/*

 * Copyright (c) 1983 Regents of the University of California.

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 3. Neither the name of the University nor the names of its contributors

 *    may be used to endorse or promote products derived from this software

 *    without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

 * SUCH DAMAGE.

 */

/* Simple minded read-ahead/write-behind subroutines for tftp user and

   server.  Written originally with multiple buffers in mind, but current

   implementation has two buffer logic wired in.

   Todo:  add some sort of final error check so when the write-buffer

   is finally flushed, the caller can detect if the disk filled up

   (or had an i/o error) and return a nak to the other side.

			Jim Guyton 10/85

 */

#include <sys/types.h>

#include <sys/socket.h>

#include <sys/ioctl.h>

#include <netinet/in.h>

#include <unistd.h>

#include <stdio.h>

#include "tftp.h"

struct bf {

	int counter;            /* size of data in buffer, or flag */

	char buf[PKTSIZE];      /* room for data packet */

} bfs[2];

				/* Values for bf.counter  */

#define BF_ALLOC -3             /* alloc'd but not yet filled */

#define BF_FREE  -2             /* free */

/* [-1 .. SEGSIZE] = size of data in the data buffer */

static int nextone;     /* index of next buffer to use */

static int current;     /* index of buffer in use */

			/* control flags for crlf conversions */

int newline = 0;        /* fillbuf: in middle of newline expansion */

int prevchar = -1;      /* putbuf: previous char (cr check) */

struct tftphdr *rw_init(int);

struct tftphdr *w_init() { return rw_init(0); }         /* write-behind */

struct tftphdr *r_init() { return rw_init(1); }         /* read-ahead */

/* init for either read-ahead or write-behind */

/* x is zero for write-behind, one for read-head */

struct tftphdr *rw_init(int x)

{

	newline = 0;            /* init crlf flag */

	prevchar = -1;

	bfs[0].counter =  BF_ALLOC;     /* pass out the first buffer */

	current = 0;

	bfs[1].counter = BF_FREE;

	nextone = x;                    /* ahead or behind? */

	return (struct tftphdr *)bfs[0].buf;

}

/* Have emptied current buffer by sending to net and getting ack.

   Free it and return next buffer filled with data.

 */

int readit(FILE * file, struct tftphdr **dpp, int convert)

{

	struct bf *b;

	bfs[current].counter = BF_FREE; /* free old one */

	current = !current;             /* "incr" current */

	b = &bfs[current];              /* look at new buffer */

	if (b->counter == BF_FREE)      /* if it's empty */

		read_ahead(file, convert);      /* fill it */

#if 0

	assert(b->counter != BF_FREE);  /* check */

#endif

	*dpp = (struct tftphdr *)b->buf;        /* set caller's ptr */

	return b->counter;

}

/*

 * fill the input buffer, doing ascii conversions if requested

 * conversions are  lf -> cr,lf  and cr -> cr, nul

 */

void read_ahead(FILE *file, int convert)

{

	register int i;

	register char *p;

	register int c;

	struct bf *b;

	struct tftphdr *dp;

	b = &bfs[nextone];              /* look at "next" buffer */

	if (b->counter != BF_FREE)      /* nop if not free */

		return;

	nextone = !nextone;             /* "incr" next buffer ptr */

	dp = (struct tftphdr *)b->buf;

	if (convert == 0) {

		b->counter = read(fileno(file), dp->th_data, SEGSIZE);

		return;

	}

	p = dp->th_data;

	for (i = 0 ; i < SEGSIZE; i++) {

		if (newline) {

			if (prevchar == '\n')

				c = '\n';       /* lf to cr,lf */

			else    c = '\0';       /* cr to cr,nul */

			newline = 0;

		}

		else {

			c = getc(file);

			if (c == EOF) break;

			if (c == '\n' || c == '\r') {

				prevchar = c;

				c = '\r';

				newline = 1;

			}

		}

	       *p++ = c;

	}

	b->counter = (int)(p - dp->th_data);

}

/* Update count associated with the buffer, get new buffer

   from the queue.  Calls write_behind only if next buffer not

   available.

 */

int writeit(FILE *file, struct tftphdr **dpp, int ct, int convert)

{

	bfs[current].counter = ct;      /* set size of data to write */

	current = !current;             /* switch to other buffer */

	if (bfs[current].counter != BF_FREE)     /* if not free */

		write_behind(file, convert);     /* flush it */

	bfs[current].counter = BF_ALLOC;        /* mark as alloc'd */

	*dpp =  (struct tftphdr *)bfs[current].buf;

	return ct;                      /* this is a lie of course */

}

/*

 * Output a buffer to a file, converting from netascii if requested.

 * CR,NUL -> CR  and CR,LF => LF.

 * Note spec is undefined if we get CR as last byte of file or a

 * CR followed by anything else.  In this case we leave it alone.

 */

int write_behind(FILE *file, int convert)

{

	char *buf;

	int count;

	register int ct;

	register char *p;

	register int c;                 /* current character */

	struct bf *b;

	struct tftphdr *dp;

	b = &bfs[nextone];

	if (b->counter < -1)            /* anything to flush? */

		return 0;               /* just nop if nothing to do */

	count = b->counter;             /* remember byte count */

	b->counter = BF_FREE;           /* reset flag */

	dp = (struct tftphdr *)b->buf;

	nextone = !nextone;             /* incr for next time */

	buf = dp->th_data;

	if (count <= 0) return -1;      /* nak logic? */

	if (convert == 0)

		return write(fileno(file), buf, count);

	p = buf;

	ct = count;

	while (ct--) {                  /* loop over the buffer */

	    c = *p++;                   /* pick up a character */

	    if (prevchar == '\r') {     /* if prev char was cr */

		if (c == '\n')          /* if have cr,lf then just */

		   fseek(file, -1, 1);  /* smash lf on top of the cr */

		else

		   if (c == '\0')       /* if have cr,nul then */

			goto skipit;    /* just skip over the putc */

		/* else just fall through and allow it */

	    }

	    putc(c, file);

skipit:

	    prevchar = c;

	}

	return count;

}

/* When an error has occurred, it is possible that the two sides

 * are out of synch.  Ie: that what I think is the other side's

 * response to packet N is really their response to packet N-1.

 *

 * So, to try to prevent that, we flush all the input queued up

 * for us on the network connection on our host.

 *

 * We return the number of packets we flushed (mostly for reporting

 * when trace is active).

 */

int synchnet(int f)

{

	int j = 0;

	char dummy;

	while (1) {

		if (recv(f, &dummy, 1, MSG_DONTWAIT) < 0)

			break;

		j++;

	}

	return j;

}