1 files changed, 59 insertions, 0 deletions

diff --git a/lib/xz/xz_crc32.c b/lib/xz/xz_crc32.c
new file mode 100644
index 000000000000..34532d14fd4c
--- /dev/null
+++ b/lib/xz/xz_crc32.c
@@ -0,0 +1,59 @@
+/*
+ * CRC32 using the polynomial from IEEE-802.3
+ *
+ * Authors: Lasse Collin <lasse.collin@tukaani.org>
+ *          Igor Pavlov <http://7-zip.org/>
+ *
+ * This file has been put into the public domain.
+ * You can do whatever you want with this file.
+ */
+
+/*
+ * This is not the fastest implementation, but it is pretty compact.
+ * The fastest versions of xz_crc32() on modern CPUs without hardware
+ * accelerated CRC instruction are 3-5 times as fast as this version,
+ * but they are bigger and use more memory for the lookup table.
+ */
+
+#include "xz_private.h"
+
+/*
+ * STATIC_RW_DATA is used in the pre-boot environment on some architectures.
+ * See <linux/decompress/mm.h> for details.
+ */
+#ifndef STATIC_RW_DATA
+#       define STATIC_RW_DATA static
+#endif
+
+STATIC_RW_DATA uint32_t xz_crc32_table[256];
+
+XZ_EXTERN void xz_crc32_init(void)
+{
+        const uint32_t poly = 0xEDB88320;
+
+        uint32_t i;
+        uint32_t j;
+        uint32_t r;
+
+        for (i = 0; i < 256; ++i) {
+                r = i;
+                for (j = 0; j < 8; ++j)
+                        r = (r >> 1) ^ (poly & ~((r & 1) - 1));
+
+                xz_crc32_table[i] = r;
+        }
+
+        return;
+}
+
+XZ_EXTERN uint32_t xz_crc32(const uint8_t *buf, size_t size, uint32_t crc)
+{
+        crc = ~crc;
+
+        while (size != 0) {
+                crc = xz_crc32_table[*buf++ ^ (crc & 0xFF)] ^ (crc >> 8);
+                --size;
+        }
+
+        return ~crc;
+}