symtab.cpp

FastDb是高效的内存数据库系统

//-< SYMTAB.CPP >----------------------------------------------------*--------*
// FastDB                    Version 1.0         (c) 1999  GARRET    *     ?  *
// (Main Memory Database Management System)                          *   /\|  *
//                                                                   *  /  \  *
//                          Created:     20-Nov-98    K.A. Knizhnik  * / [] \ *
//                          Last update: 20-Nov-98    K.A. Knizhnik  * GARRET *
//-------------------------------------------------------------------*--------*
// Symbol table implementation
//-------------------------------------------------------------------*--------*

#define INSIDE_FASTDB

#include "stdtp.h"
#include "sync.h"
#include "symtab.h"

const size_t hashTableSize = 1009;
dbSymbolTable::HashTableItem* dbSymbolTable::hashTable[hashTableSize];

dbSymbolTable dbSymbolTable::instance;

dbSymbolTable::~dbSymbolTable()
{
  for (int i = hashTableSize; --i >= 0;)
  {
    HashTableItem *ip, *next;

    for (ip = hashTable[i]; ip != NULL; ip = next)
    {
      next = ip->next;
      delete ip;
    }
  }
}

#ifdef IGNORE_CASE
#define strcmp(x,y) stricmp(x,y)
#endif

int dbSymbolTable::add
  (char* &str, int tag, bool allocate)
{
  static dbMutex mutex;
  dbCriticalSection cs(mutex);
  unsigned hash = 0;
  byte* p = (byte*)str;

  while (*p != 0)
  {
    byte b = *p++;
#ifdef IGNORE_CASE

    b = tolower(b);
#endif

    hash = hash*31 + b;
  }

  int index = hash % hashTableSize;
  HashTableItem *ip;

  for (ip = hashTable[index]; ip != NULL; ip = ip->next)
  {
    if (ip->hash == hash && strcmp(ip->str, str) == 0)
    {
      str = ip->str;
      return ip->tag;
    }
  }

  ip = new HashTableItem;
  ip->allocated = false;

  if (allocate)
  {
    char* dupstr = new char[strlen(str) + 1];
    strcpy(dupstr, str);
    str = dupstr;
    ip->allocated = true;
  }

  ip->str = str;
  ip->hash = hash;
  ip->tag = tag;
  ip->next = hashTable[index];
  hashTable[index] = ip;
  return tag;
}