text: /*-
   * Copyright (c) 2003-2011 Tim Kientzle
   * 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.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``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(S) 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.
   */
  
  /*
   * This file contains the "essential" portions of the read API, that
   * is, stuff that will probably always be used by any client that
   * actually needs to read an archive.  Optional pieces have been, as
   * far as possible, separated out into separate files to avoid
   * needlessly bloating statically-linked clients.
   */
  
  #include "archive_platform.h"
  __FBSDID("$FreeBSD: head/lib/libarchive/archive_read.c 201157 2009-12-29 05:30:23Z kientzle $");
  
  #ifdef HAVE_ERRNO_H
  #include <errno.h>
  #endif
  #include <stdio.h>
  #ifdef HAVE_STDLIB_H
  #include <stdlib.h>
  #endif
  #ifdef HAVE_STRING_H
  #include <string.h>
  #endif
  #ifdef HAVE_UNISTD_H
  #include <unistd.h>
  #endif
  
  #include "archive.h"
  #include "archive_entry.h"
  #include "archive_private.h"
  #include "archive_read_private.h"
  
  #define minimum(a, b) (a < b ? a : b)
  
  static int	choose_filters(struct archive_read *);
  static int	choose_format(struct archive_read *);
  static int	close_filters(struct archive_read *);
  static struct archive_vtable *archive_read_vtable(void);
  static int64_t	_archive_filter_bytes(struct archive *, int);
  static int	_archive_filter_code(struct archive *, int);
  static const char *_archive_filter_name(struct archive *, int);
  static int  _archive_filter_count(struct archive *);
  static int	_archive_read_close(struct archive *);
  static int	_archive_read_data_block(struct archive *,
  		    const void **, size_t *, int64_t *);
  static int	_archive_read_free(struct archive *);
  static int	_archive_read_next_header(struct archive *,
  		    struct archive_entry **);
  static int	_archive_read_next_header2(struct archive *,
  		    struct archive_entry *);
  static int64_t  advance_file_pointer(struct archive_read_filter *, int64_t);
  
  static struct archive_vtable *
  archive_read_vtable(void)
  {
  	static struct archive_vtable av;
  	static int inited = 0;
  
  	if (!inited) {
  		av.archive_filter_bytes = _archive_filter_bytes;
  		av.archive_filter_code = _archive_filter_code;
  		av.archive_filter_name = _archive_filter_name;
  		av.archive_filter_count = _archive_filter_count;
  		av.archive_read_data_block = _archive_read_data_block;
  		av.archive_read_next_header = _archive_read_next_header;
  		av.archive_read_next_header2 = _archive_read_next_header2;
  		av.archive_free = _archive_read_free;
  		av.archive_close = _archive_read_close;
  		inited = 1;
  	}
  	return (&av);
  }
  
  /*
   * Allocate, initialize and return a struct archive object.
   */
  struct archive *
  archive_read_new(void)
  {
  	struct archive_read *a;
  
  	a = (struct archive_read *)calloc(1, sizeof(*a));
  	if (a == NULL)
  		return (NULL);
  	a->archive.magic = ARCHIVE_READ_MAGIC;
  
  	a->archive.state = ARCHIVE_STATE_NEW;
  	a->entry = archive_entry_new2(&a->archive);
  	a->archive.vtable = archive_read_vtable();
  
  	a->passphrases.last = &a->passphrases.first;
  
  	return (&a->archive);
  }
  
  /*
   * Record the do-not-extract-to file. This belongs in archive_read_extract.c.
   */
  void
  archive_read_extract_set_skip_file(struct archive *_a, int64_t d, int64_t i)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  
  	if (ARCHIVE_OK != __archive_check_magic(_a, ARCHIVE_READ_MAGIC,
  		ARCHIVE_STATE_ANY, "archive_read_extract_set_skip_file"))
  		return;
  	a->skip_file_set = 1;
  	a->skip_file_dev = d;
  	a->skip_file_ino = i;
  }
  
  /*
   * Open the archive
   */
  int
  archive_read_open(struct archive *a, void *client_data,
      archive_open_callback *client_opener, archive_read_callback *client_reader,
      archive_close_callback *client_closer)
  {
  	/* Old archive_read_open() is just a thin shell around
  	 * archive_read_open1. */
  	archive_read_set_open_callback(a, client_opener);
  	archive_read_set_read_callback(a, client_reader);
  	archive_read_set_close_callback(a, client_closer);
  	archive_read_set_callback_data(a, client_data);
  	return archive_read_open1(a);
  }
  
  
  int
  archive_read_open2(struct archive *a, void *client_data,
      archive_open_callback *client_opener,
      archive_read_callback *client_reader,
      archive_skip_callback *client_skipper,
      archive_close_callback *client_closer)
  {
  	/* Old archive_read_open2() is just a thin shell around
  	 * archive_read_open1. */
  	archive_read_set_callback_data(a, client_data);
  	archive_read_set_open_callback(a, client_opener);
  	archive_read_set_read_callback(a, client_reader);
  	archive_read_set_skip_callback(a, client_skipper);
  	archive_read_set_close_callback(a, client_closer);
  	return archive_read_open1(a);
  }
  
  static ssize_t
  client_read_proxy(struct archive_read_filter *self, const void **buff)
  {
  	ssize_t r;
  	r = (self->archive->client.reader)(&self->archive->archive,
  	    self->data, buff);
  	return (r);
  }
  
  static int64_t
  client_skip_proxy(struct archive_read_filter *self, int64_t request)
  {
  	if (request < 0)
  		__archive_errx(1, "Negative skip requested.");
  	if (request == 0)
  		return 0;
  
  	if (self->archive->client.skipper != NULL) {
  		/* Seek requests over 1GiB are broken down into
  		 * multiple seeks.  This avoids overflows when the
  		 * requests get passed through 32-bit arguments. */
  		int64_t skip_limit = (int64_t)1 << 30;
  		int64_t total = 0;
  		for (;;) {
  			int64_t get, ask = request;
  			if (ask > skip_limit)
  				ask = skip_limit;
  			get = (self->archive->client.skipper)
  				(&self->archive->archive, self->data, ask);
  			total += get;
  			if (get == 0 || get == request)
  				return (total);
  			if (get > request)
  				return ARCHIVE_FATAL;
  			request -= get;
  		}
  	} else if (self->archive->client.seeker != NULL
  		&& request > 64 * 1024) {
  		/* If the client provided a seeker but not a skipper,
  		 * we can use the seeker to skip forward.
  		 *
  		 * Note: This isn't always a good idea.  The client
  		 * skipper is allowed to skip by less than requested
  		 * if it needs to maintain block alignment.  The
  		 * seeker is not allowed to play such games, so using
  		 * the seeker here may be a performance loss compared
  		 * to just reading and discarding.  That's why we
  		 * only do this for skips of over 64k.
  		 */
  		int64_t before = self->position;
  		int64_t after = (self->archive->client.seeker)
  		    (&self->archive->archive, self->data, request, SEEK_CUR);
  		if (after != before + request)
  			return ARCHIVE_FATAL;
  		return after - before;
  	}
  	return 0;
  }
  
  static int64_t
  client_seek_proxy(struct archive_read_filter *self, int64_t offset, int whence)
  {
  	/* DO NOT use the skipper here!  If we transparently handled
  	 * forward seek here by using the skipper, that will break
  	 * other libarchive code that assumes a successful forward
  	 * seek means it can also seek backwards.
  	 */
  	if (self->archive->client.seeker == NULL) {
  		archive_set_error(&self->archive->archive, ARCHIVE_ERRNO_MISC,
  		    "Current client reader does not support seeking a device");
  		return (ARCHIVE_FAILED);
  	}
  	return (self->archive->client.seeker)(&self->archive->archive,
  	    self->data, offset, whence);
  }
  
  static int
  client_close_proxy(struct archive_read_filter *self)
  {
  	int r = ARCHIVE_OK, r2;
  	unsigned int i;
  
  	if (self->archive->client.closer == NULL)
  		return (r);
  	for (i = 0; i < self->archive->client.nodes; i++)
  	{
  		r2 = (self->archive->client.closer)
  			((struct archive *)self->archive,
  				self->archive->client.dataset[i].data);
  		if (r > r2)
  			r = r2;
  	}
  	return (r);
  }
  
  static int
  client_open_proxy(struct archive_read_filter *self)
  {
    int r = ARCHIVE_OK;
  	if (self->archive->client.opener != NULL)
  		r = (self->archive->client.opener)(
  		    (struct archive *)self->archive, self->data);
  	return (r);
  }
  
  static int
  client_switch_proxy(struct archive_read_filter *self, unsigned int iindex)
  {
    int r1 = ARCHIVE_OK, r2 = ARCHIVE_OK;
  	void *data2 = NULL;
  
  	/* Don't do anything if already in the specified data node */
  	if (self->archive->client.cursor == iindex)
  		return (ARCHIVE_OK);
  
  	self->archive->client.cursor = iindex;
  	data2 = self->archive->client.dataset[self->archive->client.cursor].data;
  	if (self->archive->client.switcher != NULL)
  	{
  		r1 = r2 = (self->archive->client.switcher)
  			((struct archive *)self->archive, self->data, data2);
  		self->data = data2;
  	}
  	else
  	{
  		/* Attempt to call close and open instead */
  		if (self->archive->client.closer != NULL)
  			r1 = (self->archive->client.closer)
  				((struct archive *)self->archive, self->data);
  		self->data = data2;
  		if (self->archive->client.opener != NULL)
  			r2 = (self->archive->client.opener)
  				((struct archive *)self->archive, self->data);
  	}
  	return (r1 < r2) ? r1 : r2;
  }
  
  int
  archive_read_set_open_callback(struct archive *_a,
      archive_open_callback *client_opener)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	archive_check_magic(_a, ARCHIVE_READ_MAGIC, ARCHIVE_STATE_NEW,
  	    "archive_read_set_open_callback");
  	a->client.opener = client_opener;
  	return ARCHIVE_OK;
  }
  
  int
  archive_read_set_read_callback(struct archive *_a,
      archive_read_callback *client_reader)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	archive_check_magic(_a, ARCHIVE_READ_MAGIC, ARCHIVE_STATE_NEW,
  	    "archive_read_set_read_callback");
  	a->client.reader = client_reader;
  	return ARCHIVE_OK;
  }
  
  int
  archive_read_set_skip_callback(struct archive *_a,
      archive_skip_callback *client_skipper)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	archive_check_magic(_a, ARCHIVE_READ_MAGIC, ARCHIVE_STATE_NEW,
  	    "archive_read_set_skip_callback");
  	a->client.skipper = client_skipper;
  	return ARCHIVE_OK;
  }
  
  int
  archive_read_set_seek_callback(struct archive *_a,
      archive_seek_callback *client_seeker)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	archive_check_magic(_a, ARCHIVE_READ_MAGIC, ARCHIVE_STATE_NEW,
  	    "archive_read_set_seek_callback");
  	a->client.seeker = client_seeker;
  	return ARCHIVE_OK;
  }
  
  int
  archive_read_set_close_callback(struct archive *_a,
      archive_close_callback *client_closer)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	archive_check_magic(_a, ARCHIVE_READ_MAGIC, ARCHIVE_STATE_NEW,
  	    "archive_read_set_close_callback");
  	a->client.closer = client_closer;
  	return ARCHIVE_OK;
  }
  
  int
  archive_read_set_switch_callback(struct archive *_a,
      archive_switch_callback *client_switcher)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	archive_check_magic(_a, ARCHIVE_READ_MAGIC, ARCHIVE_STATE_NEW,
  	    "archive_read_set_switch_callback");
  	a->client.switcher = client_switcher;
  	return ARCHIVE_OK;
  }
  
  int
  archive_read_set_callback_data(struct archive *_a, void *client_data)
  {
  	return archive_read_set_callback_data2(_a, client_data, 0);
  }
  
  int
  archive_read_set_callback_data2(struct archive *_a, void *client_data,
      unsigned int iindex)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	archive_check_magic(_a, ARCHIVE_READ_MAGIC, ARCHIVE_STATE_NEW,
  	    "archive_read_set_callback_data2");
  
  	if (a->client.nodes == 0)
  	{
  		a->client.dataset = (struct archive_read_data_node *)
  		    calloc(1, sizeof(*a->client.dataset));
  		if (a->client.dataset == NULL)
  		{
  			archive_set_error(&a->archive, ENOMEM,
  				"No memory.");
  			return ARCHIVE_FATAL;
  		}
  		a->client.nodes = 1;
  	}
  
  	if (iindex > a->client.nodes - 1)
  	{
  		archive_set_error(&a->archive, EINVAL,
  			"Invalid index specified.");
  		return ARCHIVE_FATAL;
  	}
  	a->client.dataset[iindex].data = client_data;
  	a->client.dataset[iindex].begin_position = -1;
  	a->client.dataset[iindex].total_size = -1;
  	return ARCHIVE_OK;
  }
  
  int
  archive_read_add_callback_data(struct archive *_a, void *client_data,
      unsigned int iindex)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	void *p;
  	unsigned int i;
  
  	archive_check_magic(_a, ARCHIVE_READ_MAGIC, ARCHIVE_STATE_NEW,
  	    "archive_read_add_callback_data");
  	if (iindex > a->client.nodes) {
  		archive_set_error(&a->archive, EINVAL,
  			"Invalid index specified.");
  		return ARCHIVE_FATAL;
  	}
  	p = realloc(a->client.dataset, sizeof(*a->client.dataset)
  		* (++(a->client.nodes)));
  	if (p == NULL) {
  		archive_set_error(&a->archive, ENOMEM,
  			"No memory.");
  		return ARCHIVE_FATAL;
  	}
  	a->client.dataset = (struct archive_read_data_node *)p;
  	for (i = a->client.nodes - 1; i > iindex && i > 0; i--) {
  		a->client.dataset[i].data = a->client.dataset[i-1].data;
  		a->client.dataset[i].begin_position = -1;
  		a->client.dataset[i].total_size = -1;
  	}
  	a->client.dataset[iindex].data = client_data;
  	a->client.dataset[iindex].begin_position = -1;
  	a->client.dataset[iindex].total_size = -1;
  	return ARCHIVE_OK;
  }
  
  int
  archive_read_append_callback_data(struct archive *_a, void *client_data)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	return archive_read_add_callback_data(_a, client_data, a->client.nodes);
  }
  
  int
  archive_read_prepend_callback_data(struct archive *_a, void *client_data)
  {
  	return archive_read_add_callback_data(_a, client_data, 0);
  }
  
  int
  archive_read_open1(struct archive *_a)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	struct archive_read_filter *filter, *tmp;
  	int slot, e = ARCHIVE_OK;
  	unsigned int i;
  
  	archive_check_magic(_a, ARCHIVE_READ_MAGIC, ARCHIVE_STATE_NEW,
  	    "archive_read_open");
  	archive_clear_error(&a->archive);
  
  	if (a->client.reader == NULL) {
  		archive_set_error(&a->archive, EINVAL,
  		    "No reader function provided to archive_read_open");
  		a->archive.state = ARCHIVE_STATE_FATAL;
  		return (ARCHIVE_FATAL);
  	}
  
  	/* Open data source. */
  	if (a->client.opener != NULL) {
  		e = (a->client.opener)(&a->archive, a->client.dataset[0].data);
  		if (e != 0) {
  			/* If the open failed, call the closer to clean up. */
  			if (a->client.closer) {
  				for (i = 0; i < a->client.nodes; i++)
  					(a->client.closer)(&a->archive,
  					    a->client.dataset[i].data);
  			}
  			return (e);
  		}
  	}
  
  	filter = calloc(1, sizeof(*filter));
  	if (filter == NULL)
  		return (ARCHIVE_FATAL);
  	filter->bidder = NULL;
  	filter->upstream = NULL;
  	filter->archive = a;
  	filter->data = a->client.dataset[0].data;
  	filter->open = client_open_proxy;
  	filter->read = client_read_proxy;
  	filter->skip = client_skip_proxy;
  	filter->seek = client_seek_proxy;
  	filter->close = client_close_proxy;
  	filter->sswitch = client_switch_proxy;
  	filter->name = "none";
  	filter->code = ARCHIVE_FILTER_NONE;
  
  	a->client.dataset[0].begin_position = 0;
  	if (!a->filter || !a->bypass_filter_bidding)
  	{
  		a->filter = filter;
  		/* Build out the input pipeline. */
  		e = choose_filters(a);
  		if (e < ARCHIVE_WARN) {
  			a->archive.state = ARCHIVE_STATE_FATAL;
  			return (ARCHIVE_FATAL);
  		}
  	}
  	else
  	{
  		/* Need to add "NONE" type filter at the end of the filter chain */
  		tmp = a->filter;
  		while (tmp->upstream)
  			tmp = tmp->upstream;
  		tmp->upstream = filter;
  	}
  
  	if (!a->format)
  	{
  		slot = choose_format(a);
  		if (slot < 0) {
  			close_filters(a);
  			a->archive.state = ARCHIVE_STATE_FATAL;
  			return (ARCHIVE_FATAL);
  		}
  		a->format = &(a->formats[slot]);
  	}
  
  	a->archive.state = ARCHIVE_STATE_HEADER;
  
  	/* Ensure libarchive starts from the first node in a multivolume set */
  	client_switch_proxy(a->filter, 0);
  	return (e);
  }
  
  /*
   * Allow each registered stream transform to bid on whether
   * it wants to handle this stream.  Repeat until we've finished
   * building the pipeline.
   */
  
  /* We won't build a filter pipeline with more stages than this. */
  #define MAX_NUMBER_FILTERS 25
  
  static int
  choose_filters(struct archive_read *a)
  {
  	int number_bidders, i, bid, best_bid, number_filters;
  	struct archive_read_filter_bidder *bidder, *best_bidder;
  	struct archive_read_filter *filter;
  	ssize_t avail;
  	int r;
  
  	for (number_filters = 0; number_filters < MAX_NUMBER_FILTERS; ++number_filters) {
  		number_bidders = sizeof(a->bidders) / sizeof(a->bidders[0]);
  
  		best_bid = 0;
  		best_bidder = NULL;
  
  		bidder = a->bidders;
  		for (i = 0; i < number_bidders; i++, bidder++) {
  			if (bidder->bid != NULL) {
  				bid = (bidder->bid)(bidder, a->filter);
  				if (bid > best_bid) {
  					best_bid = bid;
  					best_bidder = bidder;
  				}
  			}
  		}
  
  		/* If no bidder, we're done. */
  		if (best_bidder == NULL) {
  			/* Verify the filter by asking it for some data. */
  			__archive_read_filter_ahead(a->filter, 1, &avail);
  			if (avail < 0) {
  				__archive_read_free_filters(a);
  				return (ARCHIVE_FATAL);
  			}
  			a->archive.compression_name = a->filter->name;
  			a->archive.compression_code = a->filter->code;
  			return (ARCHIVE_OK);
  		}
  
  		filter
  		    = (struct archive_read_filter *)calloc(1, sizeof(*filter));
  		if (filter == NULL)
  			return (ARCHIVE_FATAL);
  		filter->bidder = best_bidder;
  		filter->archive = a;
  		filter->upstream = a->filter;
  		a->filter = filter;
  		r = (best_bidder->init)(a->filter);
  		if (r != ARCHIVE_OK) {
  			__archive_read_free_filters(a);
  			return (ARCHIVE_FATAL);
  		}
  	}
  	archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
  	    "Input requires too many filters for decoding");
  	return (ARCHIVE_FATAL);
  }
  
  /*
   * Read header of next entry.
   */
  static int
  _archive_read_next_header2(struct archive *_a, struct archive_entry *entry)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	int r1 = ARCHIVE_OK, r2;
  
  	archive_check_magic(_a, ARCHIVE_READ_MAGIC,
  	    ARCHIVE_STATE_HEADER | ARCHIVE_STATE_DATA,
  	    "archive_read_next_header");
  
  	archive_entry_clear(entry);
  	archive_clear_error(&a->archive);
  
  	/*
  	 * If client didn't consume entire data, skip any remainder
  	 * (This is especially important for GNU incremental directories.)
  	 */
  	if (a->archive.state == ARCHIVE_STATE_DATA) {
  		r1 = archive_read_data_skip(&a->archive);
  		if (r1 == ARCHIVE_EOF)
  			archive_set_error(&a->archive, EIO,
  			    "Premature end-of-file.");
  		if (r1 == ARCHIVE_EOF || r1 == ARCHIVE_FATAL) {
  			a->archive.state = ARCHIVE_STATE_FATAL;
  			return (ARCHIVE_FATAL);
  		}
  	}
  
  	/* Record start-of-header offset in uncompressed stream. */
  	a->header_position = a->filter->position;
  
  	++_a->file_count;
  	r2 = (a->format->read_header)(a, entry);
  
  	/*
  	 * EOF and FATAL are persistent at this layer.  By
  	 * modifying the state, we guarantee that future calls to
  	 * read a header or read data will fail.
  	 */
  	switch (r2) {
  	case ARCHIVE_EOF:
  		a->archive.state = ARCHIVE_STATE_EOF;
  		--_a->file_count;/* Revert a file counter. */
  		break;
  	case ARCHIVE_OK:
  		a->archive.state = ARCHIVE_STATE_DATA;
  		break;
  	case ARCHIVE_WARN:
  		a->archive.state = ARCHIVE_STATE_DATA;
  		break;
  	case ARCHIVE_RETRY:
  		break;
  	case ARCHIVE_FATAL:
  		a->archive.state = ARCHIVE_STATE_FATAL;
  		break;
  	}
  
  	__archive_reset_read_data(&a->archive);
  
  	a->data_start_node = a->client.cursor;
  	/* EOF always wins; otherwise return the worst error. */
  	return (r2 < r1 || r2 == ARCHIVE_EOF) ? r2 : r1;
  }
  
  static int
  _archive_read_next_header(struct archive *_a, struct archive_entry **entryp)
  {
  	int ret;
  	struct archive_read *a = (struct archive_read *)_a;
  	*entryp = NULL;
  	ret = _archive_read_next_header2(_a, a->entry);
  	*entryp = a->entry;
  	return ret;
  }
  
  /*
   * Allow each registered format to bid on whether it wants to handle
   * the next entry.  Return index of winning bidder.
   */
  static int
  choose_format(struct archive_read *a)
  {
  	int slots;
  	int i;
  	int bid, best_bid;
  	int best_bid_slot;
  
  	slots = sizeof(a->formats) / sizeof(a->formats[0]);
  	best_bid = -1;
  	best_bid_slot = -1;
  
  	/* Set up a->format for convenience of bidders. */
  	a->format = &(a->formats[0]);
  	for (i = 0; i < slots; i++, a->format++) {
  		if (a->format->bid) {
  			bid = (a->format->bid)(a, best_bid);
  			if (bid == ARCHIVE_FATAL)
  				return (ARCHIVE_FATAL);
  			if (a->filter->position != 0)
  				__archive_read_seek(a, 0, SEEK_SET);
  			if ((bid > best_bid) || (best_bid_slot < 0)) {
  				best_bid = bid;
  				best_bid_slot = i;
  			}
  		}
  	}
  
  	/*
  	 * There were no bidders; this is a serious programmer error
  	 * and demands a quick and definitive abort.
  	 */
  	if (best_bid_slot < 0) {
  		archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
  		    "No formats registered");
  		return (ARCHIVE_FATAL);
  	}
  
  	/*
  	 * There were bidders, but no non-zero bids; this means we
  	 * can't support this stream.
  	 */
  	if (best_bid < 1) {
  		archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
  		    "Unrecognized archive format");
  		return (ARCHIVE_FATAL);
  	}
  
  	return (best_bid_slot);
  }
  
  /*
   * Return the file offset (within the uncompressed data stream) where
   * the last header started.
   */
  int64_t
  archive_read_header_position(struct archive *_a)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	archive_check_magic(_a, ARCHIVE_READ_MAGIC,
  	    ARCHIVE_STATE_ANY, "archive_read_header_position");
  	return (a->header_position);
  }
  
  /*
   * Returns 1 if the archive contains at least one encrypted entry.
   * If the archive format not support encryption at all
   * ARCHIVE_READ_FORMAT_ENCRYPTION_UNSUPPORTED is returned.
   * If for any other reason (e.g. not enough data read so far)
   * we cannot say whether there are encrypted entries, then
   * ARCHIVE_READ_FORMAT_ENCRYPTION_DONT_KNOW is returned.
   * In general, this function will return values below zero when the
   * reader is uncertain or totally incapable of encryption support.
   * When this function returns 0 you can be sure that the reader
   * supports encryption detection but no encrypted entries have
   * been found yet.
   *
   * NOTE: If the metadata/header of an archive is also encrypted, you
   * cannot rely on the number of encrypted entries. That is why this
   * function does not return the number of encrypted entries but#
   * just shows that there are some.
   */
  int
  archive_read_has_encrypted_entries(struct archive *_a)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	int format_supports_encryption = archive_read_format_capabilities(_a)
  			& (ARCHIVE_READ_FORMAT_CAPS_ENCRYPT_DATA | ARCHIVE_READ_FORMAT_CAPS_ENCRYPT_METADATA);
  
  	if (!_a || !format_supports_encryption) {
  		/* Format in general doesn't support encryption */
  		return ARCHIVE_READ_FORMAT_ENCRYPTION_UNSUPPORTED;
  	}
  
  	/* A reader potentially has read enough data now. */
  	if (a->format && a->format->has_encrypted_entries) {
  		return (a->format->has_encrypted_entries)(a);
  	}
  
  	/* For any other reason we cannot say how many entries are there. */
  	return ARCHIVE_READ_FORMAT_ENCRYPTION_DONT_KNOW;
  }
  
  /*
   * Returns a bitmask of capabilities that are supported by the archive format reader.
   * If the reader has no special capabilities, ARCHIVE_READ_FORMAT_CAPS_NONE is returned.
   */
  int
  archive_read_format_capabilities(struct archive *_a)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	if (a && a->format && a->format->format_capabilties) {
  		return (a->format->format_capabilties)(a);
  	}
  	return ARCHIVE_READ_FORMAT_CAPS_NONE;
  }
  
  /*
   * Read data from an archive entry, using a read(2)-style interface.
   * This is a convenience routine that just calls
   * archive_read_data_block and copies the results into the client
   * buffer, filling any gaps with zero bytes.  Clients using this
   * API can be completely ignorant of sparse-file issues; sparse files
   * will simply be padded with nulls.
   *
   * DO NOT intermingle calls to this function and archive_read_data_block
   * to read a single entry body.
   */
  ssize_t
  archive_read_data(struct archive *_a, void *buff, size_t s)
  {
  	struct archive *a = (struct archive *)_a;
  	char	*dest;
  	const void *read_buf;
  	size_t	 bytes_read;
  	size_t	 len;
  	int	 r;
  
  	bytes_read = 0;
  	dest = (char *)buff;
  
  	while (s > 0) {
  		if (a->read_data_remaining == 0) {
  			read_buf = a->read_data_block;
  			a->read_data_is_posix_read = 1;
  			a->read_data_requested = s;
  			r = archive_read_data_block(a, &read_buf,
  			    &a->read_data_remaining, &a->read_data_offset);
  			a->read_data_block = read_buf;
  			if (r == ARCHIVE_EOF)
  				return (bytes_read);
  			/*
  			 * Error codes are all negative, so the status
  			 * return here cannot be confused with a valid
  			 * byte count.  (ARCHIVE_OK is zero.)
  			 */
  			if (r < ARCHIVE_OK)
  				return (r);
  		}
  
  		if (a->read_data_offset < a->read_data_output_offset) {
  			archive_set_error(a, ARCHIVE_ERRNO_FILE_FORMAT,
  			    "Encountered out-of-order sparse blocks");
  			return (ARCHIVE_RETRY);
  		}
  
  		/* Compute the amount of zero padding needed. */
  		if (a->read_data_output_offset + (int64_t)s <
  		    a->read_data_offset) {
  			len = s;
  		} else if (a->read_data_output_offset <
  		    a->read_data_offset) {
  			len = (size_t)(a->read_data_offset -
  			    a->read_data_output_offset);
  		} else
  			len = 0;
  
  		/* Add zeroes. */
  		memset(dest, 0, len);
  		s -= len;
  		a->read_data_output_offset += len;
  		dest += len;
  		bytes_read += len;
  
  		/* Copy data if there is any space left. */
  		if (s > 0) {
  			len = a->read_data_remaining;
  			if (len > s)
  				len = s;
  			memcpy(dest, a->read_data_block, len);
  			s -= len;
  			a->read_data_block += len;
  			a->read_data_remaining -= len;
  			a->read_data_output_offset += len;
  			a->read_data_offset += len;
  			dest += len;
  			bytes_read += len;
  		}
  	}
  	a->read_data_is_posix_read = 0;
  	a->read_data_requested = 0;
  	return (bytes_read);
  }
  
  /*
   * Reset the read_data_* variables, used for starting a new entry.
   */
  void __archive_reset_read_data(struct archive * a)
  {
  	a->read_data_output_offset = 0;
  	a->read_data_remaining = 0;
  	a->read_data_is_posix_read = 0;
  	a->read_data_requested = 0;
  
     /* extra resets, from rar.c */
     a->read_data_block = NULL;
     a->read_data_offset = 0;
  }
  
  /*
   * Skip over all remaining data in this entry.
   */
  int
  archive_read_data_skip(struct archive *_a)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	int r;
  	const void *buff;
  	size_t size;
  	int64_t offset;
  
  	archive_check_magic(_a, ARCHIVE_READ_MAGIC, ARCHIVE_STATE_DATA,
  	    "archive_read_data_skip");
  
  	if (a->format->read_data_skip != NULL)
  		r = (a->format->read_data_skip)(a);
  	else {
  		while ((r = archive_read_data_block(&a->archive,
  			    &buff, &size, &offset))
  		    == ARCHIVE_OK)
  			;
  	}
  
  	if (r == ARCHIVE_EOF)
  		r = ARCHIVE_OK;
  
  	a->archive.state = ARCHIVE_STATE_HEADER;
  	return (r);
  }
  
  int64_t
  archive_seek_data(struct archive *_a, int64_t offset, int whence)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	archive_check_magic(_a, ARCHIVE_READ_MAGIC, ARCHIVE_STATE_DATA,
  	    "archive_seek_data_block");
  
  	if (a->format->seek_data == NULL) {
  		archive_set_error(&a->archive, ARCHIVE_ERRNO_PROGRAMMER,
  		    "Internal error: "
  		    "No format_seek_data_block function registered");
  		return (ARCHIVE_FATAL);
  	}
  
  	return (a->format->seek_data)(a, offset, whence);
  }
  
  /*
   * Read the next block of entry data from the archive.
   * This is a zero-copy interface; the client receives a pointer,
   * size, and file offset of the next available block of data.
   *
   * Returns ARCHIVE_OK if the operation is successful, ARCHIVE_EOF if
   * the end of entry is encountered.
   */
  static int
  _archive_read_data_block(struct archive *_a,
      const void **buff, size_t *size, int64_t *offset)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	archive_check_magic(_a, ARCHIVE_READ_MAGIC, ARCHIVE_STATE_DATA,
  	    "archive_read_data_block");
  
  	if (a->format->read_data == NULL) {
  		archive_set_error(&a->archive, ARCHIVE_ERRNO_PROGRAMMER,
  		    "Internal error: "
  		    "No format->read_data function registered");
  		return (ARCHIVE_FATAL);
  	}
  
  	return (a->format->read_data)(a, buff, size, offset);
  }
  
  static int
  close_filters(struct archive_read *a)
  {
  	struct archive_read_filter *f = a->filter;
  	int r = ARCHIVE_OK;
  	/* Close each filter in the pipeline. */
  	while (f != NULL) {
  		struct archive_read_filter *t = f->upstream;
  		if (!f->closed && f->close != NULL) {
  			int r1 = (f->close)(f);
  			f->closed = 1;
  			if (r1 < r)
  				r = r1;
  		}
  		free(f->buffer);
  		f->buffer = NULL;
  		f = t;
  	}
  	return r;
  }
  
  void
  __archive_read_free_filters(struct archive_read *a)
  {
  	/* Make sure filters are closed and their buffers are freed */
  	close_filters(a);
  
  	while (a->filter != NULL) {
  		struct archive_read_filter *t = a->filter->upstream;
  		free(a->filter);
  		a->filter = t;
  	}
  }
  
  /*
   * return the count of # of filters in use
   */
  static int
  _archive_filter_count(struct archive *_a)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	struct archive_read_filter *p = a->filter;
  	int count = 0;
  	while(p) {
  		count++;
  		p = p->upstream;
  	}
  	return count;
  }
  
  /*
   * Close the file and all I/O.
   */
  static int
  _archive_read_close(struct archive *_a)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	int r = ARCHIVE_OK, r1 = ARCHIVE_OK;
  
  	archive_check_magic(&a->archive, ARCHIVE_READ_MAGIC,
  	    ARCHIVE_STATE_ANY | ARCHIVE_STATE_FATAL, "archive_read_close");
  	if (a->archive.state == ARCHIVE_STATE_CLOSED)
  		return (ARCHIVE_OK);
  	archive_clear_error(&a->archive);
  	a->archive.state = ARCHIVE_STATE_CLOSED;
  
  	/* TODO: Clean up the formatters. */
  
  	/* Release the filter objects. */
  	r1 = close_filters(a);
  	if (r1 < r)
  		r = r1;
  
  	return (r);
  }
  
  /*
   * Release memory and other resources.
   */
  static int
  _archive_read_free(struct archive *_a)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	struct archive_read_passphrase *p;
  	int i, n;
  	int slots;
  	int r = ARCHIVE_OK;
  
  	if (_a == NULL)
  		return (ARCHIVE_OK);
  	archive_check_magic(_a, ARCHIVE_READ_MAGIC,
  	    ARCHIVE_STATE_ANY | ARCHIVE_STATE_FATAL, "archive_read_free");
  	if (a->archive.state != ARCHIVE_STATE_CLOSED
  	    && a->archive.state != ARCHIVE_STATE_FATAL)
  		r = archive_read_close(&a->archive);
  
  	/* Call cleanup functions registered by optional components. */
  	if (a->cleanup_archive_extract != NULL)
  		r = (a->cleanup_archive_extract)(a);
  
  	/* Cleanup format-specific data. */
  	slots = sizeof(a->formats) / sizeof(a->formats[0]);
  	for (i = 0; i < slots; i++) {
  		a->format = &(a->formats[i]);
  		if (a->formats[i].cleanup)
  			(a->formats[i].cleanup)(a);
  	}
  
  	/* Free the filters */
  	__archive_read_free_filters(a);
  
  	/* Release the bidder objects. */
  	n = sizeof(a->bidders)/sizeof(a->bidders[0]);
  	for (i = 0; i < n; i++) {
  		if (a->bidders[i].free != NULL) {
  			int r1 = (a->bidders[i].free)(&a->bidders[i]);
  			if (r1 < r)
  				r = r1;
  		}
  	}
  
  	/* Release passphrase list. */
  	p = a->passphrases.first;
  	while (p != NULL) {
  		struct archive_read_passphrase *np = p->next;
  
  		/* A passphrase should be cleaned. */
  		memset(p->passphrase, 0, strlen(p->passphrase));
  		free(p->passphrase);
  		free(p);
  		p = np;
  	}
  
  	archive_string_free(&a->archive.error_string);
  	archive_entry_free(a->entry);
  	a->archive.magic = 0;
  	__archive_clean(&a->archive);
  	free(a->client.dataset);
  	free(a);
  	return (r);
  }
  
  static struct archive_read_filter *
  get_filter(struct archive *_a, int n)
  {
  	struct archive_read *a = (struct archive_read *)_a;
  	struct archive_read_filter *f = a->filter;
  	/* We use n == -1 for 'the last filter', which is always the
  	 * client proxy. */
  	if (n == -1 && f != NULL) {
  		struct archive_read_filter *last = f;
  		f = f->upstream;
  		while (f != NULL) {
  			last = f;
  			f = f->upstream;
  		}
  		return (last);
  	}
  	if (n < 0)
  		return NULL;
  	while (n > 0 && f != NULL) {
  		f = f->upstream;
  		--n;
  	}
  	return (f);
  }
  
  static int
  _archive_filter_code(struct archive *_a, int n)
  {
  	struct archive_read_filter *f = get_filter(_a, n);
  	return f == NULL ? -1 : f->code;
  }
  
  static const char *
  _archive_filter_name(struct archive *_a, int n)
  {
  	struct archive_read_filter *f = get_filter(_a, n);
  	return f != NULL ? f->name : NULL;
  }
  
  static int64_t
  _archive_filter_bytes(struct archive *_a, int n)
  {
  	struct archive_read_filter *f = get_filter(_a, n);
  	return f == NULL ? -1 : f->position;
  }
  
  /*
   * Used internally by read format handlers to register their bid and
   * initialization functions.
   */
  int
  __archive_read_register_format(struct archive_read *a,
      void *format_data,
      const char *name,
      int (*bid)(struct archive_read *, int),
      int (*options)(struct archive_read *, const char *, const char *),
      int (*read_header)(struct archive_read *, struct archive_entry *),
      int (*read_data)(struct archive_read *, const void **, size_t *, int64_t *),
      int (*read_data_skip)(struct archive_read *),
      int64_t (*seek_data)(struct archive_read *, int64_t, int),
      int (*cleanup)(struct archive_read *),
      int (*format_capabilities)(struct archive_read *),
      int (*has_encrypted_entries)(struct archive_read *))
  {
  	int i, number_slots;
  
  	archive_check_magic(&a->archive,
  	    ARCHIVE_READ_MAGIC, ARCHIVE_STATE_NEW,
  	    "__archive_read_register_format");
  
  	number_slots = sizeof(a->formats) / sizeof(a->formats[0]);
  
  	for (i = 0; i < number_slots; i++) {
  		if (a->formats[i].bid == bid)
  			return (ARCHIVE_WARN); /* We've already installed */
  		if (a->formats[i].bid == NULL) {
  			a->formats[i].bid = bid;
  			a->formats[i].options = options;
  			a->formats[i].read_header = read_header;
  			a->formats[i].read_data = read_data;
  			a->formats[i].read_data_skip = read_data_skip;
  			a->formats[i].seek_data = seek_data;
  			a->formats[i].cleanup = cleanup;
  			a->formats[i].data = format_data;
  			a->formats[i].name = name;
  			a->formats[i].format_capabilties = format_capabilities;
  			a->formats[i].has_encrypted_entries = has_encrypted_entries;
  			return (ARCHIVE_OK);
  		}
  	}
  
  	archive_set_error(&a->archive, ENOMEM,
  	    "Not enough slots for format registration");
  	return (ARCHIVE_FATAL);
  }
  
  /*
   * Used internally by decompression routines to register their bid and
   * initialization functions.
   */
  int
  __archive_read_get_bidder(struct archive_read *a,
      struct archive_read_filter_bidder **bidder)
  {
  	int i, number_slots;
  
  	number_slots = sizeof(a->bidders) / sizeof(a->bidders[0]);
  
  	for (i = 0; i < number_slots; i++) {
  		if (a->bidders[i].bid == NULL) {
  			memset(a->bidders + i, 0, sizeof(a->bidders[0]));
  			*bidder = (a->bidders + i);
  			return (ARCHIVE_OK);
  		}
  	}
  
  	archive_set_error(&a->archive, ENOMEM,
  	    "Not enough slots for filter registration");
  	return (ARCHIVE_FATAL);
  }
  
  /*
   * The next section implements the peek/consume internal I/O
   * system used by archive readers.  This system allows simple
   * read-ahead for consumers while preserving zero-copy operation
   * most of the time.
   *
   * The two key operations:
   *  * The read-ahead function returns a pointer to a block of data
   *    that satisfies a minimum request.
   *  * The consume function advances the file pointer.
   *
   * In the ideal case, filters generate blocks of data
   * and __archive_read_ahead() just returns pointers directly into
   * those blocks.  Then __archive_read_consume() just bumps those
   * pointers.  Only if your request would span blocks does the I/O
   * layer use a copy buffer to provide you with a contiguous block of
   * data.
   *
   * A couple of useful idioms:
   *  * "I just want some data."  Ask for 1 byte and pay attention to
   *    the "number of bytes available" from __archive_read_ahead().
   *    Consume whatever you actually use.
   *  * "I want to output a large block of data."  As above, ask for 1 byte,
   *    emit all that's available (up to whatever limit you have), consume
   *    it all, then repeat until you're done.  This effectively means that
   *    you're passing along the blocks that came from your provider.
   *  * "I want to peek ahead by a large amount."  Ask for 4k or so, then
   *    double and repeat until you get an error or have enough.  Note
   *    that the I/O layer will likely end up expanding its copy buffer
   *    to fit your request, so use this technique cautiously.  This
   *    technique is used, for example, by some of the format tasting
   *    code that has uncertain look-ahead needs.
   */
  
  /*
   * Looks ahead in the input stream:
   *  * If 'avail' pointer is provided, that returns number of bytes available
   *    in the current buffer, which may be much larger than requested.
   *  * If end-of-file, *avail gets set to zero.
   *  * If error, *avail gets error code.
   *  * If request can be met, returns pointer to data.
   *  * If minimum request cannot be met, returns NULL.
   *
   * Note: If you just want "some data", ask for 1 byte and pay attention
   * to *avail, which will have the actual amount available.  If you
   * know exactly how many bytes you need, just ask for that and treat
   * a NULL return as an error.
   *
   * Important:  This does NOT move the file pointer.  See
   * __archive_read_consume() below.
   */
  const void *
  __archive_read_ahead(struct archive_read *a, size_t min, ssize_t *avail)
  {
  	return (__archive_read_filter_ahead(a->filter, min, avail));
  }
  
  const void *
  __archive_read_filter_ahead(struct archive_read_filter *filter,
      size_t min, ssize_t *avail)
  {
  	ssize_t bytes_read;
  	size_t tocopy;
  
  	if (filter->fatal) {
  		if (avail)
  			*avail = ARCHIVE_FATAL;
  		return (NULL);
  	}
  
  	/*
  	 * Keep pulling more data until we can satisfy the request.
  	 */
  	for (;;) {
  
  		/*
  		 * If we can satisfy from the copy buffer (and the
  		 * copy buffer isn't empty), we're done.  In particular,
  		 * note that min == 0 is a perfectly well-defined
  		 * request.
  		 */
  		if (filter->avail >= min && filter->avail > 0) {
  			if (avail != NULL)
  				*avail = filter->avail;
  			return (filter->next);
  		}
  
  		/*
  		 * We can satisfy directly from client buffer if everything
  		 * currently in the copy buffer is still in the client buffer.
  		 */
  		if (filter->client_total >= filter->client_avail + filter->avail
  		    && filter->client_avail + filter->avail >= min) {
  			/* "Roll back" to client buffer. */
  			filter->client_avail += filter->avail;
  			filter->client_next -= filter->avail;
  			/* Copy buffer is now empty. */
  			filter->avail = 0;
  			filter->next = filter->buffer;
  			/* Return data from client buffer. */
  			if (avail != NULL)
  				*avail = filter->client_avail;
  			return (filter->client_next);
  		}
  
  		/* Move data forward in copy buffer if necessary. */
  		if (filter->next > filter->buffer &&
  		    filter->next + min > filter->buffer + filter->buffer_size) {
  			if (filter->avail > 0)
  				memmove(filter->buffer, filter->next,
  				    filter->avail);
  			filter->next = filter->buffer;
  		}
  
  		/* If we've used up the client data, get more. */
  		if (filter->client_avail <= 0) {
  			if (filter->end_of_file) {
  				if (avail != NULL)
  					*avail = 0;
  				return (NULL);
  			}
  			bytes_read = (filter->read)(filter,
  			    &filter->client_buff);
  			if (bytes_read < 0) {		/* Read error. */
  				filter->client_total = filter->client_avail = 0;
  				filter->client_next =
  				    filter->client_buff = NULL;
  				filter->fatal = 1;
  				if (avail != NULL)
  					*avail = ARCHIVE_FATAL;
  				return (NULL);
  			}
  			if (bytes_read == 0) {
  				/* Check for another client object first */
  				if (filter->archive->client.cursor !=
  				      filter->archive->client.nodes - 1) {
  					if (client_switch_proxy(filter,
  					    filter->archive->client.cursor + 1)
  					    == ARCHIVE_OK)
  						continue;
  				}
  				/* Premature end-of-file. */
  				filter->client_total = filter->client_avail = 0;
  				filter->client_next =
  				    filter->client_buff = NULL;
  				filter->end_of_file = 1;
  				/* Return whatever we do have. */
  				if (avail != NULL)
  					*avail = filter->avail;
  				return (NULL);
  			}
  			filter->client_total = bytes_read;
  			filter->client_avail = filter->client_total;
  			filter->client_next = filter->client_buff;
  		} else {
  			/*
  			 * We can't satisfy the request from the copy
  			 * buffer or the existing client data, so we
  			 * need to copy more client data over to the
  			 * copy buffer.
  			 */
  
  			/* Ensure the buffer is big enough. */
  			if (min > filter->buffer_size) {
  				size_t s, t;
  				char *p;
  
  				/* Double the buffer; watch for overflow. */
  				s = t = filter->buffer_size;
  				if (s == 0)
  					s = min;
  				while (s < min) {
  					t *= 2;
  					if (t <= s) { /* Integer overflow! */
  						archive_set_error(
  						    &filter->archive->archive,
  						    ENOMEM,
  						    "Unable to allocate copy"
  						    " buffer");
  						filter->fatal = 1;
  						if (avail != NULL)
  							*avail = ARCHIVE_FATAL;
  						return (NULL);
  					}
  					s = t;
  				}
  				/* Now s >= min, so allocate a new buffer. */
  				p = (char *)malloc(s);
  				if (p == NULL) {
  					archive_set_error(
  						&filter->archive->archive,
  						ENOMEM,
  					    "Unable to allocate copy buffer");
  					filter->fatal = 1;
  					if (avail != NULL)
  						*avail = ARCHIVE_FATAL;
  					return (NULL);
  				}
  				/* Move data into newly-enlarged buffer. */
  				if (filter->avail > 0)
  					memmove(p, filter->next, filter->avail);
  				free(filter->buffer);
  				filter->next = filter->buffer = p;
  				filter->buffer_size = s;
  			}
  
  			/* We can add client data to copy buffer. */
  			/* First estimate: copy to fill rest of buffer. */
  			tocopy = (filter->buffer + filter->buffer_size)
  			    - (filter->next + filter->avail);
  			/* Don't waste time buffering more than we need to. */
  			if (tocopy + filter->avail > min)
  				tocopy = min - filter->avail;
  			/* Don't copy more than is available. */
  			if (tocopy > filter->client_avail)
  				tocopy = filter->client_avail;
  
  			memcpy(filter->next + filter->avail,
  			    filter->client_next, tocopy);
  			/* Remove this data from client buffer. */
  			filter->client_next += tocopy;
  			filter->client_avail -= tocopy;
  			/* add it to copy buffer. */
  			filter->avail += tocopy;
  		}
  	}
  }
  
  /*
   * Move the file pointer forward.
   */
  int64_t
  __archive_read_consume(struct archive_read *a, int64_t request)
  {
  	return (__archive_read_filter_consume(a->filter, request));
  }
  
  int64_t
  __archive_read_filter_consume(struct archive_read_filter * filter,
      int64_t request)
  {
  	int64_t skipped;
  
  	if (request < 0)
  		return ARCHIVE_FATAL;
  	if (request == 0)
  		return 0;
  
  	skipped = advance_file_pointer(filter, request);
  	if (skipped == request)
  		return (skipped);
  	/* We hit EOF before we satisfied the skip request. */
  	if (skipped < 0)  /* Map error code to 0 for error message below. */
  		skipped = 0;
  	archive_set_error(&filter->archive->archive,
  	    ARCHIVE_ERRNO_MISC,
  	    "Truncated input file (needed %jd bytes, only %jd available)",
  	    (intmax_t)request, (intmax_t)skipped);
  	return (ARCHIVE_FATAL);
  }
  
  /*
   * Advance the file pointer by the amount requested.
   * Returns the amount actually advanced, which may be less than the
   * request if EOF is encountered first.
   * Returns a negative value if there's an I/O error.
   */
  static int64_t
  advance_file_pointer(struct archive_read_filter *filter, int64_t request)
  {
  	int64_t bytes_skipped, total_bytes_skipped = 0;
  	ssize_t bytes_read;
  	size_t min;
  
  	if (filter->fatal)
  		return (-1);
  
  	/* Use up the copy buffer first. */
  	if (filter->avail > 0) {
  		min = (size_t)minimum(request, (int64_t)filter->avail);
  		filter->next += min;
  		filter->avail -= min;
  		request -= min;
  		filter->position += min;
  		total_bytes_skipped += min;
  	}
  
  	/* Then use up the client buffer. */
  	if (filter->client_avail > 0) {
  		min = (size_t)minimum(request, (int64_t)filter->client_avail);
  		filter->client_next += min;
  		filter->client_avail -= min;
  		request -= min;
  		filter->position += min;
  		total_bytes_skipped += min;
  	}
  	if (request == 0)
  		return (total_bytes_skipped);
  
  	/* If there's an optimized skip function, use it. */
  	if (filter->skip != NULL) {
  		bytes_skipped = (filter->skip)(filter, request);
  		if (bytes_skipped < 0) {	/* error */
  			filter->fatal = 1;
  			return (bytes_skipped);
  		}
  		filter->position += bytes_skipped;
  		total_bytes_skipped += bytes_skipped;
  		request -= bytes_skipped;
  		if (request == 0)
  			return (total_bytes_skipped);
  	}
  
  	/* Use ordinary reads as necessary to complete the request. */
  	for (;;) {
  		bytes_read = (filter->read)(filter, &filter->client_buff);
  		if (bytes_read < 0) {
  			filter->client_buff = NULL;
  			filter->fatal = 1;
  			return (bytes_read);
  		}
  
  		if (bytes_read == 0) {
  			if (filter->archive->client.cursor !=
  			      filter->archive->client.nodes - 1) {
  				if (client_switch_proxy(filter,
  				    filter->archive->client.cursor + 1)
  				    == ARCHIVE_OK)
  					continue;
  			}
  			filter->client_buff = NULL;
  			filter->end_of_file = 1;
  			return (total_bytes_skipped);
  		}
  
  		if (bytes_read >= request) {
  			filter->client_next =
  			    ((const char *)filter->client_buff) + request;
  			filter->client_avail = (size_t)(bytes_read - request);
  			filter->client_total = bytes_read;
  			total_bytes_skipped += request;
  			filter->position += request;
  			return (total_bytes_skipped);
  		}
  
  		filter->position += bytes_read;
  		total_bytes_skipped += bytes_read;
  		request -= bytes_read;
  	}
  }
  
  /**
   * Returns ARCHIVE_FAILED if seeking isn't supported.
   */
  int64_t
  __archive_read_seek(struct archive_read *a, int64_t offset, int whence)
  {
  	return __archive_read_filter_seek(a->filter, offset, whence);
  }
  
  int64_t
  __archive_read_filter_seek(struct archive_read_filter *filter, int64_t offset,
      int whence)
  {
  	struct archive_read_client *client;
  	int64_t r;
  	unsigned int cursor;
  
  	if (filter->closed || filter->fatal)
  		return (ARCHIVE_FATAL);
  	if (filter->seek == NULL)
  		return (ARCHIVE_FAILED);
  
  	client = &(filter->archive->client);
  	switch (whence) {
  	case SEEK_CUR:
  		/* Adjust the offset and use SEEK_SET instead */
  		offset += filter->position;			
  	case SEEK_SET:
  		cursor = 0;
  		while (1)
  		{
  			if (client->dataset[cursor].begin_position < 0 ||
  			    client->dataset[cursor].total_size < 0 ||
  			    client->dataset[cursor].begin_position +
  			      client->dataset[cursor].total_size - 1 > offset ||
  			    cursor + 1 >= client->nodes)
  				break;
  			r = client->dataset[cursor].begin_position +
  				client->dataset[cursor].total_size;
  			client->dataset[++cursor].begin_position = r;
  		}
  		while (1) {
  			r = client_switch_proxy(filter, cursor);
  			if (r != ARCHIVE_OK)
  				return r;
  			if ((r = client_seek_proxy(filter, 0, SEEK_END)) < 0)
  				return r;
  			client->dataset[cursor].total_size = r;
  			if (client->dataset[cursor].begin_position +
  			    client->dataset[cursor].total_size - 1 > offset ||
  			    cursor + 1 >= client->nodes)
  				break;
  			r = client->dataset[cursor].begin_position +
  				client->dataset[cursor].total_size;
  			client->dataset[++cursor].begin_position = r;
  		}
  		offset -= client->dataset[cursor].begin_position;
  		if (offset < 0
  		    || offset > client->dataset[cursor].total_size)
  			return ARCHIVE_FATAL;
  		if ((r = client_seek_proxy(filter, offset, SEEK_SET)) < 0)
  			return r;
  		break;
  
  	case SEEK_END:
  		cursor = 0;
  		while (1) {
  			if (client->dataset[cursor].begin_position < 0 ||
  			    client->dataset[cursor].total_size < 0 ||
  			    cursor + 1 >= client->nodes)
  				break;
  			r = client->dataset[cursor].begin_position +
  				client->dataset[cursor].total_size;
  			client->dataset[++cursor].begin_position = r;
  		}
  		while (1) {
  			r = client_switch_proxy(filter, cursor);
  			if (r != ARCHIVE_OK)
  				return r;
  			if ((r = client_seek_proxy(filter, 0, SEEK_END)) < 0)
  				return r;
  			client->dataset[cursor].total_size = r;
  			r = client->dataset[cursor].begin_position +
  				client->dataset[cursor].total_size;
  			if (cursor + 1 >= client->nodes)
  				break;
  			client->dataset[++cursor].begin_position = r;
  		}
  		while (1) {
  			if (r + offset >=
  			    client->dataset[cursor].begin_position)
  				break;
  			offset += client->dataset[cursor].total_size;
  			if (cursor == 0)
  				break;
  			cursor--;
  			r = client->dataset[cursor].begin_position +
  				client->dataset[cursor].total_size;
  		}
  		offset = (r + offset) - client->dataset[cursor].begin_position;
  		if ((r = client_switch_proxy(filter, cursor)) != ARCHIVE_OK)
  			return r;
  		r = client_seek_proxy(filter, offset, SEEK_SET);
  		if (r < ARCHIVE_OK)
  			return r;
  		break;
  
  	default:
  		return (ARCHIVE_FATAL);
  	}
  	r += client->dataset[cursor].begin_position;
  
  	if (r >= 0) {
  		/*
  		 * Ouch.  Clearing the buffer like this hurts, especially
  		 * at bid time.  A lot of our efficiency at bid time comes
  		 * from having bidders reuse the data we've already read.
  		 *
  		 * TODO: If the seek request is in data we already
  		 * have, then don't call the seek callback.
  		 *
  		 * TODO: Zip seeks to end-of-file at bid time.  If
  		 * other formats also start doing this, we may need to
  		 * find a way for clients to fudge the seek offset to
  		 * a block boundary.
  		 *
  		 * Hmmm... If whence was SEEK_END, we know the file
  		 * size is (r - offset).  Can we use that to simplify
  		 * the TODO items above?
  		 */
  		filter->avail = filter->client_avail = 0;
  		filter->next = filter->buffer;
  		filter->position = r;
  		filter->end_of_file = 0;
  	}
  	return r;
  }
  