2 * Copyright (c) 2012 Nicolas George
4 * This file is part of FFmpeg.
6 * FFmpeg is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
11 * FFmpeg is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with FFmpeg; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 #ifndef AVUTIL_BPRINT_H
22 #define AVUTIL_BPRINT_H
24 #include "attributes.h"
27 * Define a structure with extra padding to a fixed size
28 * This helps ensuring binary compatibility with future versions.
30 #define FF_PAD_STRUCTURE(size, ...) \
32 char reserved_padding[size - sizeof(struct { __VA_ARGS__ })];
35 * Buffer to print data progressively
37 * The string buffer grows as necessary and is always 0-terminated.
38 * The content of the string is never accessed, and thus is
39 * encoding-agnostic and can even hold binary data.
41 * Small buffers are kept in the structure itself, and thus require no
42 * memory allocation at all (unless the contents of the buffer is needed
43 * after the structure goes out of scope). This is almost as lightweight as
44 * declaring a local "char buf[512]".
46 * The length of the string can go beyond the allocated size: the buffer is
47 * then truncated, but the functions still keep account of the actual total
50 * In other words, buf->len can be greater than buf->size and records the
51 * total length of what would have been to the buffer if there had been
54 * Append operations do not need to be tested for failure: if a memory
55 * allocation fails, data stop being appended to the buffer, but the length
56 * is still updated. This situation can be tested with
57 * av_bprint_is_complete().
59 * The size_max field determines several possible behaviours:
61 * size_max = -1 (= UINT_MAX) or any large value will let the buffer be
62 * reallocated as necessary, with an amortized linear cost.
64 * size_max = 0 prevents writing anything to the buffer: only the total
65 * length is computed. The write operations can then possibly be repeated in
66 * a buffer with exactly the necessary size
67 * (using size_init = size_max = len + 1).
69 * size_max = 1 is automatically replaced by the exact size available in the
70 * structure itself, thus ensuring no dynamic memory allocation. The
71 * internal buffer is large enough to hold a reasonable paragraph of text,
72 * such as the current paragraph.
74 typedef struct AVBPrint {
75 FF_PAD_STRUCTURE(1024,
76 char *str; /** string so far */
77 unsigned len; /** length so far */
78 unsigned size; /** allocated memory */
79 unsigned size_max; /** maximum allocated memory */
80 char reserved_internal_buffer[1];
85 * Convenience macros for special values for av_bprint_init() size_max
88 #define AV_BPRINT_SIZE_UNLIMITED ((unsigned)-1)
89 #define AV_BPRINT_SIZE_AUTOMATIC 1
90 #define AV_BPRINT_SIZE_COUNT_ONLY 0
93 * Init a print buffer.
95 * @param buf buffer to init
96 * @param size_init initial size (including the final 0)
97 * @param size_max maximum size;
98 * 0 means do not write anything, just count the length;
99 * 1 is replaced by the maximum value for automatic storage;
100 * any large value means that the internal buffer will be
101 * reallocated as needed up to that limit; -1 is converted to
102 * UINT_MAX, the largest limit possible.
103 * Check also AV_BPRINT_SIZE_* macros.
105 void av_bprint_init(AVBPrint *buf, unsigned size_init, unsigned size_max);
108 * Init a print buffer using a pre-existing buffer.
110 * The buffer will not be reallocated.
112 * @param buf buffer structure to init
113 * @param buffer byte buffer to use for the string data
114 * @param size size of buffer
116 void av_bprint_init_for_buffer(AVBPrint *buf, char *buffer, unsigned size);
119 * Append a formatted string to a print buffer.
121 void av_bprintf(AVBPrint *buf, const char *fmt, ...) av_printf_format(2, 3);
124 * Append char c n times to a print buffer.
126 void av_bprint_chars(AVBPrint *buf, char c, unsigned n);
130 * Append a formatted date and time to a print buffer.
132 * param buf bprint buffer to use
133 * param fmt date and time format string, see strftime()
134 * param tm broken-down time structure to translate
136 * @note due to poor design of the standard strftime function, it may
137 * produce poor results if the format string expands to a very long text and
138 * the bprint buffer is near the limit stated by the size_max option.
140 void av_bprint_strftime(AVBPrint *buf, const char *fmt, const struct tm *tm);
143 * Allocate bytes in the buffer for external use.
145 * @param[in] buf buffer structure
146 * @param[in] size required size
147 * @param[out] mem pointer to the memory area
148 * @param[out] actual_size size of the memory area after allocation;
149 * can be larger or smaller than size
151 void av_bprint_get_buffer(AVBPrint *buf, unsigned size,
152 unsigned char **mem, unsigned *actual_size);
155 * Reset the string to "" but keep internal allocated data.
157 void av_bprint_clear(AVBPrint *buf);
160 * Test if the print buffer is complete (not truncated).
162 * It may have been truncated due to a memory allocation failure
163 * or the size_max limit (compare size and size_max if necessary).
165 static inline int av_bprint_is_complete(AVBPrint *buf)
167 return buf->len < buf->size;
171 * Finalize a print buffer.
173 * The print buffer can no longer be used afterwards,
174 * but the len and size fields are still valid.
176 * @arg[out] ret_str if not NULL, used to return a permanent copy of the
177 * buffer contents, or NULL if memory allocation fails;
178 * if NULL, the buffer is discarded and freed
179 * @return 0 for success or error code (probably AVERROR(ENOMEM))
181 int av_bprint_finalize(AVBPrint *buf, char **ret_str);
183 #endif /* AVUTIL_BPRINT_H */