shithub: libtags

ref: 63b1d8e124c602cf5bec357e1f04653a86e6af52
dir: /vorbis.c/

/*
 * https://xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-810005
 * https://wiki.xiph.org/VorbisComment
 */
#include "tagspriv.h"

#define leuint(d) (uint)(((uchar*)(d))[3]<<24 | ((uchar*)(d))[2]<<16 | ((uchar*)(d))[1]<<8 | ((uchar*)(d))[0]<<0)

void
cbvorbiscomment(Tagctx *ctx, char *k, char *v){
	if(*v == 0)
		return;
	if(cistrcmp(k, "album") == 0)
		txtcb(ctx, Talbum, k, v);
	else if(cistrcmp(k, "title") == 0)
		txtcb(ctx, Ttitle, k, v);
	else if(cistrcmp(k, "artist") == 0 || cistrcmp(k, "performer") == 0)
		txtcb(ctx, Tartist, k, v);
	else if(cistrcmp(k, "tracknumber") == 0)
		txtcb(ctx, Ttrack, k, v);
	else if(cistrcmp(k, "date") == 0)
		txtcb(ctx, Tdate, k, v);
	else if(cistrcmp(k, "replaygain_track_peak") == 0)
		txtcb(ctx, Ttrackpeak, k, v);
	else if(cistrcmp(k, "replaygain_track_gain") == 0)
		txtcb(ctx, Ttrackgain, k, v);
	else if(cistrcmp(k, "replaygain_album_peak") == 0)
		txtcb(ctx, Talbumpeak, k, v);
	else if(cistrcmp(k, "replaygain_album_gain") == 0)
		txtcb(ctx, Talbumgain, k, v);
	else if(cistrcmp(k, "genre") == 0)
		txtcb(ctx, Tgenre, k, v);
	else
		txtcb(ctx, Tunknown, k, v);
}

int
tagvorbis(Tagctx *ctx)
{
	char *v;
	uchar *d, h[4];
	int sz, numtags, i, npages;

	d = (uchar*)ctx->buf;
	/* need to find vorbis frame with type=3 */
	for(npages = 0; npages < 2; npages++){ /* vorbis comment is the second header */
		int nsegs;
		if(ctx->read(ctx, d, 27) != 27)
			return -1;
		if(memcmp(d, "OggS", 4) != 0)
			return -1;

		/* calculate the size of the packet */
		nsegs = d[26];
		if(ctx->read(ctx, d, nsegs+1) != nsegs+1)
			return -1;
		for(sz = i = 0; i < nsegs; sz += d[i++]);

		if(d[nsegs] == 3) /* comment */
			break;
		if(d[nsegs] == 1 && sz >= 28){ /* identification */
			if(ctx->read(ctx, d, 28) != 28)
				return -1;
			sz -= 28;
			ctx->channels = d[10];
			ctx->samplerate = leuint(&d[11]);
			if((ctx->bitrate = leuint(&d[15])) == 0) /* maximum */
				ctx->bitrate = leuint(&d[19]); /* nominal */
		}

		ctx->seek(ctx, sz-1, 1);
	}

	if(ctx->read(ctx, &d[1], 10) != 10 || memcmp(&d[1], "vorbis", 6) != 0)
		return -1;
	sz = leuint(&d[7]);
	if(ctx->seek(ctx, sz, 1) < 0 || ctx->read(ctx, h, 4) != 4)
		return -1;
	numtags = leuint(h);

	for(i = 0; i < numtags; i++){
		if(ctx->read(ctx, h, 4) != 4)
			return -1;
		if((sz = leuint(h)) < 0)
			return -1;

		if(ctx->bufsz < sz+1){
			if(ctx->seek(ctx, sz, 1) < 0)
				return -1;
			continue;
		}
		if(ctx->read(ctx, ctx->buf, sz) != sz)
			return -1;
		ctx->buf[sz] = 0;

		if((v = strchr(ctx->buf, '=')) == nil)
			return -1;
		*v++ = 0;
		cbvorbiscomment(ctx, ctx->buf, v);
	}

	/* calculate the duration */
	if(ctx->samplerate > 0){
		sz = ctx->bufsz <= 4096 ? ctx->bufsz : 4096;
		for(i = sz; i < 65536+16; i += sz - 16){
			if(ctx->seek(ctx, -i, 2) <= 0)
				break;
			v = ctx->buf;
			if(ctx->read(ctx, v, sz) != sz)
				break;
			for(; v != nil && v < ctx->buf+sz;){
				v = memchr(v, 'O', ctx->buf+sz - v - 14);
				if(v != nil && v[1] == 'g' && v[2] == 'g' && v[3] == 'S' && (v[5] & 4) == 4){ /* last page */
					uvlong g = leuint(v+6) | (uvlong)leuint(v+10)<<32;
					ctx->duration = g * 1000 / ctx->samplerate;
					return 0;
				}
				if(v != nil)
					v++;
			}
		}
	}

	return 0;
}