gnunet/src/util/buffer.c

/*
  This file is part of GNUnet
  Copyright (C) 2020 GNUnet e.V.

  GNUnet is free software; you can redistribute it and/or modify it under the
  terms of the GNU Affero General Public License as published by the Free Software
  Foundation; either version 3, or (at your option) any later version.

  GNUnet is distributed in the hope that it will be useful, but WITHOUT ANY
  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
  A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more details.

  You should have received a copy of the GNU Affero General Public License along with
  GNUnet; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
*/
/**
 * @file buffer.c
 * @brief Common buffer management functions.
 * @author Florian Dold
 */
#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_buffer_lib.h"

/**
 * Initialize a buffer with the given capacity.
 *
 * When a buffer is allocated with this function, a warning is logged
 * when the buffer exceeds the initial capacity.
 *
 * @param buf the buffer to initialize
 * @param capacity the capacity (in bytes) to allocate for @a buf
 */
void
GNUNET_buffer_prealloc (struct GNUNET_Buffer *buf, size_t capacity)
{
  /* Buffer should be zero-initialized */
  GNUNET_assert (0 == buf->mem);
  GNUNET_assert (0 == buf->capacity);
  GNUNET_assert (0 == buf->position);
  buf->mem = GNUNET_malloc (capacity);
  buf->capacity = capacity;
  buf->warn_grow = GNUNET_YES;
}


/**
 * Make sure that at least @a n bytes remaining in the buffer.
 *
 * @param buf buffer to potentially grow
 * @param n number of bytes that should be available to write
 */
void
GNUNET_buffer_ensure_remaining (struct GNUNET_Buffer *buf,
                                size_t n)
{
  size_t new_capacity = buf->position + n;

  /* guard against overflow */
  GNUNET_assert (new_capacity >= buf->position);
  if (new_capacity <= buf->capacity)
    return;
  /* warn if calculation of expected size was wrong */
  GNUNET_break (GNUNET_YES != buf->warn_grow);
  if (new_capacity < buf->capacity * 2)
    new_capacity = buf->capacity * 2;
  buf->capacity = new_capacity;
  if (NULL != buf->mem)
    buf->mem = GNUNET_realloc (buf->mem, new_capacity);
  else
    buf->mem = GNUNET_malloc (new_capacity);
}


/**
 * Write bytes to the buffer.
 *
 * Grows the buffer if necessary.
 *
 * @param buf buffer to write to
 * @param data data to read from
 * @param len number of bytes to copy from @a data to @a buf
 */
void
GNUNET_buffer_write (struct GNUNET_Buffer *buf,
                     const char *data,
                     size_t len)
{
  GNUNET_buffer_ensure_remaining (buf, len);
  memcpy (buf->mem + buf->position, data, len);
  buf->position += len;
}


/**
 * Write a 0-terminated string to a buffer, excluding the 0-terminator.
 *
 * @param buf the buffer to write to
 * @param str the string to write to @a buf
 */
void
GNUNET_buffer_write_str (struct GNUNET_Buffer *buf,
                         const char *str)
{
  size_t len = strlen (str);

  GNUNET_buffer_write (buf, str, len);
}


/**
 * Clear the buffer and return the string it contained.
 * The caller is responsible to eventually #GNUNET_free
 * the returned string.
 *
 * The returned string is always 0-terminated.
 *
 * @param buf the buffer to reap the string from
 * @returns the buffer contained in the string
 */
char *
GNUNET_buffer_reap_str (struct GNUNET_Buffer *buf)
{
  char *res;

  /* ensure 0-termination */
  if ( (0 == buf->position) || ('\0' != buf->mem[buf->position - 1]))
  {
    GNUNET_buffer_ensure_remaining (buf, 1);
    buf->mem[buf->position++] = '\0';
  }
  res = buf->mem;
  memset (buf, 0, sizeof (struct GNUNET_Buffer));
  return res;
}


/**
 * Clear the buffer and return its contents.
 * The caller is responsible to eventually #GNUNET_free
 * the returned data.
 *
 * @param buf the buffer to reap the contents from
 * @param size where to store the size of the returned data
 * @returns the data contained in the string
 */
void *
GNUNET_buffer_reap (struct GNUNET_Buffer *buf, size_t *size)
{
  *size = buf->position;
  void *res = buf->mem;
  memset (buf, 0, sizeof (struct GNUNET_Buffer));
  return res;
}


/**
 * Free the backing memory of the given buffer.
 * Does not free the memory of the buffer control structure,
 * which is typically stack-allocated.
 */
void
GNUNET_buffer_clear (struct GNUNET_Buffer *buf)
{
  GNUNET_free_non_null (buf->mem);
  memset (buf, 0, sizeof (struct GNUNET_Buffer));
}


/**
 * Write a path component to a buffer, ensuring that
 * there is exactly one slash between the previous contents
 * of the buffer and the new string.
 *
 * @param buf buffer to write to
 * @param str string containing the new path component
 */
void
GNUNET_buffer_write_path (struct GNUNET_Buffer *buf, const char *str)
{
  size_t len = strlen (str);

  while ( (0 != len) && ('/' == str[0]) )
  {
    str++;
    len--;
  }
  if ( (0 == buf->position) || ('/' != buf->mem[buf->position - 1]) )
  {
    GNUNET_buffer_ensure_remaining (buf, 1);
    buf->mem[buf->position++] = '/';
  }
  GNUNET_buffer_write (buf, str, len);
}


/**
 * Write a 0-terminated formatted string to a buffer, excluding the
 * 0-terminator.
 *
 * Grows the buffer if necessary.
 *
 * @param buf the buffer to write to
 * @param fmt format string
 * @param ... format arguments
 */
void
GNUNET_buffer_write_fstr (struct GNUNET_Buffer *buf, const char *fmt, ...)
{
  va_list args;

  va_start (args, fmt);
  GNUNET_buffer_write_vfstr (buf, fmt, args);
  va_end (args);
}


/**
 * Write a 0-terminated formatted string to a buffer, excluding the
 * 0-terminator.
 *
 * Grows the buffer if necessary.
 *
 * @param buf the buffer to write to
 * @param fmt format string
 * @param args format argument list
 */
void
GNUNET_buffer_write_vfstr (struct GNUNET_Buffer *buf,
                           const char *fmt,
                           va_list args)
{
  int res;
  va_list args2;

  va_copy (args2, args);
  res = vsnprintf (NULL, 0, fmt, args2);
  va_end (args2);

  GNUNET_assert (res >= 0);
  GNUNET_buffer_ensure_remaining (buf, res + 1);

  va_copy (args2, args);
  res = vsnprintf (buf->mem + buf->position, res + 1, fmt, args2);
  va_end (args2);

  GNUNET_assert (res >= 0);
  buf->position += res;
  GNUNET_assert (buf->position <= buf->capacity);
}