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66 lines
1.7 KiB
C
66 lines
1.7 KiB
C
#include "my_base.h"
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/*
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my_memmem, port of a GNU extension.
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Returns a pointer to the beginning of the substring, needle, or NULL if the
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substring is not found in haystack.
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*/
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void *my_memmem(const void *haystack, size_t haystacklen,
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const void *needle, size_t needlelen)
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{
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const unsigned char *cursor;
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const unsigned char *last_possible_needle_location =
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(unsigned char *)haystack + haystacklen - needlelen;
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/* Easy answers */
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if (needlelen > haystacklen) return(NULL);
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if (needle == NULL) return(NULL);
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if (haystack == NULL) return(NULL);
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if (needlelen == 0) return(NULL);
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if (haystacklen == 0) return(NULL);
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for (cursor = haystack; cursor <= last_possible_needle_location; cursor++) {
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if (memcmp(needle, cursor, needlelen) == 0) {
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return((void *) cursor);
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}
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}
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return(NULL);
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}
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#ifdef MAIN
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#include <assert.h>
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int main(int argc, char *argv[]) {
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char haystack[10], needle[3];
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memmove(haystack, "0123456789", 10);
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memmove(needle, "no", 2);
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assert(my_memmem(haystack, 10, needle, 2) == NULL);
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memmove(needle, "345", 3);
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assert(my_memmem(haystack, 10, needle, 3) != NULL);
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memmove(needle, "789", 3);
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assert(my_memmem(haystack, 10, needle, 3) != NULL);
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assert(my_memmem(haystack, 9, needle, 3) == NULL);
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memmove(needle, "012", 3);
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assert(my_memmem(haystack, 10, needle, 3) != NULL);
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assert(my_memmem(NULL, 10, needle, 3) == NULL);
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assert(my_memmem(NULL, 10, needle, 3) == NULL);
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assert(my_memmem(haystack, 0, needle, 3) == NULL);
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assert(my_memmem(haystack, 10, NULL, 3) == NULL);
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assert(my_memmem(haystack, 10, needle, 0) == NULL);
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assert(my_memmem(haystack, 1, needle, 3) == NULL);
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printf("success\n");
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return(0);
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}
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#endif
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