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1 /*
2  * MPEG-DASH ISO BMFF segmenter
3  * Copyright (c) 2014 Martin Storsjo
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #include "config.h"
23 #if HAVE_UNISTD_H
24 #include <unistd.h>
25 #endif
26 
27 #include "libavutil/avstring.h"
28 #include "libavutil/intreadwrite.h"
29 #include "libavutil/mathematics.h"
30 #include "libavutil/opt.h"
31 #include "libavutil/rational.h"
32 #include "libavutil/time_internal.h"
33 
34 #include "avc.h"
35 #include "avformat.h"
36 #include "avio_internal.h"
37 #include "internal.h"
38 #include "isom.h"
39 #include "os_support.h"
40 #include "url.h"
41 #include "dash.h"
42 
dash_read_tmpl_id(const char * identifier,char * format_tag,size_t format_tag_size,const char ** ptr)43 static DASHTmplId dash_read_tmpl_id(const char *identifier, char *format_tag,
44                                     size_t format_tag_size, const char **ptr) {
45     const char *next_ptr;
46     DASHTmplId id_type = DASH_TMPL_ID_UNDEFINED;
47 
48     if (av_strstart(identifier, "$$", &next_ptr)) {
49         id_type = DASH_TMPL_ID_ESCAPE;
50         *ptr = next_ptr;
51     } else if (av_strstart(identifier, "$RepresentationID$", &next_ptr)) {
52         id_type = DASH_TMPL_ID_REP_ID;
53         // default to basic format, as $RepresentationID$ identifiers
54         // are not allowed to have custom format-tags.
55         av_strlcpy(format_tag, "%d", format_tag_size);
56         *ptr = next_ptr;
57     } else { // the following identifiers may have an explicit format_tag
58         if (av_strstart(identifier, "$Number", &next_ptr))
59             id_type = DASH_TMPL_ID_NUMBER;
60         else if (av_strstart(identifier, "$Bandwidth", &next_ptr))
61             id_type = DASH_TMPL_ID_BANDWIDTH;
62         else if (av_strstart(identifier, "$Time", &next_ptr))
63             id_type = DASH_TMPL_ID_TIME;
64         else
65             id_type = DASH_TMPL_ID_UNDEFINED;
66 
67         // next parse the dash format-tag and generate a c-string format tag
68         // (next_ptr now points at the first '%' at the beginning of the format-tag)
69         if (id_type != DASH_TMPL_ID_UNDEFINED) {
70             const char *number_format = (id_type == DASH_TMPL_ID_TIME) ? PRId64 : "d";
71             if (next_ptr[0] == '$') { // no dash format-tag
72                 snprintf(format_tag, format_tag_size, "%%%s", number_format);
73                 *ptr = &next_ptr[1];
74             } else {
75                 const char *width_ptr;
76                 // only tolerate single-digit width-field (i.e. up to 9-digit width)
77                 if (av_strstart(next_ptr, "%0", &width_ptr) &&
78                     av_isdigit(width_ptr[0]) &&
79                     av_strstart(&width_ptr[1], "d$", &next_ptr)) {
80                     // yes, we're using a format tag to build format_tag.
81                     snprintf(format_tag, format_tag_size, "%s%c%s", "%0", width_ptr[0], number_format);
82                     *ptr = next_ptr;
83                 } else {
84                     av_log(NULL, AV_LOG_WARNING, "Failed to parse format-tag beginning with %s. Expected either a "
85                                                  "closing '$' character or a format-string like '%%0[width]d', "
86                                                  "where width must be a single digit\n", next_ptr);
87                     id_type = DASH_TMPL_ID_UNDEFINED;
88                 }
89             }
90         }
91     }
92     return id_type;
93 }
94 
ff_dash_fill_tmpl_params(char * dst,size_t buffer_size,const char * template,int rep_id,int number,int bit_rate,int64_t time)95 void ff_dash_fill_tmpl_params(char *dst, size_t buffer_size,
96                                   const char *template, int rep_id,
97                                   int number, int bit_rate,
98                                   int64_t time) {
99     int dst_pos = 0;
100     const char *t_cur = template;
101     while (dst_pos < buffer_size - 1 && *t_cur) {
102         char format_tag[7]; // May be "%d", "%0Xd", or "%0Xlld" (for $Time$), where X is in [0-9]
103         int n = 0;
104         DASHTmplId id_type;
105         const char *t_next = strchr(t_cur, '$'); // copy over everything up to the first '$' character
106         if (t_next) {
107             int num_copy_bytes = FFMIN(t_next - t_cur, buffer_size - dst_pos - 1);
108             av_strlcpy(&dst[dst_pos], t_cur, num_copy_bytes + 1);
109             // advance
110             dst_pos += num_copy_bytes;
111             t_cur = t_next;
112         } else { // no more DASH identifiers to substitute - just copy the rest over and break
113             av_strlcpy(&dst[dst_pos], t_cur, buffer_size - dst_pos);
114             break;
115         }
116 
117         if (dst_pos >= buffer_size - 1 || !*t_cur)
118             break;
119 
120         // t_cur is now pointing to a '$' character
121         id_type = dash_read_tmpl_id(t_cur, format_tag, sizeof(format_tag), &t_next);
122         switch (id_type) {
123         case DASH_TMPL_ID_ESCAPE:
124             av_strlcpy(&dst[dst_pos], "$", 2);
125             n = 1;
126             break;
127         case DASH_TMPL_ID_REP_ID:
128             n = snprintf(&dst[dst_pos], buffer_size - dst_pos, format_tag, rep_id);
129             break;
130         case DASH_TMPL_ID_NUMBER:
131             n = snprintf(&dst[dst_pos], buffer_size - dst_pos, format_tag, number);
132             break;
133         case DASH_TMPL_ID_BANDWIDTH:
134             n = snprintf(&dst[dst_pos], buffer_size - dst_pos, format_tag, bit_rate);
135             break;
136         case DASH_TMPL_ID_TIME:
137             n = snprintf(&dst[dst_pos], buffer_size - dst_pos, format_tag, time);
138             break;
139         case DASH_TMPL_ID_UNDEFINED:
140             // copy over one byte and advance
141             av_strlcpy(&dst[dst_pos], t_cur, 2);
142             n = 1;
143             t_next = &t_cur[1];
144             break;
145         }
146         // t_next points just past the processed identifier
147         // n is the number of bytes that were attempted to be written to dst
148         // (may have failed to write all because buffer_size).
149 
150         // advance
151         dst_pos += FFMIN(n, buffer_size - dst_pos - 1);
152         t_cur = t_next;
153     }
154 }
155 
156 
157