compare relative performance of tolower_ctype, tolower_openbsd, tolower_oraz functions

main.c

// compare relative performance of tolower_ctype, tolower_openbsd, tolower_oraz functions
// result: 30.80, 30.51, 38.09
// $ gcc -std=c99 -O3 -g -Wall -pedantic test_tolower.c -o test_tolower;
// $ valgrind --tool=callgrind ./test_tolower 1000000
#include <assert.h>
#include <ctype.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h> 
#include <string.h>

static const char chars[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33,
 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52,
 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71,
 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90,
 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107,
 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 
 123, 124, 125, 126, 127, '\0'
};

static const int nchars = sizeof(chars) / sizeof(*chars);

typedef char* (*fun_t)(char*);

static intptr_t test(int N, fun_t tolower_) {
  char *str = malloc(nchars+1);
  if (!str) {
    perror("malloc");
    exit(1);
  }
  str = strncpy(str, chars, nchars);
  str[nchars] = '\0';

  for (int i = 0; i < N; ++i)
    tolower_(str);

  free(str);
  return (intptr_t)str;
}

static char* tolower_oraz(char* str) {
  char *p = str; 
  for ( ; *p; ++p) *p = *p >= 'A' && *p <= 'Z' ? *p|0x60 : *p;
  return p;
}

static char* tolower_ctype(char* str) {
  char *p = str;
  for ( ; *p; ++p) *p = tolower(*p);
  return p;
}

static const short _C_tolower_[] = {
  EOF,
        0x00,   0x01,   0x02,   0x03,   0x04,   0x05,   0x06,   0x07,
        0x08,   0x09,   0x0a,   0x0b,   0x0c,   0x0d,   0x0e,   0x0f,
        0x10,   0x11,   0x12,   0x13,   0x14,   0x15,   0x16,   0x17,
        0x18,   0x19,   0x1a,   0x1b,   0x1c,   0x1d,   0x1e,   0x1f,
        0x20,   0x21,   0x22,   0x23,   0x24,   0x25,   0x26,   0x27,
        0x28,   0x29,   0x2a,   0x2b,   0x2c,   0x2d,   0x2e,   0x2f,
        0x30,   0x31,   0x32,   0x33,   0x34,   0x35,   0x36,   0x37,
        0x38,   0x39,   0x3a,   0x3b,   0x3c,   0x3d,   0x3e,   0x3f,
        0x40,   'a',    'b',    'c',    'd',    'e',    'f',    'g',
        'h',    'i',    'j',    'k',    'l',    'm',    'n',    'o',
        'p',    'q',    'r',    's',    't',    'u',    'v',    'w',
        'x',    'y',    'z',    0x5b,   0x5c,   0x5d,   0x5e,   0x5f,
        0x60,   0x61,   0x62,   0x63,   0x64,   0x65,   0x66,   0x67,
        0x68,   0x69,   0x6a,   0x6b,   0x6c,   0x6d,   0x6e,   0x6f,
        0x70,   0x71,   0x72,   0x73,   0x74,   0x75,   0x76,   0x77,
        0x78,   0x79,   0x7a,   0x7b,   0x7c,   0x7d,   0x7e,   0x7f,
        0x80,   0x81,   0x82,   0x83,   0x84,   0x85,   0x86,   0x87,
        0x88,   0x89,   0x8a,   0x8b,   0x8c,   0x8d,   0x8e,   0x8f,
        0x90,   0x91,   0x92,   0x93,   0x94,   0x95,   0x96,   0x97,
        0x98,   0x99,   0x9a,   0x9b,   0x9c,   0x9d,   0x9e,   0x9f,
        0xa0,   0xa1,   0xa2,   0xa3,   0xa4,   0xa5,   0xa6,   0xa7,
        0xa8,   0xa9,   0xaa,   0xab,   0xac,   0xad,   0xae,   0xaf,
        0xb0,   0xb1,   0xb2,   0xb3,   0xb4,   0xb5,   0xb6,   0xb7,
        0xb8,   0xb9,   0xba,   0xbb,   0xbc,   0xbd,   0xbe,   0xbf,
        0xc0,   0xc1,   0xc2,   0xc3,   0xc4,   0xc5,   0xc6,   0xc7,
        0xc8,   0xc9,   0xca,   0xcb,   0xcc,   0xcd,   0xce,   0xcf,
        0xd0,   0xd1,   0xd2,   0xd3,   0xd4,   0xd5,   0xd6,   0xd7,
        0xd8,   0xd9,   0xda,   0xdb,   0xdc,   0xdd,   0xde,   0xdf,
        0xe0,   0xe1,   0xe2,   0xe3,   0xe4,   0xe5,   0xe6,   0xe7,
        0xe8,   0xe9,   0xea,   0xeb,   0xec,   0xed,   0xee,   0xef,
        0xf0,   0xf1,   0xf2,   0xf3,   0xf4,   0xf5,   0xf6,   0xf7,
        0xf8,   0xf9,   0xfa,   0xfb,   0xfc,   0xfd,   0xfe,   0xff
};

static const short *tbl_C_tolower_ = _C_tolower_;

static int _tolower_openbsd(int c) {
  // assert(c >= -1);
  return c > 255 ? c : (tbl_C_tolower_+1)[c];
}

static char* tolower_openbsd(char* str) {
  char *p = str;
  for ( ; *p; ++p) *p = _tolower_openbsd(*p);
  return p;
}

int main(int argc, char *argv[]) {
  const int N = argc <= 1 ? 1000000 : atoi(argv[1]);
  fun_t funcs[] = { tolower_ctype, tolower_oraz, tolower_openbsd };
  const int nfuncs = sizeof(funcs) / sizeof(*funcs);
  for (fun_t *pf = funcs; pf != &funcs[nfuncs]; ++pf)
    printf("%" PRIxPTR "\n", test(N, *pf));
  return 0;
}