On Sun, Feb 12, 2012 at 06:29:49PM -0800, Peter C. Wallace wrote:
> 147 case 0x06: // byte stream
> 148 buff = *pin->u32_pin & ((1 << conf->DataLength) - 1);
> 149 break;
Hm, perhaps this is the correct replacement:
buff = *pin->u32_pin & (0xffffffffu >> (32 - conf->DataLength));
I wrote the following program to verify the equivalence of this and the
original-with-special-case for arguments of 1..32 inclusive:
#include <assert.h>
#include <stdint.h>
uint32_t f1(int n) {
if(n == 32) return 0xffffffffu;
return (1 << n) - 1;
}
uint32_t f2(int n) {
return 0xffffffffu >> (32 - n);
}
int main() {
int i;
for(i=1; i<32; i++) {
assert(f1(i) == f2(i));
}
return 0;
}
this moves the "shift 32 bits" case to correspond to a DataLength of 0, which
probably represents misconfiguration.
Jeff
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