Add base crc64 for small files

www/lib/CoreLibs/Create/Crc64.php

@@ -0,0 +1,106 @@
+<?php
+
+/**
+ * AUTHOR: Clemens Schwaighofer
+ * CREATED: 2026/10/15
+ * DESCRIPTION:
+ * AWS CRC64 Implementation
+ * This can be replaced by:
+ * https://github.com/awesomized/crc-fast-php-ext
+ * This this needs: https://github.com/awesomized/crc-fast-rust
+ * installed, and there is no easy binary package available.
+ *
+ * NOTE: for anything larger than 10MB this is absolutely NOT recommended
+*/
+
+declare(strict_types=1);
+
+namespace CoreLibs\Create;
+
+class Crc64
+{
+	/**
+	 * Internal CRC64 calculation for a given data string.
+	 *
+	 * @param  string $data
+	 * @param  int    $crc
+	 * @return int
+	 */
+	private function crc64Calc(string $data, int $crc = 0): int
+	{
+		static $table = null;
+		if ($table === null) {
+			// reflected poly 0x9A6C9329AC4BC9B5 (built from halves, too big for a PHP int literal)
+			$poly = (0x9A6C9329 << 32) | 0xAC4BC9B5;
+			$table = [];
+			for ($i = 0; $i < 256; $i++) {
+				$c = $i;
+				for ($k = 0; $k < 8; $k++) {
+					// logical right shift: PHP >> is arithmetic, so mask off the sign bit
+					$c = ($c & 1)
+						? ((($c >> 1) & PHP_INT_MAX) ^ $poly)
+						: (($c >> 1) & PHP_INT_MAX);
+				}
+				$table[$i] = $c;
+			}
+		}
+		$crc = ~$crc; // xor 0xFFFFFFFFFFFFFFFF
+		foreach (unpack('C*', $data) ?: [] as $b) {
+			$crc = $table[($crc ^ $b) & 0xFF] ^ (($crc >> 8) & 0x00FFFFFFFFFFFFFF);
+		}
+		return ~$crc;
+	}
+
+	/**
+	 * Returns int value of the CRC64 checksum for the given file.
+	 *
+	 * @param  string $path
+	 * @param  int<1,16777216> $chunkSize
+	 * @return int
+	 */
+	private function crc64CalcFile(string $path, int $chunkSize = 8 * 1024 * 1024): int
+	{
+		$fh = fopen($path, 'rb');
+		if ($fh === false) {
+			throw new \RuntimeException("Cannot open $path");
+		}
+		$crc = 0;
+		try {
+			while (!feof($fh)) {
+				$chunk = fread($fh, $chunkSize);
+				if ($chunk === false) {
+					throw new \RuntimeException("Read error on $path");
+				}
+				$crc = $this->crc64Calc($chunk, $crc);
+			}
+		} finally {
+			fclose($fh);
+		}
+		return $crc;
+	}
+
+	/**
+	 * Returns the Base64-encoded CRC64 checksum for the given file.
+	 *
+	 * @param  string $path
+	 * @return string
+	 */
+	public static function crc64(string $path): string
+	{
+		return base64_encode(pack('J', (new self())->crc64CalcFile($path))); // J = uint64 big-endian
+	}
+
+	/**
+	 * Returns the 16-character lowercase hexadecimal CRC64 checksum for the given file.
+	 * Same as base64.b64decode(...).hex()
+	 *
+	 * @param  string $path
+	 * @return string
+	 */
+	public static function crc64hex(string $path): string
+	{
+		return sprintf('%016x', (new self())->crc64CalcFile($path));
+	}
+}
+
+// __END__