From d0e18bdb7924c71cdca8dd983711171d87ef28be Mon Sep 17 00:00:00 2001
From: Benjamin Barenblat <bbarenblat@gmail.com>
Date: Mon, 17 Jan 2022 23:12:32 -0500
Subject: glplanet, an OpenGL-based planetary renderer
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glplanet draws Earth like it currently appears from space, putting
nighttime areas in shadow and daytime areas in light. It’s modeled
after Xplanet (http://xplanet.sourceforge.net/), but whereas Xplanet is
entirely a CPU-resident program, glplanet draws using OpenGL. It’s thus
much less resource-intensive, particularly when using high-resolution
textures.
---
 src/gl/buffer.cc | 105 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 105 insertions(+)
 create mode 100644 src/gl/buffer.cc

(limited to 'src/gl/buffer.cc')

diff --git a/src/gl/buffer.cc b/src/gl/buffer.cc
new file mode 100644
index 0000000..a56e36a
--- /dev/null
+++ b/src/gl/buffer.cc
@@ -0,0 +1,105 @@
+// Copyright 2021 Benjamin Barenblat
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+
+#include "src/gl/buffer.h"
+
+#include <stdint.h>
+
+#include <stdexcept>
+
+#include "src/gl/error.h"
+#include "src/util.h"
+#include "third_party/abseil/absl/strings/substitute.h"
+#include "third_party/glew/include/GL/glew.h"
+
+namespace gl {
+
+namespace {
+
+constexpr uint16_t Pack(Buffer::AccessFrequency frequency,
+                        Buffer::AccessNature nature) noexcept {
+  static_assert(sizeof(Buffer::AccessFrequency) == 1);
+  static_assert(sizeof(Buffer::AccessNature) == 1);
+  return FromEnum(frequency) << 8 | FromEnum(nature);
+}
+
+GLenum CombineFrequencyAndNature(Buffer::AccessFrequency frequency,
+                                 Buffer::AccessNature nature) {
+  using F = ::gl::Buffer::AccessFrequency;
+  using N = ::gl::Buffer::AccessNature;
+  switch (Pack(frequency, nature)) {
+    case Pack(F::kStream, N::kDraw):
+      return GL_STREAM_DRAW;
+    case Pack(F::kStream, N::kRead):
+      return GL_STREAM_READ;
+    case Pack(F::kStream, N::kCopy):
+      return GL_STREAM_COPY;
+
+    case Pack(F::kStatic, N::kDraw):
+      return GL_STATIC_DRAW;
+    case Pack(F::kStatic, N::kRead):
+      return GL_STATIC_READ;
+    case Pack(F::kStatic, N::kCopy):
+      return GL_STATIC_COPY;
+
+    case Pack(F::kDynamic, N::kDraw):
+      return GL_DYNAMIC_DRAW;
+    case Pack(F::kDynamic, N::kRead):
+      return GL_DYNAMIC_READ;
+    case Pack(F::kDynamic, N::kCopy):
+      return GL_DYNAMIC_COPY;
+
+    default:
+      throw std::invalid_argument(absl::Substitute(
+          "GL: invalid access frequency and/or nature ($0, $1)",
+          FromEnum(frequency), FromEnum(nature)));
+  }
+}
+
+}  // namespace
+
+Buffer::Buffer(const Buffer& other)
+    : size_bytes_(other.size_bytes_),
+      frequency_(other.frequency_),
+      nature_(other.nature_) {
+  gl_internal::CheckThreadSafety();
+
+  glCreateBuffers(1, &buffer_);
+  gl_internal::UnnecessaryErrorCheck();
+
+  glNamedBufferData(buffer_, size_bytes_, /*data=*/nullptr,
+                    CombineFrequencyAndNature(frequency_, nature_));
+  // An error check is necessary here to detect allocation failure, but it can
+  // be folded into a future error check.
+  gl_internal::UnnecessaryErrorCheck();
+
+  glCopyNamedBufferSubData(other.buffer_, buffer_, /*readOffset=*/0,
+                           /*writeOffset=*/0, other.size_bytes_);
+  // This error check is necessary because other might be mapped.
+  gl_internal::ErrorCheck();
+
+  fprintf(stderr, "BUFFER COPY\n");
+}
+
+void Buffer::SetData(const void* data, int size_bytes,
+                     AccessFrequency frequency, AccessNature nature) {
+  gl_internal::CheckThreadSafety();
+  glNamedBufferData(buffer_, size_bytes, data,
+                    CombineFrequencyAndNature(frequency, nature));
+  // This error check is necessary to detect allocation failure.
+  gl_internal::ErrorCheck();
+  size_bytes_ = size_bytes;
+}
+
+}  // namespace gl
-- 
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