LLVM 19.0.0git
BinaryItemStream.h
Go to the documentation of this file.
1//===- BinaryItemStream.h ---------------------------------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#ifndef LLVM_SUPPORT_BINARYITEMSTREAM_H
10#define LLVM_SUPPORT_BINARYITEMSTREAM_H
11
12#include "llvm/ADT/ArrayRef.h"
15#include "llvm/Support/Error.h"
16#include <cstddef>
17#include <cstdint>
18
19namespace llvm {
20
21template <typename T> struct BinaryItemTraits {
22 static size_t length(const T &Item) = delete;
23 static ArrayRef<uint8_t> bytes(const T &Item) = delete;
24};
25
26/// BinaryItemStream represents a sequence of objects stored in some kind of
27/// external container but for which it is useful to view as a stream of
28/// contiguous bytes. An example of this might be if you have a collection of
29/// records and you serialize each one into a buffer, and store these serialized
30/// records in a container. The pointers themselves are not laid out
31/// contiguously in memory, but we may wish to read from or write to these
32/// records as if they were.
33template <typename T, typename Traits = BinaryItemTraits<T>>
35public:
37
38 llvm::endianness getEndian() const override { return Endian; }
39
41 ArrayRef<uint8_t> &Buffer) override {
42 auto ExpectedIndex = translateOffsetIndex(Offset);
43 if (!ExpectedIndex)
44 return ExpectedIndex.takeError();
45 const auto &Item = Items[*ExpectedIndex];
46 if (auto EC = checkOffsetForRead(Offset, Size))
47 return EC;
48 if (Size > Traits::length(Item))
49 return make_error<BinaryStreamError>(stream_error_code::stream_too_short);
50 Buffer = Traits::bytes(Item).take_front(Size);
51 return Error::success();
52 }
53
55 ArrayRef<uint8_t> &Buffer) override {
56 auto ExpectedIndex = translateOffsetIndex(Offset);
57 if (!ExpectedIndex)
58 return ExpectedIndex.takeError();
59 Buffer = Traits::bytes(Items[*ExpectedIndex]);
60 return Error::success();
61 }
62
63 void setItems(ArrayRef<T> ItemArray) {
64 Items = ItemArray;
65 computeItemOffsets();
66 }
67
68 uint64_t getLength() override {
69 return ItemEndOffsets.empty() ? 0 : ItemEndOffsets.back();
70 }
71
72private:
73 void computeItemOffsets() {
74 ItemEndOffsets.clear();
75 ItemEndOffsets.reserve(Items.size());
76 uint64_t CurrentOffset = 0;
77 for (const auto &Item : Items) {
78 uint64_t Len = Traits::length(Item);
79 assert(Len > 0 && "no empty items");
80 CurrentOffset += Len;
81 ItemEndOffsets.push_back(CurrentOffset);
82 }
83 }
84
85 Expected<uint32_t> translateOffsetIndex(uint64_t Offset) {
86 // Make sure the offset is somewhere in our items array.
87 if (Offset >= getLength())
88 return make_error<BinaryStreamError>(stream_error_code::stream_too_short);
89 ++Offset;
90 auto Iter = llvm::lower_bound(ItemEndOffsets, Offset);
91 size_t Idx = std::distance(ItemEndOffsets.begin(), Iter);
92 assert(Idx < Items.size() && "binary search for offset failed");
93 return Idx;
94 }
95
96 llvm::endianness Endian;
97 ArrayRef<T> Items;
98
99 // Sorted vector of offsets to accelerate lookup.
100 std::vector<uint64_t> ItemEndOffsets;
101};
102
103} // end namespace llvm
104
105#endif // LLVM_SUPPORT_BINARYITEMSTREAM_H
Returns the sub type a function will return at a given Idx Should correspond to the result type of an ExtractValue instruction executed with just that one unsigned Idx
uint64_t Size
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
endianness Endian
ArrayRef - Represent a constant reference to an array (0 or more elements consecutively in memory),...
Definition: ArrayRef.h:41
ArrayRef< T > take_front(size_t N=1) const
Return a copy of *this with only the first N elements.
Definition: ArrayRef.h:228
BinaryItemStream represents a sequence of objects stored in some kind of external container but for w...
llvm::endianness getEndian() const override
Error readLongestContiguousChunk(uint64_t Offset, ArrayRef< uint8_t > &Buffer) override
Given an offset into the stream, read as much as possible without copying any data.
Error readBytes(uint64_t Offset, uint64_t Size, ArrayRef< uint8_t > &Buffer) override
Given an offset into the stream and a number of bytes, attempt to read the bytes and set the output A...
BinaryItemStream(llvm::endianness Endian)
uint64_t getLength() override
Return the number of bytes of data in this stream.
void setItems(ArrayRef< T > ItemArray)
An interface for accessing data in a stream-like format, but which discourages copying.
Definition: BinaryStream.h:34
Error checkOffsetForRead(uint64_t Offset, uint64_t DataSize)
Definition: BinaryStream.h:58
Lightweight error class with error context and mandatory checking.
Definition: Error.h:160
static ErrorSuccess success()
Create a success value.
Definition: Error.h:334
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
@ Offset
Definition: DWP.cpp:456
auto lower_bound(R &&Range, T &&Value)
Provide wrappers to std::lower_bound which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:1950
endianness
Definition: bit.h:70
static ArrayRef< uint8_t > bytes(const T &Item)=delete
static size_t length(const T &Item)=delete