Introduce InputFile/OutputFile and FileMutex.
FileHandle is replaced with InputFile/OutputFile and FileMutex.
Use InputFile when you want to open a file in read-only.
USe OutputFile when you open a file for writing.
Both of them provide a reliable way to access the files and perform
the I/O operations.
Given a name "foo", FileMutex creates a file named "foo.lock" and
tries to acquire an advisory lock (flock) on this file.
FileHandle, which uses the file it's openning for locking, may corrupt
the file contents when two or more processes are trying to gain the
lock for reading/writing. For example:
Process #2 creates foo
Process #1 opens foo
Process #2 opens foo
Process #2 locks foo (exclusively) (success)
Process #1 locks foo (failed, retry #1)
Process #2 starts writing foo
Process #1 opens and truncates foo (note there’s O_TRUNC in the flag)
Process #2 writes foo continually (foo is corrupted from now on ...)
Process #1 locks foo (failed, retry #2)
...
Process #1 locks foo (reach the max retries and return)
Process #2 gets done on writing foo (foo is corrupted ...)
Process #2 unlocks and closes foo (foo is corrupted)
diff --git a/lib/ExecutionEngine/File.h b/lib/ExecutionEngine/File.h
new file mode 100644
index 0000000..4b7ad4d
--- /dev/null
+++ b/lib/ExecutionEngine/File.h
@@ -0,0 +1,72 @@
+/*
+ * Copyright 2012, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef BCC_EXECUTION_ENGINE_FILE_H
+#define BCC_EXECUTION_ENGINE_FILE_H
+
+#include "FileBase.h"
+
+namespace bcc {
+
+template<enum FileBase::OpenModeEnum OpenMode>
+struct FileAttribute {
+ // The flags to the 2nd argument in ::open().
+ enum { kOpenFlags };
+
+ // Default value of LockMode.
+ enum { kDefaultLockMode };
+};
+
+// FileAttribute for accessing read-only file
+template<>
+struct FileAttribute<FileBase::kReadMode> {
+ enum { kOpenFlags = O_RDONLY };
+ enum { kDefaultLockMode = FileBase::kReadLock };
+};
+
+// FileAttribute for accessing writable file
+template<>
+struct FileAttribute<FileBase::kWriteMode> {
+ enum { kOpenFlags = O_RDWR | O_CREAT | O_TRUNC };
+ enum { kDefaultLockMode = FileBase::kWriteLock };
+};
+
+template<enum FileBase::OpenModeEnum OpenMode>
+class File : public FileBase {
+public:
+ File(const std::string &pFilename, unsigned pFlags)
+ : FileBase(pFilename, FileAttribute<OpenMode>::kOpenFlags, pFlags) { }
+
+ inline bool lock(enum LockModeEnum pMode = static_cast<enum LockModeEnum>(
+ FileAttribute<OpenMode>::kDefaultLockMode),
+ bool pNonblocking = true,
+ unsigned pMaxRetry = FileBase::kDefaultMaxRetryLock,
+ useconds_t pRetryInterval =
+ FileBase::kDefaultRetryLockInterval) {
+ return FileBase::lock(pMode, pNonblocking, pMaxRetry, pRetryInterval);
+ }
+
+ inline android::FileMap *createMap(off_t pOffset, size_t pLength,
+ bool pIsReadOnly =
+ (OpenMode == FileBase::kReadMode)) {
+ return FileBase::createMap(pOffset, pLength, pIsReadOnly);
+ }
+};
+
+
+} // end namespace bcc
+
+#endif // BCC_EXECUTION_ENGINE_FILE_H