/* * MPEG-DASH ISO BMFF segmenter * Copyright (c) 2014 Martin Storsjo * * This file is part of FFmpeg. * * FFmpeg 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. * * FFmpeg 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 FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ #include "config.h"#if HAVE_UNISTD_H#include <unistd.h>#endif #include "libavutil/avassert.h"#include "libavutil/avstring.h"#include "libavutil/intreadwrite.h"#include "libavutil/mathematics.h"#include "libavutil/opt.h"#include "libavutil/rational.h"#include "libavutil/time_internal.h" #include "avc.h"#include "avformat.h"#include "avio_internal.h"#include "internal.h"#include "isom.h"#include "os_support.h"#include "url.h"#include "dash.h" static DASHTmplId dash_read_tmpl_id(const char *identifier, char *format_tag,                                    size_t format_tag_size, const char **ptr) {    const char *next_ptr;    DASHTmplId id_type = DASH_TMPL_ID_UNDEFINED;     if (av_strstart(identifier, "$$", &next_ptr)) {        id_type = DASH_TMPL_ID_ESCAPE;        *ptr = next_ptr;    } else if (av_strstart(identifier, "$RepresentationID$", &next_ptr)) {        id_type = DASH_TMPL_ID_REP_ID;        // default to basic format, as $RepresentationID$ identifiers        // are not allowed to have custom format-tags.        av_strlcpy(format_tag, "%d", format_tag_size);        *ptr = next_ptr;    } else { // the following identifiers may have an explicit format_tag        if (av_strstart(identifier, "$Number", &next_ptr))            id_type = DASH_TMPL_ID_NUMBER;        else if (av_strstart(identifier, "$Bandwidth", &next_ptr))            id_type = DASH_TMPL_ID_BANDWIDTH;        else if (av_strstart(identifier, "$Time", &next_ptr))            id_type = DASH_TMPL_ID_TIME;        else            id_type = DASH_TMPL_ID_UNDEFINED;         // next parse the dash format-tag and generate a c-string format tag        // (next_ptr now points at the first '%' at the beginning of the format-tag)        if (id_type != DASH_TMPL_ID_UNDEFINED) {            const char *number_format = (id_type == DASH_TMPL_ID_TIME) ? PRId64 : "d";            if (next_ptr[0] == '$') { // no dash format-tag                snprintf(format_tag, format_tag_size, "%%%s", number_format);                *ptr = &next_ptr[1];            } else {                const char *width_ptr;                // only tolerate single-digit width-field (i.e. up to 9-digit width)                if (av_strstart(next_ptr, "%0", &width_ptr) &&                    av_isdigit(width_ptr[0]) &&                    av_strstart(&width_ptr[1], "d$", &next_ptr)) {                    // yes, we're using a format tag to build format_tag.                    snprintf(format_tag, format_tag_size, "%s%c%s", "%0", width_ptr[0], number_format);                    *ptr = next_ptr;                } else {                    av_log(NULL, AV_LOG_WARNING, "Failed to parse format-tag beginning with %s. Expected either a "                                                 "closing '$' character or a format-string like '%%0[width]d', "                                                 "where width must be a single digit\n", next_ptr);                    id_type = DASH_TMPL_ID_UNDEFINED;                }            }        }    }    return id_type;} void 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) {    int dst_pos = 0;    const char *t_cur = template;    while (dst_pos < buffer_size - 1 && *t_cur) {        char format_tag[7]; // May be "%d", "%0Xd", or "%0Xlld" (for $Time$), where X is in [0-9]        int n = 0;        DASHTmplId id_type;        const char *t_next = strchr(t_cur, '$'); // copy over everything up to the first '$' character        if (t_next) {            int num_copy_bytes = FFMIN(t_next - t_cur, buffer_size - dst_pos - 1);            av_strlcpy(&dst[dst_pos], t_cur, num_copy_bytes + 1);            // advance            dst_pos += num_copy_bytes;            t_cur = t_next;        } else { // no more DASH identifiers to substitute - just copy the rest over and break            av_strlcpy(&dst[dst_pos], t_cur, buffer_size - dst_pos);            break;        }         if (dst_pos >= buffer_size - 1 || !*t_cur)            break;         // t_cur is now pointing to a '$' character        id_type = dash_read_tmpl_id(t_cur, format_tag, sizeof(format_tag), &t_next);        switch (id_type) {        case DASH_TMPL_ID_ESCAPE:            av_strlcpy(&dst[dst_pos], "$", 2);            n = 1;            break;        case DASH_TMPL_ID_REP_ID:            n = snprintf(&dst[dst_pos], buffer_size - dst_pos, format_tag, rep_id);            break;        case DASH_TMPL_ID_NUMBER:            n = snprintf(&dst[dst_pos], buffer_size - dst_pos, format_tag, number);            break;        case DASH_TMPL_ID_BANDWIDTH:            n = snprintf(&dst[dst_pos], buffer_size - dst_pos, format_tag, bit_rate);            break;        case DASH_TMPL_ID_TIME:            n = snprintf(&dst[dst_pos], buffer_size - dst_pos, format_tag, time);            break;        case DASH_TMPL_ID_UNDEFINED:            // copy over one byte and advance            av_strlcpy(&dst[dst_pos], t_cur, 2);            n = 1;            t_next = &t_cur[1];            break;        }        // t_next points just past the processed identifier        // n is the number of bytes that were attempted to be written to dst        // (may have failed to write all because buffer_size).         // advance        dst_pos += FFMIN(n, buffer_size - dst_pos - 1);        t_cur = t_next;    }}