diff options
Diffstat (limited to 'lib/string/memmem.c')
| -rw-r--r-- | lib/string/memmem.c | 152 |
1 files changed, 0 insertions, 152 deletions
diff --git a/lib/string/memmem.c b/lib/string/memmem.c deleted file mode 100644 index cfd23bb..0000000 --- a/lib/string/memmem.c +++ /dev/null @@ -1,152 +0,0 @@ -/* SPDX-License-Identifier: MIT */ -/* Derived from musl libc (Copyright © 2005-2020 Rich Felker, et al.) */ - -#define _GNU_SOURCE -#include <string.h> -#include <stdint.h> - -static char *twobyte_memmem(const unsigned char *h, size_t k, const unsigned char *n) -{ - uint16_t nw = n[0]<<8 | n[1], hw = h[0]<<8 | h[1]; - for (h+=2, k-=2; k; k--, hw = hw<<8 | *h++) - if (hw == nw) return (char *)h-2; - return hw == nw ? (char *)h-2 : 0; -} - -static char *threebyte_memmem(const unsigned char *h, size_t k, const unsigned char *n) -{ - uint32_t nw = (uint32_t)n[0]<<24 | n[1]<<16 | n[2]<<8; - uint32_t hw = (uint32_t)h[0]<<24 | h[1]<<16 | h[2]<<8; - for (h+=3, k-=3; k; k--, hw = (hw|*h++)<<8) - if (hw == nw) return (char *)h-3; - return hw == nw ? (char *)h-3 : 0; -} - -static char *fourbyte_memmem(const unsigned char *h, size_t k, const unsigned char *n) -{ - uint32_t nw = (uint32_t)n[0]<<24 | n[1]<<16 | n[2]<<8 | n[3]; - uint32_t hw = (uint32_t)h[0]<<24 | h[1]<<16 | h[2]<<8 | h[3]; - for (h+=4, k-=4; k; k--, hw = hw<<8 | *h++) - if (hw == nw) return (char *)h-4; - return hw == nw ? (char *)h-4 : 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_memmem(const unsigned char *h, const unsigned char *z, const unsigned char *n, size_t l) -{ - size_t i, 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 (i=0; i<l; i++) - BITOP(byteset, n[i], |=), shift[n[i]] = i+1; - - /* 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; - - /* Search loop */ - for (;;) { - /* If remainder of haystack is shorter than needle, done */ - if (z-h < l) return 0; - - /* Check last byte first; advance by shift on mismatch */ - if (BITOP(byteset, h[l-1], &)) { - k = l-shift[h[l-1]]; - if (k) { - if (k < mem) k = mem; - h += k; - mem = 0; - continue; - } - } else { - h += l; - mem = 0; - continue; - } - - /* Compare right half */ - for (k=MAX(ms+1,mem); k<l && n[k] == h[k]; k++); - if (k < l) { - 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; - } -} - -void *memmem(const void *h0, size_t k, const void *n0, size_t l) -{ - const unsigned char *h = h0, *n = n0; - - /* Return immediately on empty needle */ - if (!l) return (void *)h; - - /* Return immediately when needle is longer than haystack */ - if (k<l) return 0; - - /* Use faster algorithms for short needles */ - h = memchr(h0, *n, k); - if (!h || l==1) return (void *)h; - k -= h - (const unsigned char *)h0; - if (k<l) return 0; - if (l==2) return twobyte_memmem(h, k, n); - if (l==3) return threebyte_memmem(h, k, n); - if (l==4) return fourbyte_memmem(h, k, n); - - return twoway_memmem(h, h+k, n, l); -} |
