Add a "fork" of musl as //fusl.

fusl/src/string/strstr.c

+#include <string.h>
+#include <stdint.h>
+
+static char *twobyte_strstr(const unsigned char *h, const unsigned char *n)
+{
+        uint16_t nw = n[0]<<8 | n[1], hw = h[0]<<8 | h[1];
+        for (h++; *h && hw != nw; hw = hw<<8 | *++h);
+        return *h ? (char *)h-1 : 0;
+}
+
+static char *threebyte_strstr(const unsigned char *h, const unsigned char *n)
+{
+        uint32_t nw = n[0]<<24 | n[1]<<16 | n[2]<<8;
+        uint32_t hw = h[0]<<24 | h[1]<<16 | h[2]<<8;
+        for (h+=2; *h && hw != nw; hw = (hw|*++h)<<8);
+        return *h ? (char *)h-2 : 0;
+}
+
+static char *fourbyte_strstr(const unsigned char *h, const unsigned char *n)
+{
+        uint32_t nw = n[0]<<24 | n[1]<<16 | n[2]<<8 | n[3];
+        uint32_t hw = h[0]<<24 | h[1]<<16 | h[2]<<8 | h[3];
+        for (h+=3; *h && hw != nw; hw = hw<<8 | *++h);
+        return *h ? (char *)h-3 : 0;
+}
+
+#define MAX(a,b) ((a)>(b)?(a):(b))
+#define MIN(a,b) ((a)<(b)?(a):(b))
+
+#define BITOP(a,b,op) \
+ ((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a))))
+
+static char *twoway_strstr(const unsigned char *h, const unsigned char *n)
+{
+        const unsigned char *z;
+        size_t l, ip, jp, k, p, ms, p0, mem, mem0;
+        size_t byteset[32 / sizeof(size_t)] = { 0 };
+        size_t shift[256];
+
+        /* Computing length of needle and fill shift table */
+        for (l=0; n[l] && h[l]; l++)
+                BITOP(byteset, n[l], |=), shift[n[l]] = l+1;
+        if (n[l]) return 0; /* hit the end of h */
+
+        /* Compute maximal suffix */
+        ip = -1; jp = 0; k = p = 1;
+        while (jp+k<l) {
+                if (n[ip+k] == n[jp+k]) {
+                        if (k == p) {
+                                jp += p;
+                                k = 1;
+                        } else k++;
+                } else if (n[ip+k] > n[jp+k]) {
+                        jp += k;
+                        k = 1;
+                        p = jp - ip;
+                } else {
+                        ip = jp++;
+                        k = p = 1;
+                }
+        }
+        ms = ip;
+        p0 = p;
+
+        /* And with the opposite comparison */
+        ip = -1; jp = 0; k = p = 1;
+        while (jp+k<l) {
+                if (n[ip+k] == n[jp+k]) {
+                        if (k == p) {
+                                jp += p;
+                                k = 1;
+                        } else k++;
+                } else if (n[ip+k] < n[jp+k]) {
+                        jp += k;
+                        k = 1;
+                        p = jp - ip;
+                } else {
+                        ip = jp++;
+                        k = p = 1;
+                }
+        }
+        if (ip+1 > ms+1) ms = ip;
+        else p = p0;
+
+        /* Periodic needle? */
+        if (memcmp(n, n+p, ms+1)) {
+                mem0 = 0;
+                p = MAX(ms, l-ms-1) + 1;
+        } else mem0 = l-p;
+        mem = 0;
+
+        /* Initialize incremental end-of-haystack pointer */
+        z = h;
+
+        /* Search loop */
+        for (;;) {
+                /* Update incremental end-of-haystack pointer */
+                if (z-h < l) {
+                        /* Fast estimate for MIN(l,63) */
+                        size_t grow = l | 63;
+                        const unsigned char *z2 = memchr(z, 0, grow);
+                        if (z2) {
+                                z = z2;
+                                if (z-h < l) return 0;
+                        } else z += grow;
+                }
+
+                /* Check last byte first; advance by shift on mismatch */
+                if (BITOP(byteset, h[l-1], &)) {
+                        k = l-shift[h[l-1]];
+                        //printf("adv by %zu (on %c) at [%s] (%zu;l=%zu)\n", k, h[l-1], h, shift[h[l-1]], l);
+                        if (k) {
+                                if (mem0 && mem && k < p) k = l-p;
+                                h += k;
+                                mem = 0;
+                                continue;
+                        }
+                } else {
+                        h += l;
+                        mem = 0;
+                        continue;
+                }
+
+                /* Compare right half */
+                for (k=MAX(ms+1,mem); n[k] && n[k] == h[k]; k++);
+                if (n[k]) {
+                        h += k-ms;
+                        mem = 0;
+                        continue;
+                }
+                /* Compare left half */
+                for (k=ms+1; k>mem && n[k-1] == h[k-1]; k--);
+                if (k <= mem) return (char *)h;
+                h += p;
+                mem = mem0;
+        }
+}
+
+char *strstr(const char *h, const char *n)
+{
+        /* Return immediately on empty needle */
+        if (!n[0]) return (char *)h;
+
+        /* Use faster algorithms for short needles */
+        h = strchr(h, *n);
+        if (!h || !n[1]) return (char *)h;
+        if (!h[1]) return 0;
+        if (!n[2]) return twobyte_strstr((void *)h, (void *)n);
+        if (!h[2]) return 0;
+        if (!n[3]) return threebyte_strstr((void *)h, (void *)n);
+        if (!h[3]) return 0;
+        if (!n[4]) return fourbyte_strstr((void *)h, (void *)n);
+
+        return twoway_strstr((void *)h, (void *)n);
+}