diff --git a/js/binary/utils.js b/js/binary/utils.js
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+++ b/js/binary/utils.js
@@ -0,0 +1,979 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+/**
+ * @fileoverview This file contains helper code used by jspb.BinaryReader
+ * and BinaryWriter.
+ *
+ * @author aappleby@google.com (Austin Appleby)
+ */
+
+goog.provide('jspb.utils');
+
+goog.require('goog.asserts');
+goog.require('goog.crypt.base64');
+goog.require('goog.string');
+goog.require('jspb.BinaryConstants');
+
+
+/**
+ * Javascript can't natively handle 64-bit data types, so to manipulate them we
+ * have to split them into two 32-bit halves and do the math manually.
+ *
+ * Instead of instantiating and passing small structures around to do this, we
+ * instead just use two global temporary values. This one stores the low 32
+ * bits of a split value - for example, if the original value was a 64-bit
+ * integer, this temporary value will contain the low 32 bits of that integer.
+ * If the original value was a double, this temporary value will contain the
+ * low 32 bits of the binary representation of that double, etcetera.
+ * @type {number}
+ */
+jspb.utils.split64Low = 0;
+
+
+/**
+ * And correspondingly, this temporary variable will contain the high 32 bits
+ * of whatever value was split.
+ * @type {number}
+ */
+jspb.utils.split64High = 0;
+
+
+/**
+ * Splits an unsigned Javascript integer into two 32-bit halves and stores it
+ * in the temp values above.
+ * @param {number} value The number to split.
+ */
+jspb.utils.splitUint64 = function(value) {
+  // Extract low 32 bits and high 32 bits as unsigned integers.
+  var lowBits = value >>> 0;
+  var highBits = Math.floor((value - lowBits) /
+                            jspb.BinaryConstants.TWO_TO_32) >>> 0;
+
+  jspb.utils.split64Low = lowBits;
+  jspb.utils.split64High = highBits;
+};
+
+
+/**
+ * Splits a signed Javascript integer into two 32-bit halves and stores it in
+ * the temp values above.
+ * @param {number} value The number to split.
+ */
+jspb.utils.splitInt64 = function(value) {
+  // Convert to sign-magnitude representation.
+  var sign = (value < 0);
+  value = Math.abs(value);
+
+  // Extract low 32 bits and high 32 bits as unsigned integers.
+  var lowBits = value >>> 0;
+  var highBits = Math.floor((value - lowBits) /
+                            jspb.BinaryConstants.TWO_TO_32);
+  highBits = highBits >>> 0;
+
+  // Perform two's complement conversion if the sign bit was set.
+  if (sign) {
+    highBits = ~highBits >>> 0;
+    lowBits = ~lowBits >>> 0;
+    lowBits += 1;
+    if (lowBits > 0xFFFFFFFF) {
+      lowBits = 0;
+      highBits++;
+      if (highBits > 0xFFFFFFFF) highBits = 0;
+    }
+  }
+
+  jspb.utils.split64Low = lowBits;
+  jspb.utils.split64High = highBits;
+};
+
+
+/**
+ * Convers a signed Javascript integer into zigzag format, splits it into two
+ * 32-bit halves, and stores it in the temp values above.
+ * @param {number} value The number to split.
+ */
+jspb.utils.splitZigzag64 = function(value) {
+  // Convert to sign-magnitude and scale by 2 before we split the value.
+  var sign = (value < 0);
+  value = Math.abs(value) * 2;
+
+  jspb.utils.splitUint64(value);
+  var lowBits = jspb.utils.split64Low;
+  var highBits = jspb.utils.split64High;
+
+  // If the value is negative, subtract 1 from the split representation so we
+  // don't lose the sign bit due to precision issues.
+  if (sign) {
+    if (lowBits == 0) {
+      if (highBits == 0) {
+        lowBits = 0xFFFFFFFF;
+        highBits = 0xFFFFFFFF;
+      } else {
+        highBits--;
+        lowBits = 0xFFFFFFFF;
+      }
+    } else {
+      lowBits--;
+    }
+  }
+
+  jspb.utils.split64Low = lowBits;
+  jspb.utils.split64High = highBits;
+};
+
+
+/**
+ * Converts a floating-point number into 32-bit IEEE representation and stores
+ * it in the temp values above.
+ * @param {number} value
+ */
+jspb.utils.splitFloat32 = function(value) {
+  var sign = (value < 0) ? 1 : 0;
+  value = sign ? -value : value;
+  var exp;
+  var mant;
+
+  // Handle zeros.
+  if (value === 0) {
+    if ((1 / value) > 0) {
+      // Positive zero.
+      jspb.utils.split64High = 0;
+      jspb.utils.split64Low = 0x00000000;
+    } else {
+      // Negative zero.
+      jspb.utils.split64High = 0;
+      jspb.utils.split64Low = 0x80000000;
+    }
+    return;
+  }
+
+  // Handle nans.
+  if (isNaN(value)) {
+    jspb.utils.split64High = 0;
+    jspb.utils.split64Low = 0x7FFFFFFF;
+    return;
+  }
+
+  // Handle infinities.
+  if (value > jspb.BinaryConstants.FLOAT32_MAX) {
+    jspb.utils.split64High = 0;
+    jspb.utils.split64Low = ((sign << 31) | (0x7F800000)) >>> 0;
+    return;
+  }
+
+  // Handle denormals.
+  if (value < jspb.BinaryConstants.FLOAT32_MIN) {
+    // Number is a denormal.
+    mant = Math.round(value / Math.pow(2, -149));
+    jspb.utils.split64High = 0;
+    jspb.utils.split64Low = ((sign << 31) | mant) >>> 0;
+    return;
+  }
+
+  exp = Math.floor(Math.log(value) / Math.LN2);
+  mant = value * Math.pow(2, -exp);
+  mant = Math.round(mant * jspb.BinaryConstants.TWO_TO_23) & 0x7FFFFF;
+
+  jspb.utils.split64High = 0;
+  jspb.utils.split64Low = ((sign << 31) | ((exp + 127) << 23) | mant) >>> 0;
+};
+
+
+/**
+ * Converts a floating-point number into 64-bit IEEE representation and stores
+ * it in the temp values above.
+ * @param {number} value
+ */
+jspb.utils.splitFloat64 = function(value) {
+  var sign = (value < 0) ? 1 : 0;
+  value = sign ? -value : value;
+
+  // Handle zeros.
+  if (value === 0) {
+    if ((1 / value) > 0) {
+      // Positive zero.
+      jspb.utils.split64High = 0x00000000;
+      jspb.utils.split64Low = 0x00000000;
+    } else {
+      // Negative zero.
+      jspb.utils.split64High = 0x80000000;
+      jspb.utils.split64Low = 0x00000000;
+    }
+    return;
+  }
+
+  // Handle nans.
+  if (isNaN(value)) {
+    jspb.utils.split64High = 0x7FFFFFFF;
+    jspb.utils.split64Low = 0xFFFFFFFF;
+    return;
+  }
+
+  // Handle infinities.
+  if (value > jspb.BinaryConstants.FLOAT64_MAX) {
+    jspb.utils.split64High = ((sign << 31) | (0x7FF00000)) >>> 0;
+    jspb.utils.split64Low = 0;
+    return;
+  }
+
+  // Handle denormals.
+  if (value < jspb.BinaryConstants.FLOAT64_MIN) {
+    // Number is a denormal.
+    var mant = value / Math.pow(2, -1074);
+    var mantHigh = (mant / jspb.BinaryConstants.TWO_TO_32);
+    jspb.utils.split64High = ((sign << 31) | mantHigh) >>> 0;
+    jspb.utils.split64Low = (mant >>> 0);
+    return;
+  }
+
+  var exp = Math.floor(Math.log(value) / Math.LN2);
+  if (exp == 1024) exp = 1023;
+  var mant = value * Math.pow(2, -exp);
+
+  var mantHigh = (mant * jspb.BinaryConstants.TWO_TO_20) & 0xFFFFF;
+  var mantLow = (mant * jspb.BinaryConstants.TWO_TO_52) >>> 0;
+
+  jspb.utils.split64High =
+      ((sign << 31) | ((exp + 1023) << 20) | mantHigh) >>> 0;
+  jspb.utils.split64Low = mantLow;
+};
+
+
+/**
+ * Converts an 8-character hash string into two 32-bit numbers and stores them
+ * in the temp values above.
+ * @param {string} hash
+ */
+jspb.utils.splitHash64 = function(hash) {
+  var a = hash.charCodeAt(0);
+  var b = hash.charCodeAt(1);
+  var c = hash.charCodeAt(2);
+  var d = hash.charCodeAt(3);
+  var e = hash.charCodeAt(4);
+  var f = hash.charCodeAt(5);
+  var g = hash.charCodeAt(6);
+  var h = hash.charCodeAt(7);
+
+  jspb.utils.split64Low = (a + (b << 8) + (c << 16) + (d << 24)) >>> 0;
+  jspb.utils.split64High = (e + (f << 8) + (g << 16) + (h << 24)) >>> 0;
+};
+
+
+/**
+ * Joins two 32-bit values into a 64-bit unsigned integer. Precision will be
+ * lost if the result is greater than 2^52.
+ * @param {number} bitsLow
+ * @param {number} bitsHigh
+ * @return {number}
+ */
+jspb.utils.joinUint64 = function(bitsLow, bitsHigh) {
+  return bitsHigh * jspb.BinaryConstants.TWO_TO_32 + bitsLow;
+};
+
+
+/**
+ * Joins two 32-bit values into a 64-bit signed integer. Precision will be lost
+ * if the result is greater than 2^52.
+ * @param {number} bitsLow
+ * @param {number} bitsHigh
+ * @return {number}
+ */
+jspb.utils.joinInt64 = function(bitsLow, bitsHigh) {
+  // If the high bit is set, do a manual two's complement conversion.
+  var sign = (bitsHigh & 0x80000000);
+  if (sign) {
+    bitsLow = (~bitsLow + 1) >>> 0;
+    bitsHigh = ~bitsHigh >>> 0;
+    if (bitsLow == 0) {
+      bitsHigh = (bitsHigh + 1) >>> 0;
+    }
+  }
+
+  var result = jspb.utils.joinUint64(bitsLow, bitsHigh);
+  return sign ? -result : result;
+};
+
+
+/**
+ * Joins two 32-bit values into a 64-bit unsigned integer and applies zigzag
+ * decoding. Precision will be lost if the result is greater than 2^52.
+ * @param {number} bitsLow
+ * @param {number} bitsHigh
+ * @return {number}
+ */
+jspb.utils.joinZigzag64 = function(bitsLow, bitsHigh) {
+  // Extract the sign bit and shift right by one.
+  var sign = bitsLow & 1;
+  bitsLow = ((bitsLow >>> 1) | (bitsHigh << 31)) >>> 0;
+  bitsHigh = bitsHigh >>> 1;
+
+  // Increment the split value if the sign bit was set.
+  if (sign) {
+    bitsLow = (bitsLow + 1) >>> 0;
+    if (bitsLow == 0) {
+      bitsHigh = (bitsHigh + 1) >>> 0;
+    }
+  }
+
+  var result = jspb.utils.joinUint64(bitsLow, bitsHigh);
+  return sign ? -result : result;
+};
+
+
+/**
+ * Joins two 32-bit values into a 32-bit IEEE floating point number and
+ * converts it back into a Javascript number.
+ * @param {number} bitsLow The low 32 bits of the binary number;
+ * @param {number} bitsHigh The high 32 bits of the binary number.
+ * @return {number}
+ */
+jspb.utils.joinFloat32 = function(bitsLow, bitsHigh) {
+  var sign = ((bitsLow >> 31) * 2 + 1);
+  var exp = (bitsLow >>> 23) & 0xFF;
+  var mant = bitsLow & 0x7FFFFF;
+
+  if (exp == 0xFF) {
+    if (mant) {
+      return NaN;
+    } else {
+      return sign * Infinity;
+    }
+  }
+
+  if (exp == 0) {
+    // Denormal.
+    return sign * Math.pow(2, -149) * mant;
+  } else {
+    return sign * Math.pow(2, exp - 150) *
+           (mant + Math.pow(2, 23));
+  }
+};
+
+
+/**
+ * Joins two 32-bit values into a 64-bit IEEE floating point number and
+ * converts it back into a Javascript number.
+ * @param {number} bitsLow The low 32 bits of the binary number;
+ * @param {number} bitsHigh The high 32 bits of the binary number.
+ * @return {number}
+ */
+jspb.utils.joinFloat64 = function(bitsLow, bitsHigh) {
+  var sign = ((bitsHigh >> 31) * 2 + 1);
+  var exp = (bitsHigh >>> 20) & 0x7FF;
+  var mant = jspb.BinaryConstants.TWO_TO_32 * (bitsHigh & 0xFFFFF) + bitsLow;
+
+  if (exp == 0x7FF) {
+    if (mant) {
+      return NaN;
+    } else {
+      return sign * Infinity;
+    }
+  }
+
+  if (exp == 0) {
+    // Denormal.
+    return sign * Math.pow(2, -1074) * mant;
+  } else {
+    return sign * Math.pow(2, exp - 1075) *
+           (mant + jspb.BinaryConstants.TWO_TO_52);
+  }
+};
+
+
+/**
+ * Joins two 32-bit values into an 8-character hash string.
+ * @param {number} bitsLow
+ * @param {number} bitsHigh
+ * @return {string}
+ */
+jspb.utils.joinHash64 = function(bitsLow, bitsHigh) {
+  var a = (bitsLow >>> 0) & 0xFF;
+  var b = (bitsLow >>> 8) & 0xFF;
+  var c = (bitsLow >>> 16) & 0xFF;
+  var d = (bitsLow >>> 24) & 0xFF;
+  var e = (bitsHigh >>> 0) & 0xFF;
+  var f = (bitsHigh >>> 8) & 0xFF;
+  var g = (bitsHigh >>> 16) & 0xFF;
+  var h = (bitsHigh >>> 24) & 0xFF;
+
+  return String.fromCharCode(a, b, c, d, e, f, g, h);
+};
+
+
+/**
+ * Individual digits for number->string conversion.
+ * @const {!Array.<number>}
+ */
+jspb.utils.DIGITS = [
+  '0', '1', '2', '3', '4', '5', '6', '7',
+  '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
+];
+
+
+/**
+ * Losslessly converts a 64-bit unsigned integer in 32:32 split representation
+ * into a decimal string.
+ * @param {number} bitsLow The low 32 bits of the binary number;
+ * @param {number} bitsHigh The high 32 bits of the binary number.
+ * @return {string} The binary number represented as a string.
+ */
+jspb.utils.joinUnsignedDecimalString = function(bitsLow, bitsHigh) {
+  // Skip the expensive conversion if the number is small enough to use the
+  // built-in conversions.
+  if (bitsHigh <= 0x1FFFFF) {
+    return '' + (jspb.BinaryConstants.TWO_TO_32 * bitsHigh + bitsLow);
+  }
+
+  // What this code is doing is essentially converting the input number from
+  // base-2 to base-1e7, which allows us to represent the 64-bit range with
+  // only 3 (very large) digits. Those digits are then trivial to convert to
+  // a base-10 string.
+
+  // The magic numbers used here are -
+  // 2^24 = 16777216 = (1,6777216) in base-1e7.
+  // 2^48 = 281474976710656 = (2,8147497,6710656) in base-1e7.
+
+  // Split 32:32 representation into 16:24:24 representation so our
+  // intermediate digits don't overflow.
+  var low = bitsLow & 0xFFFFFF;
+  var mid = (((bitsLow >>> 24) | (bitsHigh << 8)) >>> 0) & 0xFFFFFF;
+  var high = (bitsHigh >> 16) & 0xFFFF;
+
+  // Assemble our three base-1e7 digits, ignoring carries. The maximum
+  // value in a digit at this step is representable as a 48-bit integer, which
+  // can be stored in a 64-bit floating point number.
+  var digitA = low + (mid * 6777216) + (high * 6710656);
+  var digitB = mid + (high * 8147497);
+  var digitC = (high * 2);
+
+  // Apply carries from A to B and from B to C.
+  var base = 10000000;
+  if (digitA >= base) {
+    digitB += Math.floor(digitA / base);
+    digitA %= base;
+  }
+
+  if (digitB >= base) {
+    digitC += Math.floor(digitB / base);
+    digitB %= base;
+  }
+
+  // Convert base-1e7 digits to base-10, omitting leading zeroes.
+  var table = jspb.utils.DIGITS;
+  var start = false;
+  var result = '';
+
+  function emit(digit) {
+    var temp = base;
+    for (var i = 0; i < 7; i++) {
+      temp /= 10;
+      var decimalDigit = ((digit / temp) % 10) >>> 0;
+      if ((decimalDigit == 0) && !start) continue;
+      start = true;
+      result += table[decimalDigit];
+    }
+  }
+
+  if (digitC || start) emit(digitC);
+  if (digitB || start) emit(digitB);
+  if (digitA || start) emit(digitA);
+
+  return result;
+};
+
+
+/**
+ * Losslessly converts a 64-bit signed integer in 32:32 split representation
+ * into a decimal string.
+ * @param {number} bitsLow The low 32 bits of the binary number;
+ * @param {number} bitsHigh The high 32 bits of the binary number.
+ * @return {string} The binary number represented as a string.
+ */
+jspb.utils.joinSignedDecimalString = function(bitsLow, bitsHigh) {
+  // If we're treating the input as a signed value and the high bit is set, do
+  // a manual two's complement conversion before the decimal conversion.
+  var negative = (bitsHigh & 0x80000000);
+  if (negative) {
+    bitsLow = (~bitsLow + 1) >>> 0;
+    var carry = (bitsLow == 0) ? 1 : 0;
+    bitsHigh = (~bitsHigh + carry) >>> 0;
+  }
+
+  var result = jspb.utils.joinUnsignedDecimalString(bitsLow, bitsHigh);
+  return negative ? '-' + result : result;
+};
+
+
+/**
+ * Convert an 8-character hash string representing either a signed or unsigned
+ * 64-bit integer into its decimal representation without losing accuracy.
+ * @param {string} hash The hash string to convert.
+ * @param {boolean} signed True if we should treat the hash string as encoding
+ *     a signed integer.
+ * @return {string}
+ */
+jspb.utils.hash64ToDecimalString = function(hash, signed) {
+  jspb.utils.splitHash64(hash);
+  var bitsLow = jspb.utils.split64Low;
+  var bitsHigh = jspb.utils.split64High;
+  return signed ?
+      jspb.utils.joinSignedDecimalString(bitsLow, bitsHigh) :
+      jspb.utils.joinUnsignedDecimalString(bitsLow, bitsHigh);
+};
+
+
+/**
+ * Converts an array of 8-character hash strings into their decimal
+ * representations.
+ * @param {!Array.<string>} hashes The array of hash strings to convert.
+ * @param {boolean} signed True if we should treat the hash string as encoding
+ *     a signed integer.
+ * @return {!Array.<string>}
+ */
+jspb.utils.hash64ArrayToDecimalStrings = function(hashes, signed) {
+  var result = new Array(hashes.length);
+  for (var i = 0; i < hashes.length; i++) {
+    result[i] = jspb.utils.hash64ToDecimalString(hashes[i], signed);
+  }
+  return result;
+};
+
+
+/**
+ * Converts an 8-character hash string into its hexadecimal representation.
+ * @param {string} hash
+ * @return {string}
+ */
+jspb.utils.hash64ToHexString = function(hash) {
+  var temp = new Array(18);
+  temp[0] = '0';
+  temp[1] = 'x';
+
+  for (var i = 0; i < 8; i++) {
+    var c = hash.charCodeAt(7 - i);
+    temp[i * 2 + 2] = jspb.utils.DIGITS[c >> 4];
+    temp[i * 2 + 3] = jspb.utils.DIGITS[c & 0xF];
+  }
+
+  var result = temp.join('');
+  return result;
+};
+
+
+/**
+ * Converts a '0x<16 digits>' hex string into its hash string representation.
+ * @param {string} hex
+ * @return {string}
+ */
+jspb.utils.hexStringToHash64 = function(hex) {
+  hex = hex.toLowerCase();
+  goog.asserts.assert(hex.length == 18);
+  goog.asserts.assert(hex[0] == '0');
+  goog.asserts.assert(hex[1] == 'x');
+
+  var result = '';
+  for (var i = 0; i < 8; i++) {
+    var hi = jspb.utils.DIGITS.indexOf(hex[i * 2 + 2]);
+    var lo = jspb.utils.DIGITS.indexOf(hex[i * 2 + 3]);
+    result = String.fromCharCode(hi * 16 + lo) + result;
+  }
+
+  return result;
+};
+
+
+/**
+ * Convert an 8-character hash string representing either a signed or unsigned
+ * 64-bit integer into a Javascript number. Will lose accuracy if the result is
+ * larger than 2^52.
+ * @param {string} hash The hash string to convert.
+ * @param {boolean} signed True if the has should be interpreted as a signed
+ *     number.
+ * @return {number}
+ */
+jspb.utils.hash64ToNumber = function(hash, signed) {
+  jspb.utils.splitHash64(hash);
+  var bitsLow = jspb.utils.split64Low;
+  var bitsHigh = jspb.utils.split64High;
+  return signed ? jspb.utils.joinInt64(bitsLow, bitsHigh) :
+                  jspb.utils.joinUint64(bitsLow, bitsHigh);
+};
+
+
+/**
+ * Convert a Javascript number into an 8-character hash string. Will lose
+ * precision if the value is non-integral or greater than 2^64.
+ * @param {number} value The integer to convert.
+ * @return {string}
+ */
+jspb.utils.numberToHash64 = function(value) {
+  jspb.utils.splitInt64(value);
+  return jspb.utils.joinHash64(jspb.utils.split64Low,
+                                  jspb.utils.split64High);
+};
+
+
+/**
+ * Counts the number of contiguous varints in a buffer.
+ * @param {!Uint8Array} buffer The buffer to scan.
+ * @param {number} start The starting point in the buffer to scan.
+ * @param {number} end The end point in the buffer to scan.
+ * @return {number} The number of varints in the buffer.
+ */
+jspb.utils.countVarints = function(buffer, start, end) {
+  // Count how many high bits of each byte were set in the buffer.
+  var count = 0;
+  for (var i = start; i < end; i++) {
+    count += buffer[i] >> 7;
+  }
+
+  // The number of varints in the buffer equals the size of the buffer minus
+  // the number of non-terminal bytes in the buffer (those with the high bit
+  // set).
+  return (end - start) - count;
+};
+
+
+/**
+ * Counts the number of contiguous varint fields with the given field number in
+ * the buffer.
+ * @param {!Uint8Array} buffer The buffer to scan.
+ * @param {number} start The starting point in the buffer to scan.
+ * @param {number} end The end point in the buffer to scan.
+ * @param {number} field The field number to count.
+ * @return {number} The number of matching fields in the buffer.
+ */
+jspb.utils.countVarintFields = function(buffer, start, end, field) {
+  var count = 0;
+  var cursor = start;
+  var tag = field * 8 + jspb.BinaryConstants.WireType.VARINT;
+
+  if (tag < 128) {
+    // Single-byte field tag, we can use a slightly quicker count.
+    while (cursor < end) {
+      // Skip the field tag, or exit if we find a non-matching tag.
+      if (buffer[cursor++] != tag) return count;
+
+      // Field tag matches, we've found a valid field.
+      count++;
+
+      // Skip the varint.
+      while (1) {
+        var x = buffer[cursor++];
+        if ((x & 0x80) == 0) break;
+      }
+    }
+  } else {
+    while (cursor < end) {
+      // Skip the field tag, or exit if we find a non-matching tag.
+      var temp = tag;
+      while (temp > 128) {
+        if (buffer[cursor] != ((temp & 0x7F) | 0x80)) return count;
+        cursor++;
+        temp >>= 7;
+      }
+      if (buffer[cursor++] != temp) return count;
+
+      // Field tag matches, we've found a valid field.
+      count++;
+
+      // Skip the varint.
+      while (1) {
+        var x = buffer[cursor++];
+        if ((x & 0x80) == 0) break;
+      }
+    }
+  }
+  return count;
+};
+
+
+/**
+ * Counts the number of contiguous fixed32 fields with the given tag in the
+ * buffer.
+ * @param {!Uint8Array} buffer The buffer to scan.
+ * @param {number} start The starting point in the buffer to scan.
+ * @param {number} end The end point in the buffer to scan.
+ * @param {number} tag The tag value to count.
+ * @param {number} stride The number of bytes to skip per field.
+ * @return {number} The number of fields with a matching tag in the buffer.
+ * @private
+ */
+jspb.utils.countFixedFields_ =
+    function(buffer, start, end, tag, stride) {
+  var count = 0;
+  var cursor = start;
+
+  if (tag < 128) {
+    // Single-byte field tag, we can use a slightly quicker count.
+    while (cursor < end) {
+      // Skip the field tag, or exit if we find a non-matching tag.
+      if (buffer[cursor++] != tag) return count;
+
+      // Field tag matches, we've found a valid field.
+      count++;
+
+      // Skip the value.
+      cursor += stride;
+    }
+  } else {
+    while (cursor < end) {
+      // Skip the field tag, or exit if we find a non-matching tag.
+      var temp = tag;
+      while (temp > 128) {
+        if (buffer[cursor++] != ((temp & 0x7F) | 0x80)) return count;
+        temp >>= 7;
+      }
+      if (buffer[cursor++] != temp) return count;
+
+      // Field tag matches, we've found a valid field.
+      count++;
+
+      // Skip the value.
+      cursor += stride;
+    }
+  }
+  return count;
+};
+
+
+/**
+ * Counts the number of contiguous fixed32 fields with the given field number
+ * in the buffer.
+ * @param {!Uint8Array} buffer The buffer to scan.
+ * @param {number} start The starting point in the buffer to scan.
+ * @param {number} end The end point in the buffer to scan.
+ * @param {number} field The field number to count.
+ * @return {number} The number of matching fields in the buffer.
+ */
+jspb.utils.countFixed32Fields = function(buffer, start, end, field) {
+  var tag = field * 8 + jspb.BinaryConstants.WireType.FIXED32;
+  return jspb.utils.countFixedFields_(buffer, start, end, tag, 4);
+};
+
+
+/**
+ * Counts the number of contiguous fixed64 fields with the given field number
+ * in the buffer.
+ * @param {!Uint8Array} buffer The buffer to scan.
+ * @param {number} start The starting point in the buffer to scan.
+ * @param {number} end The end point in the buffer to scan.
+ * @param {number} field The field number to count
+ * @return {number} The number of matching fields in the buffer.
+ */
+jspb.utils.countFixed64Fields = function(buffer, start, end, field) {
+  var tag = field * 8 + jspb.BinaryConstants.WireType.FIXED64;
+  return jspb.utils.countFixedFields_(buffer, start, end, tag, 8);
+};
+
+
+/**
+ * Counts the number of contiguous delimited fields with the given field number
+ * in the buffer.
+ * @param {!Uint8Array} buffer The buffer to scan.
+ * @param {number} start The starting point in the buffer to scan.
+ * @param {number} end The end point in the buffer to scan.
+ * @param {number} field The field number to count.
+ * @return {number} The number of matching fields in the buffer.
+ */
+jspb.utils.countDelimitedFields = function(buffer, start, end, field) {
+  var count = 0;
+  var cursor = start;
+  var tag = field * 8 + jspb.BinaryConstants.WireType.DELIMITED;
+
+  while (cursor < end) {
+    // Skip the field tag, or exit if we find a non-matching tag.
+    var temp = tag;
+    while (temp > 128) {
+      if (buffer[cursor++] != ((temp & 0x7F) | 0x80)) return count;
+      temp >>= 7;
+    }
+    if (buffer[cursor++] != temp) return count;
+
+    // Field tag matches, we've found a valid field.
+    count++;
+
+    // Decode the length prefix.
+    var length = 0;
+    var shift = 1;
+    while (1) {
+      temp = buffer[cursor++];
+      length += (temp & 0x7f) * shift;
+      shift *= 128;
+      if ((temp & 0x80) == 0) break;
+    }
+
+    // Advance the cursor past the blob.
+    cursor += length;
+  }
+  return count;
+};
+
+
+/**
+ * Clones a scalar field. Pulling this out to a helper method saves us a few
+ * bytes of generated code.
+ * @param {Array} array
+ * @return {Array}
+ */
+jspb.utils.cloneRepeatedScalarField = function(array) {
+  return array ? array.slice() : null;
+};
+
+
+/**
+ * Clones an array of messages using the provided cloner function.
+ * @param {Array.<jspb.BinaryMessage>} messages
+ * @param {jspb.ClonerFunction} cloner
+ * @return {Array.<jspb.BinaryMessage>}
+ */
+jspb.utils.cloneRepeatedMessageField = function(messages, cloner) {
+  if (messages === null) return null;
+  var result = [];
+  for (var i = 0; i < messages.length; i++) {
+    result.push(cloner(messages[i]));
+  }
+  return result;
+};
+
+
+/**
+ * Clones an array of byte blobs.
+ * @param {Array.<Uint8Array>} blobs
+ * @return {Array.<Uint8Array>}
+ */
+jspb.utils.cloneRepeatedBlobField = function(blobs) {
+  if (blobs === null) return null;
+  var result = [];
+  for (var i = 0; i < blobs.length; i++) {
+    result.push(new Uint8Array(blobs[i]));
+  }
+  return result;
+};
+
+
+/**
+ * String-ify bytes for text format. Should be optimized away in non-debug.
+ * The returned string uses \xXX escapes for all values and is itself quoted.
+ * [1, 31] serializes to '"\x01\x1f"'.
+ * @param {jspb.ByteSource} byteSource The bytes to serialize.
+ * @param {boolean=} opt_stringIsRawBytes The string is interpreted as a series
+ * of raw bytes rather than base64 data.
+ * @return {string} Stringified bytes for text format.
+ */
+jspb.utils.debugBytesToTextFormat = function(byteSource,
+                                                opt_stringIsRawBytes) {
+  var s = '"';
+  if (byteSource) {
+    var bytes =
+        jspb.utils.byteSourceToUint8Array(byteSource, opt_stringIsRawBytes);
+    for (var i = 0; i < bytes.length; i++) {
+      s += '\\x';
+      if (bytes[i] < 16) s += '0';
+      s += bytes[i].toString(16);
+    }
+  }
+  return s + '"';
+};
+
+
+/**
+ * String-ify a scalar for text format. Should be optimized away in non-debug.
+ * @param {string|number|boolean} scalar The scalar to stringify.
+ * @return {string} Stringified scalar for text format.
+ */
+jspb.utils.debugScalarToTextFormat = function(scalar) {
+  if (goog.isString(scalar)) {
+    return goog.string.quote(scalar);
+  } else {
+    return scalar.toString();
+  }
+};
+
+
+/**
+ * Utility function: convert a string with codepoints 0--255 inclusive to a
+ * Uint8Array. If any codepoints greater than 255 exist in the string, throws an
+ * exception.
+ * @param {string} str
+ * @return {!Uint8Array}
+ * @private
+ */
+jspb.utils.stringToByteArray_ = function(str) {
+  var arr = new Uint8Array(str.length);
+  for (var i = 0; i < str.length; i++) {
+    var codepoint = str.charCodeAt(i);
+    if (codepoint > 255) {
+      throw new Error('Conversion error: string contains codepoint ' +
+                      'outside of byte range');
+    }
+    arr[i] = codepoint;
+  }
+  return arr;
+};
+
+
+/**
+ * Converts any type defined in jspb.ByteSource into a Uint8Array.
+ * @param {!jspb.ByteSource} data
+ * @param {boolean=} opt_stringIsRawBytes Interpret a string as a series of raw
+ * bytes (encoded as codepoints 0--255 inclusive) rather than base64 data
+ * (default behavior).
+ * @return {!Uint8Array}
+ * @suppress {invalidCasts}
+ */
+jspb.utils.byteSourceToUint8Array = function(data, opt_stringIsRawBytes) {
+  if (data.constructor === Uint8Array) {
+    return /** @type {!Uint8Array} */(data);
+  }
+
+  if (data.constructor === ArrayBuffer) {
+    data = /** @type {!ArrayBuffer} */(data);
+    return /** @type {!Uint8Array} */(new Uint8Array(data));
+  }
+
+  if (data.constructor === Array) {
+    data = /** @type {!Array.<number>} */(data);
+    return /** @type {!Uint8Array} */(new Uint8Array(data));
+  }
+
+  if (data.constructor === String) {
+    data = /** @type {string} */(data);
+    if (opt_stringIsRawBytes) {
+      return jspb.utils.stringToByteArray_(data);
+    } else {
+      return goog.crypt.base64.decodeStringToUint8Array(data);
+    }
+  }
+
+  goog.asserts.fail('Type not convertible to Uint8Array.');
+  return /** @type {!Uint8Array} */(new Uint8Array(0));
+};