mkimage : Split out and clean pbl_crc32 for use by other image types

The crc32 used by pblimgae is NOT the same as zlib crc32.

The pbl_crc32 is useful for other purposes in mkimage so split it out.

While we are about it, clean up redundant and confusing code.

Signed-off-by: Charles Manning <cdhmanning@gmail.com>

tools/pbl_crc32.c

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2012 Freescale Semiconductor, Inc.
+ *
+ * Cleaned up and refactored by Charles Manning.
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+#include "pblimage.h"
+
+static uint32_t crc_table[256];
+static int crc_table_valid;
+
+static void make_crc_table(void)
+{
+	uint32_t mask;
+	int i, j;
+	uint32_t poly; /* polynomial exclusive-or pattern */
+
+	if (crc_table_valid)
+		return;
+
+	/*
+	 * the polynomial used by PBL is 1 + x1 + x2 + x4 + x5 + x7 + x8 + x10
+	 * + x11 + x12 + x16 + x22 + x23 + x26 + x32.
+	 */
+	poly = 0x04c11db7;
+
+	for (i = 0; i < 256; i++) {
+		mask = i << 24;
+		for (j = 0; j < 8; j++) {
+			if (mask & 0x80000000)
+				mask = (mask << 1) ^ poly;
+			else
+				mask <<= 1;
+		}
+		crc_table[i] = mask;
+	}
+
+	crc_table_valid = 1;
+}
+
+uint32_t pbl_crc32(uint32_t in_crc, const char *buf, uint32_t len)
+{
+	uint32_t crc32_val;
+	int i;
+
+	make_crc_table();
+
+	crc32_val = ~in_crc;
+
+	for (i = 0; i < len; i++)
+		crc32_val = (crc32_val << 8) ^
+			crc_table[(crc32_val >> 24) ^ (*buf++ & 0xff)];
+
+	return crc32_val;
+}