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 20namespace llvm { 21 22class 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. 28class CachedFileStream { 29public: 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. 41using 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); 57using 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. 63using 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. 72Expected<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