/* Copyright (C) 1994, 1995, 1996, 1997, 1998, 1999 Aladdin Enterprises.  All rights reserved.

   This file is part of Aladdin Ghostscript.

   Aladdin Ghostscript is distributed with NO WARRANTY OF ANY KIND.  No author
   or distributor accepts any responsibility for the consequences of using it,
   or for whether it serves any particular purpose or works at all, unless he
   or she says so in writing.  Refer to the Aladdin Ghostscript Free Public
   License (the "License") for full details.

   Every copy of Aladdin Ghostscript must include a copy of the License,
   normally in a plain ASCII text file named PUBLIC.  The License grants you
   the right to copy, modify and redistribute Aladdin Ghostscript, but only
   under certain conditions described in the License.  Among other things, the
   License requires that the copyright notice and this notice be preserved on
   all copies.
 */

/*$Id: sfxfd.c $ */
/* File stream implementation using direct OS calls */
/******
 ****** NOTE: THIS FILE MAY NOT COMPILE ON NON-UNIX PLATFORMS, AND MAY
 ****** REQUIRE EDITING ON SOME UNIX PLATFORMS.
 ******/
#include "stdio_.h"		/* includes std.h */
#include "errno_.h"
#include "memory_.h"
/*
 * It's likely that you will have to edit the next line on some Unix
 * and most non-Unix platforms, since there is no standard (ANSI or
 * otherwise) for where to find these definitions.
 */
/*
 * unistd.h may declare unlink in a way that conflicts with stdio_.h if
 * const has been disabled.
 */
#define unlink unlink_
#include <unistd.h>		/* for read, write, fsync, lseek */
#include "gdebug.h"
#include "gpcheck.h"
#include "stream.h"
#include "strimpl.h"

/*
 * This is an alternate implementation of file streams.  It still uses
 * FILE * in the interface, but it uses direct OS calls for I/O.
 * It also includes workarounds for the nasty habit of System V Unix
 * of breaking out of read and write operations with EINTR, EAGAIN,
 * and/or EWOULDBLOCK "errors".
 *
 * The interface should be identical to that of sfxstdio.c.  However, in
 * order to allow both implementations to exist in the same executable, we
 * optionally use different names for sread_file, swrite_file, and
 * sappend_file (the public procedures).  See sfxboth.c.
 */
#ifndef KEEP_FILENO_API
#  define sread_fileno sread_file
#  define swrite_fileno swrite_file
#  define sappend_fileno sappend_file
#endif

/* Forward references for file stream procedures */
private int
    s_fileno_available(P2(stream *, long *)),
    s_fileno_read_seek(P2(stream *, long)),
    s_fileno_read_close(P1(stream *)),
    s_fileno_read_process(P4(stream_state *, stream_cursor_read *,
			     stream_cursor_write *, bool));
private int
    s_fileno_write_seek(P2(stream *, long)),
    s_fileno_write_flush(P1(stream *)),
    s_fileno_write_close(P1(stream *)),
    s_fileno_write_process(P4(stream_state *, stream_cursor_read *,
			      stream_cursor_write *, bool));
private int
    s_fileno_switch(P2(stream *, bool));

/* ------ File streams ------ */

/* Get the file descriptor number of a stream. */
inline private int
sfileno(const stream *s)
{
    return fileno(s->file);
}

/* Initialize a stream for reading an OS file. */
void
sread_fileno(register stream * s, FILE * file, byte * buf, uint len)
{
    static const stream_procs p = {
	s_fileno_available, s_fileno_read_seek, s_std_read_reset,
	s_std_read_flush, s_fileno_read_close, s_fileno_read_process,
	s_fileno_switch
    };
    /*
     * There is no really portable way to test seekability,
     * but this should work on most systems.
     */
    int fd = fileno(file);
    long curpos = lseek(fd, 0L, SEEK_CUR);
    bool seekable = (curpos != -1L && lseek(fd, curpos, SEEK_SET) != -1L);

    s_std_init(s, buf, len, &p,
	       (seekable ? s_mode_read + s_mode_seek : s_mode_read));
    if_debug2('s', "[s]read file=0x%lx, fd=%d\n", (ulong) file,
	      fileno(file));
    s->file = file;
    s->file_modes = s->modes;
}
/* Procedures for reading from a file */
private int
s_fileno_available(register stream * s, long *pl)
{
    int fd = sfileno(s);

    *pl = sbufavailable(s);
    if (sseekable(s)) {
	long pos, end;

	pos = lseek(fd, 0L, SEEK_CUR);
	if (pos < 0)
	    return ERRC;
	end = lseek(fd, 0L, SEEK_END);
	if (lseek(fd, pos, SEEK_SET) < 0 || end < 0)
	    return ERRC;
	*pl += end - pos;
	if (*pl == 0)
	    *pl = -1;		/* EOF */
    } else {
	if (*pl == 0)
	    *pl = -1;		/* EOF */
    }
    return 0;
}
private int
s_fileno_read_seek(register stream * s, long pos)
{
    uint end = s->srlimit - s->cbuf + 1;
    long offset = pos - s->position;

    if (offset >= 0 && offset <= end) {  /* Staying within the same buffer */
	s->srptr = s->cbuf + offset - 1;
	return 0;
    }
    if (lseek(sfileno(s), pos, SEEK_SET) < 0)
	return ERRC;
    s->srptr = s->srlimit = s->cbuf - 1;
    s->end_status = 0;
    s->position = pos;
    return 0;
}
private int
s_fileno_read_close(stream * s)
{
    FILE *file = s->file;

    if (file != 0) {
	s->file = 0;
	return (fclose(file) ? ERRC : 0);
    }
    return 0;
}

/* Initialize a stream for writing an OS file. */
void
swrite_fileno(register stream * s, FILE * file, byte * buf, uint len)
{
    static const stream_procs p = {
	s_std_noavailable, s_fileno_write_seek, s_std_write_reset,
	s_fileno_write_flush, s_fileno_write_close, s_fileno_write_process,
	s_fileno_switch
    };

    s_std_init(s, buf, len, &p,
	       (file == stdout ? s_mode_write : s_mode_write + s_mode_seek));
    if_debug2('s', "[s]write file=0x%lx, fd=%d\n", (ulong) file,
	      fileno(file));
    s->file = file;
    s->file_modes = s->modes;
}
/* Initialize for appending to an OS file. */
void
sappend_fileno(register stream * s, FILE * file, byte * buf, uint len)
{
    swrite_fileno(s, file, buf, len);
    s->modes = s_mode_write + s_mode_append;	/* no seek */
    s->file_modes = s->modes;
    s->position = lseek(fileno(file), 0L, SEEK_END);
}
/* Procedures for writing on a file */
private int
s_fileno_write_seek(stream * s, long pos)
{
    /* We must flush the buffer to reposition. */
    int code = sflush(s);

    if (code < 0)
	return code;
    if (lseek(sfileno(s), pos, SEEK_SET) < 0)
	return ERRC;
    s->position = pos;
    return 0;
}
private int
s_fileno_write_flush(register stream * s)
{
    int result = s_process_write_buf(s, false);

    discard(fsync(sfileno(s)));
    return result;
}
private int
s_fileno_write_close(register stream * s)
{
    s_process_write_buf(s, true);
    return s_fileno_read_close(s);
}

/* Define the System V interrupts that require retrying a call. */
private bool
errno_is_retry(int errn)
{
    switch (errn) {
#ifdef EINTR
    case EINTR: return true;
#endif
#if defined(EAGAIN) && (!defined(EINTR) || EAGAIN != EINTR)
    case EAGAIN: return true;
#endif
#if defined(EWOULDBLOCK) && (!defined(EINTR) || EWOULDBLOCK != EINTR) && (!defined(EAGAIN) || EWOULDBLOCK != EAGAIN)
    case EWOULDBLOCK: return true;
#endif
    default: return false;
    }
}

/* Process a buffer for a file reading stream. */
/* This is the first stream in the pipeline, so pr is irrelevant. */
private int
s_fileno_read_process(stream_state * st, stream_cursor_read * ignore_pr,
		      stream_cursor_write * pw, bool last)
{
    int nread, status;

again:
    /*
     * In the Mac MetroWerks compiler, the prototype for read incorrectly
     * declares the second argument of read as char * rather than void *.
     * Work around this here.
     */
    nread = read(sfileno((stream *)st), (void *)(pw->ptr + 1),
		 (uint)(pw->limit - pw->ptr));
    if (nread > 0) {
	pw->ptr += nread;
	status = 0;
    } else if (nread == 0)
	status = EOFC;
    else if (errno_is_retry(errno))	/* Handle System V interrupts */
	goto again;
    else
	status = ERRC;
    process_interrupts();
    return status;
}

/* Process a buffer for a file writing stream. */
/* This is the last stream in the pipeline, so pw is irrelevant. */
private int
s_fileno_write_process(stream_state * st, stream_cursor_read * pr,
		       stream_cursor_write * ignore_pw, bool last)
{
    int nwrite, status;
    uint count;

again:
    count = pr->limit - pr->ptr;
    /* Some versions of the DEC C library on AXP architectures */
    /* give an error on write if the count is zero! */
    if (count == 0) {
	process_interrupts();
	return 0;
    }
    /* See above regarding the Mac MetroWorks compiler. */
    nwrite = write(sfileno((stream *)st), (const void *)(pr->ptr + 1), count);
    if (nwrite >= 0) {
	pr->ptr += nwrite;
	status = 0;
    } else if (errno_is_retry(errno))	/* Handle System V interrupts */
	goto again;
    else
	status = ERRC;
    process_interrupts();
    return status;
}

/* Switch a file stream to reading or writing. */
private int
s_fileno_switch(stream * s, bool writing)
{
    uint modes = s->file_modes;
    int fd = sfileno(s);
    long pos;

    if (writing) {
	if (!(s->file_modes & s_mode_write))
	    return ERRC;
	pos = stell(s);
	if_debug2('s', "[s]switch 0x%lx to write at %ld\n",
		  (ulong) s, pos);
	lseek(fd, pos, SEEK_SET);	/* pacify OS */
	if (modes & s_mode_append) {
	    sappend_file(s, s->file, s->cbuf, s->cbsize);  /* sets position */
	} else {
	    swrite_file(s, s->file, s->cbuf, s->cbsize);
	    s->position = pos;
	}
	s->modes = modes;
    } else {
	if (!(s->file_modes & s_mode_read))
	    return ERRC;
	pos = stell(s);
	if_debug2('s', "[s]switch 0x%lx to read at %ld\n",
		  (ulong) s, pos);
	if (sflush(s) < 0)
	    return ERRC;
	lseek(fd, 0L, SEEK_CUR);	/* pacify OS */
	sread_file(s, s->file, s->cbuf, s->cbsize);
	s->modes |= modes & s_mode_append;	/* don't lose append info */
	s->position = pos;
    }
    s->file_modes = modes;
    return 0;
}
