CH14 Colors

/*
 * Tuenti Contest
 * Challenge 14 - Colors
 * Author: Pedro Antonio Pardal Jimena
 * Email: pardal@alu.uma.es
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <string.h>

struct rgb24
{
    unsigned char b, g, r;
} __attribute__((packed));

struct bmp
{
    /* BITMAPFILEHEADER */
    uint16_t    bfType;
    uint32_t    bfSize;
    uint16_t    bfReserved1;
    uint16_t    bfReserved2;
    uint32_t    bfOffBits;

    /* BITMAPINFOHEADER */
    uint32_t    biSize;
    uint32_t    biWidth;
    uint32_t    biHeight;
    uint16_t    biPlanes;
    uint16_t    biBitCount;
    uint32_t    biCompression;
    uint32_t    biSizeImage;
    uint32_t    biXPelsPerMeter;
    uint32_t    biYPelsPerMeter;
    uint32_t    biClrUsed;
    uint32_t    biClrImportant;

    struct rgb24 data[];
} __attribute__((packed));

static struct bmp* read_image()
{
    int fd;
    int longitud;
    struct bmp *img;
    struct stat stbuf;

    if ((fd = open("trabaja.bmp", O_RDONLY)) == -1)
    {
        perror("open");
        exit(-1);
    }

    if (fstat(fd, &stbuf) == -1) {
        perror("fstat");
        exit(-1);
    }
    longitud = stbuf.st_size;

    if ((img = (struct bmp *)mmap((caddr_t) 0, longitud, PROT_READ, MAP_SHARED,
                                  fd, 0)) == MAP_FAILED)
    {
        perror("mmap");
        exit(-1);
    }

    close(fd);

    return img;
}

static void close_image(struct bmp *img)
{
    munmap(img, img->bfSize);
}

static int compute_sum(struct bmp *img, char color, int line)
{
    int i, base, sum;

    base = (img->biHeight - line - 1) * img->biWidth;
    sum = 0;

    for (i = 0; i < img->biWidth; i++)
    {
        switch (color)
        {
            case 'R':
                sum += img->data[base + i].r;
                break;
            case 'G':
                sum += img->data[base + i].g;
                break;
            case 'B':
                sum += img->data[base + i].b;
                break;
        }
    }

    return sum + 1;
}

#define BUFFER_SIZE 0x100

int main(int argc, char *argv[])
{
    struct bmp *img;
    int i;
    char buffer[BUFFER_SIZE];
    char *tok;
    char color;
    int line;
    int sum;

    img = read_image();

    while (fgets(buffer, BUFFER_SIZE, stdin) != NULL)
    {
        color = buffer[0];
        line = atoi(&buffer[1]);
        sum = compute_sum(img, color, line);

        fprintf(stdout, "%d\n", sum);
    }

    return 0;
}