abi.js

// Extracted from https://github.com/ethereumjs/ethereumjs-abi and stripped out irrelevant code
// Original code licensed under the MIT License - Copyright (c) 2015 Alex Beregszaszi

const util = require('./util')
const BN = require('bn.js')
const Buffer = require('buffer/').Buffer

// Convert from short to canonical names
// FIXME: optimise or make this nicer?
function elementaryName (name) {
  if (name.startsWith('int[')) {
    return 'int256' + name.slice(3)
  } else if (name === 'int') {
    return 'int256'
  } else if (name.startsWith('uint[')) {
    return 'uint256' + name.slice(4)
  } else if (name === 'uint') {
    return 'uint256'
  } else if (name.startsWith('fixed[')) {
    return 'fixed128x128' + name.slice(5)
  } else if (name === 'fixed') {
    return 'fixed128x128'
  } else if (name.startsWith('ufixed[')) {
    return 'ufixed128x128' + name.slice(6)
  } else if (name === 'ufixed') {
    return 'ufixed128x128'
  }
  return name
}

// Parse N from type<N>
function parseTypeN (type) {
  return parseInt(/^\D+(\d+)$/.exec(type)[1], 10)
}

// Parse N,M from type<N>x<M>
function parseTypeNxM (type) {
  var tmp = /^\D+(\d+)x(\d+)$/.exec(type)
  return [ parseInt(tmp[1], 10), parseInt(tmp[2], 10) ]
}

// Parse N in type[<N>] where "type" can itself be an array type.
function parseTypeArray (type) {
  var tmp = type.match(/(.*)\[(.*?)\]$/)
  if (tmp) {
    return tmp[2] === '' ? 'dynamic' : parseInt(tmp[2], 10)
  }
  return null
}

function parseNumber (arg) {
  var type = typeof arg
  if (type === 'string') {
    if (util.isHexString(arg)) {
      return new BN(util.stripHexPrefix(arg), 16)
    } else {
      return new BN(arg, 10)
    }
  } else if (type === 'number') {
    return new BN(arg)
  } else if (arg.toArray) {
    // assume this is a BN for the moment, replace with BN.isBN soon
    return arg
  } else {
    throw new Error('Argument is not a number')
  }
}

// Encodes a single item (can be dynamic array)
// @returns: Buffer
function encodeSingle (type, arg) {
  var size, num, ret, i

  if (type === 'address') {
    return encodeSingle('uint160', parseNumber(arg))
  } else if (type === 'bool') {
    return encodeSingle('uint8', arg ? 1 : 0)
  } else if (type === 'string') {
    return encodeSingle('bytes', new Buffer(arg, 'utf8'))
  } else if (isArray(type)) {
    // this part handles fixed-length ([2]) and variable length ([]) arrays
    // NOTE: we catch here all calls to arrays, that simplifies the rest
    if (typeof arg.length === 'undefined') {
      throw new Error('Not an array?')
    }
    size = parseTypeArray(type)
    if (size !== 'dynamic' && size !== 0 && arg.length > size) {
      throw new Error('Elements exceed array size: ' + size)
    }
    ret = []
    type = type.slice(0, type.lastIndexOf('['))
    if (typeof arg === 'string') {
      arg = JSON.parse(arg)
    }
    for (i in arg) {
      ret.push(encodeSingle(type, arg[i]))
    }
    if (size === 'dynamic') {
      var length = encodeSingle('uint256', arg.length)
      ret.unshift(length)
    }
    return Buffer.concat(ret)
  } else if (type === 'bytes') {
    arg = new Buffer(arg)

    ret = Buffer.concat([ encodeSingle('uint256', arg.length), arg ])

    if ((arg.length % 32) !== 0) {
      ret = Buffer.concat([ ret, util.zeros(32 - (arg.length % 32)) ])
    }

    return ret
  } else if (type.startsWith('bytes')) {
    size = parseTypeN(type)
    if (size < 1 || size > 32) {
      throw new Error('Invalid bytes<N> width: ' + size)
    }

    return util.setLengthRight(arg, 32)
  } else if (type.startsWith('uint')) {
    size = parseTypeN(type)
    if ((size % 8) || (size < 8) || (size > 256)) {
      throw new Error('Invalid uint<N> width: ' + size)
    }

    num = parseNumber(arg)
    if (num.bitLength() > size) {
      throw new Error('Supplied uint exceeds width: ' + size + ' vs ' + num.bitLength())
    }

    if (num < 0) {
      throw new Error('Supplied uint is negative')
    }

    return num.toArrayLike(Buffer, 'be', 32)
  } else if (type.startsWith('int')) {
    size = parseTypeN(type)
    if ((size % 8) || (size < 8) || (size > 256)) {
      throw new Error('Invalid int<N> width: ' + size)
    }

    num = parseNumber(arg)
    if (num.bitLength() > size) {
      throw new Error('Supplied int exceeds width: ' + size + ' vs ' + num.bitLength())
    }

    return num.toTwos(256).toArrayLike(Buffer, 'be', 32)
  } else if (type.startsWith('ufixed')) {
    size = parseTypeNxM(type)

    num = parseNumber(arg)

    if (num < 0) {
      throw new Error('Supplied ufixed is negative')
    }

    return encodeSingle('uint256', num.mul(new BN(2).pow(new BN(size[1]))))
  } else if (type.startsWith('fixed')) {
    size = parseTypeNxM(type)

    return encodeSingle('int256', parseNumber(arg).mul(new BN(2).pow(new BN(size[1]))))
  }

  throw new Error('Unsupported or invalid type: ' + type)
}

// Is a type dynamic?
function isDynamic (type) {
  // FIXME: handle all types? I don't think anything is missing now
  return (type === 'string') || (type === 'bytes') || (parseTypeArray(type) === 'dynamic')
}

// Is a type an array?
function isArray (type) {
  return type.lastIndexOf(']') === type.length - 1
}

// Encode a method/event with arguments
// @types an array of string type names
// @args  an array of the appropriate values
function rawEncode (types, values) {
  var output = []
  var data = []

  var headLength = 32 * types.length

  for (var i in types) {
    var type = elementaryName(types[i])
    var value = values[i]
    var cur = encodeSingle(type, value)

    // Use the head/tail method for storing dynamic data
    if (isDynamic(type)) {
      output.push(encodeSingle('uint256', headLength))
      data.push(cur)
      headLength += cur.length
    } else {
      output.push(cur)
    }
  }

  return Buffer.concat(output.concat(data))
}

function solidityPack (types, values) {
  if (types.length !== values.length) {
    throw new Error('Number of types are not matching the values')
  }

  var size, num
  var ret = []

  for (var i = 0; i < types.length; i++) {
    var type = elementaryName(types[i])
    var value = values[i]

    if (type === 'bytes') {
      ret.push(value)
    } else if (type === 'string') {
      ret.push(new Buffer(value, 'utf8'))
    } else if (type === 'bool') {
      ret.push(new Buffer(value ? '01' : '00', 'hex'))
    } else if (type === 'address') {
      ret.push(util.setLength(value, 20))
    } else if (type.startsWith('bytes')) {
      size = parseTypeN(type)
      if (size < 1 || size > 32) {
        throw new Error('Invalid bytes<N> width: ' + size)
      }

      ret.push(util.setLengthRight(value, size))
    } else if (type.startsWith('uint')) {
      size = parseTypeN(type)
      if ((size % 8) || (size < 8) || (size > 256)) {
        throw new Error('Invalid uint<N> width: ' + size)
      }

      num = parseNumber(value)
      if (num.bitLength() > size) {
        throw new Error('Supplied uint exceeds width: ' + size + ' vs ' + num.bitLength())
      }

      ret.push(num.toArrayLike(Buffer, 'be', size / 8))
    } else if (type.startsWith('int')) {
      size = parseTypeN(type)
      if ((size % 8) || (size < 8) || (size > 256)) {
        throw new Error('Invalid int<N> width: ' + size)
      }

      num = parseNumber(value)
      if (num.bitLength() > size) {
        throw new Error('Supplied int exceeds width: ' + size + ' vs ' + num.bitLength())
      }

      ret.push(num.toTwos(size).toArrayLike(Buffer, 'be', size / 8))
    } else {
      // FIXME: support all other types
      throw new Error('Unsupported or invalid type: ' + type)
    }
  }

  return Buffer.concat(ret)
}

function soliditySHA3 (types, values) {
  return util.keccak(solidityPack(types, values))
}

module.exports = {
  rawEncode,
  solidityPack,
  soliditySHA3
}