avformat/concatdec: add support for very long line sizes

Fixes ticket #6761.
Signed-off-by: Marton Balint <cus@passwd.hu>

libavformat/concatdec.c

@@ -20,6 +20,7 @@
 
 #include "libavutil/avassert.h"
 #include "libavutil/avstring.h"
+#include "libavutil/bprint.h"
 #include "libavutil/intreadwrite.h"
 #include "libavutil/opt.h"
 #include "libavutil/parseutils.h"
@@ -386,18 +387,18 @@ static int concat_read_close(AVFormatContext *avf)
 static int concat_read_header(AVFormatContext *avf)
 {
     ConcatContext *cat = avf->priv_data;
-    uint8_t buf[4096];
+    AVBPrint bp;
     uint8_t *cursor, *keyword;
-    int ret, line = 0, i;
+    int line = 0, i;
     unsigned nb_files_alloc = 0;
     ConcatFile *file = NULL;
-    int64_t time = 0;
+    int64_t ret, time = 0;
 
-    while (1) {
-        if ((ret = ff_get_line(avf->pb, buf, sizeof(buf))) <= 0)
-            break;
+    av_bprint_init(&bp, 0, AV_BPRINT_SIZE_UNLIMITED);
+
+    while ((ret = ff_read_line_to_bprint_overwrite(avf->pb, &bp)) >= 0) {
         line++;
-        cursor = buf;
+        cursor = bp.str;
         keyword = get_keyword(&cursor);
         if (!*keyword || *keyword == '#')
             continue;
@@ -473,7 +474,7 @@ static int concat_read_header(AVFormatContext *avf)
             FAIL(AVERROR_INVALIDDATA);
         }
     }
-    if (ret < 0)
+    if (ret != AVERROR_EOF && ret < 0)
         goto fail;
     if (!cat->nb_files)
         FAIL(AVERROR_INVALIDDATA);
@@ -499,9 +500,11 @@ static int concat_read_header(AVFormatContext *avf)
                                                MATCH_ONE_TO_ONE;
     if ((ret = open_file(avf, 0)) < 0)
         goto fail;
+    av_bprint_finalize(&bp, NULL);
     return 0;
 
 fail:
+    av_bprint_finalize(&bp, NULL);
     concat_read_close(avf);
     return ret;
 }