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author | Florian Weimer <fweimer@redhat.com> | 2022-12-19 18:56:54 +0100 |
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committer | Florian Weimer <fweimer@redhat.com> | 2022-12-19 18:56:54 +0100 |
commit | 659fe9fdd14b0772f4e9722b751b9b010665e053 (patch) | |
tree | 3098a69345fbd3474154bbba45e8f21de449f266 /stdio-common/wprintf_buffer_as_file.c | |
parent | ffde06c915d10c0717a0980508ccb28506c6ec63 (diff) | |
download | glibc-659fe9fdd14b0772f4e9722b751b9b010665e053.tar.gz glibc-659fe9fdd14b0772f4e9722b751b9b010665e053.tar.xz glibc-659fe9fdd14b0772f4e9722b751b9b010665e053.zip |
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>
Diffstat (limited to 'stdio-common/wprintf_buffer_as_file.c')
-rw-r--r-- | stdio-common/wprintf_buffer_as_file.c | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/stdio-common/wprintf_buffer_as_file.c b/stdio-common/wprintf_buffer_as_file.c new file mode 100644 index 0000000000..cd48a7d42a --- /dev/null +++ b/stdio-common/wprintf_buffer_as_file.c @@ -0,0 +1,153 @@ +/* FILE * interface to a struct __wprintf_buffer. Wide version. + Copyright (C) 2022 Free Software Foundation, Inc. + 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/>. */ + +#include <printf_buffer_as_file.h> + +#include <assert.h> +#include <printf_buffer.h> + +/* Commit the data directly written through the stdio stream. */ +static void +__wprintf_buffer_as_file_commit (struct __wprintf_buffer_as_file *file) +{ + /* Check that the write pointers in the file stream are consistent + with the next buffer. */ + assert (file->wide_stream._IO_write_ptr >= file->next->write_ptr); + assert (file->wide_stream._IO_write_ptr <= file->next->write_end); + assert (file->wide_stream._IO_write_base == file->next->write_base); + assert (file->wide_stream._IO_write_end == file->next->write_end); + + file->next->write_ptr = file->wide_stream._IO_write_ptr; +} + +/* Pointer the FILE * write buffer into the active struct __wprintf_buffer + area. */ +static void +__wprintf_buffer_as_file_switch_to_buffer (struct __wprintf_buffer_as_file *file) +{ + file->wide_stream._IO_write_base = file->next->write_base; + file->wide_stream._IO_write_ptr = file->next->write_ptr; + file->wide_stream._IO_write_end = file->next->write_end; +} + +/* Only a small subset of the vtable functions is implemented here, + following _IO_obstack_jumps. */ + +static wint_t +__wprintf_buffer_as_file_overflow (FILE *fp, int ch) +{ + struct __wprintf_buffer_as_file *file + = (struct __wprintf_buffer_as_file *) fp; + + __wprintf_buffer_as_file_commit (file); + + /* EOF means only a flush is requested. */ + if (ch != WEOF) + __wprintf_buffer_putc (file->next, ch); + else + ch = 0; + + /* Ensure that flushing actually produces room. */ + if (!__wprintf_buffer_has_failed (file->next) + && file->next->write_ptr == file->next->write_end) + __wprintf_buffer_flush (file->next); + + __wprintf_buffer_as_file_switch_to_buffer (file); + + if (!__wprintf_buffer_has_failed (file->next)) + return (unsigned char) ch; + else + return WEOF; +} + +static size_t +__wprintf_buffer_as_file_xsputn (FILE *fp, const void *buf, size_t len) +{ + struct __wprintf_buffer_as_file *file + = (struct __wprintf_buffer_as_file *) fp; + + __wprintf_buffer_as_file_commit (file); + + /* Copy the data. */ + __wprintf_buffer_write (file->next, buf, len); + + __wprintf_buffer_as_file_switch_to_buffer (file); + + if (!__wprintf_buffer_has_failed (file->next)) + return len; + else + /* We may actually have written something. But the stream is + corrupted in this case anyway, so try not to divine the write + count here. */ + return 0; +} + +static const struct _IO_jump_t _IO_wprintf_buffer_as_file_jumps libio_vtable = +{ + JUMP_INIT_DUMMY, + JUMP_INIT(finish, NULL), + JUMP_INIT(overflow, (_IO_overflow_t) __wprintf_buffer_as_file_overflow), + JUMP_INIT(underflow, NULL), + JUMP_INIT(uflow, NULL), + JUMP_INIT(pbackfail, NULL), + JUMP_INIT(xsputn, __wprintf_buffer_as_file_xsputn), + JUMP_INIT(xsgetn, NULL), + JUMP_INIT(seekoff, NULL), + JUMP_INIT(seekpos, NULL), + JUMP_INIT(setbuf, NULL), + JUMP_INIT(sync, NULL), + JUMP_INIT(doallocate, NULL), + JUMP_INIT(read, NULL), + JUMP_INIT(write, NULL), + JUMP_INIT(seek, NULL), + JUMP_INIT(close, NULL), + JUMP_INIT(stat, NULL), + JUMP_INIT(showmanyc, NULL), + JUMP_INIT(imbue, NULL) +}; + +void +__wprintf_buffer_as_file_init (struct __wprintf_buffer_as_file *file, + struct __wprintf_buffer *next) +{ + file->stream._lock = NULL; + _IO_no_init (&file->stream, _IO_USER_LOCK, 0, &file->wide_stream, + &_IO_wprintf_buffer_as_file_jumps); + _IO_fwide (&file->stream, 1); + + /* Set up the write buffer from the next buffer. */ + file->next = next; + __wprintf_buffer_as_file_switch_to_buffer (file); + + /* Mark the read area as inactive, by making all pointers equal. */ + file->stream._IO_read_base = file->stream._IO_write_base; + file->stream._IO_read_ptr = file->stream._IO_write_base; + file->stream._IO_read_end = file->stream._IO_write_base; +} + +bool +__wprintf_buffer_as_file_terminate (struct __wprintf_buffer_as_file *file) +{ + if (file->stream._flags & _IO_ERR_SEEN) + return false; + else + { + __wprintf_buffer_as_file_commit (file); + return true; + } +} |