integer.coffee

# Public Domain (-) 2012 The Ampify Authors.
# See the Ampify UNLICENSE file for details.

define 'amp', (exports, root) ->

  WORD_SIZE = 30
  DIGIT_BASE = 1 << WORD_SIZE
  DIGIT_MASK = DIGIT_BASE - 1

  HALF_WORD_SIZE = WORD_SIZE / 2
  HALF_DIGIT_BASE = 1 << HALF_WORD_SIZE
  HALF_DIGIT_MASK = HALF_DIGIT_BASE - 1

  INTEGER_CACHE_SIZE = 100
  LOG_BASE_10 = Math.log(10) / Math.LN2

  ceil = Math.ceil
  pow = Math.pow

  integer = (v) ->
    if not (this instanceof integer)
      return new integer v
    switch typeof v
      when "string"
        @c = 2
      when "number"
        if isNaN(v) or not isFinite v
          throw new TypeError "not a valid number: `#{v}`"
        if v <= DIGIT_MASK and v >= -DIGIT_MASK
          v |= 0
          if v >= 0
            if cache and v <= INTEGER_CACHE_SIZE
              return cache[v+INTEGER_CACHE_SIZE]
            @p = true
          else
            if cache and v >= -INTEGER_CACHE_SIZE
              return cache[v+INTEGER_CACHE_SIZE]
            @p = false
            v = -v
          @d = new Int32Array @b = new ArrayBuffer(8), 0, @c = 1
          @d[0] = v
        else if v <= 9007199254740991 and v >= -9007199254740991
          return new integer parseInt(v, 10).toString()
        else
          throw new RangeError 'cannot convert Numbers outside of the 53-bit range'
      else
        throw new TypeError "not a valid number: `#{v}`"
    return

  exports.integer = integer

  integer::toString = ->
    switch @c
      when 1
        if @p
          return @d[0].toString()
        return "-#{@d[0].toString()}"
      when 0
        return "0"
      else
        # Estimate the size of the final string.
        l = @c - 1
        l = ceil(((l * WORD_SIZE) + bitlen(@d[l]))/LOG_BASE_10)
        s = []

        return "size: #{l}"

  cache = (new integer(i) for i in [-INTEGER_CACHE_SIZE..INTEGER_CACHE_SIZE])
  cache[0].c = 0
  exports.cache = cache

  bitlen = (w) ->
    n = 0
    if w >= 32768
      w >>= 16
      n += 16
    if w >= 128
      w >>= 8
      n += 8
    if w >= 8
      w >>= 4
      n += 4
    if w >= 2
      w >>= 2
      n += 2
    if w >= 1
      n++
    return n

  exports.foo = foo = new integer(12884901762)
  foo.c = 2
  foo.b = new ArrayBuffer(8)
  foo.d = new Int32Array(foo.b, 0, 2)
  foo.d[0] = 1073741698
  foo.d[1] = 11

  integer::toNumber = ->
    v = @d[0]
    `for (var i = 1; i < this.c; i++) {
      v += this.d[i] * pow(DIGIT_MASK, i)
    }`
    return v