web3.js/lib/solidity/type.js

var f = require('./formatters');
var SolidityParam = require('./param');

/**
 * SolidityType prototype is used to encode/decode solidity params of certain type
 */
var SolidityType = function (config) {
    this._inputFormatter = config.inputFormatter;
    this._outputFormatter = config.outputFormatter;
};

/**
 * Should be used to determine if this SolidityType do match given name
 *
 * @method isType
 * @param {String} name
 * @return {Bool} true if type match this SolidityType, otherwise false
 */
SolidityType.prototype.isType = function (name) {
    throw "this method should be overrwritten for type " + name;
};

/**
 * Should be used to determine what is the length of static part in given type
 *
 * @method staticPartLength
 * @param {String} name
 * @return {Number} length of static part in bytes
 */
SolidityType.prototype.staticPartLength = function (name) {
    throw "this method should be overrwritten for type: " + name;
};

/**
 * Should be used to determine if type is dynamic array
 * eg: 
 * "type[]" => true
 * "type[4]" => false
 *
 * @method isDynamicArray
 * @param {String} name
 * @return {Bool} true if the type is dynamic array 
 */
SolidityType.prototype.isDynamicArray = function (name) {
    var nestedTypes = this.nestedTypes(name);
    return !!nestedTypes && !nestedTypes[nestedTypes.length - 1].match(/[0-9]{1,}/g);
};

/**
 * Should be used to determine if type is static array
 * eg: 
 * "type[]" => false
 * "type[4]" => true
 *
 * @method isStaticArray
 * @param {String} name
 * @return {Bool} true if the type is static array 
 */
SolidityType.prototype.isStaticArray = function (name) {
    var nestedTypes = this.nestedTypes(name);
    return !!nestedTypes && !!nestedTypes[nestedTypes.length - 1].match(/[0-9]{1,}/g);
};

/**
 * Should return length of static array
 * eg. 
 * "int[32]" => 32
 * "int256[14]" => 14
 * "int[2][3]" => 3
 * "int" => 1
 * "int[1]" => 1
 * "int[]" => 1
 *
 * @method staticArrayLength
 * @param {String} name
 * @return {Number} static array length
 */
SolidityType.prototype.staticArrayLength = function (name) {
    var nestedTypes = this.nestedTypes(name);
    if (nestedTypes) {
       return parseInt(nestedTypes[nestedTypes.length - 1].match(/[0-9]{1,}/g) || 1);
    }
    return 1;
};

/**
 * Should return nested type
 * eg.
 * "int[32]" => "int"
 * "int256[14]" => "int256"
 * "int[2][3]" => "int[2]"
 * "int" => "int"
 * "int[]" => "int"
 *
 * @method nestedName
 * @param {String} name
 * @return {String} nested name
 */
SolidityType.prototype.nestedName = function (name) {
    // remove last [] in name
    var nestedTypes = this.nestedTypes(name);
    if (!nestedTypes) {
        return name;
    }

    return name.substr(0, name.length - nestedTypes[nestedTypes.length - 1].length);
};

/**
 * Should return true if type has dynamic size by default
 * such types are "string", "bytes"
 *
 * @method isDynamicType
 * @param {String} name
 * @return {Bool} true if is dynamic, otherwise false
 */
SolidityType.prototype.isDynamicType = function () {
    return false;
};

/**
 * Should return array of nested types
 * eg.
 * "int[2][3][]" => ["[2]", "[3]", "[]"]
 * "int[] => ["[]"]
 * "int" => null
 *
 * @method nestedTypes
 * @param {String} name
 * @return {Array} array of nested types
 */
SolidityType.prototype.nestedTypes = function (name) {
    // return list of strings eg. "[]", "[3]", "[]", "[2]"
    return name.match(/(\[[0-9]*\])/g);
};

/**
 * Should be used to encode the value
 *
 * @method encode
 * @param {Object} value 
 * @param {String} name
 * @return {String} encoded value
 */
SolidityType.prototype.encode = function (value, name) {
    var self = this;
    if (this.isDynamicArray(name)) {

        return (function () {
            var length = value.length;                          // in int
            var nestedName = self.nestedName(name);

            var result = [];
            result.push(f.formatInputInt(length).encode());
            
            value.forEach(function (v) {
                result.push(self.encode(v, nestedName));
            });

            return result;
        })();

    } else if (this.isStaticArray(name)) {

        return (function () {
            var length = self.staticArrayLength(name);          // in int
            var nestedName = self.nestedName(name);

            var result = [];
            for (var i = 0; i < length; i++) {
                result.push(self.encode(value[i], nestedName));
            }

            return result;
        })();

    }

    return this._inputFormatter(value, name).encode();
};

/**
 * Should be used to decode value from bytes
 *
 * @method decode
 * @param {String} bytes
 * @param {Number} offset in bytes
 * @param {String} name type name
 * @returns {Object} decoded value
 */
SolidityType.prototype.decode = function (bytes, offset, name) {
    var self = this;

    if (this.isDynamicArray(name)) {

        return (function () {
            var arrayOffset = parseInt('0x' + bytes.substr(offset * 2, 64)); // in bytes
            var length = parseInt('0x' + bytes.substr(arrayOffset * 2, 64)); // in int
            var arrayStart = arrayOffset + 32; // array starts after length; // in bytes

            var nestedName = self.nestedName(name);
            var nestedStaticPartLength = self.staticPartLength(nestedName);  // in bytes
            var result = [];

            for (var i = 0; i < length * nestedStaticPartLength; i += nestedStaticPartLength) {
                result.push(self.decode(bytes, arrayStart + i, nestedName));
            }

            return result;
        })();

    } else if (this.isStaticArray(name)) {

        return (function () {
            var length = self.staticArrayLength(name);                      // in int
            var arrayStart = offset;                                        // in bytes

            var nestedName = self.nestedName(name);
            var nestedStaticPartLength = self.staticPartLength(nestedName); // in bytes
            var result = [];

            for (var i = 0; i < length * nestedStaticPartLength; i += nestedStaticPartLength) {
                result.push(self.decode(bytes, arrayStart + i, nestedName));
            }

            return result;
        })();
    } else if (this.isDynamicType(name)) {
        
        return (function () {
            var dynamicOffset = parseInt('0x' + bytes.substr(offset * 2, 64));      // in bytes
            var length = parseInt('0x' + bytes.substr(dynamicOffset * 2, 64));      // in bytes
            var roundedLength = Math.floor((length + 31) / 32);                     // in int
        
            return self._outputFormatter(new SolidityParam(bytes.substr(dynamicOffset * 2, ( 1 + roundedLength) * 64), 0));
        })();
    }

    var length = this.staticPartLength(name);
    return this._outputFormatter(new SolidityParam(bytes.substr(offset * 2, length * 2)));
};

module.exports = SolidityType;