/* Copyright (C) 1994, 1997, 1998, 1999 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: seexec.c,v 1.4.2.1.2.1 2003/01/17 00:49:05 giles Exp $ */
/* eexec filters */
#include "stdio_.h"		/* includes std.h */
#include "strimpl.h"
#include "sfilter.h"
#include "gscrypt1.h"
#include "scanchar.h"

/* ------ eexecEncode ------ */

/* Encoding is much simpler than decoding, because we don't */
/* worry about initial characters or hex vs. binary (the client */
/* has to take care of these aspects). */

private_st_exE_state();

/* Process a buffer */
private int
s_exE_process(stream_state * st, stream_cursor_read * pr,
	      stream_cursor_write * pw, bool last)
{
    stream_exE_state *const ss = (stream_exE_state *) st;
    const byte *p = pr->ptr;
    byte *q = pw->ptr;
    uint rcount = pr->limit - p;
    uint wcount = pw->limit - q;
    uint count;
    int status;

    if (rcount <= wcount)
	count = rcount, status = 0;
    else
	count = wcount, status = 1;
    gs_type1_encrypt(q + 1, p + 1, count, (crypt_state *)&ss->cstate);
    pr->ptr += count;
    pw->ptr += count;
    return status;
}

/* Stream template */
const stream_template s_exE_template = {
    &st_exE_state, NULL, s_exE_process, 1, 2
};

/* ------ eexecDecode ------ */

private_st_exD_state();

/* Set defaults. */
private void
s_exD_set_defaults(stream_state * st)
{
    stream_exD_state *const ss = (stream_exD_state *) st;

    ss->binary = -1;		/* unknown */
    ss->lenIV = 4;
    ss->record_left = max_long;
    ss->hex_left = max_long;
    /* Clear pointers for GC */
    ss->pfb_state = 0;
}

/* Initialize the state for reading and decrypting. */
/* Decrypting streams are not positionable. */
private int
s_exD_init(stream_state * st)
{
    stream_exD_state *const ss = (stream_exD_state *) st;

    ss->odd = -1;
    ss->skip = ss->lenIV;
    return 0;
}

/* Process a buffer. */
private int
s_exD_process(stream_state * st, stream_cursor_read * pr,
	      stream_cursor_write * pw, bool last)
{
    stream_exD_state *const ss = (stream_exD_state *) st;
    const byte *p = pr->ptr;
    byte *q = pw->ptr;
    int skip = ss->skip;
    int rcount = pr->limit - p;
    int wcount = pw->limit - q;
    int status = 0;
    int count = (wcount < rcount ? (status = 1, wcount) : rcount);

    if (ss->binary < 0) {
	/*
	 * This is the very first time we're filling the buffer.
	 * Determine whether this is ASCII or hex encoding.
	 */
	const byte *const decoder = scan_char_decoder;
	int i;

        if (rcount < 8 && !last)
            return 0; 

	/*
	 * Adobe's documentation doesn't actually specify the test
	 * that eexec should use, but we believe the following
	 * gives correct answers even on certain non-conforming
	 * PostScript files encountered in practice:
	 */
	ss->binary = 0;
	for (i = min(8, rcount); i > 0; i--)
	    if (!(decoder[p[i]] <= 0xf ||
		  decoder[p[i]] == ctype_space)
		) {
		ss->binary = 1;
		if (ss->pfb_state != 0) {
		    /* Stop at the end of the .PFB binary data. */
		    ss->record_left = ss->pfb_state->record_left;
		}
		break;
	    }
    }
    if (ss->binary) {
	if (count > ss->record_left) {
	    count = ss->record_left;
	    status = 0;
	}
	/*
	 * We pause at the end of the .PFB binary data,
	 * in an attempt to keep from reading beyond the end of
	 * the encrypted data.
	 */
	if ((ss->record_left -= count) == 0)
	    ss->record_left = max_long;
	pr->ptr = p + count;
    } else {
	/*
	 * We only ignore leading whitespace, in an attempt to
	 * keep from reading beyond the end of the encrypted data;
	 * but some badly coded files require us to ignore % also.
	 */
	stream_cursor_read r;
	const byte *start;

hp:	r = *pr;
	start = r.ptr;
	if (r.limit - r.ptr > ss->hex_left)
	    r.limit = r.ptr + ss->hex_left;
	status = s_hex_process(&r, pw, &ss->odd,
			       hex_ignore_leading_whitespace);
	pr->ptr = r.ptr;
	ss->hex_left -= r.ptr - start;
	/*
	 * Check for having finished a prematurely decoded hex section of
	 * a PFB file.
	 */
	if (ss->hex_left == 0)
	    ss->binary = 1;
	count = pw->ptr - q;
	if (status < 0 && ss->odd < 0) {
	    if (count) {
		--p;
		status = 0;	/* reprocess error next time */
	    } else if (*p == '%')
		goto hp;	/* ignore % */
	}
	p = q;
    }
    if (skip >= count && skip != 0) {
	gs_type1_decrypt(q + 1, p + 1, count,
			 (crypt_state *) & ss->cstate);
	ss->skip -= count;
	count = 0;
	status = 0;
    } else {
	gs_type1_decrypt(q + 1, p + 1, skip,
			 (crypt_state *) & ss->cstate);
	count -= skip;
	gs_type1_decrypt(q + 1, p + 1 + skip, count,
			 (crypt_state *) & ss->cstate);
	ss->skip = 0;
    }
    pw->ptr = q + count;
    return status;
}

/* Stream template */
/*
 * The specification of eexec decoding requires that it never read more than
 * 512 source bytes ahead.  The only reliable way to ensure this is to
 * limit the size of the output buffer to 256.  We set it a little smaller
 * so that it will stay under the limit even after adding min_in_size
 * for a subsequent filter in a pipeline.  Note that we have to specify
 * a size of at least 128 so that filter_read won't round it up.
 */
const stream_template s_exD_template = {
    &st_exD_state, s_exD_init, s_exD_process, 8, 200,
    NULL, s_exD_set_defaults
};