Classes/Shaders.m

/*
 
 File: Shaders.m
 
 Abstract: Shader utilities for compiling, linking and validating shaders. 
 It is important to check the result status.
 
 Version: 1.0
 
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*/
 
#import "Shaders.h"
 
/* Create and compile a shader from the provided source(s) */
GLint compileShader(GLuint *shader, GLenum type, GLsizei count, NSString *file)
{
    GLint status;
    const GLchar *sources;
    
    // get source code
    sources = (GLchar *)[[NSString stringWithContentsOfFile:file encoding:NSUTF8StringEncoding error:nil] UTF8String];
    if (!sources)
    {
        NSLog(@"Failed to load vertex shader");
        return 0;
    }
    
    *shader = glCreateShader(type);             // create shader
    glShaderSource(*shader, 1, &sources, NULL); // set source code in the shader
    glCompileShader(*shader);                   // compile shader
    
#if defined(DEBUG)
    GLint logLength;
    glGetShaderiv(*shader, GL_INFO_LOG_LENGTH, &logLength);
    if (logLength > 0)
    {
        GLchar *log = (GLchar *)malloc(logLength);
        glGetShaderInfoLog(*shader, logLength, &logLength, log);
        NSLog(@"Shader compile log:\n%s", log);
        free(log);
    }
#endif
    
    glGetShaderiv(*shader, GL_COMPILE_STATUS, &status);
    if (status == GL_FALSE)
    {
        NSLog(@"Failed to compile shader:\n");
        int i;
        for (i = 0; i < count; i++)
            NSLog(@"%s", sources[i]);
    }
    
    return status;
}
 
 
/* Link a program with all currently attached shaders */
GLint linkProgram(GLuint prog)
{
    GLint status;
    
    glLinkProgram(prog);
    
#if defined(DEBUG)
    GLint logLength;
    glGetProgramiv(prog, GL_INFO_LOG_LENGTH, &logLength);
    if (logLength > 0)
    {
        GLchar *log = (GLchar *)malloc(logLength);
        glGetProgramInfoLog(prog, logLength, &logLength, log);
        NSLog(@"Program link log:\n%s", log);
        free(log);
    }
#endif
    
    glGetProgramiv(prog, GL_LINK_STATUS, &status);
    if (status == GL_FALSE)
        NSLog(@"Failed to link program %d", prog);
    
    return status;
}
 
 
/* Validate a program (for i.e. inconsistent samplers) */
GLint validateProgram(GLuint prog)
{
    GLint logLength, status;
    
    glValidateProgram(prog);
    glGetProgramiv(prog, GL_INFO_LOG_LENGTH, &logLength);
    if (logLength > 0)
    {
        GLchar *log = (GLchar *)malloc(logLength);
        glGetProgramInfoLog(prog, logLength, &logLength, log);
        NSLog(@"Program validate log:\n%s", log);
        free(log);
    }
    
    glGetProgramiv(prog, GL_VALIDATE_STATUS, &status);
    if (status == GL_FALSE)
        NSLog(@"Failed to validate program %d", prog);
    
    return status;
}
 
/* delete shader resources */
void destroyShaders(GLuint vertShader, GLuint fragShader, GLuint prog)
{   
    if (vertShader) {
        glDeleteShader(vertShader);
        vertShader = 0;
    }
    if (fragShader) {
        glDeleteShader(fragShader);
        fragShader = 0;
    }
    if (prog) {
        glDeleteProgram(prog);
        prog = 0;
    }
}