1 files changed, 107 insertions, 0 deletions
diff --git a/clang-r353983e/include/llvm/Support/BinaryItemStream.h b/clang-r353983e/include/llvm/Support/BinaryItemStream.h
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+++ b/clang-r353983e/include/llvm/Support/BinaryItemStream.h
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+//===- BinaryItemStream.h ---------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_BINARYITEMSTREAM_H
+#define LLVM_SUPPORT_BINARYITEMSTREAM_H
+
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/Support/BinaryStream.h"
+#include "llvm/Support/BinaryStreamError.h"
+#include "llvm/Support/Error.h"
+#include <cstddef>
+#include <cstdint>
+
+namespace llvm {
+
+template <typename T> struct BinaryItemTraits {
+  static size_t length(const T &Item) = delete;
+  static ArrayRef<uint8_t> bytes(const T &Item) = delete;
+};
+
+/// BinaryItemStream represents a sequence of objects stored in some kind of
+/// external container but for which it is useful to view as a stream of
+/// contiguous bytes.  An example of this might be if you have a collection of
+/// records and you serialize each one into a buffer, and store these serialized
+/// records in a container.  The pointers themselves are not laid out
+/// contiguously in memory, but we may wish to read from or write to these
+/// records as if they were.
+template <typename T, typename Traits = BinaryItemTraits<T>>
+class BinaryItemStream : public BinaryStream {
+public:
+  explicit BinaryItemStream(llvm::support::endianness Endian)
+      : Endian(Endian) {}
+
+  llvm::support::endianness getEndian() const override { return Endian; }
+
+  Error readBytes(uint32_t Offset, uint32_t Size,
+                  ArrayRef<uint8_t> &Buffer) override {
+    auto ExpectedIndex = translateOffsetIndex(Offset);
+    if (!ExpectedIndex)
+      return ExpectedIndex.takeError();
+    const auto &Item = Items[*ExpectedIndex];
+    if (auto EC = checkOffsetForRead(Offset, Size))
+      return EC;
+    if (Size > Traits::length(Item))
+      return make_error<BinaryStreamError>(stream_error_code::stream_too_short);
+    Buffer = Traits::bytes(Item).take_front(Size);
+    return Error::success();
+  }
+
+  Error readLongestContiguousChunk(uint32_t Offset,
+                                   ArrayRef<uint8_t> &Buffer) override {
+    auto ExpectedIndex = translateOffsetIndex(Offset);
+    if (!ExpectedIndex)
+      return ExpectedIndex.takeError();
+    Buffer = Traits::bytes(Items[*ExpectedIndex]);
+    return Error::success();
+  }
+
+  void setItems(ArrayRef<T> ItemArray) {
+    Items = ItemArray;
+    computeItemOffsets();
+  }
+
+  uint32_t getLength() override {
+    return ItemEndOffsets.empty() ? 0 : ItemEndOffsets.back();
+  }
+
+private:
+  void computeItemOffsets() {
+    ItemEndOffsets.clear();
+    ItemEndOffsets.reserve(Items.size());
+    uint32_t CurrentOffset = 0;
+    for (const auto &Item : Items) {
+      uint32_t Len = Traits::length(Item);
+      assert(Len > 0 && "no empty items");
+      CurrentOffset += Len;
+      ItemEndOffsets.push_back(CurrentOffset);
+    }
+  }
+
+  Expected<uint32_t> translateOffsetIndex(uint32_t Offset) {
+    // Make sure the offset is somewhere in our items array.
+    if (Offset >= getLength())
+      return make_error<BinaryStreamError>(stream_error_code::stream_too_short);
+    ++Offset;
+    auto Iter =
+        std::lower_bound(ItemEndOffsets.begin(), ItemEndOffsets.end(), Offset);
+    size_t Idx = std::distance(ItemEndOffsets.begin(), Iter);
+    assert(Idx < Items.size() && "binary search for offset failed");
+    return Idx;
+  }
+
+  llvm::support::endianness Endian;
+  ArrayRef<T> Items;
+
+  // Sorted vector of offsets to accelerate lookup.
+  std::vector<uint32_t> ItemEndOffsets;
+};
+
+} // end namespace llvm
+
+#endif // LLVM_SUPPORT_BINARYITEMSTREAM_H