ghostscript-7.07/src/stream.c

/* Copyright (C) 1989, 2000, 2001 artofcode LLC.  All rights reserved.

  This program is free software; you can redistribute it and/or modify it
  under the terms of the GNU General Public License as published by the
  Free Software Foundation; either version 2 of the License, or (at your
  option) any later version.

  This program 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
  General Public License for more details.

  You should have received a copy of the GNU General Public License along
  with this program; if not, write to the Free Software Foundation, Inc.,
  59 Temple Place, Suite 330, Boston, MA, 02111-1307.

*/

/*$Id: stream.c,v 1.15.2.1.2.1 2003/01/17 00:49:05 giles Exp $ */
/* Stream package for Ghostscript interpreter */
#include "stdio_.h"		/* includes std.h */
#include "memory_.h"
#include "gdebug.h"
#include "gpcheck.h"
#include "stream.h"
#include "strimpl.h"

/* Forward declarations */
private int sreadbuf(P2(stream *, stream_cursor_write *));
private int swritebuf(P3(stream *, stream_cursor_read *, bool));
private void stream_compact(P2(stream *, bool));

/* Structure types for allocating streams. */
public_st_stream();
public_st_stream_state();	/* default */
/* GC procedures */
private
ENUM_PTRS_WITH(stream_enum_ptrs, stream *st) return 0;
case 0:
if (st->foreign)
    ENUM_RETURN(NULL);
else if (st->cbuf_string.data != 0)
    ENUM_RETURN_STRING_PTR(stream, cbuf_string);
else
    ENUM_RETURN(st->cbuf);
ENUM_PTR3(1, stream, strm, prev, next);
ENUM_PTR(4, stream, state);
case 5: return ENUM_CONST_STRING(&st->file_name);
ENUM_PTRS_END
private RELOC_PTRS_WITH(stream_reloc_ptrs, stream *st)
{
    byte *cbuf_old = st->cbuf;

    if (cbuf_old != 0 && !st->foreign) {
	long reloc;

	if (st->cbuf_string.data != 0) {
	    RELOC_STRING_VAR(st->cbuf_string);
	    st->cbuf = st->cbuf_string.data;
	} else
	    RELOC_VAR(st->cbuf);
	reloc = cbuf_old - st->cbuf;
	/* Relocate the other buffer pointers. */
	st->srptr -= reloc;
	st->srlimit -= reloc;	/* same as swptr */
	st->swlimit -= reloc;
    }
    RELOC_VAR(st->strm);
    RELOC_VAR(st->prev);
    RELOC_VAR(st->next);
    RELOC_VAR(st->state);
    RELOC_CONST_STRING_VAR(st->file_name);
}
RELOC_PTRS_END
/* Finalize a stream by closing it. */
/* We only do this for file streams, because other kinds of streams */
/* may attempt to free storage when closing. */
private void
stream_finalize(void *vptr)
{
    stream *const st = vptr;

    if_debug2('u', "[u]%s 0x%lx\n",
	      (!s_is_valid(st) ? "already closed:" :
	       st->is_temp ? "is_temp set:" :
	       st->file == 0 ? "not file:" :
	       "closing file:"), (ulong) st);
    if (s_is_valid(st) && !st->is_temp && st->file != 0) {
	/* Prevent any attempt to free the buffer. */
	st->cbuf = 0;
	st->cbuf_string.data = 0;
	sclose(st);		/* ignore errors */
    }
}

/* Dummy template for streams that don't have a separate state. */
private const stream_template s_no_template = {
    &st_stream_state, 0, 0, 1, 1, 0
};

/* ------ Generic procedures ------ */

/* Allocate a stream and initialize it minimally. */
void
s_init(stream *s, gs_memory_t * mem)
{
    s->memory = mem;
    s->report_error = s_no_report_error;
    s->min_left = 0;
    s->error_string[0] = 0;
    s->prev = s->next = 0;	/* clean for GC */
    s->file_name.data = 0;	/* ibid. */
    s->file_name.size = 0;
    s->close_strm = false;	/* default */
    s->close_at_eod = true;	/* default */
}
stream *
s_alloc(gs_memory_t * mem, client_name_t cname)
{
    stream *s = gs_alloc_struct(mem, stream, &st_stream, cname);

    if_debug2('s', "[s]alloc(%s) = 0x%lx\n",
	      client_name_string(cname), (ulong) s);
    if (s == 0)
	return 0;
    s_init(s, mem);
    return s;
}

/* Allocate a stream state and initialize it minimally. */
void
s_init_state(stream_state *st, const stream_template *template,
	     gs_memory_t *mem)
{
    st->template = template;
    st->memory = mem;
    st->report_error = s_no_report_error;
    st->min_left = 0;
}
stream_state *
s_alloc_state(gs_memory_t * mem, gs_memory_type_ptr_t stype,
	      client_name_t cname)
{
    stream_state *st = gs_alloc_struct(mem, stream_state, stype, cname);

    if_debug3('s', "[s]alloc_state %s(%s) = 0x%lx\n",
	      client_name_string(cname),
	      client_name_string(stype->sname),
	      (ulong) st);
    if (st)
	s_init_state(st, NULL, mem);
    return st;
}

/* Standard stream initialization */
void
s_std_init(register stream * s, byte * ptr, uint len, const stream_procs * pp,
	   int modes)
{
    s->template = &s_no_template;
    s->cbuf = ptr;
    s->srptr = s->srlimit = s->swptr = ptr - 1;
    s->swlimit = ptr - 1 + len;
    s->end_status = 0;
    s->foreign = 0;
    s->modes = modes;
    s->cbuf_string.data = 0;
    s->position = 0;
    s->bsize = s->cbsize = len;
    s->strm = 0;		/* not a filter */
    s->is_temp = 0;
    s->procs = *pp;
    s->state = (stream_state *) s;	/* hack to avoid separate state */
    s->file = 0;
    s->file_name.data = 0;	/* in case stream is on stack */
    s->file_name.size = 0;
    if_debug4('s', "[s]init 0x%lx, buf=0x%lx, len=%u, modes=%d\n",
	      (ulong) s, (ulong) ptr, len, modes);
}


/* Set the file name of a stream, copying the name. */
/* Return <0 if the copy could not be allocated. */
int
ssetfilename(stream *s, const byte *data, uint size)
{
    byte *str =
	(s->file_name.data == 0 ?
	 gs_alloc_string(s->memory, size + 1, "ssetfilename") :
	 gs_resize_string(s->memory,
			  (byte *)s->file_name.data,	/* break const */
			  s->file_name.size,
			  size + 1, "ssetfilename"));

    if (str == 0)
	return -1;
    memcpy(str, data, size);
    str[size] = 0;
    s->file_name.data = str;
    s->file_name.size = size + 1;
    return 0;
}

/* Return the file name of a stream, if any. */
/* There is a guaranteed 0 byte after the string. */
int
sfilename(stream *s, gs_const_string *pfname)
{
    pfname->data = s->file_name.data;
    if (pfname->data == 0) {
	pfname->size = 0;
	return -1;
    }
    pfname->size = s->file_name.size - 1; /* omit terminator */
    return 0;
}

/* Implement a stream procedure as a no-op. */
int
s_std_null(stream * s)
{
    return 0;
}

/* Discard the contents of the buffer when reading. */
void
s_std_read_reset(stream * s)
{
    s->srptr = s->srlimit = s->cbuf - 1;
}

/* Discard the contents of the buffer when writing. */
void
s_std_write_reset(stream * s)
{
    s->swptr = s->cbuf - 1;
}

/* Flush data to end-of-file when reading. */
int
s_std_read_flush(stream * s)
{
    while (1) {
	s->srptr = s->srlimit = s->cbuf - 1;
	if (s->end_status)
	    break;
	s_process_read_buf(s);
    }
    return (s->end_status == EOFC ? 0 : s->end_status);
}

/* Flush buffered data when writing. */
int
s_std_write_flush(stream * s)
{
    return s_process_write_buf(s, false);
}

/* Indicate that the number of available input bytes is unknown. */
int
s_std_noavailable(stream * s, long *pl)
{
    *pl = -1;
    return 0;
}

/* Indicate an error when asked to seek. */
int
s_std_noseek(stream * s, long pos)
{
    return ERRC;
}

/* Standard stream closing. */
int
s_std_close(stream * s)
{
    return 0;
}

/* Standard stream mode switching. */
int
s_std_switch_mode(stream * s, bool writing)
{
    return ERRC;
}

/* Standard stream finalization.  Disable the stream. */
void
s_disable(register stream * s)
{
    s->cbuf = 0;
    s->bsize = 0;
    s->end_status = EOFC;
    s->modes = 0;
    s->cbuf_string.data = 0;
    /* The pointers in the next two statements should really be */
    /* initialized to ([const] byte *)0 - 1, but some very picky */
    /* compilers complain about this. */
    s->cursor.r.ptr = s->cursor.r.limit = 0;
    s->cursor.w.limit = 0;
    s->procs.close = s_std_null;
    /* Clear pointers for GC */
    s->strm = 0;
    s->state = (stream_state *) s;
    s->template = &s_no_template;
    /* Free the file name. */
    if (s->file_name.data) {
	gs_free_const_string(s->memory, s->file_name.data, s->file_name.size,
			     "s_disable(file_name)");
	s->file_name.data = 0;
	s->file_name.size = 0;
    }
    /****** SHOULD DO MORE THAN THIS ******/
    if_debug1('s', "[s]disable 0x%lx\n", (ulong) s);
}

/* Implement flushing for encoding filters. */
int
s_filter_write_flush(register stream * s)
{
    int status = s_process_write_buf(s, false);

    if (status != 0)
	return status;
    return sflush(s->strm);
}

/* Close a filter.  If this is an encoding filter, flush it first. */
int
s_filter_close(register stream * s)
{
    if (s_is_writing(s)) {
	int status = s_process_write_buf(s, true);

	if (status != 0 && status != EOFC)
	    return status;
    }
    return s_std_close(s);
}

/* Disregard a stream error message. */
int
s_no_report_error(stream_state * st, const char *str)
{
    return 0;
}

/* Generic procedure structures for filters. */

const stream_procs s_filter_read_procs = {
    s_std_noavailable, s_std_noseek, s_std_read_reset,
    s_std_read_flush, s_filter_close
};

const stream_procs s_filter_write_procs = {
    s_std_noavailable, s_std_noseek, s_std_write_reset,
    s_filter_write_flush, s_filter_close
};

/* ------ Implementation-independent procedures ------ */

/* Store the amount of available data in a(n input) stream. */
int
savailable(stream * s, long *pl)
{
    return (*(s)->procs.available) (s, pl);
}

/* Return the current position of a stream. */
long
stell(stream * s)
{
    /*
     * The stream might have been closed, but the position
     * is still meaningful in this case.
     */
    const byte *ptr = (s_is_writing(s) ? s->swptr : s->srptr);

    return (ptr == 0 ? 0 : ptr + 1 - s->cbuf) + s->position;
}

/* Set the position of a stream. */
int
spseek(stream * s, long pos)
{
    if_debug3('s', "[s]seek 0x%lx to %ld, position was %ld\n",
	      (ulong) s, pos, stell(s));
    return (*(s)->procs.seek) (s, pos);
}

/* Switch a stream to read or write mode. */
/* Return 0 or ERRC. */
int
sswitch(register stream * s, bool writing)
{
    if (s->procs.switch_mode == 0)
	return ERRC;
    return (*s->procs.switch_mode) (s, writing);
}

/* Close a stream, disabling it if successful. */
/* (The stream may already be closed.) */
int
sclose(register stream * s)
{
    stream_state *st;
    int code = (*s->procs.close) (s);

    if (code < 0)
	return code;
    st = s->state;
    if (st != 0) {
	stream_proc_release((*release)) = st->template->release;
	if (release != 0)
	    (*release) (st);
	if (st != (stream_state *) s && st->memory != 0)
	    gs_free_object(st->memory, st, "s_std_close");
	s->state = (stream_state *) s;
    }
    s_disable(s);
    return code;
}

/*
 * Implement sgetc when the buffer may be empty.  If the buffer really is
 * empty, refill it and then read a byte.  Note that filters must read one
 * byte ahead, so that they can close immediately after the client reads the
 * last data byte if the next thing is an EOD.
 */
int
spgetcc(register stream * s, bool close_at_eod)
{
    int status, left;
    int min_left = sbuf_min_left(s);

    while (status = s->end_status,
	   left = s->srlimit - s->srptr,
	   left <= min_left && status >= 0
	)
	s_process_read_buf(s);
    if (left <= min_left &&
	(left == 0 || (status != EOFC && status != ERRC))
	) {
	/* Compact the stream so stell will return the right result. */
	stream_compact(s, true);
	if (status == EOFC && close_at_eod && s->close_at_eod) {
	    status = sclose(s);
	    if (status == 0)
		status = EOFC;
	    s->end_status = status;
	}
	return status;
    }
    return *++(s->srptr);
}

/* Implementing sputc when the buffer is full, */
/* by flushing the buffer and then writing the byte. */
int
spputc(register stream * s, byte b)
{
    for (;;) {
	if (s->end_status)
	    return s->end_status;
	if (!sendwp(s)) {
	    *++(s->swptr) = b;
	    return b;
	}
	s_process_write_buf(s, false);
    }
}

/* Push back a character onto a (read) stream. */
/* The character must be the same as the last one read. */
/* Return 0 on success, ERRC on failure. */
int
sungetc(register stream * s, byte c)
{
    if (!s_is_reading(s) || s->srptr < s->cbuf || *(s->srptr) != c)
	return ERRC;
    s->srptr--;
    return 0;
}

/* Get a string from a stream. */
/* Return 0 if the string was filled, or an exception status. */
int
sgets(stream * s, byte * buf, uint nmax, uint * pn)
{
    stream_cursor_write cw;
    int status = 0;
    int min_left = sbuf_min_left(s);

    cw.ptr = buf - 1;
    cw.limit = cw.ptr + nmax;
    while (cw.ptr < cw.limit) {
	int left;

	if ((left = s->srlimit - s->srptr) > min_left) {
	    s->srlimit -= min_left;
	    stream_move(&s->cursor.r, &cw);
	    s->srlimit += min_left;
	} else {
	    uint wanted = cw.limit - cw.ptr;
	    int c;
	    stream_state *st;

	    if (wanted >= s->bsize >> 2 &&
		(st = s->state) != 0 &&
		wanted >= st->template->min_out_size &&
		s->end_status == 0 &&
		left == 0
		) {
		byte *wptr = cw.ptr;

		cw.limit -= min_left;
		status = sreadbuf(s, &cw);
		cw.limit += min_left;
		/*
		 * We know the stream buffer is empty, so it's safe to
		 * update position.  However, we need to reset the read
		 * cursor to indicate that there is no data in the buffer.
		 */
		s->srptr = s->srlimit = s->cbuf - 1;
		s->position += cw.ptr - wptr;
		if (status != 1 || cw.ptr == cw.limit)
		    break;
	    }
	    c = spgetc(s);
	    if (c < 0) {
		status = c;
		break;
	    }
	    *++(cw.ptr) = c;
	}
    }
    *pn = cw.ptr + 1 - buf;
    return (status >= 0 ? 0 : status);
}

/* Write a string on a stream. */
/* Return 0 if the entire string was written, or an exception status. */
int
sputs(register stream * s, const byte * str, uint wlen, uint * pn)
{
    uint len = wlen;
    int status = s->end_status;

    if (status >= 0)
	while (len > 0) {
	    uint count = s->swlimit - s->swptr;

	    if (count > 0) {
		if (count > len)
		    count = len;
		memcpy(s->swptr + 1, str, count);
		s->swptr += count;
		str += count;
		len -= count;
	    } else {
		byte ch = *str++;

		status = sputc(s, ch);
		if (status < 0)
		    break;
		len--;
	    }
	}
    *pn = wlen - len;
    return (status >= 0 ? 0 : status);
}

/* Skip ahead a specified distance in a read stream. */
/* Return 0 or an exception code. */
/* Store the number of bytes skipped in *pskipped. */
int
spskip(register stream * s, long nskip, long *pskipped)
{
    long n = nskip;
    int min_left;

    if (nskip < 0 || !s_is_reading(s)) {
	*pskipped = 0;
	return ERRC;
    }
    if (s_can_seek(s)) {
	long pos = stell(s);
	int code = sseek(s, pos + n);

	*pskipped = stell(s) - pos;
	return code;
    }
    min_left = sbuf_min_left(s);
    while (sbufavailable(s) < n + min_left) {
	int code;

	n -= sbufavailable(s);
	s->srptr = s->srlimit;
	if (s->end_status) {
	    *pskipped = nskip - n;
	    return s->end_status;
	}
	code = sgetc(s);
	if (code < 0) {
	    *pskipped = nskip - n;
	    return code;
	}
	--n;
    }
    /* Note that if min_left > 0, n < 0 is possible; this is harmless. */
    s->srptr += n;
    *pskipped = nskip;
    return 0;
}

/* Read a line from a stream.  See srdline.h for the specification. */
int
sreadline(stream *s_in, stream *s_out, void *readline_data,
	  gs_const_string *prompt, gs_string * buf,
	  gs_memory_t * bufmem, uint * pcount, bool *pin_eol,
	  bool (*is_stdin)(P1(const stream *)))
{
    uint count = *pcount;

    /* Most systems define \n as 0xa and \r as 0xd; however, */
    /* OS-9 has \n == \r == 0xd and \l == 0xa.  The following */
    /* code works properly regardless of environment. */
#if '\n' == '\r'
#  define LF 0xa
#else
#  define LF '\n'
#endif

    if (count == 0 && s_out && prompt) {
	uint ignore_n;
	int ch = sputs(s_out, prompt->data, prompt->size, &ignore_n);

	if (ch < 0)
	    return ch;
    }

top:
    if (*pin_eol) {
	/*
	 * We're in the middle of checking for a two-character
	 * end-of-line sequence.  If we get an EOF here, stop, but
	 * don't signal EOF now; wait till the next read.
	 */
	int ch = spgetcc(s_in, false);

	if (ch == EOFC) {
	    *pin_eol = false;
	    return 0;
	} else if (ch < 0)
	    return ch;
	else if (ch != LF)
	    sputback(s_in);
	*pin_eol = false;
	return 0;
    }
    for (;;) {
	int ch = sgetc(s_in);

	if (ch < 0) {		/* EOF or exception */
	    *pcount = count;
	    return ch;
	}
	switch (ch) {
	    case '\r':
		{
#if '\n' == '\r'		/* OS-9 or similar */
		    if (!is_stdin(s_in))
#endif
		    {
			*pcount = count;
			*pin_eol = true;
			goto top;
		    }
		}
		/* falls through */
	    case LF:
#undef LF
		*pcount = count;
		return 0;
	}
	if (count >= buf->size) {	/* filled the string */
	    if (!bufmem) {
		sputback(s_in);
		*pcount = count;
		return 1;
	    }
	    {
		uint nsize = count + max(count, 20);
		byte *ndata = gs_resize_string(bufmem, buf->data, buf->size,
					       nsize, "sreadline(buffer)");

		if (ndata == 0)
		    return ERRC; /* no better choice */
		buf->data = ndata;
		buf->size = nsize;
	    }
	}
	buf->data[count++] = ch;
    }
    /*return 0; *//* not reached */
}

/* ------ Utilities ------ */

/*
 * Attempt to refill the buffer of a read stream.  Only call this if the
 * end_status is not EOFC, and if the buffer is (nearly) empty.
 */
int
s_process_read_buf(stream * s)
{
    int status;

    stream_compact(s, false);
    status = sreadbuf(s, &s->cursor.w);
    s->end_status = (status >= 0 ? 0 : status);
    return 0;
}

/*
 * Attempt to empty the buffer of a write stream.  Only call this if the
 * end_status is not EOFC.
 */
int
s_process_write_buf(stream * s, bool last)
{
    int status = swritebuf(s, &s->cursor.r, last);

    stream_compact(s, false);
    return (status >= 0 ? 0 : status);
}

/* Move forward or backward in a pipeline.  We temporarily reverse */
/* the direction of the pointers while doing this. */
/* (Cf the Deutsch-Schorr-Waite graph marking algorithm.) */
#define MOVE_BACK(curr, prev)\
  BEGIN\
    stream *back = prev->strm;\
    prev->strm = curr; curr = prev; prev = back;\
  END
#define MOVE_AHEAD(curr, prev)\
  BEGIN\
    stream *ahead = curr->strm;\
    curr->strm = prev; prev = curr; curr = ahead;\
  END

/*
 * Read from a stream pipeline.  Update end_status for all streams that were
 * actually touched.  Return the status from the outermost stream: this is
 * normally the same as s->end_status, except that if s->procs.process
 * returned 1, sreadbuf sets s->end_status to 0, but returns 1.
 */
private int
sreadbuf(stream * s, stream_cursor_write * pbuf)
{
    stream *prev = 0;
    stream *curr = s;
    int status;

    for (;;) {
	stream *strm;
	stream_cursor_write *pw;
	byte *oldpos;

	for (;;) {		/* Descend into the recursion. */
	    stream_cursor_read cr;
	    stream_cursor_read *pr;
	    int left;
	    bool eof;

	    strm = curr->strm;
	    if (strm == 0) {
		cr.ptr = 0, cr.limit = 0;
		pr = &cr;
		left = 0;
		eof = false;
	    } else {
		pr = &strm->cursor.r;
		left = sbuf_min_left(strm);
		left = min(left, pr->limit - pr->ptr);
		pr->limit -= left;
		eof = strm->end_status == EOFC;
	    }
	    pw = (prev == 0 ? pbuf : &curr->cursor.w);
	    if_debug4('s', "[s]read process 0x%lx, nr=%u, nw=%u, eof=%d\n",
		      (ulong) curr, (uint) (pr->limit - pr->ptr),
		      (uint) (pw->limit - pw->ptr), eof);
	    oldpos = pw->ptr;
	    status = (*curr->procs.process) (curr->state, pr, pw, eof);
	    pr->limit += left;
	    if_debug4('s', "[s]after read 0x%lx, nr=%u, nw=%u, status=%d\n",
		      (ulong) curr, (uint) (pr->limit - pr->ptr),
		      (uint) (pw->limit - pw->ptr), status);
	    if (strm == 0 || status != 0)
		break;
	    if (strm->end_status < 0) {
		if (strm->end_status != EOFC || pw->ptr == oldpos)
		    status = strm->end_status;
		break;
	    }
	    MOVE_AHEAD(curr, prev);
	    stream_compact(curr, false);
	}
	/* If curr reached EOD and is a filter stream, close it. */
	if (strm != 0 && status == EOFC &&
	    curr->cursor.r.ptr >= curr->cursor.r.limit &&
	    curr->close_at_eod
	    ) {
	    int cstat = sclose(curr);

	    if (cstat != 0)
		status = cstat;
	}
	/* Unwind from the recursion. */
	curr->end_status = (status >= 0 ? 0 : status);
	if (prev == 0)
	    return status;
	MOVE_BACK(curr, prev);
    }
}

/* Write to a pipeline. */
private int
swritebuf(stream * s, stream_cursor_read * pbuf, bool last)
{
    stream *prev = 0;
    stream *curr = s;
    int depth = 0;		/* # of non-temp streams before curr */
    int status;

    /*
     * The handling of EOFC is a little tricky.  There are two
     * invariants that keep it straight:
     *      - We only pass last = true to a stream if either it is
     * the first stream in the pipeline, or it is a temporary stream
     * below the first stream and the stream immediately above it has
     * end_status = EOFC.
     */
    for (;;) {
	for (;;) {
	    /* Move ahead in the pipeline. */
	    stream *strm = curr->strm;
	    stream_cursor_write cw;
	    stream_cursor_read *pr;
	    stream_cursor_write *pw;

	    /*
	     * We only want to set the last/end flag for
	     * the top-level stream and any temporary streams
	     * immediately below it.
	     */
	    bool end = last &&
		(prev == 0 ||
		 (depth <= 1 && prev->end_status == EOFC));

	    if (strm == 0)
		cw.ptr = 0, cw.limit = 0, pw = &cw;
	    else
		pw = &strm->cursor.w;
	    if (prev == 0)
		pr = pbuf;
	    else
		pr = &curr->cursor.r;
	    if_debug5('s',
		      "[s]write process 0x%lx(%s), nr=%u, nw=%u, end=%d\n",
		      (ulong)curr,
		      gs_struct_type_name(curr->state->template->stype),
		      (uint)(pr->limit - pr->ptr),
		      (uint)(pw->limit - pw->ptr), end);
	    status = curr->end_status;
	    if (status >= 0) {
		status = (*curr->procs.process)(curr->state, pr, pw, end);
		if_debug5('s',
			  "[s]after write 0x%lx, nr=%u, nw=%u, end=%d, status=%d\n",
			  (ulong) curr, (uint) (pr->limit - pr->ptr),
			  (uint) (pw->limit - pw->ptr), end, status);
		if (status == 0 && end)
		    status = EOFC;
		if (status == EOFC || status == ERRC)
		    curr->end_status = status;
	    }
	    if (strm == 0 || (status < 0 && status != EOFC))
		break;
	    if (status != 1) {
		/*
		 * Keep going if we are closing a filter with a sub-stream.
		 * We know status == 0 or EOFC.
		 */
		if (!end || !strm->is_temp)
		    break;
	    }
	    status = strm->end_status;
	    if (status < 0)
		break;
	    if (!curr->is_temp)
		++depth;
	    if_debug1('s', "[s]moving ahead, depth = %d\n", depth);
	    MOVE_AHEAD(curr, prev);
	    stream_compact(curr, false);
	}
	/* Move back in the pipeline. */
	curr->end_status = (status >= 0 ? 0 : status);
	if (status < 0 || prev == 0) {
	    /*
	     * All streams up to here were called with last = true
	     * and returned 0 or EOFC (so their end_status is now EOFC):
	     * finish unwinding and then return.  Change the status of
	     * the prior streams to ERRC if the new status is ERRC,
	     * otherwise leave it alone.
	     */
	    while (prev) {
		if_debug0('s', "[s]unwinding\n");
		MOVE_BACK(curr, prev);
		if (status >= 0)
		    curr->end_status = 0;
		else if (status == ERRC)
		    curr->end_status = ERRC;
	    }
	    return status;
	}
	MOVE_BACK(curr, prev);
	if (!curr->is_temp)
	    --depth;
	if_debug1('s', "[s]moving back, depth = %d\n", depth);
    }
}

/* Move as much data as possible from one buffer to another. */
/* Return 0 if the input became empty, 1 if the output became full. */
int
stream_move(stream_cursor_read * pr, stream_cursor_write * pw)
{
    uint rcount = pr->limit - pr->ptr;
    uint wcount = pw->limit - pw->ptr;
    uint count;
    int status;

    if (rcount <= wcount)
	count = rcount, status = 0;
    else
	count = wcount, status = 1;
    memmove(pw->ptr + 1, pr->ptr + 1, count);
    pr->ptr += count;
    pw->ptr += count;
    return status;
}

/* If possible, compact the information in a stream buffer to the bottom. */
private void
stream_compact(stream * s, bool always)
{
    if (s->cursor.r.ptr >= s->cbuf && (always || s->end_status >= 0)) {
	uint dist = s->cursor.r.ptr + 1 - s->cbuf;

	memmove(s->cbuf, s->cursor.r.ptr + 1,
		(uint) (s->cursor.r.limit - s->cursor.r.ptr));
	s->cursor.r.ptr = s->cbuf - 1;
	s->cursor.r.limit -= dist;	/* same as w.ptr */
	s->position += dist;
    }
}

/* ------ String streams ------ */

/* String stream procedures */
private int
    s_string_available(P2(stream *, long *)),
    s_string_read_seek(P2(stream *, long)),
    s_string_write_seek(P2(stream *, long)),
    s_string_read_process(P4(stream_state *, stream_cursor_read *,
			     stream_cursor_write *, bool)),
    s_string_write_process(P4(stream_state *, stream_cursor_read *,
			      stream_cursor_write *, bool));

/* Initialize a stream for reading a string. */
void
sread_string(register stream *s, const byte *ptr, uint len)
{
    static const stream_procs p = {
	 s_string_available, s_string_read_seek, s_std_read_reset,
	 s_std_read_flush, s_std_null, s_string_read_process
    };

    s_std_init(s, (byte *)ptr, len, &p, s_mode_read + s_mode_seek);
    s->cbuf_string.data = (byte *)ptr;
    s->cbuf_string.size = len;
    s->end_status = EOFC;
    s->srlimit = s->swlimit;
}
/* Initialize a reusable stream for reading a string. */
private void
s_string_reusable_reset(stream *s)
{
    s->srptr = s->cbuf - 1;	/* just reset to the beginning */
    s->srlimit = s->srptr + s->bsize;  /* might have gotten reset */
}
private int
s_string_reusable_flush(stream *s)
{
    s->srptr = s->srlimit = s->cbuf + s->bsize - 1;  /* just set to the end */
    return 0;
}
void
sread_string_reusable(stream *s, const byte *ptr, uint len)
{
    static const stream_procs p = {
	 s_string_available, s_string_read_seek, s_string_reusable_reset,
	 s_string_reusable_flush, s_std_null, s_string_read_process
    };

    sread_string(s, ptr, len);
    s->procs = p;
    s->close_at_eod = false;
}

/* Return the number of available bytes when reading from a string. */
private int
s_string_available(stream *s, long *pl)
{
    *pl = sbufavailable(s);
    if (*pl == 0 && s->close_at_eod)	/* EOF */
	*pl = -1;
    return 0;
}

/* Seek in a string being read.  Return 0 if OK, ERRC if not. */
private int
s_string_read_seek(register stream * s, long pos)
{
    if (pos < 0 || pos > s->bsize)
	return ERRC;
    s->srptr = s->cbuf + pos - 1;
    /* We might be seeking after a reusable string reached EOF. */
    s->srlimit = s->cbuf + s->bsize - 1;
    return 0;
}

/* Initialize a stream for writing a string. */
void
swrite_string(register stream * s, byte * ptr, uint len)
{
    static const stream_procs p = {
	s_std_noavailable, s_string_write_seek, s_std_write_reset,
	s_std_null, s_std_null, s_string_write_process
    };

    s_std_init(s, ptr, len, &p, s_mode_write + s_mode_seek);
    s->cbuf_string.data = ptr;
    s->cbuf_string.size = len;
}

/* Seek in a string being written.  Return 0 if OK, ERRC if not. */
private int
s_string_write_seek(register stream * s, long pos)
{
    if (pos < 0 || pos > s->bsize)
	return ERRC;
    s->swptr = s->cbuf + pos - 1;
    return 0;
}

/* Since we initialize the input buffer of a string read stream */
/* to contain all of the data in the string, if we are ever asked */
/* to refill the buffer, we should signal EOF. */
private int
s_string_read_process(stream_state * st, stream_cursor_read * ignore_pr,
		      stream_cursor_write * pw, bool last)
{
    return EOFC;
}
/* Similarly, if we are ever asked to empty the buffer, it means that */
/* there has been an overrun (unless we are closing the stream). */
private int
s_string_write_process(stream_state * st, stream_cursor_read * pr,
		       stream_cursor_write * ignore_pw, bool last)
{
    return (last ? EOFC : ERRC);
}

/* ------ Position-tracking stream ------ */

private int
    s_write_position_process(P4(stream_state *, stream_cursor_read *,
				stream_cursor_write *, bool));

/* Set up a write stream that just keeps track of the position. */
void
swrite_position_only(stream *s)
{
    static byte discard_buf[50];	/* size is arbitrary */

    swrite_string(s, discard_buf, sizeof(discard_buf));
    s->procs.process = s_write_position_process;
}

private int
s_write_position_process(stream_state * st, stream_cursor_read * pr,
			 stream_cursor_write * ignore_pw, bool last)
{
    pr->ptr = pr->limit;	/* discard data */
    return 0;
}

/* ------ Filter pipelines ------ */

/*
 * Add a filter to an output pipeline.  The client must have allocated the
 * stream state, if any, using the given allocator.  For s_init_filter, the
 * client must have called s_init and s_init_state.
 */
int
s_init_filter(stream *fs, stream_state *fss, byte *buf, uint bsize,
	      stream *target)
{
    const stream_template *template = fss->template;

    if (bsize < template->min_in_size)
	return ERRC;
    s_std_init(fs, buf, bsize, &s_filter_write_procs, s_mode_write);
    fs->procs.process = template->process;
    fs->state = fss;
    if (template->init)
	(template->init)(fss);
    fs->strm = target;
    return 0;
}
stream *
s_add_filter(stream **ps, const stream_template *template,
	     stream_state *ss, gs_memory_t *mem)
{
    stream *es;
    stream_state *ess;
    uint bsize = max(template->min_in_size, 256);	/* arbitrary */
    byte *buf;

    /*
     * Ensure enough buffering.  This may require adding an additional
     * stream.
     */
    if (bsize > (*ps)->bsize && template->process != s_NullE_template.process) {
	stream_template null_template;

	null_template = s_NullE_template;
	null_template.min_in_size = bsize;
	if (s_add_filter(ps, &null_template, NULL, mem) == 0)
	    return 0;
    }
    es = s_alloc(mem, "s_add_filter(stream)");
    buf = gs_alloc_bytes(mem, bsize, "s_add_filter(buf)");
    if (es == 0 || buf == 0) {
	gs_free_object(mem, buf, "s_add_filter(buf)");
	gs_free_object(mem, es, "s_add_filter(stream)");
	return 0;
    }
    ess = (ss == 0 ? (stream_state *)es : ss);
    ess->template = template;
    ess->memory = mem;
    es->memory = mem;
    s_init_filter(es, ess, buf, bsize, *ps);
    *ps = es;
    return es;
}

/*
 * Close the filters in a pipeline, up to a given target stream, freeing
 * their buffers and state structures.
 */
int
s_close_filters(stream **ps, stream *target)
{
    while (*ps != target) {
	stream *s = *ps;
	gs_memory_t *mem = s->state->memory;
	byte *sbuf = s->cbuf;
	stream *next = s->strm;
	int status = sclose(s);
	stream_state *ss = s->state; /* sclose may set this to s */

	if (status < 0)
	    return status;
	if (mem) {
	    gs_free_object(mem, sbuf, "s_close_filters(buf)");
	    gs_free_object(mem, s, "s_close_filters(stream)");
	    if (ss != (stream_state *)s)
		gs_free_object(mem, ss, "s_close_filters(state)");
	}
	*ps = next;
    }
    return 0;
}

/* ------ NullEncode/Decode ------ */

/* Process a buffer */
private int
s_Null_process(stream_state * st, stream_cursor_read * pr,
	       stream_cursor_write * pw, bool last)
{
    return stream_move(pr, pw);
}

/* Stream template */
const stream_template s_NullE_template = {
    &st_stream_state, NULL, s_Null_process, 1, 1
};
const stream_template s_NullD_template = {
    &st_stream_state, NULL, s_Null_process, 1, 1
};