/*      $NetBSD: tftpsubs.c,v 1.12 2011/09/17 15:15:46 christos Exp $   */

/*
* Copyright (c) 1983, 1993
*      The 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.
*/

#include <sys/cdefs.h>
#ifndef lint
#if 0
static char sccsid[] = "@(#)tftpsubs.c  8.1 (Berkeley) 6/6/93";
#else
__RCSID("$NetBSD: tftpsubs.c,v 1.12 2011/09/17 15:15:46 christos Exp $");
#endif
#endif /* not lint */

/* 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 <arpa/tftp.h>

#include <stdio.h>
#include <unistd.h>

#include "tftpsubs.h"

static struct bf {
       int counter;            /* size of data in buffer, or flag */
       char buf[MAXPKTSIZE];   /* 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 */
static int newline = 0;         /* fillbuf: in middle of newline expansion */
static int prevchar = -1;       /* putbuf: previous char (cr check) */

static struct tftphdr *rw_init(int);

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

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

static struct tftphdr *
rw_init(int x)                  /* init for either read-ahead or write-behind */
                               /* zero for write-behind, one for read-head */
{
       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 *)(void *)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,                     /* file opened for read */
   struct tftphdr **dpp,
   size_t amt,
   int convert)                    /* if true, convert to ascii */
{
       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, amt, convert);      /* fill it */
/*      assert(b->counter != BF_FREE);*//* check */
       *dpp = (struct tftphdr *)(void *)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,                 /* file opened for read */
   size_t amt,                 /* number of bytes to read */
   int convert)                /* if true, convert to ascii */
{
       size_t i;
       char *p;
       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 *)(void *)b->buf;

       if (convert == 0) {
               b->counter = read(fileno(file), dp->th_data, amt);
               return;
       }

       p = dp->th_data;
       for (i = 0 ; i < amt; 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 */
               if (write_behind(file, convert) == -1) /* flush it */
                       return -1;
       bfs[current].counter = BF_ALLOC;        /* mark as alloc'd */
       *dpp =  (struct tftphdr *)(void *)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;
       int ct;
       char *p;
       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 *)(void *)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, (size_t)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 */
                  (void)fseeko(file, (off_t)-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 */
           }
           if (putc(c, file) == EOF)
               return -1;
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
/*ARGSUSED*/
synchnet(
   int f,              /* socket to flush */
   size_t bsize)       /* size of buffer to sync */
{
       int i, j = 0;
       char rbuf[PKTSIZE];
       struct sockaddr_storage from;
       socklen_t fromlen;

       for (;;) {
               (void) ioctl(f, FIONREAD, &i);
               if (i) {
                       j++;
                       fromlen = sizeof from;
                       (void)recvfrom(f, rbuf, sizeof (rbuf), 0,
                           (struct sockaddr *)(void *)&from, &fromlen);
               } else {
                       return j;
               }
       }
}

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