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glibc/stdio-common/printf_buffer_to_file.h

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stdio-common: Introduce buffers for implementing printf These buffers will eventually be used instead of FILE * objects to implement printf functions. The multibyte buffer is struct __printf_buffer, the wide buffer is struct __wprintf_buffer. To enable writing type-generic code, the header files printf_buffer-char.h and printf_buffer-wchar_t.h define the Xprintf macro differently, enabling Xprintf (buffer) to stand for __printf_buffer and __wprintf_buffer as appropriate. For common cases, macros like Xprintf_buffer are provided as a more syntactically convenient shortcut. Buffer-specific flush callbacks are implemented with a switch statement instead of a function pointer, to avoid hardening issues similar to those of libio vtables. struct __printf_buffer_as_file is needed to support custom printf specifiers because the public interface for that requires passing a FILE *, which is why there is a trapdoor back from these buffers to FILE * streams. Since the immediate user of these interfaces knows when processing has finished, there is no flush callback for the end of processing, only a flush callback for the intermediate buffer flush. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2022-12-19 17:56:54 +00:00
/* Multibyte and wide printf buffers writing data to a FILE * stream.
Update copyright dates with scripts/update-copyrights
2024-01-01 18:12:26 +00:00
Copyright (C) 2022-2024 Free Software Foundation, Inc.
stdio-common: Introduce buffers for implementing printf These buffers will eventually be used instead of FILE * objects to implement printf functions. The multibyte buffer is struct __printf_buffer, the wide buffer is struct __wprintf_buffer. To enable writing type-generic code, the header files printf_buffer-char.h and printf_buffer-wchar_t.h define the Xprintf macro differently, enabling Xprintf (buffer) to stand for __printf_buffer and __wprintf_buffer as appropriate. For common cases, macros like Xprintf_buffer are provided as a more syntactically convenient shortcut. Buffer-specific flush callbacks are implemented with a switch statement instead of a function pointer, to avoid hardening issues similar to those of libio vtables. struct __printf_buffer_as_file is needed to support custom printf specifiers because the public interface for that requires passing a FILE *, which is why there is a trapdoor back from these buffers to FILE * streams. Since the immediate user of these interfaces knows when processing has finished, there is no flush callback for the end of processing, only a flush callback for the intermediate buffer flush. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2022-12-19 17:56:54 +00:00
This file is part of the GNU C Library.
The GNU C Library 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 2.1 of the License, or (at your option) any later version.
The GNU C Library 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 the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#ifndef PRINTF_BUFFER_TO_FILE_H
#define PRINTF_BUFFER_TO_FILE_H
#include <bits/types/FILE.h>
#include <printf_buffer.h>
struct __printf_buffer_to_file
{
struct __printf_buffer base;
FILE *fp;
/* Staging buffer. Used if fp does not have any available buffer
space. */
char stage[PRINTF_BUFFER_SIZE_TO_FILE_STAGE];
};
/* Initializes *BUF to write data to FP. */
void __printf_buffer_to_file_init (struct __printf_buffer_to_file *buf,
FILE *fp) attribute_hidden;
/* Transfers any pending data in BUF to BUF->FP. The return value
follows the printf convention (number bytes written; or -1 for error). */
int __printf_buffer_to_file_done (struct __printf_buffer_to_file *buf)
attribute_hidden;
/* Wide version below. */
struct __wprintf_buffer_to_file
{
struct __wprintf_buffer base;
FILE *fp;
wchar_t stage[PRINTF_BUFFER_SIZE_TO_FILE_STAGE];
};
void __wprintf_buffer_to_file_init (struct __wprintf_buffer_to_file *buf,
FILE *fp) attribute_hidden;
int __wprintf_buffer_to_file_done (struct __wprintf_buffer_to_file *buf)
attribute_hidden;
#endif /* PRINTF_BUFFER_TO_FILE_H */
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