Down integrate from Google internal.

2 files changed, 85 insertions, 0 deletions

diff --git a/js/binary/utils.js b/js/binary/utils.js
index 875ff955..51405553 100644
--- a/js/binary/utils.js
+++ b/js/binary/utils.js
@@ -568,6 +568,56 @@ jspb.utils.hash64ArrayToDecimalStrings = function(hashes, signed) {
 
 
 /**
+ * Converts a signed or unsigned decimal string into its hash string
+ * representation.
+ * @param {string} dec
+ * @return {string}
+ */
+jspb.utils.decimalStringToHash64 = function(dec) {
+  goog.asserts.assert(dec.length > 0);
+
+  // Check for minus sign.
+  var minus = false;
+  if (dec[0] === '-') {
+    minus = true;
+    dec = dec.slice(1);
+  }
+
+  // Store result as a byte array.
+  var resultBytes = [0, 0, 0, 0, 0, 0, 0, 0];
+
+  // Set result to m*result + c.
+  function muladd(m, c) {
+    for (var i = 0; i < 8 && (m !== 1 || c > 0); i++) {
+      var r = m * resultBytes[i] + c;
+      resultBytes[i] = r & 0xFF;
+      c = r >>> 8;
+    }
+  }
+
+  // Negate the result bits.
+  function neg() {
+    for (var i = 0; i < 8; i++) {
+      resultBytes[i] = (~resultBytes[i]) & 0xFF;
+    }
+  }
+
+  // For each decimal digit, set result to 10*result + digit.
+  for (var i = 0; i < dec.length; i++) {
+    muladd(10, jspb.utils.DIGITS.indexOf(dec[i]));
+  }
+
+  // If there's a minus sign, convert into two's complement.
+  if (minus) {
+    neg();
+    muladd(1, 1);
+  }
+
+  return String.fromCharCode.apply(null, resultBytes);
+};
+
+
+/**
  * Converts an 8-character hash string into its hexadecimal representation.
  * @param {string} hash
  * @return {string}
diff --git a/js/binary/utils_test.js b/js/binary/utils_test.js
index 518d7597..d27e5ea2 100644
--- a/js/binary/utils_test.js
+++ b/js/binary/utils_test.js
@@ -197,6 +197,41 @@ describe('binaryUtilsTest', function() {
     assertEquals('123456789123456789', result[2]);
   });
 
+  /*
+   * Going from decimal strings to hash strings should be lossless.
+   */
+  it('testDecimalToHashConversion', function() {
+    var result;
+    var convert = jspb.utils.decimalStringToHash64;
+
+    result = convert('0');
+    assertEquals(String.fromCharCode.apply(null,
+      [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]), result);
+
+    result = convert('-1');
+    assertEquals(String.fromCharCode.apply(null,
+      [0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF]), result);
+
+    result = convert('18446744073709551615');
+    assertEquals(String.fromCharCode.apply(null,
+      [0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF]), result);
+
+    result = convert('9223372036854775808');
+    assertEquals(String.fromCharCode.apply(null,
+      [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80]), result);
+
+    result = convert('-9223372036854775808');
+    assertEquals(String.fromCharCode.apply(null,
+      [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80]), result);
+
+    result = convert('123456789123456789');
+    assertEquals(String.fromCharCode.apply(null,
+      [0x15, 0x5F, 0xD0, 0xAC, 0x4B, 0x9B, 0xB6, 0x01]), result);
+
+    result = convert('-123456789123456789');
+    assertEquals(String.fromCharCode.apply(null,
+      [0xEB, 0xA0, 0x2F, 0x53, 0xB4, 0x64, 0x49, 0xFE]), result);
+  });
 
   /**
    * Going from hash strings to hex strings should be lossless.