avformat/dash: move reused API to common file and header file

move from dashenc, move DASHTmplId and dash_fill_tmpl_params to
dash.c, they will be used by dash demuxer and dash muxer.

v2 fixed:
1. rename common file from dashcomm.* to dash.*
Suggested-by: Hendrik Leppkes <h.leppkes@gmail.com>

v3 fixed:
1. rename header file pre defined
2. add ff_ prefix for the internal API
Suggested-by: James Almer <jamrial@gmail.com>

Suggested-by: Timo Rothenpieler <timo@rothenpieler.org>
Reviewed-by: wm4 <nfxjfg@googlemail.com>
Signed-off-by: Steven Liu <lq@onvideo.cn>

1 files changed, 136 insertions, 0 deletions

diff --git a/libavformat/dash.c b/libavformat/dash.c
new file mode 100644
index 0000000..b0b1ed4
--- /dev/null
+++ b/libavformat/dash.c
@@ -0,0 +1,136 @@
+#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;
+    }
+}
+
+