Add utility function to compute crc32 check sums

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 31 insertions, 0 deletions

diff --git a/lib/util/crc32.c b/lib/util/crc32.c
new file mode 100644
index 0000000..ffe0044
--- /dev/null
+++ b/lib/util/crc32.c
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "config.h"
+#include "util.h"
+
+/*
+  Karl Malbrain's compact CRC-32. See "A compact CCITT crc16 and crc32 C
+  implementation that balances processor cache usage against speed"
+ */
+static const uint32_t s_crc32[16] = {
+	0x00000000, 0x1DB71064, 0x3B6E20C8, 0x26D930AC,
+	0x76DC4190, 0x6B6B51F4, 0x4DB26158, 0x5005713C,
+	0xEDB88320, 0xF00F9344, 0xD6D6A3E8, 0xCB61B38C,
+	0x9B64C2B0, 0x86D3D2D4, 0xA00AE278, 0xBDBDF21C
+};
+
+uint32_t update_crc32(uint32_t crc, const void *data, size_t size)
+{
+	const uint8_t *ptr = data;
+	uint8_t b;
+
+	crc = ~crc;
+
+	while (size--) {
+		b = *ptr++;
+
+		crc = (crc >> 4) ^ s_crc32[(crc & 0x0F) ^ (b & 0x0F)];
+		crc = (crc >> 4) ^ s_crc32[(crc & 0x0F) ^ (b >> 4)];
+	}
+
+	return ~crc;
+}