Implement phpiredis_utils_crc16().

This new utility function is useful to implement redis-cluster on top
of phpiredis since crc16 is at the base of the algorithm used to map
keys to hash slots. Compared to a pure-PHP implementation of CRC16 it
is ~10 times faster (PHP 7.0.7) when calculating the hash for strings
of 10 bytes. Examples of PHP projects that can benefit from it in the
immediate are nrk/predis and jarnix/LiteRedis.

phpiredis uses the reference implementation in ANSI C made available
on http://redis.io/topics/cluster-spec#appendix (compatible license).

config.m4

@@ -37,5 +37,5 @@ if test "$PHP_PHPIREDIS" = "yes"; then
 
   AC_DEFINE(HAVE_PHPIREDIS, 1, [Whether you have phpiredis])
   PHP_SUBST(PHPIREDIS_SHARED_LIBADD)
-  PHP_NEW_EXTENSION(phpiredis, phpiredis.c, $ext_shared)
+  PHP_NEW_EXTENSION(phpiredis, phpiredis.c crc16.c, $ext_shared)
 fi

crc16.c

@@ -0,0 +1,88 @@
+/*
+ * Copyright 2001-2010 Georges Menie (www.menie.org)
+ * Copyright 2010-2012 Salvatore Sanfilippo (adapted to Redis coding style)
+ * All rights reserved.
+ *
+ * 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 the University of California, Berkeley 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 REGENTS 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 REGENTS AND 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.
+ */
+
+/* CRC16 implementation according to CCITT standards.
+ *
+ * Note by @antirez: this is actually the XMODEM CRC 16 algorithm, using the
+ * following parameters:
+ *
+ * Name                       : "XMODEM", also known as "ZMODEM", "CRC-16/ACORN"
+ * Width                      : 16 bit
+ * Poly                       : 1021 (That is actually x^16 + x^12 + x^5 + 1)
+ * Initialization             : 0000
+ * Reflect Input byte         : False
+ * Reflect Output CRC         : False
+ * Xor constant to output CRC : 0000
+ * Output for "123456789"     : 31C3
+ */
+
+#include <stdint.h>
+
+static const uint16_t crc16tab[256]= {
+    0x0000,0x1021,0x2042,0x3063,0x4084,0x50a5,0x60c6,0x70e7,
+    0x8108,0x9129,0xa14a,0xb16b,0xc18c,0xd1ad,0xe1ce,0xf1ef,
+    0x1231,0x0210,0x3273,0x2252,0x52b5,0x4294,0x72f7,0x62d6,
+    0x9339,0x8318,0xb37b,0xa35a,0xd3bd,0xc39c,0xf3ff,0xe3de,
+    0x2462,0x3443,0x0420,0x1401,0x64e6,0x74c7,0x44a4,0x5485,
+    0xa56a,0xb54b,0x8528,0x9509,0xe5ee,0xf5cf,0xc5ac,0xd58d,
+    0x3653,0x2672,0x1611,0x0630,0x76d7,0x66f6,0x5695,0x46b4,
+    0xb75b,0xa77a,0x9719,0x8738,0xf7df,0xe7fe,0xd79d,0xc7bc,
+    0x48c4,0x58e5,0x6886,0x78a7,0x0840,0x1861,0x2802,0x3823,
+    0xc9cc,0xd9ed,0xe98e,0xf9af,0x8948,0x9969,0xa90a,0xb92b,
+    0x5af5,0x4ad4,0x7ab7,0x6a96,0x1a71,0x0a50,0x3a33,0x2a12,
+    0xdbfd,0xcbdc,0xfbbf,0xeb9e,0x9b79,0x8b58,0xbb3b,0xab1a,
+    0x6ca6,0x7c87,0x4ce4,0x5cc5,0x2c22,0x3c03,0x0c60,0x1c41,
+    0xedae,0xfd8f,0xcdec,0xddcd,0xad2a,0xbd0b,0x8d68,0x9d49,
+    0x7e97,0x6eb6,0x5ed5,0x4ef4,0x3e13,0x2e32,0x1e51,0x0e70,
+    0xff9f,0xefbe,0xdfdd,0xcffc,0xbf1b,0xaf3a,0x9f59,0x8f78,
+    0x9188,0x81a9,0xb1ca,0xa1eb,0xd10c,0xc12d,0xf14e,0xe16f,
+    0x1080,0x00a1,0x30c2,0x20e3,0x5004,0x4025,0x7046,0x6067,
+    0x83b9,0x9398,0xa3fb,0xb3da,0xc33d,0xd31c,0xe37f,0xf35e,
+    0x02b1,0x1290,0x22f3,0x32d2,0x4235,0x5214,0x6277,0x7256,
+    0xb5ea,0xa5cb,0x95a8,0x8589,0xf56e,0xe54f,0xd52c,0xc50d,
+    0x34e2,0x24c3,0x14a0,0x0481,0x7466,0x6447,0x5424,0x4405,
+    0xa7db,0xb7fa,0x8799,0x97b8,0xe75f,0xf77e,0xc71d,0xd73c,
+    0x26d3,0x36f2,0x0691,0x16b0,0x6657,0x7676,0x4615,0x5634,
+    0xd94c,0xc96d,0xf90e,0xe92f,0x99c8,0x89e9,0xb98a,0xa9ab,
+    0x5844,0x4865,0x7806,0x6827,0x18c0,0x08e1,0x3882,0x28a3,
+    0xcb7d,0xdb5c,0xeb3f,0xfb1e,0x8bf9,0x9bd8,0xabbb,0xbb9a,
+    0x4a75,0x5a54,0x6a37,0x7a16,0x0af1,0x1ad0,0x2ab3,0x3a92,
+    0xfd2e,0xed0f,0xdd6c,0xcd4d,0xbdaa,0xad8b,0x9de8,0x8dc9,
+    0x7c26,0x6c07,0x5c64,0x4c45,0x3ca2,0x2c83,0x1ce0,0x0cc1,
+    0xef1f,0xff3e,0xcf5d,0xdf7c,0xaf9b,0xbfba,0x8fd9,0x9ff8,
+    0x6e17,0x7e36,0x4e55,0x5e74,0x2e93,0x3eb2,0x0ed1,0x1ef0
+};
+
+uint16_t crc16(const char *buf, int len) {
+    int counter;
+    uint16_t crc = 0;
+    for (counter = 0; counter < len; counter++)
+            crc = (crc<<8) ^ crc16tab[((crc>>8) ^ *buf++)&0x00FF];
+    return crc;
+}

php_phpiredis.h

@@ -5,6 +5,8 @@
 #include "config.h"
 #endif
 
+uint16_t crc16(const char *buf, int len);
+
 #include "php.h"
 #include "php_ini.h"
 
@@ -29,6 +31,7 @@ PHP_FUNCTION(phpiredis_reader_get_reply);
 PHP_FUNCTION(phpiredis_reader_destroy);
 PHP_FUNCTION(phpiredis_reader_set_error_handler);
 PHP_FUNCTION(phpiredis_reader_set_status_handler);
+PHP_FUNCTION(phpiredis_utils_crc16);
 
 extern zend_module_entry phpiredis_module_entry;
 #define phpext_phpiredis_ptr &phpiredis_module_entry

phpiredis.c

@@ -925,6 +925,21 @@ PHP_FUNCTION(phpiredis_reader_get_state)
     }
 }
 
+PHP_FUNCTION(phpiredis_utils_crc16)
+{
+    char *buf;
+    PHPIREDIS_LEN_TYPE buf_size;
+    uint16_t crc;
+
+    if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s", &buf, &buf_size) == FAILURE) {
+        return;
+    }
+
+    crc = crc16(buf, buf_size);
+
+    ZVAL_LONG(return_value, crc);
+}
+
 // -------------------------------------------------------------------------- //
 
 PHP_MINIT_FUNCTION(phpiredis)
@@ -969,6 +984,7 @@ static zend_function_entry phpiredis_functions[] = {
     PHP_FE(phpiredis_reader_destroy, NULL)
     PHP_FE(phpiredis_reader_set_error_handler, NULL)
     PHP_FE(phpiredis_reader_set_status_handler, NULL)
+    PHP_FE(phpiredis_utils_crc16, NULL)
     {NULL, NULL, NULL}
 };
 

tests/utils_001.phpt

@@ -0,0 +1,31 @@
+--TEST--
+[UTILS] Calculate the CRC16 of strings
+
+--SKIPIF--
+<?php
+require_once 'testsuite_skipif.inc';
+
+--FILE--
+<?php
+var_dump(phpiredis_utils_crc16('key:000'));
+var_dump(phpiredis_utils_crc16('key:001'));
+var_dump(phpiredis_utils_crc16('key:002'));
+var_dump(phpiredis_utils_crc16('key:003'));
+var_dump(phpiredis_utils_crc16('key:004'));
+var_dump(phpiredis_utils_crc16('key:005'));
+var_dump(phpiredis_utils_crc16('key:006'));
+var_dump(phpiredis_utils_crc16('key:007'));
+var_dump(phpiredis_utils_crc16('key:008'));
+var_dump(phpiredis_utils_crc16('key:009'));
+
+--EXPECTF--
+int(58359)
+int(62422)
+int(50101)
+int(54164)
+int(41843)
+int(45906)
+int(33585)
+int(37648)
+int(25343)
+int(29406)