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

BUILD.bazel

@@ -13,3 +13,16 @@
 # limitations under the License.
 
 licenses(["notice"])
+
+cc_library(
+    name = "api",
+    hdrs = ["include/astc-codec/astc-codec.h"],
+    visibility = ["//src/decoder:__pkg__"],
+)
+
+cc_library(
+    name = "astc_codec",
+    deps = ["//src/decoder:codec"],
+    includes = ["include"],
+    visibility = ["//visibility:public"],
+)

README.md

@@ -3,6 +3,41 @@
 astc-codec is a software ASTC decoder implementation, which supports the ASTC
 LDR profile.
 
+Example usage:
+
+```
+#include <astc-codec/astc-codec.h>
+
+// ...
+
+std::vector<uint8_t> astc = LoadMyASTCData();
+const size_t width = 640;
+const size_t height = 480;
+
+std::vector<uint8_t> result;
+result.resize(width * height * 4);
+
+bool result = astc_codec::ASTCDecompressToRGBA(
+    astc.data(), astc.size(), width, height, astc_codec::FootprintType::k4x4,
+    result.data(), result.size(), /* stride */ width * 4);
+```
+
+## Building
+
+Install [Bazel](https://bazel.build/), and then run:
+
+```
+bazel build :astc_codec -c opt
+```
+
+astc-codec has been tested on Mac and Linux.
+
+## Run Tests
+
+```
+bazel test //...
+```
+
 ## Contributing
 
 See [CONTRIBUTING.md](CONTRIBUTING.md) for important contributing requirements.
@@ -12,4 +47,4 @@ See [CONTRIBUTING.md](CONTRIBUTING.md) for important contributing requirements.
 astc-codec project is licensed under the Apache License Version 2.0. You can
 find a copy of it in [LICENSE](LICENSE).
 
-This is not an official Google product.
+This is not an officially supported Google product.

include/astc-codec/astc-codec.h

@@ -0,0 +1,75 @@
+// 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_ASTC_CODEC_H_
+#define ASTC_CODEC_ASTC_CODEC_H_
+
+#include <cstddef>
+#include <cstdint>
+
+namespace astc_codec {
+
+// These are the valid ASTC footprints according to the specification in
+// Section C.2.7.
+enum class FootprintType {
+  k4x4,
+  k5x4,
+  k5x5,
+  k6x5,
+  k6x6,
+  k8x5,
+  k8x6,
+  k10x5,
+  k10x6,
+  k8x8,
+  k10x8,
+  k10x10,
+  k12x10,
+  k12x12,
+
+  kCount
+};
+
+// Decompresses ASTC LDR image data to a RGBA32 buffer.
+//
+// Supports formats defined in the KHR_texture_compression_astc_ldr spec and
+// returns UNORM8 values.  sRGB is not supported, and should be implemented
+// by the caller.
+//
+// |astc_data| - Compressed ASTC image buffer, must be at least |astc_data_size|
+//               bytes long.
+// |astc_data_size| - The size of |astc_data|, in bytes.
+// |width| - Image width, in pixels.
+// |height| - Image height, in pixels.
+// |footprint| - The ASTC footprint (block size) of the compressed image buffer.
+// |out_buffer| - Pointer to a buffer where the decompressed image will be
+//                stored, must be at least |out_buffer_size| bytes long.
+// |out_buffer_size| - The size of |out_buffer|, in bytes, at least
+//                     height*out_buffer_stride. If this is too small, this
+//                     function will return false and no data will be
+//                     decompressed.
+// |out_buffer_stride| - The stride that should be used to store rows of the
+//                       decoded image, must be at least 4*width bytes.
+//
+// Returns true if the decompression succeeded, or false if decompression
+// failed, or if the astc_data_size was too small for the given width, height,
+// and footprint, or if out_buffer_size is too small.
+bool ASTCDecompressToRGBA(const uint8_t* astc_data, size_t astc_data_size,
+                          size_t width, size_t height, FootprintType footprint,
+                          uint8_t* out_buffer, size_t out_buffer_size,
+                          size_t out_buffer_stride);
+
+}  // namespace astc_codec
+
+#endif  // ASTC_CODEC_ASTC_CODEC_H_

src/.clang-format

@@ -0,0 +1,4 @@
+BasedOnStyle: Google
+AllowShortCaseLabelsOnASingleLine: true
+AllowShortFunctionsOnASingleLine: Inline
+SpaceAfterTemplateKeyword: false

src/base/BUILD.bazel

@@ -0,0 +1,45 @@
+# 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.
+
+cc_library(
+    name = "base",
+    hdrs = [
+        "bit_stream.h",
+        "bottom_n.h",
+        "math_utils.h",
+        "optional.h",
+        "string_utils.h",
+        "type_traits.h",
+        "uint128.h",
+    ],
+    visibility = ["//src/decoder:__pkg__"],
+)
+
+cc_test(
+    name = "base_test",
+    srcs = [
+        "test/bit_stream_test.cpp",
+        "test/bottom_n_test.cpp",
+        "test/math_utils_test.cpp",
+        "test/optional_test.cpp",
+        "test/string_utils_test.cpp",
+        "test/type_traits_test.cpp",
+        "test/uint128_test.cpp",
+    ],
+    deps = [
+        "@gtest//:gtest_main",
+        ":base",
+    ],
+)
+

src/base/bit_stream.h

@@ -0,0 +1,77 @@
+// 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_BASE_BIT_STREAM_H_
+#define ASTC_CODEC_BASE_BIT_STREAM_H_
+
+#include <cassert>
+#include <cstdint>
+
+namespace astc_codec {
+namespace base {
+
+// Represents a stream of bits that can be read or written in arbitrary-sized
+// chunks.
+template<typename IntType = uint64_t>
+class BitStream {
+ public:
+  // Creates an empty BitStream.
+  BitStream() = default;
+  BitStream(IntType data, uint32_t data_size)
+      : data_(data), data_size_(data_size) {
+    assert(data_size_ <= sizeof(data_) * 8);
+  }
+
+  // Return the number of bits in the stream.
+  uint32_t Bits() const { return data_size_; }
+
+  // Put |size| bits into the stream.
+  // Fails if there is not enough space in the buffer to store the bits.
+  template<typename ResultType>
+  void PutBits(ResultType x, uint32_t size) {
+    assert(data_size_ + size <= sizeof(data_) * 8);
+
+    data_ |= (IntType(x) & MaskFor(size)) << data_size_;
+    data_size_ += size;
+  }
+
+  // Get |count| bits from the stream.
+  // Returns true if |count| bits were successfully retrieved.
+  template<typename ResultType>
+  bool GetBits(uint32_t count, ResultType* result) {
+    if (count <= data_size_) {
+      *result = static_cast<ResultType>(data_ & MaskFor(count));
+      data_ = data_ >> count;
+      data_size_ -= count;
+      return true;
+    } else {
+      *result = 0;
+      return false;
+    }
+  }
+
+ private:
+  IntType MaskFor(uint32_t bits) const {
+    return (bits == sizeof(IntType) * 8) ? ~IntType(0)
+                                         : (IntType(1) << bits) - 1;
+  }
+
+  IntType data_ = 0;
+  uint32_t data_size_ = 0;
+};
+
+}  // namespace base
+}  // namespace astc_codec
+
+#endif  // ASTC_CODEC_BASE_BIT_STREAM_H_

src/base/bottom_n.h

@@ -0,0 +1,78 @@
+// 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_BASE_BOTTOM_N_H_
+#define ASTC_CODEC_BASE_BOTTOM_N_H_
+
+#include <algorithm>
+#include <functional>
+#include <vector>
+
+namespace astc_codec {
+namespace base {
+
+// Used to aggregate the lowest N values of data supplied.
+template<typename T, typename CompareFn = std::less<T>>
+class BottomN {
+ public:
+  typedef std::vector<T> ContainerType;
+
+  // Creates an empty BottomN with limit |max_size|.
+  BottomN(size_t max_size) : max_size_(max_size) { }
+
+  bool Empty() const { return data_.empty(); }
+  size_t Size() const { return data_.size(); }
+
+  const T& Top() const { return data_.front(); }
+
+  void Push(const T& value) {
+    if (data_.size() < max_size_ || compare_(value, Top())) {
+      data_.push_back(value);
+      std::push_heap(data_.begin(), data_.end(), compare_);
+
+      if (Size() > max_size_) {
+        PopTop();
+      }
+    }
+  }
+
+  std::vector<T> Pop() {
+    const size_t len = Size();
+    std::vector<T> result(len);
+
+    for (size_t i = 0; i < len; ++i) {
+      result[len - i - 1] = PopTop();
+    }
+
+    return result;
+  }
+
+ private:
+  T PopTop() {
+    std::pop_heap(data_.begin(), data_.end(), compare_);
+    T result = data_.back();
+    data_.pop_back();
+    return result;
+  }
+
+  ContainerType data_;
+  CompareFn compare_;
+
+  const size_t max_size_;
+};
+
+}  // namespace base
+}  // namespace astc_codec
+
+#endif  // ASTC_CODEC_BASE_BOTTOM_N_H_