src/buffer.c

#include <stdarg.h>
#include <string.h>
#include <assert.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

#include "config.h"
#include "cmark_ctype.h"
#include "buffer.h"

/* Used as default value for cmark_strbuf->ptr so that people can always
 * assume ptr is non-NULL and zero terminated even for new cmark_strbufs.
 */
unsigned char cmark_strbuf__initbuf[1];

#ifndef MIN
#define MIN(x, y) ((x < y) ? x : y)
#endif

void cmark_strbuf_init(cmark_strbuf *buf, bufsize_t initial_size) {
  buf->asize = 0;
  buf->size = 0;
  buf->ptr = cmark_strbuf__initbuf;

  if (initial_size > 0)
    cmark_strbuf_grow(buf, initial_size);
}

void cmark_strbuf_overflow_err() {
  fprintf(stderr, "String buffer overflow");
  abort();
}

static inline void S_strbuf_grow_by(cmark_strbuf *buf, size_t add) {
  size_t target_size = (size_t)buf->size + add;

  if (target_size < add            /* Integer overflow. */
      || target_size > BUFSIZE_MAX /* Truncation overflow. */
      ) {
    cmark_strbuf_overflow_err();
    return; /* unreachable */
  }

  if ((bufsize_t)target_size >= buf->asize)
    cmark_strbuf_grow(buf, (bufsize_t)target_size);
}

void cmark_strbuf_grow(cmark_strbuf *buf, bufsize_t target_size) {
  unsigned char *new_ptr;

  if (target_size < buf->asize)
    return;

  if (buf->asize == 0) {
    new_ptr = NULL;
  } else {
    new_ptr = buf->ptr;
  }

  /* Oversize the buffer by 50% to guarantee amortized linear time
   * complexity on append operations. */
  size_t new_size = (size_t)target_size + (size_t)target_size / 2;

  /* Account for terminating null byte. */
  new_size += 1;

  /* round allocation up to multiple of 8 */
  new_size = (new_size + 7) & ~7;

  if (new_size < (size_t)target_size /* Integer overflow. */
      || new_size > BUFSIZE_MAX      /* Truncation overflow. */
      ) {
    if (target_size >= BUFSIZE_MAX) {
      /* No space for terminating null byte. */
      cmark_strbuf_overflow_err();
      return; /* unreachable */
    }
    /* Oversize by the maximum possible amount. */
    new_size = BUFSIZE_MAX;
  }

  new_ptr = (unsigned char *)realloc(new_ptr, new_size);

  if (!new_ptr) {
    perror("realloc in cmark_strbuf_grow");
    abort();
  }

  buf->asize = (bufsize_t)new_size;
  buf->ptr = new_ptr;
}

bufsize_t cmark_strbuf_len(const cmark_strbuf *buf) { return buf->size; }

void cmark_strbuf_free(cmark_strbuf *buf) {
  if (!buf)
    return;

  if (buf->ptr != cmark_strbuf__initbuf)
    free(buf->ptr);

  cmark_strbuf_init(buf, 0);
}

void cmark_strbuf_clear(cmark_strbuf *buf) {
  buf->size = 0;

  if (buf->asize > 0)
    buf->ptr[0] = '\0';
}

void cmark_strbuf_set(cmark_strbuf *buf, const unsigned char *data,
                      bufsize_t len) {
  if (len <= 0 || data == NULL) {
    cmark_strbuf_clear(buf);
  } else {
    if (data != buf->ptr) {
      if (len >= buf->asize)
        cmark_strbuf_grow(buf, len);
      memmove(buf->ptr, data, len);
    }
    buf->size = len;
    buf->ptr[buf->size] = '\0';
  }
}

void cmark_strbuf_sets(cmark_strbuf *buf, const char *string) {
  cmark_strbuf_set(buf, (const unsigned char *)string,
                   string ? cmark_strbuf_safe_strlen(string) : 0);
}

void cmark_strbuf_putc(cmark_strbuf *buf, int c) {
  S_strbuf_grow_by(buf, 1);
  buf->ptr[buf->size++] = (unsigned char)(c & 0xFF);
  buf->ptr[buf->size] = '\0';
}

void cmark_strbuf_put(cmark_strbuf *buf, const unsigned char *data,
                      bufsize_t len) {
  if (len <= 0)
    return;

  S_strbuf_grow_by(buf, len);
  memmove(buf->ptr + buf->size, data, len);
  buf->size += len;
  buf->ptr[buf->size] = '\0';
}

void cmark_strbuf_puts(cmark_strbuf *buf, const char *string) {
  cmark_strbuf_put(buf, (const unsigned char *)string,
                   cmark_strbuf_safe_strlen(string));
}

void cmark_strbuf_copy_cstr(char *data, bufsize_t datasize,
                            const cmark_strbuf *buf) {
  bufsize_t copylen;

  assert(buf);
  if (!data || datasize <= 0)
    return;

  data[0] = '\0';

  if (buf->size == 0 || buf->asize <= 0)
    return;

  copylen = buf->size;
  if (copylen > datasize - 1)
    copylen = datasize - 1;
  memmove(data, buf->ptr, copylen);
  data[copylen] = '\0';
}

void cmark_strbuf_swap(cmark_strbuf *buf_a, cmark_strbuf *buf_b) {
  cmark_strbuf t = *buf_a;
  *buf_a = *buf_b;
  *buf_b = t;
}

unsigned char *cmark_strbuf_detach(cmark_strbuf *buf) {
  unsigned char *data = buf->ptr;

  if (buf->asize == 0) {
    /* return an empty string */
    return (unsigned char *)calloc(1, 1);
  }

  cmark_strbuf_init(buf, 0);
  return data;
}

int cmark_strbuf_cmp(const cmark_strbuf *a, const cmark_strbuf *b) {
  int result = memcmp(a->ptr, b->ptr, MIN(a->size, b->size));
  return (result != 0) ? result
                       : (a->size < b->size) ? -1 : (a->size > b->size) ? 1 : 0;
}

bufsize_t cmark_strbuf_strchr(const cmark_strbuf *buf, int c, bufsize_t pos) {
  if (pos >= buf->size)
    return -1;
  if (pos < 0)
    pos = 0;

  const unsigned char *p =
      (unsigned char *)memchr(buf->ptr + pos, c, buf->size - pos);
  if (!p)
    return -1;

  return (bufsize_t)(p - (const unsigned char *)buf->ptr);
}

bufsize_t cmark_strbuf_strrchr(const cmark_strbuf *buf, int c, bufsize_t pos) {
  if (pos < 0 || buf->size == 0)
    return -1;
  if (pos >= buf->size)
    pos = buf->size - 1;

  for (bufsize_t i = pos; i >= 0; i--) {
    if (buf->ptr[i] == (unsigned char)c)
      return i;
  }

  return -1;
}

void cmark_strbuf_truncate(cmark_strbuf *buf, bufsize_t len) {
  if (len < 0)
    len = 0;

  if (len < buf->size) {
    buf->size = len;
    buf->ptr[buf->size] = '\0';
  }
}

void cmark_strbuf_drop(cmark_strbuf *buf, bufsize_t n) {
  if (n > 0) {
    if (n > buf->size)
      n = buf->size;
    buf->size = buf->size - n;
    if (buf->size)
      memmove(buf->ptr, buf->ptr + n, buf->size);

    buf->ptr[buf->size] = '\0';
  }
}

void cmark_strbuf_rtrim(cmark_strbuf *buf) {
  if (!buf->size)
    return;

  while (buf->size > 0) {
    if (!cmark_isspace(buf->ptr[buf->size - 1]))
      break;

    buf->size--;
  }

  buf->ptr[buf->size] = '\0';
}

void cmark_strbuf_trim(cmark_strbuf *buf) {
  bufsize_t i = 0;

  if (!buf->size)
    return;

  while (i < buf->size && cmark_isspace(buf->ptr[i]))
    i++;

  cmark_strbuf_drop(buf, i);

  cmark_strbuf_rtrim(buf);
}

// Destructively modify string, collapsing consecutive
// space and newline characters into a single space.
void cmark_strbuf_normalize_whitespace(cmark_strbuf *s) {
  bool last_char_was_space = false;
  bufsize_t r, w;

  for (r = 0, w = 0; r < s->size; ++r) {
    if (cmark_isspace(s->ptr[r])) {
      if (!last_char_was_space) {
        s->ptr[w++] = ' ';
        last_char_was_space = true;
      }
    } else {
      s->ptr[w++] = s->ptr[r];
      last_char_was_space = false;
    }
  }

  cmark_strbuf_truncate(s, w);
}

// Destructively unescape a string: remove backslashes before punctuation chars.
extern void cmark_strbuf_unescape(cmark_strbuf *buf) {
  bufsize_t r, w;

  for (r = 0, w = 0; r < buf->size; ++r) {
    if (buf->ptr[r] == '\\' && cmark_ispunct(buf->ptr[r + 1]))
      r++;

    buf->ptr[w++] = buf->ptr[r];
  }

  cmark_strbuf_truncate(buf, w);
}