#include <stdio.h>
#include <stdbool.h>
#include <epoxy/gl.h>
#include <GL/freeglut.h>
#include <math.h>
#include <stdio.h>

#define ARRAY_SIZE(ary) (sizeof(ary) / sizeof((ary)[0]))

static void
test_r16(void)
{
        GLushort buf[65536];
        GLubyte without_pbo[65536], with_pbo[65536];
        GLuint i;
        GLuint tex;
        GLuint pbo;
        float expected;
        GLuint expected_int;

        for (i = 0; i < ARRAY_SIZE(buf); i++)
                buf[i] = i;

        glGenTextures(1, &tex);
        glBindTexture(GL_TEXTURE_2D, tex);
        glTexImage2D(GL_TEXTURE_2D,
                     0, /* level */
                     GL_R16,
                     256, 256, /* width/height */
                     0, /* border */
                     GL_RED,
                     GL_UNSIGNED_SHORT,
                     buf);
        glGetTexImage(GL_TEXTURE_2D,
                      0, /* level */
                      GL_RED,
                      GL_UNSIGNED_BYTE,
                      without_pbo);

        glGenBuffers(1, &pbo);
        glBindBuffer(GL_PIXEL_PACK_BUFFER, pbo);
        glBufferData(GL_PIXEL_PACK_BUFFER,
                     sizeof without_pbo,
                     NULL, /* data */
                     GL_STATIC_READ);
        glGetTexImage(GL_TEXTURE_2D,
                      0, /* level */
                      GL_RED,
                      GL_UNSIGNED_BYTE,
                      NULL);
        glGetBufferSubData(GL_PIXEL_PACK_BUFFER,
                           0, /* offset */
                           sizeof with_pbo,
                           with_pbo);
        glBindBuffer(GL_PIXEL_PACK_BUFFER, 0);
        glDeleteBuffers(1, &pbo);

        for (i = 0; i < ARRAY_SIZE(buf); i++) {
                expected = i * 255.0f / 65535.0f;
                expected_int = roundf(expected);
                if (expected_int != without_pbo[i] ||
                    expected_int != with_pbo[i]) {
                        printf("source_value=%i float=%f expected=%i "
                               "without_pbo=%i with_pbo=%i\n",
                               i,
                               expected,
                               expected_int,
                               without_pbo[i],
                               with_pbo[i]);
                }
        }
}

int
main(int argc, char **argv)
{
        glutInit(&argc, argv);
        glutCreateWindow("GL_R16 to unsigned byte test");

        test_r16();

        return EXIT_SUCCESS;
}