main.c

#include <stdio.h>
#include <stdlib.h>

#include "lang1.h"

char * read_entire_file(char const *path);
int main(int argc, char const *argv[]);


char * read_entire_file(char const *path)
{
    FILE *f = fopen(path, "rb");
    if (f == NULL)
        goto error;
    
    if (fseek(f, 0, SEEK_END) != 0)
        goto error_after_open;
    
    long length = ftell(f);
    if (length < 0)
        goto error_after_open;

    rewind(f);

    char *buffer = malloc(((unsigned long) length) + 1);
    if (buffer == NULL)
        goto error_after_malloc;

    buffer[length] = '\0';

    if (length == 0)
        return buffer;

    else if (fread(buffer, ((unsigned long) length), 1, f) != 1)
        goto error_after_malloc;

    fclose(f);
    return buffer;

error_after_malloc:
    free(buffer);
error_after_open:
    fclose(f);
error:
    return NULL;
}

int main(int argc, char const *argv[])
{
    if (argc != 2)
        goto print_usage;

    char const *program_source = read_entire_file(argv[1]);

    if (program_source == NULL)
    {
        printf("Error while reading the input file (%s):\n    ", argv[1]);
        fflush(stdout);
        perror("");
    }
    else if (program_source[0] == '\0')
    {
        printf("Error: The input file (%s) is empty!\n", argv[1]);
    }

    return 0;

print_usage:
    printf("Usage: %s <file>\n", (argv[0][0] != '\0') ? argv[0] : "lang1");
    return 1;
}