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

typedef uint32_t u32;

void bgraify(char *rgb_buf, char *bgra_buf, size_t n_pixels)
{
  for (size_t i = 0; i != n_pixels; i++) {
    /* Naïve approach for a baseline */
    char *p = &rgb_buf[i*3], *q = &bgra_buf[i*4];
    q[0] = p[2];
    q[1] = p[1];
    q[2] = p[0];
  }
}

/* Not currently tested.  Renders an 8-bit PseudoColor image into
   32-bit TrueColor. */
void depalettize(u32 *palette, unsigned char *img, u32 *out, size_t n_pixels)
{
  for (size_t i = 0; i < n_pixels; i++) out[i] = palette[img[i]];
}

void debitmapize(u32 *palette, unsigned char *img, u32 *out, size_t n_pixels)
{
  for (size_t i = 0; i < n_pixels/8; i++) {
    unsigned char c = img[i];
    for (size_t j = 8; j; j--) {
      out[i*8 + j] = palette[1 & c];
      c >>= 1;
    }
  }
}

int main(int argc, char **argv)
{
  if (argc != 3) {
    fprintf(stderr, "Usage: %s largefile 53\n"
            "Converts the RGB data in largefile to a BGRA memory buffer\n"
            "53 times to measure the speed of byteswapping.\n", argv[0]);
    return 1;
  }

  /* XXX copied and pasted from memcpycost.c */
  int f = open(argv[1], O_RDONLY);
  int n = atoi(argv[2]);
  if (f < 0) {
    perror(argv[1]);
    return 1;
  }
  int size = lseek(f, 0, SEEK_END);
  char *m = mmap(0, size, PROT_READ, MAP_SHARED, f, 0);
  if (MAP_FAILED == m) {
    perror("mmap");
    return 1;
  }
  int out_size = size/3*4;
  char *p = malloc(out_size);
  if (!p) {
    perror("malloc");
    return 1;
  }

  printf("BGRAifying %d input bytes into %d output bytes\n",
         size, out_size);
  for (int i = 0; i != n; i++) {
    bgraify(m, p, size/3);
  }
  printf("Byte 53 is %d\n", p[53]);

  return 0;
}