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string-buffer-reversed: New module.

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* lib/string-buffer-reversed.h: New file, based on lib/string-buffer.h.
* lib/string-buffer-reversed.c: New file, based on lib/string-buffer.c.
* lib/string-buffer-reversed-printf.c: New file, based on
lib/string-buffer-printf.c.
* modules/string-buffer-reversed: New file.
This commit is contained in:
Bruno Haible
2025-02-05 20:57:16 +01:00
parent adb68524ad
commit 17a3c9deee
5 changed files with 669 additions and 0 deletions
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9
ChangeLog
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@@ -1,3 +1,12 @@
2025-02-05 Bruno Haible <bruno@clisp.org>
string-buffer-reversed: New module.
* lib/string-buffer-reversed.h: New file, based on lib/string-buffer.h.
* lib/string-buffer-reversed.c: New file, based on lib/string-buffer.c.
* lib/string-buffer-reversed-printf.c: New file, based on
lib/string-buffer-printf.c.
* modules/string-buffer-reversed: New file.
2025-02-05 Bruno Haible <bruno@clisp.org>
string-buffer: Improve comments.

207
lib/string-buffer-reversed-printf.c Normal file
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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->error = 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. */
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->error = 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. */
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->error = 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. */
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->error = 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. */
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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lib/string-buffer-reversed.c Normal file
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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 <stdio.h>
#include <stdlib.h>
#include <string.h>
/* The warnings about memory resource 'buffer->data' in this file are not
relevant. Silence them. */
#if __clang_major__ >= 3
# pragma clang diagnostic ignored "-Wthread-safety"
#endif
void
sbr_init (struct string_buffer_reversed *buffer)
{
buffer->data = buffer->space;
/* Pre-allocate a trailing NUL. This makes it easy to implement
sbr_contents_c(). */
buffer->data[sizeof (buffer->space) - 1] = '\0';
buffer->length = 1;
buffer->allocated = sizeof (buffer->space);
buffer->error = false;
}
/* Ensures that INCREMENT bytes are available beyond the current used length
of BUFFER.
Returns 0, or -1 in case of out-of-memory error. */
int
sbr_ensure_more_bytes (struct string_buffer_reversed *buffer, size_t increment)
{
size_t incremented_length = increment + buffer->length;
if (incremented_length < increment)
/* Overflow. */
return -1;
if (buffer->allocated < incremented_length)
{
size_t new_allocated = 2 * buffer->allocated;
if (new_allocated < buffer->allocated)
/* Overflow. */
return -1;
if (new_allocated < incremented_length)
new_allocated = incremented_length;
char *new_data;
if (buffer->data == buffer->space)
{
new_data = (char *) malloc (new_allocated);
if (new_data == NULL)
/* Out-of-memory. */
return -1;
memcpy (new_data + new_allocated - buffer->length,
buffer->data + buffer->allocated - buffer->length,
buffer->length);
}
else
{
new_data = (char *) realloc (buffer->data, new_allocated);
if (new_data == NULL)
/* Out-of-memory. */
return -1;
memmove (new_data + new_allocated - buffer->length,
new_data + buffer->allocated - buffer->length,
buffer->length);
}
buffer->data = new_data;
buffer->allocated = new_allocated;
}
return 0;
}
int
sbr_prepend1 (struct string_buffer_reversed *buffer, char c)
{
if (sbr_ensure_more_bytes (buffer, 1) < 0)
{
buffer->error = true;
return -1;
}
buffer->data[buffer->allocated - buffer->length - 1] = c;
buffer->length++;
return 0;
}
int
sbr_prepend_desc (struct string_buffer_reversed *buffer, string_desc_t s)
{
size_t len = sd_length (s);
if (sbr_ensure_more_bytes (buffer, len) < 0)
{
buffer->error = true;
return -1;
}
memcpy (buffer->data + buffer->allocated - buffer->length - len, sd_data (s), len);
buffer->length += len;
return 0;
}
int
sbr_prepend_c (struct string_buffer_reversed *buffer, const char *str)
{
size_t len = strlen (str);
if (sbr_ensure_more_bytes (buffer, len) < 0)
{
buffer->error = true;
return -1;
}
memcpy (buffer->data + buffer->allocated - buffer->length - len, str, len);
buffer->length += len;
return 0;
}
void
sbr_free (struct string_buffer_reversed *buffer)
{
if (buffer->data != buffer->space)
free (buffer->data);
}
string_desc_t
sbr_contents (struct string_buffer_reversed *buffer)
{
return sd_new_addr (buffer->length - 1,
buffer->data + buffer->allocated - buffer->length);
}
const char *
sbr_contents_c (struct string_buffer_reversed *buffer)
{
return buffer->data + buffer->allocated - buffer->length;
}
string_desc_t
sbr_dupfree (struct string_buffer_reversed *buffer)
{
if (buffer->error)
goto fail;
size_t length = buffer->length;
if (buffer->data == buffer->space)
{
char *copy = (char *) malloc (length > 1 ? length - 1 : 1);
if (copy == NULL)
goto fail;
memcpy (copy, buffer->data + buffer->allocated - length, length - 1);
return sd_new_addr (length - 1, copy);
}
else
{
/* Shrink the string before returning it. */
char *contents = buffer->data;
memmove (contents, contents + buffer->allocated - length, length - 1);
contents = realloc (contents, length > 1 ? length - 1 : 1);
if (contents == NULL)
goto fail;
return sd_new_addr (length - 1, contents);
}
fail:
sbr_free (buffer);
return sd_new_addr (0, NULL);
}
char *
sbr_dupfree_c (struct string_buffer_reversed *buffer)
{
if (buffer->error)
goto fail;
size_t length = buffer->length;
if (buffer->data == buffer->space)
{
char *copy = (char *) malloc (length);
if (copy == NULL)
goto fail;
memcpy (copy, buffer->data + buffer->allocated - length, length);
return copy;
}
else
{
/* Shrink the string before returning it. */
char *contents = buffer->data;
if (length < buffer->allocated)
{
memmove (contents, contents + buffer->allocated - length, length);
contents = realloc (contents, length);
if (contents == NULL)
goto fail;
}
return contents;
}
fail:
sbr_free (buffer);
return NULL;
}

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lib/string-buffer-reversed.h Normal file
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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. */
#ifndef _STRING_BUFFER_REVERSED_H
#define _STRING_BUFFER_REVERSED_H
/* This file uses _GL_ATTRIBUTE_MALLOC, _GL_ATTRIBUTE_RETURNS_NONNULL,
_GL_ATTRIBUTE_CAPABILITY_TYPE, _GL_ATTRIBUTE_ACQUIRE_CAPABILITY,
_GL_ATTRIBUTE_RELEASE_CAPABILITY. */
#if !_GL_CONFIG_H_INCLUDED
#error "Please include config.h first."
#endif
#include <stdarg.h>
#include <stdlib.h>
#include "attribute.h"
#include "string-desc.h"
typedef char * _GL_ATTRIBUTE_CAPABILITY_TYPE ("memory resource")
sbr_heap_allocated_pointer_t;
/* A string buffer type. */
struct string_buffer_reversed
{
/* data[allocated-length .. allocated-1] are used. */
sbr_heap_allocated_pointer_t data;
size_t length; /* used bytes, <= allocated */
size_t allocated; /* allocated bytes */
bool error; /* true if there was an error */
char space[1024]; /* stack allocated space */
};
#ifdef __cplusplus
extern "C" {
#endif
/* ================== Functions in module 'string-buffer' ================== */
/* Initializes BUFFER to the empty string. */
extern void sbr_init (struct string_buffer_reversed *buffer)
_GL_ATTRIBUTE_ACQUIRE_CAPABILITY (buffer->data);
/* Prepends the character C to BUFFER.
Returns 0, or -1 in case of out-of-memory error. */
extern int sbr_prepend1 (struct string_buffer_reversed *buffer, char c);
/* Prepends the contents of the memory area S to BUFFER.
Returns 0, or -1 in case of out-of-memory error. */
extern int sbr_prepend_desc (struct string_buffer_reversed *buffer,
string_desc_t s);
/* Prepends the contents of the C string STR to BUFFER.
Returns 0, or -1 in case of out-of-memory error. */
extern int sbr_prepend_c (struct string_buffer_reversed *buffer,
const char *str);
/* Prepends the result of the printf-compatible FORMATSTRING with the argument
list LIST to BUFFER.
Returns 0, or -1 with errno set in case of error.
Error code EOVERFLOW can only occur when a width > INT_MAX is used.
Therefore, if the format string is valid and does not use %ls/%lc
directives nor widths, the only possible error code is ENOMEM. */
extern int sbr_prependvf (struct string_buffer_reversed *buffer,
const char *formatstring, va_list list)
#if (__GNUC__ + (__GNUC_MINOR__ >= 4) > 4) && !defined __clang__
ATTRIBUTE_FORMAT ((__gnu_printf__, 2, 0))
#else
ATTRIBUTE_FORMAT ((__printf__, 2, 0))
#endif
;
/* Prepends the result of the printf-compatible FORMATSTRING with the following
arguments to BUFFER.
Returns 0, or -1 with errno set in case of error.
Error code EOVERFLOW can only occur when a width > INT_MAX is used.
Therefore, if the format string is valid and does not use %ls/%lc
directives nor widths, the only possible error code is ENOMEM. */
extern int sbr_prependf (struct string_buffer_reversed *buffer,
const char *formatstring, ...)
#if (__GNUC__ + (__GNUC_MINOR__ >= 4) > 4) && !defined __clang__
ATTRIBUTE_FORMAT ((__gnu_printf__, 2, 3))
#else
ATTRIBUTE_FORMAT ((__printf__, 2, 3))
#endif
;
/* Frees the memory held by BUFFER. */
extern void sbr_free (struct string_buffer_reversed *buffer)
_GL_ATTRIBUTE_RELEASE_CAPABILITY (buffer->data);
/* Returns a read-only view of the current contents of BUFFER.
The result is only valid until the next operation on BUFFER. */
extern string_desc_t sbr_contents (struct string_buffer_reversed *buffer);
/* Ensures the contents of BUFFER is followed by a NUL byte (without
incrementing the length of the contents).
Then returns a read-only view of the current contents of BUFFER,
that is, the current contents of BUFFER as a C string.
The result is only valid until the next operation on BUFFER. */
extern const char * sbr_contents_c (struct string_buffer_reversed *buffer);
/* Returns the contents of BUFFER and frees all other memory held by BUFFER.
Returns NULL upon failure or if there was an error earlier.
It is the responsibility of the caller to sd_free() the result. */
extern string_desc_t sbr_dupfree (struct string_buffer_reversed *buffer)
_GL_ATTRIBUTE_RELEASE_CAPABILITY (buffer->data);
/* Returns the contents of BUFFER (with an added trailing NUL, that is,
as a C string), and frees all other memory held by BUFFER.
Returns NULL upon failure or if there was an error earlier.
It is the responsibility of the caller to free() the result. */
extern char * sbr_dupfree_c (struct string_buffer_reversed *buffer)
_GL_ATTRIBUTE_RELEASE_CAPABILITY (buffer->data);
/* ================== Functions in module 'xstring-buffer' ================== */
#if GNULIB_XSTRING_BUFFER_REVERSED
/* The following functions invoke xalloc_die () in case of out-of-memory
error. */
/* Prepends the character C to BUFFER. */
extern void sbr_xprepend1 (struct string_buffer_reversed *buffer, char c);
/* Prepends the contents of the memory area S to BUFFER. */
extern void sbr_xprepend_desc (struct string_buffer_reversed *buffer,
string_desc_t s);
/* Prepends the contents of the C string STR to BUFFER. */
extern void sbr_xprepend_c (struct string_buffer_reversed *buffer,
const char *str);
/* Prepends the result of the printf-compatible FORMATSTRING with the argument
list LIST to BUFFER.
Returns 0, or -1 in case of error other than out-of-memory error.
Error code EOVERFLOW can only occur when a width > INT_MAX is used.
Therefore, if the format string is valid and does not use %ls/%lc
directives nor widths, no error is possible. */
extern int sbr_xprependvf (struct string_buffer_reversed *buffer,
const char *formatstring, va_list list)
#if (__GNUC__ + (__GNUC_MINOR__ >= 4) > 4) && !defined __clang__
ATTRIBUTE_FORMAT ((__gnu_printf__, 2, 0))
#else
ATTRIBUTE_FORMAT ((__printf__, 2, 0))
#endif
;
/* Prepends the result of the printf-compatible FORMATSTRING with the following
arguments to BUFFER.
Returns 0, or -1 in case of error other than out-of-memory error.
Error code EOVERFLOW can only occur when a width > INT_MAX is used.
Therefore, if the format string is valid and does not use %ls/%lc
directives nor widths, no error is possible. */
extern int sbr_xprependf (struct string_buffer_reversed *buffer,
const char *formatstring, ...)
#if (__GNUC__ + (__GNUC_MINOR__ >= 4) > 4) && !defined __clang__
ATTRIBUTE_FORMAT ((__gnu_printf__, 2, 3))
#else
ATTRIBUTE_FORMAT ((__printf__, 2, 3))
#endif
;
/* Returns the contents of BUFFER and frees all other memory held by BUFFER.
Returns (0, NULL) if there was an error earlier.
It is the responsibility of the caller to sd_free() the result. */
extern string_desc_t sbr_xdupfree (struct string_buffer_reversed *buffer)
_GL_ATTRIBUTE_RELEASE_CAPABILITY (buffer->data);
/* Returns the contents of BUFFER (with an added trailing NUL, that is,
as a C string), and frees all other memory held by BUFFER.
Returns NULL if there was an error earlier.
It is the responsibility of the caller to free() the result. */
extern char * sbr_xdupfree_c (struct string_buffer_reversed *buffer)
_GL_ATTRIBUTE_MALLOC _GL_ATTRIBUTE_DEALLOC_FREE
_GL_ATTRIBUTE_RELEASE_CAPABILITY (buffer->data);
#endif /* GNULIB_XSTRING_BUFFER_REVERSED */
/* ========================================================================== */
#ifdef __cplusplus
}
#endif
#endif /* _STRING_BUFFER_REVERSED_H */

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modules/string-buffer-reversed Normal file
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Description:
A buffer that accumulates a string by piecewise concatenation,
from the end to the start.
Files:
lib/string-buffer-reversed.h
lib/string-buffer-reversed.c
lib/string-buffer-reversed-printf.c
Depends-on:
bool
attribute
string-desc
stdarg-h
vsnzprintf-posix
configure.ac:
Makefile.am:
lib_SOURCES += string-buffer-reversed.c string-buffer-reversed-printf.c
Include:
"string-buffer-reversed.h"
License:
LGPL
Maintainer:
all