add ffi_get_struct_offsets
diff --git a/doc/libffi.texi b/doc/libffi.texi
index 5c9fddd..94b7a9e 100644
--- a/doc/libffi.texi
+++ b/doc/libffi.texi
@@ -440,7 +440,8 @@
@item
The size and alignment of a new structure type will not be set by
-@code{libffi} until it has been passed to @code{ffi_prep_cif}.
+@code{libffi} until it has been passed to @code{ffi_prep_cif} or
+@code{ffi_get_struct_offsets}.
@item
A structure type cannot be shared across ABIs. Instead each ABI needs
@@ -448,8 +449,9 @@
@end itemize
So, before examining these fields, it is safest to pass the
-@code{ffi_type} object to @code{ffi_prep_cif} first. This function
-will do all the needed setup.
+@code{ffi_type} object to @code{ffi_prep_cif} or
+@code{ffi_get_struct_offsets} first. This function will do all the
+needed setup.
@example
ffi_type *desired_type;
@@ -463,6 +465,28 @@
@}
@end example
+@code{libffi} also provides a way to get the offsets of the members of
+a structure.
+
+@findex ffi_get_struct_offsets
+@defun ffi_status ffi_get_struct_offsets (ffi_abi abi, ffi_type *struct_type, size_t *offsets)
+Compute the offset of each element of the given structure type.
+@var{abi} is the ABI to use; this is needed because in some cases the
+layout depends on the ABI.
+
+@var{sizes} is an out parameter. The caller is responsible for
+providing enough space for all the results to be written -- one
+element per element type in @var{struct_type}. If @var{sizes} is
+@code{NULL}, then the type will be laid out but not otherwise
+modified. This can be useful for accessing the type's size or layout,
+as mentioned above.
+
+This function returns @code{FFI_OK} on success; @code{FFI_BAD_ABI} if
+@var{abi} is invalid; or @code{FFI_BAD_TYPEDEF} if @var{struct_type}
+is invalid in some way. Note that only @code{FFI_STRUCT} types are
+valid here.
+@end defun
+
@node Arrays Unions Enums
@subsection Arrays, Unions, and Enumerations
diff --git a/include/ffi.h.in b/include/ffi.h.in
index cd3358f..9e65277 100644
--- a/include/ffi.h.in
+++ b/include/ffi.h.in
@@ -458,6 +458,9 @@
void *rvalue,
void **avalue);
+ffi_status ffi_get_struct_offsets (ffi_abi abi, ffi_type *struct_type,
+ size_t *offsets);
+
/* Useful for eliminating compiler warnings */
#define FFI_FN(f) ((void (*)(void))f)
diff --git a/src/prep_cif.c b/src/prep_cif.c
index 5881ceb..43f0487 100644
--- a/src/prep_cif.c
+++ b/src/prep_cif.c
@@ -34,7 +34,7 @@
/* Perform machine independent initialization of aggregate type
specifications. */
-static ffi_status initialize_aggregate(ffi_type *arg)
+static ffi_status initialize_aggregate(ffi_type *arg, size_t *offsets)
{
ffi_type **ptr;
@@ -52,13 +52,15 @@
while ((*ptr) != NULL)
{
if (UNLIKELY(((*ptr)->size == 0)
- && (initialize_aggregate((*ptr)) != FFI_OK)))
+ && (initialize_aggregate((*ptr), NULL) != FFI_OK)))
return FFI_BAD_TYPEDEF;
/* Perform a sanity check on the argument type */
FFI_ASSERT_VALID_TYPE(*ptr);
arg->size = ALIGN(arg->size, (*ptr)->alignment);
+ if (offsets)
+ *offsets++ = arg->size;
arg->size += (*ptr)->size;
arg->alignment = (arg->alignment > (*ptr)->alignment) ?
@@ -133,7 +135,8 @@
#endif
/* Initialize the return type if necessary */
- if ((cif->rtype->size == 0) && (initialize_aggregate(cif->rtype) != FFI_OK))
+ if ((cif->rtype->size == 0)
+ && (initialize_aggregate(cif->rtype, NULL) != FFI_OK))
return FFI_BAD_TYPEDEF;
#ifndef FFI_TARGET_HAS_COMPLEX_TYPE
@@ -164,7 +167,8 @@
{
/* Initialize any uninitialized aggregate type definitions */
- if (((*ptr)->size == 0) && (initialize_aggregate((*ptr)) != FFI_OK))
+ if (((*ptr)->size == 0)
+ && (initialize_aggregate((*ptr), NULL) != FFI_OK))
return FFI_BAD_TYPEDEF;
#ifndef FFI_TARGET_HAS_COMPLEX_TYPE
@@ -240,3 +244,18 @@
}
#endif
+
+ffi_status
+ffi_get_struct_offsets (ffi_abi abi, ffi_type *struct_type, size_t *offsets)
+{
+ if (! (abi > FFI_FIRST_ABI && abi < FFI_LAST_ABI))
+ return FFI_BAD_ABI;
+ if (struct_type->type != FFI_TYPE_STRUCT)
+ return FFI_BAD_TYPEDEF;
+
+#if HAVE_LONG_DOUBLE_VARIANT
+ ffi_prep_types (abi);
+#endif
+
+ return initialize_aggregate(struct_type, offsets);
+}
diff --git a/testsuite/libffi.call/offsets.c b/testsuite/libffi.call/offsets.c
new file mode 100644
index 0000000..23d88b3
--- /dev/null
+++ b/testsuite/libffi.call/offsets.c
@@ -0,0 +1,46 @@
+/* Area: Struct layout
+ Purpose: Test ffi_get_struct_offsets
+ Limitations: none.
+ PR: none.
+ Originator: Tom Tromey. */
+
+/* { dg-do run } */
+#include "ffitest.h"
+#include <stddef.h>
+
+struct test_1
+{
+ char c;
+ float f;
+ char c2;
+ int i;
+};
+
+int
+main (void)
+{
+ ffi_type test_1_type;
+ ffi_type *test_1_elements[5];
+ size_t test_1_offsets[4];
+
+ test_1_elements[0] = &ffi_type_schar;
+ test_1_elements[1] = &ffi_type_float;
+ test_1_elements[2] = &ffi_type_schar;
+ test_1_elements[3] = &ffi_type_sint;
+ test_1_elements[4] = NULL;
+
+ test_1_type.size = 0;
+ test_1_type.alignment = 0;
+ test_1_type.type = FFI_TYPE_STRUCT;
+ test_1_type.elements = test_1_elements;
+
+ CHECK (ffi_get_struct_offsets (FFI_DEFAULT_ABI, &test_1_type, test_1_offsets)
+ == FFI_OK);
+ CHECK (test_1_type.size == sizeof (struct test_1));
+ CHECK (offsetof (struct test_1, c) == test_1_offsets[0]);
+ CHECK (offsetof (struct test_1, f) == test_1_offsets[1]);
+ CHECK (offsetof (struct test_1, c2) == test_1_offsets[2]);
+ CHECK (offsetof (struct test_1, i) == test_1_offsets[3]);
+
+ return 0;
+}
