/********************************************************************
 *                                                                  *
 * USE, DISTRIBUTION AND REPRODUCTION OF THIS CODE IS               *
 * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
 * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
 *                                                                  *
 * THE OggVorbis SOURCE CODE IS (C) COPYRIGHT 1994-2002             *
 * by the XIPHOPHORUS Company http://www.xiph.org/                  *
 *                                                                  *
 ********************************************************************

function: simple example decoder
last mod: $Id: decoder_example.c 7187 2004-07-20 07:24:27Z xiphmont $

 ********************************************************************/

/* Takes a vorbis bitstream from stdin and rewrites the granulepos to start
 * from 0. This is a quick hack, combining decoder_example and
 * encoder_example without doing a full decode/encode step. */

/* compile with -logg -lvorbis */

/* Note that this is POSIX, not ANSI code */

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <vorbis/codec.h>

#ifdef _WIN32 /* We need the following two to set stdin/stdout to binary */
#include <io.h>
#include <fcntl.h>
#endif

#if defined(__MACOS__) && defined(__MWERKS__)
#include <console.h>      /* CodeWarrior's Mac "command-line" support */
#endif

ogg_int16_t convbuffer[4096]; /* take 8k out of the data segment, not the stack */
int convsize=4096;

extern void _VDBG_dump(void);


int main(){
	ogg_sync_state   oy; /* sync and verify incoming physical bitstream */
	ogg_stream_state os; /* take physical pages, weld into a logical
							stream of packets */
	ogg_page         og; /* one Ogg bitstream page.  Vorbis packets are inside */
	ogg_packet       op; /* one raw packet of data for decode */

	ogg_stream_state os_out;
	ogg_page og_out;
	ogg_packet op_out;

	vorbis_info      vi; /* struct that stores all the static vorbis bitstream
							settings */
	vorbis_comment   vc; /* struct that stores all the bitstream user comments */
	vorbis_dsp_state vd; /* central working state for the packet->PCM decoder */
	vorbis_block     vb; /* local working space for packet->PCM decode */

	char *buffer;
	int  bytes;

#ifdef _WIN32 /* We need to set stdin/stdout to binary mode. Damn windows. */
	/* Beware the evil ifdef. We avoid these where we can, but this one we 
	   cannot. Don't add any more, you'll probably go to hell if you do. */
	_setmode( _fileno( stdin ), _O_BINARY );
	_setmode( _fileno( stdout ), _O_BINARY );
#endif

#if defined(macintosh) && defined(__MWERKS__)
	{
		int argc;
		char **argv;
		argc=ccommand(&argv); /* get a "command line" from the Mac user */
		/* this also lets the user set stdin and stdout */
	}
#endif

	/********** Decode setup ************/

	ogg_sync_init(&oy); /* Now we can read pages */

	while(1){ /* we repeat if the bitstream is chained */
		int eos=0;
		int i;
		ogg_int64_t new_granpos = 0;

		/* grab some data at the head of the stream.  We want the first page
		   (which is guaranteed to be small and only contain the Vorbis
		   stream initial header) We need the first page to get the stream
		   serialno. */

		/* submit a 4k block to libvorbis' Ogg layer */
		buffer=ogg_sync_buffer(&oy,4096);
		bytes=fread(buffer,1,4096,stdin);
		ogg_sync_wrote(&oy,bytes);

		/* Get the first page. */
		if(ogg_sync_pageout(&oy,&og)!=1){
			/* have we simply run out of data?  If so, we're done. */
			if(bytes<4096)break;

			/* error case.  Must not be Vorbis data */
			fprintf(stderr,"Input does not appear to be an Ogg bitstream.\n");
			exit(1);
		}

		/* Get the serial number and set up the rest of decode. */
		/* serialno first; use it to set up a logical stream */
		ogg_stream_init(&os,ogg_page_serialno(&og));
		ogg_stream_init(&os_out,ogg_page_serialno(&og));

		/* extract the initial header from the first page and verify that the
		   Ogg bitstream is in fact Vorbis data */

		/* I handle the initial header first instead of just having the code
		   read all three Vorbis headers at once because reading the initial
		   header is an easy way to identify a Vorbis bitstream and it's
		   useful to see that functionality seperated out. */

		vorbis_info_init(&vi);
		vorbis_comment_init(&vc);
		if(ogg_stream_pagein(&os,&og)<0){ 
			/* error; stream version mismatch perhaps */
			fprintf(stderr,"Error reading first page of Ogg bitstream data.\n");
			exit(1);
		}

		if(ogg_stream_packetout(&os,&op)!=1){ 
			/* no page? must not be vorbis */
			fprintf(stderr,"Error reading initial header packet.\n");
			exit(1);
		}
		ogg_stream_packetin(&os_out,&op);

		if(vorbis_synthesis_headerin(&vi,&vc,&op)<0){ 
			/* error case; not a vorbis header */
			fprintf(stderr,"This Ogg bitstream does not contain Vorbis "
					"audio data.\n");
			exit(1);
		}

		/* At this point, we're sure we're Vorbis.  We've set up the logical
		   (Ogg) bitstream decoder.  Get the comment and codebook headers and
		   set up the Vorbis decoder */

		/* The next two packets in order are the comment and codebook headers.
		   They're likely large and may span multiple pages.  Thus we reead
		   and submit data until we get our two pacakets, watching that no
		   pages are missing.  If a page is missing, error out; losing a
		   header page is the only place where missing data is fatal. */

		i=0;
		while(i<2){
			while(i<2){
				int result=ogg_sync_pageout(&oy,&og);
				int serial=ogg_page_serialno(&og);
				if(result==0)break; /* Need more data */
				/* Don't complain about missing or corrupt data yet.  We'll
				   catch it at the packet output phase */
				if(result==1){
					ogg_stream_pagein(&os,&og); /* we can ignore any errors here
												   as they'll also become apparent
												   at packetout */
					while(i<2){
						result=ogg_stream_packetout(&os,&op);
						if(result==0)break;
						if(result<0){
							/* Uh oh; data at some point was corrupted or missing!
							   We can't tolerate that in a header.  Die. */
							fprintf(stderr,"Corrupt secondary header.  Exiting.\n");
							exit(1);
						}
						ogg_stream_packetin(&os_out,&op);
						vorbis_synthesis_headerin(&vi,&vc,&op);
						fprintf(stderr, "got packet no. %ld with serialno %ld\n",
								(long int)op.packetno, (long int)serial );
						i++;
					}
				}
			}
			/* no harm in not checking before adding more */
			buffer=ogg_sync_buffer(&oy,4096);
			bytes=fread(buffer,1,4096,stdin);
			if(bytes==0 && i<2){
				fprintf(stderr,"End of file before finding all Vorbis headers!\n");
				exit(1);
			}
			ogg_sync_wrote(&oy,bytes);
		}
		/* This ensures the actual
		 * audio data will start on a new page, as per spec
		 */
		while(!eos){
			int result=ogg_stream_flush(&os_out,&og_out);
			if(result==0)break;
			fwrite(og_out.header,1,og_out.header_len,stdout);
			fwrite(og_out.body,1,og_out.body_len,stdout);
		}

		convsize=4096/vi.channels;

		/* OK, got and parsed all three headers. Initialize the Vorbis
		   packet->PCM decoder. */
		vorbis_synthesis_init(&vd,&vi); /* central decode state */
		vorbis_block_init(&vd,&vb);     /* local state for most of the decode
										   so multiple block decodes can
										   proceed in parallel.  We could init
										   multiple vorbis_block structures
										   for vd here */

		long samples, samples_prev = 0;
		int center, center_prev = 0;;
		/* The rest is just a straight decode loop until end of stream */
		i=0;
		while(!eos){
			while(!eos){
				int result=ogg_sync_pageout(&oy,&og);
				if(result==0)break; /* need more data */
				if(result<0){ /* missing or corrupt data at this page position */
					fprintf(stderr,"Corrupt or missing data in bitstream; "
							"continuing...\n");
				}else{
					ogg_stream_pagein(&os,&og); /* can safely ignore errors at
												   this point */
					while(1){
						result=ogg_stream_packetout(&os,&op);

						if(result==0)break; /* need more data */
						if(result<0){ /* missing or corrupt data at this page position */
							/* no reason to complain; already complained above */
						}else{
							/* we have a packet.  Rewrite it */
							if(vorbis_synthesis(&vb,&op)==0) /* test for success! */
								vorbis_synthesis_blockin(&vd,&vb);

							samples = vorbis_packet_blocksize(&vi, &op);
							if(samples_prev == 0) {
								samples_prev = samples;
							} else {
								new_granpos += samples_prev/4 + samples/4;
								samples_prev = samples;
							}
							if( op.granulepos != -1 ) op.granulepos = new_granpos;
							if( op.e_o_s )
								fprintf( stderr, "found eos at packet no %ld\n",
										(long)op.packetno );
							ogg_stream_packetin(&os_out,&op);
							i++;
						}
					}
					int result=ogg_stream_pageout(&os_out,&og_out);
					if(result==0)break;
					fwrite(og_out.header,1,og_out.header_len,stdout);
					fwrite(og_out.body,1,og_out.body_len,stdout);

					/* this could be set above, but for illustrative purposes, I do
					   it here (to show that vorbis does know where the stream ends) */
					if(ogg_page_eos(&og))eos=1;
				}
			}
			if(!eos){
				buffer=ogg_sync_buffer(&oy,4096);
				bytes=fread(buffer,1,4096,stdin);
				ogg_sync_wrote(&oy,bytes);
				if(bytes==0)eos=1;
			}
		}
		{
		int result=ogg_stream_flush(&os_out,&og_out);
		if(result==0)break;
		fwrite(og_out.header,1,og_out.header_len,stdout);
		fwrite(og_out.body,1,og_out.body_len,stdout);
		}

		/* clean up this logical bitstream; before exit we see if we're
		   followed by another [chained] */

		ogg_stream_clear(&os);
	}

	/* OK, clean up the framer */
	ogg_sync_clear(&oy);

	fprintf(stderr,"Done.\n");
	return(0);
}