atomic_counters.hpp

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#ifndef GLK_ATOMIC_COUNTERS_HPP
#define GLK_ATOMIC_COUNTERS_HPP
 
#include <vector>
#include <GL/gl3w.h>
 
namespace glk {
 
class AtomicCounters {
public:
  AtomicCounters(int num_counters, GLenum usage = GL_DYNAMIC_COPY) {
    this->num_counters = num_counters;
 
    glGenBuffers(1, &atomic_buffer);
    glBindBuffer(GL_ATOMIC_COUNTER_BUFFER, atomic_buffer);
    glBufferData(GL_ATOMIC_COUNTER_BUFFER, sizeof(GLuint) * num_counters, nullptr, usage);
    glBindBuffer(GL_ATOMIC_COUNTER_BUFFER, 0);
  }
  ~AtomicCounters() {
    glDeleteBuffers(1, &atomic_buffer);
  }
 
  void reset(GLuint* values = nullptr) {
    glBindBuffer(GL_ATOMIC_COUNTER_BUFFER, atomic_buffer);
 
    if(values) {
      glBufferSubData(GL_ATOMIC_COUNTER_BUFFER, 0, sizeof(GLuint) * num_counters, values);
    } else {
      std::vector<GLuint> v(num_counters, 0);
      glBufferSubData(GL_ATOMIC_COUNTER_BUFFER, 0, sizeof(GLuint) * num_counters, v.data());
    }
 
    glBindBuffer(GL_ATOMIC_COUNTER_BUFFER, 0);
  }
 
  GLuint get_value() const {
    glBindBuffer(GL_ATOMIC_COUNTER_BUFFER, atomic_buffer);
 
    GLuint value;
    glGetBufferSubData(GL_ATOMIC_COUNTER_BUFFER, 0, sizeof(GLuint), &value);
 
    glBindBuffer(GL_ATOMIC_COUNTER_BUFFER, 0);
 
    return value;
  }
 
  std::vector<GLuint> get_values() const {
    glBindBuffer(GL_ATOMIC_COUNTER_BUFFER, atomic_buffer);
 
    std::vector<GLuint> values(num_counters, 0);
    glGetBufferSubData(GL_ATOMIC_COUNTER_BUFFER, 0, sizeof(GLuint) * num_counters, values.data());
 
    glBindBuffer(GL_ATOMIC_COUNTER_BUFFER, 0);
 
    return values;
  }
 
  void bind(GLuint index = 0) const {
    glBindBufferBase(GL_ATOMIC_COUNTER_BUFFER, index, atomic_buffer);
  }
 
  void unbind() const {
    glBindBufferBase(GL_ATOMIC_COUNTER_BUFFER, 0, 0);
  }
 
private:
  int num_counters;
  GLuint atomic_buffer;
};
}  // namespace glk
 
#endif