[FFmpeg-devel,v3] avformat: add a concat protocol that takes a line break delimited list of resources

diff --git a/doc/protocols.texi b/doc/protocols.texi
index ccdfb6e439..726e5f1c44 100644
--- a/doc/protocols.texi
+++ b/doc/protocols.texi
@@ -215,6 +215,38 @@  ffplay concat:split1.mpeg\|split2.mpeg\|split3.mpeg
 Note that you may need to escape the character "|" which is special for
 many shells.
 
+@section concatf
+
+Physical concatenation protocol using a line break delimited list of
+resources.
+
+Read and seek from many resources in sequence as if they were
+a unique resource.
+
+A URL accepted by this protocol has the syntax:
+@example
+concatf:@var{URL}
+@end example
+
+where @var{URL} is the url containing a line break delimited list of
+resources to be concatenated, each one possibly specifying a distinct
+protocol. Special characters must be escaped with backslash or single
+quotes. See @ref{quoting_and_escaping,,the "Quoting and escaping"
+section in the ffmpeg-utils(1) manual,ffmpeg-utils}.
+
+For example to read a sequence of files @file{split1.mpeg},
+@file{split2.mpeg}, @file{split3.mpeg} listed in separate lines within
+a file @file{split.txt} with @command{ffplay} use the command:
+@example
+ffplay concatf:split.txt
+@end example
+Where @file{split.txt} contains the lines:
+@example
+split1.mpeg
+split2.mpeg
+split3.mpeg
+@end example
+
 @section crypto
 
 AES-encrypted stream reading protocol.
diff --git a/libavformat/Makefile b/libavformat/Makefile
index c9ef564523..caca95802a 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -616,6 +616,7 @@  OBJS-$(CONFIG_APPLEHTTP_PROTOCOL)        += hlsproto.o
 OBJS-$(CONFIG_BLURAY_PROTOCOL)           += bluray.o
 OBJS-$(CONFIG_CACHE_PROTOCOL)            += cache.o
 OBJS-$(CONFIG_CONCAT_PROTOCOL)           += concat.o
+OBJS-$(CONFIG_CONCATF_PROTOCOL)          += concat.o
 OBJS-$(CONFIG_CRYPTO_PROTOCOL)           += crypto.o
 OBJS-$(CONFIG_DATA_PROTOCOL)             += data_uri.o
 OBJS-$(CONFIG_FFRTMPCRYPT_PROTOCOL)      += rtmpcrypt.o rtmpdigest.o rtmpdh.o
diff --git a/libavformat/concat.c b/libavformat/concat.c
index 278afd997d..aec1f52d8e 100644
--- a/libavformat/concat.c
+++ b/libavformat/concat.c
@@ -22,9 +22,11 @@ 
  */
 
 #include "libavutil/avstring.h"
+#include "libavutil/bprint.h"
 #include "libavutil/mem.h"
 
 #include "avformat.h"
+#include "avio_internal.h"
 #include "url.h"
 
 #define AV_CAT_SEPARATOR "|"
@@ -56,6 +58,7 @@  static av_cold int concat_close(URLContext *h)
     return err < 0 ? -1 : 0;
 }
 
+#if CONFIG_CONCAT_PROTOCOL
 static av_cold int concat_open(URLContext *h, const char *uri, int flags)
 {
     char *node_uri = NULL;
@@ -124,6 +127,7 @@  static av_cold int concat_open(URLContext *h, const char *uri, int flags)
     data->total_size = total_size;
     return err;
 }
+#endif
 
 static int concat_read(URLContext *h, unsigned char *buf, int size)
 {
@@ -188,6 +192,7 @@  static int64_t concat_seek(URLContext *h, int64_t pos, int whence)
     return result;
 }
 
+#if CONFIG_CONCAT_PROTOCOL
 const URLProtocol ff_concat_protocol = {
     .name           = "concat",
     .url_open       = concat_open,
@@ -197,3 +202,107 @@  const URLProtocol ff_concat_protocol = {
     .priv_data_size = sizeof(struct concat_data),
     .default_whitelist = "concat,file,subfile",
 };
+#endif
+
+#if CONFIG_CONCATF_PROTOCOL
+static av_cold int concatf_open(URLContext *h, const char *uri, int flags)
+{
+    AVBPrint bp;
+    struct concat_data *data = h->priv_data;
+    AVIOContext *in = NULL;
+    const char *cursor;
+    int64_t total_size = 0;
+    unsigned int nodes_size = 0;
+    size_t i = 0;
+    int err;
+
+    if (!av_strstart(uri, "concatf:", &uri)) {
+        av_log(h, AV_LOG_ERROR, "URL %s lacks prefix\n", uri);
+        return AVERROR(EINVAL);
+    }
+
+    /* handle input */
+    if (!*uri)
+        return AVERROR(ENOENT);
+
+    err = ffio_open_whitelist(&in, uri, AVIO_FLAG_READ, &h->interrupt_callback,
+                              NULL, h->protocol_whitelist, h->protocol_blacklist);
+    if (err < 0)
+        return err;
+
+    av_bprint_init(&bp, 0, AV_BPRINT_SIZE_UNLIMITED);
+    err = avio_read_to_bprint(in, &bp, SIZE_MAX);
+    avio_closep(&in);
+    if (err < 0) {
+        av_bprint_finalize(&bp, NULL);
+        return err;
+    }
+
+    cursor = bp.str;
+    while (*cursor) {
+        struct concat_nodes *nodes;
+        URLContext *uc;
+        char *node_uri;
+        int64_t size;
+        size_t len = i;
+
+        node_uri = av_get_token(&cursor, "\r\n");
+        if (!node_uri) {
+            err = AVERROR(ENOMEM);
+            break;
+        }
+        cursor++;
+
+        if (++len == SIZE_MAX / sizeof(*nodes)) {
+            av_free(node_uri);
+            err = AVERROR(ENAMETOOLONG);
+            break;
+        }
+
+        /* creating URLContext */
+        err = ffurl_open_whitelist(&uc, node_uri, flags,
+                                   &h->interrupt_callback, NULL, h->protocol_whitelist, h->protocol_blacklist, h);
+        av_free(node_uri);
+        if (err < 0)
+            break;
+
+        /* creating size */
+        if ((size = ffurl_size(uc)) < 0) {
+            ffurl_close(uc);
+            err = AVERROR(ENOSYS);
+            break;
+        }
+
+        nodes = av_fast_realloc(data->nodes, &nodes_size, sizeof(*nodes) * len);
+        if (!nodes) {
+            ffurl_close(uc);
+            err = AVERROR(ENOMEM);
+            break;
+        }
+        data->nodes = nodes;
+
+        /* assembling */
+        data->nodes[i].uc   = uc;
+        data->nodes[i++].size = size;
+        total_size += size;
+    }
+    av_bprint_finalize(&bp, NULL);
+    data->length = i;
+
+    if (err < 0)
+        concat_close(h);
+
+    data->total_size = total_size;
+    return err;
+}
+
+const URLProtocol ff_concatf_protocol = {
+    .name           = "concatf",
+    .url_open       = concatf_open,
+    .url_read       = concat_read,
+    .url_seek       = concat_seek,
+    .url_close      = concat_close,
+    .priv_data_size = sizeof(struct concat_data),
+    .default_whitelist = "concatf,concat,file,subfile",
+};
+#endif
diff --git a/libavformat/protocols.c b/libavformat/protocols.c
index 4b6b1c8e98..7f08f151b6 100644
--- a/libavformat/protocols.c
+++ b/libavformat/protocols.c
@@ -27,6 +27,7 @@  extern const URLProtocol ff_async_protocol;
 extern const URLProtocol ff_bluray_protocol;
 extern const URLProtocol ff_cache_protocol;
 extern const URLProtocol ff_concat_protocol;
+extern const URLProtocol ff_concatf_protocol;
 extern const URLProtocol ff_crypto_protocol;
 extern const URLProtocol ff_data_protocol;
 extern const URLProtocol ff_ffrtmpcrypt_protocol;