1    :  // Copyright 2013 Google Inc. All Rights Reserved.
   2    :  //
   3    :  // Licensed under the Apache License, Version 2.0 (the "License");
   4    :  // you may not use this file except in compliance with the License.
   5    :  // You may obtain a copy of the License at
   6    :  //
   7    :  //     http://www.apache.org/licenses/LICENSE-2.0
   8    :  //
   9    :  // Unless required by applicable law or agreed to in writing, software
  10    :  // distributed under the License is distributed on an "AS IS" BASIS,
  11    :  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12    :  // See the License for the specific language governing permissions and
  13    :  // limitations under the License.
  14    :  //
  15    :  // Declares a utility class for mapping slices of shared files (buffers, from
  16    :  // the point of view of the call-trace service) into memory.
  17    :  
  18    :  #ifndef SYZYGY_TRACE_SERVICE_MAPPED_BUFFER_H_
  19    :  #define SYZYGY_TRACE_SERVICE_MAPPED_BUFFER_H_
  20    :  
  21    :  #include <stdint.h>
  22    :  
  23    :  #include "base/logging.h"
  24    :  
  25    :  namespace trace {
  26    :  namespace service {
  27    :  
  28    :  // Forward declare.
  29    :  struct Buffer;
  30    :  
  31    :  // A utility class for creating a scoped on demand memory mapped view into a
  32    :  // shared file. Automatically unmaps the buffer when destroyed.
  33    :  class MappedBuffer {
  34    :   public:
  35    :    // Constructor.
  36    :    // @param buffer The buffer to be mapped.
  37  E :    explicit MappedBuffer(Buffer* buffer)
  38  E :        : buffer_(buffer), base_(NULL), data_(NULL) {
  39  E :      DCHECK(buffer != NULL);
  40  E :    }
  41    :  
  42  E :    ~MappedBuffer() {
  43  E :      Unmap();
  44  E :    }
  45    :  
  46    :    // Maps the current buffer. Logs an error message on failure.
  47    :    // @returns true on success, false otherwise.
  48    :    bool Map();
  49    :  
  50    :    // Unmaps the current buffer. Logs an error message on failure.
  51    :    // @returns true on success, false otherwise.
  52    :    bool Unmap();
  53    :  
  54    :    // @returns true if the buffer is mapped, false otherwise.
  55  E :    bool IsMapped() const { return data_ != NULL; }
  56    :  
  57    :    // Returns a pointer to the mapped buffer data.
  58  E :    uint8_t* data() const { return data_; }
  59    :  
  60    :   protected:
  61    :    Buffer* buffer_;
  62    :    uint8_t* base_;
  63    :    uint8_t* data_;
  64    :  };
  65    :  
  66    :  }  // namespace service
  67    :  }  // namespace trace
  68    :  
  69    :  #endif  // SYZYGY_TRACE_SERVICE_MAPPED_BUFFER_H_