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/* A buffer that accumulates a string by piecewise concatenation, from the end
to the start.
Copyright (C) 2021-2025 Free Software Foundation, Inc.
This file is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation, either version 3 of the
License, or (at your option) any later version.
This file 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 Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Bruno Haible <bruno@clisp.org>, 2025. */
#include <config.h>
/* Specification. */
#include "string-buffer-reversed.h"
/* Undocumented. */
extern int sbr_ensure_more_bytes (struct string_buffer_reversed *buffer,
size_t increment);
#include <errno.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int
sbr_prependvf (struct string_buffer_reversed *buffer, const char *formatstring,
va_list list)
{
va_list list_copy;
/* Make a bit of room, so that the probability that the first vsnzprintf()
call succeeds is high. */
size_t room = buffer->allocated - buffer->length;
if (room < 64)
{
if (sbr_ensure_more_bytes (buffer, 64) < 0)
{
buffer->oom = true;
errno = ENOMEM;
return -1;
}
room = buffer->allocated - buffer->length;
}
va_copy (list_copy, list);
/* First vsnzprintf() call. */
ptrdiff_t ret = vsnzprintf (buffer->data, room, formatstring, list);
if (ret < 0)
{
/* Failed. errno is set. */
if (errno == ENOMEM)
buffer->oom = true;
else
buffer->error = true;
ret = -1;
}
else
{
if (ret <= room)
{
/* The result has fit into room bytes. */
memmove (buffer->data + buffer->allocated - buffer->length - (size_t) ret,
buffer->data,
(size_t) ret);
buffer->length += (size_t) ret;
ret = 0;
}
else
{
/* The result was truncated. Make more room, for a second
vsnzprintf() call. */
if (sbr_ensure_more_bytes (buffer, (size_t) ret) < 0)
{
buffer->oom = true;
errno = ENOMEM;
ret = -1;
}
else
{
/* Second vsnzprintf() call. */
room = buffer->allocated - buffer->length;
ret = vsnzprintf (buffer->data, room, formatstring, list_copy);
if (ret < 0)
{
/* Failed. errno is set. */
if (errno == ENOMEM)
buffer->oom = true;
else
buffer->error = true;
ret = -1;
}
else
{
if (ret <= room)
{
/* The result has fit into room bytes. */
memmove (buffer->data + buffer->allocated - buffer->length - (size_t) ret,
buffer->data,
(size_t) ret);
buffer->length += (size_t) ret;
ret = 0;
}
else
/* The return values of the vsnzprintf() calls are not
consistent. */
abort ();
}
}
}
}
va_end (list_copy);
return ret;
}
int
sbr_prependf (struct string_buffer_reversed *buffer, const char *formatstring,
...)
{
va_list args;
/* Make a bit of room, so that the probability that the first vsnzprintf()
call succeeds is high. */
size_t room = buffer->allocated - buffer->length;
if (room < 64)
{
if (sbr_ensure_more_bytes (buffer, 64) < 0)
{
buffer->oom = true;
errno = ENOMEM;
return -1;
}
room = buffer->allocated - buffer->length;
}
va_start (args, formatstring);
/* First vsnzprintf() call. */
ptrdiff_t ret = vsnzprintf (buffer->data, room, formatstring, args);
if (ret < 0)
{
/* Failed. errno is set. */
if (errno == ENOMEM)
buffer->oom = true;
else
buffer->error = true;
ret = -1;
}
else
{
if (ret <= room)
{
/* The result has fit into room bytes. */
memmove (buffer->data + buffer->allocated - buffer->length - (size_t) ret,
buffer->data,
(size_t) ret);
buffer->length += (size_t) ret;
ret = 0;
}
else
{
/* The result was truncated. Make more room, for a second
vsnzprintf() call. */
if (sbr_ensure_more_bytes (buffer, (size_t) ret) < 0)
{
buffer->oom = true;
errno = ENOMEM;
ret = -1;
}
else
{
/* Second vsnzprintf() call. */
room = buffer->allocated - buffer->length;
va_end (args);
va_start (args, formatstring);
ret = vsnzprintf (buffer->data, room, formatstring, args);
if (ret < 0)
{
/* Failed. errno is set. */
if (errno == ENOMEM)
buffer->oom = true;
else
buffer->error = true;
ret = -1;
}
else
{
if (ret <= room)
{
/* The result has fit into room bytes. */
memmove (buffer->data + buffer->allocated - buffer->length - (size_t) ret,
buffer->data,
(size_t) ret);
buffer->length += (size_t) ret;
ret = 0;
}
else
/* The return values of the vsnzprintf() calls are not
consistent. */
abort ();
}
}
}
}
va_end (args);
return ret;
}
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