mirror of
https://github.com/cc65/cc65.git
synced 2024-11-05 08:05:51 +00:00
57 lines
1.3 KiB
C
57 lines
1.3 KiB
C
/*
|
|
!!DESCRIPTION!!
|
|
!!ORIGIN!! testsuite
|
|
!!LICENCE!! Public Domain
|
|
!!AUTHOR!! Marc 'BlackJack' Rintsch
|
|
*/
|
|
|
|
/*
|
|
Compiler is build from cc65-snapshot-2.13.9.20101031 sources.
|
|
|
|
Expected results and also what I get from this without any optimisations
|
|
are: 48663 and 49218
|
|
|
|
When I turn on ''-O'': 58096 and 58096. After swapping the two variable
|
|
declaration lines in 'calculate_checksum()' the results are correct
|
|
with ''-O''.
|
|
|
|
But with ''--O --static-locals'' the results are incorrect again (31757
|
|
and 15408). ''--static-locals'' alone works though.
|
|
*/
|
|
|
|
#include <stdio.h>
|
|
#include <stdint.h>
|
|
|
|
// uint16_t __fastcall__ calculate_checksum(uint8_t *block);
|
|
uint8_t block[256];
|
|
|
|
uint16_t calculate_checksum(uint8_t *block)
|
|
{
|
|
uint16_t i, result = 0xffff;
|
|
uint8_t j;
|
|
|
|
for (i = 0; i < 256; ++i) {
|
|
result ^= block[i] << 8;
|
|
for (j = 0; j < 8; ++j) {
|
|
if (result & (1 << 15)) {
|
|
result = (result << 1) ^ 0x1021;
|
|
} else {
|
|
result <<= 1;
|
|
}
|
|
}
|
|
}
|
|
return ~result;
|
|
}
|
|
|
|
int main(void)
|
|
{
|
|
uint16_t i;
|
|
|
|
printf("zeroes: %u\n", calculate_checksum(block));
|
|
for (i = 0; i < 256; ++i) block[i] = i;
|
|
printf("0..255: %u\n", calculate_checksum(block));
|
|
|
|
return 0;
|
|
}
|
|
|