diff --git a/internal/cgen/base/io-private.h b/internal/cgen/base/io-private.h
index aa2feab..5bd9d22 100644
--- a/internal/cgen/base/io-private.h
+++ b/internal/cgen/base/io-private.h
@@ -172,7 +172,7 @@
   b->meta.pos = 0;
   b->meta.closed = false;
 
-  o->private_impl.buf = b;
+  *o = b;
   *ptr_iop_r = data.ptr;
   *ptr_io1_r = data.ptr + data.len;
 
@@ -203,7 +203,7 @@
   b->meta.pos = 0;
   b->meta.closed = false;
 
-  o->private_impl.buf = b;
+  *o = b;
   *ptr_iop_w = data.ptr;
   *ptr_io1_w = data.ptr + data.len;
 
diff --git a/internal/cgen/base/io-public.h b/internal/cgen/base/io-public.h
index 4372fb3..b17d9ab 100644
--- a/internal/cgen/base/io-public.h
+++ b/internal/cgen/base/io-public.h
@@ -20,21 +20,8 @@
 
 struct wuffs_base__io_buffer__struct;
 
-typedef struct {
-  // Do not access the private_impl's fields directly. There is no API/ABI
-  // compatibility or safety guarantee if you do so.
-  struct {
-    struct wuffs_base__io_buffer__struct* buf;
-  } private_impl;
-} wuffs_base__io_reader;
-
-typedef struct {
-  // Do not access the private_impl's fields directly. There is no API/ABI
-  // compatibility or safety guarantee if you do so.
-  struct {
-    struct wuffs_base__io_buffer__struct* buf;
-  } private_impl;
-} wuffs_base__io_writer;
+typedef struct wuffs_base__io_buffer__struct* wuffs_base__io_reader;
+typedef struct wuffs_base__io_buffer__struct* wuffs_base__io_writer;
 
 // wuffs_base__io_buffer_meta is the metadata for a wuffs_base__io_buffer's
 // data.
@@ -111,16 +98,12 @@
 
 static inline wuffs_base__io_reader  //
 wuffs_base__null_io_reader() {
-  wuffs_base__io_reader ret;
-  ret.private_impl.buf = NULL;
-  return ret;
+  return NULL;
 }
 
 static inline wuffs_base__io_writer  //
 wuffs_base__null_io_writer() {
-  wuffs_base__io_writer ret;
-  ret.private_impl.buf = NULL;
-  return ret;
+  return NULL;
 }
 
 // wuffs_base__io_buffer__compact moves any written but unread bytes to the
@@ -141,16 +124,12 @@
 
 static inline wuffs_base__io_reader  //
 wuffs_base__io_buffer__reader(wuffs_base__io_buffer* buf) {
-  wuffs_base__io_reader ret;
-  ret.private_impl.buf = buf;
-  return ret;
+  return buf;
 }
 
 static inline wuffs_base__io_writer  //
 wuffs_base__io_buffer__writer(wuffs_base__io_buffer* buf) {
-  wuffs_base__io_writer ret;
-  ret.private_impl.buf = buf;
-  return ret;
+  return buf;
 }
 
 static inline uint64_t  //
diff --git a/internal/cgen/builtin.go b/internal/cgen/builtin.go
index 95c6901..c736ef6 100644
--- a/internal/cgen/builtin.go
+++ b/internal/cgen/builtin.go
@@ -141,29 +141,29 @@
 		return nil
 
 	case t.IDCountSince:
-		b.printf("(%s%s.private_impl.buf ? wuffs_base__io__count_since(", prefix, name)
+		b.printf("(%s%s ? wuffs_base__io__count_since(", prefix, name)
 		if err := g.writeExpr(b, args[0].AsArg().Value(), depth); err != nil {
 			return err
 		}
-		b.printf(", ((uint64_t)(iop_%s%s - %s%s.private_impl.buf->data.ptr))) : 0)", prefix, name, prefix, name)
+		b.printf(", ((uint64_t)(iop_%s%s - %s%s->data.ptr))) : 0)", prefix, name, prefix, name)
 		return nil
 
 	case t.IDMark:
-		b.printf("(%s%s.private_impl.buf ? ((uint64_t)(iop_%s%s - %s%s.private_impl.buf->data.ptr)) : 0)",
+		b.printf("(%s%s ? ((uint64_t)(iop_%s%s - %s%s->data.ptr)) : 0)",
 			prefix, name, prefix, name, prefix, name)
 		return nil
 
 	case t.IDPosition:
-		b.printf("(a_src.private_impl.buf ? wuffs_base__u64__sat_add(" +
-			"a_src.private_impl.buf->meta.pos, ((uint64_t)(iop_a_src - a_src.private_impl.buf->data.ptr))) : 0)")
+		b.printf("(a_src ? wuffs_base__u64__sat_add(" +
+			"a_src->meta.pos, ((uint64_t)(iop_a_src - a_src->data.ptr))) : 0)")
 		return nil
 
 	case t.IDSince:
-		b.printf("(%s%s.private_impl.buf ? wuffs_base__io__since(", prefix, name)
+		b.printf("(%s%s ? wuffs_base__io__since(", prefix, name)
 		if err := g.writeExpr(b, args[0].AsArg().Value(), depth); err != nil {
 			return err
 		}
-		b.printf(", ((uint64_t)(iop_%s%s - %s%s.private_impl.buf->data.ptr)), %s%s.private_impl.buf->data.ptr)"+
+		b.printf(", ((uint64_t)(iop_%s%s - %s%s->data.ptr)), %s%s->data.ptr)"+
 			": wuffs_base__make_slice_u8(NULL, 0))",
 			prefix, name, prefix, name, prefix, name)
 		return nil
@@ -217,7 +217,7 @@
 			suffix = "_fast"
 		}
 		b.printf("wuffs_base__io_writer__copy_n_from_history%s("+
-			"&iop_a_dst, %sdst.private_impl.buf->data.ptr, io1_a_dst",
+			"&iop_a_dst, %sdst->data.ptr, io1_a_dst",
 			suffix, aPrefix)
 		for _, o := range args {
 			b.writeb(',')
@@ -246,32 +246,31 @@
 		return g.writeArgs(b, args, depth)
 
 	case t.IDCountSince:
-		b.printf("(a_dst.private_impl.buf ? wuffs_base__io__count_since(")
+		b.printf("(a_dst ? wuffs_base__io__count_since(")
 		if err := g.writeExpr(b, args[0].AsArg().Value(), depth); err != nil {
 			return err
 		}
-		b.printf(", ((uint64_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr))) : 0)")
+		b.printf(", ((uint64_t)(iop_a_dst - a_dst->data.ptr))) : 0)")
 		return nil
 
 	case t.IDHistoryAvailable:
-		b.printf("((uint64_t)(iop_%s%s - %s%s.private_impl.buf->data.ptr))", prefix, name, prefix, name)
+		b.printf("((uint64_t)(iop_%s%s - %s%s->data.ptr))", prefix, name, prefix, name)
 		return nil
 
 	case t.IDMark:
-		b.printf("(a_dst.private_impl.buf ? ((uint64_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr)) : 0)")
+		b.printf("(a_dst ? ((uint64_t)(iop_a_dst - a_dst->data.ptr)) : 0)")
 		return nil
 
 	case t.IDPosition:
-		b.printf("(a_dst.private_impl.buf ? wuffs_base__u64__sat_add(" +
-			"a_dst.private_impl.buf->meta.pos, iop_a_dst - a_dst.private_impl.buf->data.ptr) : 0)")
+		b.printf("(a_dst ? wuffs_base__u64__sat_add(a_dst->meta.pos, iop_a_dst - a_dst->data.ptr) : 0)")
 		return nil
 
 	case t.IDSince:
-		b.printf("(a_dst.private_impl.buf ? wuffs_base__io__since(")
+		b.printf("(a_dst ? wuffs_base__io__since(")
 		if err := g.writeExpr(b, args[0].AsArg().Value(), depth); err != nil {
 			return err
 		}
-		b.printf(", ((uint64_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr)), a_dst.private_impl.buf->data.ptr)" +
+		b.printf(", ((uint64_t)(iop_a_dst - a_dst->data.ptr)), a_dst->data.ptr)" +
 			": wuffs_base__make_slice_u8(NULL, 0))")
 		return nil
 	}
diff --git a/internal/cgen/data.go b/internal/cgen/data.go
index 2efa261..9de073b 100644
--- a/internal/cgen/data.go
+++ b/internal/cgen/data.go
@@ -167,19 +167,18 @@
 	"    n = (size_t)(length);\n  }\n  // TODO: unrolling by 3 seems best for the std/deflate benchmarks, but that\n  // is mostly because 3 is the minimum length for the deflate format. This\n  // function implementation shouldn't overfit to that one format. Perhaps the\n  // copy_n_from_history Wuffs method should also take an unroll hint argument,\n  // and the cgen can look if that argument is the constant expression '3'.\n  //\n  // See also wuffs_base__io_writer__copy_n_from_history_fast below.\n  //\n  // Alternatively, or additionally, have a sloppy_copy_n_from_history method\n  // that copies 8 bytes at a time, possibly writing more than length bytes?\n  for (; n >= 3; n -= 3) {\n    *p++ = *q++;\n    *p++ = *q++;\n    *p++ = *q++;\n  }\n  for (; n; n--) {\n    *p++ = *q++;\n  }\n  *ptr_iop_w = p;\n  return length;\n}\n\n// wuffs_base__io_writer__copy_n_from_history_fast is like the\n// wuffs_base__io_writer__copy_n_from_history function above, but has stronger\n// pre-conditions. The caller needs to prove that:\n//  - distance >  " +
 	"0\n//  - distance <= (*ptr_iop_w - io0_w)\n//  - length   <= (io1_w      - *ptr_iop_w)\nstatic inline uint32_t  //\nwuffs_base__io_writer__copy_n_from_history_fast(uint8_t** ptr_iop_w,\n                                                uint8_t* io0_w,\n                                                uint8_t* io1_w,\n                                                uint32_t length,\n                                                uint32_t distance) {\n  uint8_t* p = *ptr_iop_w;\n  uint8_t* q = p - distance;\n  uint32_t n = length;\n  for (; n >= 3; n -= 3) {\n    *p++ = *q++;\n    *p++ = *q++;\n    *p++ = *q++;\n  }\n  for (; n; n--) {\n    *p++ = *q++;\n  }\n  *ptr_iop_w = p;\n  return length;\n}\n\nstatic inline uint32_t  //\nwuffs_base__io_writer__copy_n_from_reader(uint8_t** ptr_iop_w,\n                                          uint8_t* io1_w,\n                                          uint32_t length,\n                                          uint8_t** ptr_iop_r,\n                                          uint8_t* io1_r) {\n  uint8_t* i" +
 	"op_w = *ptr_iop_w;\n  size_t n = length;\n  if (n > ((size_t)(io1_w - iop_w))) {\n    n = (size_t)(io1_w - iop_w);\n  }\n  uint8_t* iop_r = *ptr_iop_r;\n  if (n > ((size_t)(io1_r - iop_r))) {\n    n = (size_t)(io1_r - iop_r);\n  }\n  if (n > 0) {\n    memmove(iop_w, iop_r, n);\n    *ptr_iop_w += n;\n    *ptr_iop_r += n;\n  }\n  return (uint32_t)(n);\n}\n\nstatic inline uint64_t  //\nwuffs_base__io_writer__copy_from_slice(uint8_t** ptr_iop_w,\n                                       uint8_t* io1_w,\n                                       wuffs_base__slice_u8 src) {\n  uint8_t* iop_w = *ptr_iop_w;\n  size_t n = src.len;\n  if (n > ((size_t)(io1_w - iop_w))) {\n    n = (size_t)(io1_w - iop_w);\n  }\n  if (n > 0) {\n    memmove(iop_w, src.ptr, n);\n    *ptr_iop_w += n;\n  }\n  return (uint64_t)(n);\n}\n\nstatic inline uint32_t  //\nwuffs_base__io_writer__copy_n_from_slice(uint8_t** ptr_iop_w,\n                                         uint8_t* io1_w,\n                                         uint32_t length,\n                                         w" +
-	"uffs_base__slice_u8 src) {\n  uint8_t* iop_w = *ptr_iop_w;\n  size_t n = src.len;\n  if (n > length) {\n    n = length;\n  }\n  if (n > ((size_t)(io1_w - iop_w))) {\n    n = (size_t)(io1_w - iop_w);\n  }\n  if (n > 0) {\n    memmove(iop_w, src.ptr, n);\n    *ptr_iop_w += n;\n  }\n  return (uint32_t)(n);\n}\n\nstatic inline wuffs_base__empty_struct  //\nwuffs_base__io_reader__set(wuffs_base__io_reader* o,\n                           wuffs_base__io_buffer* b,\n                           uint8_t** ptr_iop_r,\n                           uint8_t** ptr_io1_r,\n                           wuffs_base__slice_u8 data) {\n  b->data = data;\n  b->meta.wi = data.len;\n  b->meta.ri = 0;\n  b->meta.pos = 0;\n  b->meta.closed = false;\n\n  o->private_impl.buf = b;\n  *ptr_iop_r = data.ptr;\n  *ptr_io1_r = data.ptr + data.len;\n\n  wuffs_base__empty_struct ret;\n  ret.private_impl = 0;\n  return ret;\n}\n\nstatic inline wuffs_base__slice_u8  //\nwuffs_base__io_reader__take(uint8_t** ptr_iop_r, uint8_t* io1_r, uint64_t n) {\n  if (n <= ((size_t)(io1_r - *ptr_iop_r))" +
-	") {\n    uint8_t* p = *ptr_iop_r;\n    *ptr_iop_r += n;\n    return wuffs_base__make_slice_u8(p, n);\n  }\n  return wuffs_base__make_slice_u8(NULL, 0);\n}\n\nstatic inline wuffs_base__empty_struct  //\nwuffs_base__io_writer__set(wuffs_base__io_writer* o,\n                           wuffs_base__io_buffer* b,\n                           uint8_t** ptr_iop_w,\n                           uint8_t** ptr_io1_w,\n                           wuffs_base__slice_u8 data) {\n  b->data = data;\n  b->meta.wi = 0;\n  b->meta.ri = 0;\n  b->meta.pos = 0;\n  b->meta.closed = false;\n\n  o->private_impl.buf = b;\n  *ptr_iop_w = data.ptr;\n  *ptr_io1_w = data.ptr + data.len;\n\n  wuffs_base__empty_struct ret;\n  ret.private_impl = 0;\n  return ret;\n}\n\n" +
+	"uffs_base__slice_u8 src) {\n  uint8_t* iop_w = *ptr_iop_w;\n  size_t n = src.len;\n  if (n > length) {\n    n = length;\n  }\n  if (n > ((size_t)(io1_w - iop_w))) {\n    n = (size_t)(io1_w - iop_w);\n  }\n  if (n > 0) {\n    memmove(iop_w, src.ptr, n);\n    *ptr_iop_w += n;\n  }\n  return (uint32_t)(n);\n}\n\nstatic inline wuffs_base__empty_struct  //\nwuffs_base__io_reader__set(wuffs_base__io_reader* o,\n                           wuffs_base__io_buffer* b,\n                           uint8_t** ptr_iop_r,\n                           uint8_t** ptr_io1_r,\n                           wuffs_base__slice_u8 data) {\n  b->data = data;\n  b->meta.wi = data.len;\n  b->meta.ri = 0;\n  b->meta.pos = 0;\n  b->meta.closed = false;\n\n  *o = b;\n  *ptr_iop_r = data.ptr;\n  *ptr_io1_r = data.ptr + data.len;\n\n  wuffs_base__empty_struct ret;\n  ret.private_impl = 0;\n  return ret;\n}\n\nstatic inline wuffs_base__slice_u8  //\nwuffs_base__io_reader__take(uint8_t** ptr_iop_r, uint8_t* io1_r, uint64_t n) {\n  if (n <= ((size_t)(io1_r - *ptr_iop_r))) {\n    uint8_t* " +
+	"p = *ptr_iop_r;\n    *ptr_iop_r += n;\n    return wuffs_base__make_slice_u8(p, n);\n  }\n  return wuffs_base__make_slice_u8(NULL, 0);\n}\n\nstatic inline wuffs_base__empty_struct  //\nwuffs_base__io_writer__set(wuffs_base__io_writer* o,\n                           wuffs_base__io_buffer* b,\n                           uint8_t** ptr_iop_w,\n                           uint8_t** ptr_io1_w,\n                           wuffs_base__slice_u8 data) {\n  b->data = data;\n  b->meta.wi = 0;\n  b->meta.ri = 0;\n  b->meta.pos = 0;\n  b->meta.closed = false;\n\n  *o = b;\n  *ptr_iop_w = data.ptr;\n  *ptr_io1_w = data.ptr + data.len;\n\n  wuffs_base__empty_struct ret;\n  ret.private_impl = 0;\n  return ret;\n}\n\n" +
 	"" +
 	"// ---------------- I/O (Utility)\n\n#define wuffs_base__utility__null_io_reader wuffs_base__null_io_reader\n#define wuffs_base__utility__null_io_writer wuffs_base__null_io_writer\n" +
 	""
 
 const baseIOPublicH = "" +
-	"// ---------------- I/O\n//\n// See (/doc/note/io-input-output.md).\n\nstruct wuffs_base__io_buffer__struct;\n\ntypedef struct {\n  // Do not access the private_impl's fields directly. There is no API/ABI\n  // compatibility or safety guarantee if you do so.\n  struct {\n    struct wuffs_base__io_buffer__struct* buf;\n  } private_impl;\n} wuffs_base__io_reader;\n\ntypedef struct {\n  // Do not access the private_impl's fields directly. There is no API/ABI\n  // compatibility or safety guarantee if you do so.\n  struct {\n    struct wuffs_base__io_buffer__struct* buf;\n  } private_impl;\n} wuffs_base__io_writer;\n\n// wuffs_base__io_buffer_meta is the metadata for a wuffs_base__io_buffer's\n// data.\ntypedef struct {\n  size_t wi;     // Write index. Invariant: wi <= len.\n  size_t ri;     // Read  index. Invariant: ri <= wi.\n  uint64_t pos;  // Position of the buffer start relative to the stream start.\n  bool closed;   // No further writes are expected.\n} wuffs_base__io_buffer_meta;\n\n// wuffs_base__io_buffer is a 1-dimensional buffer " +
-	"(a pointer and length) plus\n// additional metadata.\n//\n// A value with all fields zero is a valid, empty buffer.\ntypedef struct wuffs_base__io_buffer__struct {\n  wuffs_base__slice_u8 data;\n  wuffs_base__io_buffer_meta meta;\n\n#ifdef __cplusplus\n  inline void compact();\n  inline wuffs_base__io_reader reader();\n  inline wuffs_base__io_writer writer();\n  inline uint64_t reader_available() const;\n  inline uint64_t reader_io_position() const;\n  inline uint64_t writer_available() const;\n  inline uint64_t writer_io_position() const;\n#endif  // __cplusplus\n\n} wuffs_base__io_buffer;\n\nstatic inline wuffs_base__io_buffer  //\nwuffs_base__make_io_buffer(wuffs_base__slice_u8 data,\n                           wuffs_base__io_buffer_meta meta) {\n  wuffs_base__io_buffer ret;\n  ret.data = data;\n  ret.meta = meta;\n  return ret;\n}\n\nstatic inline wuffs_base__io_buffer_meta  //\nwuffs_base__make_io_buffer_meta(size_t wi,\n                                size_t ri,\n                                uint64_t pos,\n                          " +
-	"      bool closed) {\n  wuffs_base__io_buffer_meta ret;\n  ret.wi = wi;\n  ret.ri = ri;\n  ret.pos = pos;\n  ret.closed = closed;\n  return ret;\n}\n\nstatic inline wuffs_base__io_buffer  //\nwuffs_base__null_io_buffer() {\n  wuffs_base__io_buffer ret;\n  ret.data.ptr = NULL;\n  ret.data.len = 0;\n  ret.meta.wi = 0;\n  ret.meta.ri = 0;\n  ret.meta.pos = 0;\n  ret.meta.closed = false;\n  return ret;\n}\n\nstatic inline wuffs_base__io_buffer_meta  //\nwuffs_base__null_io_buffer_meta() {\n  wuffs_base__io_buffer_meta ret;\n  ret.wi = 0;\n  ret.ri = 0;\n  ret.pos = 0;\n  ret.closed = false;\n  return ret;\n}\n\nstatic inline wuffs_base__io_reader  //\nwuffs_base__null_io_reader() {\n  wuffs_base__io_reader ret;\n  ret.private_impl.buf = NULL;\n  return ret;\n}\n\nstatic inline wuffs_base__io_writer  //\nwuffs_base__null_io_writer() {\n  wuffs_base__io_writer ret;\n  ret.private_impl.buf = NULL;\n  return ret;\n}\n\n// wuffs_base__io_buffer__compact moves any written but unread bytes to the\n// start of the buffer.\nstatic inline void  //\nwuffs_base__io_buffer" +
-	"__compact(wuffs_base__io_buffer* buf) {\n  if (!buf || (buf->meta.ri == 0)) {\n    return;\n  }\n  buf->meta.pos = wuffs_base__u64__sat_add(buf->meta.pos, buf->meta.ri);\n  size_t n = buf->meta.wi - buf->meta.ri;\n  if (n != 0) {\n    memmove(buf->data.ptr, buf->data.ptr + buf->meta.ri, n);\n  }\n  buf->meta.wi = n;\n  buf->meta.ri = 0;\n}\n\nstatic inline wuffs_base__io_reader  //\nwuffs_base__io_buffer__reader(wuffs_base__io_buffer* buf) {\n  wuffs_base__io_reader ret;\n  ret.private_impl.buf = buf;\n  return ret;\n}\n\nstatic inline wuffs_base__io_writer  //\nwuffs_base__io_buffer__writer(wuffs_base__io_buffer* buf) {\n  wuffs_base__io_writer ret;\n  ret.private_impl.buf = buf;\n  return ret;\n}\n\nstatic inline uint64_t  //\nwuffs_base__io_buffer__reader_available(const wuffs_base__io_buffer* buf) {\n  return buf ? buf->meta.wi - buf->meta.ri : 0;\n}\n\nstatic inline uint64_t  //\nwuffs_base__io_buffer__reader_io_position(const wuffs_base__io_buffer* buf) {\n  return buf ? wuffs_base__u64__sat_add(buf->meta.pos, buf->meta.ri) : 0;\n}\n\nstat" +
-	"ic inline uint64_t  //\nwuffs_base__io_buffer__writer_available(const wuffs_base__io_buffer* buf) {\n  return buf ? buf->data.len - buf->meta.wi : 0;\n}\n\nstatic inline uint64_t  //\nwuffs_base__io_buffer__writer_io_position(const wuffs_base__io_buffer* buf) {\n  return buf ? wuffs_base__u64__sat_add(buf->meta.pos, buf->meta.wi) : 0;\n}\n\n#ifdef __cplusplus\n\ninline void  //\nwuffs_base__io_buffer__struct::compact() {\n  wuffs_base__io_buffer__compact(this);\n}\n\ninline wuffs_base__io_reader  //\nwuffs_base__io_buffer__struct::reader() {\n  return wuffs_base__io_buffer__reader(this);\n}\n\ninline wuffs_base__io_writer  //\nwuffs_base__io_buffer__struct::writer() {\n  return wuffs_base__io_buffer__writer(this);\n}\n\ninline uint64_t  //\nwuffs_base__io_buffer__struct::reader_available() const {\n  return wuffs_base__io_buffer__reader_available(this);\n}\n\ninline uint64_t  //\nwuffs_base__io_buffer__struct::reader_io_position() const {\n  return wuffs_base__io_buffer__reader_io_position(this);\n}\n\ninline uint64_t  //\nwuffs_base__io_buffer__" +
-	"struct::writer_available() const {\n  return wuffs_base__io_buffer__writer_available(this);\n}\n\ninline uint64_t  //\nwuffs_base__io_buffer__struct::writer_io_position() const {\n  return wuffs_base__io_buffer__writer_io_position(this);\n}\n\n#endif  // __cplusplus\n" +
+	"// ---------------- I/O\n//\n// See (/doc/note/io-input-output.md).\n\nstruct wuffs_base__io_buffer__struct;\n\ntypedef struct wuffs_base__io_buffer__struct* wuffs_base__io_reader;\ntypedef struct wuffs_base__io_buffer__struct* wuffs_base__io_writer;\n\n// wuffs_base__io_buffer_meta is the metadata for a wuffs_base__io_buffer's\n// data.\ntypedef struct {\n  size_t wi;     // Write index. Invariant: wi <= len.\n  size_t ri;     // Read  index. Invariant: ri <= wi.\n  uint64_t pos;  // Position of the buffer start relative to the stream start.\n  bool closed;   // No further writes are expected.\n} wuffs_base__io_buffer_meta;\n\n// wuffs_base__io_buffer is a 1-dimensional buffer (a pointer and length) plus\n// additional metadata.\n//\n// A value with all fields zero is a valid, empty buffer.\ntypedef struct wuffs_base__io_buffer__struct {\n  wuffs_base__slice_u8 data;\n  wuffs_base__io_buffer_meta meta;\n\n#ifdef __cplusplus\n  inline void compact();\n  inline wuffs_base__io_reader reader();\n  inline wuffs_base__io_writer writer();\n  in" +
+	"line uint64_t reader_available() const;\n  inline uint64_t reader_io_position() const;\n  inline uint64_t writer_available() const;\n  inline uint64_t writer_io_position() const;\n#endif  // __cplusplus\n\n} wuffs_base__io_buffer;\n\nstatic inline wuffs_base__io_buffer  //\nwuffs_base__make_io_buffer(wuffs_base__slice_u8 data,\n                           wuffs_base__io_buffer_meta meta) {\n  wuffs_base__io_buffer ret;\n  ret.data = data;\n  ret.meta = meta;\n  return ret;\n}\n\nstatic inline wuffs_base__io_buffer_meta  //\nwuffs_base__make_io_buffer_meta(size_t wi,\n                                size_t ri,\n                                uint64_t pos,\n                                bool closed) {\n  wuffs_base__io_buffer_meta ret;\n  ret.wi = wi;\n  ret.ri = ri;\n  ret.pos = pos;\n  ret.closed = closed;\n  return ret;\n}\n\nstatic inline wuffs_base__io_buffer  //\nwuffs_base__null_io_buffer() {\n  wuffs_base__io_buffer ret;\n  ret.data.ptr = NULL;\n  ret.data.len = 0;\n  ret.meta.wi = 0;\n  ret.meta.ri = 0;\n  ret.meta.pos = 0;\n  ret.meta.c" +
+	"losed = false;\n  return ret;\n}\n\nstatic inline wuffs_base__io_buffer_meta  //\nwuffs_base__null_io_buffer_meta() {\n  wuffs_base__io_buffer_meta ret;\n  ret.wi = 0;\n  ret.ri = 0;\n  ret.pos = 0;\n  ret.closed = false;\n  return ret;\n}\n\nstatic inline wuffs_base__io_reader  //\nwuffs_base__null_io_reader() {\n  return NULL;\n}\n\nstatic inline wuffs_base__io_writer  //\nwuffs_base__null_io_writer() {\n  return NULL;\n}\n\n// wuffs_base__io_buffer__compact moves any written but unread bytes to the\n// start of the buffer.\nstatic inline void  //\nwuffs_base__io_buffer__compact(wuffs_base__io_buffer* buf) {\n  if (!buf || (buf->meta.ri == 0)) {\n    return;\n  }\n  buf->meta.pos = wuffs_base__u64__sat_add(buf->meta.pos, buf->meta.ri);\n  size_t n = buf->meta.wi - buf->meta.ri;\n  if (n != 0) {\n    memmove(buf->data.ptr, buf->data.ptr + buf->meta.ri, n);\n  }\n  buf->meta.wi = n;\n  buf->meta.ri = 0;\n}\n\nstatic inline wuffs_base__io_reader  //\nwuffs_base__io_buffer__reader(wuffs_base__io_buffer* buf) {\n  return buf;\n}\n\nstatic inline wuffs_base" +
+	"__io_writer  //\nwuffs_base__io_buffer__writer(wuffs_base__io_buffer* buf) {\n  return buf;\n}\n\nstatic inline uint64_t  //\nwuffs_base__io_buffer__reader_available(const wuffs_base__io_buffer* buf) {\n  return buf ? buf->meta.wi - buf->meta.ri : 0;\n}\n\nstatic inline uint64_t  //\nwuffs_base__io_buffer__reader_io_position(const wuffs_base__io_buffer* buf) {\n  return buf ? wuffs_base__u64__sat_add(buf->meta.pos, buf->meta.ri) : 0;\n}\n\nstatic inline uint64_t  //\nwuffs_base__io_buffer__writer_available(const wuffs_base__io_buffer* buf) {\n  return buf ? buf->data.len - buf->meta.wi : 0;\n}\n\nstatic inline uint64_t  //\nwuffs_base__io_buffer__writer_io_position(const wuffs_base__io_buffer* buf) {\n  return buf ? wuffs_base__u64__sat_add(buf->meta.pos, buf->meta.wi) : 0;\n}\n\n#ifdef __cplusplus\n\ninline void  //\nwuffs_base__io_buffer__struct::compact() {\n  wuffs_base__io_buffer__compact(this);\n}\n\ninline wuffs_base__io_reader  //\nwuffs_base__io_buffer__struct::reader() {\n  return wuffs_base__io_buffer__reader(this);\n}\n\ninline wuffs" +
+	"_base__io_writer  //\nwuffs_base__io_buffer__struct::writer() {\n  return wuffs_base__io_buffer__writer(this);\n}\n\ninline uint64_t  //\nwuffs_base__io_buffer__struct::reader_available() const {\n  return wuffs_base__io_buffer__reader_available(this);\n}\n\ninline uint64_t  //\nwuffs_base__io_buffer__struct::reader_io_position() const {\n  return wuffs_base__io_buffer__reader_io_position(this);\n}\n\ninline uint64_t  //\nwuffs_base__io_buffer__struct::writer_available() const {\n  return wuffs_base__io_buffer__writer_available(this);\n}\n\ninline uint64_t  //\nwuffs_base__io_buffer__struct::writer_io_position() const {\n  return wuffs_base__io_buffer__writer_io_position(this);\n}\n\n#endif  // __cplusplus\n" +
 	""
 
 const baseRangePrivateH = "" +
diff --git a/internal/cgen/var.go b/internal/cgen/var.go
index ba1308b..7205c22 100644
--- a/internal/cgen/var.go
+++ b/internal/cgen/var.go
@@ -106,18 +106,18 @@
 		b.printf("uint8_t* %s%s WUFFS_BASE__POTENTIALLY_UNUSED = NULL;", io1Prefix, preName)
 	}
 
-	b.printf("if (%s.private_impl.buf) {", preName)
+	b.printf("if (%s) {", preName)
 
-	b.printf("%s%s = %s.private_impl.buf->data.ptr + %s.private_impl.buf->%s;",
+	b.printf("%s%s = %s->data.ptr + %s->%s;",
 		iopPrefix, preName, preName, preName, i0)
 
 	if header {
 		b.printf("%s%s = %s%s;", io0Prefix, preName, iopPrefix, preName)
-		b.printf("%s%s = %s.private_impl.buf->data.ptr + %s.private_impl.buf->%s;",
+		b.printf("%s%s = %s->data.ptr + %s->%s;",
 			io1Prefix, preName, preName, preName, i1)
 
 		if typ.QID()[1] == t.IDIOWriter {
-			b.printf("if (%s.private_impl.buf->meta.closed) {", preName)
+			b.printf("if (%s->meta.closed) {", preName)
 			b.printf("%s%s = %s%s;", io1Prefix, preName, iopPrefix, preName)
 			b.printf("}\n")
 		}
@@ -158,10 +158,8 @@
 		i0 = "wi"
 	}
 
-	b.printf("if (%s.private_impl.buf) {", preName)
-	b.printf("%s.private_impl.buf->meta.%s = ((size_t)(%s%s - %s.private_impl.buf->data.ptr));",
-		preName, i0, iopPrefix, preName, preName)
-	b.printf("}\n")
+	b.printf("if (%s) { %s->meta.%s = ((size_t)(%s%s - %s->data.ptr)); }\n",
+		preName, preName, i0, iopPrefix, preName, preName)
 	return nil
 }
 
diff --git a/release/c/wuffs-unsupported-snapshot.c b/release/c/wuffs-unsupported-snapshot.c
index 10e87ca..79bab2f 100644
--- a/release/c/wuffs-unsupported-snapshot.c
+++ b/release/c/wuffs-unsupported-snapshot.c
@@ -1278,21 +1278,8 @@
 
 struct wuffs_base__io_buffer__struct;
 
-typedef struct {
-  // Do not access the private_impl's fields directly. There is no API/ABI
-  // compatibility or safety guarantee if you do so.
-  struct {
-    struct wuffs_base__io_buffer__struct* buf;
-  } private_impl;
-} wuffs_base__io_reader;
-
-typedef struct {
-  // Do not access the private_impl's fields directly. There is no API/ABI
-  // compatibility or safety guarantee if you do so.
-  struct {
-    struct wuffs_base__io_buffer__struct* buf;
-  } private_impl;
-} wuffs_base__io_writer;
+typedef struct wuffs_base__io_buffer__struct* wuffs_base__io_reader;
+typedef struct wuffs_base__io_buffer__struct* wuffs_base__io_writer;
 
 // wuffs_base__io_buffer_meta is the metadata for a wuffs_base__io_buffer's
 // data.
@@ -1369,16 +1356,12 @@
 
 static inline wuffs_base__io_reader  //
 wuffs_base__null_io_reader() {
-  wuffs_base__io_reader ret;
-  ret.private_impl.buf = NULL;
-  return ret;
+  return NULL;
 }
 
 static inline wuffs_base__io_writer  //
 wuffs_base__null_io_writer() {
-  wuffs_base__io_writer ret;
-  ret.private_impl.buf = NULL;
-  return ret;
+  return NULL;
 }
 
 // wuffs_base__io_buffer__compact moves any written but unread bytes to the
@@ -1399,16 +1382,12 @@
 
 static inline wuffs_base__io_reader  //
 wuffs_base__io_buffer__reader(wuffs_base__io_buffer* buf) {
-  wuffs_base__io_reader ret;
-  ret.private_impl.buf = buf;
-  return ret;
+  return buf;
 }
 
 static inline wuffs_base__io_writer  //
 wuffs_base__io_buffer__writer(wuffs_base__io_buffer* buf) {
-  wuffs_base__io_writer ret;
-  ret.private_impl.buf = buf;
-  return ret;
+  return buf;
 }
 
 static inline uint64_t  //
@@ -4658,7 +4637,7 @@
   b->meta.pos = 0;
   b->meta.closed = false;
 
-  o->private_impl.buf = b;
+  *o = b;
   *ptr_iop_r = data.ptr;
   *ptr_io1_r = data.ptr + data.len;
 
@@ -4689,7 +4668,7 @@
   b->meta.pos = 0;
   b->meta.closed = false;
 
-  o->private_impl.buf = b;
+  *o = b;
   *ptr_iop_w = data.ptr;
   *ptr_io1_w = data.ptr + data.len;
 
@@ -6434,13 +6413,11 @@
   uint8_t* iop_a_dst = NULL;
   uint8_t* io0_a_dst WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_dst WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_dst.private_impl.buf) {
-    iop_a_dst =
-        a_dst.private_impl.buf->data.ptr + a_dst.private_impl.buf->meta.wi;
+  if (a_dst) {
+    iop_a_dst = a_dst->data.ptr + a_dst->meta.wi;
     io0_a_dst = iop_a_dst;
-    io1_a_dst =
-        a_dst.private_impl.buf->data.ptr + a_dst.private_impl.buf->data.len;
-    if (a_dst.private_impl.buf->meta.closed) {
+    io1_a_dst = a_dst->data.ptr + a_dst->data.len;
+    if (a_dst->meta.closed) {
       io1_a_dst = iop_a_dst;
     }
   }
@@ -6452,19 +6429,15 @@
     WUFFS_BASE__COROUTINE_SUSPENSION_POINT_0;
 
     while (true) {
-      v_mark = (a_dst.private_impl.buf
-                    ? ((uint64_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr))
-                    : 0);
+      v_mark = (a_dst ? ((uint64_t)(iop_a_dst - a_dst->data.ptr)) : 0);
       {
-        if (a_dst.private_impl.buf) {
-          a_dst.private_impl.buf->meta.wi =
-              ((size_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr));
+        if (a_dst) {
+          a_dst->meta.wi = ((size_t)(iop_a_dst - a_dst->data.ptr));
         }
         wuffs_base__status t_0 =
             wuffs_deflate__decoder__decode_blocks(self, a_dst, a_src);
-        if (a_dst.private_impl.buf) {
-          iop_a_dst = a_dst.private_impl.buf->data.ptr +
-                      a_dst.private_impl.buf->meta.wi;
+        if (a_dst) {
+          iop_a_dst = a_dst->data.ptr + a_dst->meta.wi;
         }
         v_status = t_0;
       }
@@ -6479,12 +6452,10 @@
         goto ok;
       }
       v_written =
-          (a_dst.private_impl.buf
-               ? wuffs_base__io__since(
-                     v_mark,
-                     ((uint64_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr)),
-                     a_dst.private_impl.buf->data.ptr)
-               : wuffs_base__make_slice_u8(NULL, 0));
+          (a_dst ? wuffs_base__io__since(
+                       v_mark, ((uint64_t)(iop_a_dst - a_dst->data.ptr)),
+                       a_dst->data.ptr)
+                 : wuffs_base__make_slice_u8(NULL, 0));
       if (((uint64_t)(v_written.len)) >= 32768) {
         v_written = wuffs_base__slice_u8__suffix(v_written, 32768);
         wuffs_base__slice_u8__copy_from_slice(
@@ -6533,9 +6504,8 @@
 
   goto exit;
 exit:
-  if (a_dst.private_impl.buf) {
-    a_dst.private_impl.buf->meta.wi =
-        ((size_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr));
+  if (a_dst) {
+    a_dst->meta.wi = ((size_t)(iop_a_dst - a_dst->data.ptr));
   }
 
   if (wuffs_base__status__is_error(status)) {
@@ -6560,12 +6530,10 @@
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   uint32_t coro_susp_point = self->private_impl.p_decode_blocks[0];
@@ -6595,16 +6563,14 @@
       self->private_impl.f_bits >>= 3;
       self->private_impl.f_n_bits -= 3;
       if (v_type == 0) {
-        if (a_src.private_impl.buf) {
-          a_src.private_impl.buf->meta.ri =
-              ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+        if (a_src) {
+          a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
         }
         WUFFS_BASE__COROUTINE_SUSPENSION_POINT(2);
         status =
             wuffs_deflate__decoder__decode_uncompressed(self, a_dst, a_src);
-        if (a_src.private_impl.buf) {
-          iop_a_src = a_src.private_impl.buf->data.ptr +
-                      a_src.private_impl.buf->meta.ri;
+        if (a_src) {
+          iop_a_src = a_src->data.ptr + a_src->meta.ri;
         }
         if (status) {
           goto suspend;
@@ -6623,15 +6589,13 @@
           goto ok;
         }
       } else if (v_type == 2) {
-        if (a_src.private_impl.buf) {
-          a_src.private_impl.buf->meta.ri =
-              ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+        if (a_src) {
+          a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
         }
         WUFFS_BASE__COROUTINE_SUSPENSION_POINT(3);
         status = wuffs_deflate__decoder__init_dynamic_huffman(self, a_src);
-        if (a_src.private_impl.buf) {
-          iop_a_src = a_src.private_impl.buf->data.ptr +
-                      a_src.private_impl.buf->meta.ri;
+        if (a_src) {
+          iop_a_src = a_src->data.ptr + a_src->meta.ri;
         }
         if (status) {
           goto suspend;
@@ -6642,15 +6606,13 @@
       }
       self->private_impl.f_end_of_block = false;
       while (true) {
-        if (a_src.private_impl.buf) {
-          a_src.private_impl.buf->meta.ri =
-              ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+        if (a_src) {
+          a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
         }
         v_status =
             wuffs_deflate__decoder__decode_huffman_fast(self, a_dst, a_src);
-        if (a_src.private_impl.buf) {
-          iop_a_src = a_src.private_impl.buf->data.ptr +
-                      a_src.private_impl.buf->meta.ri;
+        if (a_src) {
+          iop_a_src = a_src->data.ptr + a_src->meta.ri;
         }
         if (wuffs_base__status__is_error(v_status)) {
           status = v_status;
@@ -6659,16 +6621,14 @@
         if (self->private_impl.f_end_of_block) {
           goto label_0_continue;
         }
-        if (a_src.private_impl.buf) {
-          a_src.private_impl.buf->meta.ri =
-              ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+        if (a_src) {
+          a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
         }
         WUFFS_BASE__COROUTINE_SUSPENSION_POINT(4);
         status =
             wuffs_deflate__decoder__decode_huffman_slow(self, a_dst, a_src);
-        if (a_src.private_impl.buf) {
-          iop_a_src = a_src.private_impl.buf->data.ptr +
-                      a_src.private_impl.buf->meta.ri;
+        if (a_src) {
+          iop_a_src = a_src->data.ptr + a_src->meta.ri;
         }
         if (status) {
           goto suspend;
@@ -6693,9 +6653,8 @@
 
   goto exit;
 exit:
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   return status;
@@ -6715,25 +6674,21 @@
   uint8_t* iop_a_dst = NULL;
   uint8_t* io0_a_dst WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_dst WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_dst.private_impl.buf) {
-    iop_a_dst =
-        a_dst.private_impl.buf->data.ptr + a_dst.private_impl.buf->meta.wi;
+  if (a_dst) {
+    iop_a_dst = a_dst->data.ptr + a_dst->meta.wi;
     io0_a_dst = iop_a_dst;
-    io1_a_dst =
-        a_dst.private_impl.buf->data.ptr + a_dst.private_impl.buf->data.len;
-    if (a_dst.private_impl.buf->meta.closed) {
+    io1_a_dst = a_dst->data.ptr + a_dst->data.len;
+    if (a_dst->meta.closed) {
       io1_a_dst = iop_a_dst;
     }
   }
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   uint32_t coro_susp_point = self->private_impl.p_decode_uncompressed[0];
@@ -6817,13 +6772,11 @@
 
   goto exit;
 exit:
-  if (a_dst.private_impl.buf) {
-    a_dst.private_impl.buf->meta.wi =
-        ((size_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr));
+  if (a_dst) {
+    a_dst->meta.wi = ((size_t)(iop_a_dst - a_dst->data.ptr));
   }
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   return status;
@@ -6895,12 +6848,10 @@
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   uint32_t coro_susp_point = self->private_impl.p_init_dynamic_huffman[0];
@@ -7113,9 +7064,8 @@
 
   goto exit;
 exit:
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   return status;
@@ -7401,25 +7351,21 @@
   uint8_t* iop_a_dst = NULL;
   uint8_t* io0_a_dst WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_dst WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_dst.private_impl.buf) {
-    iop_a_dst =
-        a_dst.private_impl.buf->data.ptr + a_dst.private_impl.buf->meta.wi;
+  if (a_dst) {
+    iop_a_dst = a_dst->data.ptr + a_dst->meta.wi;
     io0_a_dst = iop_a_dst;
-    io1_a_dst =
-        a_dst.private_impl.buf->data.ptr + a_dst.private_impl.buf->data.len;
-    if (a_dst.private_impl.buf->meta.closed) {
+    io1_a_dst = a_dst->data.ptr + a_dst->data.len;
+    if (a_dst->meta.closed) {
       io1_a_dst = iop_a_dst;
     }
   }
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   if ((self->private_impl.f_n_bits >= 8) ||
@@ -7585,11 +7531,10 @@
     v_n_copied = 0;
     while (true) {
       if (((uint64_t)((v_dist_minus_1 + 1))) >
-          ((uint64_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr))) {
+          ((uint64_t)(iop_a_dst - a_dst->data.ptr))) {
         v_hlen = 0;
-        v_hdist = ((uint32_t)(
-            (((uint64_t)((v_dist_minus_1 + 1))) -
-             ((uint64_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr)))));
+        v_hdist = ((uint32_t)((((uint64_t)((v_dist_minus_1 + 1))) -
+                               ((uint64_t)(iop_a_dst - a_dst->data.ptr)))));
         if (v_length > v_hdist) {
           v_length -= v_hdist;
           v_hlen = v_hdist;
@@ -7623,13 +7568,13 @@
           goto label_0_continue;
         }
         if (((uint64_t)((v_dist_minus_1 + 1))) >
-            ((uint64_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr))) {
+            ((uint64_t)(iop_a_dst - a_dst->data.ptr))) {
           status = wuffs_deflate__error__internal_error_inconsistent_distance;
           goto exit;
         }
       }
       wuffs_base__io_writer__copy_n_from_history_fast(
-          &iop_a_dst, a_dst.private_impl.buf->data.ptr, io1_a_dst, v_length,
+          &iop_a_dst, a_dst->data.ptr, io1_a_dst, v_length,
           (v_dist_minus_1 + 1));
       goto label_2_break;
     }
@@ -7654,13 +7599,11 @@
   }
   goto exit;
 exit:
-  if (a_dst.private_impl.buf) {
-    a_dst.private_impl.buf->meta.wi =
-        ((size_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr));
+  if (a_dst) {
+    a_dst->meta.wi = ((size_t)(iop_a_dst - a_dst->data.ptr));
   }
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   return status;
@@ -7697,25 +7640,21 @@
   uint8_t* iop_a_dst = NULL;
   uint8_t* io0_a_dst WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_dst WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_dst.private_impl.buf) {
-    iop_a_dst =
-        a_dst.private_impl.buf->data.ptr + a_dst.private_impl.buf->meta.wi;
+  if (a_dst) {
+    iop_a_dst = a_dst->data.ptr + a_dst->meta.wi;
     io0_a_dst = iop_a_dst;
-    io1_a_dst =
-        a_dst.private_impl.buf->data.ptr + a_dst.private_impl.buf->data.len;
-    if (a_dst.private_impl.buf->meta.closed) {
+    io1_a_dst = a_dst->data.ptr + a_dst->data.len;
+    if (a_dst->meta.closed) {
       io1_a_dst = iop_a_dst;
     }
   }
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   uint32_t coro_susp_point = self->private_impl.p_decode_huffman_slow[0];
@@ -7946,10 +7885,9 @@
       }
       while (true) {
         if (((uint64_t)((v_dist_minus_1 + 1))) >
-            ((uint64_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr))) {
-          v_hdist = ((uint32_t)(
-              (((uint64_t)((v_dist_minus_1 + 1))) -
-               ((uint64_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr)))));
+            ((uint64_t)(iop_a_dst - a_dst->data.ptr))) {
+          v_hdist = ((uint32_t)((((uint64_t)((v_dist_minus_1 + 1))) -
+                                 ((uint64_t)(iop_a_dst - a_dst->data.ptr)))));
           if (v_length > v_hdist) {
             v_length -= v_hdist;
             v_hlen = v_hdist;
@@ -8008,7 +7946,7 @@
           }
         }
         v_n_copied = wuffs_base__io_writer__copy_n_from_history(
-            &iop_a_dst, a_dst.private_impl.buf->data.ptr, io1_a_dst, v_length,
+            &iop_a_dst, a_dst->data.ptr, io1_a_dst, v_length,
             (v_dist_minus_1 + 1));
         if (v_length <= v_n_copied) {
           v_length = 0;
@@ -8056,13 +7994,11 @@
 
   goto exit;
 exit:
-  if (a_dst.private_impl.buf) {
-    a_dst.private_impl.buf->meta.wi =
-        ((size_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr));
+  if (a_dst) {
+    a_dst->meta.wi = ((size_t)(iop_a_dst - a_dst->data.ptr));
   }
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   return status;
@@ -8305,12 +8241,10 @@
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   v_clear_code = self->private_impl.f_clear_code;
@@ -8465,9 +8399,8 @@
   self->private_impl.f_bits = v_bits;
   self->private_impl.f_n_bits = v_n_bits;
   self->private_impl.f_output_wi = v_output_wi;
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   return wuffs_base__make_empty_struct();
@@ -8486,13 +8419,11 @@
   uint8_t* iop_a_dst = NULL;
   uint8_t* io0_a_dst WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_dst WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_dst.private_impl.buf) {
-    iop_a_dst =
-        a_dst.private_impl.buf->data.ptr + a_dst.private_impl.buf->meta.wi;
+  if (a_dst) {
+    iop_a_dst = a_dst->data.ptr + a_dst->meta.wi;
     io0_a_dst = iop_a_dst;
-    io1_a_dst =
-        a_dst.private_impl.buf->data.ptr + a_dst.private_impl.buf->data.len;
-    if (a_dst.private_impl.buf->meta.closed) {
+    io1_a_dst = a_dst->data.ptr + a_dst->data.len;
+    if (a_dst->meta.closed) {
       io1_a_dst = iop_a_dst;
     }
   }
@@ -8538,9 +8469,8 @@
 
   goto exit;
 exit:
-  if (a_dst.private_impl.buf) {
-    a_dst.private_impl.buf->meta.wi =
-        ((size_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr));
+  if (a_dst) {
+    a_dst->meta.wi = ((size_t)(iop_a_dst - a_dst->data.ptr));
   }
 
   return status;
@@ -8917,12 +8847,10 @@
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   uint32_t coro_susp_point = self->private_impl.p_ack_metadata_chunk[0];
@@ -8935,11 +8863,9 @@
       status = wuffs_base__error__bad_call_sequence;
       goto exit;
     }
-    if ((a_src.private_impl.buf
-             ? wuffs_base__u64__sat_add(
-                   a_src.private_impl.buf->meta.pos,
-                   ((uint64_t)(iop_a_src - a_src.private_impl.buf->data.ptr)))
-             : 0) != self->private_impl.f_metadata_io_position) {
+    if ((a_src ? wuffs_base__u64__sat_add(
+                     a_src->meta.pos, ((uint64_t)(iop_a_src - a_src->data.ptr)))
+               : 0) != self->private_impl.f_metadata_io_position) {
       status = wuffs_base__error__bad_i_o_position;
       goto exit;
     }
@@ -8952,12 +8878,10 @@
           (((uint64_t)(wuffs_base__load_u8be(iop_a_src))) + 1);
       if (self->private_impl.f_metadata_chunk_length_value > 1) {
         self->private_impl.f_metadata_io_position = wuffs_base__u64__sat_add(
-            (a_src.private_impl.buf
-                 ? wuffs_base__u64__sat_add(
-                       a_src.private_impl.buf->meta.pos,
-                       ((uint64_t)(iop_a_src -
-                                   a_src.private_impl.buf->data.ptr)))
-                 : 0),
+            (a_src ? wuffs_base__u64__sat_add(
+                         a_src->meta.pos,
+                         ((uint64_t)(iop_a_src - a_src->data.ptr)))
+                   : 0),
             self->private_impl.f_metadata_chunk_length_value);
         status = wuffs_base__warning__metadata_reported;
         goto ok;
@@ -8968,12 +8892,10 @@
       if (self->private_impl.f_metadata_chunk_length_value > 0) {
         (iop_a_src += 1, wuffs_base__make_empty_struct());
         self->private_impl.f_metadata_io_position = wuffs_base__u64__sat_add(
-            (a_src.private_impl.buf
-                 ? wuffs_base__u64__sat_add(
-                       a_src.private_impl.buf->meta.pos,
-                       ((uint64_t)(iop_a_src -
-                                   a_src.private_impl.buf->data.ptr)))
-                 : 0),
+            (a_src ? wuffs_base__u64__sat_add(
+                         a_src->meta.pos,
+                         ((uint64_t)(iop_a_src - a_src->data.ptr)))
+                   : 0),
             self->private_impl.f_metadata_chunk_length_value);
         status = wuffs_base__warning__metadata_reported;
         goto ok;
@@ -9000,9 +8922,8 @@
 
   goto exit;
 exit:
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   if (wuffs_base__status__is_error(status)) {
@@ -9182,12 +9103,10 @@
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   uint32_t coro_susp_point = self->private_impl.p_decode_frame_config[0];
@@ -9204,44 +9123,38 @@
      wuffs_base__make_empty_struct());
     if (!self->private_impl.f_end_of_data) {
       if (self->private_impl.f_call_sequence == 0) {
-        if (a_src.private_impl.buf) {
-          a_src.private_impl.buf->meta.ri =
-              ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+        if (a_src) {
+          a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
         }
         WUFFS_BASE__COROUTINE_SUSPENSION_POINT(1);
         status = wuffs_gif__decoder__decode_image_config(self, NULL, a_src);
-        if (a_src.private_impl.buf) {
-          iop_a_src = a_src.private_impl.buf->data.ptr +
-                      a_src.private_impl.buf->meta.ri;
+        if (a_src) {
+          iop_a_src = a_src->data.ptr + a_src->meta.ri;
         }
         if (status) {
           goto suspend;
         }
       } else if (self->private_impl.f_call_sequence != 3) {
         if (self->private_impl.f_call_sequence == 4) {
-          if (a_src.private_impl.buf) {
-            a_src.private_impl.buf->meta.ri =
-                ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+          if (a_src) {
+            a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
           }
           WUFFS_BASE__COROUTINE_SUSPENSION_POINT(2);
           status = wuffs_gif__decoder__skip_frame(self, a_src);
-          if (a_src.private_impl.buf) {
-            iop_a_src = a_src.private_impl.buf->data.ptr +
-                        a_src.private_impl.buf->meta.ri;
+          if (a_src) {
+            iop_a_src = a_src->data.ptr + a_src->meta.ri;
           }
           if (status) {
             goto suspend;
           }
         }
-        if (a_src.private_impl.buf) {
-          a_src.private_impl.buf->meta.ri =
-              ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+        if (a_src) {
+          a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
         }
         WUFFS_BASE__COROUTINE_SUSPENSION_POINT(3);
         status = wuffs_gif__decoder__decode_up_to_id_part1(self, a_src);
-        if (a_src.private_impl.buf) {
-          iop_a_src = a_src.private_impl.buf->data.ptr +
-                      a_src.private_impl.buf->meta.ri;
+        if (a_src) {
+          iop_a_src = a_src->data.ptr + a_src->meta.ri;
         }
         if (status) {
           goto suspend;
@@ -9310,9 +9223,8 @@
 
   goto exit;
 exit:
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   if (wuffs_base__status__is_error(status)) {
@@ -9334,12 +9246,10 @@
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   uint32_t coro_susp_point = self->private_impl.p_skip_frame[0];
@@ -9384,15 +9294,13 @@
       status = wuffs_gif__error__bad_literal_width;
       goto exit;
     }
-    if (a_src.private_impl.buf) {
-      a_src.private_impl.buf->meta.ri =
-          ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+    if (a_src) {
+      a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
     }
     WUFFS_BASE__COROUTINE_SUSPENSION_POINT(4);
     status = wuffs_gif__decoder__skip_blocks(self, a_src);
-    if (a_src.private_impl.buf) {
-      iop_a_src =
-          a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+    if (a_src) {
+      iop_a_src = a_src->data.ptr + a_src->meta.ri;
     }
     if (status) {
       goto suspend;
@@ -9418,9 +9326,8 @@
 
   goto exit;
 exit:
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   return status;
@@ -9535,12 +9442,10 @@
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   uint32_t coro_susp_point = self->private_impl.p_decode_up_to_id_part1[0];
@@ -9552,20 +9457,16 @@
     if (!self->private_impl.f_restarted) {
       if (self->private_impl.f_call_sequence != 2) {
         self->private_impl.f_frame_config_io_position =
-            (a_src.private_impl.buf
-                 ? wuffs_base__u64__sat_add(
-                       a_src.private_impl.buf->meta.pos,
-                       ((uint64_t)(iop_a_src -
-                                   a_src.private_impl.buf->data.ptr)))
-                 : 0);
+            (a_src ? wuffs_base__u64__sat_add(
+                         a_src->meta.pos,
+                         ((uint64_t)(iop_a_src - a_src->data.ptr)))
+                   : 0);
       }
     } else if (self->private_impl.f_frame_config_io_position !=
-               (a_src.private_impl.buf
-                    ? wuffs_base__u64__sat_add(
-                          a_src.private_impl.buf->meta.pos,
-                          ((uint64_t)(iop_a_src -
-                                      a_src.private_impl.buf->data.ptr)))
-                    : 0)) {
+               (a_src ? wuffs_base__u64__sat_add(
+                            a_src->meta.pos,
+                            ((uint64_t)(iop_a_src - a_src->data.ptr)))
+                      : 0)) {
       status = wuffs_base__error__bad_restart;
       goto exit;
     } else {
@@ -9582,15 +9483,13 @@
         v_block_type = t_0;
       }
       if (v_block_type == 33) {
-        if (a_src.private_impl.buf) {
-          a_src.private_impl.buf->meta.ri =
-              ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+        if (a_src) {
+          a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
         }
         WUFFS_BASE__COROUTINE_SUSPENSION_POINT(2);
         status = wuffs_gif__decoder__decode_extension(self, a_src);
-        if (a_src.private_impl.buf) {
-          iop_a_src = a_src.private_impl.buf->data.ptr +
-                      a_src.private_impl.buf->meta.ri;
+        if (a_src) {
+          iop_a_src = a_src->data.ptr + a_src->meta.ri;
         }
         if (status) {
           goto suspend;
@@ -9601,15 +9500,13 @@
           wuffs_base__u64__sat_add_indirect(
               &self->private_impl.f_num_decoded_frames_value, 1);
         }
-        if (a_src.private_impl.buf) {
-          a_src.private_impl.buf->meta.ri =
-              ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+        if (a_src) {
+          a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
         }
         WUFFS_BASE__COROUTINE_SUSPENSION_POINT(3);
         status = wuffs_gif__decoder__decode_id_part0(self, a_src);
-        if (a_src.private_impl.buf) {
-          iop_a_src = a_src.private_impl.buf->data.ptr +
-                      a_src.private_impl.buf->meta.ri;
+        if (a_src) {
+          iop_a_src = a_src->data.ptr + a_src->meta.ri;
         }
         if (status) {
           goto suspend;
@@ -9643,9 +9540,8 @@
 
   goto exit;
 exit:
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   return status;
@@ -9664,12 +9560,10 @@
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   uint32_t coro_susp_point = self->private_impl.p_decode_header[0];
@@ -9713,9 +9607,8 @@
 
   goto exit;
 exit:
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   return status;
@@ -9738,12 +9631,10 @@
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   uint32_t coro_susp_point = self->private_impl.p_decode_lsd[0];
@@ -9930,9 +9821,8 @@
 
   goto exit;
 exit:
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   return status;
@@ -9950,12 +9840,10 @@
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   uint32_t coro_susp_point = self->private_impl.p_decode_extension[0];
@@ -9974,15 +9862,13 @@
       v_label = t_0;
     }
     if (v_label == 249) {
-      if (a_src.private_impl.buf) {
-        a_src.private_impl.buf->meta.ri =
-            ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+      if (a_src) {
+        a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
       }
       WUFFS_BASE__COROUTINE_SUSPENSION_POINT(2);
       status = wuffs_gif__decoder__decode_gc(self, a_src);
-      if (a_src.private_impl.buf) {
-        iop_a_src =
-            a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+      if (a_src) {
+        iop_a_src = a_src->data.ptr + a_src->meta.ri;
       }
       if (status) {
         goto suspend;
@@ -9990,15 +9876,13 @@
       status = NULL;
       goto ok;
     } else if (v_label == 255) {
-      if (a_src.private_impl.buf) {
-        a_src.private_impl.buf->meta.ri =
-            ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+      if (a_src) {
+        a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
       }
       WUFFS_BASE__COROUTINE_SUSPENSION_POINT(3);
       status = wuffs_gif__decoder__decode_ae(self, a_src);
-      if (a_src.private_impl.buf) {
-        iop_a_src =
-            a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+      if (a_src) {
+        iop_a_src = a_src->data.ptr + a_src->meta.ri;
       }
       if (status) {
         goto suspend;
@@ -10006,15 +9890,13 @@
       status = NULL;
       goto ok;
     }
-    if (a_src.private_impl.buf) {
-      a_src.private_impl.buf->meta.ri =
-          ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+    if (a_src) {
+      a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
     }
     WUFFS_BASE__COROUTINE_SUSPENSION_POINT(4);
     status = wuffs_gif__decoder__skip_blocks(self, a_src);
-    if (a_src.private_impl.buf) {
-      iop_a_src =
-          a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+    if (a_src) {
+      iop_a_src = a_src->data.ptr + a_src->meta.ri;
     }
     if (status) {
       goto suspend;
@@ -10033,9 +9915,8 @@
 
   goto exit;
 exit:
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   return status;
@@ -10053,12 +9934,10 @@
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   uint32_t coro_susp_point = self->private_impl.p_skip_blocks[0];
@@ -10107,9 +9986,8 @@
 
   goto exit;
 exit:
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   return status;
@@ -10132,12 +10010,10 @@
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   uint32_t coro_susp_point = self->private_impl.p_decode_ae[0];
@@ -10303,12 +10179,10 @@
         (iop_a_src += 1, wuffs_base__make_empty_struct());
         self->private_impl.f_metadata_fourcc_value = 1229144912;
         self->private_impl.f_metadata_io_position = wuffs_base__u64__sat_add(
-            (a_src.private_impl.buf
-                 ? wuffs_base__u64__sat_add(
-                       a_src.private_impl.buf->meta.pos,
-                       ((uint64_t)(iop_a_src -
-                                   a_src.private_impl.buf->data.ptr)))
-                 : 0),
+            (a_src ? wuffs_base__u64__sat_add(
+                         a_src->meta.pos,
+                         ((uint64_t)(iop_a_src - a_src->data.ptr)))
+                   : 0),
             self->private_impl.f_metadata_chunk_length_value);
         self->private_impl.f_call_sequence = 1;
         status = wuffs_base__warning__metadata_reported;
@@ -10322,12 +10196,10 @@
             (((uint64_t)(wuffs_base__load_u8be(iop_a_src))) + 1);
         self->private_impl.f_metadata_fourcc_value = 1481461792;
         self->private_impl.f_metadata_io_position = wuffs_base__u64__sat_add(
-            (a_src.private_impl.buf
-                 ? wuffs_base__u64__sat_add(
-                       a_src.private_impl.buf->meta.pos,
-                       ((uint64_t)(iop_a_src -
-                                   a_src.private_impl.buf->data.ptr)))
-                 : 0),
+            (a_src ? wuffs_base__u64__sat_add(
+                         a_src->meta.pos,
+                         ((uint64_t)(iop_a_src - a_src->data.ptr)))
+                   : 0),
             self->private_impl.f_metadata_chunk_length_value);
         self->private_impl.f_call_sequence = 1;
         status = wuffs_base__warning__metadata_reported;
@@ -10336,15 +10208,13 @@
       goto label_0_break;
     }
   label_0_break:;
-    if (a_src.private_impl.buf) {
-      a_src.private_impl.buf->meta.ri =
-          ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+    if (a_src) {
+      a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
     }
     WUFFS_BASE__COROUTINE_SUSPENSION_POINT(12);
     status = wuffs_gif__decoder__skip_blocks(self, a_src);
-    if (a_src.private_impl.buf) {
-      iop_a_src =
-          a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+    if (a_src) {
+      iop_a_src = a_src->data.ptr + a_src->meta.ri;
     }
     if (status) {
       goto suspend;
@@ -10368,9 +10238,8 @@
 
   goto exit;
 exit:
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   return status;
@@ -10390,12 +10259,10 @@
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   uint32_t coro_susp_point = self->private_impl.p_decode_gc[0];
@@ -10502,9 +10369,8 @@
 
   goto exit;
 exit:
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   return status;
@@ -10520,12 +10386,10 @@
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   uint32_t coro_susp_point = self->private_impl.p_decode_id_part0[0];
@@ -10675,9 +10539,8 @@
 
   goto exit;
 exit:
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   return status;
@@ -10703,12 +10566,10 @@
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   uint32_t coro_susp_point = self->private_impl.p_decode_id_part1[0];
@@ -10873,9 +10734,8 @@
 
   goto exit;
 exit:
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   return status;
@@ -10907,12 +10767,10 @@
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   uint32_t coro_susp_point = self->private_impl.p_decode_id_part2[0];
@@ -11003,9 +10861,7 @@
                                             4096),
                   self->private_impl.f_compressed_ri,
                   self->private_impl.f_compressed_wi));
-          v_mark = (v_r.private_impl.buf
-                        ? ((uint64_t)(iop_v_r - v_r.private_impl.buf->data.ptr))
-                        : 0);
+          v_mark = (v_r ? ((uint64_t)(iop_v_r - v_r->data.ptr)) : 0);
           {
             u_r.meta.ri = ((size_t)(iop_v_r - u_r.data.ptr));
             wuffs_base__status t_1 = wuffs_lzw__decoder__decode_io_writer(
@@ -11017,10 +10873,8 @@
           }
           wuffs_base__u64__sat_add_indirect(
               &self->private_impl.f_compressed_ri,
-              (v_r.private_impl.buf
-                   ? wuffs_base__io__count_since(
-                         v_mark,
-                         ((uint64_t)(iop_v_r - v_r.private_impl.buf->data.ptr)))
+              (v_r ? wuffs_base__io__count_since(
+                         v_mark, ((uint64_t)(iop_v_r - v_r->data.ptr)))
                    : 0));
           v_r = o_0_v_r;
           iop_v_r = o_0_iop_v_r;
@@ -11050,15 +10904,13 @@
               goto suspend;
             }
             iop_a_src += self->private_data.s_decode_id_part2[0].scratch;
-            if (a_src.private_impl.buf) {
-              a_src.private_impl.buf->meta.ri =
-                  ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+            if (a_src) {
+              a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
             }
             WUFFS_BASE__COROUTINE_SUSPENSION_POINT(4);
             status = wuffs_gif__decoder__skip_blocks(self, a_src);
-            if (a_src.private_impl.buf) {
-              iop_a_src = a_src.private_impl.buf->data.ptr +
-                          a_src.private_impl.buf->meta.ri;
+            if (a_src) {
+              iop_a_src = a_src->data.ptr + a_src->meta.ri;
             }
             if (status) {
               goto suspend;
@@ -11108,9 +10960,8 @@
 
   goto exit;
 exit:
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   return status;
@@ -11396,25 +11247,21 @@
   uint8_t* iop_a_dst = NULL;
   uint8_t* io0_a_dst WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_dst WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_dst.private_impl.buf) {
-    iop_a_dst =
-        a_dst.private_impl.buf->data.ptr + a_dst.private_impl.buf->meta.wi;
+  if (a_dst) {
+    iop_a_dst = a_dst->data.ptr + a_dst->meta.wi;
     io0_a_dst = iop_a_dst;
-    io1_a_dst =
-        a_dst.private_impl.buf->data.ptr + a_dst.private_impl.buf->data.len;
-    if (a_dst.private_impl.buf->meta.closed) {
+    io1_a_dst = a_dst->data.ptr + a_dst->data.len;
+    if (a_dst->meta.closed) {
       io1_a_dst = iop_a_dst;
     }
   }
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   uint32_t coro_susp_point = self->private_impl.p_decode_io_writer[0];
@@ -11582,46 +11429,35 @@
       goto exit;
     }
     while (true) {
-      v_mark = (a_dst.private_impl.buf
-                    ? ((uint64_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr))
-                    : 0);
+      v_mark = (a_dst ? ((uint64_t)(iop_a_dst - a_dst->data.ptr)) : 0);
       {
-        if (a_dst.private_impl.buf) {
-          a_dst.private_impl.buf->meta.wi =
-              ((size_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr));
+        if (a_dst) {
+          a_dst->meta.wi = ((size_t)(iop_a_dst - a_dst->data.ptr));
         }
-        if (a_src.private_impl.buf) {
-          a_src.private_impl.buf->meta.ri =
-              ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+        if (a_src) {
+          a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
         }
         wuffs_base__status t_7 = wuffs_deflate__decoder__decode_io_writer(
             &self->private_data.f_flate, a_dst, a_src, a_workbuf);
-        if (a_dst.private_impl.buf) {
-          iop_a_dst = a_dst.private_impl.buf->data.ptr +
-                      a_dst.private_impl.buf->meta.wi;
+        if (a_dst) {
+          iop_a_dst = a_dst->data.ptr + a_dst->meta.wi;
         }
-        if (a_src.private_impl.buf) {
-          iop_a_src = a_src.private_impl.buf->data.ptr +
-                      a_src.private_impl.buf->meta.ri;
+        if (a_src) {
+          iop_a_src = a_src->data.ptr + a_src->meta.ri;
         }
         v_status = t_7;
       }
       if (!self->private_impl.f_ignore_checksum) {
         v_checksum_got = wuffs_crc32__ieee_hasher__update(
             &self->private_data.f_checksum,
-            (a_dst.private_impl.buf
-                 ? wuffs_base__io__since(
-                       v_mark,
-                       ((uint64_t)(iop_a_dst -
-                                   a_dst.private_impl.buf->data.ptr)),
-                       a_dst.private_impl.buf->data.ptr)
-                 : wuffs_base__make_slice_u8(NULL, 0)));
+            (a_dst ? wuffs_base__io__since(
+                         v_mark, ((uint64_t)(iop_a_dst - a_dst->data.ptr)),
+                         a_dst->data.ptr)
+                   : wuffs_base__make_slice_u8(NULL, 0)));
         v_decoded_length_got += ((uint32_t)(
-            ((a_dst.private_impl.buf
-                  ? wuffs_base__io__count_since(
-                        v_mark, ((uint64_t)(iop_a_dst -
-                                            a_dst.private_impl.buf->data.ptr)))
-                  : 0) &
+            ((a_dst ? wuffs_base__io__count_since(
+                          v_mark, ((uint64_t)(iop_a_dst - a_dst->data.ptr)))
+                    : 0) &
              4294967295)));
       }
       if (wuffs_base__status__is_ok(v_status)) {
@@ -11716,13 +11552,11 @@
 
   goto exit;
 exit:
-  if (a_dst.private_impl.buf) {
-    a_dst.private_impl.buf->meta.wi =
-        ((size_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr));
+  if (a_dst) {
+    a_dst->meta.wi = ((size_t)(iop_a_dst - a_dst->data.ptr));
   }
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   if (wuffs_base__status__is_error(status)) {
@@ -11885,25 +11719,21 @@
   uint8_t* iop_a_dst = NULL;
   uint8_t* io0_a_dst WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_dst WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_dst.private_impl.buf) {
-    iop_a_dst =
-        a_dst.private_impl.buf->data.ptr + a_dst.private_impl.buf->meta.wi;
+  if (a_dst) {
+    iop_a_dst = a_dst->data.ptr + a_dst->meta.wi;
     io0_a_dst = iop_a_dst;
-    io1_a_dst =
-        a_dst.private_impl.buf->data.ptr + a_dst.private_impl.buf->data.len;
-    if (a_dst.private_impl.buf->meta.closed) {
+    io1_a_dst = a_dst->data.ptr + a_dst->data.len;
+    if (a_dst->meta.closed) {
       io1_a_dst = iop_a_dst;
     }
   }
   uint8_t* iop_a_src = NULL;
   uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  if (a_src.private_impl.buf) {
-    iop_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.ri;
+  if (a_src) {
+    iop_a_src = a_src->data.ptr + a_src->meta.ri;
     io0_a_src = iop_a_src;
-    io1_a_src =
-        a_src.private_impl.buf->data.ptr + a_src.private_impl.buf->meta.wi;
+    io1_a_src = a_src->data.ptr + a_src->meta.wi;
   }
 
   uint32_t coro_susp_point = self->private_impl.p_decode_io_writer[0];
@@ -11959,40 +11789,31 @@
       goto exit;
     }
     while (true) {
-      v_mark = (a_dst.private_impl.buf
-                    ? ((uint64_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr))
-                    : 0);
+      v_mark = (a_dst ? ((uint64_t)(iop_a_dst - a_dst->data.ptr)) : 0);
       {
-        if (a_dst.private_impl.buf) {
-          a_dst.private_impl.buf->meta.wi =
-              ((size_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr));
+        if (a_dst) {
+          a_dst->meta.wi = ((size_t)(iop_a_dst - a_dst->data.ptr));
         }
-        if (a_src.private_impl.buf) {
-          a_src.private_impl.buf->meta.ri =
-              ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+        if (a_src) {
+          a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
         }
         wuffs_base__status t_1 = wuffs_deflate__decoder__decode_io_writer(
             &self->private_data.f_flate, a_dst, a_src, a_workbuf);
-        if (a_dst.private_impl.buf) {
-          iop_a_dst = a_dst.private_impl.buf->data.ptr +
-                      a_dst.private_impl.buf->meta.wi;
+        if (a_dst) {
+          iop_a_dst = a_dst->data.ptr + a_dst->meta.wi;
         }
-        if (a_src.private_impl.buf) {
-          iop_a_src = a_src.private_impl.buf->data.ptr +
-                      a_src.private_impl.buf->meta.ri;
+        if (a_src) {
+          iop_a_src = a_src->data.ptr + a_src->meta.ri;
         }
         v_status = t_1;
       }
       if (!self->private_impl.f_ignore_checksum) {
         v_checksum_got = wuffs_adler32__hasher__update(
             &self->private_data.f_checksum,
-            (a_dst.private_impl.buf
-                 ? wuffs_base__io__since(
-                       v_mark,
-                       ((uint64_t)(iop_a_dst -
-                                   a_dst.private_impl.buf->data.ptr)),
-                       a_dst.private_impl.buf->data.ptr)
-                 : wuffs_base__make_slice_u8(NULL, 0)));
+            (a_dst ? wuffs_base__io__since(
+                         v_mark, ((uint64_t)(iop_a_dst - a_dst->data.ptr)),
+                         a_dst->data.ptr)
+                   : wuffs_base__make_slice_u8(NULL, 0)));
       }
       if (wuffs_base__status__is_ok(v_status)) {
         goto label_0_break;
@@ -12052,13 +11873,11 @@
 
   goto exit;
 exit:
-  if (a_dst.private_impl.buf) {
-    a_dst.private_impl.buf->meta.wi =
-        ((size_t)(iop_a_dst - a_dst.private_impl.buf->data.ptr));
+  if (a_dst) {
+    a_dst->meta.wi = ((size_t)(iop_a_dst - a_dst->data.ptr));
   }
-  if (a_src.private_impl.buf) {
-    a_src.private_impl.buf->meta.ri =
-        ((size_t)(iop_a_src - a_src.private_impl.buf->data.ptr));
+  if (a_src) {
+    a_src->meta.ri = ((size_t)(iop_a_src - a_src->data.ptr));
   }
 
   if (wuffs_base__status__is_error(status)) {
diff --git a/test/c/std/gif.c b/test/c/std/gif.c
index c8a2374..d09b35b 100644
--- a/test/c/std/gif.c
+++ b/test/c/std/gif.c
@@ -73,8 +73,7 @@
 const char* test_basic_bad_receiver() {
   CHECK_FOCUS(__func__);
   wuffs_base__image_config ic = ((wuffs_base__image_config){});
-  wuffs_base__io_reader src = ((wuffs_base__io_reader){});
-  const char* status = wuffs_gif__decoder__decode_image_config(NULL, &ic, src);
+  const char* status = wuffs_gif__decoder__decode_image_config(NULL, &ic, NULL);
   if (status != wuffs_base__error__bad_receiver) {
     RETURN_FAIL("decode_image_config: got \"%s\", want \"%s\"", status,
                 wuffs_base__error__bad_receiver);
@@ -112,8 +111,7 @@
   CHECK_FOCUS(__func__);
   wuffs_gif__decoder dec = ((wuffs_gif__decoder){});
   wuffs_base__image_config ic = ((wuffs_base__image_config){});
-  wuffs_base__io_reader src = ((wuffs_base__io_reader){});
-  const char* status = wuffs_gif__decoder__decode_image_config(&dec, &ic, src);
+  const char* status = wuffs_gif__decoder__decode_image_config(&dec, &ic, NULL);
   if (status != wuffs_base__error__initialize_not_called) {
     RETURN_FAIL("decode_image_config: got \"%s\", want \"%s\"", status,
                 wuffs_base__error__initialize_not_called);