1 files changed, 62 insertions, 0 deletions
diff --git a/projects/hsm/crc32.c b/projects/hsm/crc32.c
new file mode 100644
index 0000000..4d1a0bc
--- /dev/null
+++ b/projects/hsm/crc32.c
@@ -0,0 +1,62 @@
+/* Reference code from RFC1952. Not meant to be used outside test code. */
+
+#include "stm32f4xx_hal.h"
+
+
+/* Table of CRCs of all 8-bit messages. */
+unsigned long crc_table[256];
+
+/* Flag: has the table been computed? Initially false. */
+int crc_table_computed = 0;
+
+/* Make the table for a fast CRC. */
+void make_crc_table(void)
+{
+    unsigned long c;
+
+    int n, k;
+    for (n = 0; n < 256; n++) {
+	c = (unsigned long) n;
+	for (k = 0; k < 8; k++) {
+	    if (c & 1) {
+		c = 0xedb88320L ^ (c >> 1);
+	    } else {
+		c = c >> 1;
+	    }
+	}
+	crc_table[n] = c;
+    }
+    crc_table_computed = 1;
+}
+
+/*
+  Update a running crc with the bytes buf[0..len-1] and return
+  the updated crc. The crc should be initialized to zero. Pre- and
+  post-conditioning (one's complement) is performed within this
+  function so it shouldn't be done by the caller. Usage example:
+
+  unsigned long crc = 0L;
+
+  while (read_buffer(buffer, length) != EOF) {
+  crc = update_crc(crc, buffer, length);
+  }
+  if (crc != original_crc) error();
+*/
+uint32_t update_crc(uint32_t crc, uint8_t *buf, int len)
+{
+    unsigned long c = crc ^ 0xffffffffL;
+    int n;
+
+    if (!crc_table_computed)
+	make_crc_table();
+    for (n = 0; n < len; n++) {
+	c = crc_table[(c ^ buf[n]) & 0xff] ^ (c >> 8);
+    }
+    return c ^ 0xffffffffL;
+}
+
+/* Return the CRC of the bytes buf[0..len-1]. */
+unsigned long crc(unsigned char *buf, int len)
+{
+    return update_crc(0L, buf, len);
+}