.\" zip_source_file.mdoc -- create data source from a file
.\" Copyright (C) 2004-2021 Dieter Baron and Thomas Klausner
.\"
.\" This file is part of libzip, a library to manipulate ZIP archives.
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.Dd June 30, 2023
.Dt ZIP_SOURCE_FILE 3
.Os
.Sh NAME
.Nm zip_source_file ,
.Nm zip_source_file_create
.Nd create data source from a file
.Sh LIBRARY
libzip (-lzip)
.Sh SYNOPSIS
.In zip.h
.Ft zip_source_t *
.Fn zip_source_file "zip_t *archive" "const char *fname" "zip_uint64_t start" "zip_int64_t len"
.Ft zip_source_t *
.Fn zip_source_file_create "const char *fname" "zip_uint64_t start" "zip_int64_t len" "zip_error_t *error"
.Sh DESCRIPTION
The functions
.Fn zip_source_file
and
.Fn zip_source_file_create
create a zip source from a file.
They open
.Ar fname
and read
.Ar len
bytes from offset
.Ar start
from it.
.Pp
When passing
.Dv ZIP_LENGTH_TO_END
(or \-1, which is deprecated) as
.Ar len ,
.Nm
determines the file size when it is called and uses that as the
expected file size.
If the file size grows between creating and reading from the source,
the additional data is ignored.
If the file shrinks,
.Nm libzip
treats it as an error
.Dv ( ZIP_ER_DATA_LENGTH ) .
.Pp
When passing
.Dv ZIP_LENGTH_UNCHECKED
as
.Ar len ,
.Nm
assumes the file's size is unknown.
Reading from the source returns as much data as is there at that time
(usually when calling
.Xr zip_close 3 ) .
.Pp
.Nm libzip
can do various optimizations if the size of a source is known when
it's created, so
.Dv ZIP_LENGTH_TO_END
is preferrable.
If you deal with files that are likely to change while you are
processing them, you can use the less efficient
.Dv ZIP_LENGTH_UNCHECKED .
.Pp
If the file supports seek, the source can be used to open a zip archive from.
.Pp
The file is opened and read when the data from the source is used, usually by
.Fn zip_close
or
.Fn zip_open_from_source .
.Sh RETURN VALUES
Upon successful completion, the created source is returned.
Otherwise,
.Dv NULL
is returned and the error code in
.Ar archive
or
.Ar error
is set to indicate the error.
.Sh ERRORS
.Fn zip_source_file
and
.Fn zip_source_file_create
fail if:
.Bl -tag -width Er
.It Bq Er ZIP_ER_INVAL
.Ar fname ,
.Ar start ,
or
.Ar len
are invalid.
.It Bq Er ZIP_ER_MEMORY
Required memory could not be allocated.
.It Bq Er ZIP_ER_OPEN
Opening
.Ar fname
failed.
.El
.Sh SEE ALSO
.Xr libzip 3 ,
.Xr zip_file_add 3 ,
.Xr zip_file_replace 3 ,
.Xr zip_source 3
.Sh HISTORY
.Fn zip_source_file
and
.Fn zip_source_file_create
were added in libzip 1.0.
.Pp
.Dv ZIP_LENGTH_TO_END
and
.Dv ZIP_LENGTH_UNCHECKED
were added in libzip 1.10.1.
.Sh AUTHORS
.An -nosplit
.An Dieter Baron Aq Mt dillo@nih.at
and
.An Thomas Klausner Aq Mt tk@giga.or.at