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/*
* =========================================================================
* big_buf_io - A library to allow efficient small reads and writes.
* Copyright (c) 1997,2001 Fred M. Erickson
*
* 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, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
* =========================================================================
*
*
* Routines that let you do a lot of small reads and writes from a file,
* without a lot of OS penalty. Simply call buf_read() and buf_write()
* instead of read() and write(). These routines read/write a file in
* large chunks and pass you the data in the small chunks that you ask
* for. Note some caveats:
*
* You must call buf_write(filedes, buf, 0) when you are done
* writing so that it can flush the write buffer.
* (Should maybe implement buf_flush() to take care of this.)
*
* You can't reset the file pointer with lseek() or you will
* mess up these routines.
*
* You can only use these routines with one file at a time,
* since there is only one buffer to hold the data.
*
* If you only have one file to read, you can simply open it
* and begin calling these routines. If you have more than
* one file to read (consecutively, of course), you should use
* buf_open() to open the files, so that proper initialization
* gets done. buf_close() has been added for completeness, but
* it doesn't do anything except call close().
*
* get_a_line() fills a buffer with information until it finds a newline,
* or runs out of space.
*/
#include <sys/types.h>
#include <fcntl.h>
int buf_open(const char *, int, mode_t, ...);
int buf_close(int);
ssize_t buf_read(int, void *, size_t);
ssize_t buf_write(int, const void *, size_t);
ssize_t get_a_line(int, void *, size_t);
#define BUF_SIZE 16384
static r_place = 0;
static r_size = 0;
static w_place = 0;
int
buf_open(const char *pathname, int flags, mode_t mode, ...)
{
r_place = 0;
r_size = 0;
w_place = 0;
if (flags & O_CREAT) {
return(open(pathname, flags, mode));
}
else {
return(open(pathname, flags));
}
}
int
buf_close(int fdesc)
{
return(close(fdesc));
}
ssize_t
buf_read(int filedes, void *buf, size_t nbyte)
{
static char bigbuf[BUF_SIZE];
long amount;
long tmp_nbyte;
char *local_buf;
local_buf = (char *)buf;
tmp_nbyte = nbyte;
while (tmp_nbyte > 0) {
if ((r_size <= 0) || (r_place == r_size)) {
r_size = read(filedes, bigbuf, BUF_SIZE);
if (r_size <= 0) {
return(r_size);
}
r_place = 0;
}
amount = (r_size - r_place) >= tmp_nbyte ? tmp_nbyte : r_size - r_place;
memcpy(local_buf, &bigbuf[r_place], amount);
local_buf = local_buf + amount;
r_place = r_place + amount;
tmp_nbyte = tmp_nbyte - amount;
}
return(nbyte);
}
ssize_t
buf_write(int filedes, const void *buf, size_t nbyte)
{
static char bigbuf[BUF_SIZE];
long amount;
long tmp_nbyte;
long ret_val;
char *local_buf;
local_buf = (char *)buf;
if (nbyte == 0) {
ret_val = write(filedes, bigbuf, w_place);
if (ret_val < 0) {
return(ret_val);
}
else {
return(0);
}
}
tmp_nbyte = nbyte;
while (tmp_nbyte > 0) {
amount = (BUF_SIZE - w_place) >= tmp_nbyte ? tmp_nbyte : BUF_SIZE - w_place;
memcpy(&bigbuf[w_place], local_buf, amount);
local_buf = local_buf + amount;
w_place = w_place + amount;
tmp_nbyte = tmp_nbyte - amount;
if (w_place == BUF_SIZE) {
if (write(filedes, bigbuf, BUF_SIZE) != BUF_SIZE) {
return(-1);
}
w_place = 0;
}
}
return(nbyte);
}
ssize_t
get_a_line(int filedes, void *buf, size_t nbyte)
{
long i = 0;
ssize_t ret_val;
while (i < nbyte) {
ret_val = buf_read(filedes, buf + i, 1);
if (ret_val < 0) {
return(ret_val);
}
else if (ret_val == 0) {
return((ssize_t)i);
}
if (*((unsigned char *)buf + i) == '\n') {
return(i + 1);
}
i++;
}
return((ssize_t)nbyte);
}
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