/* https://xiph.org/flac/format.html */#include "tagspriv.h" #define beu3(d) ((d)[0]<<16 | (d)[1]<<8 | (d)[2]<<0) inttagflac(Tagctx *ctx){	uint8_t *d;	int sz, last;	uint64_t g; 	d = (uint8_t*)ctx->buf;	/* 8 bytes for marker, block type, length. 18 bytes for the stream info */	if(ctx->read(ctx, d, 8+18) != 8+18 || memcmp(d, "fLaC\x00", 5) != 0)		return -1; 	sz = beu3(&d[5]); /* size of the stream info */	ctx->samplerate = beu3(&d[18]) >> 4;	ctx->channels = ((d[20]>>1) & 7) + 1;	if(ctx->samplerate < 1 || ctx->channels < 1)		return -1; 	g = (uint64_t)(d[21] & 0xf)<<32 | beu3(&d[22])<<8 | d[25];	ctx->duration = g * 1000 / ctx->samplerate; 	/* skip the rest of the stream info */	if(ctx->seek(ctx, sz-18, 1) != ctx->restart+8+sz)		return -1; 	for(last = 0; !last;){		if(ctx->read(ctx, d, 4) != 4)			return -1; 		if((sz = beu3(&d[1])) < 0)			return -1;		if((d[0] & 0x80) != 0)			last = 1; 		if((d[0] & 0x7f) == 6){ /* 6 = picture */			int n, offset;			char *mime; 			if(sz < 8+4+20 || ctx->read(ctx, d, 8) != 8) /* type, mime length */				return -1;			sz -= 8;			n = beuint(&d[4]);			mime = ctx->buf+20;			if(n < 0 || n >= sz-4-20 || n >= ctx->bufsz-20 || ctx->read(ctx, mime, n) != n)				return -1;			sz -= n;			mime[n] = 0;			ctx->read(ctx, d, 4); /* description */			sz -= 4;			offset = beuint(d) + ctx->seek(ctx, 0, 1) + 20;			ctx->read(ctx, d, 20);			sz -= 20;			if((n = beuint(&d[16])) < 0)				return -1;			if(n > 0)				tagscallcb(ctx, Timage, "", mime, offset, n, nil);			if(ctx->seek(ctx, sz, 1) <= 0)				return -1;		}else if((d[0] & 0x7f) == 4){ /* 4 = vorbis comment */			int i, numtags, tagsz, vensz;			char *k, *v; 			if(sz < 12 || ctx->read(ctx, d, 4) != 4)				return -1; 			sz -= 4;			vensz = leuint(d);			if(vensz < 0 || vensz > sz-4)				return -1;			/* skip vendor, read the number of tags */			if(ctx->seek(ctx, vensz, 1) < 0 || ctx->read(ctx, d, 4) != 4)				return -1;			sz -= vensz + 4;			numtags = leuint(d); 			for(i = 0; i < numtags && sz > 4; i++){				if(ctx->read(ctx, d, 4) != 4)					return -1;				tagsz = leuint(d);				sz -= 4;				if(tagsz < 0 || tagsz > sz)					return -1; 				/* if it doesn't fit, ignore it */				if(tagsz == 0 || tagsz >= ctx->bufsz){					if(ctx->seek(ctx, tagsz, 1) < 0)						return -1;					continue;				} 				k = ctx->buf;				if(ctx->read(ctx, k, tagsz) != tagsz)					return -1;				/* some tags have a stupid '\r'; ignore */				if(k[tagsz-1] == '\r')					k[tagsz-1] = 0;				k[tagsz] = 0; 				if((v = strchr(k, '=')) != nil){					*v++ = 0;					cbvorbiscomment(ctx, k, v);				}			}		}else if(ctx->seek(ctx, sz, 1) <= 0)			return -1;	} 	return 0;}