Rich Felker
a59341420f
this interface is non-standardized and is a GNU invention, and as such, our implementation should match the behavior of the GNU function. one peculiarity the old implementation got wrong was the handling of all-zero digit sequences: they are supposed to compare greater than digit sequences of which they are a proper prefix, as in 009 < 00. in addition, high bytes were treated with char signedness rather than as unsigned. this was wrong regardless of what the GNU function does since the resulting order relation varied by arch. the new strverscmp implementation makes explicit the cases where the order differs from what strcmp would produce, of which there are only two.
35 lines
973 B
C
35 lines
973 B
C
#define _GNU_SOURCE
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#include <ctype.h>
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#include <string.h>
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int strverscmp(const char *l0, const char *r0)
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{
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const unsigned char *l = (const void *)l0;
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const unsigned char *r = (const void *)r0;
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size_t i, dp, j;
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int z = 1;
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/* Find maximal matching prefix and track its maximal digit
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* suffix and whether those digits are all zeros. */
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for (dp=i=0; l[i]==r[i]; i++) {
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int c = l[i];
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if (!c) return 0;
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if (!isdigit(c)) dp=i+1, z=1;
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else if (c!='0') z=0;
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}
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if (l[dp]!='0' && r[dp]!='0') {
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/* If we're not looking at a digit sequence that began
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* with a zero, longest digit string is greater. */
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for (j=i; isdigit(l[j]); j++)
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if (!isdigit(r[j])) return 1;
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if (isdigit(r[j])) return -1;
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} else if (z && dp<i && (isdigit(l[i]) || isdigit(r[i]))) {
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/* Otherwise, if common prefix of digit sequence is
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* all zeros, digits order less than non-digits. */
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return (unsigned char)(l[i]-'0') - (unsigned char)(r[i]-'0');
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}
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return l[i] - r[i];
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}
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