174 lines
6.0 KiB
Groff
174 lines
6.0 KiB
Groff
.\" Automatically generated from an mdoc input file. Do not edit.
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.\" zip_source_layered.mdoc -- create layered source from function
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.\" Copyright (C) 2004-2022 Dieter Baron and Thomas Klausner
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.\"
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.\" This file is part of libzip, a library to manipulate ZIP archives.
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.\" The authors can be contacted at <info@libzip.org>
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in
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.\" the documentation and/or other materials provided with the
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.\" distribution.
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.\" 3. The names of the authors may not be used to endorse or promote
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.\" products derived from this software without specific prior
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.\" written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS
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.\" OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
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.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
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.\" GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
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.\" IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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.\" OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
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.\" IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.TH "ZIP_SOURCE_LAYERED" "3" "January 20, 2023" "NiH" "Library Functions Manual"
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.nh
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.if n .ad l
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.SH "NAME"
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\fBzip_source_layered\fR,
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\fBzip_source_layered_create\fR
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\- create layered data source from function
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.SH "LIBRARY"
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libzip (-lzip)
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.SH "SYNOPSIS"
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\fB#include <zip.h>\fR
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.sp
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\fIzip_source_t *\fR
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.br
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.PD 0
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.HP 4n
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\fBzip_source_layered\fR(\fIzip_t\ *archive\fR, \fIzip_source_t\ *source\fR, \fIzip_source_layered_callback\ fn\fR, \fIvoid\ *userdata\fR);
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.PD
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.PP
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\fIzip_source_t *\fR
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.br
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.PD 0
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.HP 4n
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\fBzip_source_layered_create\fR(\fIzip_source_t\ *source\fR, \fIzip_source_layered_callback\ fn\fR, \fIvoid\ *userdata\fR, \fIzip_error_t\ *error\fR);
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.PD
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.SH "DESCRIPTION"
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The functions
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\fBzip_source_layered\fR()
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and
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\fBzip_source_layered_create\fR()
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create a layered zip source from the user-provided function
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\fIfn\fR,
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which must be of the following type:
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.PP
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\fItypedef zip_int64_t\fR
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\fB\fR(*\zip_source_layered_callback\fR)\fP\fR(\fIzip_source_t\ *source\fR, \fIvoid\ *userdata\fR, \fIvoid\ *data\fR, \fIzip_uint64_t\ length\fR, \fIzip_source_cmd_t\ cmd\fR)
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.PP
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\fIarchive\fR
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or
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\fIerror\fR
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are used for reporting errors and can be
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\fRNULL\fR.
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.PP
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When called by the library, the first argument is the
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\fIsource\fR
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of the lower layer, the second argument is the
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\fIuserdata\fR
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argument supplied to the function.
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The next two arguments are a buffer
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\fIdata\fR
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of size
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\fIlength\fR
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when data is passed in or expected to be returned, or else
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\fRNULL\fR
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and 0.
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The last argument,
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\fIcmd\fR,
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specifies which action the function should perform.
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.PP
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See
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zip_source_function(3)
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for a description of the commands.
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.PP
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A layered source transforms the data or metadata of the source below in some way.
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Layered sources can't support writing and are not sufficient to cleanly add support for additional compression or encryption methods.
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This may be revised in a later release of libzip.
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.PP
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On success, the layered source takes ownership of
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\fIsource\fR.
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The caller should not free it.
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.PP
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The interaction with the lower layer depends on the command:
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.SS "\fRZIP_SOURCE_ACCEPT_EMPTY\fR"
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If the layered source supports this command, the lower layer is not called automatically.
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Otherwise, the return value of the lower source is used.
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.SS "\fRZIP_SOURCE_CLOSE\fR"
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The lower layer is closed after the callback returns.
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.SS "\fRZIP_SOURCE_ERROR\fR"
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The lower layer is not called automatically.
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If you need to retrieve error information from the lower layer, use
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zip_error_set_from_source(3)
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or
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zip_source_pass_to_lower_layer(3).
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.SS "\fRZIP_SOURCE_FREE\fR"
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The lower layer is freed after the callback returns.
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.SS "\fRZIP_SOURCE_GET_FILE_ATTRIBUTES\fR"
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The attributes of the lower layer are merged with the attributes returned by the callback: information set by the callback wins over the lower layer, with the following exceptions: the higher
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\fIversion_needed\fR
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is used, and
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\fIgeneral_purpose_bit_flags\fR
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are only overwritten if the corresponding bit is set in
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\fIgeneral_purpose_bit_mask\fR.
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.SS "\fRZIP_SOURCE_OPEN\fR"
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The lower layer is opened before the callback is called.
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.SS "\fRZIP_SOURCE_READ\fR"
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The lower layer is not called automatically.
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.SS "\fRZIP_SOURCE_SEEK\fR"
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The lower layer is not called automatically.
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.SS "\fRZIP_SOURCE_STAT\fR"
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\fIdata\fR
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contains the stat information from the lower layer when the callback is called.
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.SS "\fRZIP_SOURCE_SUPPORTS\fR"
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\fIdata\fR
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contains the bitmap of commands supported by the lower layer when the callback is called.
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Since layered sources can't support writing, all commands related to writing are stripped from the returned support bitmap.
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.SS "\fRZIP_SOURCE_TELL\fR"
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The lower layer is not called automatically.
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.SH "RETURN VALUES"
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Upon successful completion, the created source is returned.
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Otherwise,
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\fRNULL\fR
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is returned and the error code in
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\fIarchive\fR
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or
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\fIerror\fR
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is set to indicate the error (unless
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it is
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\fRNULL\fR).
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.SH "ERRORS"
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\fBzip_source_layered\fR()
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fails if:
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.TP 19n
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[\fRZIP_ER_MEMORY\fR]
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Required memory could not be allocated.
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.SH "SEE ALSO"
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libzip(3),
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zip_file_add(3),
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zip_file_attributes_init(3),
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zip_file_replace(3),
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zip_source(3),
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zip_source_function(3),
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zip_source_pass_to_lower_layer(3)
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.SH "HISTORY"
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\fBzip_source_layered\fR()
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and
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\fBzip_source_layered_create\fR()
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were added in libzip 1.10.
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.SH "AUTHORS"
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Dieter Baron <\fIdillo@nih.at\fR>
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and
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Thomas Klausner <\fIwiz@gatalith.at\fR>
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