A few more changes to improve the support of negative numbers.

protocolbuffers.inc.php

@@ -217,7 +217,6 @@ public static function size_varint($value) {
 	 */
 	public static function decode_varint($encoded) {
 		checkArgument(is_string($encoded), 'encoded value must be a string of bytes');
-		checkArgument($encoded !== '', 'encoded value contains no bytes');
 
 		$len = strlen($encoded);
 		if ($len <= self::MAX_PHP_INT_VARINT_LEN) { // TODO lower this on PHP32.
@@ -238,17 +237,15 @@ public static function decode_signed_varint($encoded) {
 			// signed extension. To help maintain a accuracy we do it manually
 			// over the bytes of the varint, by flipping the bits and adding one.
 
-			// All but the last bit should be disacard (as it would be above 64bits)
-			$encoded[$len - 1] = chr(ord($encoded[$len - 1]) & 0x01);
-			$lastZero = $len - 1;
-			for ($i = $len - 2; $i >= 0; $i--) {
+			$len--;
+			for ($i = 0; $i < $len; $i++) {
 				$encoded[$i] = chr(~(ord($encoded[$i]) & 0x7F));
-				if ($encoded[$i] === "\x80" && $lastZero === $i + 1) {
-					$lastZero = $i + 1;
-				}
 			}
 
-			$encoded = substr($encoded, 0, $lastZero);
+			// Drop the last digit as it's above 64bit and not used
+			$encoded = substr($encoded, 0, $len);
+			$encoded = rtrim($encoded, "\x80"); // TODO change this to rtrim(\xff) and move above the loop
+
 			return -self::decode_varint($encoded) - 1;
 		} else {
 			return self::decode_varint($encoded);
@@ -553,16 +550,31 @@ public static function encode_varint_float($value) {
 	public static function encode_varint($value) {
 
 		if ($value < 0) {
-			$value = -$value + 1;
+			$value = -($value + 1);
+			$negative = true;
+		} else {
+			$negative = false;
 		}
 
 		if (is_int($value)) {
-			return self::encode_varint_float($value);
+			$encoded = self::encode_varint_int($value);
 		} elseif (is_float($value)) {
-			return self::encode_varint_float($value);
+			$encoded = self::encode_varint_float($value);
 		} else {
 			throw new InvalidArgumentException('value must be a integer or float');
 		}
+
+		if ($negative) {
+			$len = strlen($encoded);
+			for ($i = $len - 1; $i >= 0; $i--) {
+				$encoded[$i] = chr(~(ord($encoded[$i])) | 0x80);
+			}
+
+			// Now sign extend
+			$encoded = str_pad($encoded, 9, "\xff", STR_PAD_RIGHT) . "\x01";
+		}
+
+		return $encoded;
 	}
 
 	/**

tests/protocolbuffers_test.php

@@ -8,21 +8,24 @@ class VarintProtobufTest extends ProtobufTestCase {
 
 	var $tests = array(
 		-9223372036854775808 => "\x80\x80\x80\x80\x80\x80\x80\x80\x80\x01", // -2^63
-		-9223372036854775800 => "\x88\x80\x80\x80\x80\x80\x80\x80\x80\x01",
+		-9223372036854775807 => "\x81\x80\x80\x80\x80\x80\x80\x80\x80\x01", // -2^63 + 1
+		-9223372036854775800 => "\x88\x80\x80\x80\x80\x80\x80\x80\x80\x01", // -2^63 + 8
 
-		-72057594037927935   => "\x81\x80\x80\x80\x80\x80\x80\x80\xff\x01", // -2^56 - 1
+		-72057594037927937   => "\xff\xff\xff\xff\xff\xff\xff\xff\xfe\x01", // -2^56 - 1
 		-72057594037927936   => "\x80\x80\x80\x80\x80\x80\x80\x80\xff\x01", // -2^56
-		-72057594037927937   => "\xff\xff\xff\xff\xff\xff\xff\xff\xfe\x01", // -2^56 + 1
+		-72057594037927935   => "\x81\x80\x80\x80\x80\x80\x80\x80\xff\x01", // -2^56 + 1
 
 		-2147483648          => "\x80\x80\x80\x80\xf8\xff\xff\xff\xff\x01", // -2^31
 		-255                 => "\x81\xfe\xff\xff\xff\xff\xff\xff\xff\x01",
 		-16                  => "\xf0\xff\xff\xff\xff\xff\xff\xff\xff\x01",
 		-8                   => "\xf8\xff\xff\xff\xff\xff\xff\xff\xff\x01",
+		-3                   => "\xfd\xff\xff\xff\xff\xff\xff\xff\xff\x01",
 		-2                   => "\xfe\xff\xff\xff\xff\xff\xff\xff\xff\x01",
 		-1                   => "\xff\xff\xff\xff\xff\xff\xff\xff\xff\x01",
 		0                    => "\x00",
 		1                    => "\x01",
 		2                    => "\x02",
+		3                    => "\x03",
 		127                  => "\x7F",
 		128                  => "\x80\x01",
 		255                  => "\xff\x01",