common_shader_utils.h

/**
 * From the OpenGL Programming wikibook: http://en.wikibooks.org/wiki/OpenGL_Programming
 * This file is in the public domain.
 * Contributors: Sylvain Beucler
 */
#ifndef _CREATE_SHADER_H
#define _CREATE_SHADER_H
#include <stdio.h>
#include <stdlib.h>
#include <GL/glew.h>
inline char* file_read(const char* filename) {
	  FILE* in = fopen(filename, "rb");
  if (in == NULL) return NULL;

  int res_size = BUFSIZ;
  char* res = (char*)malloc(res_size);
  int nb_read_total = 0;

  while (!feof(in) && !ferror(in)) {
    if (nb_read_total + BUFSIZ > res_size) {
      if (res_size > 10*1024*1024) break;
      res_size = res_size * 2;
      res = (char*)realloc(res, res_size);
    }
    char* p_res = res + nb_read_total;
    nb_read_total += fread(p_res, 1, BUFSIZ, in);
  }
  
  fclose(in);
  res = (char*)realloc(res, nb_read_total + 1);
  res[nb_read_total] = '\0';
  return res;

}
inline void print_log(GLuint object) {
	  GLint log_length = 0;
  if (glIsShader(object))
    glGetShaderiv(object, GL_INFO_LOG_LENGTH, &log_length);
  else if (glIsProgram(object))
    glGetProgramiv(object, GL_INFO_LOG_LENGTH, &log_length);
  else {
    fprintf(stderr, "printlog: Not a shader or a program\n");
    return;
  }

  char* log = (char*)malloc(log_length);

  if (glIsShader(object))
    glGetShaderInfoLog(object, log_length, NULL, log);
  else if (glIsProgram(object))
    glGetProgramInfoLog(object, log_length, NULL, log);

  fprintf(stderr, "%s", log);
  free(log);

}
inline GLuint create_shader(const char* filename, GLenum type) {
	  const GLchar* source = file_read(filename);
  if (source == NULL) {
    fprintf(stderr, "Error opening %s: ", filename); perror("");
    return 0;
  }
  GLuint res = glCreateShader(type);
  const GLchar* sources[] = {
    // Define GLSL version
#ifdef GL_ES_VERSION_2_0
    "#version 100\n"
#else
    "#version 120\n"
#endif
    ,
    // GLES2 precision specifiers
#ifdef GL_ES_VERSION_2_0
    // Define default float precision for fragment shaders:
    (type == GL_FRAGMENT_SHADER) ?
    "#ifdef GL_FRAGMENT_PRECISION_HIGH\n"
    "precision highp float;           \n"
    "#else                            \n"
    "precision mediump float;         \n"
    "#endif                           \n"
    : ""
    // Note: OpenGL ES automatically defines this:
    // #define GL_ES
#else
    // Ignore GLES 2 precision specifiers:
    "#define lowp   \n"
    "#define mediump\n"
    "#define highp  \n"
#endif
    ,
    source };
  glShaderSource(res, 3, sources, NULL);
  free((void*)source);

  glCompileShader(res);
  GLint compile_ok = GL_FALSE;
  glGetShaderiv(res, GL_COMPILE_STATUS, &compile_ok);
  if (compile_ok == GL_FALSE) {
    fprintf(stderr, "%s:", filename);
    print_log(res);
    glDeleteShader(res);
    return 0;
  }

  return res;

}
#endif