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/**
* From the OpenGL Programming wikibook: http://en.wikibooks.org/wiki/OpenGL_Programming
* This file is in the public domain.
* Contributors: Sylvain Beucler
*/
#include <stdio.h>
#include <stdlib.h>
#include "shader_utils.h"
/**
* Store all the file's contents in memory, useful to pass shaders
* source code to OpenGL
*/
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;
}
/**
* Display compilation errors from the OpenGL shader compiler
*/
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);
}
/**
* Compile the shader from file 'filename', with error handling
*/
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;
}