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#include "scan.h"
size_t scan_8int(const char* src,unsigned int* dest) {
/* make a copy of src so we can return the number of bytes we progressed */
register const char *tmp=src;
register unsigned int l=0;
register unsigned char c;
/* *tmp - '0' can be negative, but casting to unsigned char makes
* those cases positive and large; that means we only need one
* comparison. This trick is no longer needed on modern compilers,
* but we also want to produce good code on old compilers :) */
while ((c=(unsigned char)(*tmp-'0'))<8) {
/* overflow check; for each digit we multiply by 8 and then add the
* digit; 0-7 needs 3 bits of storage, so we need to check if the
* uppermost 3 bits of l are empty. Do it by shifting to the right */
if (l>>(sizeof(l)*8-3)) break;
l=l*8+c;
++tmp;
}
*dest=l;
return (size_t)(tmp-src);
}
#ifdef UNITTEST
#include <assert.h>
int main() {
unsigned int i;
assert(scan_8int("1234",&i)==4 && i==01234);
assert(scan_8int("12345678",&i)==7 && i==01234567);
assert(scan_8int("37777777777",&i)==11 && i==0xffffffff);
assert(scan_8int("40000000000",&i)==10 && i==04000000000);
assert(scan_8int("-4",&i)==0 && i==0);
assert(scan_8int("01234",&i)==5 && i==01234);
return 0;
}
#endif