man/zip_source_function.html

<!DOCTYPE html>
<html>
<!-- This is an automatically generated file.  Do not edit.
   zip_source_function.mdoc -- create data source from function
   Copyright (C) 2004-2021 Dieter Baron and Thomas Klausner
  
   This file is part of libzip, a library to manipulate ZIP archives.
   The authors can be contacted at <libzip@nih.at>
  
   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions
   are met:
   1. Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
   2. Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in
      the documentation and/or other materials provided with the
      distribution.
   3. The names of the authors may not be used to endorse or promote
      products derived from this software without specific prior
      written permission.
  
   THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``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 AUTHORS 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.
   -->
<head>
  <meta charset="utf-8"/>
  <link rel="stylesheet" href="../nih-man.css" type="text/css" media="all"/>
  <title>ZIP_SOURCE_FUNCTION(3)</title>
</head>
<body>
<table class="head">
  <tr>
    <td class="head-ltitle">ZIP_SOURCE_FUNCTION(3)</td>
    <td class="head-vol">Library Functions Manual</td>
    <td class="head-rtitle">ZIP_SOURCE_FUNCTION(3)</td>
  </tr>
</table>
<div class="manual-text">
<section class="Sh">
<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1>
<code class="Nm">zip_source_function</code>,
  <code class="Nm">zip_source_function_create</code> &#x2014;
<div class="Nd">create data source from function</div>
</section>
<section class="Sh">
<h1 class="Sh" id="LIBRARY"><a class="permalink" href="#LIBRARY">LIBRARY</a></h1>
libzip (-lzip)
</section>
<section class="Sh">
<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1>
<code class="In">#include &lt;<a class="In">zip.h</a>&gt;</code>
<p class="Pp"><var class="Ft">zip_source_t *</var>
  <br/>
  <code class="Fn">zip_source_function</code>(<var class="Fa" style="white-space: nowrap;">zip_t
    *archive</var>,
    <var class="Fa" style="white-space: nowrap;">zip_source_callback fn</var>,
    <var class="Fa" style="white-space: nowrap;">void *userdata</var>);</p>
<p class="Pp"><var class="Ft">zip_source_t *</var>
  <br/>
  <code class="Fn">zip_source_function_create</code>(<var class="Fa" style="white-space: nowrap;">zip_source_callback
    fn</var>, <var class="Fa" style="white-space: nowrap;">void *userdata</var>,
    <var class="Fa" style="white-space: nowrap;">zip_error_t *error</var>);</p>
</section>
<section class="Sh">
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
The functions <code class="Fn">zip_source_function</code>() and
  <code class="Fn">zip_source_function_create</code>() creates a zip source from
  the user-provided function <var class="Ar">fn</var>, which must be of the
  following type:
<p class="Pp"><var class="Ft">typedef zip_int64_t</var>
    <code class="Fn">(*zip_source_callback)</code>(<var class="Fa">void
    *userdata</var>, <var class="Fa">void *data</var>,
    <var class="Fa">zip_uint64_t len</var>, <var class="Fa">zip_source_cmd_t
    cmd</var>);</p>
<p class="Pp"><var class="Ar">archive</var> or <var class="Ar">error</var> are
    used for reporting errors and can be <code class="Dv">NULL</code>.</p>
<p class="Pp">When called by the library, the first argument is the
    <var class="Ar">userdata</var> argument supplied to the function. The next
    two arguments are a buffer <var class="Ar">data</var> of size
    <var class="Ar">len</var> when data is passed in or expected to be returned,
    or else <code class="Dv">NULL</code> and 0. The last argument,
    <var class="Ar">cmd</var>, specifies which action the function should
    perform.</p>
<p class="Pp">Depending on the uses, there are three useful sets of commands to
    be supported by a <code class="Fn">zip_source_callback</code>():</p>
<dl class="Bl-tag">
  <dt>read source</dt>
  <dd>Providing streamed data (for file data added to archives). Must support
      <code class="Dv">ZIP_SOURCE_OPEN</code>,
      <code class="Dv">ZIP_SOURCE_READ</code>,
      <code class="Dv">ZIP_SOURCE_CLOSE</code>,
      <code class="Dv">ZIP_SOURCE_STAT</code>, and
      <code class="Dv">ZIP_SOURCE_ERROR</code>.</dd>
  <dt>seekable read source</dt>
  <dd>Same as previous, but from a source allowing reading from arbitrary
      offsets (also for read-only zip archive). Must additionally support
      <code class="Dv">ZIP_SOURCE_SEEK</code>,
      <code class="Dv">ZIP_SOURCE_TELL</code>, and
      <code class="Dv">ZIP_SOURCE_SUPPORTS</code>.</dd>
  <dt>read/write source</dt>
  <dd>Same as previous, but additionally allowing writing (also for writable zip
      archives). Must additionally support
      <code class="Dv">ZIP_SOURCE_BEGIN_WRITE</code>,
      <code class="Dv">ZIP_SOURCE_COMMIT_WRITE</code>,
      <code class="Dv">ZIP_SOURCE_ROLLBACK_WRITE</code>,
      <code class="Dv">ZIP_SOURCE_SEEK_WRITE</code>,
      <code class="Dv">ZIP_SOURCE_TELL_WRITE</code>, and
      <code class="Dv">ZIP_SOURCE_REMOVE</code>.</dd>
</dl>
<section class="Ss">
<h2 class="Ss"><code class="Dv">ZIP_SOURCE_ACCEPT_EMPTY</code></h2>
Return 1 if an empty source should be accepted as a valid zip archive. This is
  the default if this command is not supported by a source. File system backed
  sources should return 0.
</section>
<section class="Ss">
<h2 class="Ss"><code class="Dv">ZIP_SOURCE_BEGIN_WRITE</code></h2>
Prepare the source for writing. Use this to create any temporary file(s).
</section>
<section class="Ss">
<h2 class="Ss"><code class="Dv">ZIP_SOURCE_BEGIN_WRITE_CLONING</code></h2>
Prepare the source for writing, keeping the first <var class="Ar">len</var>
  bytes of the original file. Only implement this command if it is more
  efficient than copying the data, and if it does not destructively overwrite
  the original file (you still have to be able to execute
  <code class="Dv">ZIP_SOURCE_ROLLBACK_WRITE</code>).
<p class="Pp">The next write should happen at byte
  <var class="Ar">offset</var>.</p>
</section>
<section class="Ss">
<h2 class="Ss"><code class="Dv">ZIP_SOURCE_CLOSE</code></h2>
Reading is done.
</section>
<section class="Ss">
<h2 class="Ss"><code class="Dv">ZIP_SOURCE_COMMIT_WRITE</code></h2>
Finish writing to the source. Replace the original data with the newly written
  data. Clean up temporary files or internal buffers. Subsequently opening and
  reading from the source should return the newly written data.
</section>
<section class="Ss">
<h2 class="Ss"><code class="Dv">ZIP_SOURCE_ERROR</code></h2>
Get error information. <var class="Ar">data</var> points to an array of two
  ints, which should be filled with the libzip error code and the corresponding
  system error code for the error that occurred. See
  <a class="Xr" href="zip_errors.html">zip_errors(3)</a> for details on the
  error codes. If the source stores error information in a zip_error_t, use
  <a class="Xr" href="zip_error_to_data.html">zip_error_to_data(3)</a> and
  return its return value. Otherwise, return 2 * sizeof(int).
</section>
<section class="Ss">
<h2 class="Ss"><code class="Dv">ZIP_SOURCE_FREE</code></h2>
Clean up and free all resources, including <var class="Ar">userdata</var>. The
  callback function will not be called again.
</section>
<section class="Ss">
<h2 class="Ss"><code class="Dv">ZIP_SOURCE_GET_FILE_ATTRIBUTES</code></h2>
Provide information about various data. Then the data should be put in the
  appropriate entry in the passed <var class="Vt">zip_file_attributes_t</var>
  argument, and the appropriate <code class="Dv">ZIP_FILE_ATTRIBUTES_*</code>
  value must be or'ed into the <var class="Ar">valid</var> member to denote that
  the corresponding data has been provided. A
  <var class="Vt">zip_file_attributes_t</var> structure can be initialized using
  <a class="Xr" href="zip_file_attributes_init.html">zip_file_attributes_init(3)</a>.
<dl class="Bl-tag">
  <dt>ASCII mode</dt>
  <dd>If a file is a plaintext file in ASCII. Can be used by extraction tools to
      automatically convert line endings (part of the interal file attributes).
      Member <var class="Ar">ascii</var>, flag
      <code class="Dv">ZIP_FILE_ATTRIBUTES_ASCII</code>.</dd>
  <dt>General Purpose Bit Flags (limited to Compression Flags)</dt>
  <dd>The general purpose bit flag in the zip in the local and central directory
      headers contain information about the compression method. Member
      <var class="Ar">general_purpose_bit_flags</var> and
      <var class="Ar">general_purpose_bit_mask</var> to denote which members
      have been set; flag
      <code class="Dv">ZIP_FILE_ATTRIBUTES_GENERAL_PURPOSE_BIT_FLAGS</code>.</dd>
  <dt>External File Attributes</dt>
  <dd>The external file attributes (usually operating system-specific). Member
      <var class="Ar">external_file_attributes</var>, flag
      <code class="Dv">ZIP_FILE_ATTRIBUTES_EXTERNAL_FILE_ATTRIBUTES</code>.</dd>
  <dt>Version Needed</dt>
  <dd>A minimum version needed required to unpack this entry (in the usual
      &quot;major * 10 + minor&quot; format). Member
      <var class="Ar">version_needed</var>, flag
      <code class="Dv">ZIP_FILE_ATTRIBUTES_VERSION_NEEDED</code>.</dd>
  <dt>Operating System</dt>
  <dd>One of the operating systems as defined by the
      <code class="Dv">ZIP_OPSYS_*</code> variables (see
      <span class="Pa">zip.h</span>). This value affects the interpretation of
      the external file attributes. Member <var class="Ar">host_system</var>,
      flag <code class="Dv">ZIP_FILE_ATTRIBUTES_HOST_SYSTEM</code>.</dd>
</dl>
</section>
<section class="Ss">
<h2 class="Ss"><code class="Dv">ZIP_SOURCE_OPEN</code></h2>
Prepare for reading.
</section>
<section class="Ss">
<h2 class="Ss"><code class="Dv">ZIP_SOURCE_READ</code></h2>
Read data into the buffer <var class="Ar">data</var> of size
  <var class="Ar">len</var>. Return the number of bytes placed into
  <var class="Ar">data</var> on success, and zero for end-of-file.
</section>
<section class="Ss">
<h2 class="Ss"><code class="Dv">ZIP_SOURCE_REMOVE</code></h2>
Remove the underlying file. This is called if a zip archive is empty when
  closed.
</section>
<section class="Ss">
<h2 class="Ss"><code class="Dv">ZIP_SOURCE_ROLLBACK_WRITE</code></h2>
Abort writing to the source. Discard written data. Clean up temporary files or
  internal buffers. Subsequently opening and reading from the source should
  return the original data.
</section>
<section class="Ss">
<h2 class="Ss"><code class="Dv">ZIP_SOURCE_SEEK</code></h2>
Specify position to read next byte from, like
  <a class="Xr" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/fseek.html">fseek(3)</a>. Use
  <a class="Xr" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/ZIP_SOURCE_GET_ARGS.html">ZIP_SOURCE_GET_ARGS(3)</a> to
  decode the arguments into the following struct:
<div class="Bd Pp">
<pre>
struct zip_source_args_seek {
    zip_int64_t offset;
    int whence;
};
</pre>
</div>
<p class="Pp">If the size of the source's data is known, use
    <a class="Xr" href="zip_source_seek_compute_offset.html">zip_source_seek_compute_offset(3)</a>
    to validate the arguments and compute the new offset.</p>
</section>
<section class="Ss">
<h2 class="Ss"><code class="Dv">ZIP_SOURCE_SEEK_WRITE</code></h2>
Specify position to write next byte to, like
  <a class="Xr" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/fseek.html">fseek(3)</a>. See
  <code class="Dv">ZIP_SOURCE_SEEK</code> for details.
</section>
<section class="Ss">
<h2 class="Ss"><code class="Dv">ZIP_SOURCE_STAT</code></h2>
Get meta information for the input data. <var class="Ar">data</var> points to an
  allocated <var class="Vt">struct zip_stat</var>, which should be initialized
  using <a class="Xr" href="zip_stat_init.html">zip_stat_init(3)</a> and then
  filled in.
<p class="Pp">For uncompressed, unencrypted data, all information is optional.
    However, fill in as much information as is readily available.</p>
<p class="Pp">If the data is compressed,
    <code class="Dv">ZIP_STAT_COMP_METHOD</code>,
    <code class="Dv">ZIP_STAT_SIZE</code>, and
    <code class="Dv">ZIP_STAT_CRC</code> must be filled in.</p>
<p class="Pp">If the data is encrypted,
    <code class="Dv">ZIP_STAT_ENCRYPTION_METHOD</code>,
    <code class="Dv">ZIP_STAT_COMP_METHOD</code>,
    <code class="Dv">ZIP_STAT_SIZE</code>, and
    <code class="Dv">ZIP_STAT_CRC</code> must be filled in.</p>
<p class="Pp">Information only available after the source has been read (e.g.,
    size) can be omitted in an earlier call. <i class="Em">NOTE</i>:
    <code class="Fn">zip_source_function</code>() may be called with this
    argument even after being called with
    <code class="Dv">ZIP_SOURCE_CLOSE</code>.</p>
<p class="Pp">Return sizeof(struct zip_stat) on success.</p>
</section>
<section class="Ss">
<h2 class="Ss"><code class="Dv">ZIP_SOURCE_SUPPORTS</code></h2>
Return bitmap specifying which commands are supported. Use
  <a class="Xr" href="zip_source_make_command_bitmap.html">zip_source_make_command_bitmap(3)</a>.
  If this command is not implemented, the source is assumed to be a read source
  without seek support.
</section>
<section class="Ss">
<h2 class="Ss"><code class="Dv">ZIP_SOURCE_TELL</code></h2>
Return the current read offset in the source, like
  <a class="Xr" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/ftell.html">ftell(3)</a>.
</section>
<section class="Ss">
<h2 class="Ss"><code class="Dv">ZIP_SOURCE_TELL_WRITE</code></h2>
Return the current write offset in the source, like
  <a class="Xr" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/ftell.html">ftell(3)</a>.
</section>
<section class="Ss">
<h2 class="Ss"><code class="Dv">ZIP_SOURCE_WRITE</code></h2>
Write data to the source. Return number of bytes written.
</section>
<section class="Ss">
<h2 class="Ss" id="Return_Values"><a class="permalink" href="#Return_Values">Return
  Values</a></h2>
Commands should return -1 on error. <code class="Dv">ZIP_SOURCE_ERROR</code>
  will be called to retrieve the error code. On success, commands return 0,
  unless specified otherwise in the description above.
</section>
<section class="Ss">
<h2 class="Ss" id="Calling_Conventions"><a class="permalink" href="#Calling_Conventions">Calling
  Conventions</a></h2>
The library will always issue <code class="Dv">ZIP_SOURCE_OPEN</code> before
  issuing <code class="Dv">ZIP_SOURCE_READ</code>,
  <code class="Dv">ZIP_SOURCE_SEEK</code>, or
  <code class="Dv">ZIP_SOURCE_TELL</code>. When it no longer wishes to read from
  this source, it will issue <code class="Dv">ZIP_SOURCE_CLOSE</code>. If the
  library wishes to read the data again, it will issue
  <code class="Dv">ZIP_SOURCE_OPEN</code> a second time. If the function is
  unable to provide the data again, it should return -1.
<p class="Pp"><code class="Dv">ZIP_SOURCE_BEGIN_WRITE</code> or
    <code class="Dv">ZIP_SOURCE_BEGIN_WRITE_CLONING</code> will be called before
    <code class="Dv">ZIP_SOURCE_WRITE</code>,
    <code class="Dv">ZIP_SOURCE_SEEK_WRITE</code>, or
    <code class="Dv">ZIP_SOURCE_TELL_WRITE</code>. When writing is complete,
    either <code class="Dv">ZIP_SOURCE_COMMIT_WRITE</code> or
    <code class="Dv">ZIP_SOURCE_ROLLBACK_WRITE</code> will be called.</p>
<p class="Pp"><code class="Dv">ZIP_SOURCE_ACCEPT_EMPTY</code>,
    <code class="Dv">ZIP_SOURCE_GET_FILE_ATTRIBUTES</code>, and
    <code class="Dv">ZIP_SOURCE_STAT</code> can be issued at any time.</p>
<p class="Pp"><code class="Dv">ZIP_SOURCE_ERROR</code> will only be issued in
    response to the function returning -1.</p>
<p class="Pp"><code class="Dv">ZIP_SOURCE_FREE</code> will be the last command
    issued; if <code class="Dv">ZIP_SOURCE_OPEN</code> was called and succeeded,
    <code class="Dv">ZIP_SOURCE_CLOSE</code> will be called before
    <code class="Dv">ZIP_SOURCE_FREE</code>, and similarly for
    <code class="Dv">ZIP_SOURCE_BEGIN_WRITE</code> or
    <code class="Dv">ZIP_SOURCE_BEGIN_WRITE_CLONING</code> and
    <code class="Dv">ZIP_SOURCE_COMMIT_WRITE</code> or
    <code class="Dv">ZIP_SOURCE_ROLLBACK_WRITE</code>.</p>
</section>
</section>
<section class="Sh">
<h1 class="Sh" id="RETURN_VALUES"><a class="permalink" href="#RETURN_VALUES">RETURN
  VALUES</a></h1>
Upon successful completion, the created source is returned. Otherwise,
  <code class="Dv">NULL</code> is returned and the error code in
  <var class="Ar">archive</var> or <var class="Ar">error</var> is set to
  indicate the error (unless it is <code class="Dv">NULL</code>).
</section>
<section class="Sh">
<h1 class="Sh" id="ERRORS"><a class="permalink" href="#ERRORS">ERRORS</a></h1>
<code class="Fn">zip_source_function</code>() fails if:
<dl class="Bl-tag">
  <dt>[<a class="permalink" href="#ZIP_ER_MEMORY"><code class="Er" id="ZIP_ER_MEMORY">ZIP_ER_MEMORY</code></a>]</dt>
  <dd>Required memory could not be allocated.</dd>
</dl>
</section>
<section class="Sh">
<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE
  ALSO</a></h1>
<a class="Xr" href="libzip.html">libzip(3)</a>,
  <a class="Xr" href="zip_file_add.html">zip_file_add(3)</a>,
  <a class="Xr" href="zip_file_attributes_init.html">zip_file_attributes_init(3)</a>,
  <a class="Xr" href="zip_file_replace.html">zip_file_replace(3)</a>,
  <a class="Xr" href="zip_source.html">zip_source(3)</a>,
  <a class="Xr" href="zip_stat_init.html">zip_stat_init(3)</a>
</section>
<section class="Sh">
<h1 class="Sh" id="HISTORY"><a class="permalink" href="#HISTORY">HISTORY</a></h1>
<code class="Fn">zip_source_function</code>() and
  <code class="Fn">zip_source_function_create</code>() were added in libzip 1.0.
</section>
<section class="Sh">
<h1 class="Sh" id="AUTHORS"><a class="permalink" href="#AUTHORS">AUTHORS</a></h1>
<span class="An">Dieter Baron</span>
  &lt;<a class="Mt" href="mailto:dillo@nih.at">dillo@nih.at</a>&gt; and
  <span class="An">Thomas Klausner</span>
  &lt;<a class="Mt" href="mailto:tk@giga.or.at">tk@giga.or.at</a>&gt;
</section>
</div>
<table class="foot">
  <tr>
    <td class="foot-date">April 17, 2020</td>
    <td class="foot-os">NiH</td>
  </tr>
</table>
</body>
</html>