// File:      LDOM_MemManager.cxx
// Created:   26.06.01 11:42:23
// Author:    Alexander GRIGORIEV
// Copyright: OpenCascade 2001
// History:

#include <LDOM_MemManager.hxx>
#include <LDOMBasicString.hxx>

IMPLEMENT_STANDARD_HANDLE  (LDOM_MemManager, MMgt_TShared)
IMPLEMENT_STANDARD_RTTIEXT (LDOM_MemManager, MMgt_TShared)

#define HASH_MASK 255
#define MINIMAL_ROOM 3

typedef unsigned char LDOM_HashValue;     // allocating HASH_MASK integer

inline Standard_Integer convertBlockSize (const Standard_Integer aBlockSize)
{
  return ((aBlockSize - 1) / sizeof(Standard_Integer)) + 1;
}

inline Standard_Boolean compareStrings (char * const           str,
                                        const char *           theString,
                                        const Standard_Integer theLength)
{
// ** This is a bit dangerous (can override the boundary of allocated memory)
//  return (str[theLength] == '\0' &&
//          memcmp (str, theString, theLength) == 0);
// ** This is a more stable (less performant) solution
  if (memcmp (str, theString, theLength)) return Standard_False;
  return (str[theLength] == '\0');
}

//=======================================================================
//function : MemBlock::MemBlock
//purpose  : 
//=======================================================================

inline LDOM_MemManager::MemBlock::MemBlock (const Standard_Integer aSize,
                                            LDOM_MemManager::MemBlock * aFirst)
     : mySize (aSize), myNext (aFirst)
{
  myFreeSpace = myBlock = new Standard_Integer [aSize];
  myEndBlock = myBlock + aSize;
}

//=======================================================================
//function : MemBlock::Allocate
//purpose  : 
//=======================================================================

inline void * LDOM_MemManager::MemBlock::Allocate (const Standard_Integer aSize)
{
  void * aResult = NULL;
  if (aSize <= myEndBlock - myFreeSpace) {
    aResult = myFreeSpace;
    myFreeSpace += aSize;
  }
  return aResult;
}

//=======================================================================
//function : MemBlock::AllocateAndCheck
//purpose  : 
//=======================================================================

void * LDOM_MemManager::MemBlock::AllocateAndCheck
                        (const Standard_Integer             aSize,
                         const LDOM_MemManager::MemBlock *& aFirstWithoutRoom)
{
  void * aResult = NULL;
  Standard_Integer aRoom = myEndBlock - myFreeSpace;
  if (aSize <= aRoom) {
    aResult = myFreeSpace;
    myFreeSpace += aSize;
  }
  if (aRoom < MINIMAL_ROOM) {
    if (aFirstWithoutRoom == NULL) aFirstWithoutRoom = this;
  } else
    aFirstWithoutRoom = NULL;
  return aResult;
}

//=======================================================================
//function : ~MemBlock
//purpose  : Destructor
//=======================================================================

LDOM_MemManager::MemBlock::~MemBlock ()
{
  delete [] myBlock;
  delete myNext;
}

//=======================================================================
//function : HashTable
//purpose  : Constructor
//=======================================================================

LDOM_MemManager::HashTable::HashTable (/* const Standard_Integer   aMask, */
                                       LDOM_MemManager&         aMemManager)
     : myManager        (aMemManager)
{
  Standard_Integer m, nKeys = HASH_MASK + 1;
/*
  Standard_Integer m     = aMask;
  Standard_Integer nKeys = 1;
  while (m) {
    nKeys *= 2;
    m     /= 2;
  }
  myMask = nKeys - 1;
*/
  myTable = (TableItem *) myManager.Allocate (sizeof(TableItem) * nKeys);
  for (m = 0; m < nKeys; m += 2) {
    myTable[m].str    = NULL;
    myTable[m].next   = NULL;
    myTable[m+1].str  = NULL;
    myTable[m+1].next = NULL;
  }
}

//=======================================================================
//function : Hash
//purpose  : CRC-16 hash function
//=======================================================================

Standard_Integer LDOM_MemManager::HashTable::Hash (const char * aString,
                                                   const Standard_Integer aLen)
{
  static const unsigned int wCRC16a[16] =
  {
    0000000,    0140301,    0140601,    0000500,
    0141401,    0001700,    0001200,    0141101,
    0143001,    0003300,    0003600,    0143501,
    0002400,    0142701,    0142201,    0002100,
  };

  static const unsigned int wCRC16b[16] =
  {
    0000000,    0146001,    0154001,    0012000,
    0170001,    0036000,    0024000,    0162001,
    0120001,    0066000,    0074000,    0132001,
    0050000,    0116001,    0104001,    0043000,
  };

  unsigned int aCRC = 0;
  const unsigned char * aPtr = (const unsigned char *) aString;
  for (Standard_Integer i = aLen; i > 0; i--) {
    const unsigned int  bTmp = aCRC ^ (const unsigned int) (* aPtr++);
    aCRC = ((aCRC >> 8) ^ wCRC16a[bTmp & 0x0F]) ^ wCRC16b[(bTmp >> 4) & 0x0F];
  }
  return Standard_Integer (aCRC & HASH_MASK /* myMask */);
}

//=======================================================================
//function : AddString
//purpose  : Add or find a string in the hash table
//=======================================================================

const char * LDOM_MemManager::HashTable::AddString
                                          (const char             * theString,
                                           const Standard_Integer theLen,
                                           Standard_Integer&      theHashIndex)
{
  const char * aResult = NULL;
  if (theString == NULL) return NULL;
  Standard_Integer aHashIndex = Hash (theString, theLen);
  TableItem        * aNode    = &myTable[aHashIndex];
  if (aNode -> str == NULL) {
    LDOM_HashValue * anAlloc = (LDOM_HashValue *)
      myManager.Allocate (theLen + 1 + sizeof(LDOM_HashValue));
    anAlloc[0] = LDOM_HashValue (aHashIndex);
    aNode -> str = (char *) &anAlloc[1];
    memcpy (aNode -> str, theString, theLen);
    aNode -> str [theLen] = '\0';
    aResult = aNode -> str;
  }else{
    if (compareStrings (aNode -> str, theString, theLen))
      aResult = aNode -> str;
    else 
      while (aNode -> next) {
        aNode = aNode -> next;
        if (compareStrings (aNode -> str, theString, theLen)) {
          aResult = aNode -> str;
          break;
        }
      }
    if (aResult == NULL) {
      // Attention!!! We can make this allocation in a separate pool
      //              improving performance
      aNode -> next = (TableItem *) myManager.Allocate (sizeof(TableItem));
      aNode = aNode -> next;
      LDOM_HashValue * anAlloc = (LDOM_HashValue *)
        myManager.Allocate (theLen + 1 + sizeof(LDOM_HashValue));
      anAlloc[0] = LDOM_HashValue (aHashIndex);
      aNode -> str = (char *) &anAlloc[1];
      memcpy (aNode -> str, theString, theLen);
      aNode -> str [theLen] = '\0';
      aResult = aNode -> str;
      aNode -> next = NULL;
    }
  }
  theHashIndex = aHashIndex;
  return aResult;
}

//=======================================================================
//function : LDOM_MemManager
//purpose  : Constructor
//=======================================================================

LDOM_MemManager::LDOM_MemManager (const Standard_Integer aBlockSize)
     : myRootElement            (NULL),
       myFirstBlock             (NULL),
       myFirstWithoutRoom       (NULL),
       myBlockSize              (convertBlockSize(aBlockSize)),
       myHashTable              (NULL) {}

//=======================================================================
//function : ~LDOM_MemManager
//purpose  : Destructor
//=======================================================================

LDOM_MemManager::~LDOM_MemManager ()
{
#ifdef DEB
  Standard_Integer aSomme = 0, aCount = 0;
  MemBlock * aBlock = myFirstBlock;
//FILE * out = fopen ("/tmp/dump","w");
  while (aBlock) {
    aCount ++;
    aSomme += aBlock -> mySize;
//    for (const Standard_Integer * aPtr = aBlock -> myBlock;
//         aPtr < aBlock -> myEndBlock; ) {
//      const char * aStr = (const char *) aPtr;
//      Standard_Integer aLen = strlen (aStr) + 1;
//      if (aLen > 1) fprintf (out, "%s\n", aStr);
//      aPtr += convertBlockSize (aLen);
//    }
    aBlock = aBlock -> Next();
  }
  if (aCount > 1)
    cout << ".. Destroying " << aCount << " LDOM memory allocations: "
         << aSomme / 256 << " kB" << endl;
//fclose (out);
#endif
  delete myFirstBlock;
  if (myHashTable)
    delete myHashTable;
}

//=======================================================================
//function : Allocate
//purpose  : 
//=======================================================================

void * LDOM_MemManager::Allocate (const Standard_Integer theSize)
{
  void                  * aResult = NULL;
  Standard_Integer      aSize = convertBlockSize (theSize);

  if (aSize >= myBlockSize) {
    myFirstBlock = new MemBlock (aSize, myFirstBlock);
    aResult = myFirstBlock -> Allocate (aSize);
  }else{
    MemBlock * aBlock = myFirstBlock;
    if (aBlock == NULL) {
      myFirstBlock = new MemBlock (myBlockSize, myFirstBlock);
      return myFirstBlock -> Allocate (aSize);
    }
    aResult = aBlock -> Allocate (aSize);
    if (aResult)
      return aResult;
    aBlock = aBlock -> Next();
    const MemBlock * aFirstWithoutRoom = NULL;
    while (aBlock != myFirstWithoutRoom) {
      aResult = aBlock -> AllocateAndCheck (aSize, aFirstWithoutRoom);
      if (aResult) break;
      aBlock = aBlock -> Next();
    }
    myFirstWithoutRoom = (MemBlock *&)aFirstWithoutRoom;
    if (aResult == NULL) {
      myFirstBlock = new MemBlock (myBlockSize, myFirstBlock);
      aResult = myFirstBlock -> Allocate (aSize);
    }
  }
  return aResult;
}

//=======================================================================
//function : HashedAllocate
//purpose  : Memory allocation with access via hash table. No new allocation
//           if already present
//=======================================================================

const char * LDOM_MemManager::HashedAllocate (const char           * theString,
                                              const Standard_Integer theLen,
                                              Standard_Integer&      theHash)
{
  if (myHashTable == NULL) myHashTable = new HashTable (* this);
  return myHashTable -> AddString (theString, theLen, theHash);
}

//=======================================================================
//function : HashedAllocate
//purpose  : Memory allocation with access via hash table. No new allocation
//           if already present
//=======================================================================

void LDOM_MemManager::HashedAllocate         (const char             * aString,
                                              const Standard_Integer theLen,
                                              LDOMBasicString&       theResult)
{
  theResult.myType = LDOMBasicString::LDOM_AsciiHashed;
  Standard_Integer aDummy;
  const char * aHashedString = HashedAllocate (aString, theLen, aDummy);
  if (aHashedString != NULL)
    theResult.myVal.ptr = (void *) aHashedString;
}

//=======================================================================
//function : CompareStrings
//purpose  : Compare 
//=======================================================================

Standard_Boolean LDOM_MemManager::CompareStrings
                                        (const char             * theString,
                                         const Standard_Integer theHashValue,
                                         const char             * theHashedStr)
{
  if (((LDOM_HashValue *)theHashedStr)[-1] == LDOM_HashValue(theHashValue))
    if (!strcmp (theString, theHashedStr))
      return Standard_True;
  return Standard_False;
}
