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106 lines
1.9 KiB
106 lines
1.9 KiB
9 years ago
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#include "esp8266.h"
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#include <stdbool.h>
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#include "sbmp_config.h"
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#include "sbmp_checksum.h"
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#if SBMP_HAS_CRC32
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#include "crc32.h"
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#endif
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/** Get nr of bytes in a checksum */
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uint8_t chksum_length(SBMP_CksumType cksum_type)
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{
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switch (cksum_type) {
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case SBMP_CKSUM_CRC32: return 4;
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case SBMP_CKSUM_XOR: return 1;
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case SBMP_CKSUM_NONE: return 0;
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default:
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return 4; // assume all unknown checksums are 4 bytes long
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}
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}
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/** Start calculating a checksum */
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void cksum_begin(SBMP_CksumType type, uint32_t *scratch)
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{
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switch (type) {
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#if SBMP_HAS_CRC32
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case SBMP_CKSUM_CRC32:
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*scratch = crc32_begin();
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break;
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#endif
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case SBMP_CKSUM_XOR:
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*scratch = 0;
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break;
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case SBMP_CKSUM_NONE: // fall-through
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default:
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;
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}
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}
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/** Update the checksum calculation with an incoming byte */
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void cksum_update(SBMP_CksumType type, uint32_t *scratch, uint8_t byte)
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{
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switch (type) {
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#if SBMP_HAS_CRC32
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case SBMP_CKSUM_CRC32:
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*scratch = crc32_update(*scratch, byte);
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break;
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#endif
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case SBMP_CKSUM_XOR:
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*scratch ^= byte;
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break;
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case SBMP_CKSUM_NONE: // fall-through
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default:
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;
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}
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}
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/** Stop the checksum calculation, get the result */
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void cksum_end(SBMP_CksumType type, uint32_t *scratch)
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{
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switch (type) {
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#if SBMP_HAS_CRC32
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case SBMP_CKSUM_CRC32:
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*scratch = crc32_end(*scratch);
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#endif
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case SBMP_CKSUM_XOR:
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// scratch already contains the checksum
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break;
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case SBMP_CKSUM_NONE: // fall-through
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default:
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*scratch = 0;
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break;
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}
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}
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/** Check if the calculated checksum matches the received one */
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bool cksum_verify(SBMP_CksumType type, uint32_t *scratch, uint32_t received_cksum)
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{
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cksum_end(type, scratch);
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// scratch now contains the checksum
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switch (type) {
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#if SBMP_HAS_CRC32
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case SBMP_CKSUM_CRC32: // fall-through
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#endif
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case SBMP_CKSUM_XOR:
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return (*scratch == received_cksum);
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case SBMP_CKSUM_NONE: // fall-through
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default:
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// unknown checksum type
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return true; // assume it's OK
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}
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}
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