compress.cc

/* Copyright (C) 2006 MySQL AB

   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; version 2 of the License.

   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, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA */

#include <config.h>
#include <drizzled/plugin/function.h>
#include <drizzled/item/func.h>
#include <drizzled/function/str/strfunc.h>
#include <drizzled/error.h>
#include <drizzled/sql_error.h>
#include <drizzled/current_session.h>
#include <zlib.h>
#include <plugin/compression/compress.h>

#include <string>

using namespace std;
using namespace drizzled;

String *Item_func_compress::val_str(String *str)
{
  ulong new_size;
  String *res;
  Byte *body;
  char *tmp, *last_char;
  assert(fixed == 1);

  if (!(res= args[0]->val_str(str)))
  {
    null_value= 1;
    return 0;
  }
  null_value= 0;
  if (res->empty()) return res;

  /*
    Citation from zlib.h (comment for compress function):

    Compresses the source buffer into the destination buffer.  sourceLen is
    the byte length of the source buffer. Upon entry, destLen is the total
    size of the destination buffer, which must be at least 0.1% larger than
    sourceLen plus 12 bytes.
    We assume here that the buffer can't grow more than .25 %.
  */
  new_size= res->length() + res->length() / 5 + 12;

  // Check new_size overflow: new_size <= res->length()
  if ((uint32_t) (new_size+5) <= res->length())
  {
    null_value= 1;
    return 0;
  }
  buffer.realloc((uint32_t) new_size + 4 + 1);

  body= ((Byte*)buffer.ptr()) + 4;

  // As far as we have checked res->empty() we can use ptr()
  int err= compress(body, &new_size, (const Bytef*)res->ptr(), res->length());
  if (err != Z_OK)
  {
    drizzled::error_t code= err==Z_MEM_ERROR ? ER_ZLIB_Z_MEM_ERROR : ER_ZLIB_Z_BUF_ERROR;
    push_warning(current_session, DRIZZLE_ERROR::WARN_LEVEL_ERROR, code, ER(code));
    null_value= 1;
    return 0;
  }

  tmp= buffer.ptr(); // int4store is a macro; avoid side effects
  int4store(tmp, res->length() & 0x3FFFFFFF);

  /* This is to ensure that things works for CHAR fields, which trim ' ': */
  last_char= ((char*)body)+new_size-1;
  if (*last_char == ' ')
  {
    *++last_char= '.';
    new_size++;
  }

  buffer.length((uint32_t)new_size + 4);
  return &buffer;
}