avformat/movenc: factorize data shifting

And move data shift function from movenc to utils.

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

libavformat/internal.h

@@ -1019,4 +1019,11 @@ void ff_format_set_url(AVFormatContext *s, char *url);
 
 void avpriv_register_devices(const AVOutputFormat * const o[], const AVInputFormat * const i[]);
 
+/**
+ * Make shift_size amount of space at read_start by shifting data in the output
+ * at read_start until the current IO position. The underlying IO context must
+ * be seekable.
+ */
+int ff_format_shift_data(AVFormatContext *s, int64_t read_start, int shift_size);
+
 #endif /* AVFORMAT_INTERNAL_H */

libavformat/movenc.c

@@ -7150,13 +7150,8 @@ static int compute_sidx_size(AVFormatContext *s)
 
 static int shift_data(AVFormatContext *s)
 {
-    int ret = 0, moov_size;
+    int moov_size;
     MOVMuxContext *mov = s->priv_data;
-    int64_t pos, pos_end;
-    uint8_t *buf, *read_buf[2];
-    int read_buf_id = 0;
-    int read_size[2];
-    AVIOContext *read_pb;
 
     if (mov->flags & FF_MOV_FLAG_FRAGMENT)
         moov_size = compute_sidx_size(s);
@@ -7165,53 +7160,7 @@ static int shift_data(AVFormatContext *s)
     if (moov_size < 0)
         return moov_size;
 
-    buf = av_malloc(moov_size * 2);
-    if (!buf)
-        return AVERROR(ENOMEM);
-    read_buf[0] = buf;
-    read_buf[1] = buf + moov_size;
-
-    /* Shift the data: the AVIO context of the output can only be used for
-     * writing, so we re-open the same output, but for reading. It also avoids
-     * a read/seek/write/seek back and forth. */
-    avio_flush(s->pb);
-    ret = s->io_open(s, &read_pb, s->url, AVIO_FLAG_READ, NULL);
-    if (ret < 0) {
-        av_log(s, AV_LOG_ERROR, "Unable to re-open %s output file for "
-               "the second pass (faststart)\n", s->url);
-        goto end;
-    }
-
-    /* mark the end of the shift to up to the last data we wrote, and get ready
-     * for writing */
-    pos_end = avio_tell(s->pb);
-    avio_seek(s->pb, mov->reserved_header_pos + moov_size, SEEK_SET);
-
-    /* start reading at where the new moov will be placed */
-    avio_seek(read_pb, mov->reserved_header_pos, SEEK_SET);
-    pos = avio_tell(read_pb);
-
-#define READ_BLOCK do {                                                             \
-    read_size[read_buf_id] = avio_read(read_pb, read_buf[read_buf_id], moov_size);  \
-    read_buf_id ^= 1;                                                               \
-} while (0)
-
-    /* shift data by chunk of at most moov_size */
-    READ_BLOCK;
-    do {
-        int n;
-        READ_BLOCK;
-        n = read_size[read_buf_id];
-        if (n <= 0)
-            break;
-        avio_write(s->pb, read_buf[read_buf_id], n);
-        pos += n;
-    } while (pos < pos_end);
-    ff_format_io_close(s, &read_pb);
-
-end:
-    av_free(buf);
-    return ret;
+    return ff_format_shift_data(s, mov->reserved_header_pos, moov_size);
 }
 
 static int mov_write_trailer(AVFormatContext *s)

libavformat/utils.c

@@ -2035,3 +2035,59 @@ const char *av_disposition_to_string(int disposition)
 
     return NULL;
 }
+
+int ff_format_shift_data(AVFormatContext *s, int64_t read_start, int shift_size)
+{
+    int ret;
+    int64_t pos, pos_end;
+    uint8_t *buf, *read_buf[2];
+    int read_buf_id = 0;
+    int read_size[2];
+    AVIOContext *read_pb;
+
+    buf = av_malloc_array(shift_size, 2);
+    if (!buf)
+        return AVERROR(ENOMEM);
+    read_buf[0] = buf;
+    read_buf[1] = buf + shift_size;
+
+    /* Shift the data: the AVIO context of the output can only be used for
+     * writing, so we re-open the same output, but for reading. It also avoids
+     * a read/seek/write/seek back and forth. */
+    avio_flush(s->pb);
+    ret = s->io_open(s, &read_pb, s->url, AVIO_FLAG_READ, NULL);
+    if (ret < 0) {
+        av_log(s, AV_LOG_ERROR, "Unable to re-open %s output file for shifting data\n", s->url);
+        goto end;
+    }
+
+    /* mark the end of the shift to up to the last data we wrote, and get ready
+     * for writing */
+    pos_end = avio_tell(s->pb);
+    avio_seek(s->pb, read_start + shift_size, SEEK_SET);
+
+    avio_seek(read_pb, read_start, SEEK_SET);
+    pos = avio_tell(read_pb);
+
+#define READ_BLOCK do {                                                             \
+    read_size[read_buf_id] = avio_read(read_pb, read_buf[read_buf_id], shift_size);  \
+    read_buf_id ^= 1;                                                               \
+} while (0)
+
+    /* shift data by chunk of at most shift_size */
+    READ_BLOCK;
+    do {
+        int n;
+        READ_BLOCK;
+        n = read_size[read_buf_id];
+        if (n <= 0)
+            break;
+        avio_write(s->pb, read_buf[read_buf_id], n);
+        pos += n;
+    } while (pos < pos_end);
+    ff_format_io_close(s, &read_pb);
+
+end:
+    av_free(buf);
+    return ret;
+}