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. 28 class CachedFileStream { 29 public: 30 CachedFileStream(std::unique_ptr<raw_pwrite_stream> OS, 31 std::string OSPath = "") OS(std::move (OS))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. 72 Expected<FileCache> localCache( 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 80