8e959426e2
Javascript only supports 64 bit floating points, which have uint precision up to Math.pow(2, 53). We now support reading variable sized numbers up to that size. If the number is bigger than that, then we need to use BN.
124 lines
2.9 KiB
JavaScript
124 lines
2.9 KiB
JavaScript
var BN = require('./bn');
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var BufferReader = function BufferReader(buf) {
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if (!(this instanceof BufferReader))
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return new BufferReader(buf);
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if (Buffer.isBuffer(buf)) {
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this.set({buf: buf});
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}
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else if (buf) {
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var obj = buf;
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this.set(obj);
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}
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};
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BufferReader.prototype.set = function(obj) {
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this.buf = obj.buf || this.buf || undefined;
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this.pos = obj.pos || this.pos || 0;
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return this;
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};
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BufferReader.prototype.eof = function() {
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return this.pos >= this.buf.length;
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};
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BufferReader.prototype.buffer = function(len) {
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var buf = this.buf.slice(this.pos, this.pos + len);
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this.pos = this.pos + len;
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return buf;
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};
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BufferReader.prototype.read = function() {
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var buf = this.buf.slice(this.pos);
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this.pos = this.buf.length;
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return buf;
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};
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BufferReader.prototype.readUInt8 = function() {
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var val = this.buf.readUInt8(this.pos);
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this.pos = this.pos + 1;
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return val;
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};
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BufferReader.prototype.readUInt16BE = function() {
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var val = this.buf.readUInt16BE(this.pos);
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this.pos = this.pos + 2;
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return val;
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};
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BufferReader.prototype.readUInt16LE = function() {
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var val = this.buf.readUInt16LE(this.pos);
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this.pos = this.pos + 2;
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return val;
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};
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BufferReader.prototype.readUInt32BE = function() {
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var val = this.buf.readUInt32BE(this.pos);
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this.pos = this.pos + 4;
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return val;
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};
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BufferReader.prototype.readUInt32LE = function() {
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var val = this.buf.readUInt32LE(this.pos);
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this.pos = this.pos + 4;
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return val;
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};
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BufferReader.prototype.readUInt64BEBN = function() {
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var buf = this.buf.slice(this.pos, this.pos + 8);
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var bn = BN().fromBuffer(buf);
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this.pos = this.pos + 8;
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return bn;
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};
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BufferReader.prototype.readUInt64LEBN = function() {
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var buf = this.buf.slice(this.pos, this.pos + 8);
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var reversebuf = BufferReader({buf: buf}).reverse().read();
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var bn = BN().fromBuffer(reversebuf);
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this.pos = this.pos + 8;
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return bn;
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};
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BufferReader.prototype.readVarInt = function() {
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var first = this.readUInt8();
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switch (first) {
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case 0xFD:
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return this.readUInt16LE();
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case 0xFE:
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return this.readUInt32LE();
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case 0xFF:
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var bn = this.readUInt64LEBN();
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var n = bn.toNumber();
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if (n <= Math.pow(2, 53))
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return n;
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else
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throw new Error('number too large to retain precision - use readVarIntBN');
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default:
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return first;
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}
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};
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BufferReader.prototype.readVarIntBN = function() {
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var first = this.readUInt8();
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switch (first) {
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case 0xFD:
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return BN(this.readUInt16LE());
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case 0xFE:
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return BN(this.readUInt32LE());
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case 0xFF:
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return this.readUInt64LEBN();
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default:
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return BN(first);
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}
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};
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BufferReader.prototype.reverse = function() {
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var buf = new Buffer(this.buf.length);
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for (var i = 0; i < buf.length; i++)
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buf[i] = this.buf[this.buf.length - 1 - i]
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this.buf = buf;
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return this;
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};
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module.exports = BufferReader;
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