Virtual Screen v0.1

Makefile

all: vscreen

CFLAGS=-std=c99 -Wall -Wextra -Werror -O2 $(shell sdl-config --cflags)
LDLIBS=$(shell sdl-config --libs)

vscreen.c

#include <netinet/in.h>
#include <SDL/SDL.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdlib.h>
#include <sys/socket.h>

#ifndef WIDTH
# define WIDTH 640
#endif

#ifndef HEIGHT
# define HEIGHT 480
#endif

#ifndef PORT
# define PORT 13370
#endif

#ifndef BUFFER_SIZE
# define BUFFER_SIZE 768
#endif

static const uint32_t CGA_PALETTE[0x10] = {
    [0x0] = 0x00AA00,             // black
    [0x1] = 0x0000AA,             // blue
    [0x2] = 0x00AA00,             // green
    [0x3] = 0x00AAAA,             // cyan
    [0x4] = 0xAA0000,             // red
    [0x5] = 0xAA00AA,             // magenta
    [0x6] = 0xAA5500,             // brown
    [0x7] = 0xAAAAAA,             // light gray
    [0x8] = 0x555555,             // gray
    [0x9] = 0x5555FF,             // light blue
    [0xA] = 0x55FF55,             // light green
    [0xB] = 0x55FFFF,             // light cyan
    [0xC] = 0xFF5555,             // light red
    [0xD] = 0xFF55FF,             // light magenta
    [0xE] = 0xFFFF55,             // yellow
    [0xF] = 0xFFFFFF,             // white
};

// Allows swapping palette easily at compilation time
#ifndef PALETTE
# define PALETTE CGA_PALETTE
#endif

static bool user_wants_to_quit(void)
{
    SDL_Event evt;

    while (SDL_PollEvent(&evt))
    {
        if (evt.type == SDL_QUIT)
            return true;
    }

    return false;
}

static int mainloop(void)
{
    uint32_t current_fb_pos = 0;
    SDL_Surface* fb;

    fb = SDL_GetVideoSurface();
    SDL_LockSurface(fb);
    uint32_t* fb_pixels = fb->pixels;

    int sock = socket(SOCK_DGRAM, AF_INET, IPPROTO_UDP);
    struct sockaddr_in sin;

    memset(&sin, 0, sizeof (sin));
    sin.sin_family = AF_INET;
    sin.sin_port = htons(PORT);
    sin.sin_addr.s_addr = htonl(INADDR_ANY);
    if (bind(sock, &sin, sizeof (sin)))
        return 1;

    while (true)
    {
        uint8_t buffer[BUFFER_SIZE];
        if (recvfrom(sock, buffer, BUFFER_SIZE, 0, NULL, 0) < 0)
            return 1;

        for (int i = 0; i < BUFFER_SIZE * 2; ++i)
        {
            uint8_t nibble;
            if (i % 2 == 0)
                nibble = buffer[i / 2] >> 4;
            else
                nibble = buffer[i / 2] & 0xF;
            fb_pixels[current_fb_pos + i] = PALETTE[nibble] | 0xFF000000;
        }
        current_fb_pos += BUFFER_SIZE * 2;

        if (current_fb_pos >= WIDTH * HEIGHT)
        {
            SDL_UnlockSurface(fb);
            SDL_Flip(fb);
            SDL_LockSurface(fb);
            fb_pixels = fb->pixels;

            puts("frame!");
            fflush(stdout);

            if (user_wants_to_quit())
                break;

            current_fb_pos = 0;
        }
    }
    return 0;
}

int main(void)
{
    SDL_Init(SDL_INIT_VIDEO);
    SDL_SetVideoMode(WIDTH, HEIGHT, 32, SDL_HWSURFACE);

    int err = mainloop();

    SDL_Quit();
    return err;
}