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44 lines
1.6 KiB
C
44 lines
1.6 KiB
C
#include "scan.h"
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size_t scan_8longn(const char *src,size_t n,unsigned long *dest) {
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/* make a copy of src so we can return the number of bytes we progressed */
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register const char *tmp=src;
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register unsigned long l=0;
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register unsigned char c;
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/* *tmp - '0' can be negative, but casting to unsigned char makes
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* those cases positive and large; that means we only need one
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* comparison. This trick is no longer needed on modern compilers,
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* but we also want to produce good code on old compilers :) */
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while (n-->0 && (c=(unsigned char)(*tmp-'0'))<8) {
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/* overflow check; for each digit we multiply by 8 and then add the
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* digit; 0-7 needs 3 bits of storage, so we need to check if the
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* uppermost 3 bits of l are empty. Do it by shifting to the right */
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if (l>>(sizeof(l)*8-3)) break;
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l=l*8+c;
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++tmp;
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}
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*dest=l;
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return (size_t)(tmp-src);
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}
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#ifdef UNITTEST
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#include <assert.h>
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int main() {
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unsigned long i;
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assert(scan_8longn("1234\0""67890",10,&i)==4 && i==01234);
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assert(scan_8longn("12345678",9,&i)==7 && i==01234567);
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if (sizeof(long)==sizeof(int)) {
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assert(scan_8longn("37777777777",12,&i)==11 && i==0xffffffff);
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assert(scan_8longn("40000000000",12,&i)==10 && i==04000000000);
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} else if (sizeof(long)==sizeof(long long)) {
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assert(scan_8longn("1777777777777777777777",23,&i)==22 && i==0xffffffffffffffffull);
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assert(scan_8longn("2000000000000000000000",23,&i)==21 && i==0200000000000000000000ull);
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}
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assert(scan_8longn("-4",3,&i)==0 && i==0);
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assert(scan_8longn("01234",6,&i)==5 && i==01234);
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assert(scan_8longn("1234",2,&i)==2 && i==012);
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return 0;
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}
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#endif
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