/*	$OpenBSD: cread.c,v 1.4 1997/02/06 22:57:03 downsj Exp $	*/
/*	$NetBSD: cread.c,v 1.2 1997/02/04 18:38:20 thorpej Exp $	*/

/*
 * Copyright (c) 1996
 *	Matthias Drochner.  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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed for the NetBSD Project
 *	by Matthias Drochner.
 * 4. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 *
 */

/* support for compressed bootfiles
 (only read)
 replaces open(), close(), read(), lseek().
 original libsa open(), close(), read(), lseek() are called
 as oopen(), oclose(), oread() resp. olseek().
 compression parts stripped from zlib:gzio.c
 */

/* gzio.c -- IO on .gz files
 * Copyright (C) 1995-1996 Jean-loup Gailly.
 * For conditions of distribution and use, see copyright notice in zlib.h
 */

#include "stand.h"
#include "../libz/zlib.h"

#define EOF (-1) /* needed by compression code */

#define zmemcpy	memcpy

#ifdef SAVE_MEMORY
#define Z_BUFSIZE 1024
#else
#define Z_BUFSIZE 4096
#endif

static int gz_magic[2] = {0x1f, 0x8b}; /* gzip magic header */

/* gzip flag byte */
#define ASCII_FLAG   0x01 /* bit 0 set: file probably ascii text */
#define HEAD_CRC     0x02 /* bit 1 set: header CRC present */
#define EXTRA_FIELD  0x04 /* bit 2 set: extra field present */
#define ORIG_NAME    0x08 /* bit 3 set: original file name present */
#define COMMENT      0x10 /* bit 4 set: file comment present */
#define RESERVED     0xE0 /* bits 5..7: reserved */

static struct sd {
  z_stream stream;
  int      z_err;   /* error code for last stream operation */
  int      z_eof;   /* set if end of input file */
  int fd;
  unsigned char     *inbuf;  /* input buffer */
  unsigned long    crc;     /* crc32 of uncompressed data */
  int      transparent; /* 1 if input file is not a .gz file */
} *ss[SOPEN_MAX];

/*
 * compression utilities
 */

void *zcalloc (opaque, items, size)
void *opaque;
unsigned items;
unsigned size;
{
  return(alloc(items * size));
}

void  zcfree (opaque, ptr)
void *opaque;
void *ptr;
{
  free(ptr, 0); /* XXX works only with modified allocator */
}

static int get_byte(s)
    struct sd *s;
{
    if (s->z_eof) return EOF;
    if (s->stream.avail_in == 0) {
	errno = 0;
	s->stream.avail_in = oread(s->fd, s->inbuf, Z_BUFSIZE);
	if (s->stream.avail_in == 0) {
	    s->z_eof = 1;
	    if (errno) s->z_err = Z_ERRNO;
	    return EOF;
	}
	s->stream.next_in = s->inbuf;
    }
    s->stream.avail_in--;
    return *(s->stream.next_in)++;
}

static unsigned long getLong (s)
    struct sd *s;
{
    unsigned long x = (unsigned long)get_byte(s);
    int c;

    x += ((unsigned long)get_byte(s))<<8;
    x += ((unsigned long)get_byte(s))<<16;
    c = get_byte(s);
    if (c == EOF) s->z_err = Z_DATA_ERROR;
    x += ((unsigned long)c)<<24;
    return x;
}

static void check_header(s)
    struct sd *s;
{
    int method; /* method byte */
    int flags;  /* flags byte */
    unsigned int len;
    int c;

    /* Check the gzip magic header */
    for (len = 0; len < 2; len++) {
	c = get_byte(s);
	if (c != gz_magic[len]) {
	    s->transparent = 1;
	    if (c != EOF) s->stream.avail_in++, s->stream.next_in--;
	    s->z_err = s->stream.avail_in != 0 ? Z_OK : Z_STREAM_END;
	    return;
	}
    }
    method = get_byte(s);
    flags = get_byte(s);
    if (method != Z_DEFLATED || (flags & RESERVED) != 0) {
	s->z_err = Z_DATA_ERROR;
	return;
    }

    /* Discard time, xflags and OS code: */
    for (len = 0; len < 6; len++) (void)get_byte(s);

    if ((flags & EXTRA_FIELD) != 0) { /* skip the extra field */
	len  =  (unsigned int)get_byte(s);
	len += ((unsigned int)get_byte(s))<<8;
	/* len is garbage if EOF but the loop below will quit anyway */
	while (len-- != 0 && get_byte(s) != EOF) ;
    }
    if ((flags & ORIG_NAME) != 0) { /* skip the original file name */
	while ((c = get_byte(s)) != 0 && c != EOF) ;
    }
    if ((flags & COMMENT) != 0) {   /* skip the .gz file comment */
	while ((c = get_byte(s)) != 0 && c != EOF) ;
    }
    if ((flags & HEAD_CRC) != 0) {  /* skip the header crc */
	for (len = 0; len < 2; len++) (void)get_byte(s);
    }
    s->z_err = s->z_eof ? Z_DATA_ERROR : Z_OK;
}

/*
 * new open(), close(), read(), lseek()
 */

int
open(fname, mode)
	const char *fname;
	int mode;
{
	  int fd;
	  struct sd *s = 0;

	  if(((fd = oopen(fname, mode)) == -1)
	     || (mode != 0)) /* compression only for read */
	  return(fd);

	  ss[fd] = s = alloc(sizeof(struct sd));
	  if(!s) goto errout;
	  bzero(s, sizeof(struct sd));

	  if(inflateInit2(&(s->stream), -15) != Z_OK)
	      goto errout;

	  s->stream.next_in  = s->inbuf = (unsigned char*)alloc(Z_BUFSIZE);
	  if(!s->inbuf) {
	      inflateEnd(&(s->stream));
	      goto errout;
	  }

	  s->fd = fd;
	  check_header(s); /* skip the .gz header */
	  return(fd);

errout:
          if(s) free(s, sizeof(struct sd));
          oclose(fd);
	  return(-1);
}

int
close(fd)
	int fd;
{
	struct open_file *f;
        struct sd *s;

	if ((unsigned)fd >= SOPEN_MAX) {
		errno = EBADF;
		return (-1);
	}
	f = &files[fd];

	if(!(f->f_flags & F_READ))
		return(oclose(fd));

	s = ss[fd];

	inflateEnd(&(s->stream));

	free(s->inbuf, Z_BUFSIZE);
	free(s, sizeof(struct sd));

	return(oclose(fd));
}

ssize_t
read(fd, buf, len)
	int fd;
	void *buf;
	size_t len;
{
	  struct sd *s;
	  unsigned char *start = buf; /* starting point for crc computation */

	  s = ss[fd];

	  if (s->z_err == Z_DATA_ERROR || s->z_err == Z_ERRNO) return -1;
	  if (s->z_err == Z_STREAM_END) return 0;  /* EOF */

	  s->stream.next_out = buf;
	  s->stream.avail_out = len;

	  while (s->stream.avail_out != 0) {

	    if (s->transparent) {
	      /* Copy first the lookahead bytes: */
	      unsigned int n = s->stream.avail_in;
	      if (n > s->stream.avail_out) n = s->stream.avail_out;
	      if (n > 0) {
		zmemcpy(s->stream.next_out, s->stream.next_in, n);
		s->stream.next_out += n;
		s->stream.next_in   += n;
		s->stream.avail_out -= n;
		s->stream.avail_in  -= n;
	      }
	      if (s->stream.avail_out > 0) {
		s->stream.avail_out -= oread(s->fd, s->stream.next_out, s->stream.avail_out);
	      }
	      return (int)(len - s->stream.avail_out);
	    }

	    if (s->stream.avail_in == 0 && !s->z_eof) {

	      errno = 0;
	      s->stream.avail_in = oread(fd, s->inbuf, Z_BUFSIZE);
	      if (s->stream.avail_in == 0) {
		s->z_eof = 1;
		if (errno) {
		  s->z_err = Z_ERRNO;
		  break;
		}
	      }
	      s->stream.next_in = s->inbuf;
	    }
	    s->z_err = inflate(&(s->stream), Z_NO_FLUSH);

	    if (s->z_err == Z_STREAM_END) {
	      /* Check CRC and original size */
	      s->crc = crc32(s->crc, start, (unsigned int)(s->stream.next_out - start));
	      start = s->stream.next_out;

	      if (getLong(s) != s->crc || getLong(s) != s->stream.total_out) {
		s->z_err = Z_DATA_ERROR;
	      } else {
		/* Check for concatenated .gz files: */
		check_header(s);
		if (s->z_err == Z_OK) {
		  inflateReset(&(s->stream));
		  s->crc = crc32(0L, Z_NULL, 0);
		}
	      }
	    }
	    if (s->z_err != Z_OK || s->z_eof) break;
	  }
	  s->crc = crc32(s->crc, start, (unsigned int)(s->stream.next_out - start));

	  return (int)(len - s->stream.avail_out);
}

off_t
lseek(fd, offset, where)
	int fd;
	off_t offset;
	int where;
{
	    register struct open_file *f;
	    struct sd *s;

	    if ((unsigned)fd >= SOPEN_MAX) {
		errno = EBADF;
		return (-1);
	    }
	    f = &files[fd];;

	    if(!(f->f_flags & F_READ))
		return(olseek(fd, offset, where));

	    s = ss[fd];

	    if(s->transparent) {
		off_t res = olseek(fd, offset, where);
		if(res != (off_t)-1) {
		    /* make sure the lookahead buffer is invalid */
		    s->stream.avail_in = 0;
		}
		return(res);
	    }

	    switch(where) {
		case SEEK_CUR:
		    offset += s->stream.total_out;
		case SEEK_SET:

		    /* if seek backwards, simply start from
		     the beginning */
		    if(offset < s->stream.total_out) {
			off_t res;
			void *sav_inbuf;

			res = olseek(fd, 0, SEEK_SET);
			if(res == (off_t)-1)
			    return(res);
			/* ??? perhaps fallback to close / open */

			inflateEnd(&(s->stream));

			sav_inbuf = s->inbuf; /* don't allocate again */
			bzero(s, sizeof(struct sd)); /* this resets total_out to 0! */

			inflateInit2(&(s->stream), -15);
			s->stream.next_in = s->inbuf = sav_inbuf;

			s->fd = fd;
			check_header(s); /* skip the .gz header */
		    }

		    /* to seek forwards, throw away data */
		    if(offset > s->stream.total_out) {
			off_t toskip = offset - s->stream.total_out;

			while(toskip > 0) {
#define DUMMYBUFSIZE 256
			    char dummybuf[DUMMYBUFSIZE];
			    off_t len = toskip;
			    if(len > DUMMYBUFSIZE) len = DUMMYBUFSIZE;
			    if(read(fd, dummybuf, len) != len) {
				errno = EOFFSET;
				return((off_t)-1);
			    }
			    toskip -= len;
			}
		    }
#ifdef DEBUG
		    if(offset != s->stream.total_out)
			panic("lseek compressed");
#endif
		    return(offset);
		case SEEK_END:
		    errno = EOFFSET;
		    break;
		default:
		    errno = EINVAL;
	    }
	    return((off_t)-1);
}