opengl.c

#include "opengl.h"

VBO vbo_init(GLfloat* vertices) {
    VBO out;

    glGenBuffers(1, &(out.vbo));
    glBindBuffer(GL_ARRAY_BUFFER, out.vbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    vbo_unbind();

    return out;
}

void vbo_bind(VBO vbo)
{
    glBindBuffer(GL_ARRAY_BUFFER, vbo.vbo);
}

void vbo_unbind()
{
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
}

void vbo_kill(VBO vbo)
{
    glDeleteBuffers(1,vbo.vbo);
}


char* read_file(const char* filename){
    long n, r;
    FILE *fp = fopen(filename, "r");

    fseek(fp, 0L, SEEK_END);
    n = ftell(fp);
    fseek(fp, 0L, SEEK_SET);
    
    char * out = (char*)malloc(n);
    r = fread(out, 1, n, fp);
    fclose(fp);
    out[r-1] = '\0';

    return out;
}

GLuint compile(const char* filename, GLenum type)
{
    GLint compile_ok = GL_FALSE;

    const char *source = read_file(filename);
    GLuint id = glCreateShader(type);
    glShaderSource(id, 1, &source, NULL);
    free((void*)source);
    glCompileShader(id);
    glGetShaderiv(id, GL_COMPILE_STATUS, &compile_ok);
    if (!compile_ok) {
        GLint log_length;
        glGetShaderiv(id, GL_INFO_LOG_LENGTH, &log_length);
        char* log = (char*)malloc(log_length);
        glGetShaderInfoLog(id, log_length, NULL, log);
        fprintf(stderr, "%s", log);
        free(log);
    }

    return id;
}

Shader shader_init(const char *vs_filename, const char *fs_filename)
{
    GLint link_ok = GL_FALSE;

    GLuint vs=compile(vs_filename, GL_VERTEX_SHADER);
    GLuint fs=compile(fs_filename, GL_FRAGMENT_SHADER);

    GLuint program = glCreateProgram();
    glAttachShader(program, vs);
    glAttachShader(program, fs);
    glLinkProgram(program);
    glGetProgramiv(program, GL_LINK_STATUS, &link_ok);
    if (!link_ok) {
        GLint log_length;
        glGetProgramiv(program, GL_INFO_LOG_LENGTH, &log_length);
        char* log = (char*)malloc(log_length);
        glGetProgramInfoLog(program, log_length, NULL, log);
        fprintf(stderr, "%s", log);
        free(log);
    }

    Shader shader = {.fs=fs,.vs=vs,.program=program};
    return shader;
}


void shader_kill(Shader shader)
{
    glDeleteProgram(shader.program);
}


/* void get_attribute(const char *name) */
/* { */
/*  attributes[name] = glGetAttribLocation(program, name); */
/*  if (attributes[name] == -1) { */
/*      fprintf(stderr, "Could not get attribute %s\n", name); */
/*  } */
/* } */

/* void get_uniform(const char *name) */
/* { */
/*  uniforms[name] = glGetUniformLocation(program, name); */
/*  if (uniforms[name] == -1) { */
/*      fprintf(stderr, "Could not get uniform %s\n", name); */
/*  } */
/* } */

/* void bind_attribute(Shader shader, GLuint location, const GLchar* name) */
/* { */
/*  shader.attrib[location] = location; */
/*  glBindAttribLocation(shader.program, location, name); */
/* } */

void shader_use(Shader shader)
{
    glUseProgram(shader.program);
    /* map<string, GLint>::iterator p; */
    /* for (p = attributes.begin(); p != attributes.end(); ++p) { */
    /*  glEnableVertexAttribArray(p->second); */
    /* } */
}