Line data    Source code

       1             : /*
       2             : Copyright 2015 Esri
       3             : 
       4             : Licensed under the Apache License, Version 2.0 (the "License");
       5             : you may not use this file except in compliance with the License.
       6             : You may obtain a copy of the License at
       7             : 
       8             : http://www.apache.org/licenses/LICENSE-2.0
       9             : 
      10             : Unless required by applicable law or agreed to in writing, software
      11             : distributed under the License is distributed on an "AS IS" BASIS,
      12             : WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      13             : See the License for the specific language governing permissions and
      14             : limitations under the License.
      15             : 
      16             : A local copy of the license and additional notices are located with the
      17             : source distribution at:
      18             : 
      19             : http://github.com/Esri/lerc/
      20             : 
      21             : Contributors:  Thomas Maurer
      22             : */
      23             : 
      24             : #ifndef RLE_H
      25             : #define RLE_H
      26             : 
      27             : #include <cstddef>
      28             : #include "Defines.h"
      29             : 
      30             : NAMESPACE_LERC_START
      31             : 
      32             : /** RLE:
      33             :  *  run length encode a byte array
      34             :  *
      35             :  *  best case resize factor (all bytes are the same):
      36             :  *    (((n + 1) * 3 / 32767 + 2) / n) ~= (3 / 32767)  ~= 0.00009
      37             :  *
      38             :  *  worst case resize factor (no stretch of same bytes):
      39             :  *    ((n + (n + 1) * 2 / 32767 + 2) / n) ~= (1 + 2 / 32767) ~= 1.00006
      40             :  */
      41             : 
      42             : class RLE
      43             : {
      44             : public:
      45          27 :   RLE() : m_minNumEven(5) {}
      46          27 :   virtual ~RLE() {}
      47             : 
      48             :   size_t computeNumBytesRLE(const Byte* arr, size_t numBytes) const;
      49             : 
      50             :   // when done, call
      51             :   // delete[] *arrRLE;
      52             :   bool compress(const Byte* arr, size_t numBytes,
      53             :     Byte** arrRLE, size_t& numBytesRLE, bool verify = false) const;
      54             : 
      55             :   // when done, call
      56             :   // delete[] *arr;
      57             :   static bool decompress(const Byte* arrRLE, size_t nBytesRemaining, Byte** arr, size_t& numBytes);
      58             : 
      59             :   // arr already allocated, just fill
      60             :   static bool decompress(const Byte* arrRLE, size_t nBytesRemaining, Byte* arr, size_t arrSize);
      61             : 
      62             : protected:
      63             :   int m_minNumEven;
      64             : 
      65             :   static void writeCount(short cnt, Byte** ppCnt, Byte** ppDst);
      66             :   static short readCount(const Byte** ppCnt);
      67             : 
      68             : };
      69             : 
      70             : NAMESPACE_LERC_END
      71             : #endif