Playing with buffers.

src/xenia/gpu/gl4/circular_buffer.cc

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+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2014 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include <xenia/gpu/gl4/circular_buffer.h>
+
+#include <poly/assert.h>
+#include <poly/math.h>
+#include <xenia/gpu/gpu-private.h>
+
+namespace xe {
+namespace gpu {
+namespace gl4 {
+
+extern "C" GLEWContext* glewGetContext();
+extern "C" WGLEWContext* wglewGetContext();
+
+CircularBuffer::CircularBuffer(size_t capacity)
+    : capacity_(capacity),
+      write_head_(0),
+      buffer_(0),
+      gpu_base_(0),
+      host_base_(nullptr) {}
+
+CircularBuffer::~CircularBuffer() {
+  glUnmapNamedBuffer(buffer_);
+  glDeleteBuffers(1, &buffer_);
+}
+
+bool CircularBuffer::Initialize() {
+  glCreateBuffers(1, &buffer_);
+  glNamedBufferStorage(buffer_, capacity_, nullptr,
+                       GL_MAP_WRITE_BIT | GL_MAP_PERSISTENT_BIT);
+  host_base_ = reinterpret_cast<uint8_t*>(glMapNamedBufferRange(
+      buffer_, 0, capacity_, GL_MAP_WRITE_BIT | GL_MAP_FLUSH_EXPLICIT_BIT |
+                                 GL_MAP_UNSYNCHRONIZED_BIT |
+                                 GL_MAP_PERSISTENT_BIT));
+  assert_not_null(host_base_);
+  if (!host_base_) {
+    return false;
+  }
+  glMakeNamedBufferResidentNV(buffer_, GL_WRITE_ONLY);
+  glGetNamedBufferParameterui64vNV(buffer_, GL_BUFFER_GPU_ADDRESS_NV,
+                                   &gpu_base_);
+  return true;
+}
+
+CircularBuffer::Allocation CircularBuffer::Acquire(size_t length) {
+  // Addresses must always be % 256.
+  length = poly::round_up(length, 256);
+
+  assert_true(length <= capacity_, "Request too large");
+
+  if (write_head_ + length > capacity_) {
+    // Flush and wait.
+    WaitUntilClean();
+  }
+
+  Allocation allocation;
+  allocation.host_ptr = host_base_ + write_head_;
+  allocation.gpu_ptr = gpu_base_ + write_head_;
+  allocation.length = length;
+  write_head_ += length;
+  return allocation;
+}
+
+void CircularBuffer::Commit(Allocation allocation) {
+  glFlushMappedNamedBufferRange(buffer_, allocation.gpu_ptr - gpu_base_,
+                                allocation.length);
+}
+
+void CircularBuffer::WaitUntilClean() {
+  glFinish();
+  write_head_ = 0;
+}
+
+}  // namespace gl4
+}  // namespace gpu
+}  // namespace xe