static int shift_data(AVFormatContext *s) { int ret = 0, moov_size; MOVMuxContext *mov = s->priv_data; int64_t pos, pos_end = avio_tell(s->pb); 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); else moov_size = compute_moov_size(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 = avio_open(&read_pb, s->filename, AVIO_FLAG_READ); if (ret < 0) { av_log(s, AV_LOG_ERROR, "Unable to re-open %s output file for " "the second pass (faststart)\n", s->filename); 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); avio_close(read_pb); end: av_free(buf); return ret; }