You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
87 lines
2.7 KiB
C
87 lines
2.7 KiB
C
#include "scan.h"
|
|
#ifndef INTERNAL
|
|
#include "haveuint128.h"
|
|
#endif
|
|
|
|
size_t scan_ulongn(const char* src,size_t n,unsigned long int* dest) {
|
|
register const char *tmp=src;
|
|
register unsigned long int l=0;
|
|
register unsigned char c;
|
|
/* Since the conditions can be computed at compile time, the compiler
|
|
* should only emit code for one of the implementations, depending on
|
|
* which architecture the code is compiled for. */
|
|
#if defined(__GNUC__) && (__GNUC__ >= 5)
|
|
/* implementation for recent gcc or clang */
|
|
int ok=0;
|
|
for (; n-->0 && (c=(unsigned char)(*tmp-'0'))<10; ++tmp) {
|
|
unsigned long v;
|
|
if (__builtin_mul_overflow(l,10,&v) || __builtin_add_overflow(v,c,&v))
|
|
break;
|
|
l=v;
|
|
ok=1;
|
|
}
|
|
if (!ok) return 0;
|
|
|
|
*dest=l;
|
|
return (size_t)(tmp-src);
|
|
#else
|
|
#ifdef HAVE_UINT128
|
|
if (sizeof(unsigned long)==sizeof(unsigned long long) && sizeof(unsigned long)<sizeof(__uint128_t)) {
|
|
/* implementation for 64-bit platforms with gcc */
|
|
for (; n-->0 && (c=(unsigned char)(*tmp-'0'))<10; ++tmp) {
|
|
__uint128_t L=(__uint128_t)l*10+c;
|
|
if ((L >> ((sizeof(L)-sizeof(l))*8))) break;
|
|
l=(unsigned long)L;
|
|
}
|
|
*dest=l;
|
|
return (size_t)(tmp-src);
|
|
} else
|
|
#endif
|
|
if (sizeof(unsigned long)<sizeof(unsigned long long)) {
|
|
/* implementation for 32-bit platforms */
|
|
for (; n-->0 && (c=(unsigned char)(*tmp-'0'))<10; ++tmp) {
|
|
unsigned long long L=(unsigned long long)l*10+c;
|
|
if ((unsigned long)L != L) break;
|
|
l=(unsigned long)L;
|
|
}
|
|
*dest=l;
|
|
return (size_t)(tmp-src);
|
|
} else {
|
|
/* implementation for 64-bit platforms without gcc */
|
|
while (n-->0 && (c=(unsigned char)(*tmp-'0'))<10) {
|
|
unsigned long int n;
|
|
/* we want to do: l=l*10+c
|
|
* but we need to check for integer overflow.
|
|
* to check whether l*10 overflows, we could do
|
|
* if ((l*10)/10 != l)
|
|
* however, multiplication and division are expensive.
|
|
* so instead of *10 we do (l<<3) (i.e. *8) + (l<<1) (i.e. *2)
|
|
* and check for overflow on all the intermediate steps */
|
|
n=l<<3; if ((n>>3)!=l) break;
|
|
if (n+(l<<1)+c < n) break;
|
|
l=n+(l<<1)+c;
|
|
++tmp;
|
|
}
|
|
if (tmp-src) *dest=l;
|
|
return (size_t)(tmp-src);
|
|
}
|
|
#endif
|
|
}
|
|
|
|
#ifdef UNITTEST
|
|
#include <assert.h>
|
|
|
|
int main() {
|
|
unsigned long l;
|
|
assert(scan_ulongn("4294967295",10,&l) == 10 && l==4294967295ul);
|
|
if (sizeof(unsigned long)==4) {
|
|
assert(scan_ulongn("4294967296",10,&l) == 9 && l==429496729);
|
|
} else {
|
|
assert(scan_ulongn("18446744073709551615",20,&l) == 20 && l==18446744073709551615ull);
|
|
assert(scan_ulongn("18446744073709551616",20,&l) == 19 && l==1844674407370955161ull);
|
|
}
|
|
assert(scan_ulongn("1234",3,&l)==3 && l==123);
|
|
return 0;
|
|
}
|
|
#endif
|