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/*
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* =========================================================================
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* big_buf_io - A library to allow efficient small reads and writes.
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* Copyright (c) 1997,2001 Fred M. Erickson
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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* =========================================================================
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*
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*
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* Routines that let you do a lot of small reads and writes from a file,
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* without a lot of OS penalty. Simply call buf_read() and buf_write()
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* instead of read() and write(). These routines read/write a file in
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* large chunks and pass you the data in the small chunks that you ask
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* for. Note some caveats:
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*
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* You must call buf_write(filedes, buf, 0) when you are done
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* writing so that it can flush the write buffer.
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* (Should maybe implement buf_flush() to take care of this.)
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*
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* You can't reset the file pointer with lseek() or you will
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* mess up these routines.
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*
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* You can only use these routines with one file at a time,
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* since there is only one buffer to hold the data.
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*
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* If you only have one file to read, you can simply open it
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* and begin calling these routines. If you have more than
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* one file to read (consecutively, of course), you should use
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* buf_open() to open the files, so that proper initialization
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* gets done. buf_close() has been added for completeness, but
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* it doesn't do anything except call close().
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*
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* get_a_line() fills a buffer with information until it finds a newline,
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* or runs out of space.
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*/
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#include <sys/types.h>
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#include <fcntl.h>
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int buf_open(const char *, int, mode_t, ...);
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int buf_close(int);
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ssize_t buf_read(int, void *, size_t);
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ssize_t buf_write(int, const void *, size_t);
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ssize_t get_a_line(int, void *, size_t);
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#define BUF_SIZE 16384
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static r_place = 0;
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static r_size = 0;
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static w_place = 0;
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int
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buf_open(const char *pathname, int flags, mode_t mode, ...)
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{
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r_place = 0;
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r_size = 0;
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w_place = 0;
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if (flags & O_CREAT) {
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return(open(pathname, flags, mode));
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}
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else {
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return(open(pathname, flags));
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}
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}
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int
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buf_close(int fdesc)
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{
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return(close(fdesc));
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}
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ssize_t
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buf_read(int filedes, void *buf, size_t nbyte)
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{
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static char bigbuf[BUF_SIZE];
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long amount;
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long tmp_nbyte;
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char *local_buf;
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local_buf = (char *)buf;
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tmp_nbyte = nbyte;
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while (tmp_nbyte > 0) {
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if ((r_size <= 0) || (r_place == r_size)) {
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r_size = read(filedes, bigbuf, BUF_SIZE);
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if (r_size <= 0) {
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return(r_size);
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}
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r_place = 0;
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}
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amount = (r_size - r_place) >= tmp_nbyte ? tmp_nbyte : r_size - r_place;
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memcpy(local_buf, &bigbuf[r_place], amount);
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local_buf = local_buf + amount;
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r_place = r_place + amount;
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tmp_nbyte = tmp_nbyte - amount;
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}
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return(nbyte);
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}
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ssize_t
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buf_write(int filedes, const void *buf, size_t nbyte)
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{
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static char bigbuf[BUF_SIZE];
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long amount;
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long tmp_nbyte;
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long ret_val;
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char *local_buf;
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local_buf = (char *)buf;
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if (nbyte == 0) {
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ret_val = write(filedes, bigbuf, w_place);
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if (ret_val < 0) {
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return(ret_val);
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}
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else {
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return(0);
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}
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}
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tmp_nbyte = nbyte;
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while (tmp_nbyte > 0) {
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amount = (BUF_SIZE - w_place) >= tmp_nbyte ? tmp_nbyte : BUF_SIZE - w_place;
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memcpy(&bigbuf[w_place], local_buf, amount);
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local_buf = local_buf + amount;
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w_place = w_place + amount;
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tmp_nbyte = tmp_nbyte - amount;
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if (w_place == BUF_SIZE) {
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if (write(filedes, bigbuf, BUF_SIZE) != BUF_SIZE) {
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return(-1);
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}
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w_place = 0;
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}
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}
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return(nbyte);
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}
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ssize_t
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get_a_line(int filedes, void *buf, size_t nbyte)
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{
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long i = 0;
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ssize_t ret_val;
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while (i < nbyte) {
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ret_val = buf_read(filedes, buf + i, 1);
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if (ret_val < 0) {
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return(ret_val);
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}
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else if (ret_val == 0) {
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return((ssize_t)i);
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}
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if (*((unsigned char *)buf + i) == '\n') {
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return(i + 1);
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}
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i++;
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}
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return((ssize_t)nbyte);
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}
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