stringpool.cxx

C++ 编写的EROS RTOS

/*
 * Copyright (C) 1998, 1999, Jonathan S. Shapiro.
 *
 * This file is part of the EROS Operating System.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2,
 * or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#include <string.h>
#include <unistd.h>

#include <erosimg/App.hxx>
#include <erosimg/Intern.hxx>
#include <erosimg/StringPool.hxx>

StringPool::StringPool()
{
  for (int i = 0; i < nPockets; i++)
    poolTable[i] = 0;
  
  poolsz = 0;
  poolLimit = 0;
  pool = 0;

  Add(InternedString(""));	/* empty string is ALWAYS first! */
}

StringPool::~StringPool()
{
  for (int i = 0; i < nPockets; i++) {
    PoolEntry* pe = poolTable[i];

    while (pe) {
      PoolEntry *npe = pe->pNext;
      delete pe;
      pe = npe;
    }
  }

  delete pool;
}

void
StringPool::reinit()
{
  if (pool) {
    for (int i = 0; i < nPockets; i++) {
      PoolEntry* pe = poolTable[i];
      poolTable[i] = 0;
      
      while (pe) {
	PoolEntry *npe = pe->pNext;
	delete pe;
	pe = npe;
      }
    }

    delete pool;

    poolsz = 0;
    poolLimit = 0;
    pool = 0;
  }

  Add(InternedString(""));	/* empty string is ALWAYS first! */
}

int
StringPool::Lookup(const InternedString& is)
{
  int pocket = is.Signature() % nPockets;
  PoolEntry *pe = poolTable[pocket];

  while (pe) {
    if (pe->signature == is.Signature() &&
	strcmp(is.str(), pool + pe->offset) == 0)
      return pe->offset;

    pe = pe->pNext;
  }
  return -1;
}

int
StringPool::Add(const InternedString& is)
{
  int pos = Lookup(is);
  if (pos != -1)
    return pos;

  int pocket = is.Signature() % nPockets;
  
  PoolEntry *pe = new PoolEntry;
  pe->signature = is.Signature();
  pe->offset = poolsz;
  pe->pNext = poolTable[pocket];
  poolTable[pocket] = pe;

  /* Now copy the string! */
  const char *s = is.str();
  int len = strlen(s);

  int need = len + 1;		/* terminating null! */
  int avail = poolLimit - poolsz;

  if (avail < need) {
    while (avail < need) {
      poolLimit += 4096;
      avail = poolLimit - poolsz;
    }
    
    char *newPool = new char[poolLimit];

    /* buffer contains nulls, so must use memcpy!! */
    if (pool)
      memcpy(newPool, pool, poolsz); 

    delete [] pool;
    pool = newPool;
  }

  pos = poolsz;

  strcpy(pool + pos, s); /* copies trailing null */
  poolsz += need;

/*  Diag::printf("Pool 0x08%x: add string \"%s\"\n", this, s); */
  return pos;
}

InternedString
StringPool::Get(int offset) const
{
  if (offset < poolsz)
    return InternedString(&pool[offset]);
  return InternedString();
}

int
StringPool::WriteToFile(int fd)
{
  return ::write(fd, pool, poolsz);
}

/* This takes advantage of the fact that the logic for adding new
 * strings is append-always.
 */
bool
StringPool::ReadFromFile(int sfd, int len)
{
  reinit();
  
  char *tmpPool = new char[len];

  if ( ::read(sfd, tmpPool, len) != len )
    return false;

  /* Run through the temporary pool, interning all the strings and
   * adding them to the current pool.  This works only because the
   * pool implementation is append-only and we are starting from an
   * empty pool:
   */

  int offset = 0;

  while (offset < len) {
    InternedString is(&tmpPool[offset]);
    Add(is);

    offset += strlen(is.str());
    offset += 1;
  }

  return true;
}