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 // Copyright (c) 2011, Google Inc.

 // All rights reserved.

 //

 // Redistribution and use in source and binary forms, with or without

 // modification, are permitted provided that the following conditions are

 // met:

 //

 //     * Redistributions of source code must retain the above copyright

 // notice, this list of conditions and the following disclaimer.

 //     * Redistributions in binary form must reproduce the above

 // copyright notice, this list of conditions and the following disclaimer

 // in the documentation and/or other materials provided with the

 // distribution.

 //     * Neither the name of Google Inc. nor the names of its

 // contributors may be used to endorse or promote products derived from

 // this software without specific prior written permission.

 //

 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 // memory_range.h: Define the google_breakpad::MemoryRange class, which

 // is a lightweight wrapper with a pointer and a length to encapsulate

 // a contiguous range of memory.

 #ifndef COMMON_MEMORY_RANGE_H_

 #define COMMON_MEMORY_RANGE_H_

 #include <stddef.h>

 #include "google_breakpad/common/breakpad_types.h"

 namespace google_breakpad {

 // A lightweight wrapper with a pointer and a length to encapsulate a

 // contiguous range of memory. It provides helper methods for checked

 // access of a subrange of the memory. Its implemementation does not

 // allocate memory or call into libc functions, and is thus safer to use

 // in a crashed environment.

 class MemoryRange {

  public:

   MemoryRange() : data_(NULL), length_(0) {}

   MemoryRange(const void* data, size_t length) {

     Set(data, length);

   }

   // Returns true if this memory range contains no data.

   bool IsEmpty() const {

     // Set() guarantees that |length_| is zero if |data_| is NULL.

     return length_ == 0;

   }

   // Resets to an empty range.

   void Reset() {

     data_ = NULL;

     length_ = 0;

   }

   // Sets this memory range to point to |data| and its length to |length|.

   void Set(const void* data, size_t length) {

     data_ = reinterpret_cast<const uint8_t*>(data);

     // Always set |length_| to zero if |data_| is NULL.

     length_ = data ? length : 0;

   }

   // Returns true if this range covers a subrange of |sub_length| bytes

   // at |sub_offset| bytes of this memory range, or false otherwise.

   bool Covers(size_t sub_offset, size_t sub_length) const {

     // The following checks verify that:

     // 1. sub_offset is within [ 0 .. length_ - 1 ]

     // 2. sub_offset + sub_length is within

     //    [ sub_offset .. length_ ]

     return sub_offset < length_ &&

            sub_offset + sub_length >= sub_offset &&

            sub_offset + sub_length <= length_;

   }

   // Returns a raw data pointer to a subrange of |sub_length| bytes at

   // |sub_offset| bytes of this memory range, or NULL if the subrange

   // is out of bounds.

   const void* GetData(size_t sub_offset, size_t sub_length) const {

     return Covers(sub_offset, sub_length) ? (data_ + sub_offset) : NULL;

   }

   // Same as the two-argument version of GetData() but uses sizeof(DataType)

   // as the subrange length and returns an |DataType| pointer for convenience.

   template <typename DataType>

   const DataType* GetData(size_t sub_offset) const {

     return reinterpret_cast<const DataType*>(

         GetData(sub_offset, sizeof(DataType)));

   }

   // Returns a raw pointer to the |element_index|-th element of an array

   // of elements of length |element_size| starting at |sub_offset| bytes

   // of this memory range, or NULL if the element is out of bounds.

   const void* GetArrayElement(size_t element_offset,

                               size_t element_size,

                               unsigned element_index) const {

     size_t sub_offset = element_offset + element_index * element_size;

     return GetData(sub_offset, element_size);

   }

   // Same as the three-argument version of GetArrayElement() but deduces

   // the element size using sizeof(ElementType) and returns an |ElementType|

   // pointer for convenience.

   template <typename ElementType>

   const ElementType* GetArrayElement(size_t element_offset,

                                      unsigned element_index) const {

     return reinterpret_cast<const ElementType*>(

         GetArrayElement(element_offset, sizeof(ElementType), element_index));

   }

   // Returns a subrange of |sub_length| bytes at |sub_offset| bytes of

   // this memory range, or an empty range if the subrange is out of bounds.

   MemoryRange Subrange(size_t sub_offset, size_t sub_length) const {

     return Covers(sub_offset, sub_length) ?

         MemoryRange(data_ + sub_offset, sub_length) : MemoryRange();

   }

   // Returns a pointer to the beginning of this memory range.

   const uint8_t* data() const { return data_; }

   // Returns the length, in bytes, of this memory range.

   size_t length() const { return length_; }

  private:

   // Pointer to the beginning of this memory range.

   const uint8_t* data_;

   // Length, in bytes, of this memory range.

   size_t length_;

 };

 }  // namespace google_breakpad

 #endif  // COMMON_MEMORY_RANGE_H_