/* http://wiki.multimedia.cx/?title=QuickTime_container *//* https://developer.apple.com/library/mac/documentation/QuickTime/QTFF/QTFFChap2/qtff2.html */#include "tagspriv.h" #define beuint16(d) (uint16_t)((d)[0]<<8 | (d)[1]<<0) inttagm4a(Tagctx *ctx){	uint64_t duration;	uint x;	uint8_t *d;	int sz, type, dtype, i, skip, n; 	d = (uint8_t*)ctx->buf;	/* 4 bytes for atom size, 4 for type, 4 for data - exect "ftyp" to come first */	if(ctx->read(ctx, d, 4+4+4) != 4+4+4 || memcmp(d+4, "ftypM4A ", 8) != 0)		return -1;	sz = beuint(d) - 4; /* already have 8 bytes */ 	for(;;){		if(sz < 0 || ctx->seek(ctx, sz, 1) < 0)			return -1;		if(ctx->read(ctx, d, 4) != 4) /* size */			break;		sz = beuint(d);		if(sz == 0)			continue;		if(ctx->read(ctx, d, 4) != 4) /* type */			return -1;		if(sz < 8)			continue; 		d[4] = 0; 		if(memcmp(d, "meta", 4) == 0){			sz = 4;			continue;		}else if(			memcmp(d, "udta", 4) == 0 ||			memcmp(d, "ilst", 4) == 0 ||			memcmp(d, "trak", 4) == 0 ||			memcmp(d, "mdia", 4) == 0 ||			memcmp(d, "minf", 4) == 0 ||			memcmp(d, "moov", 4) == 0 ||			memcmp(d, "trak", 4) == 0 ||			memcmp(d, "stbl", 4) == 0){			sz = 0;			continue;		}else if(memcmp(d, "stsd", 4) == 0){			sz -= 8;			if(ctx->read(ctx, d, 8) != 8)				return -1;			sz -= 8; 			for(i = beuint(&d[4]); i > 0 && sz > 0; i--){				if(ctx->read(ctx, d, 8) != 8) /* size + format */					return -1;				sz -= 8;				skip = beuint(d) - 8;				if(skip < 0)					return -1; 				if(memcmp(&d[4], "mp4a", 4) == 0){ /* audio */					n = 6+2 + 2+4+2 + 2+2 + 2+2 + 4; /* read a bunch at once */					/* reserved+id, ver+rev+vendor, channels+bps, ?+?, sample rate */					if(ctx->read(ctx, d, n) != n)						return -1;					skip -= n;					sz -= n;					ctx->channels = beuint16(&d[16]);					ctx->samplerate = beuint(&d[24])>>16;				} 				if(ctx->seek(ctx, skip, 1) < 0)					return -1;				sz -= skip;			}			continue;		} 		sz -= 8;		type = -1;		if(memcmp(d, "\251nam", 4) == 0)			type = Ttitle;		else if(memcmp(d, "\251alb", 4) == 0)			type = Talbum;		else if(memcmp(d, "\251ART", 4) == 0)			type = Tartist;		else if(memcmp(d, "\251gen", 4) == 0 || memcmp(d, "gnre", 4) == 0)			type = Tgenre;		else if(memcmp(d, "\251day", 4) == 0)			type = Tdate;		else if(memcmp(d, "covr", 4) == 0)			type = Timage;		else if(memcmp(d, "trkn", 4) == 0)			type = Ttrack;		else if(memcmp(d, "\251wrt", 4) == 0)			type = Tcomposer;		else if(memcmp(d, "\251cmt", 4) == 0)			type = Tcomment;		else if(memcmp(d, "mdhd", 4) == 0){			if(ctx->read(ctx, d, 4) != 4)				return -1;			sz -= 4;			duration = 0;			if(d[0] == 0){ /* version 0 */				if(ctx->read(ctx, d, 16) != 16)					return -1;				sz -= 16;				if((x = beuint(&d[8])) > 0)					duration = beuint(&d[12]) / x;			}else if(d[1] == 1){ /* version 1 */				if(ctx->read(ctx, d, 28) != 28)					return -1;				sz -= 28;				if((x = beuint(&d[16])) > 0)					duration = ((uint64_t)beuint(&d[20])<<32 | beuint(&d[24])) / (uint64_t)x;			}			ctx->duration = duration * 1000;			continue;		} 		if(type < 0)			continue; 		if(sz < 16 || ctx->seek(ctx, 8, 1) < 0) /* skip size and "data" */			return -1;		sz -= 8;		if(ctx->read(ctx, d, 8) != 8) /* read data type and 4 bytes of whatever else */			return -1;		sz -= 8;		d[0] = 0;		dtype = beuint(d); 		if(type == Ttrack){			if(ctx->read(ctx, d, 4) != 4)				return -1;			sz -= 4;			snprintf((char*)d, ctx->bufsz, "%d", beuint(d));			txtcb(ctx, type, "", d);		}else if(type == Tgenre && dtype != 1){			if(ctx->read(ctx, d, 2) != 2)				return -1;			sz -= 2;			if((i = d[1]-1) >= 0 && i < Numgenre)				txtcb(ctx, type, "", id3genres[i]);		}else if(dtype == 1){ /* text */			if(sz >= ctx->bufsz) /* skip tags that can't fit into memory. ">=" because of '\0' */				continue;			if(sz < 0 || ctx->read(ctx, d, sz) != sz)				return -1;			d[sz] = 0;			txtcb(ctx, type, "", d);			sz = 0;		}else if(type == Timage && dtype == 13) /* jpeg cover image */			tagscallcb(ctx, Timage, "", "image/jpeg", ctx->seek(ctx, 0, 1), sz, nil);		else if(type == Timage && dtype == 14) /* png cover image */			tagscallcb(ctx, Timage, "", "image/png", ctx->seek(ctx, 0, 1), sz, nil);	} 	return 0;}