YueWen/node_modules/exif-parser/lib/jpeg.js

/*jslint browser: true, devel: true, bitwise: false, debug: true, eqeq: false, es5: true, evil: false, forin: false, newcap: false, nomen: true, plusplus: true, regexp: false, unparam: false, sloppy: true, stupid: false, sub: false, todo: true, vars: true, white: true */

module.exports = {
	parseSections: function(stream, iterator) {
		var len, markerType;
		stream.setBigEndian(true);
		//stop reading the stream at the SOS (Start of Stream) marker,
		//because its length is not stored in the header so we can't
		//know where to jump to. The only marker after that is just EOI (End Of Image) anyway
		while(stream.remainingLength() > 0 && markerType !== 0xDA) {
			if(stream.nextUInt8() !== 0xFF) {
				throw new Error('Invalid JPEG section offset');
			}
			markerType = stream.nextUInt8();
			//don't read size from markers that have no datas
			if((markerType >= 0xD0 && markerType <= 0xD9) || markerType === 0xDA) {
				len = 0;
			} else {
				len = stream.nextUInt16() - 2;
			}
			iterator(markerType, stream.branch(0, len));
			stream.skip(len);
		}
	},
	//stream should be located after SOF section size and in big endian mode, like passed to parseSections iterator
	getSizeFromSOFSection: function(stream) {
		stream.skip(1);
		return {
			height: stream.nextUInt16(),
			width: stream.nextUInt16()
		};
	},
	getSectionName: function(markerType) {
		var name, index;
		switch(markerType) {
			case 0xD8: name = 'SOI'; break;
			case 0xC4: name = 'DHT'; break;
			case 0xDB: name = 'DQT'; break;
			case 0xDD: name = 'DRI'; break;
			case 0xDA: name = 'SOS'; break;
			case 0xFE: name = 'COM'; break;
			case 0xD9: name = 'EOI'; break;
			default:
				if(markerType >= 0xE0 && markerType <= 0xEF) {
					name = 'APP';
					index = markerType - 0xE0;
				}
				else if(markerType >= 0xC0 && markerType <= 0xCF && markerType !== 0xC4 && markerType !== 0xC8 && markerType !== 0xCC) {
					name = 'SOF';
					index = markerType - 0xC0;
				}
				else if(markerType >= 0xD0 && markerType <= 0xD7) {
					name = 'RST';
					index = markerType - 0xD0;
				}
				break;
		}
		var nameStruct = {
			name: name
		};
		if(typeof index === 'number') {
			nameStruct.index = index;
		}
		return nameStruct;
	}
};