/src/libarchive/libarchive/archive_read.c

Source
/*-
 * 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"

#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif
#ifdef HAVE_LIMITS_H
#include <limits.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_integer.h"
#include "archive_private.h"
#include "archive_read_private.h"

#define minimum(a, b) (a < b ? a : b)

static int  bid_format(struct archive_read *, int);
static int  choose_filters(struct archive_read *);
static int  choose_format(struct archive_read *);
static int  close_filters(struct archive_read *);
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 const struct archive_vtable
archive_read_vtable = {
  .archive_filter_bytes = _archive_filter_bytes,
  .archive_filter_code = _archive_filter_code,
  .archive_filter_name = _archive_filter_name,
  .archive_filter_count = _archive_filter_count,
  .archive_read_data_block = _archive_read_data_block,
  .archive_read_next_header = _archive_read_next_header,
  .archive_read_next_header2 = _archive_read_next_header2,
  .archive_free = _archive_read_free,
  .archive_close = _archive_read_close,
};

/*
 * Allocate, initialize and return a struct archive object.
 */
struct archive *
archive_read_new(void)
{
  struct archive_read *a;

  a = 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);
  if (a->entry == NULL) {
    free(a);
    return (NULL);
  }
  a->archive.vtable = &archive_read_vtable;
  a->entry_bytes_declared = -1;

  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, la_int64_t d,
    la_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)
{
  int r;

  /* 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);
  r = archive_read_set_callback_data(a, client_data);
  if (r < 0)
    return (r);
  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)
{
  int r;

  /* Old archive_read_open2() is just a thin shell around
   * archive_read_open1. */
  r = archive_read_set_callback_data(a, client_data);
  if (r < 0)
    return (r);
  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 int
client_switch_proxy(struct archive_read_filter *f, unsigned int iindex)
{
  struct archive_read *a;
  int r1 = ARCHIVE_OK, r2 = ARCHIVE_OK;
  void *data2;

  a = f->archive;

  /* Don't do anything if already in the specified data node */
  if (a->client.cursor == iindex)
    return (ARCHIVE_OK);

  a->client.cursor = iindex;
  data2 = a->client.dataset[a->client.cursor].data;
  if (a->client.switcher != NULL)
  {
    r1 = r2 = (a->client.switcher)
      ((struct archive *)a, f->data, data2);
    f->data = data2;
  }
  else
  {
    /* Attempt to call close and open instead */
    if (a->client.closer != NULL)
      r1 = (a->client.closer)
        ((struct archive *)a, f->data);
    f->data = data2;
    if (a->client.opener != NULL)
      r2 = (a->client.opener)
        ((struct archive *)a, f->data);
  }
  f->client_total = f->client_avail = 0;
  return (r1 < r2) ? r1 : r2;
}

/*
 * Reads data from client.
 *
 * Automatically switches clients if end of file of a client is reached.
 * This simplifies handling of multi volume archives for readers.
 */
static ssize_t
client_read_proxy(struct archive_read_filter *f, const void **buff)
{
  ssize_t bytes_read = 0;

  for (;;) {
    bytes_read = (f->archive->client.reader)(&f->archive->archive,
        f->data, buff);
    if (bytes_read == 0) {
      unsigned int cursor = f->archive->client.cursor;

      /* Continue with next client object if available. */
      if (cursor != f->archive->client.nodes - 1 &&
          client_switch_proxy(f, cursor + 1) == ARCHIVE_OK)
        continue;
    }
    break;
  }

  return (bytes_read);
}

static int64_t
client_skip_proxy(struct archive_read_filter *f, int64_t request)
{
  return (f->archive->client.skipper)(&f->archive->archive,
      f->data, request);
}

static int64_t
client_seek_proxy(struct archive_read_filter *f, 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.
   */
  return (f->archive->client.seeker)(&f->archive->archive,
      f->data, offset, whence);
}

static int
client_close_proxy(struct archive_read_filter *f)
{
  struct archive_read *a = f->archive;
  int r = ARCHIVE_OK, r2;
  unsigned int i;

  if (a->client.closer == NULL)
    return (r);
  for (i = 0; i < a->client.nodes; i++)
  {
    r2 = (a->client.closer)
      ((struct archive *)a, a->client.dataset[i].data);
    if (r > r2)
      r = r2;
  }
  return (r);
}

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;
  size_t alloc_size;
  unsigned int i;
  unsigned int nodes;

  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;
  }

  if (a->client.nodes == UINT_MAX ||
      archive_ckd_mul_size(&alloc_size,
      (size_t)a->client.nodes + 1, sizeof(*a->client.dataset))) {
    archive_set_error(&a->archive, ENOMEM,
      "No memory");
    return ARCHIVE_FATAL;
  }

  nodes = a->client.nodes + 1;
  p = realloc(a->client.dataset, alloc_size);
  if (p == NULL) {
    archive_set_error(&a->archive, ENOMEM,
      "No memory");
    return ARCHIVE_FATAL;
  }

  a->client.dataset = (struct archive_read_data_node *)p;
  a->client.nodes = nodes;

  for (i = a->client.nodes - 1; i > iindex; 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);
}

static const struct archive_read_filter_vtable
none_reader_vtable = {
  .read = client_read_proxy,
  .close = client_close_proxy,
};

int
archive_read_open1(struct archive *_a)
{
  struct archive_read *a = (struct archive_read *)_a;
  struct archive_read_filter *f, *tmp;
  int slot, e = ARCHIVE_OK;

  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);
  }

  a->archive.state = ARCHIVE_STATE_OPEN;

  f = calloc(1, sizeof(*f));
  if (f == NULL) {
    a->archive.state = ARCHIVE_STATE_FATAL;
    return (ARCHIVE_FATAL);
  }
  f->bidder = NULL;
  f->upstream = NULL;
  f->archive = a;
  f->data = a->client.dataset[0].data;
  f->vtable = &none_reader_vtable;
  f->name = "none";
  f->code = ARCHIVE_FILTER_NONE;
  f->can_skip = a->client.skipper != NULL;
  f->can_seek = a->client.seeker != NULL;

  /* Open data source. */
  if (a->client.opener != NULL) {
    e = (a->client.opener)(&a->archive, a->client.dataset[0].data);
    if (e != ARCHIVE_OK) {
      /* If the open failed, call the closer to clean up. */
      client_close_proxy(f);
      free(f);
      a->archive.state = ARCHIVE_STATE_FATAL;
      return (e);
    }
  }

  a->client.dataset[0].begin_position = 0;
  if (!a->filter || !a->bypass_filter_bidding)
  {
    a->filter = f;
    /* 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 = f;
  }

  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]);
  }
  else if (a->format->bid != NULL)
  {
    if (bid_format(a, -1) < 0) {
      archive_set_error(&a->archive,
          ARCHIVE_ERRNO_FILE_FORMAT,
          "Registered format does not match");
      close_filters(a);
      a->archive.state = ARCHIVE_STATE_FATAL;
      return (ARCHIVE_FATAL);
    }
  }

  a->archive.state = ARCHIVE_STATE_HEADER;

  /* Ensure libarchive starts from the first node in a multivolume set */
  client_switch_proxy(f, 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 *f;
  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->vtable == NULL)
        continue;
      bid = (bidder->vtable->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);
      }
      return (ARCHIVE_OK);
    }

    f = calloc(1, sizeof(*f));
    if (f == NULL)
      return (ARCHIVE_FATAL);
    f->bidder = best_bidder;
    f->archive = a;
    f->upstream = a->filter;
    a->filter = f;
    r = (best_bidder->vtable->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);
}

int
__archive_read_header(struct archive_read *a, struct archive_entry *entry)
{
  if (!a->filter->vtable->read_header)
    return (ARCHIVE_OK);
  return a->filter->vtable->read_header(a->filter, entry);
}

/*
 * 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_STATE_DATA_RECOVERY,
      "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.)
   * A header that failed to parse (DATA_RECOVERY) still needs the
   * same treatment: whatever of its body the format reader left
   * unconsumed must be skipped before we can read the next header.
   */
  if (a->archive.state == ARCHIVE_STATE_DATA ||
      a->archive.state == ARCHIVE_STATE_DATA_RECOVERY) {
    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;
  case ARCHIVE_FAILED:
    /*
     * This entry's header could not be parsed, so its metadata
     * cannot be trusted.  ARCHIVE_STATE_DATA_RECOVERY still
     * permits skipping past it (the format reader is
     * responsible for ensuring that's actually possible), but
     * blocks archive_read_data() and friends, which all check
     * for ARCHIVE_STATE_DATA specifically and would otherwise
     * return content for an entry we don't actually understand.
     */
    a->archive.state = ARCHIVE_STATE_DATA_RECOVERY;
    break;
  }

  if (r2 == ARCHIVE_OK || r2 == ARCHIVE_WARN)
    a->entry_bytes_declared = archive_entry_size_is_set(entry)
        ? archive_entry_size(entry) : -1;
  else
    a->entry_bytes_declared = -1;

  __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;
}

static int
bid_format(struct archive_read *a, int best_bid)
{
  int 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) < 0)
    return (ARCHIVE_FATAL);

  return (bid);
}

/*
 * 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 = bid_format(a, best_bid);
      if (bid == ARCHIVE_FATAL)
        return (ARCHIVE_FATAL);
      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.
 */
la_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 does 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.
 */
la_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_offset == a->read_data_output_offset &&
        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 &&
          a->read_data_offset == a->read_data_output_offset &&
          a->read_data_remaining == 0)
        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;
      if (len) {
        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_STATE_DATA_RECOVERY,
      "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;

  if (r == ARCHIVE_FATAL)
    a->archive.state = ARCHIVE_STATE_FATAL;
  else
    a->archive.state = ARCHIVE_STATE_HEADER;
  return (r);
}

la_int64_t
archive_seek_data(struct archive *_a, int64_t offset, int whence)
{
  struct archive_read *a = (struct archive_read *)_a;
  la_int64_t r;

  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_MISC,
        "Cannot seek data with this format");
    return (ARCHIVE_FAILED);
  }

  r = (a->format->seek_data)(a, offset, whence);
  if (r == ARCHIVE_FATAL)
    a->archive.state = ARCHIVE_STATE_FATAL;
  return (r);
}

/*
 * 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;
  int r;

  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");
    a->archive.state = ARCHIVE_STATE_FATAL;
    return (ARCHIVE_FATAL);
  }

  r = (a->format->read_data)(a, buff, size, offset);
  if (r == ARCHIVE_FATAL)
    a->archive.state = ARCHIVE_STATE_FATAL;
  return (r);
}

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->vtable != NULL) {
      int r1 = (f->vtable->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].vtable == NULL ||
        a->bidders[i].vtable->free == NULL)
      continue;
    (a->bidders[i].vtable->free)(&a->bidders[i]);
  }

  /* 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_register_bidder(struct archive_read *a,
  void *bidder_data,
  const struct archive_read_filter_bidder_vtable *vtable)
{
  struct archive_read_filter_bidder *bidder;
  int i, number_slots;

  archive_check_magic(&a->archive, ARCHIVE_READ_MAGIC,
      ARCHIVE_STATE_NEW, "__archive_read_register_bidder");

  number_slots = sizeof(a->bidders) / sizeof(a->bidders[0]);

  for (i = 0; i < number_slots; i++) {
    if (a->bidders[i].vtable != NULL)
      continue;
    memset(a->bidders + i, 0, sizeof(a->bidders[0]));
    bidder = (a->bidders + i);
    bidder->data = bidder_data;
    bidder->vtable = vtable;
    if (bidder->vtable->bid == NULL || bidder->vtable->init == NULL) {
      archive_set_error(&a->archive, ARCHIVE_ERRNO_PROGRAMMER,
          "Internal error: "
          "no bid/init for filter bidder");
      return (ARCHIVE_FATAL);
    }

    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.
 */

/*
 * Reads data into client buffer.
 *
 * In case of error or end of file, filter flags are set.
 * Client buffer related fields are updated.
 */
static ssize_t
read_client_data(struct archive_read_filter *f)
{
  ssize_t bytes_read;

  if (f->end_of_file)
    return (0);

  bytes_read = (f->vtable->read)(f, &f->client_buff);
  if (bytes_read < 0) {
    f->client_total = f->client_avail = 0;
    f->client_next = f->client_buff = NULL;
    f->fatal = 1;
  } else if (bytes_read == 0) {
    f->client_total = f->client_avail = 0;
    f->client_next = f->client_buff = NULL;
    f->end_of_file = 1;
  } else {
    f->client_total = bytes_read;
    f->client_avail = f->client_total;
    f->client_next = f->client_buff;
  }

  return (bytes_read);
}

/*
 * 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 *f,
    size_t request, ssize_t *avail)
{
  ssize_t bytes_read;
  size_t min, tocopy;

  if (f->fatal) {
    if (avail)
      *avail = ARCHIVE_FATAL;
    return (NULL);
  }
  /* request == 0 is perfectly well-defined.*/
  min = request == 0 ? 1 : request;

  /*
   * Keep pulling more data until we can satisfy the request.
   */
  for (;;) {

    /*
     * We can satisfy directly from client buffer if everything
     * currently in the copy buffer is still in the client buffer.
     */
    if (f->client_total >= f->client_avail + f->avail
        && f->client_avail + f->avail >= min) {
      /* "Roll back" to client buffer. */
      f->client_avail += f->avail;
      f->client_next -= f->avail;
      /* Copy buffer is now empty. */
      f->avail = 0;
      f->next = f->buffer;
      /* Return data from client buffer. */
      if (avail != NULL)
        *avail = f->client_avail;
      return (f->client_next);
    }

    /* If we can satisfy from the copy buffer, we're done. */
    if (f->avail >= min) {
      if (avail != NULL)
        *avail = f->avail;
      return (f->next);
    }

    /* If we've used up the client data, get more. */
    if (f->client_avail <= 0) {
      bytes_read = read_client_data(f);
      if (bytes_read < 0) {
        /* Read error. */
        if (avail != NULL)
          *avail = ARCHIVE_FATAL;
        return (NULL);
      }
      if (bytes_read == 0) {
        static const char *empty = "";
        const char *eof;

        /* Premature end-of-file.
         * Return whatever we do have. */
        if (avail != NULL)
          *avail = f->avail;
        if (request == 0)
          eof = f->avail == 0 ? empty : f->next;
        else
          eof = NULL;
        return (eof);
      }
    } 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 > f->buffer_size) {
        size_t s;
        char *p;

        /* Double the buffer; watch for overflow. */
        s = f->buffer_size;
        if (s == 0)
          s = min;
        while (s < min) {
          if (archive_ckd_mul_size(&s, s, 2)) {
            /* Integer overflow! */
            archive_set_error(
                &f->archive->archive,
                ENOMEM,
                "Unable to allocate copy"
                " buffer");
            f->fatal = 1;
            if (avail != NULL)
              *avail = ARCHIVE_FATAL;
            return (NULL);
          }
        }
        /* Now s >= min, so allocate a new buffer. */
        p = malloc(s);
        if (p == NULL) {
          archive_set_error(
            &f->archive->archive,
            ENOMEM,
              "Unable to allocate copy buffer");
          f->fatal = 1;
          if (avail != NULL)
            *avail = ARCHIVE_FATAL;
          return (NULL);
        }
        /* Move data into newly-enlarged buffer. */
        if (f->avail > 0)
          memcpy(p, f->next, f->avail);
        free(f->buffer);
        f->next = f->buffer = p;
        f->buffer_size = s;
      } else if (f->next > f->buffer &&
          min > f->buffer_size - (f->next - f->buffer)) {
        /* Move data forward in copy buffer
         * if necessary. */
        if (f->avail > 0)
          memmove(f->buffer, f->next,
              f->avail);
        f->next = f->buffer;
      }

      /* We can add client data to copy buffer. */
      /* Don't waste time buffering more than we need to. */
      tocopy = min - f->avail;
      /* Don't copy more than is available. */
      if (tocopy > f->client_avail)
        tocopy = f->client_avail;

      memcpy(f->next + f->avail,
          f->client_next, tocopy);
      /* Remove this data from client buffer. */
      f->client_next += tocopy;
      f->client_avail -= tocopy;
      /* add it to copy buffer. */
      f->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 *f,
    int64_t request)
{
  int64_t skipped;

  if (request < 0)
    return ARCHIVE_FATAL;
  if (request == 0)
    return 0;

  skipped = advance_file_pointer(f, 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(&f->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 *f, int64_t request)
{
  int64_t total_bytes_skipped = 0;

  if (f->fatal)
    return (-1);

  /* Use up the copy buffer first. */
  if (f->avail > 0) {
    size_t min = (size_t)minimum(request, (int64_t)f->avail);
    f->next += min;
    f->avail -= min;
    request -= min;
    f->position += min;
    total_bytes_skipped += min;
  }

  /* Then use up the client buffer. */
  if (f->client_avail > 0) {
    size_t min = (size_t)minimum(request, (int64_t)f->client_avail);
    f->client_next += min;
    f->client_avail -= min;
    request -= min;
    f->position += min;
    total_bytes_skipped += min;
  }
  if (request == 0)
    return (total_bytes_skipped);

  /* If there's an optimized skip function, use it. */
  if (f->can_skip != 0) {
    while (request > 0) {
      int64_t get = client_skip_proxy(f, request);
      if (get < 0 || get > request) {
        f->fatal = 1;
        return (ARCHIVE_FATAL);
      }
      if (get == 0)
        break;
      f->position += get;
      total_bytes_skipped += get;
      request -= get;
    }
    if (request == 0)
      return (total_bytes_skipped);
  } else if (f->can_seek != 0 && 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 bytes_skipped;
    int64_t before = f->position;
    int64_t after = __archive_read_filter_seek(f,
        request, SEEK_CUR);
    if (after != before + request) {
      f->fatal = 1;
      return (ARCHIVE_FATAL);
    }
    bytes_skipped = after - before;
    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 (;;) {
    ssize_t bytes_read = read_client_data(f);
    if (bytes_read < 0)
      return (bytes_read);

    if (bytes_read == 0)
      return (total_bytes_skipped);

    if (bytes_read >= request) {
      f->client_next += request;
      f->client_avail -= request;
      total_bytes_skipped += request;
      f->position += request;
      return (total_bytes_skipped);
    }

    f->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 *f, int64_t offset,
    int whence)
{
  struct archive_read_client *client;
  int64_t r;
  unsigned int cursor, old_cursor;
  int sought = 0;

  if (f->closed || f->fatal)
    return (ARCHIVE_FATAL);
  if (f->can_seek == 0)
    return (ARCHIVE_FAILED);

  client = &(f->archive->client);
  old_cursor = client->cursor;

  switch (whence) {
  case SEEK_CUR:
    /* Adjust the offset and use SEEK_SET instead */
    offset += f->position;
    __LA_FALLTHROUGH;
  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 > 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(f, cursor);
      if (r != ARCHIVE_OK)
        goto clear_buffer;
      if ((r = client_seek_proxy(f, 0, SEEK_END)) < 0)
        goto clear_buffer;
      sought = 1;
      client->dataset[cursor].total_size = r;
      if (client->dataset[cursor].begin_position +
          client->dataset[cursor].total_size > 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) {
      r = ARCHIVE_FATAL;
      goto clear_buffer;
    }
    if ((r = client_seek_proxy(f, offset, SEEK_SET)) < 0)
      goto clear_buffer;
    sought = 1;
    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(f, cursor);
      if (r != ARCHIVE_OK)
        goto clear_buffer;
      if ((r = client_seek_proxy(f, 0, SEEK_END)) < 0)
        goto clear_buffer;
      sought = 1;
      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(f, cursor)) != ARCHIVE_OK)
      goto clear_buffer;
    r = client_seek_proxy(f, offset, SEEK_SET);
    if (r < ARCHIVE_OK)
      goto clear_buffer;
    sought = 1;
    break;

  default:
    return (ARCHIVE_FATAL);
  }
  r += client->dataset[cursor].begin_position;

clear_buffer:
  if (r == ARCHIVE_FAILED && !sought && old_cursor == client->cursor) {
    /* Seek failed without moving position: keep buffer */
    return (r);
  }

  /*
   * 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?
  */
  f->avail = f->client_avail = 0;
  f->next = f->buffer;
  if (r >= 0) {
    f->position = r;
    f->end_of_file = 0;
  } else
    f->fatal = 1;

  return r;
}

Coverage Report

Created: 2026-10-10 07:18