remove_spaces.c

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/mman.h>

char* remove_spaces_asm16(char *in, char *out, unsigned int count);

char* remove_spaces_straight(char* in, char* out, unsigned int count) {
    while (count--) {
        if (*in != ' ') {
            *out++ = *in;
        }
        in++;
    }
    return out;
}

int main(int argc, char **argv) {
    if (argc < 2) {
        printf("Usage: %s <file> [asm]\n", argv[0]);
        exit(0);
    }

    int fd;
    struct stat fs;

    fd = open(argv[1], O_RDONLY);
    if (fd < 0) {
        printf("Error opening file \"%s\"\n", argv[1]);
        exit(1);
    }

    fstat(fd, &fs);
    printf("File size: %li\n", fs.st_size);
    if (fs.st_size % 16) {
        fputs("File size must be divisible by 16\n", stderr);
        exit(1);
    }

    char *in = mmap(NULL, fs.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
    char *out = malloc(fs.st_size);
    char *end;

    if (argc > 2) {
        end = remove_spaces_asm16(in, out, fs.st_size);
        printf("Spaces found (asm): %li\n", fs.st_size - (end - out));
        out[22] = '\0';
        printf("\"%s\"\n", out);
    } else {
        end = remove_spaces_straight(in, out, fs.st_size);
        printf("Spaces found (straight): %li\n", fs.st_size - (end - out));
        out[22] = '\0';
        printf("\"%s\"\n", out);
    }
}