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/*
Unix SMB/Netbios implementation.
Version 1.9.
file read prediction routines
Copyright (C) Andrew Tridgell 1992-1997
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 of the License, 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, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include "includes.h"
extern int DEBUGLEVEL;
/* variables used by the read prediction module */
static int rp_fd = -1;
static int rp_offset = 0;
static int rp_length = 0;
static int rp_alloced = 0;
static int rp_predict_fd = -1;
static int rp_predict_offset = 0;
static int rp_predict_length = 0;
static int rp_timeout = 5;
static time_t rp_time = 0;
static char *rp_buffer = NULL;
static BOOL predict_skip=False;
time_t smb_last_time=(time_t)0;
/****************************************************************************
handle read prediction on a file
****************************************************************************/
int read_predict(int fd,int offset,char *buf,char **ptr,int num)
{
int ret = 0;
int possible = rp_length - (offset - rp_offset);
possible = MIN(possible,num);
/* give data if possible */
if (fd == rp_fd &&
offset >= rp_offset &&
possible>0 &&
smb_last_time-rp_time < rp_timeout)
{
ret = possible;
if (buf)
memcpy(buf,rp_buffer + (offset-rp_offset),possible);
else
*ptr = rp_buffer + (offset-rp_offset);
DEBUG(5,("read-prediction gave %d bytes of %d\n",ret,num));
}
if (ret == num) {
predict_skip = True;
} else {
predict_skip = False;
/* prepare the next prediction */
rp_predict_fd = fd;
rp_predict_offset = offset + num;
rp_predict_length = num;
}
if (ret < 0) ret = 0;
return(ret);
}
/****************************************************************************
pre-read some data
****************************************************************************/
void do_read_prediction()
{
static int readsize = 0;
if (predict_skip) return;
if (rp_predict_fd == -1)
return;
rp_fd = rp_predict_fd;
rp_offset = rp_predict_offset;
rp_length = 0;
rp_predict_fd = -1;
if (readsize == 0) {
readsize = lp_readsize();
readsize = MAX(readsize,1024);
}
rp_predict_length = MIN(rp_predict_length,2*readsize);
rp_predict_length = MAX(rp_predict_length,1024);
rp_offset = (rp_offset/1024)*1024;
rp_predict_length = (rp_predict_length/1024)*1024;
if (rp_predict_length > rp_alloced)
{
rp_buffer = Realloc(rp_buffer,rp_predict_length);
rp_alloced = rp_predict_length;
if (!rp_buffer)
{
DEBUG(0,("can't allocate read-prediction buffer\n"));
rp_predict_fd = -1;
rp_fd = -1;
rp_alloced = 0;
return;
}
}
if (lseek(rp_fd,rp_offset,SEEK_SET) != rp_offset) {
rp_fd = -1;
rp_predict_fd = -1;
return;
}
rp_length = read(rp_fd,rp_buffer,rp_predict_length);
rp_time = time(NULL);
if (rp_length < 0)
rp_length = 0;
}
/****************************************************************************
invalidate read-prediction on a fd
****************************************************************************/
void invalidate_read_prediction(int fd)
{
if (rp_fd == fd)
rp_fd = -1;
if (rp_predict_fd == fd)
rp_predict_fd = -1;
}
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