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/*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;
}
};