avformat/file: add seekable option to disallow seeking

Signed-off-by: Marton Balint <cus@passwd.hu>

doc/protocols.texi

@@ -199,6 +199,14 @@ If set to 1, the protocol will retry reading at the end of the file, allowing
 reading files that still are being written. In order for this to terminate,
 you either need to use the rw_timeout option, or use the interrupt callback
 (for API users).
+
+@item seekable
+Controls if seekability is advertised on the file. 0 means non-seekable, -1
+means auto (seekable for normal files, non-seekable for named pipes).
+
+Many demuxers handle seekable and non-seekable resources differently,
+overriding this might speed up opening certain files at the cost of losing some
+features (e.g. accurate seeking).
 @end table
 
 @section ftp

libavformat/file.c

@@ -73,6 +73,7 @@ typedef struct FileContext {
     int trunc;
     int blocksize;
     int follow;
+    int seekable;
 #if HAVE_DIRENT_H
     DIR *dir;
 #endif
@@ -82,6 +83,7 @@ static const AVOption file_options[] = {
     { "truncate", "truncate existing files on write", offsetof(FileContext, trunc), AV_OPT_TYPE_BOOL, { .i64 = 1 }, 0, 1, AV_OPT_FLAG_ENCODING_PARAM },
     { "blocksize", "set I/O operation maximum block size", offsetof(FileContext, blocksize), AV_OPT_TYPE_INT, { .i64 = INT_MAX }, 1, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM },
     { "follow", "Follow a file as it is being written", offsetof(FileContext, follow), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, AV_OPT_FLAG_DECODING_PARAM },
+    { "seekable", "Sets if the file is seekable", offsetof(FileContext, seekable), AV_OPT_TYPE_INT, { .i64 = -1 }, -1, 0, AV_OPT_FLAG_DECODING_PARAM | AV_OPT_FLAG_ENCODING_PARAM },
     { NULL }
 };
 
@@ -238,6 +240,9 @@ static int file_open(URLContext *h, const char *filename, int flags)
     if (!h->is_streamed && flags & AVIO_FLAG_WRITE)
         h->min_packet_size = h->max_packet_size = 262144;
 
+    if (c->seekable >= 0)
+        h->is_streamed = !c->seekable;
+
     return 0;
 }
 

libavformat/version.h

@@ -33,7 +33,7 @@
 // Also please add any ticket numbers that you believe might be affected here
 #define LIBAVFORMAT_VERSION_MAJOR  58
 #define LIBAVFORMAT_VERSION_MINOR  27
-#define LIBAVFORMAT_VERSION_MICRO 101
+#define LIBAVFORMAT_VERSION_MICRO 102
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
                                                LIBAVFORMAT_VERSION_MINOR, \