94 lines
2.0 KiB
JavaScript
94 lines
2.0 KiB
JavaScript
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var util = require('../core').util;
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var toBuffer = require('./to-buffer').toBuffer;
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/**
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* A lossless representation of a signed, 64-bit integer. Instances of this
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* class may be used in arithmetic expressions as if they were numeric
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* primitives, but the binary representation will be preserved unchanged as the
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* `bytes` property of the object. The bytes should be encoded as big-endian,
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* two's complement integers.
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* @param {Buffer} bytes
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*
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* @api private
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*/
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function Int64(bytes) {
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if (bytes.length !== 8) {
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throw new Error('Int64 buffers must be exactly 8 bytes');
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}
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if (!util.Buffer.isBuffer(bytes)) bytes = toBuffer(bytes);
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this.bytes = bytes;
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}
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/**
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* @param {number} number
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* @returns {Int64}
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*
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* @api private
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*/
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Int64.fromNumber = function(number) {
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if (number > 9223372036854775807 || number < -9223372036854775808) {
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throw new Error(
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number + ' is too large (or, if negative, too small) to represent as an Int64'
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);
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}
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var bytes = new Uint8Array(8);
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for (
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var i = 7, remaining = Math.abs(Math.round(number));
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i > -1 && remaining > 0;
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i--, remaining /= 256
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) {
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bytes[i] = remaining;
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}
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if (number < 0) {
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negate(bytes);
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}
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return new Int64(bytes);
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};
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/**
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* @returns {number}
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*
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* @api private
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*/
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Int64.prototype.valueOf = function() {
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var bytes = this.bytes.slice(0);
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var negative = bytes[0] & 128;
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if (negative) {
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negate(bytes);
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}
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return parseInt(bytes.toString('hex'), 16) * (negative ? -1 : 1);
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};
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Int64.prototype.toString = function() {
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return String(this.valueOf());
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};
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/**
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* @param {Buffer} bytes
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*
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* @api private
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*/
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function negate(bytes) {
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for (var i = 0; i < 8; i++) {
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bytes[i] ^= 0xFF;
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}
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for (var i = 7; i > -1; i--) {
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bytes[i]++;
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if (bytes[i] !== 0) {
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break;
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}
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}
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}
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/**
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* @api private
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*/
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module.exports = {
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Int64: Int64
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};
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