be/src/exec/hdfs-lzo-text-scanner.h

// Licensed to the Apache Software Foundation (ASF) under one
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// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you 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
//
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#ifndef IMPALA_EXEC_HDFS_LZO_TEXT_SCANNER_H
#define IMPALA_EXEC_HDFS_LZO_TEXT_SCANNER_H

#include "common/status.h"
#include "exec/scan-node.h"
#include "exec/hdfs-scanner.h"
#include "exec/hdfs-scan-node-base.h"
#include "util/spinlock.h"

namespace impala {

/// This is a wrapper for calling the external HdfsLzoTextScanner
/// The LZO scanner class is implemented in a dynamically linked library so that
/// Impala does not include GPL code.  The two entry points are:
/// IssueInitialRanges -- issue calls to the I/O manager to read the file headers
/// GetHdfsLzoTextScanner -- returns a pointer to the Scanner object.
class HdfsLzoTextScanner {
 public:
  static HdfsScanner* GetHdfsLzoTextScanner(HdfsScanNodeBase* scan_node,
      RuntimeState* state);
  static Status IssueInitialRanges(HdfsScanNodeBase* scan_node,
                                   const std::vector<HdfsFileDesc*>& files);

 private:
  /// Impala LZO library name -- GPL code.
  const static std::string LIB_IMPALA_LZO;

  /// If non-OK, then we have tried and failed to load the LZO library.
  static Status library_load_status_;

  /// Lock to protect loading of the lzo file library.
  static SpinLock lzo_load_lock_;

  /// Dynamically linked function to create the Lzo Scanner Object.
  static HdfsScanner* (*CreateLzoTextScanner)
      (HdfsScanNodeBase* scan_node, RuntimeState* state);

  /// Dynamically linked function to set the initial scan ranges.
  static Status (*LzoIssueInitialRanges)(
      HdfsScanNodeBase* scan_node, const std::vector<HdfsFileDesc*>& files);

  /// Dynamically loads CreateLzoTextScanner and LzoIssueInitialRanges.
  /// lzo_load_lock_ should be taken before calling this method.
  static Status LoadLzoLibrary();
};
}
#endif