cmdutils: add a commandline pre-parser.

It splits the commandline into a more convenient internal representation
for further parsing.

This will allow e.g.
- processing global options first independently of their location on the
  commandline, eliminating ugly hacks for processing e.g. cpuflags
  first
- better options validation and error reporting. It is now possible for
  the parser to know that it's applying an input option to an output
  file or vice versa and act accordingly.

cmdutils.c

@@ -340,6 +340,29 @@ void parse_options(void *optctx, int argc, char **argv, const OptionDef *options
     }
 }
 
+int parse_optgroup(void *optctx, OptionGroup *g)
+{
+    int i, ret;
+
+    av_log(NULL, AV_LOG_DEBUG, "Parsing a group of options: %s %s.\n",
+           g->group_def->name, g->arg);
+
+    for (i = 0; i < g->nb_opts; i++) {
+        Option *o = &g->opts[i];
+
+        av_log(NULL, AV_LOG_DEBUG, "Applying option %s (%s) with argument %s.\n",
+               o->key, o->opt->help, o->val);
+
+        ret = write_option(optctx, o->opt, o->key, o->val);
+        if (ret < 0)
+            return ret;
+    }
+
+    av_log(NULL, AV_LOG_DEBUG, "Successfully parsed a group of options.\n");
+
+    return 0;
+}
+
 int locate_option(int argc, char **argv, const OptionDef *options,
                   const char *optname)
 {
@@ -416,6 +439,224 @@ int opt_default(void *optctx, const char *opt, const char *arg)
     return AVERROR_OPTION_NOT_FOUND;
 }
 
+/*
+ * Check whether given option is a group separator.
+ *
+ * @return index of the group definition that matched or -1 if none
+ */
+static int match_group_separator(const OptionGroupDef *groups, const char *opt)
+{
+    const OptionGroupDef *p = groups;
+
+    while (p->name) {
+        if (p->sep && !strcmp(p->sep, opt))
+            return p - groups;
+        p++;
+    }
+
+    return -1;
+}
+
+/*
+ * Finish parsing an option group.
+ *
+ * @param group_idx which group definition should this group belong to
+ * @param arg argument of the group delimiting option
+ */
+static void finish_group(OptionParseContext *octx, int group_idx,
+                         const char *arg)
+{
+    OptionGroupList *l = &octx->groups[group_idx];
+    OptionGroup *g;
+
+    GROW_ARRAY(l->groups, l->nb_groups);
+    g = &l->groups[l->nb_groups - 1];
+
+    *g             = octx->cur_group;
+    g->arg         = arg;
+    g->group_def   = l->group_def;
+#if CONFIG_SWSCALE
+    g->sws_opts    = sws_opts;
+#endif
+    g->codec_opts  = codec_opts;
+    g->format_opts = format_opts;
+
+    codec_opts  = NULL;
+    format_opts = NULL;
+#if CONFIG_SWSCALE
+    sws_opts    = NULL;
+#endif
+    init_opts();
+
+    memset(&octx->cur_group, 0, sizeof(octx->cur_group));
+}
+
+/*
+ * Add an option instance to currently parsed group.
+ */
+static void add_opt(OptionParseContext *octx, const OptionDef *opt,
+                    const char *key, const char *val)
+{
+    int global = !(opt->flags & (OPT_PERFILE | OPT_SPEC | OPT_OFFSET));
+    OptionGroup *g = global ? &octx->global_opts : &octx->cur_group;
+
+    GROW_ARRAY(g->opts, g->nb_opts);
+    g->opts[g->nb_opts - 1].opt = opt;
+    g->opts[g->nb_opts - 1].key = key;
+    g->opts[g->nb_opts - 1].val = val;
+}
+
+static void init_parse_context(OptionParseContext *octx,
+                               const OptionGroupDef *groups)
+{
+    static const OptionGroupDef global_group = { "global" };
+    const OptionGroupDef *g = groups;
+    int i;
+
+    memset(octx, 0, sizeof(*octx));
+
+    while (g->name)
+        g++;
+    octx->nb_groups = g - groups;
+    octx->groups    = av_mallocz(sizeof(*octx->groups) * octx->nb_groups);
+    if (!octx->groups)
+        exit(1);
+
+    for (i = 0; i < octx->nb_groups; i++)
+        octx->groups[i].group_def = &groups[i];
+
+    octx->global_opts.group_def = &global_group;
+    octx->global_opts.arg       = "";
+
+    init_opts();
+}
+
+void uninit_parse_context(OptionParseContext *octx)
+{
+    int i, j;
+
+    for (i = 0; i < octx->nb_groups; i++) {
+        OptionGroupList *l = &octx->groups[i];
+
+        for (j = 0; j < l->nb_groups; j++) {
+            av_freep(&l->groups[j].opts);
+            av_dict_free(&l->groups[j].codec_opts);
+            av_dict_free(&l->groups[j].format_opts);
+#if CONFIG_SWSCALE
+            sws_freeContext(l->groups[j].sws_opts);
+#endif
+        }
+        av_freep(&l->groups);
+    }
+    av_freep(&octx->groups);
+
+    av_freep(&octx->cur_group.opts);
+    av_freep(&octx->global_opts.opts);
+
+    uninit_opts();
+}
+
+int split_commandline(OptionParseContext *octx, int argc, char *argv[],
+                      const OptionDef *options,
+                      const OptionGroupDef *groups)
+{
+    int optindex = 1;
+
+    /* perform system-dependent conversions for arguments list */
+    prepare_app_arguments(&argc, &argv);
+
+    init_parse_context(octx, groups);
+    av_log(NULL, AV_LOG_DEBUG, "Splitting the commandline.\n");
+
+    while (optindex < argc) {
+        const char *opt = argv[optindex++], *arg;
+        const OptionDef *po;
+        int ret;
+
+        av_log(NULL, AV_LOG_DEBUG, "Reading option '%s' ...", opt);
+
+        /* unnamed group separators, e.g. output filename */
+        if (opt[0] != '-' || !opt[1]) {
+            finish_group(octx, 0, opt);
+            av_log(NULL, AV_LOG_DEBUG, " matched as %s.\n", groups[0].name);
+            continue;
+        }
+        opt++;
+
+#define GET_ARG(arg)                                                           \
+do {                                                                           \
+    arg = argv[optindex++];                                                    \
+    if (!arg) {                                                                \
+        av_log(NULL, AV_LOG_ERROR, "Missing argument for option '%s'.\n", opt);\
+        return AVERROR(EINVAL);                                                \
+    }                                                                          \
+} while (0)
+
+        /* named group separators, e.g. -i */
+        if ((ret = match_group_separator(groups, opt)) >= 0) {
+            GET_ARG(arg);
+            finish_group(octx, ret, arg);
+            av_log(NULL, AV_LOG_DEBUG, " matched as %s with argument '%s'.\n",
+                   groups[ret].name, arg);
+            continue;
+        }
+
+        /* normal options */
+        po = find_option(options, opt);
+        if (po->name) {
+            if (po->flags & OPT_EXIT) {
+                /* optional argument, e.g. -h */
+                arg = argv[optindex++];
+            } else if (po->flags & HAS_ARG) {
+                GET_ARG(arg);
+            } else {
+                arg = "1";
+            }
+
+            add_opt(octx, po, opt, arg);
+            av_log(NULL, AV_LOG_DEBUG, " matched as option '%s' (%s) with "
+                   "argument '%s'.\n", po->name, po->help, arg);
+            continue;
+        }
+
+        /* AVOptions */
+        if (argv[optindex]) {
+            ret = opt_default(NULL, opt, argv[optindex]);
+            if (ret >= 0) {
+                av_log(NULL, AV_LOG_DEBUG, " matched as AVOption '%s' with "
+                       "argument '%s'.\n", opt, argv[optindex]);
+                optindex++;
+                continue;
+            } else if (ret != AVERROR_OPTION_NOT_FOUND) {
+                av_log(NULL, AV_LOG_ERROR, "Error parsing option '%s' "
+                       "with argument '%s'.\n", opt, argv[optindex]);
+                return ret;
+            }
+        }
+
+        /* boolean -nofoo options */
+        if (opt[0] == 'n' && opt[1] == 'o' &&
+            (po = find_option(options, opt + 2)) &&
+            po->name && po->flags & OPT_BOOL) {
+            add_opt(octx, po, opt, "0");
+            av_log(NULL, AV_LOG_DEBUG, " matched as option '%s' (%s) with "
+                   "argument 0.\n", po->name, po->help);
+            continue;
+        }
+
+        av_log(NULL, AV_LOG_ERROR, "Unrecognized option '%s'.\n", opt);
+        return AVERROR_OPTION_NOT_FOUND;
+    }
+
+    if (octx->cur_group.nb_opts || codec_opts || format_opts)
+        av_log(NULL, AV_LOG_WARNING, "Trailing options were found on the "
+               "commandline.\n");
+
+    av_log(NULL, AV_LOG_DEBUG, "Finished splitting the commandline.\n");
+
+    return 0;
+}
+
 int opt_loglevel(void *optctx, const char *opt, const char *arg)
 {
     const struct { const char *name; int level; } log_levels[] = {

cmdutils.h

@@ -205,6 +205,94 @@ void parse_options(void *optctx, int argc, char **argv, const OptionDef *options
 int parse_option(void *optctx, const char *opt, const char *arg,
                  const OptionDef *options);
 
+/**
+ * An option extracted from the commandline.
+ * Cannot use AVDictionary because of options like -map which can be
+ * used multiple times.
+ */
+typedef struct Option {
+    const OptionDef  *opt;
+    const char       *key;
+    const char       *val;
+} Option;
+
+typedef struct OptionGroupDef {
+    /**< group name */
+    const char *name;
+    /**
+     * Option to be used as group separator. Can be NULL for groups which
+     * are terminated by a non-option argument (e.g. avconv output files)
+     */
+    const char *sep;
+} OptionGroupDef;
+
+typedef struct OptionGroup {
+    const OptionGroupDef *group_def;
+    const char *arg;
+
+    Option *opts;
+    int  nb_opts;
+
+    AVDictionary *codec_opts;
+    AVDictionary *format_opts;
+    struct SwsContext *sws_opts;
+} OptionGroup;
+
+/**
+ * A list of option groups that all have the same group type
+ * (e.g. input files or output files)
+ */
+typedef struct OptionGroupList {
+    const OptionGroupDef *group_def;
+
+    OptionGroup *groups;
+    int       nb_groups;
+} OptionGroupList;
+
+typedef struct OptionParseContext {
+    OptionGroup global_opts;
+
+    OptionGroupList *groups;
+    int           nb_groups;
+
+    /* parsing state */
+    OptionGroup cur_group;
+} OptionParseContext;
+
+/**
+ * Parse an options group and write results into optctx.
+ *
+ * @param optctx an app-specific options context. NULL for global options group
+ */
+int parse_optgroup(void *optctx, OptionGroup *g);
+
+/**
+ * Split the commandline into an intermediate form convenient for further
+ * processing.
+ *
+ * The commandline is assumed to be composed of options which either belong to a
+ * group (those with OPT_SPEC, OPT_OFFSET or OPT_PERFILE) or are global
+ * (everything else).
+ *
+ * A group (defined by an OptionGroupDef struct) is a sequence of options
+ * terminated by either a group separator option (e.g. -i) or a parameter that
+ * is not an option (doesn't start with -). A group without a separator option
+ * must always be first in the supplied groups list.
+ *
+ * All options within the same group are stored in one OptionGroup struct in an
+ * OptionGroupList, all groups with the same group definition are stored in one
+ * OptionGroupList in OptionParseContext.groups. The order of group lists is the
+ * same as the order of group definitions.
+ */
+int split_commandline(OptionParseContext *octx, int argc, char *argv[],
+                      const OptionDef *options,
+                      const OptionGroupDef *groups);
+
+/**
+ * Free all allocated memory in an OptionParseContext.
+ */
+void uninit_parse_context(OptionParseContext *octx);
+
 /**
  * Find the '-loglevel' option in the command line args and apply it.
  */