libj/J/shader.h

#ifndef SHADER_H
#define SHADER_H

#include <iostream>
#include <fstream>
#include <stdexcept>
#include <map>
#include <iterator>

#import <OpenGLES/ES2/gl.h>
#import <OpenGLES/ES2/glext.h>

// TODO: do glValidateProgram, like in the OpenGL template (see bottom)
// TODO: add error checking at set_uniforms?
// TODO: use an uniform map? (benchmark first!)
// TODO: allow arrays is uniforms (now all counts are 1)

namespace J {
    
enum {
    ATTRIB_VERTEX,
    ATTRIB_COLOR,
    NUM_ATTRIBUTES
};

class shader {
    // NOTE: it could be hardcoded to use vertex_shader and fragment_shader.
    typedef std::map<GLenum, GLuint> ShaderMap;
    
	GLuint program;
	ShaderMap shaders;

public:

    // ***********
    // constructor
	shader(std::string vertex_shader_filename, std::string fragment_shader_filename) :
	program(0), shaders() {
		program = glCreateProgram();
		if(program == 0) {
			throw std::runtime_error("Program couldn't be created");
		}

		{   // vertex shader
            // NOTE: C++03 mandates .c_str(), ugly, nothing to do about it...
			std::ifstream vertex_shader(vertex_shader_filename.c_str());
			if(!vertex_shader)
				throw std::runtime_error(vertex_shader_filename + " couldn't be opened");
			compile_shader(vertex_shader, GL_VERTEX_SHADER);
		}
		{   // fragment shader
			std::ifstream fragment_shader(fragment_shader_filename.c_str());
			if(!fragment_shader)
				throw std::runtime_error(fragment_shader_filename + " couldn't be opened");
			compile_shader(fragment_shader, GL_FRAGMENT_SHADER);
		}
        {   // TODO: think of a nice way to implement this
            // Bind attribute locations.
            // This needs to be done prior to linking.
            glBindAttribLocation(program, ATTRIB_VERTEX, "position");
            glBindAttribLocation(program, ATTRIB_COLOR, "color");
        }

		link_program();
	}

	~shader(){
		begin();
		for(ShaderMap::const_iterator i = shaders.begin(); i != shaders.end(); ++i){
            ShaderMap::value_type const & it = *i;
			GLuint shader = it.second;
			glDetachShader(program, shader);
			glDeleteShader(shader);
            // NOTE: If a shader object to be deleted is attached to a program object, it will be flagged for deletion, but it will not be deleted until it is no longer attached to any program object
		}
        
		end();
		glDeleteProgram(program);
	}

    // *****
    // usage
	void begin() {
		glUseProgram(program);
	}

	void end() {
		glUseProgram(0);
	}

    // ***************
    // uniform setters
    
    // float vectors (multiple values)
	void set_uniform(char const* name, float x) const {
		glUniform1f(glGetUniformLocation(program, name), x);
	}

	void set_uniform(char const* name, float x, float y) const {
		glUniform2f(glGetUniformLocation(program, name), x, y);
	}

	void set_uniform(char const* name, float x, float y, float z) const {
		glUniform3f(glGetUniformLocation(program, name), x, y, z);
	}

	void set_uniform(char const* name, float x, float y, float z, float w) const {
		glUniform4f(glGetUniformLocation(program, name), x, y, z, w);
	}

    // integer vectors (multiple values)
	void set_uniform(char const* name, int x) const {
		glUniform1i(glGetUniformLocation(program, name), x);
	}

	void set_uniform(char const* name, int x, int y) const {
		glUniform2i(glGetUniformLocation(program, name), x, y);
	}

	void set_uniform(char const* name, int x, int y, int z) const {
		glUniform3i(glGetUniformLocation(program, name), x, y, z);
	}

	void set_uniform(char const* name, int x, int y, int z, int w) const {
		glUniform4i(glGetUniformLocation(program, name), x, y, z, w);
	}
    
    // Float vectors (array)
	void set_uniform(char const* name, const GLfloat (&value)[4]) const {
		glUniform4fv(glGetUniformLocation(program, name), 1, value);
	}
    
    void set_uniform(char const* name, const GLfloat (&value)[3]) const {
		glUniform3fv(glGetUniformLocation(program, name), 1, value);
	}
    
    void set_uniform(char const* name, const GLfloat (&value)[2]) const {
		glUniform2fv(glGetUniformLocation(program, name), 1, value);
	}
    
    void set_uniform(char const* name, const GLfloat (&value)[1]) const {
		glUniform1fv(glGetUniformLocation(program, name), 1, value);
	}
    
    // Integer vectors (array)
	void set_uniform(char const* name, const GLint (&value)[4]) const {
		glUniform4iv(glGetUniformLocation(program, name), 1, value);
	}
    
    void set_uniform(char const* name, const GLint (&value)[3]) const {
		glUniform3iv(glGetUniformLocation(program, name), 1, value);
	}
    
    void set_uniform(char const* name, const GLint (&value)[2]) const {
		glUniform2iv(glGetUniformLocation(program, name), 1, value);
	}
    
    void set_uniform(char const* name, const GLint (&value)[1]) const {
		glUniform1iv(glGetUniformLocation(program, name), 1, value);
	}

    // matrices (in ES2 only square matrices)
	void set_uniform(char const* name, const GLfloat (&value)[16], GLboolean trans = GL_FALSE) const {
		glUniformMatrix4fv(glGetUniformLocation(program, name), 1, trans, value);
	}
    
    void set_uniform(char const* name, const GLfloat (&value)[9], GLboolean trans = GL_FALSE) const {
		glUniformMatrix3fv(glGetUniformLocation(program, name), 1, trans, value);
	}
    
    void set_uniform(char const* name, const GLfloat (&value)[4], GLboolean trans = GL_FALSE) const {
		glUniformMatrix2fv(glGetUniformLocation(program, name), 1, trans, value);
	}

    // textures (see todo above)
	void set_texture(const char* name, GLenum target, GLuint tex, int textureLocation) const {
		glActiveTexture(GL_TEXTURE0 + textureLocation);
		glBindTexture(target, tex);
		set_uniform(name, textureLocation);
	}
    
    // *********
    // validator
    void validate() {
        GLint status;
        glValidateProgram(program);
        glGetProgramiv(program, GL_VALIDATE_STATUS, &status);
        if(status == GL_FALSE){
            std::cerr << "validator reports:" << std::endl;
            show_log();
			throw std::runtime_error("Program not valid");
        }
    }

private:

    // *******************
    // compiling / linking
	void compile_shader(std::istream& file, GLenum type) {
		// get the c-string, the shortest way (not fastest)
		std::string buffer((std::istreambuf_iterator<char>(file)), std::istreambuf_iterator<char>());
		const char* sptr = buffer.c_str();
		int ssize = buffer.size();

		// create and compile shader
		GLuint shader = glCreateShader(type);
		glShaderSource(shader, 1, &sptr, &ssize);
		glCompileShader(shader);

        #if defined(DEBUG)
		check_compile_status(shader, buffer);
        #endif

		// put it in tha map
		shaders[type] = shader;
	}

	void link_program() {
		// attach all shaders
		for(ShaderMap::const_iterator i = shaders.begin(); i != shaders.end(); ++i){
            ShaderMap::value_type const & it = *i;
			GLuint shader = it.second;
			glAttachShader(program, shader);
		}

		// link
		glLinkProgram(program);

        #if defined(DEBUG)
		check_link_status();
        #endif
	}
    
    // ***************
    // status checking
    void check_compile_status(GLint shader, std::string source = "") {
		GLint status = GL_FALSE;
		glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
		if(status == GL_FALSE || shader == 0) {
			std::cerr << "source:\n" << source << std::endl;
			std::cerr << "shader reports:" << std::endl;
            show_log();
			throw std::runtime_error("Shader failed to compile");
		}
    }

    void check_link_status() {
		GLint status;
		glGetProgramiv(program, GL_LINK_STATUS, &status);
		if(status == GL_FALSE) {
            std::cerr << "linker reports:" << std::endl;
            show_log();
			throw std::runtime_error("Shader failed to link");
		}
    }
    
    void show_log(std::ostream& out = std::cerr) {
        GLsizei infoLength = 0;
        glGetProgramiv(program, GL_INFO_LOG_LENGTH, &infoLength);
        char* infoBuffer = new GLchar[infoLength];
        glGetProgramInfoLog(program, infoLength, &infoLength, infoBuffer);
        out << infoBuffer << std::endl;
        delete [] infoBuffer;
    }
};
    
} // namespace J

#endif // SHADER_H