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/OutputFile.h b/lib/ExecutionEngine/OutputFile.h
new file mode 100644
index 0000000..4de8863
--- /dev/null
+++ b/lib/ExecutionEngine/OutputFile.h
@@ -0,0 +1,53 @@
+/*
+ * 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_OUTPUT_FILE_H
+#define BCC_EXECUTION_ENGINE_OUTPUT_FILE_H
+
+#include "File.h"
+#include "FileBase.h"
+
+namespace llvm {
+ class raw_fd_ostream;
+}
+
+namespace bcc {
+
+class OutputFile : public File<FileBase::kWriteMode> {
+ typedef File<FileBase::kWriteMode> super;
+public:
+ // Generate a unique temporary filename from pFileTemplate and open it in
+ // an OutputFile returned. The filename will be pFileTemplate with
+ // a dot ('.') plus six random characters appended. Return NULL on error.
+ static OutputFile *CreateTemporary(const std::string &pFileTemplate,
+ unsigned pFlags);
+
+ OutputFile(const std::string &pFilename, unsigned pFlags = 0);
+
+ ssize_t write(const void *pBuf, size_t count);
+
+ void truncate();
+
+ // This is similar to the system call dup(). It creates a copy of the file
+ // descriptor it contains and wrap it in llvm::raw_fd_ostream object. It
+ // returns a non-NULL object if everything goes well and user should later
+ // use delete operator to destroy it by itself.
+ llvm::raw_fd_ostream *dup();
+};
+
+} // end namespace bcc
+
+#endif // BCC_EXECUTION_ENGINE_OUTPUT_FILE_H