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SRC\TPIPE.C
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1994-06-25
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/*
* This file forms part of "TKERN" - "Troy's Kernel for Windows".
*
* Copyright (C) 1994 Troy Rollo <troy@cbme.unsw.EDU.AU>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library 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
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the Free
* Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <fcntl.h>
#include <errno.h>
#include <io.h>
#include <sys/tfile.h>
#include <errno.h>
#include <memory.h>
#include <malloc.h>
#include <string.h>
extern int nError;
extern void tkern_wakeup_call(void);
#define PIPESIZE 2048
#define READER_CLOSED 1
#define WRITER_CLOSED 2
#define CLOSED (READER_CLOSED | WRITER_CLOSED)
struct pipe_struc
{
int nReadSeq;
int nWriteSeq;
int iStart;
int iEnd;
int flags;
struct pipe_struc *next;
int iBuffer;
char achBuffer[PIPESIZE + 1];
};
static struct pipe_struc *pipes = 0;
static struct pipe_struc *lastpipe = 0;
static int nSeq = 0;
static void
incseq(void)
{
nSeq = nSeq + 2;
if (nSeq > 32000)
nSeq = 0;
}
static void
remove_pipe(int nSeq)
{
struct pipe_struc **link, *entry;
for (link = &pipes; *link; link = &(*link)->next)
{
if ((*link)->nReadSeq == nSeq)
{
entry = *link;
*link = entry->next;
free(entry);
return;
}
}
}
#pragma argsused
int
pipe_open( char const *pchFile,
int nMode,
int nAccess)
{
int nResult;
struct pipe_struc *entry, **link;
if (!strcmp(pchFile, "input"))
{
if (lastpipe)
{
remove_pipe(lastpipe->nReadSeq);
lastpipe = 0;
}
link = &pipes;
while (*link)
{
if ((*link)->nReadSeq == nSeq)
{
incseq();
link = &pipes;
}
else
{
link = &(*link)->next;
}
}
entry = (struct pipe_struc *) malloc(sizeof(struct pipe_struc));
entry->nReadSeq = nSeq;
entry->nWriteSeq = nSeq + 1;
entry->next = 0;
entry->iStart = 1;
entry->iEnd = 0;
entry->flags = 0;
*link = entry;
lastpipe = entry;
incseq();
nError = 0;
return entry->nReadSeq;
}
else if (!strcmp(pchFile, "output"))
{
if (!lastpipe)
{
nError = EPIPE;
return -1;
}
entry = lastpipe;
lastpipe = 0;
nError = 0;
return entry->nWriteSeq;
}
else
{
nError = ENODEV;
return -1;
}
}
int
pipe_close( int id)
{
struct pipe_struc *entry;
for (entry = pipes; entry; entry = entry->next)
{
if (entry->nReadSeq == id)
{
entry->flags |= READER_CLOSED;
if ((entry->flags & CLOSED) == CLOSED)
remove_pipe(entry->nReadSeq);
return 0;
}
if (entry->nWriteSeq == id)
{
entry->flags |= WRITER_CLOSED;
if ((entry->flags & CLOSED) == CLOSED)
remove_pipe(entry->nReadSeq);
return 0;
}
}
nError = EFAULT;
return -1;
}
int
pipe_read( int id,
char *pchData,
int nBytes)
{
int nAvailable;
struct pipe_struc *entry;
int nTotal = 0;
if (id & 1) /* Indicates a write-side */
{
nError = EACCES;
return -1;
}
for (entry = pipes; entry; entry = entry->next)
{
if (entry->nReadSeq == id)
break;
}
if (!entry)
{
nError = EFAULT;
return -1;
}
nAvailable = entry->iEnd - entry->iStart;
if (nAvailable < 0)
nAvailable += PIPESIZE + 1;
if (!nAvailable)
{
if (entry->flags & WRITER_CLOSED)
{
return 0;
}
else
{
return FR_NOTREADY;
}
}
if (nAvailable < nBytes)
nBytes = nAvailable;
if (nBytes + entry->iStart > PIPESIZE)
{
nTotal = PIPESIZE - entry->iStart + 1;
memcpy(pchData,
entry->achBuffer + entry->iStart,
nTotal);
nBytes -= nTotal;
pchData += nTotal;
entry->iStart = 0;
}
memcpy(pchData, entry->achBuffer + entry->iStart, nBytes);
entry->iStart += nBytes;
nTotal += nBytes;
tkern_wakeup_call();
return nTotal;
}
int
pipe_write( int id,
char const *pchData,
int nBytes)
{
struct pipe_struc *entry;
int nTotal = 0;
int nAvailable;
if (!(id & 1)) /* Indicates a read-side */
{
nError = EACCES;
return -1;
}
for (entry = pipes; entry; entry = entry->next)
{
if (entry->nWriteSeq == id)
break;
}
if (!entry)
{
nError = EFAULT;
return -1;
}
if (entry->flags & READER_CLOSED)
{
/* Write on a pipe with nobody to read */
nError = EPIPE;
return -1;
}
nAvailable = entry->iStart - entry->iEnd - 1;
if (nAvailable < 0)
nAvailable = nAvailable + PIPESIZE + 1;
if (nAvailable < nBytes)
nBytes = nAvailable;
if (!nAvailable)
{
return FR_NOTREADY;
}
if (nBytes + entry->iEnd > PIPESIZE)
{
nTotal = PIPESIZE - entry->iEnd + 1;
memcpy(entry->achBuffer + entry->iEnd,
pchData,
nTotal);
nBytes -= nTotal;
pchData += nTotal;
entry->iEnd = 0;
}
memcpy(entry->achBuffer + entry->iEnd, pchData, nBytes);
entry->iEnd += nBytes;
nTotal += nBytes;
tkern_wakeup_call();
return nTotal;
}
int
pipe_ioctl(void)
{
nError = EINVAL;
return -1;
}