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endian_aware_dataview.js
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// we want an endian aware dataview mostly because ARM can be big-endian, and
// that might put us in trouble wrt handheld devices.
//////////////////////////////////////////////////////////////////////////////
(function() {
var _is_little_endian;
(function() {
var x = new ArrayBuffer(4);
var bytes = new Uint8Array(x),
words = new Uint32Array(x);
bytes[0] = 1;
if (words[0] === 1) {
_is_little_endian = true;
} else if (words[0] === 16777216) {
_is_little_endian = false;
} else {
throw "we're bizarro endian, refusing to continue";
}
})();
Rserve.EndianAwareDataView = (function() {
var proto = {
'setInt8': function(i, v) { return this.view.setInt8(i, v); },
'setUint8': function(i, v) { return this.view.setUint8(i, v); },
'getInt8': function(i) { return this.view.getInt8(i); },
'getUint8': function(i) { return this.view.getUint8(i); }
};
var setters = ['setInt32', 'setInt16', 'setUint32', 'setUint16',
'setFloat32', 'setFloat64'];
var getters = ['getInt32', 'getInt16', 'getUint32', 'getUint16',
'getFloat32', 'getFloat64'];
for (var i=0; i<setters.length; ++i) {
var name = setters[i];
proto[name]= (function(name) {
return function(byteOffset, value) {
return this.view[name](byteOffset, value, _is_little_endian);
};
})(name);
}
for (i=0; i<getters.length; ++i) {
var name = getters[i];
proto[name]= (function(name) {
return function(byteOffset) {
return this.view[name](byteOffset, _is_little_endian);
};
})(name);
}
function my_dataView(buffer, byteOffset, byteLength) {
if (byteOffset === undefined) {
// work around node.js bug https://github.com/joyent/node/issues/6051
if (buffer.byteLength === 0) {
this.view = {
byteLength: 0, byteOffset: 0
};
} else
this.view = new DataView(buffer);
} else {
this.view = new DataView(buffer, byteOffset, byteLength);
}
};
my_dataView.prototype = proto;
return my_dataView;
})();
Rserve.my_ArrayBufferView = function(b, o, l) {
o = _.isUndefined(o) ? 0 : o;
l = _.isUndefined(l) ? b.byteLength : l;
return {
buffer: b,
offset: o,
length: l,
data_view: function() {
return new Rserve.EndianAwareDataView(this.buffer, this.offset,
this.buffer.byteLength - this.offset);
},
make: function(ctor, new_offset, new_length) {
new_offset = _.isUndefined(new_offset) ? 0 : new_offset;
new_length = _.isUndefined(new_length) ? this.length : new_length;
var element_size = ctor.BYTES_PER_ELEMENT || 1;
var n_els = new_length / element_size;
if ((this.offset + new_offset) % element_size != 0) {
var view = new DataView(this.buffer, this.offset + new_offset, new_length);
var output_buffer = new ArrayBuffer(new_length);
var out_view = new DataView(output_buffer);
for (var i=0; i < new_length; ++i) {
out_view.setUint8(i, view.getUint8(i));
}
return new ctor(output_buffer);
} else {
return new ctor(this.buffer,
this.offset + new_offset,
n_els);
}
},
skip: function(offset) {
return Rserve.my_ArrayBufferView(
this.buffer, this.offset + offset, this.buffer.byteLength);
},
view: function(new_offset, new_length) {
var ofs = this.offset + new_offset;
if(ofs + new_length > this.buffer.byteLength)
throw new Error("Rserve.my_ArrayBufferView.view: bounds error: size: " +
this.buffer.byteLength + " offset: " + ofs + " length: " + new_length);
return Rserve.my_ArrayBufferView(
this.buffer, ofs, new_length);
}
};
};
})(this);