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659fe9fdd1
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>
88 lines
2.7 KiB
C
88 lines
2.7 KiB
C
/* FILE * interface to a struct __*printf_buffer.
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Copyright (C) 2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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/* Registered printf format specifier callbacks produce data via a
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FILE * stream. struct __printf_buffer_as_file enables vfprintf to
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create a suitable stdio stream. Likewise struct
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__wprintf_buffer_as_file for vfwprintf. */
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#ifndef PRINTF_BUFFER_AS_FILE_H
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#define PRINTF_BUFFER_AS_FILE_H
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#include <libio/libioP.h>
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struct __printf_buffer;
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struct __printf_buffer_as_file
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{
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/* Interface to libio. */
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FILE stream;
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const struct _IO_jump_t *vtable;
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/* Pointer to the underlying buffer. */
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struct __printf_buffer *next;
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};
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/* Initialization *FP so that data written to its FILE * stream ends
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up in NEXT. */
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void __printf_buffer_as_file_init (struct __printf_buffer_as_file *fp,
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struct __printf_buffer *next)
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attribute_hidden;
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/* Returns the FILE * that can be used to write data to the
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buffer. */
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static inline FILE *
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__printf_buffer_as_file_get (struct __printf_buffer_as_file *file)
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{
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return &file->stream;
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}
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/* Transfers all pending data from the FILE * to the underlying
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buffer. Returns true if there have been no errors. */
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bool __printf_buffer_as_file_terminate (struct __printf_buffer_as_file *)
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attribute_hidden;
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/* Wide variant follows. */
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struct __wprintf_buffer;
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struct __wprintf_buffer_as_file
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{
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/* Interface to libio. */
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FILE stream;
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const struct _IO_jump_t *vtable;
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struct _IO_wide_data wide_stream;
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/* Pointer to the underlying buffer. */
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struct __wprintf_buffer *next;
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};
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void __wprintf_buffer_as_file_init (struct __wprintf_buffer_as_file *fp,
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struct __wprintf_buffer *next)
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attribute_hidden;
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static inline FILE *
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__wprintf_buffer_as_file_get (struct __wprintf_buffer_as_file *file)
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{
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return &file->stream;
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}
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bool __wprintf_buffer_as_file_terminate (struct __wprintf_buffer_as_file *)
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attribute_hidden;
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#endif /* PRINTF_BUFFER_AS_FILE_H */
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