[337] | 1 | #include <wchar.h>
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| 2 |
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| 3 | #define MAX(a,b) ((a)>(b)?(a):(b))
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| 4 | #define MIN(a,b) ((a)<(b)?(a):(b))
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| 5 |
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| 6 | static wchar_t *twoway_wcsstr(const wchar_t *h, const wchar_t *n)
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| 7 | {
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| 8 | const wchar_t *z;
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| 9 | size_t l, ip, jp, k, p, ms, p0, mem, mem0;
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| 10 |
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| 11 | /* Computing length of needle */
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| 12 | for (l=0; n[l] && h[l]; l++);
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| 13 | if (n[l]) return 0; /* hit the end of h */
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| 14 |
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| 15 | /* Compute maximal suffix */
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| 16 | ip = -1; jp = 0; k = p = 1;
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| 17 | while (jp+k<l) {
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| 18 | if (n[ip+k] == n[jp+k]) {
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| 19 | if (k == p) {
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| 20 | jp += p;
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| 21 | k = 1;
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| 22 | } else k++;
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| 23 | } else if (n[ip+k] > n[jp+k]) {
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| 24 | jp += k;
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| 25 | k = 1;
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| 26 | p = jp - ip;
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| 27 | } else {
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| 28 | ip = jp++;
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| 29 | k = p = 1;
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| 30 | }
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| 31 | }
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| 32 | ms = ip;
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| 33 | p0 = p;
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| 34 |
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| 35 | /* And with the opposite comparison */
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| 36 | ip = -1; jp = 0; k = p = 1;
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| 37 | while (jp+k<l) {
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| 38 | if (n[ip+k] == n[jp+k]) {
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| 39 | if (k == p) {
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| 40 | jp += p;
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| 41 | k = 1;
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| 42 | } else k++;
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| 43 | } else if (n[ip+k] < n[jp+k]) {
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| 44 | jp += k;
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| 45 | k = 1;
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| 46 | p = jp - ip;
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| 47 | } else {
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| 48 | ip = jp++;
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| 49 | k = p = 1;
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| 50 | }
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| 51 | }
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| 52 | if (ip+1 > ms+1) ms = ip;
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| 53 | else p = p0;
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| 54 |
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| 55 | /* Periodic needle? */
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| 56 | if (wmemcmp(n, n+p, ms+1)) {
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| 57 | mem0 = 0;
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| 58 | p = MAX(ms, l-ms-1) + 1;
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| 59 | } else mem0 = l-p;
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| 60 | mem = 0;
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| 61 |
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| 62 | /* Initialize incremental end-of-haystack pointer */
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| 63 | z = h;
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| 64 |
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| 65 | /* Search loop */
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| 66 | for (;;) {
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| 67 | /* Update incremental end-of-haystack pointer */
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| 68 | if (z-h < l) {
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| 69 | /* Fast estimate for MIN(l,63) */
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| 70 | size_t grow = l | 63;
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| 71 | const wchar_t *z2 = wmemchr(z, 0, grow);
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| 72 | if (z2) {
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| 73 | z = z2;
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| 74 | if (z-h < l) return 0;
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| 75 | } else z += grow;
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| 76 | }
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| 77 |
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| 78 | /* Compare right half */
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| 79 | for (k=MAX(ms+1,mem); n[k] && n[k] == h[k]; k++);
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| 80 | if (n[k]) {
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| 81 | h += k-ms;
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| 82 | mem = 0;
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| 83 | continue;
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| 84 | }
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| 85 | /* Compare left half */
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| 86 | for (k=ms+1; k>mem && n[k-1] == h[k-1]; k--);
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| 87 | if (k <= mem) return (wchar_t *)h;
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| 88 | h += p;
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| 89 | mem = mem0;
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| 90 | }
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| 91 | }
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| 92 |
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| 93 | wchar_t *wcsstr(const wchar_t *restrict h, const wchar_t *restrict n)
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| 94 | {
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| 95 | /* Return immediately on empty needle or haystack */
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| 96 | if (!n[0]) return (wchar_t *)h;
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| 97 | if (!h[0]) return 0;
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| 98 |
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| 99 | /* Use faster algorithms for short needles */
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| 100 | h = wcschr(h, *n);
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| 101 | if (!h || !n[1]) return (wchar_t *)h;
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| 102 | if (!h[1]) return 0;
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| 103 |
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| 104 | return twoway_wcsstr(h, n);
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| 105 | }
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