226 lines
7.2 KiB
HTML
226 lines
7.2 KiB
HTML
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<title>JSDoc: Source: structs.js</title>
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<h1 class="page-title">Source: structs.js</h1>
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<section>
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<article>
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<pre class="prettyprint source linenums"><code>/**
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* Implements common structures.
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* @see {@link https://bitmessage.org/wiki/Protocol_specification#Common_structures}
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* @module bitmessage/structs
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*/
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"use strict";
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var assert = require("assert");
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/**
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* var_int.
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* @see {@link https://bitmessage.org/wiki/Protocol_specification#Variable_length_integer}
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* @namespace
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* @static
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*/
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var var_int = exports.var_int = {
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/**
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* Decode var_int.
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* @param {Buffer} buf - A buffer that starts with encoded var_int
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* @return {{value: number, length: number, rest: Buffer}}
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* Decoded var_int structure.
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*/
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decode: function(buf) {
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var value, length;
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assert(buf.length > 0, "Empty buffer");
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switch (buf[0]) {
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case 253:
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value = buf.readUInt16BE(1);
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assert(value >= 253, "Impractical var_int");
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length = 3;
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break;
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case 254:
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value = buf.readUInt32BE(1);
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assert(value >= 65536, "Impractical var_int");
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length = 5;
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break;
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case 255:
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var hi = buf.readUInt32BE(1);
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assert(hi !== 0, "Impractical var_int");
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// Max safe number = 2^53 - 1 =
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// 0b0000000000011111111111111111111111111111111111111111111111111111
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// = 2097151*(2^32) + (2^32 - 1).
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// So it's safe until hi <= 2097151. See
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// <http://mdn.io/issafeinteger>,
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// <https://stackoverflow.com/q/307179> for details.
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// TODO(Kagami): We may want to return raw Buffer for
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// 2^53 <= value <= 2^64 - 1 range. Possibly using the optional
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// argument because most of the code expect to get a number when
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// calling `var_int.decode`.
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assert(hi <= 2097151, "Unsafe integer");
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var lo = buf.readUInt32BE(5);
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value = hi * 4294967296 + lo;
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length = 9;
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break;
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default:
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value = buf[0];
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length = 1;
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}
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var rest = buf.slice(length);
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return {value: value, length: length, rest: rest};
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},
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/**
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* Encode number into var_int.
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* @param {(number|Buffer)} value - Input number
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* @return {Buffer} Encoded var_int.
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*/
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encode: function(value) {
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var buf, targetStart;
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if (typeof value === "number") {
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assert(value >= 0, "Value cannot be less than zero");
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if (value < 253) {
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buf = new Buffer([value]);
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} else if (value < 65536) {
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buf = new Buffer(3);
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buf[0] = 253;
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buf.writeUInt16BE(value, 1, true);
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} else if (value < 4294967296) {
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buf = new Buffer(5);
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buf[0] = 254;
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buf.writeUInt32BE(value, 1, true);
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} else {
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assert(value <= 9007199254740991, "Unsafe integer");
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buf = new Buffer(9);
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buf[0] = 255;
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buf.writeUInt32BE(Math.floor(value / 4294967296), 1, true); // high32
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buf.writeUInt32BE(value % 4294967296, 5, true); // low32
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}
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} else if (Buffer.isBuffer(value)) {
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assert(value.length <= 8, "Buffer is too big");
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buf = new Buffer(9);
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buf.fill(0);
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buf[0] = 255;
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targetStart = 1 + (8 - value.length);
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value.copy(buf, targetStart);
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} else {
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throw new Error("Value encode error");
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}
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return buf;
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},
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};
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/**
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* var_str.
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* @see {@link https://bitmessage.org/wiki/Protocol_specification#Variable_length_string}
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* @namespace
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*/
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exports.var_str = {
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/**
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* Decode var_str.
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* @param {Buffer} buf - A buffer that starts with encoded var_str
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* @return {{str: string, length: number, rest: Buffer}}
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* Decoded var_str structure.
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*/
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decode: function(buf) {
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var decoded = var_int.decode(buf);
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var strLength = decoded.value;
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// XXX(Kagami): Spec doesn't mention encoding, using UTF-8.
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var str = decoded.rest.slice(0, strLength).toString();
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var rest = decoded.rest.slice(strLength);
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return {str: str, length: decoded.length + strLength, rest: rest};
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},
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/**
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* Encode string into var_str.
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* @param {string} str - A string
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* @return {Buffer} Encoded var_str.
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*/
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encode: function(str) {
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// XXX(Kagami): Spec doesn't mention encoding, using UTF-8.
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var strBuf = new Buffer(str);
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return Buffer.concat([var_int.encode(strBuf.length), strBuf]);
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},
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};
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/**
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* var_int_list.
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* @see {@link https://bitmessage.org/wiki/Protocol_specification#Variable_length_list_of_integers}
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* @namespace
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*/
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exports.var_int_list = {
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/**
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* Decode var_int_list.
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* @param {Buffer} buf - A buffer that starts with encoded
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* var_int_list
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* @return {{list: number[], length: number, rest: Buffer}}
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* Decoded var_int_list structure.
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*/
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decode: function(buf) {
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var decoded = var_int.decode(buf);
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var listLength = decoded.value;
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var list = new Array(listLength);
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var rest = decoded.rest;
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var sumLength = decoded.length;
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for (var i = 0; i < listLength; i++) {
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decoded = var_int.decode(rest);
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list[i] = decoded.value;
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rest = decoded.rest;
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sumLength += decoded.length;
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}
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return {list: list, length: sumLength, rest: rest};
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},
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/**
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* Encode list of numbers into var_int_list.
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* @param {number[]} list - A number list
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* @return {Buffer} Encoded var_int_list.
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*/
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encode: function(list) {
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var listBuf = Buffer.concat(list.map(var_int.encode));
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return Buffer.concat([var_int.encode(list.length), listBuf]);
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},
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};
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</code></pre>
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</article>
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</section>
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</div>
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<nav>
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<h2><a href="index.html">Home</a></h2><h3>Modules</h3><ul><li><a href="module-bitmessage.html">bitmessage</a></li><li><a href="module-bitmessage_address.html">bitmessage/address</a></li><li><a href="module-bitmessage_crypto.html">bitmessage/crypto</a></li><li><a href="module-bitmessage_messages.html">bitmessage/messages</a></li><li><a href="module-bitmessage_objects.html">bitmessage/objects</a></li><li><a href="module-bitmessage_pow.html">bitmessage/pow</a></li><li><a href="module-bitmessage_structs.html">bitmessage/structs</a></li><li><a href="module-bitmessage_wif.html">bitmessage/wif</a></li></ul><h3>Classes</h3><ul><li><a href="module-bitmessage_address.Address.html">Address</a></li></ul><h3>Namespaces</h3><ul><li><a href="module-bitmessage_structs.var_int.html">var_int</a></li><li><a href="module-bitmessage_structs.var_int_list.html">var_int_list</a></li><li><a href="module-bitmessage_structs.var_str.html">var_str</a></li></ul>
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Documentation generated by <a href="https://github.com/jsdoc3/jsdoc">JSDoc 3.3.0-alpha13</a> on Sat Jan 03 2015 19:33:03 GMT+0300 (MSK)
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