Initial version of astc-codec for open source release

Contains an implementation of an ASTC decoder that is able to pass the
dEQP ASTC LDR tests.

astc-codec has no external dependencies for the main library, only for
test code, and is licensed under the Apache license.

Components:

include/ - Public API that can decode ASTC LDR data into a RGBA UNORM8
buffer.

src/base/ - Base library with common functionality not directly related
to ASTC decoding.  Contains a uint128 implementation, BitStream for
reading/writing bits with a primitive (or uint128 type), Optional
implementation (to not take a dependency on C++17), and more.

src/decoder/ - Internal implementation of the ASTC decoder.

src/base/test/, src/decoder/test/ - Unit tests (and a fuzzing test) for
the astc decoder.

src/decoder/testdata/ - Sample ASTC images and golden image results for
testing.

src/decoder/tools/ - A tool to inspect contents of an ASTC file.

third_party/ - Third party libraries, only used for tests.

Change-Id: Ia98e5a7dc847daa3d3a48c5e62d94b8fb1cb98bd

1 files changed, 74 insertions, 0 deletions

diff --git a/src/decoder/types.h b/src/decoder/types.h
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--- /dev/null
+++ b/src/decoder/types.h
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+// Copyright 2018 Google LLC
+//
+// 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.
+
+#ifndef ASTC_CODEC_DECODER_ASTC_TYPES_H_
+#define ASTC_CODEC_DECODER_ASTC_TYPES_H_
+
+#include <array>
+#include <string>
+#include <utility>
+
+namespace astc_codec {
+
+// The color endpoint mode determines how the values encoded in the ASTC block
+// are interpreted in order to create the RGBA values for the given endpoint
+// pair. The order of this enum is required to match the ASTC specification in
+// Section C.2.14.
+enum class ColorEndpointMode {
+  kLDRLumaDirect = 0,
+  kLDRLumaBaseOffset,
+  kHDRLumaLargeRange,
+  kHDRLumaSmallRange,
+  kLDRLumaAlphaDirect,
+  kLDRLumaAlphaBaseOffset,
+  kLDRRGBBaseScale,
+  kHDRRGBBaseScale,
+  kLDRRGBDirect,
+  kLDRRGBBaseOffset,
+  kLDRRGBBaseScaleTwoA,
+  kHDRRGBDirect,
+  kLDRRGBADirect,
+  kLDRRGBABaseOffset,
+  kHDRRGBDirectLDRAlpha,
+  kHDRRGBDirectHDRAlpha,
+
+  // The total number of color endpoints defined by the ASTC specification.
+  // This isn't a specific endpoint mode and its sole purpose is to be used
+  // as a constant number.
+  kNumColorEndpointModes
+};
+
+// Returns the class for the given mode as defined in Section C.2.11.
+constexpr int EndpointModeClass(ColorEndpointMode mode) {
+  return static_cast<int>(mode) / 4;
+}
+
+// Returns the number of encoded color values for the given endpoint mode. The
+// number of encoded color values and their range determines the size of the
+// color data in a physical ASTC block. This information is taken from
+// Section C.2.17 of the ASTC specification.
+constexpr int NumColorValuesForEndpointMode(ColorEndpointMode mode) {
+  return (EndpointModeClass(mode) + 1) * 2;
+}
+
+// We define a number of convenience types here that give more logical meaning
+// throughout the ASTC utilities.
+using RgbColor = std::array<int, 3>;
+using RgbaColor = std::array<int, 4>;
+using Endpoint = RgbaColor;
+using EndpointPair = std::pair<Endpoint, Endpoint>;
+
+}  // namespace astc_codec
+
+#endif  // ASTC_CODEC_DECODER_ASTC_TYPES_H_