Shaders.cpp

// routines for creating shaders
#include <GL/glew.h>
#include <stdio.h>
#include "Shaders.h"
#include <stdarg.h>


char *readShaderFile(char *filename) {
    FILE *fid;
    char *buffer;
    int len;
    int n;

    fid = fopen(filename,"r");
    if(fid == NULL) {
        printf("can't open shader file: %s\n", filename);
        return(0);
    }

    fseek(fid, 0, SEEK_END);
    len = ftell(fid);
    rewind(fid);

    buffer = new char[len+1];
    n = fread(buffer, sizeof(char), len, fid);
    buffer[n] = 0;

    return buffer;

}


int buildShader(int type, char *filename) {
    int shader;
    char *source;
    int result;
    char *buffer;

    shader = glCreateShader(type);
    source = readShaderFile(filename);
    if(source == 0)
        return 0;

    glShaderSource(shader, 1, (const  GLchar **) &source, 0);
    glCompileShader(shader);
    glGetShaderiv(shader, GL_COMPILE_STATUS, &result);
    if(result != GL_TRUE) {
        printf("shader compile error: %s\n",filename);
        glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &result);
        buffer = new char[result];
        glGetShaderInfoLog(shader, result, 0, buffer);
        printf("%s\n", buffer);
        delete buffer;
        return(0);
    }

    return(shader);
}


int buildProgram(int first, ...) {
    int result;
    char *buffer;
    int program;
    va_list argptr;
    int shader;
    int vs = 0;
    int fs = 0;
    int type;

    program = glCreateProgram();
    if(first != 0) {
        glAttachShader(program,first);
        glGetShaderiv(first, GL_SHADER_TYPE, &type);
        if(type == GL_VERTEX_SHADER)
            vs++;
        if(type == GL_FRAGMENT_SHADER)
            fs++;
    }

    va_start(argptr,first);
    while((shader = va_arg(argptr,int)) != 0) {
        glAttachShader(program,shader);
        glGetShaderiv(shader, GL_SHADER_TYPE, &type);
        if(type == GL_VERTEX_SHADER)
            vs++;
        if(type == GL_FRAGMENT_SHADER)
            fs++;
    }

    if(vs == 0) {
        printf("no vertex shader\n");
    }
    if(fs == 0) {
        printf("no fragment shader\n");
    }
    glLinkProgram(program);
    glGetProgramiv(program, GL_LINK_STATUS, &result);
    if(result != GL_TRUE) {
        printf("program link error\n");
        glGetProgramiv(program, GL_INFO_LOG_LENGTH, &result);
        buffer = new char[result];
        glGetProgramInfoLog(program, result, 0, buffer);
        printf("%s\n",buffer);
        delete buffer;
        return(0);
    }

    return(program);

}


void dumpProgram(int program, char *description) {
    char name[256];
    GLsizei length;
    GLint size;
    GLenum type;
    int uniforms;
    int attributes;
    int shaders;
    int i;

    printf("Information for shader: %s\n",description);

    if(!glIsProgram(program)) {
        printf("not a valid shader program\n");
        return;
    }

    glGetProgramiv(program, GL_ATTACHED_SHADERS, &shaders);
    printf("Number of shaders: %d\n",shaders);

    glGetProgramiv(program,GL_ACTIVE_UNIFORMS,&uniforms);
    printf("uniforms: %d\n",uniforms);
    for(i=0; i<uniforms; i++) {
        glGetActiveUniform(program, i, 256, &length ,&size ,&type, name);
        printf("  name: %s\n",name);
    }
    glGetProgramiv(program,GL_ACTIVE_ATTRIBUTES,&attributes);
    printf("attributes: %d\n",attributes);
    for(i=0; i<attributes; i++) {
        glGetActiveAttrib(program, i, 256, &length, &size, &type, name);
        printf("  name: %s\n",name);
    }
}