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Caching.h
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1 //===- Caching.h - LLVM Local File Cache ------------------------*- 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 // This file defines the CachedFileStream and the localCache function, which
10 // simplifies caching files on the local filesystem in a directory whose
11 // contents are managed by a CachePruningPolicy.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_SUPPORT_CACHING_H
16 #define LLVM_SUPPORT_CACHING_H
17 
18 #include "llvm/Support/Error.h"
19 
20 namespace llvm {
21 
22 class MemoryBuffer;
23 
24 /// This class wraps an output stream for a file. Most clients should just be
25 /// able to return an instance of this base class from the stream callback, but
26 /// if a client needs to perform some action after the stream is written to,
27 /// that can be done by deriving from this class and overriding the destructor.
29 public:
30  CachedFileStream(std::unique_ptr<raw_pwrite_stream> OS,
31  std::string OSPath = "")
32  : OS(std::move(OS)), ObjectPathName(OSPath) {}
33  std::unique_ptr<raw_pwrite_stream> OS;
34  std::string ObjectPathName;
35  virtual ~CachedFileStream() = default;
36 };
37 
38 /// This type defines the callback to add a file that is generated on the fly.
39 ///
40 /// Stream callbacks must be thread safe.
41 using AddStreamFn = std::function<Expected<std::unique_ptr<CachedFileStream>>(
42  unsigned Task, const Twine &ModuleName)>;
43 
44 /// This is the type of a file cache. To request an item from the cache, pass a
45 /// unique string as the Key. For hits, the cached file will be added to the
46 /// link and this function will return AddStreamFn(). For misses, the cache will
47 /// return a stream callback which must be called at most once to produce
48 /// content for the stream. The file stream produced by the stream callback will
49 /// add the file to the link after the stream is written to. ModuleName is the
50 /// unique module identifier for the bitcode module the cache is being checked
51 /// for.
52 ///
53 /// Clients generally look like this:
54 ///
55 /// if (AddStreamFn AddStream = Cache(Task, Key, ModuleName))
56 /// ProduceContent(AddStream);
57 using FileCache = std::function<Expected<AddStreamFn>(
58  unsigned Task, StringRef Key, const Twine &ModuleName)>;
59 
60 /// This type defines the callback to add a pre-existing file (e.g. in a cache).
61 ///
62 /// Buffer callbacks must be thread safe.
63 using AddBufferFn = std::function<void(unsigned Task, const Twine &ModuleName,
64  std::unique_ptr<MemoryBuffer> MB)>;
65 
66 /// Create a local file system cache which uses the given cache name, temporary
67 /// file prefix, cache directory and file callback. This function does not
68 /// immediately create the cache directory if it does not yet exist; this is
69 /// done lazily the first time a file is added. The cache name appears in error
70 /// messages for errors during caching. The temporary file prefix is used in the
71 /// temporary file naming scheme used when writing files atomically.
73  const Twine &CacheNameRef, const Twine &TempFilePrefixRef,
74  const Twine &CacheDirectoryPathRef,
75  AddBufferFn AddBuffer = [](size_t Task, const Twine &ModuleName,
76  std::unique_ptr<MemoryBuffer> MB) {});
77 } // namespace llvm
78 
79 #endif
llvm
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
llvm::CachedFileStream::OS
std::unique_ptr< raw_pwrite_stream > OS
Definition: Caching.h:33
llvm::CachedFileStream
This class wraps an output stream for a file.
Definition: Caching.h:28
Error.h
llvm::AddBufferFn
std::function< void(unsigned Task, const Twine &ModuleName, std::unique_ptr< MemoryBuffer > MB)> AddBufferFn
This type defines the callback to add a pre-existing file (e.g.
Definition: Caching.h:64
llvm::Expected
Tagged union holding either a T or a Error.
Definition: APFloat.h:41
llvm::CachedFileStream::CachedFileStream
CachedFileStream(std::unique_ptr< raw_pwrite_stream > OS, std::string OSPath="")
Definition: Caching.h:30
llvm::CachedFileStream::ObjectPathName
std::string ObjectPathName
Definition: Caching.h:34
llvm::AMDGPU::PALMD::Key
Key
PAL metadata keys.
Definition: AMDGPUMetadata.h:486
llvm::AddStreamFn
std::function< Expected< std::unique_ptr< CachedFileStream > >(unsigned Task, const Twine &ModuleName)> AddStreamFn
This type defines the callback to add a file that is generated on the fly.
Definition: Caching.h:42
llvm::move
OutputIt move(R &&Range, OutputIt Out)
Provide wrappers to std::move which take ranges instead of having to pass begin/end explicitly.
Definition: STLExtras.h:1861
llvm::CachedFileStream::~CachedFileStream
virtual ~CachedFileStream()=default
ModuleName
Definition: ItaniumDemangle.h:999
function
print Print MemDeps of function
Definition: MemDepPrinter.cpp:82
llvm::localCache
Expected< FileCache > localCache(const Twine &CacheNameRef, const Twine &TempFilePrefixRef, const Twine &CacheDirectoryPathRef, AddBufferFn AddBuffer=[](size_t Task, const Twine &ModuleName, std::unique_ptr< MemoryBuffer > MB) {})
Create a local file system cache which uses the given cache name, temporary file prefix,...
Definition: Caching.cpp:29
llvm::StringRef
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:50
llvm::Twine
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:81
std
Definition: BitVector.h:851
llvm::FileCache
std::function< Expected< AddStreamFn >(unsigned Task, StringRef Key, const Twine &ModuleName)> FileCache
This is the type of a file cache.
Definition: Caching.h:58