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https://github.com/fluencelabs/musl
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476cd1d965
in cases where the memorized match range from the right factor exceeded the length of the left factor, it was wrongly treated as a mismatch rather than a match. issue reported by Yves Bastide.
106 lines
2.0 KiB
C
106 lines
2.0 KiB
C
#include <wchar.h>
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#define MAX(a,b) ((a)>(b)?(a):(b))
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#define MIN(a,b) ((a)<(b)?(a):(b))
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static wchar_t *twoway_wcsstr(const wchar_t *h, const wchar_t *n)
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{
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const wchar_t *z;
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size_t l, ip, jp, k, p, ms, p0, mem, mem0;
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/* Computing length of needle */
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for (l=0; n[l] && h[l]; l++);
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if (n[l]) return 0; /* hit the end of h */
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/* Compute maximal suffix */
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ip = -1; jp = 0; k = p = 1;
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while (jp+k<l) {
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if (n[ip+k] == n[jp+k]) {
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if (k == p) {
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jp += p;
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k = 1;
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} else k++;
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} else if (n[ip+k] > n[jp+k]) {
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jp += k;
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k = 1;
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p = jp - ip;
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} else {
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ip = jp++;
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k = p = 1;
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}
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}
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ms = ip;
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p0 = p;
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/* And with the opposite comparison */
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ip = -1; jp = 0; k = p = 1;
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while (jp+k<l) {
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if (n[ip+k] == n[jp+k]) {
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if (k == p) {
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jp += p;
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k = 1;
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} else k++;
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} else if (n[ip+k] < n[jp+k]) {
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jp += k;
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k = 1;
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p = jp - ip;
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} else {
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ip = jp++;
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k = p = 1;
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}
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}
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if (ip+1 > ms+1) ms = ip;
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else p = p0;
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/* Periodic needle? */
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if (wmemcmp(n, n+p, ms+1)) {
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mem0 = 0;
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p = MAX(ms, l-ms-1) + 1;
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} else mem0 = l-p;
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mem = 0;
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/* Initialize incremental end-of-haystack pointer */
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z = h;
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/* Search loop */
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for (;;) {
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/* Update incremental end-of-haystack pointer */
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if (z-h < l) {
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/* Fast estimate for MIN(l,63) */
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size_t grow = l | 63;
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const wchar_t *z2 = wmemchr(z, 0, grow);
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if (z2) {
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z = z2;
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if (z-h < l) return 0;
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} else z += grow;
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}
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/* Compare right half */
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for (k=MAX(ms+1,mem); n[k] && n[k] == h[k]; k++);
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if (n[k]) {
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h += k-ms;
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mem = 0;
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continue;
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}
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/* Compare left half */
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for (k=ms+1; k>mem && n[k-1] == h[k-1]; k--);
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if (k <= mem) return (wchar_t *)h;
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h += p;
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mem = mem0;
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}
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}
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wchar_t *wcsstr(const wchar_t *restrict h, const wchar_t *restrict n)
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{
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/* Return immediately on empty needle or haystack */
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if (!n[0]) return (wchar_t *)h;
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if (!h[0]) return 0;
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/* Use faster algorithms for short needles */
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h = wcschr(h, *n);
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if (!h || !n[1]) return (wchar_t *)h;
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if (!h[1]) return 0;
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return twoway_wcsstr(h, n);
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}
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