/* sync the stream and get a page. Keep trying until we find a page.
* Suppress 'sync errors' after reporting the first.
*
* return values:
* -1) recapture (hole in data)
* 0) need more data
* 1) page returned
*
* Returns pointers into buffered data; invalidated by next call to
* _stream, _clear, _init, or _buffer */
static public int ogg_sync_pageout(ref ogg_sync_state oy, ref ogg_page og)
{
if (ogg_sync_check(ref oy) != 0)
{
return(0);
}
/* all we need to do is verify a page at the head of the stream
* buffer. If it doesn't verify, we look for the next potential
* frame */
for (;;)
{
int ret = ogg_sync_pageseek(ref oy, ref og);
if (ret > 0)
{
/* have a page */
return(1);
}
if (ret == 0)
{
/* need more data */
return(0);
}
if (oy.unsynced == 0)
{
oy.unsynced = 1;
return(-1);
}
}
}
static public int ogg_sync_destroy(ref ogg_sync_state oy)
{
if (oy != null)
{
ogg_sync_clear(ref oy);
}
return(0);
}
/* clear things to an initial state. Good to call, eg, before seeking */
static public int ogg_sync_reset(ref ogg_sync_state oy)
{
if (ogg_sync_check(ref oy) != 0)
{
return(-1);
}
oy.fill = 0;
oy.returned = 0;
oy.unsynced = 0;
oy.headerbytes = 0;
oy.bodybytes = 0;
return(0);
}
static public int ogg_sync_wrote(ref ogg_sync_state oy, int bytes)
{
if (ogg_sync_check(ref oy) != 0)
{
return(-1);
}
if (oy.fill + bytes > oy.storage)
{
return(-1);
}
oy.fill += bytes;
return(0);
}
static public int ogg_sync_check(ref ogg_sync_state oy)
{
if (oy == null)
{
return(-1);
}
else if (oy.storage < 0)
{
return(-1);
}
else
{
return(0);
}
}
static public byte *ogg_sync_buffer(ref ogg_sync_state oy, int size)
{
if (ogg_sync_check(ref oy) != 0)
{
return(null);
}
/* first, clear out any space that has been previously returned */
if (oy.returned > 0)
{
oy.fill -= oy.returned;
if (oy.fill > 0)
{
CopyMemory(oy.data, oy.data + oy.returned, oy.fill);
}
oy.returned = 0;
}
if (size > oy.storage - oy.fill)
{
/* We need to extend the internal buffer */
int newsize = size + oy.fill + 4096; /* an extra page to be nice */
if (oy.data != null)
{
oy.data = (byte *)_ogg_realloc(oy.data, newsize);
}
else
{
oy.data = (byte *)_ogg_malloc(newsize);
}
oy.storage = newsize;
}
/* expose a segment at least as large as requested at the fill mark */
return(oy.data + oy.fill);
}
static public int ogg_sync_clear(ref ogg_sync_state oy)
{
if (oy == null)
{
return(1);
}
if (oy.data != null)
{
_ogg_free(oy.data);
}
oy.data = null;
oy.storage = 0;
oy.fill = 0;
oy.returned = 0;
oy.unsynced = 0;
oy.headerbytes = 0;
oy.bodybytes = 0;
return(0);
}
public static extern int ogg_sync_pageout(ref ogg_sync_state oy, ref ogg_page og);
public static extern int ogg_sync_wrote(ref ogg_sync_state oy, int bytes);
public static extern IntPtr ogg_sync_buffer(ref ogg_sync_state oy, int size);
public static extern int ogg_sync_reset(ref ogg_sync_state oy);
public static extern int ogg_sync_destroy(ref ogg_sync_state oy);
public static extern int ogg_sync_clear(ref ogg_sync_state oy);
public static extern int ogg_sync_check(ref ogg_sync_state oy);
public static extern int ogg_sync_init(ref ogg_sync_state oy);
/* DECODING PRIMITIVES: packet streaming layer */
/* This has two layers to place more of the multi-serialno and paging control in the application's hands. First, we expose a data buffer
* using ogg_sync_buffer(). The app either copies into the buffer, or passes it directly to read(), etc. We then call
* ogg_sync_wrote() to tell how many bytes we just added.
*
* Pages are returned (pointers into the buffer in ogg_sync_state) by ogg_sync_pageout(). The page is then submitted to
* ogg_stream_pagein() along with the appropriate ogg_stream_state* (ie, matching serialno). We then get raw packets out calling ogg_stream_packetout() with a
* ogg_stream_state. */
/* initialize the struct to a known state */
static public int ogg_sync_init(ref ogg_sync_state oy)
{
return(ogg_sync_clear(ref oy));
}
static public int ogg_sync_pageseek(ref ogg_sync_state oy, ref ogg_page og)
{
byte *page = oy.data + oy.returned;
byte *next = null;
int bytes = oy.fill - oy.returned;
if (ogg_sync_check(ref oy) != 0)
{
return(0);
}
if (oy.headerbytes == 0)
{
int headerbytes;
if (bytes < 27)
{
return(0);
}
if
(
page[0] != 'O' ||
page[1] != 'g' ||
page[2] != 'g' ||
page[3] != 'S'
)
{
goto sync_fail;
}
else
{
headerbytes = page[26] + 27;
if (bytes < headerbytes)
{
return(0);
}
for (int i = 0; i < page[26]; i++)
{
oy.bodybytes += page[27 + i];
}
oy.headerbytes = headerbytes;
}
}
if (oy.bodybytes + oy.headerbytes > bytes)
{
return(0);
}
/* The whole test page is buffered. Verify the checksum */
{
byte[] chksum = new byte[4];
ogg_page log = new ogg_page();
/* Grab the checksum bytes, set the header field to zero */
Marshal.Copy((IntPtr)(page + 22), chksum, 0, 4);
ZeroMemory(page + 22, 4);
/* set up a temp page struct and recompute the checksum */
log.header = page;
log.header_len = oy.headerbytes;
log.body = page + oy.headerbytes;
log.body_len = oy.bodybytes;
ogg_page_checksum_set(ref log);
/* Compare */
if
(
chksum[0] != page[22] ||
chksum[1] != page[23] ||
chksum[2] != page[24] ||
chksum[3] != page[25]
)
{
/* D'oh. Mismatch! Corrupt page (or miscapture and not a page at all) */
/* replace the computed checksum with the one actually read in */
Marshal.Copy(chksum, 0, (IntPtr)(page + 22), 4);
/* Bad checksum. Lose sync */
goto sync_fail;
}
}
/* yes, have a whole page all ready to go */
{
byte *_page = oy.data + oy.returned;
bytes = oy.headerbytes + oy.bodybytes;
if (og != null)
{
og.header = _page;
og.header_len = oy.headerbytes;
og.body = _page + oy.headerbytes;
og.body_len = oy.bodybytes;
}
oy.unsynced = 0;
oy.returned += bytes;
oy.headerbytes = 0;
oy.bodybytes = 0;
return(bytes);
}
sync_fail:
oy.headerbytes = 0;
oy.bodybytes = 0;
for (int i = 1; i < bytes; i++)
{
if (page[i] == 'O')
{
next = (byte *)(page + i);
break;
}
}
if (next == null)
{
next = oy.data + oy.fill;
}
oy.returned = (int)(next - oy.data);
return((int)-(next - page));
}
