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Naive C-implementation of wc
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#include <errno.h> | |
#include <fcntl.h> | |
#include <stddef.h> | |
#include <stdint.h> | |
#include <stdio.h> | |
#include <stdlib.h> | |
#include <string.h> | |
#include <sys/mman.h> | |
#include <time.h> | |
#include <unistd.h> | |
static struct { size_t chars, words, lines; } result; | |
static _Bool process_chunk(const unsigned char *text, const size_t bytes, | |
_Bool prev) { | |
result.chars += bytes; | |
for (size_t i = 0; i < bytes; ++i) { | |
result.lines += text[i] == '\n'; | |
_Bool now = text[i] != ' ' && text[i] - 9 > 4; | |
result.words += now & !prev; | |
prev = now; | |
} | |
return prev; | |
} | |
static int process_fd(int fd) { | |
off_t length = lseek(fd, 0, SEEK_END); | |
if (length >= 0 && length <= INTPTR_MAX) { | |
void *ptr = mmap(NULL, (size_t)length, PROT_READ, MAP_PRIVATE, fd, 0); | |
if (ptr == MAP_FAILED) { | |
perror("mmap"); | |
return EXIT_FAILURE; | |
} | |
process_chunk((const unsigned char *)ptr, (size_t)length, 0); | |
munmap(ptr, length); | |
return EXIT_SUCCESS; | |
} | |
if (length < 0 && errno != ESPIPE) { | |
perror("leeek"); | |
return EXIT_FAILURE; | |
} | |
_Bool state = 0; | |
ssize_t chunk; | |
for (;;) { | |
unsigned char buf[65536]; | |
chunk = read(fd, buf, sizeof(buf)); | |
if (chunk < 1) | |
break; | |
state = process_chunk(buf, chunk, state); | |
} | |
if (chunk < 0) { | |
perror("read"); | |
return EXIT_FAILURE; | |
} | |
return EXIT_SUCCESS; | |
} | |
int main(int argc, const char *argv[]) { | |
int rc = 42; | |
if (argc > 1) { | |
for (int i = 1; i < argc; ++i) { | |
int fd = | |
(strcmp(argv[i], "-") == 0) ? STDIN_FILENO : open(argv[1], O_RDONLY); | |
if (fd < 0) { | |
perror("open"); | |
return EXIT_FAILURE; | |
} | |
rc = process_fd(fd); | |
close(fd); | |
if (rc != EXIT_SUCCESS) | |
break; | |
} | |
} else | |
rc = process_fd(STDIN_FILENO); | |
struct timespec ts = {0, 0}; | |
if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts)) | |
perror("clock_gettime(CLOCK_PROCESS_CPUTIME_ID)"); | |
if (rc == EXIT_SUCCESS) | |
printf("lines %zu, words %zu, chars %zu\ntook %.6f seconds\n", result.lines, | |
result.words, result.chars, ts.tv_nsec * 1e-9 + ts.tv_sec); | |
return rc; | |
} |
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