/* Measure strstr functions. Copyright (C) 2013-2019 Free Software Foundation, Inc. This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. The GNU C Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with the GNU C Library; if not, see . */ #define MIN_PAGE_SIZE 131072 #define TEST_MAIN #define TEST_NAME "strstr" #include "bench-string.h" static const char input[] = "This manual is written with the assumption that you are at least " "somewhat familiar with the C programming language and basic programming " "concepts. Specifically, familiarity with ISO standard C (*note ISO " "C::), rather than “traditional” pre-ISO C dialects, is assumed.\n" " The GNU C Library includes several “header files”, each of which " "provides definitions and declarations for a group of related facilities; " "this information is used by the C compiler when processing your program. " "For example, the header file ‘stdio.h’ declares facilities for " "performing input and output, and the header file ‘string.h’ declares " "string processing utilities. The organization of this manual generally " "follows the same division as the header files.\n" " If you are reading this manual for the first time, you should read " "all of the introductory material and skim the remaining chapters. There " "are a _lot_ of functions in the GNU C Library and it’s not realistic to " "expect that you will be able to remember exactly _how_ to use each and " "every one of them. It’s more important to become generally familiar " "with the kinds of facilities that the library provides, so that when you " "are writing your programs you can recognize _when_ to make use of " "library functions, and _where_ in this manual you can find more specific " "information about them.\n"; /* Simple yet efficient strstr - for needles < 32 bytes it is 2-4 times faster than the optimized twoway_strstr. */ static char * basic_strstr (const char *s1, const char *s2) { size_t i; int c = s2[0]; if (c == 0) return (char*)s1; for ( ; s1[0] != '\0'; s1++) { if (s1[0] != c) continue; for (i = 1; s2[i] != 0; i++) if (s1[i] != s2[i]) break; if (s2[i] == '\0') return (char*)s1; } return NULL; } #define RETURN_TYPE char * #define AVAILABLE(h, h_l, j, n_l) \ (((j) + (n_l) <= (h_l)) \ || ((h_l) += __strnlen ((void*)((h) + (h_l)), (n_l) + 512), \ (j) + (n_l) <= (h_l))) #define CHECK_EOL (1) #define RET0_IF_0(a) if (!a) goto ret0 #define FASTSEARCH(S,C,N) (void*) strchr ((void*)(S), (C)) #define LONG_NEEDLE_THRESHOLD 32U #define __strnlen strnlen #include "string/str-two-way.h" /* Optimized Two-way implementation from GLIBC 2.29. */ static char * twoway_strstr (const char *haystack, const char *needle) { size_t needle_len; /* Length of NEEDLE. */ size_t haystack_len; /* Known minimum length of HAYSTACK. */ /* Handle empty NEEDLE special case. */ if (needle[0] == '\0') return (char *) haystack; /* Skip until we find the first matching char from NEEDLE. */ haystack = strchr (haystack, needle[0]); if (haystack == NULL || needle[1] == '\0') return (char *) haystack; /* Ensure HAYSTACK length is at least as long as NEEDLE length. Since a match may occur early on in a huge HAYSTACK, use strnlen and read ahead a few cachelines for improved performance. */ needle_len = strlen (needle); haystack_len = __strnlen (haystack, needle_len + 256); if (haystack_len < needle_len) return NULL; /* Check whether we have a match. This improves performance since we avoid the initialization overhead of the two-way algorithm. */ if (memcmp (haystack, needle, needle_len) == 0) return (char *) haystack; /* Perform the search. Abstract memory is considered to be an array of 'unsigned char' values, not an array of 'char' values. See ISO C 99 section 6.2.6.1. */ if (needle_len < LONG_NEEDLE_THRESHOLD) return two_way_short_needle ((const unsigned char *) haystack, haystack_len, (const unsigned char *) needle, needle_len); return two_way_long_needle ((const unsigned char *) haystack, haystack_len, (const unsigned char *) needle, needle_len); } typedef char *(*proto_t) (const char *, const char *); IMPL (strstr, 1) IMPL (twoway_strstr, 0) IMPL (basic_strstr, 0) static void do_one_test (impl_t *impl, const char *s1, const char *s2, char *exp_result) { size_t i, iters = INNER_LOOP_ITERS_SMALL; timing_t start, stop, cur; char *res; TIMING_NOW (start); for (i = 0; i < iters; ++i) res = CALL (impl, s1, s2); TIMING_NOW (stop); TIMING_DIFF (cur, start, stop); TIMING_PRINT_MEAN ((double) cur, (double) iters); if (res != exp_result) { error (0, 0, "Wrong result in function %s %s %s", impl->name, res, exp_result); ret = 1; } } static void do_test (size_t align1, size_t align2, size_t len1, size_t len2, int fail) { char *s1 = (char *) (buf1 + align1); char *s2 = (char *) (buf2 + align2); size_t size = sizeof (input) - 1; size_t pos = (len1 + len2) % size; char *ss2 = s2; for (size_t l = len2; l > 0; l = l > size ? l - size : 0) { size_t t = l > size ? size : l; if (pos + t <= size) ss2 = mempcpy (ss2, input + pos, t); else { ss2 = mempcpy (ss2, input + pos, size - pos); ss2 = mempcpy (ss2, input, t - (size - pos)); } } s2[len2] = '\0'; char *ss1 = s1; for (size_t l = len1; l > 0; l = l > size ? l - size : 0) { size_t t = l > size ? size : l; memcpy (ss1, input, t); ss1 += t; } if (!fail) memcpy (s1 + len1 - len2, s2, len2); s1[len1] = '\0'; /* Remove any accidental matches except for the last if !fail. */ for (ss1 = basic_strstr (s1, s2); ss1; ss1 = basic_strstr (ss1 + 1, s2)) if (fail || ss1 != s1 + len1 - len2) ++ss1[len2 / 2]; printf ("Length %4zd/%3zd, alignment %2zd/%2zd, %s:", len1, len2, align1, align2, fail ? "fail " : "found"); FOR_EACH_IMPL (impl, 0) do_one_test (impl, s1, s2, fail ? NULL : s1 + len1 - len2); putchar ('\n'); } /* Test needles which exhibit worst-case performance. This shows that basic_strstr is quadratic and thus unsuitable for large needles. On the other hand Two-way and skip table implementations are linear with increasing needle sizes. The slowest cases of the two implementations are within a factor of 2 on several different microarchitectures. */ static void test_hard_needle (size_t ne_len, size_t hs_len) { char *ne = (char *) buf1; char *hs = (char *) buf2; /* Hard needle for strstr algorithm using skip table. This results in many memcmp calls comparing most of the needle. */ { memset (ne, 'a', ne_len); ne[ne_len] = '\0'; ne[ne_len - 14] = 'b'; memset (hs, 'a', hs_len); for (size_t i = ne_len; i <= hs_len; i += ne_len) { hs[i-5] = 'b'; hs[i-62] = 'b'; } printf ("Length %4zd/%3zd, complex needle 1:", hs_len, ne_len); FOR_EACH_IMPL (impl, 0) do_one_test (impl, hs, ne, NULL); putchar ('\n'); } /* 2nd hard needle for strstr algorithm using skip table. This results in many memcmp calls comparing most of the needle. */ { memset (ne, 'a', ne_len); ne[ne_len] = '\0'; ne[ne_len - 6] = 'b'; memset (hs, 'a', hs_len); for (size_t i = ne_len; i <= hs_len; i += ne_len) { hs[i-5] = 'b'; hs[i-6] = 'b'; } printf ("Length %4zd/%3zd, complex needle 2:", hs_len, ne_len); FOR_EACH_IMPL (impl, 0) do_one_test (impl, hs, ne, NULL); putchar ('\n'); } /* Hard needle for Two-way algorithm - the random input causes a large number of branch mispredictions which significantly reduces performance on modern micro architectures. */ { for (int i = 0; i < hs_len; i++) hs[i] = (rand () & 255) > 155 ? 'a' : 'b'; hs[hs_len] = 0; memset (ne, 'a', ne_len); ne[ne_len-2] = 'b'; ne[0] = 'b'; ne[ne_len] = 0; printf ("Length %4zd/%3zd, complex needle 3:", hs_len, ne_len); FOR_EACH_IMPL (impl, 0) do_one_test (impl, hs, ne, NULL); putchar ('\n'); } } static int test_main (void) { test_init (); printf ("%23s", ""); FOR_EACH_IMPL (impl, 0) printf ("\t%s", impl->name); putchar ('\n'); for (size_t hlen = 64; hlen <= 256; hlen += 32) for (size_t klen = 1; klen <= 16; klen++) { do_test (1, 3, hlen, klen, 0); do_test (0, 9, hlen, klen, 1); } for (size_t hlen = 256; hlen <= 65536; hlen *= 2) for (size_t klen = 16; klen <= 256; klen *= 2) { do_test (1, 11, hlen, klen, 0); do_test (14, 5, hlen, klen, 1); } test_hard_needle (64, 65536); test_hard_needle (256, 65536); test_hard_needle (1024, 65536); return ret; } #include