fftools/cmdutils: put stream specifier handling back into cmdutils

Stream specifiers were originally designed exclusively for CLI use and
were not intended to be public API. Handling them in avformat places
major restrictions on how they are used. E.g. if ffmpeg CLI wishes to
override some stream parameters, it has to change the demuxer fields
(since avformat_match_stream_specifier() does not have access to
anything else). However, such fields are supposed to be read-only for
the caller.

Furthermore having this code in avformat restricts extending the
specifier syntax. An example of such an extension will be added in
following commits.

fftools/cmdutils.c

@@ -980,10 +980,219 @@ FILE *get_preset_file(char *filename, size_t filename_size,
     return f;
 }
 
+/**
+ * Matches a stream specifier (but ignores requested index).
+ *
+ * @param indexptr set to point to the requested stream index if there is one
+ *
+ * @return <0 on error
+ *         0  if st is NOT a matching stream
+ *         >0 if st is a matching stream
+ */
+static int match_stream_specifier(const AVFormatContext *s, const AVStream *st,
+                                  const char *spec, const char **indexptr,
+                                  const AVStreamGroup **g, const AVProgram **p)
+{
+    int match = 1;                      /* Stores if the specifier matches so far. */
+    while (*spec) {
+        if (*spec <= '9' && *spec >= '0') { /* opt:index */
+            if (indexptr)
+                *indexptr = spec;
+            return match;
+        } else if (*spec == 'v' || *spec == 'a' || *spec == 's' || *spec == 'd' ||
+                   *spec == 't' || *spec == 'V') { /* opt:[vasdtV] */
+            enum AVMediaType type;
+            int nopic = 0;
+
+            switch (*spec++) {
+            case 'v': type = AVMEDIA_TYPE_VIDEO;      break;
+            case 'a': type = AVMEDIA_TYPE_AUDIO;      break;
+            case 's': type = AVMEDIA_TYPE_SUBTITLE;   break;
+            case 'd': type = AVMEDIA_TYPE_DATA;       break;
+            case 't': type = AVMEDIA_TYPE_ATTACHMENT; break;
+            case 'V': type = AVMEDIA_TYPE_VIDEO; nopic = 1; break;
+            default:  av_assert0(0);
+            }
+            if (*spec && *spec++ != ':')         /* If we are not at the end, then another specifier must follow. */
+                return AVERROR(EINVAL);
+
+            if (type != st->codecpar->codec_type)
+                match = 0;
+            if (nopic && (st->disposition & AV_DISPOSITION_ATTACHED_PIC))
+                match = 0;
+        } else if (*spec == 'g' && *(spec + 1) == ':') {
+            int64_t group_idx = -1, group_id = -1;
+            int found = 0;
+            char *endptr;
+            spec += 2;
+            if (*spec == '#' || (*spec == 'i' && *(spec + 1) == ':')) {
+                spec += 1 + (*spec == 'i');
+                group_id = strtol(spec, &endptr, 0);
+                if (spec == endptr || (*endptr && *endptr++ != ':'))
+                    return AVERROR(EINVAL);
+                spec = endptr;
+            } else {
+                group_idx = strtol(spec, &endptr, 0);
+                /* Disallow empty id and make sure that if we are not at the end, then another specifier must follow. */
+                if (spec == endptr || (*endptr && *endptr++ != ':'))
+                    return AVERROR(EINVAL);
+                spec = endptr;
+            }
+            if (match) {
+                if (group_id > 0) {
+                    for (unsigned i = 0; i < s->nb_stream_groups; i++) {
+                        if (group_id == s->stream_groups[i]->id) {
+                            group_idx = i;
+                            break;
+                        }
+                    }
+                }
+                if (group_idx < 0 || group_idx >= s->nb_stream_groups)
+                    return AVERROR(EINVAL);
+                for (unsigned j = 0; j < s->stream_groups[group_idx]->nb_streams; j++) {
+                    if (st->index == s->stream_groups[group_idx]->streams[j]->index) {
+                        found = 1;
+                        if (g)
+                            *g = s->stream_groups[group_idx];
+                        break;
+                    }
+                }
+            }
+            if (!found)
+                match = 0;
+        } else if (*spec == 'p' && *(spec + 1) == ':') {
+            int prog_id;
+            int found = 0;
+            char *endptr;
+            spec += 2;
+            prog_id = strtol(spec, &endptr, 0);
+            /* Disallow empty id and make sure that if we are not at the end, then another specifier must follow. */
+            if (spec == endptr || (*endptr && *endptr++ != ':'))
+                return AVERROR(EINVAL);
+            spec = endptr;
+            if (match) {
+                for (unsigned i = 0; i < s->nb_programs; i++) {
+                    if (s->programs[i]->id != prog_id)
+                        continue;
+
+                    for (unsigned j = 0; j < s->programs[i]->nb_stream_indexes; j++) {
+                        if (st->index == s->programs[i]->stream_index[j]) {
+                            found = 1;
+                            if (p)
+                                *p = s->programs[i];
+                            i = s->nb_programs;
+                            break;
+                        }
+                    }
+                }
+            }
+            if (!found)
+                match = 0;
+        } else if (*spec == '#' ||
+                   (*spec == 'i' && *(spec + 1) == ':')) {
+            int stream_id;
+            char *endptr;
+            spec += 1 + (*spec == 'i');
+            stream_id = strtol(spec, &endptr, 0);
+            if (spec == endptr || *endptr)                /* Disallow empty id and make sure we are at the end. */
+                return AVERROR(EINVAL);
+            return match && (stream_id == st->id);
+        } else if (*spec == 'm' && *(spec + 1) == ':') {
+            const AVDictionaryEntry *tag;
+            char *key, *val;
+            int ret;
+
+            if (match) {
+                spec += 2;
+                val = strchr(spec, ':');
+
+                key = val ? av_strndup(spec, val - spec) : av_strdup(spec);
+                if (!key)
+                    return AVERROR(ENOMEM);
+
+                tag = av_dict_get(st->metadata, key, NULL, 0);
+                if (tag) {
+                    if (!val || !strcmp(tag->value, val + 1))
+                        ret = 1;
+                    else
+                        ret = 0;
+                } else
+                    ret = 0;
+
+                av_freep(&key);
+            }
+            return match && ret;
+        } else if (*spec == 'u' && *(spec + 1) == '\0') {
+            const AVCodecParameters *par = st->codecpar;
+            int val;
+            switch (par->codec_type) {
+            case AVMEDIA_TYPE_AUDIO:
+                val = par->sample_rate && par->ch_layout.nb_channels;
+                if (par->format == AV_SAMPLE_FMT_NONE)
+                    return 0;
+                break;
+            case AVMEDIA_TYPE_VIDEO:
+                val = par->width && par->height;
+                if (par->format == AV_PIX_FMT_NONE)
+                    return 0;
+                break;
+            case AVMEDIA_TYPE_UNKNOWN:
+                val = 0;
+                break;
+            default:
+                val = 1;
+                break;
+            }
+            return match && (par->codec_id != AV_CODEC_ID_NONE && val != 0);
+        } else {
+            return AVERROR(EINVAL);
+        }
+    }
+
+    return match;
+}
+
 int check_stream_specifier(AVFormatContext *s, AVStream *st, const char *spec)
 {
-    int ret = avformat_match_stream_specifier(s, st, spec);
+    int ret, index;
+    char *endptr;
+    const char *indexptr = NULL;
+    const AVStreamGroup *g = NULL;
+    const AVProgram *p = NULL;
+    int nb_streams;
+
+    ret = match_stream_specifier(s, st, spec, &indexptr, &g, &p);
     if (ret < 0)
+        goto error;
+
+    if (!indexptr)
+        return ret;
+
+    index = strtol(indexptr, &endptr, 0);
+    if (*endptr) {                  /* We can't have anything after the requested index. */
+        ret = AVERROR(EINVAL);
+        goto error;
+    }
+
+    /* This is not really needed but saves us a loop for simple stream index specifiers. */
+    if (spec == indexptr)
+        return (index == st->index);
+
+    /* If we requested a matching stream index, we have to ensure st is that. */
+    nb_streams = g ? g->nb_streams : (p ? p->nb_stream_indexes : s->nb_streams);
+    for (int i = 0; i < nb_streams && index >= 0; i++) {
+        unsigned idx = g ? g->streams[i]->index : (p ? p->stream_index[i] : i);
+        const AVStream *candidate = s->streams[idx];
+        ret = match_stream_specifier(s, candidate, spec, NULL, NULL, NULL);
+        if (ret < 0)
+            goto error;
+        if (ret > 0 && index-- == 0 && st == candidate)
+            return 1;
+    }
+    return 0;
+
+error:
+    if (ret == AVERROR(EINVAL))
         av_log(s, AV_LOG_ERROR, "Invalid stream specifier: %s.\n", spec);
     return ret;
 }