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39 lines
1.3 KiB
C
39 lines
1.3 KiB
C
#include "byte.h"
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/* str_diff returns negative, 0, or positive, depending on whether the
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* string a[0], a[1], ..., a[n]=='\0' is lexicographically smaller than,
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* equal to, or greater than the string b[0], b[1], ..., b[m-1]=='\0'.
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* When the strings are different, str_diff does not read bytes past the
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* first difference. */
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int str_diffn(const char* a, const char* b, size_t limit) {
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register const unsigned char* s=(const unsigned char*)a;
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register const unsigned char* t=(const unsigned char*)b;
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register const unsigned char* u=t+limit;
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register int j;
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j=0;
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for (;;) {
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if (t>=u || (j=(*s-*t)) || !*t) break;
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++s; ++t;
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if (t>=u || (j=(*s-*t)) || !*t) break;
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++s; ++t;
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if (t>=u || (j=(*s-*t)) || !*t) break;
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++s; ++t;
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if (t>=u || (j=(*s-*t)) || !*t) break;
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++s; ++t;
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}
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return j;
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}
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#ifdef UNITTEST
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#include <assert.h>
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#include <string.h>
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int main() {
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assert(str_diffn("foo","foo",3)==0);
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assert(str_diffn("foo","fob",3)==('o'-'b'));
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assert(str_diffn("foo","foox",4)==(-'x'));
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assert(str_diffn("foox","foo",4)=='x');
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assert(str_diffn("foo","fob",2)==0);
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}
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#endif
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