aboutsummaryrefslogtreecommitdiff
path: root/projects/cli-test/crc32.c
diff options
context:
space:
mode:
authorFredrik Thulin <fredrik@thulin.net>2016-05-15 10:42:23 +0200
committerFredrik Thulin <fredrik@thulin.net>2016-05-15 10:43:03 +0200
commit9b73356f2831800d2328827998e1e5b2a1994b68 (patch)
tree194357028a78b8ef92e4914074c2b3c51df5b17b /projects/cli-test/crc32.c
parentcc07ee6bfcf4721254145ef388196be82532fd4a (diff)
add simple filetransfer poc
Diffstat (limited to 'projects/cli-test/crc32.c')
-rw-r--r--projects/cli-test/crc32.c62
1 files changed, 62 insertions, 0 deletions
diff --git a/projects/cli-test/crc32.c b/projects/cli-test/crc32.c
new file mode 100644
index 0000000..4d1a0bc
--- /dev/null
+++ b/projects/cli-test/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);
+}