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comparison lib/libavutil/bprint.h @ 2134:992d2e6f907d

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preparation for libavcodec
author zipi
date Tue, 31 Dec 2013 14:52:14 +0000
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2133:e378232bfd36 2134:992d2e6f907d
1 /*
2 * Copyright (c) 2012 Nicolas George
3 *
4 * This file is part of FFmpeg.
5 *
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.
10 *
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.
15 *
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
19 */
20
21 #ifndef AVUTIL_BPRINT_H
22 #define AVUTIL_BPRINT_H
23
24 #include "attributes.h"
25 #include "avstring.h"
26
27 /**
28 * Define a structure with extra padding to a fixed size
29 * This helps ensuring binary compatibility with future versions.
30 */
31 #define FF_PAD_STRUCTURE(size, ...) \
32 __VA_ARGS__ \
33 char reserved_padding[size - sizeof(struct { __VA_ARGS__ })];
34
35 /**
36 * Buffer to print data progressively
37 *
38 * The string buffer grows as necessary and is always 0-terminated.
39 * The content of the string is never accessed, and thus is
40 * encoding-agnostic and can even hold binary data.
41 *
42 * Small buffers are kept in the structure itself, and thus require no
43 * memory allocation at all (unless the contents of the buffer is needed
44 * after the structure goes out of scope). This is almost as lightweight as
45 * declaring a local "char buf[512]".
46 *
47 * The length of the string can go beyond the allocated size: the buffer is
48 * then truncated, but the functions still keep account of the actual total
49 * length.
50 *
51 * In other words, buf->len can be greater than buf->size and records the
52 * total length of what would have been to the buffer if there had been
53 * enough memory.
54 *
55 * Append operations do not need to be tested for failure: if a memory
56 * allocation fails, data stop being appended to the buffer, but the length
57 * is still updated. This situation can be tested with
58 * av_bprint_is_complete().
59 *
60 * The size_max field determines several possible behaviours:
61 *
62 * size_max = -1 (= UINT_MAX) or any large value will let the buffer be
63 * reallocated as necessary, with an amortized linear cost.
64 *
65 * size_max = 0 prevents writing anything to the buffer: only the total
66 * length is computed. The write operations can then possibly be repeated in
67 * a buffer with exactly the necessary size
68 * (using size_init = size_max = len + 1).
69 *
70 * size_max = 1 is automatically replaced by the exact size available in the
71 * structure itself, thus ensuring no dynamic memory allocation. The
72 * internal buffer is large enough to hold a reasonable paragraph of text,
73 * such as the current paragraph.
74 */
75 typedef struct AVBPrint {
76 FF_PAD_STRUCTURE(1024,
77 char *str; /** string so far */
78 unsigned len; /** length so far */
79 unsigned size; /** allocated memory */
80 unsigned size_max; /** maximum allocated memory */
81 char reserved_internal_buffer[1];
82 )
83 } AVBPrint;
84
85 /**
86 * Convenience macros for special values for av_bprint_init() size_max
87 * parameter.
88 */
89 #define AV_BPRINT_SIZE_UNLIMITED ((unsigned)-1)
90 #define AV_BPRINT_SIZE_AUTOMATIC 1
91 #define AV_BPRINT_SIZE_COUNT_ONLY 0
92
93 /**
94 * Init a print buffer.
95 *
96 * @param buf buffer to init
97 * @param size_init initial size (including the final 0)
98 * @param size_max maximum size;
99 * 0 means do not write anything, just count the length;
100 * 1 is replaced by the maximum value for automatic storage;
101 * any large value means that the internal buffer will be
102 * reallocated as needed up to that limit; -1 is converted to
103 * UINT_MAX, the largest limit possible.
104 * Check also AV_BPRINT_SIZE_* macros.
105 */
106 void av_bprint_init(AVBPrint *buf, unsigned size_init, unsigned size_max);
107
108 /**
109 * Init a print buffer using a pre-existing buffer.
110 *
111 * The buffer will not be reallocated.
112 *
113 * @param buf buffer structure to init
114 * @param buffer byte buffer to use for the string data
115 * @param size size of buffer
116 */
117 void av_bprint_init_for_buffer(AVBPrint *buf, char *buffer, unsigned size);
118
119 /**
120 * Append a formatted string to a print buffer.
121 */
122 void av_bprintf(AVBPrint *buf, const char *fmt, ...) av_printf_format(2, 3);
123
124 /**
125 * Append char c n times to a print buffer.
126 */
127 void av_bprint_chars(AVBPrint *buf, char c, unsigned n);
128
129 struct tm;
130 /**
131 * Append a formatted date and time to a print buffer.
132 *
133 * param buf bprint buffer to use
134 * param fmt date and time format string, see strftime()
135 * param tm broken-down time structure to translate
136 *
137 * @note due to poor design of the standard strftime function, it may
138 * produce poor results if the format string expands to a very long text and
139 * the bprint buffer is near the limit stated by the size_max option.
140 */
141 void av_bprint_strftime(AVBPrint *buf, const char *fmt, const struct tm *tm);
142
143 /**
144 * Allocate bytes in the buffer for external use.
145 *
146 * @param[in] buf buffer structure
147 * @param[in] size required size
148 * @param[out] mem pointer to the memory area
149 * @param[out] actual_size size of the memory area after allocation;
150 * can be larger or smaller than size
151 */
152 void av_bprint_get_buffer(AVBPrint *buf, unsigned size,
153 unsigned char **mem, unsigned *actual_size);
154
155 /**
156 * Reset the string to "" but keep internal allocated data.
157 */
158 void av_bprint_clear(AVBPrint *buf);
159
160 /**
161 * Test if the print buffer is complete (not truncated).
162 *
163 * It may have been truncated due to a memory allocation failure
164 * or the size_max limit (compare size and size_max if necessary).
165 */
166 static inline int av_bprint_is_complete(AVBPrint *buf)
167 {
168 return buf->len < buf->size;
169 }
170
171 /**
172 * Finalize a print buffer.
173 *
174 * The print buffer can no longer be used afterwards,
175 * but the len and size fields are still valid.
176 *
177 * @arg[out] ret_str if not NULL, used to return a permanent copy of the
178 * buffer contents, or NULL if memory allocation fails;
179 * if NULL, the buffer is discarded and freed
180 * @return 0 for success or error code (probably AVERROR(ENOMEM))
181 */
182 int av_bprint_finalize(AVBPrint *buf, char **ret_str);
183
184 /**
185 * Escape the content in src and append it to dstbuf.
186 *
187 * @param dstbuf already inited destination bprint buffer
188 * @param src string containing the text to escape
189 * @param special_chars string containing the special characters which
190 * need to be escaped, can be NULL
191 * @param mode escape mode to employ, see AV_ESCAPE_MODE_* macros.
192 * Any unknown value for mode will be considered equivalent to
193 * AV_ESCAPE_MODE_BACKSLASH, but this behaviour can change without
194 * notice.
195 * @param flags flags which control how to escape, see AV_ESCAPE_FLAG_* macros
196 */
197 void av_bprint_escape(AVBPrint *dstbuf, const char *src, const char *special_chars,
198 enum AVEscapeMode mode, int flags);
199
200 #endif /* AVUTIL_BPRINT_H */