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Module for encoding/decoding Bencoded data
このスクリプトは単体で利用できません。右のようなメタデータを含むスクリプトから、ライブラリとして読み込まれます: // @require https://update.greasyfork.org/scripts/13016/79776/Bencode%20encoderdecoder.js
// ==UserScript==
// @name Bencode encoder/decoder
// @description Module for encoding/decoding Bencoded data
// @version 1.0
// ==/UserScript==
// Copyright: https://github.com/nutbread/t2m
var bencode = (function() {
"use strict";
// Encoding functions
var encode = function (value) {
// Type
var t = typeof(value);
// Number
if (t == "number") return encode_int(Math.floor(value));
// String
if (t == "string") return encode_string(value);
// Array
if (Array.isArray(value)) return encode_list(value);
// Dict
return encode_dict(value);
};
var encode_int = function (value) {
return "i" + value + "e";
};
var encode_string = function (value) {
return "" + value.length + ":" + value;
};
var encode_list = function (value) {
var str = [ "l" ],
i;
// List values
for (i = 0; i < value.length; ++i) {
str.push(encode(value[i]));
}
// End
str.push("e");
return str.join("");
};
var encode_dict = function (value) {
var str = [ "d" ],
keys = [],
i;
// Get and sort keys
for (i in value) keys.push(i);
keys.sort();
// Push values
for (i = 0; i < keys.length; ++i) {
str.push(encode_string(keys[i]));
str.push(encode(value[keys[i]]));
}
// End
str.push("e");
return str.join("");
};
// Decoding class
var Decoder = function () {
this.pos = 0;
};
Decoder.prototype = {
constructor: Decoder,
decode: function (str) {
// Errors
var k = str[this.pos];
if (!(k in decode_generic)) throw "Invalid format";
// Call
return decode_generic[k].call(this, str);
},
decode_int: function (str) {
// Skip the "i" prefix
++this.pos;
var end = str.indexOf("e", this.pos),
value;
// No end
if (end < 0) throw "Invalid format";
// Assume proper number format
value = parseInt(str.substr(this.pos, end - this.pos), 10);
// Done
this.pos = end + 1;
return value;
},
decode_string: function (str) {
var delim = str.indexOf(":", this.pos),
length, value;
// No end
if (delim < 0) throw "Invalid format";
// Assume proper number format
length = parseInt(str.substr(this.pos, delim - this.pos), 10);
value = str.substr(delim + 1, length);
// Done
this.pos = delim + length + 1;
return value;
},
decode_list: function (str) {
// Skip the "l" prefix
++this.pos;
// Read list
var list = [],
value;
// Loop until end or exception
while (str[this.pos] != "e") {
value = this.decode(str); // this throws errors if str[this.pos] is out of bounds
list.push(value);
}
// Done; skip "e" suffix
++this.pos;
return list;
},
decode_dict: function (str) {
// Skip the "d" prefix
++this.pos;
// Read dict
var dict = {},
key, value;
// Loop until end or exception
while (str[this.pos] != "e") {
key = this.decode_string(str);
value = this.decode(str); // this throws errors if str[this.pos] is out of bounds
dict[key] = value;
}
// Done; skip "e" suffix
++this.pos;
return dict;
}
};
// Generic decode functions
var decode_generic = {
"l": Decoder.prototype.decode_list,
"d": Decoder.prototype.decode_dict,
"i": Decoder.prototype.decode_int,
},
i;
for (i = 0; i < 10; ++i) decode_generic[i.toString()] = Decoder.prototype.decode_string;
// Encode/decode functions
return {
/**
encode: function (obj)
Encodes an object into a Bencode'd string
@param obj
The object to encode
This should only be one of the following:
string
number (floats are floor'd to integers)
array (containing things only from this list)
object (containing things only from this list)
Strings should be encoded in some way such that each character is in the range [0,255]
@return
A string representing the object
*/
encode: encode,
/**
decode: function (str)
Decodes a Bencode'd string back into its original type
@param str
The string to decode
@return
The original object represented by str
@throws
Any one of the following self-explanatory strings
"Invalid format"
"Invalid string"
"Invalid int"
*/
decode: function (str) {
// Create a decoder and call
return (new Decoder()).decode(str);
},
};
})();