Protocol Buffer runtime library and 'protoc' plugin

lib/protobuf/runtime/PbCodec.dart

+// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+class _Constants {
+  static final int MIN_SINT32 = -2147483648;
+  static final int MAX_SINT32 =  2147483647;
+  static final int MAX_UINT32 =  4294967295;
+  static final int MIN_SINT64 = -9223372036854775808;
+  static final int MAX_SINT64 =  9223372036854775807;
+  static final int MAX_UINT64 =  18446744073709551615;
+  static final double MIN_FLOAT_DENORM = 1.401298464324817E-45;
+  static final double MAX_FLOAT = 3.4028234663852886E38;
+
+  static final int POWER_64_INT = 18446744073709551616;
+  static final int POWER_63_INT = 9223372036854775808;
+  static final int POWER_32_INT = 4294967296;
+  static final int POWER_31_INT = 2147483648;
+  static final int POWER_25_INT = 33554432;
+  // use literal to avoid browser issues
+  static final int MAX_BITS_32 = 0xffffffff;
+  static final int MAX_BITS_64 = (1 << 64) - 1;
+  static final int MAX_BITS_8 = (1 << 8) - 1;
+  static final int MAX_BITS_7 = (1 << 7) - 1;
+  static final int MIN_BITS_8 = (1 << 7);
+  static final int OCTET_BIT_COUNT = 8;
+  static final int SEPTET_BIT_COUNT = 7;
+  static final int BYTES_IN_32_BITS = 4;
+  static final int BYTES_IN_64_BITS = 8;
+  static final List<int> trueBytes = const [0x01];
+  static final List<int> falseBytes = const [0x00];
+
+  // 2^512, 2^-512
+  static final double POWER_512 = 1.3407807929942597E154;
+  static final double POWER_MINUS_512 = 7.458340731200207E-155;
+  // 2^256, 2^-256
+  static final double POWER_256 = 1.157920892373162E77;
+  static final double POWER_MINUS_256 = 8.636168555094445E-78;
+  // 2^128, 2^-128
+  static final double POWER_128 = 3.4028236692093846E38;
+  static final double POWER_MINUS_128 = 2.9387358770557188E-39;
+  // 2^64, 2^-64
+  static final double POWER_64 = 18446744073709551616.0;
+  static final double POWER_MINUS_64 = 5.421010862427522E-20;
+  // 2^52, 2^-52
+  static final double POWER_52 = 4503599627370496.0;
+  static final double POWER_MINUS_52 = 2.220446049250313E-16;
+  // 2^32, 2^-32
+  static final double POWER_32 = 4294967296.0;
+  static final double POWER_MINUS_32 = 2.3283064365386963E-10;
+  // 2^31
+  static final double POWER_31 = 2147483648.0;
+  // 2^20, 2^-20
+  static final double POWER_20 = 1048576.0;
+  static final double POWER_MINUS_20 = 9.5367431640625E-7;
+  // 2^16, 2^-16
+  static final double POWER_16 = 65536.0;
+  static final double POWER_MINUS_16 = 0.0000152587890625;
+  // 2^8, 2^-8
+  static final double POWER_8 = 256.0;
+  static final double POWER_MINUS_8 = 0.00390625;
+  // 2^4, 2^-4
+  static final double POWER_4 = 16.0;
+  static final double POWER_MINUS_4 = 0.0625;
+  // 2^2, 2^-2
+  static final double POWER_2 = 4.0;
+  static final double POWER_MINUS_2 = 0.25;
+  // 2^1, 2^-1
+  static final double POWER_1 = 2.0;
+  static final double POWER_MINUS_1 = 0.5;
+  // 2^-149 (smallest single non-denorm)
+  static final double POWER_MINUS_149 = 1.401298464324817E-45;
+  // 2^-1022 (smallest double non-denorm)
+  static final double POWER_MINUS_1022 = 2.2250738585072014E-308;
+
+  static final List<double> powers = const [
+    POWER_512, POWER_256, POWER_128, POWER_64, POWER_32, POWER_16, POWER_8,
+    POWER_4, POWER_2, POWER_1
+  ];
+
+  static final List<double> invPowers = const [
+    POWER_MINUS_512, POWER_MINUS_256, POWER_MINUS_128, POWER_MINUS_64,
+    POWER_MINUS_32, POWER_MINUS_16, POWER_MINUS_8, POWER_MINUS_4, POWER_MINUS_2,
+    POWER_MINUS_1
+  ];
+}
+
+/**
+ * An unsigned 64-bit number, stored internally as two unsigned 32-bit numbers.
+ */
+class Packed64 {
+
+  int64 _packed;
+
+  // Determine whether the platform supports ints greater than 2^53
+  // without loss of precision.
+  static bool _haveBigIntsCached = null;
+
+  static bool get _haveBigInts() {
+    if (_haveBigIntsCached == null) {
+      var x = 9007199254740992;
+      // Defeat compile-time constant folding.
+      if (2 + 2 != 4) {
+        x = 0;
+      }
+      var y = x + 1;
+      var same = y == x;
+      _haveBigIntsCached = !same;
+    }
+    return _haveBigIntsCached;
+  }
+
+  static final bool _allowSoftInts = true;
+
+  bool get _softInts() =>
+      (null !== _haveBigIntsCached && _haveBigIntsCached) ||
+      (null !== _allowSoftInts && _allowSoftInts);
+
+  /**
+   * Constructs a [Packed64] instance with given high and low 32-bit words.
+   * Throws [:IllegalArgumentException:] if either the [lo] or [hi] int is
+   * outside the range of a signed 32-bit INT.
+   */
+  Packed64(int hi, int lo) {
+    if (hi < -_Constants.POWER_32_INT || hi >= _Constants.POWER_32_INT) {
+      throw new IllegalArgumentException("Hi value out of range: $hi");
+    }
+    if (lo < -_Constants.POWER_32_INT || lo >= _Constants.POWER_32_INT) {
+      throw new IllegalArgumentException("Lo value out of range: $lo");
+    }
+    _packed = new int64.fromInts(hi, lo);
+  }
+
+  /**
+   * Constructs a [Packed64] instance from a list of byte values, LSB first.
+   */
+  Packed64.fromBytes(List<int> b) {
+    _packed = new int64.fromBytes(b);
+  }
+
+  /**
+   * Constructs a [Packed64] instance that will have the bit pattern of the
+   * given [double] value.  All [:NaN:] values are converted to a canonical
+   * bit pattern.
+   */
+  factory Packed64.fromDouble(double d) {
+    if (d.isNaN()) {
+      return new Packed64(0x7ff80000, 0x0);
+    }
+
+    bool negative = false;
+    if (d.isNegative()) {
+      negative = true;
+      d = -d;
+    }
+    if (d == 0.0) {
+      if (negative) {
+        return new Packed64(_Constants.POWER_31_INT, 0x0);
+      } else {
+        return new Packed64(0x0, 0x0);
+      }
+    }
+    if (d.isInfinite()) {
+      if (negative) {
+        return new Packed64(0xfff00000, 0x0);
+      } else {
+        return new Packed64(0x7ff00000, 0x0);
+      }
+    }
+
+    int exp = 0;
+
+    // Scale d by powers of 2 into the range [1.0, 2.0)
+    // If the exponent would go below -1023, scale into (0.0, 1.0) instead
+    if (d < 1.0) {
+      int bit = 512;
+      for (int i = 0; i < 10; i++, bit >>= 1) {
+        if (d < _Constants.invPowers[i] && exp - bit >= -1023) {
+          d *= _Constants.powers[i];
+          exp -= bit;
+        }
+      }
+      // Force into [1.0, 2.0) range
+      if (d < 1.0 && exp - 1 >= -1023) {
+        d *= 2.0;
+        exp--;
+      }
+    } else if (d >= 2.0) {
+      int bit = 512;
+      for (int i = 0; i < 10; i++, bit >>= 1) {
+        if (d >= _Constants.powers[i]) {
+          d *= _Constants.invPowers[i];
+          exp += bit;
+        }
+      }
+    }
+
+    if (exp > -1023) {
+      // Remove significand of non-denormalized mantissa
+      d -= 1.0;
+    } else {
+      // Insert 0 bit as significand of denormalized mantissa
+      d *= 0.5;
+    }
+
+    // Extract high 20 bits of mantissa
+    int ihi = (d * _Constants.POWER_20).toInt();
+
+    // Extract low 32 bits of mantissa
+    d -= ihi * _Constants.POWER_MINUS_20;
+    int ilo = (d * _Constants.POWER_52).toInt();
+
+    // Exponent bits
+    ihi |= (exp + 1023) << 20;
+    // Sign bit
+    if (negative) {
+      ihi += _Constants.POWER_31_INT;
+    }
+
+    return new Packed64(ihi, ilo);
+  }
+
+  void _orShifted(int bits, int shift) {
+    _packed |= new int64.fromInt(bits) << shift;
+  }
+
+  /**
+   * Constructs a [Packed64] instance from a variable-length representation.
+   * Throws an [:IllegalArgumentException:] if the encoding is invalid.
+   */
+  Packed64.fromVarintBytes(List<int> b) {
+    try {
+      _packed = int64.ZERO;
+      int i = 0;
+      bool lastByte = ((b[i] & _Constants.MIN_BITS_8) === 0);
+      while (i < 10 && !lastByte) {
+        _orShifted(b[i] & _Constants.MAX_BITS_7,
+            _Constants.SEPTET_BIT_COUNT * i);
+        i++;
+        lastByte = (b[i] & _Constants.MIN_BITS_8) === 0;
+      }
+      _orShifted(b[i] & _Constants.MAX_BITS_7,
+          _Constants.SEPTET_BIT_COUNT * i);
+    } catch (IndexOutOfRangeException e) {
+      throw new IllegalArgumentException("Invalid Encoding");
+    }
+  }
+
+  /**
+   * Constructs a [Packed64] instance whose value is equivalent to the given
+   * value. Throws an [:IllegalArgumentException:] if the value is &lt;
+   * -9223372036854775808 (MIN_SINT64) or &gt; 18446744073709551615
+   * (MAZ_UINT64).
+   */
+  Packed64.fromInt(int x) {
+    if (x < -9223372036854775808 || x > 18446744073709551615) {
+      throw new IllegalArgumentException("Out of range: $x");
+    }
+    _packed = new int64.fromInt(x);
+  }
+
+  /**
+   * Compares this [Packed64] with a given [Packed64] or [int] value.
+   */
+  bool operator ==(var other) {
+    if (other is num) {
+      return this.toInt() == new Packed64.fromInt(other);
+    }
+    if (other is !Packed64) {
+      return false;
+    }
+    return other._packed == _packed;
+  }
+
+  int hashCode() {
+    return _packed.hashCode();
+  }
+
+  /**
+   * Returns the 32 high bits of this [Packed64] value as an unsigned integer
+   * in the range [0, 2^31 - 1].
+   */
+  int get hi() => ((_packed >> 32) & 0xffffffff).toInt();
+
+  /**
+   * Returns the 32 low bits of this [Packed64] value as an unsigned integer
+   * in the range [0, 2^31 - 1].
+   */
+  int get lo() => (_packed & 0xffffffff).toInt();
+
+  /**
+   * Decodes this [Packed64] from the zig-zag representation
+   * [:(n << 1) ^ (n >> 63):].
+   */
+  Packed64 decodeZigZag() {
+    int ihi = this.hi;
+    int ilo = this.lo;
+
+    int sign = ilo % 2;
+    ilo = ((ihi % 2 == 1) ? _Constants.POWER_31_INT : 0) + (ilo ~/ 2);
+    ihi = ihi ~/ 2;
+    if (sign == 1) {
+      ihi = _bitFlip(ihi);
+      ilo = _bitFlip(ilo);
+    }
+    Packed64 result = new Packed64(ihi, ilo);
+    return result;
+  }
+
+  static int _bitFlip(int x) => _Constants.MAX_BITS_32 - x;
+
+  /**
+   * Encodes this [Packed64] in the zig-zag representation
+   * [:(n << 1) ^ (n >> 63):].
+   */
+  Packed64 encodeZigZag() {
+    int ihi = hi;
+    int ilo = lo;
+    bool negative = ihi >= _Constants.POWER_31_INT;
+    ihi = ihi * 2 + (ilo >= _Constants.POWER_31_INT ? 1 : 0);
+    ilo = ilo * 2;
+    if (ihi >= _Constants.POWER_32_INT) {
+      ihi -= _Constants.POWER_32_INT;
+    }
+    if (ilo >= _Constants.POWER_32_INT) {
+      ilo -= _Constants.POWER_32_INT;
+    }
+    if (negative) {
+      ihi = _bitFlip(ihi);
+      ilo = _bitFlip(ilo);
+    }
+    return new Packed64(ihi, ilo);
+  }
+
+  /**
+   * Returns [true] if this [Packed64] can safely be converted to a signed
+   * integer in the range [-2^51, 2^51 - 1].
+   */
+  bool isSafeAsInt() {
+    if (_haveBigInts) {
+      return true;
+    } else {
+      int top = (hi >> 20) & 0xfff;
+      return top == 0x0 || top == 0xfff;
+    }
+  }
+
+  /**
+   * Returns [true] if this [Packed64] can safely be converted to an unsigned
+   * integer in the range [0, 2^52 - 1].
+   */
+  bool isSafeAsUint() {
+    if (_haveBigInts) {
+      return true;
+    } else {
+      int top = (hi >> 20) & 0xfff;
+      return top == 0x0;
+    }
+  }
+
+  /**
+   * Return the number of bytes required to encdode this [Packed64] using
+   * the variable-length representation.
+   */
+  int sizeOfVarint() {
+    int ihi = this.hi;
+    int ilo = this.lo;
+
+    int i = 0;
+    while (i < 10) {
+      ilo = ((ihi % 128) * _Constants.POWER_25_INT) + (ilo ~/ 128);
+      ihi ~/= 128;
+      i++;
+      if (ihi === 0 && ilo === 0) {
+        return i;
+      }
+    }
+    return i;
+  }
+
+  /**
+   * Return this [Packed64] as a list of 8 ints, LSB first.
+   */
+  List<int> toBytes() => _packed.toBytes();
+
+  /**
+   * Return this [Packed64] interpreted as an IEEE double-precision value.
+   */
+  double toDouble() {
+    int ihi = this.hi;
+    int ilo = this.lo;
+    if (ihi < 0) {
+      ihi += _Constants.POWER_32_INT;
+    }
+    if (ilo < 0) {
+      ilo += _Constants.POWER_32_INT;
+    }
+
+    bool negative = (ihi & _Constants.POWER_31_INT) != 0;
+    int exp = (ihi >> 20) & 0x7ff;
+    ihi &= 0xfffff; // remove sign bit and exponent
+
+    if (exp == 0x0) {
+      double d = (ihi * _Constants.POWER_MINUS_20) +
+          (ilo * _Constants.POWER_MINUS_52);
+      d *= _Constants.POWER_MINUS_1022;
+      return negative ? (d == 0.0 ? -0.0 : -d) : d;
+    } else if (exp == 0x7ff) {
+      if (ihi == 0 && ilo == 0) {
+        return negative ? double.NEGATIVE_INFINITY : double.INFINITY;
+      } else {
+        return double.NAN;
+      }
+    }
+
+    // Normalize exponent
+    exp -= 1023;
+
+    double d = 1.0 + (ihi * _Constants.POWER_MINUS_20) +
+        (ilo * _Constants.POWER_MINUS_52);
+    if (exp > 0) {
+      int bit = 512;
+      for (int i = 0; i < 10; i++, bit >>= 1) {
+        if (exp >= bit) {
+          d *= _Constants.powers[i];
+          exp -= bit;
+        }
+      }
+    } else if (exp < 0) {
+      while (exp < 0) {
+        int bit = 512;
+        for (int i = 0; i < 10; i++, bit >>= 1) {
+          if (exp <= -bit) {
+            d *= _Constants.invPowers[i];
+            exp += bit;
+          }
+        }
+      }
+    }
+    return negative ? -d : d;
+  }
+
+  /**
+   * Return the value of this [Packed64] as an int if the resulting value
+   * is in the legal range of [-2^51, 2^51 -1], otherwise throw an
+   * IllegalArgumentException.
+   */
+  int toInt() => _packed.toInt();
+
+  /**
+   * Return the value of this [Packed64] as an int if the resulting value
+   * is in the legal range of [-2^51, 2^51 -1], otherwise return [this].
+   */
+  Dynamic toIntIfSafe() {
+    if (_softInts && this.isSafeAsInt()) {
+      return this.toInt();
+    }
+    return this;
+  }
+
+  /**
+   * Return the value of this [Packed64] as an int if the resulting value
+   * is in the legal range of [0, 2^52 -1], otherwise throw an
+   * IllegalArgumentException.
+   */
+  int toUint() {
+    if (!isSafeAsUint()) {
+      throw new IllegalArgumentException("Out of range");
+    }
+    int value = this.hi * _Constants.POWER_32_INT + this.lo;
+    return value;
+  }
+
+  /**
+   * Return the value of this [Packed64] as an int if the resulting value
+   * is in the legal range of [0, 2^52 -1], otherwise return [this].
+   */
+  Dynamic toUintIfSafe() {
+    if (_softInts && this.isSafeAsUint()) {
+      return this.toUint();
+    }
+    return this;
+  }
+
+  /**
+   * Return a list of up to 10 ints encoding this [Packed64] using a
+   * variable-length representation.
+   */
+  List<int> toVarintBytes() {
+    int ihi = this.hi;
+    int ilo = this.lo;
+
+    List<int> b = [];
+    int i = 0;
+    while (true) {
+      i++;
+      if ((ihi != 0 || ilo >= 128) && i < 10) {
+        int v = 128 + (ilo % 128);
+        b.add(v);
+      } else {
+        int v = ilo % 128;
+        b.add(v);
+        break;
+      }
+      ilo = ((ihi % 128) * 33554432) + (ilo ~/ 128);
+      ihi ~/= 128;
+    }
+    return b;
+  }
+
+  /**
+   * Return a String useful for debugging.
+   */
+  String toDebugString() {
+    return "Packed64[0x${hi.toRadixString(16)},0x${lo.toRadixString(16)}]";
+  }
+
+  /**
+   * Return a String in decimal representation.
+   */
+  String toString() {
+    return _packed.toString();
+  }
+}
+
+/*
+ * Provides conversion utilities from dart types to/from protocol buffer wire
+ * format.
+ */
+class PbCodec {
+  static bool toBool(List<int> b) => b[0] !== 0;
+
+  static int toFixed32(List<int> b) => packedToUint32(bytesToPacked(b));
+
+  // return value may be an int or a Packed64
+  static Dynamic toFixed64(List<int> b) => int64ToUint64(bytesToPacked64(b));
+
+  static int toInt32(List<int> b) => packedToInt32(varintBytesToPacked(b));
+
+  // return value may be an int or a Packed64
+  static Dynamic toInt64(List<int> b) =>
+      int64ToSigned(varintBytesToPacked64(b));
+
+  static int toSfixed32(List<int> b) => packedToInt32(bytesToPacked(b));
+
+  // return value may be an int or a Packed64
+  static Dynamic toSfixed64(List<int> b) => bytesToPacked64(b);
+
+  static int toSint32(List<int> b) => packedToSint32(varintBytesToPacked(b));
+
+  // return value may be an int or a Packed64
+  static Dynamic toSint64(List<int> b) =>
+      int64ToSint64(varintBytesToPacked64(b));
+
+  static int toUint32(List<int> b) => packedToUint32(varintBytesToPacked(b));
+
+  // return value may be an int or a Packed64
+  static Dynamic toUint64(List<int> b) =>
+      int64ToUint64(varintBytesToPacked64(b));
+
+  static double toFloat(List<int> b) => packedToFloat(bytesToPacked(b));
+
+  static double toDouble(List<int> b) => int64ToDouble(bytesToPacked64(b));
+
+  static List<int> boolToBytes(bool value) =>
+      value ? _Constants.trueBytes : _Constants.falseBytes;
+
+  static List<int> fixed32ToBytes(int value) =>
+      packed32ToBytes(uint32ToPacked(value));
+
+  // value may be an int or a Packed64
+  static List<int> fixed64ToBytes(var value) => packed64ToBytes(value);
+
+  static List<int> int32ToBytes(int value) =>
+      packedToVarintBytes(int32ToPacked(value));
+
+  // value may be an int or a Packed64
+  static List<int> int64ToBytes(var value) =>
+    int64ToVarintBytes(value);
+
+  static List<int> sfixed32ToBytes(int value) =>
+      packed32ToBytes(int32ToPacked(value));
+
+  // value may be an int or a Packed64
+  static List<int> sfixed64ToBytes(var value) =>
+      packed64ToBytes(value);
+
+  static List<int> sint32ToBytes(int value) =>
+      packedToVarintBytes(sint32ToPacked(value));
+
+  // value may be an int or a Packed64
+  static List<int> sint64ToBytes(var value) =>
+      int64ToVarintBytes(sint64ToPacked64(value));
+
+  static List<int> uint32ToBytes(int value) =>
+      packedToVarintBytes(uint32ToPacked(value));
+
+  // value may be an int or a Packed64
+  static List<int> uint64ToBytes(var value) =>
+      int64ToVarintBytes(uint64ToPacked64(value));
+
+  static List<int> floatToBytes(double value) =>
+      packed32ToBytes(floatToPacked(value));
+
+  static List<int> doubleToBytes(double value) =>
+      packed64ToBytes(doubleToPacked64(value));
+
+  static final int sizeOfBool = 1;
+
+  static int sizeOfFixed32 = _Constants.BYTES_IN_32_BITS;
+
+  static int sizeOfFixed64 = _Constants.BYTES_IN_64_BITS;
+
+  static int sizeOfSfixed32 = _Constants.BYTES_IN_32_BITS;
+
+  static int sizeOfSfixed64 = _Constants.BYTES_IN_64_BITS;
+
+  static int sizeOfInt32(int value) => value < 0 ? 5 : sizeOfVarint(value);
+
+  // value may be an int or a Packed64
+  static int sizeOfInt64(var value) {
+    if (value is Packed64) {
+       return value.sizeOfVarint();
+    } else if (value is num) {
+      if (value < 0) {
+        return 10;
+      } else {
+        return sizeOfVarint64(new Packed64.fromInt(value.toInt()));
+      }
+    } else {
+      throw new IllegalArgumentException("Expected Packed64 or int");
+    }
+  }
+
+  static int sizeOfSint32(int value) => sizeOfVarint(encodeZigZag32(value));
+
+  // value may be an int or a Packed64
+  static int sizeOfSint64(var value) => sizeOfVarint64(encodeZigZag64(value));
+
+  static int sizeOfUint32(int value) => sizeOfVarint(value);
+
+  // value may be an int or a Packed64
+  static int sizeOfUint64(var value) => sizeOfVarint64(value);
+
+  static int sizeOfVarint(int value) {
+    int i = 0;
+    while (i < 10) {
+      value >>= _Constants.SEPTET_BIT_COUNT;
+      i++;
+      if (value === 0) return i;
+    }
+    return i;
+  }
+
+  // value may be an int or a Packed64
+  static int sizeOfVarint64(var value) {
+    if (value is Packed64) {
+      return value.sizeOfVarint();
+    } else if (value is num) {
+      return new Packed64.fromInt(value.toInt()).sizeOfVarint();
+    } else {
+      throw new IllegalArgumentException("Expected Packed64 or int");
+    }
+  }
+
+  static int int32ToPacked(int value) {
+    if (value < 0) {
+      return _Constants.POWER_32_INT + value;
+    }
+    return value;
+  }
+
+  static int sint32ToPacked(int value) => encodeZigZag32(value);
+
+  // value and return may be an int or a Packed64
+  static Dynamic sint64ToPacked64(var value) => encodeZigZag64(value);
+
+  static int uint32ToPacked(int value) => value;
+
+  // value and return may be an int or a Packed64
+  static Dynamic uint64ToPacked64(var value) => value;
+
+  static int packedToInt32(int packed) {
+    if (packed >= _Constants.POWER_32_INT) {
+      packed &= _Constants.MAX_BITS_32;
+    }
+    if (packed < 0 || ((packed & _Constants.POWER_31_INT) == 0)) {
+      return packed;
+    } else {
+      return packed - _Constants.POWER_32_INT;
+    }
+  }
+
+  static int packedToSint32(int packed) => decodeZigZag32(packed);
+
+  static int packedToUint32(int packed) => packed;
+
+  // value and return may be an int or a Packed64
+  static Dynamic int64ToSint64(var packed) => decodeZigZag64(packed);
+
+  // value and return may be an int or a Packed64
+  static Dynamic int64ToUint64(var packed) {
+    if (packed is Packed64) {
+      return packed;
+    } else if (packed < 0) {
+      return _Constants.POWER_64_INT + packed;
+    } else {
+      return packed;
+    }
+  }
+
+  // value and return may be an int or a Packed64
+  static Dynamic int64ToSigned(var packed) {
+    if (packed is Packed64) {
+      return packed;
+    } else if (packed >= _Constants.POWER_63_INT) {
+      return packed - _Constants.POWER_64_INT;
+    } else {
+      return packed;
+    }
+  }
+
+  static int bytesToPacked(List<int> b) {
+    int result = 0;
+    int factor = 1;
+    for (int i = 0; i < b.length && i < _Constants.BYTES_IN_64_BITS;
+        i++, factor *= 256) {
+      result += (b[i] & _Constants.MAX_BITS_8) * factor;
+    }
+    return result;
+  }
+
+  static Dynamic bytesToPacked64(List<int> b) =>
+      new Packed64.fromBytes(b).toIntIfSafe();
+
+  static int _unsigned(int x) => x < 0 ? x + _Constants.POWER_32_INT : x;
+
+  static int varintBytesToPacked(List<int> b) {
+    try {
+      int result = 0;
+      int i = 0;
+      bool lastByte = ((b[i] & _Constants.MIN_BITS_8) === 0);
+      while (i < 10 && !lastByte) {
+        result |= (((b[i] & _Constants.MAX_BITS_7) <<
+            (_Constants.SEPTET_BIT_COUNT * i)));
+        i++;
+        lastByte = (b[i] & _Constants.MIN_BITS_8) === 0;
+      }
+      result |= (b[i] & _Constants.MAX_BITS_7) <<
+          (_Constants.SEPTET_BIT_COUNT * i);
+      return _unsigned(result);
+    } catch (IndexOutOfRangeException e) {
+      throw new IllegalArgumentException("Invalid Encoding");
+    }
+  }
+
+  static Dynamic varintBytesToPacked64(List<int> b) =>
+     new Packed64.fromVarintBytes(b).toUintIfSafe();
+
+  static List<int> packed32ToBytes(int value) {
+    List<int> b = new List(4);
+    for (int i = 0; i < 4; i++) {
+      if (value === 0) {
+        while (i < 4) {
+          b[i] = 0;
+          i++;
+        }
+      } else {
+        b[i] = value & _Constants.MAX_BITS_8;
+        value >>= _Constants.OCTET_BIT_COUNT;
+      }
+    }
+    return b;
+  }
+
+  // value may be an int or a Packed64
+  static List<int> packed64ToBytes(var value) {
+    if (value is Packed64) {
+      return value.toBytes();
+    } else if (value is num) {
+      return new Packed64.fromInt(value.toInt()).toBytes();
+    } else {
+      throw new IllegalArgumentException("Expected Packed64 or int");
+    }
+  }
+
+  static List<int> packedToVarintBytes(int value) {
+    List<int> b = [];
+    int i = 0;
+    while (true) {
+      i++;
+      int nextVal = value ~/ 128;
+      if (nextVal !== 0 && i < 10) {
+        int v = 128 + (value % 128);
+        b.add(v);
+      } else {
+        int v = value % 128;
+        b.add(v);
+        break;
+      }
+      value = nextVal;
+    }
+    return b;
+  }
+
+  static List<int> int64ToVarintBytes(var value) {
+    if (value is Packed64) {
+      return value.toVarintBytes();
+    } else if (value is num) {
+      return new Packed64.fromInt(value.toInt()).toVarintBytes();
+    } else {
+      throw new IllegalArgumentException("Expected Packed64 or int");
+    }
+  }
+
+  static int encodeZigZag32(int value) {
+    if (value < 0) {
+      return -(value * 2) - 1;
+    } else {
+      return value * 2;
+    }
+  }
+
+  // value and return may be an int or a Packed64
+  static Dynamic encodeZigZag64(var value) {
+    if (value is Packed64) {
+      return value.encodeZigZag().toUintIfSafe();
+    } else if (value is num) {
+      return new Packed64.fromInt(value.toInt()).encodeZigZag().toUint();
+    } else {
+      throw new IllegalArgumentException("Expected Packed64 or int");
+    }
+  }
+
+  static int decodeZigZag32(int value) {
+    if ((value & 0x1) == 0) {
+      return value ~/ 2;
+    } else {
+      value = (value - 1) ~/ 2;
+      if (value < _Constants.POWER_32_INT) {
+        return -value - 1;
+      } else {
+        return value;
+      }
+    }
+  }
+
+  // value and return may be an int or a Packed64
+  static Dynamic decodeZigZag64(var value) {
+    if (value is Packed64) {
+      return value.decodeZigZag().toIntIfSafe();
+    } else if (value is num) {
+      return new Packed64.fromInt(value.toInt()).decodeZigZag().toIntIfSafe();
+    } else {
+      throw new IllegalArgumentException("Expected Packed64 or int");
+    }
+  }
+
+  // value may be an int or a Packed64
+  static double int64ToDouble(var value) {
+    if (value is Packed64) {
+      return value.toDouble();
+    } else if (value is num) {
+      return new Packed64.fromInt(value.toInt()).toDouble();
+    } else {
+      throw new IllegalArgumentException("Expected Packed64 or int");
+    }
+  }
+
+  static double packedToFloat(int packed) {
+    bool negative = (packed & _Constants.POWER_31_INT) != 0;
+    int exp = (packed >> 23) & 0xff;
+    packed &= 0x7fffff;
+
+    if (exp == 0x0) {
+      // Handle +/- 0 here, denorms below
+      if (packed == 0) {
+        return negative ? -0.0 : 0.0;
+      }
+    } else if (exp == 0xff) {
+      // Inf & NaN
+      if (packed == 0) {
+        return negative ? double.NEGATIVE_INFINITY : double.INFINITY;
+      } else {
+        return double.NAN;
+      }
+    }
+
+    // Build the bits of a 64-bit double from the incoming bits
+    int ihi = negative ? _Constants.POWER_31_INT : 0x0;
+    int ilo = 0x0;
+    if (exp == 0) {
+      // Input is denormalized, renormalize by shifting left until there is a
+      // leading 1
+      exp = 897;
+      while ((packed & 0x800000) == 0) {
+        packed <<= 1;
+        exp--;
+      }
+      packed &= 0x7fffff;
+      ihi |= exp << 20;
+      ihi |= packed >> 3;
+      ilo = (packed & 0x7) << 29;
+    } else {
+      // Normalized number, rebias exponent and shift mantissa into place
+      ihi |= (exp + 896) << 20;
+      ihi |= packed >> 3;
+      ilo = (packed & 0x7) << 29;
+    }
+    return int64ToDouble(new Packed64(ihi, ilo));
+  }
+
+  /**
+   * Return the 32-bit IEEE single-precision representation that represents
+   * the value [d] truncated to 23 fractional bits.
+   */
+  static int floatToPacked(double d) {
+    // Return a canonical NaN since we have no way to detect anything else
+    if (d.isNaN()) {
+      return 0x7fc00000;
+    }
+
+    bool negative = false;
+    if (d.isNegative()) {
+      negative = true;
+      d = -d;
+    }
+    // Numbers below min float map to 0.0
+    if (d < _Constants.MIN_FLOAT_DENORM) {
+      return negative ? _Constants.POWER_31_INT : 0x0;
+    }
+    // Numbers above max float map to Infinity
+    if (d.isInfinite() || d > _Constants.MAX_FLOAT) {
+      return negative ? 0xff800000 : 0x7f800000;
+    }
+
+    // Obtain the 64-bit representation and extract its exponent and
+    // mantissa.
+    var packed = doubleToPacked64(d);
+    int exp, mantissa;
+    if (packed is Packed64) {
+      Packed64 packed64 = packed;
+      exp = ((packed64.hi >> 20) & 0x7ff) - 1023;
+      mantissa = ((packed64.hi & 0xfffff) << 3) | ((packed64.lo >> 29) & 0x7);
+    } else if (packed is num) {
+      var ipacked = packed.toInt();
+      exp = ((ipacked >> 52) & 0x7ff) - 1023;
+      mantissa = (ipacked & 0xfffffffffffff) >> 29;
+    }
+
+    // If the number will be a denorm in the float representation
+    // (i.e., its exponent is -127 or smaller), add a leading 1 to the
+    // mantissa and shift it right to maintain an exponent of -127.
+    if (exp <= -127) {
+      mantissa = (0x800000 | mantissa) >> (-127 - exp + 1);
+      exp = -127;
+    }
+
+    // Construct the 32-bit representation
+    int packed32 = negative ? _Constants.POWER_31_INT : 0x0;
+    packed32 |= (exp + 127) << 23;
+    packed32 |= mantissa;
+    if (packed32 < 0) {
+      packed32 += _Constants.POWER_32_INT;
+    }
+    return packed32;
+  }
+
+  static Dynamic doubleToPacked64(double d) {
+    Packed64 packed = new Packed64.fromDouble(d);
+    if (packed.isSafeAsUint()) {
+      return packed.toUint();
+    }
+    return packed;
+  }
+
+  // JSON
+
+  // ('0' + x) or ('a' + x - 10)
+  static int _hexDigit(int x) => x < 10 ? 48 + x : 87 + x;
+
+  // Escape a string to be suitable as a JSON value
+  static String escapeString(String x) {
+    List<int> chars = x.charCodes();
+    List<int> output = new List<int>();
+    for (int i = 0; i < chars.length; i++) {
+      int c = chars[i];
+      // Escape control characters, double-quote, and backslash
+      if (c < 32) { // control characters
+        output.add(92); // '\'
+        switch (c) {
+        case 8: // backspace
+          output.add(98); // 'b'
+          break;
+        case 9: // tab
+          output.add(116); // 't'
+          break;
+        case 10: // newline
+          output.add(110); // 'n'
+          break;
+        case 12: // formfeed
+          output.add(102); // 'f'
+          break;
+        case 13: // carriage return
+          output.add(114); // 'r'
+          break;
+        default:
+          output.add(117); // 'u'
+          output.add(_hexDigit((c >> 12) & 0xf));
+          output.add(_hexDigit((c >> 8) & 0xf));
+          output.add(_hexDigit((c >> 4) & 0xf));
+          output.add(_hexDigit(c & 0xf));
+          break;
+        }
+      } else if (c == 34 || c == 92) { // double-quote or backslash
+        output.add(92); // '\'
+        output.add(c);
+      } else {
+        output.add(c);
+      }
+    }
+    return new String.fromCharCodes(output);
+  }
+}
+
+// TODO - make this a separate library
+class Base64Codec {
+
+  // MIME Base64 characters plus padding char '=' (RFC 2045)
+  static final String MIME_ALPHABET =
+      "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
+
+  static Base64Codec _defaultInstance = null;
+
+  static Base64Codec get defaultInstance() {
+    if (_defaultInstance == null) {
+      _defaultInstance = new Base64Codec();
+    }
+    return _defaultInstance;
+  }
+
+  List<int> _base64Chars = null;
+  List<int> _base64InverseChars = null;
+  int _padding;
+
+  Base64Codec([String alphabet = null]) {
+    assert(alphabet == null || alphabet.length == 65);
+    if (alphabet == null) {
+      alphabet = MIME_ALPHABET;
+    }
+    _initTables(alphabet);
+  }
+
+  void _initTables(String alphabet) {
+    _base64Chars = alphabet.charCodes();
+    _base64InverseChars = new List<int>(128);
+    // Use -1 to indicate an illegal character
+    for (int i = 0; i < 128; i++) {
+      _base64InverseChars[i] = -1;
+    }
+    for (int i = 0; i < 64; i++) {
+      _base64InverseChars[_base64Chars[i]] = i;
+    }
+    // The padding character is interpreted as 0
+    _padding = alphabet.charCodeAt(64);
+    _base64InverseChars[_padding] = 0;
+  }
+
+  int _base64Inverse(int x) {
+    // Look at 7 low bits only
+    int result = _base64InverseChars[x & 0x7f];
+    if (result == -1) {
+      throw new IllegalArgumentException("Unknown character code: ${x & 0x7f}");
+    }
+    return result;
+  }
+
+  List<int> decodeAsList(String s) {
+    int olen = 3 * (s.length ~/ 4);
+    // Inspect the last two characters of the input for padding
+    for (int i = Math.max(0, s.length - 2); i < s.length; i++) {
+      if (s.charCodeAt(i) == _padding) {
+        --olen;
+      }
+    }
+
+    int iidx = 0;
+    int oidx = 0;
+    List<int> data = createIntArray(olen);
+    int lastStartIndex = s.length - 3;
+    while (iidx < lastStartIndex) {
+      int c0 = _base64Inverse(s.charCodeAt(iidx++));
+      int c1 = _base64Inverse(s.charCodeAt(iidx++));
+      int c2 = _base64Inverse(s.charCodeAt(iidx++));
+      int c3 = _base64Inverse(s.charCodeAt(iidx++));
+      int c24 = (c0 << 18) | (c1 << 12) | (c2 << 6) | c3;
+
+      data[oidx++] = (c24 >> 16) & 0xff;
+      if (oidx == olen) {
+        break;
+      }
+      data[oidx++] = (c24 >> 8) & 0xff;
+      if (oidx == olen) {
+        break;
+      }
+      data[oidx++] = c24 & 0xff;
+    }
+
+    return data;
+  }
+
+  String decode(String s) => new String.fromCharCodes(decodeAsList(s));
+
+  // Encode a String as a Base64 string.  Only the low 8 bits of each
+  // character code are used.
+  String encodeList(List<int> x, [bool pad = true]) {
+    int idx = 0;
+    int bytesLeft = x.length;
+    List<int> data = new List<int>();
+    while (bytesLeft > 0) {
+      // Concatenate up to 3 input characters into a 24-bit chunk
+      int b0 = x[idx++] & 0xff;
+      int b1 = (bytesLeft > 1) ? x[idx++] & 0xff : 0;
+      int b2 = (bytesLeft > 2) ? x[idx++] & 0xff : 0;
+      int b24 = (b0 << 16) | (b1 << 8) | b2;
+
+      // Extract 4 6-bit chunks
+      int c0 = (b24 >> 18) & 0x3f;
+      int c1 = (b24 >> 12) & 0x3f;
+      int c2 = (b24 >> 6) & 0x3f;
+      int c3 = b24 & 0x3f;
+
+      // Ouput 4 characters, padding unused bits with "="
+      data.add(_base64Chars[c0]);
+      data.add(_base64Chars[c1]);
+      if (bytesLeft > 1 || pad) {
+        data.add(bytesLeft > 1 ? _base64Chars[c2] : _padding);
+      }
+      if (bytesLeft > 2 || pad) {
+        data.add(bytesLeft > 2 ? _base64Chars[c3] : _padding);
+      }
+      bytesLeft -= 3;
+    }
+    return new String.fromCharCodes(data);
+  }
+
+  String encode(String s, [bool pad = true]) => encodeList(s.charCodes(), pad);
+}