http.c

#include "http.h"

#include <sys/fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>

const int BUFFER_SIZE = 104857600;

const char *get_mime_type(const char *file_ext) {
    if (strcasecmp(file_ext, "html") == 0 || strcasecmp(file_ext, "htm") == 0) {
        return "text/html";
    } else if (strcasecmp(file_ext, "txt") == 0) {
        return "text/plain";
    } else if (strcasecmp(file_ext, "jpg") == 0 || strcasecmp(file_ext, "jpeg") == 0) {
        return "image/jpeg";
    } else if (strcasecmp(file_ext, "png") == 0) {
        return "image/png";
    } else {
        return "application/octet-stream";
    }
}

void build_http_response(const char *file_name, 
                        const char *file_ext, 
                        char *response, 
                        size_t *response_len) {
    // build HTTP header
    const char *mime_type = get_mime_type(file_ext);
    char *header = (char *)malloc(BUFFER_SIZE * sizeof(char));
    snprintf(header, BUFFER_SIZE,
             "HTTP/1.1 200 OK\r\n"
             "Content-Type: %s\r\n"
             "\r\n",
             mime_type);

    // if file not exist, response is 404 Not Found
    int file_fd = open(file_name, O_RDONLY);
    if (file_fd == -1) {
        snprintf(response, BUFFER_SIZE,
                 "HTTP/1.1 404 Not Found\r\n"
                 "Content-Type: text/plain\r\n"
                 "\r\n"
                 "404 Not Found");
        *response_len = strlen(response);
        return;
    }

    // get file size for Content-Length
    struct stat file_stat;
    fstat(file_fd, &file_stat);
    off_t file_size = file_stat.st_size;

    // copy header to response buffer
    *response_len = 0;
    memcpy(response, header, strlen(header));
    *response_len += strlen(header);

    // copy file to response buffer
    ssize_t bytes_read;
    while ((bytes_read = read(file_fd, 
                            response + *response_len, 
                            BUFFER_SIZE - *response_len)) > 0) {
        *response_len += bytes_read;
    }
    free(header);
    close(file_fd);
}