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Added the possibility of reading little endian bits #87

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Added the possibility of reading little endian bits #87

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75 changes: 70 additions & 5 deletions lib/binary_parser.js
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Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,8 @@ var SPECIAL_TYPES = {
Skip: null,
Choice: null,
Nest: null,
Bit: null
Bit: null,
Bitle: null,
};

var aliasRegistry = {};
Expand Down Expand Up @@ -100,6 +101,14 @@ BIT_RANGE.forEach(function(i) {
options.length = i;
return this.setNextParser("bit", varName, options);
};

Parser.prototype["bitle" + i.toString()] = function(varName, options) {
if (!options) {
options = {};
}
options.length = i;
return this.setNextParser("bitle", varName, options);
};
});

Parser.prototype.namely = function(alias) {
Expand Down Expand Up @@ -487,17 +496,17 @@ Parser.prototype.generateBit = function(ctx) {
ctx.pushCode("var {0} = buffer.readUInt8(offset);", val);
sum = 8;
} else if (sum <= 16) {
ctx.pushCode("var {0} = buffer.readUInt16BE(offset);", val);
ctx.pushCode(`var {0} = buffer.readUInt16BE(offset);`, val);
sum = 16;
} else if (sum <= 24) {
var val1 = ctx.generateTmpVariable();
var val2 = ctx.generateTmpVariable();
ctx.pushCode("var {0} = buffer.readUInt16BE(offset);", val1);
ctx.pushCode(`var {0} = buffer.readUInt16BE(offset);`, val1);
ctx.pushCode("var {0} = buffer.readUInt8(offset + 2);", val2);
ctx.pushCode("var {2} = ({0} << 8) | {1};", val1, val2, val);
sum = 24;
} else if (sum <= 32) {
ctx.pushCode("var {0} = buffer.readUInt32BE(offset);", val);
ctx.pushCode(`var {0} = buffer.readUInt32BE(offset);`, val);
sum = 32;
} else {
throw new Error(
Expand All @@ -523,6 +532,62 @@ Parser.prototype.generateBit = function(ctx) {
}
};

Parser.prototype.generateBitle = function(ctx) {
// TODO find better method to handle nested bit fields
var parser = JSON.parse(JSON.stringify(this));
parser.varName = ctx.generateVariable(parser.varName);
ctx.bitFields.push(parser);

if (
!this.next ||
(this.next && ["Bitle", "Nest"].indexOf(this.next.type) < 0)
) {
var sum = 0;
ctx.bitFields.forEach(function(parser) {
sum += parser.options.length;
});

var val = ctx.generateTmpVariable();

if (sum <= 8) {
ctx.pushCode("var {0} = buffer.readUInt8(offset);", val);
sum = 8;
} else if (sum <= 16) {
ctx.pushCode(`var {0} = buffer.readUInt16LE(offset);`, val);
sum = 16;
} else if (sum <= 24) {
var val1 = ctx.generateTmpVariable();
var val2 = ctx.generateTmpVariable();
ctx.pushCode(`var {0} = buffer.readUInt16LE(offset);`, val1);
ctx.pushCode("var {0} = buffer.readUInt8(offset + 2);", val2);
ctx.pushCode("var {2} = ({0} << 8) | {1};", val1, val2, val);
sum = 24;
} else if (sum <= 32) {
ctx.pushCode(`var {0} = buffer.readUInt32LE(offset);`, val);
sum = 32;
} else {
throw new Error(
"Currently, bit field sequence longer than 4-bytes is not supported."
);
}
ctx.pushCode("offset += {0};", sum / 8);

var bitOffset = 0;
ctx.bitFields.forEach(function(parser) {
ctx.pushCode(
"{0} = {1} >> {2} & {3};",
parser.varName,
val,
bitOffset,
(1 << parser.options.length) - 1
);
bitOffset += parser.options.length;
});

ctx.bitFields = [];
}
};

Parser.prototype.generateSkip = function(ctx) {
var length = ctx.generateOption(this.options.length);
ctx.pushCode("offset += {0};", length);
Expand Down Expand Up @@ -739,7 +804,7 @@ Parser.prototype.generateFormatter = function(ctx, varName, formatter) {
};

Parser.prototype.isInteger = function() {
return !!this.type.match(/U?Int[8|16|32][BE|LE]?|Bit\d+/);
return !!this.type.match(/U?Int[8|16|32][BE|LE]?|Bit\d+|Bitle\d+/);
};

//========================================================================================
Expand Down