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zip_source_function.mdoc -- create data source from function
Copyright (C) 2004-2017 Dieter Baron and Thomas Klausner
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<head>
<meta charset="utf-8"/>
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<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">
<h1 class="Sh" title="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1>
<code class="Nm" title="Nm">zip_source_function</code>,
<code class="Nm" title="Nm">zip_source_function_create</code> &#x2014;
<div class="Nd" title="Nd">create data source from function</div>
<h1 class="Sh" title="Sh" id="LIBRARY"><a class="permalink" href="#LIBRARY">LIBRARY</a></h1>
libzip (-lzip)
<h1 class="Sh" title="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1>
<code class="In" title="In">#include
&lt;<a class="In" title="In">zip.h</a>&gt;</code>
<div class="Pp"></div>
<var class="Ft" title="Ft">zip_source_t *</var>
<br/>
<code class="Fn" title="Fn">zip_source_function</code>(<var class="Fa" title="Fa" style="white-space: nowrap;">zip_t
*archive</var>,
<var class="Fa" title="Fa" style="white-space: nowrap;">zip_source_callback
fn</var>, <var class="Fa" title="Fa" style="white-space: nowrap;">void
*userdata</var>);
<div class="Pp"></div>
<var class="Ft" title="Ft">zip_source_t *</var>
<br/>
<code class="Fn" title="Fn">zip_source_function_create</code>(<var class="Fa" title="Fa" style="white-space: nowrap;">zip_source_callback
fn</var>, <var class="Fa" title="Fa" style="white-space: nowrap;">void
*userdata</var>,
<var class="Fa" title="Fa" style="white-space: nowrap;">zip_error_t
*error</var>);
<h1 class="Sh" title="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
The functions <code class="Fn" title="Fn">zip_source_function</code>() and
<code class="Fn" title="Fn">zip_source_function_create</code>() creates a zip
source from the user-provided function <var class="Ar" title="Ar">fn</var>,
which must be of the following type:
<div class="Pp"></div>
<var class="Ft" title="Ft">typedef zip_int64_t</var>
<code class="Fn" title="Fn">(*zip_source_callback)</code>(<var class="Fa" title="Fa">void
*userdata</var>, <var class="Fa" title="Fa">void *data</var>,
<var class="Fa" title="Fa">zip_uint64_t len</var>,
<var class="Fa" title="Fa">zip_source_cmd_t cmd</var>);
<div class="Pp"></div>
<var class="Ar" title="Ar">archive</var> or
<var class="Ar" title="Ar">error</var> are used for reporting errors and can
be <code class="Dv" title="Dv">NULL</code>.
<div class="Pp"></div>
When called by the library, the first argument is the
<var class="Ar" title="Ar">userdata</var> argument supplied to the function.
The next two arguments are a buffer <var class="Ar" title="Ar">data</var> of
size <var class="Ar" title="Ar">len</var> when data is passed in or expected
to be returned, or else <code class="Dv" title="Dv">NULL</code> and 0. The
last argument, <var class="Ar" title="Ar">cmd</var>, specifies which action
the function should perform.
<div class="Pp"></div>
Depending on the uses, there are three useful sets of commands to be supported
by a <code class="Fn" title="Fn">zip_source_callback</code>():
<dl class="Bl-tag">
<dt>&#x00A0;</dt>
<dd>&#x00A0;</dd>
<dt>read source</dt>
<dd>Providing streamed data (for file data added to archives). Must support
<code class="Dv" title="Dv">ZIP_SOURCE_OPEN</code>,
<code class="Dv" title="Dv">ZIP_SOURCE_READ</code>,
<code class="Dv" title="Dv">ZIP_SOURCE_CLOSE</code>,
<code class="Dv" title="Dv">ZIP_SOURCE_STAT</code>, and
<code class="Dv" title="Dv">ZIP_SOURCE_ERROR</code>.</dd>
<dt>&#x00A0;</dt>
<dd>&#x00A0;</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" title="Dv">ZIP_SOURCE_SEEK</code>,
<code class="Dv" title="Dv">ZIP_SOURCE_TELL</code>, and
<code class="Dv" title="Dv">ZIP_SOURCE_SUPPORTS</code>.</dd>
<dt>&#x00A0;</dt>
<dd>&#x00A0;</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" title="Dv">ZIP_SOURCE_BEGIN_WRITE</code>,
<code class="Dv" title="Dv">ZIP_SOURCE_COMMIT_WRITE</code>,
<code class="Dv" title="Dv">ZIP_SOURCE_ROLLBACK_WRITE</code>,
<code class="Dv" title="Dv">ZIP_SOURCE_SEEK_WRITE</code>,
<code class="Dv" title="Dv">ZIP_SOURCE_TELL_WRITE</code>, and
<code class="Dv" title="Dv">ZIP_SOURCE_REMOVE</code>.</dd>
</dl>
<h2 class="Ss" title="Ss"><code class="Dv" title="Dv">ZIP_SOURCE_BEGIN_WRITE</code></h2>
Prepare the source for writing. Use this to create any temporary file(s).
<h2 class="Ss" title="Ss"><code class="Dv" title="Dv">ZIP_SOURCE_BEGIN_WRITE_CLONING</code></h2>
Prepare the source for writing, keeping the first
<var class="Ar" title="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" title="Dv">ZIP_SOURCE_ROLLBACK_WRITE</code>).
<div class="Pp"></div>
The next write should happen at byte <var class="Ar" title="Ar">offset</var>.
<h2 class="Ss" title="Ss"><code class="Dv" title="Dv">ZIP_SOURCE_CLOSE</code></h2>
Reading is done.
<h2 class="Ss" title="Ss"><code class="Dv" title="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.
<h2 class="Ss" title="Ss"><code class="Dv" title="Dv">ZIP_SOURCE_ERROR</code></h2>
Get error information. <var class="Ar" title="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" title="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" title="Xr" href="zip_error_to_data.html">zip_error_to_data(3)</a>
and return its return value. Otherwise, return 2 * sizeof(int).
<h2 class="Ss" title="Ss"><code class="Dv" title="Dv">ZIP_SOURCE_FREE</code></h2>
Clean up and free all resources, including
<var class="Ar" title="Ar">userdata</var>. The callback function will not be
called again.
<h2 class="Ss" title="Ss"><code class="Dv" title="Dv">ZIP_SOURCE_OPEN</code></h2>
Prepare for reading.
<h2 class="Ss" title="Ss"><code class="Dv" title="Dv">ZIP_SOURCE_READ</code></h2>
Read data into the buffer <var class="Ar" title="Ar">data</var> of size
<var class="Ar" title="Ar">len</var>. Return the number of bytes placed into
<var class="Ar" title="Ar">data</var> on success, and zero for end-of-file.
<h2 class="Ss" title="Ss"><code class="Dv" title="Dv">ZIP_SOURCE_REMOVE</code></h2>
Remove the underlying file. This is called if a zip archive is empty when
closed.
<h2 class="Ss" title="Ss"><code class="Dv" title="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.
<h2 class="Ss" title="Ss"><code class="Dv" title="Dv">ZIP_SOURCE_SEEK</code></h2>
Specify position to read next byte from, like
<a class="Xr" title="Xr" href="fseek.html">fseek(3)</a>. Use
<a class="Xr" title="Xr" href="ZIP_SOURCE_GET_ARGS.html">ZIP_SOURCE_GET_ARGS(3)</a>
to decode the arguments into the following struct:
<div class="Pp"></div>
<div class="Bd">
<pre class="Li">
struct zip_source_args_seek {
zip_int64_t offset;
int whence;
};
</pre>
</div>
<div class="Pp"></div>
If the size of the source's data is known, use
<a class="Xr" title="Xr" href="zip_source_seek_compute_offset.html">zip_source_seek_compute_offset(3)</a>
to validate the arguments and compute the new offset.
<h2 class="Ss" title="Ss"><code class="Dv" title="Dv">ZIP_SOURCE_SEEK_WRITE</code></h2>
Specify position to write next byte to, like
<a class="Xr" title="Xr" href="fseek.html">fseek(3)</a>. See
<code class="Dv" title="Dv">ZIP_SOURCE_SEEK</code> for details.
<h2 class="Ss" title="Ss"><code class="Dv" title="Dv">ZIP_SOURCE_STAT</code></h2>
Get meta information for the input data. <var class="Ar" title="Ar">data</var>
points to an allocated <var class="Vt" title="Vt">struct zip_stat</var>, which
should be initialized using
<a class="Xr" title="Xr" href="zip_stat_init.html">zip_stat_init(3)</a> and
then filled in.
<div class="Pp"></div>
For uncompressed, unencrypted data, all information is optional. However, fill
in as much information as is readily available.
<div class="Pp"></div>
If the data is compressed,
<code class="Dv" title="Dv">ZIP_STAT_COMP_METHOD</code>,
<code class="Dv" title="Dv">ZIP_STAT_SIZE</code>, and
<code class="Dv" title="Dv">ZIP_STAT_CRC</code> must be filled in.
<div class="Pp"></div>
If the data is encrypted,
<code class="Dv" title="Dv">ZIP_STAT_ENCRYPTION_METHOD</code>,
<code class="Dv" title="Dv">ZIP_STAT_COMP_METHOD</code>,
<code class="Dv" title="Dv">ZIP_STAT_SIZE</code>, and
<code class="Dv" title="Dv">ZIP_STAT_CRC</code> must be filled in.
<div class="Pp"></div>
Information only available after the source has been read (e.g., size) can be
omitted in an earlier call. <i class="Em" title="Em">NOTE</i>:
<code class="Fn" title="Fn">zip_source_function</code>() may be called with
this argument even after being called with
<code class="Dv" title="Dv">ZIP_SOURCE_CLOSE</code>.
<div class="Pp"></div>
Return sizeof(struct zip_stat) on success.
<h2 class="Ss" title="Ss"><code class="Dv" title="Dv">ZIP_SOURCE_SUPPORTS</code></h2>
Return bitmap specifying which commands are supported. Use
<a class="Xr" title="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.
<h2 class="Ss" title="Ss"><code class="Dv" title="Dv">ZIP_SOURCE_TELL</code></h2>
Return the current read offset in the source, like
<a class="Xr" title="Xr" href="ftell.html">ftell(3)</a>.
<h2 class="Ss" title="Ss"><code class="Dv" title="Dv">ZIP_SOURCE_TELL_WRITE</code></h2>
Return the current write offset in the source, like
<a class="Xr" title="Xr" href="ftell.html">ftell(3)</a>.
<h2 class="Ss" title="Ss"><code class="Dv" title="Dv">ZIP_SOURCE_WRITE</code></h2>
Write data to the source. Return number of bytes written.
<h2 class="Ss" title="Ss" id="Return_Values"><a class="permalink" href="#Return_Values">Return
Values</a></h2>
Commands should return -1 on error.
<code class="Dv" title="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.
<h2 class="Ss" title="Ss" id="Calling_Conventions"><a class="permalink" href="#Calling_Conventions">Calling
Conventions</a></h2>
The library will always issue <code class="Dv" title="Dv">ZIP_SOURCE_OPEN</code>
before issuing <code class="Dv" title="Dv">ZIP_SOURCE_READ</code>,
<code class="Dv" title="Dv">ZIP_SOURCE_SEEK</code>, or
<code class="Dv" title="Dv">ZIP_SOURCE_TELL</code>. When it no longer wishes
to read from this source, it will issue
<code class="Dv" title="Dv">ZIP_SOURCE_CLOSE</code>. If the library wishes to
read the data again, it will issue
<code class="Dv" title="Dv">ZIP_SOURCE_OPEN</code> a second time. If the
function is unable to provide the data again, it should return -1.
<div class="Pp"></div>
<code class="Dv" title="Dv">ZIP_SOURCE_BEGIN_WRITE</code> or
<code class="Dv" title="Dv">ZIP_SOURCE_BEGIN_WRITE_CLONING</code> will be
called before <code class="Dv" title="Dv">ZIP_SOURCE_WRITE</code>,
<code class="Dv" title="Dv">ZIP_SOURCE_SEEK_WRITE</code>, or
<code class="Dv" title="Dv">ZIP_SOURCE_TELL_WRITE</code>. When writing is
complete, either <code class="Dv" title="Dv">ZIP_SOURCE_COMMIT_WRITE</code> or
<code class="Dv" title="Dv">ZIP_SOURCE_ROLLBACK_WRITE</code> will be called.
<div class="Pp"></div>
<code class="Dv" title="Dv">ZIP_SOURCE_STAT</code> can be issued at any time.
<div class="Pp"></div>
<code class="Dv" title="Dv">ZIP_SOURCE_ERROR</code> will only be issued in
response to the function returning -1.
<div class="Pp"></div>
<code class="Dv" title="Dv">ZIP_SOURCE_FREE</code> will be the last command
issued; if <code class="Dv" title="Dv">ZIP_SOURCE_OPEN</code> was called and
succeeded, <code class="Dv" title="Dv">ZIP_SOURCE_CLOSE</code> will be called
before <code class="Dv" title="Dv">ZIP_SOURCE_FREE</code>, and similarly for
<code class="Dv" title="Dv">ZIP_SOURCE_BEGIN_WRITE</code> or
<code class="Dv" title="Dv">ZIP_SOURCE_BEGIN_WRITE_CLONING</code> and
<code class="Dv" title="Dv">ZIP_SOURCE_COMMIT_WRITE</code> or
<code class="Dv" title="Dv">ZIP_SOURCE_ROLLBACK_WRITE</code>.
<h1 class="Sh" title="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" title="Dv">NULL</code> is returned and the error code in
<var class="Ar" title="Ar">archive</var> or
<var class="Ar" title="Ar">error</var> is set to indicate the error (unless it
is <code class="Dv" title="Dv">NULL</code>).
<h1 class="Sh" title="Sh" id="ERRORS"><a class="permalink" href="#ERRORS">ERRORS</a></h1>
<code class="Fn" title="Fn">zip_source_function</code>() fails if:
<dl class="Bl-tag">
<dt>&#x00A0;</dt>
<dd>&#x00A0;</dd>
<dt>[<a class="permalink" href="#ZIP_ER_MEMORY"><code class="Er" title="Er" id="ZIP_ER_MEMORY">ZIP_ER_MEMORY</code></a>]</dt>
<dd>Required memory could not be allocated.</dd>
</dl>
<h1 class="Sh" title="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE
ALSO</a></h1>
<a class="Xr" title="Xr" href="libzip.html">libzip(3)</a>,
<a class="Xr" title="Xr" href="zip_file_add.html">zip_file_add(3)</a>,
<a class="Xr" title="Xr" href="zip_file_replace.html">zip_file_replace(3)</a>,
<a class="Xr" title="Xr" href="zip_source.html">zip_source(3)</a>,
<a class="Xr" title="Xr" href="zip_stat_init.html">zip_stat_init(3)</a>
<h1 class="Sh" title="Sh" id="HISTORY"><a class="permalink" href="#HISTORY">HISTORY</a></h1>
<code class="Fn" title="Fn">zip_source_function</code>() and
<code class="Fn" title="Fn">zip_source_function_create</code>() were added in
libzip 1.0.
<h1 class="Sh" title="Sh" id="AUTHORS"><a class="permalink" href="#AUTHORS">AUTHORS</a></h1>
<span class="An" title="An">Dieter Baron</span>
&lt;<a class="Mt" title="Mt" href="mailto:dillo@nih.at">dillo@nih.at</a>&gt;
and <span class="An" title="An">Thomas Klausner</span>
&lt;<a class="Mt" title="Mt" href="mailto:tk@giga.or.at">tk@giga.or.at</a>&gt;</div>
<table class="foot">
<tr>
<td class="foot-date">December 18, 2017</td>
<td class="foot-os">NetBSD 8.99.27</td>
</tr>
</table>
</body>
</html>
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