stasis-aries-wal/src/stasis/page/compression/rle.h

#ifndef _ROSE_COMPRESSION_RLE_H__
#define _ROSE_COMPRESSION_RLE_H__

// Copyright 2007 Google Inc. All Rights Reserved.
// Author: sears@google.com (Rusty Sears)

#include <limits.h>
#include <ctype.h>
#include "pstar.h"

namespace rose {

template <class TYPE>
class Rle {

 public:
  typedef uint32_t block_index_t;
  typedef uint16_t copy_count_t;
  typedef TYPE TYP;

  static const copy_count_t MAX_COPY_COUNT = USHRT_MAX;

  struct triple_t {
    slot_index_t index;
    copy_count_t copies;
    //byte foo[100]; // <-- Uncomment to test boundaries
    TYPE data;
  };

  static const int PLUGIN_ID = 1;

  inline void offset(TYPE off) { nth_block_ptr(0)->data = off; };
  inline size_t max_overrun() { return sizeof(triple_t); }

  /** @see For::append */
  inline slot_index_t append(int xid, const TYPE dat,
			     byte_off_t* except, byte * exceptions,
			     int * free_bytes);
  /** @see For::recordRead */
  inline TYPE *recordRead(int xid, slot_index_t slot, byte *exceptions,
                          TYPE *scratch);
  /**
    This constructor initializes a new Rle region.

    @param xid the transaction that created the new region.
  */
  Rle(int xid, void * mem): mem_(mem), last_(0) {
    *block_count_ptr() = 1;
    triple_t * n = last_block_ptr();
    n->index = 0;
    n->copies = 0;
    n->data = 0;
  }
  /**
     This constructor is called when existing RLE data is read from
     disk.
  */
  Rle(void * mem): mem_(mem), last_(0) { }

  Rle() : mem_(0), last_(0) {}

  /**
      @see For::bytes_used();
  */
  inline byte_off_t bytes_used() {
    return ((intptr_t)(last_block_ptr()+1))-(intptr_t)mem_;
  }

  inline void init_mem(void * mem) {
    mem_=mem;
    last_=0;
    *block_count_ptr() = 1;
    triple_t * n = nth_block_ptr(0);
    n->index = 0;
    n->copies = 0;
    n->data = 0;
  }

  inline void mem(void * mem) {
    mem_=mem;
    last_=0;
  }
 private:
  inline TYPE offset() { return nth_block_ptr(0)->dat; }
  inline block_index_t* block_count_ptr() {
    return reinterpret_cast<block_index_t*>(mem_);
  }
  inline triple_t* nth_block_ptr(block_index_t n) {
    return reinterpret_cast<triple_t*>(block_count_ptr()+1) + n;
  }
  inline triple_t* last_block_ptr() {
    return nth_block_ptr(*block_count_ptr()-1);
  }
  inline triple_t* new_block_ptr() {
    return nth_block_ptr(*block_count_ptr());
  }
  void * mem_;
  block_index_t last_;
};

} // namespace rose
#endif  // _ROSE_COMPRESSION_RLE_H__