Subversion Repositories QNX 8.QNX8 LLVM/Clang compiler suite

//===- Caching.h - LLVM Local File Cache ------------------------*- 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

//

//===----------------------------------------------------------------------===//

//

// This file defines the CachedFileStream and the localCache function, which

// simplifies caching files on the local filesystem in a directory whose

// contents are managed by a CachePruningPolicy.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_SUPPORT_CACHING_H

#define LLVM_SUPPORT_CACHING_H

#include "llvm/Support/Error.h"

namespace llvm {

class MemoryBuffer;

/// This class wraps an output stream for a file. Most clients should just be

/// able to return an instance of this base class from the stream callback, but

/// if a client needs to perform some action after the stream is written to,

/// that can be done by deriving from this class and overriding the destructor.

class CachedFileStream {

public:

  CachedFileStream(std::unique_ptr<raw_pwrite_stream> OS,

                   std::string OSPath = "")

      : OS(std::move(OS)), ObjectPathName(OSPath) {}

  std::unique_ptr<raw_pwrite_stream> OS;

  std::string ObjectPathName;

  virtual ~CachedFileStream() = default;

};

/// This type defines the callback to add a file that is generated on the fly.

///

/// Stream callbacks must be thread safe.

using AddStreamFn = std::function<Expected<std::unique_ptr<CachedFileStream>>(

    unsigned Task, const Twine &ModuleName)>;

/// This is the type of a file cache. To request an item from the cache, pass a

/// unique string as the Key. For hits, the cached file will be added to the

/// link and this function will return AddStreamFn(). For misses, the cache will

/// return a stream callback which must be called at most once to produce

/// content for the stream. The file stream produced by the stream callback will

/// add the file to the link after the stream is written to. ModuleName is the

/// unique module identifier for the bitcode module the cache is being checked

/// for.

///

/// Clients generally look like this:

///

/// if (AddStreamFn AddStream = Cache(Task, Key, ModuleName))

///   ProduceContent(AddStream);

using FileCache = std::function<Expected<AddStreamFn>(

    unsigned Task, StringRef Key, const Twine &ModuleName)>;

/// This type defines the callback to add a pre-existing file (e.g. in a cache).

///

/// Buffer callbacks must be thread safe.

using AddBufferFn = std::function<void(unsigned Task, const Twine &ModuleName,

                                       std::unique_ptr<MemoryBuffer> MB)>;

/// Create a local file system cache which uses the given cache name, temporary

/// file prefix, cache directory and file callback.  This function does not

/// immediately create the cache directory if it does not yet exist; this is

/// done lazily the first time a file is added.  The cache name appears in error

/// messages for errors during caching. The temporary file prefix is used in the

/// temporary file naming scheme used when writing files atomically.

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) {});

} // namespace llvm

#endif