From 92ce4da1158aabd1a45d3a5044a5e5fd7bac3c41 Mon Sep 17 00:00:00 2001 From: Fredrik Thulin Date: Fri, 27 May 2016 15:56:16 +0200 Subject: DFU working - but no signature validation for now. --- projects/bootloader/crc32.c | 62 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) create mode 100644 projects/bootloader/crc32.c (limited to 'projects/bootloader/crc32.c') diff --git a/projects/bootloader/crc32.c b/projects/bootloader/crc32.c new file mode 100644 index 0000000..4d1a0bc --- /dev/null +++ b/projects/bootloader/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); +} -- cgit v1.2.3