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112 lines
2.0 KiB
112 lines
2.0 KiB
math = require("math")
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module.exports = {
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decode_string: decode_string,
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decode_varint: decode_varint,
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encode_big_endian: encode_big_endian,
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encode: encode,
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reverse: reverse,
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}
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function reverse(buf){
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for (var i = 0; i < buf.length/2; i++){
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a = buf[i];
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b = buf[buf.length-1 - i];
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buf[i] = b;
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buf[buf.length-1 - i] = a;
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}
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return buf
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}
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function uvarint_size(i){
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if (i == 0){
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return 0
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}
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for(var j = 1; j < 9; j++) {
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if ( i < 1<<j*8 ) {
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return j
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}
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}
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return 8
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}
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function encode_big_endian(i, size){
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if (size == 0){
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return new Buffer(0);
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}
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b = encode_big_endian(math.floor(i/256), size-1);
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return Buffer.concat([b, new Buffer([i%256])]);
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}
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function decode_big_endian(reader, size){
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if (size == 0){ return 0 }
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firstByte = reader.read(1)[0];
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return firstByte*(math.pow(256, size-1)) + decode_big_endian(reader, size-1)
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}
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function encode_string(s){
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size = encode_varint(s.length);
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return Buffer.concat([size, new Buffer(s)])
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}
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function decode_string(reader){
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length = decode_varint(reader);
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return reader.read(length).toString()
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}
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function encode_varint(i){
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var negate = false;
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if (i < 0){
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negate = true;
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i = -i;
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}
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size = uvarint_size(i);
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if (size == 0){
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return new Buffer([0])
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}
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big_end = encode_big_endian(i, size);
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if (negate){ size += 0xF0 }
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var buf = new Buffer([1]);
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return Buffer.concat([buf, big_end])
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}
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function decode_varint(reader){
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size = reader.read(1)[0];
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if (size == 0 ){
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return 0
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}
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var negate = false;
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if (size > 0xF0){ negate = true }
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if (negate) { size = size - 0xF0 }
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i = decode_big_endian(reader, size);
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if (negate) { i = i * -1}
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return i
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}
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function encode_list(l){
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var l2 = l.map(encode);
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var buf = new Buffer(encode_varint(l2.length));
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return Buffer.concat([buf, Buffer.concat(l2)]);
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}
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function encode(b){
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if (b == null){
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return Buffer(0)
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} else if (typeof b == "number"){
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return encode_varint(b)
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} else if (typeof b == "string"){
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return encode_string(b)
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} else if (Array.isArray(b)){
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return encode_list(b)
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} else{
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console.log("UNSUPPORTED TYPE!", typeof b, b)
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}
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}
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