ZIP_SOURCE_LAYERED(3)

NAME
zip_source_layered, zip_source_layered_create - create layered data source from function

LIBRARY
libzip (-lzip)

SYNOPSIS
#include <zip.h>

zip_source_t *
zip_source_layered(zip_t *archive, zip_source_t *source, zip_source_layered_callback fn, void *userdata);

zip_source_t *
zip_source_layered_create(zip_source_t *source, zip_source_layered_callback fn, void *userdata, zip_error_t *error);

DESCRIPTION
The functions zip_source_layered() and zip_source_layered_create() create a layered zip source from the user-provided function fn, which must be of the following type:

typedef zip_int64_t (*ip_source_layered_callback)(zip_source_t *source, void *userdata, void *data, zip_uint64_t length, zip_source_cmd_t cmd)

archive or error are used for reporting errors and can be NULL.

When called by the library, the first argument is the source of the lower layer, the second argument is the userdata argument supplied to the function. The next two arguments are a buffer data of size length when data is passed in or expected to be returned, or else NULL and 0. The last argument, cmd, specifies which action the function should perform.

See zip_source_function(3) for a description of the commands.

A layered source transforms the data or metadata of the source below in some way. Layered sources can't support writing and are not sufficient to cleanly add support for additional compression or encryption methods. This may be revised in a later release of libzip.

On success, the layered source takes ownership of source. The caller should not free it.

The interaction with the lower layer depends on the command:

  ZIP_SOURCE_ACCEPT_EMPTY
If the layered source supports this command, the lower layer is not called automatically. Otherwise, the return value of the lower source is used.

  ZIP_SOURCE_CLOSE
The lower layer is closed after the callback returns.

  ZIP_SOURCE_ERROR
The lower layer is not called automatically. If you need to retrieve error information from the lower layer, use zip_error_set_from_source(3) or zip_source_pass_to_lower_layer(3).

  ZIP_SOURCE_FREE
The lower layer is freed after the callback returns.

  ZIP_SOURCE_GET_FILE_ATTRIBUTES
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 version_needed is used, and general_purpose_bit_flags are only overwritten if the corresponding bit is set in general_purpose_bit_mask.

  ZIP_SOURCE_OPEN
The lower layer is opened before the callback is called.

  ZIP_SOURCE_READ
The lower layer is not called automatically.

  ZIP_SOURCE_SEEK
The lower layer is not called automatically.

  ZIP_SOURCE_STAT
data contains the stat information from the lower layer when the callback is called.

  ZIP_SOURCE_SUPPORTS
data contains the bitmap of commands supported by the lower layer when the callback is called. Since layered sources can't support writing, all commands related to writing are stripped from the returned support bitmap.

  ZIP_SOURCE_TELL
The lower layer is not called automatically.

RETURN VALUES
Upon successful completion, the created source is returned. Otherwise, NULL is returned and the error code in archive or error is set to indicate the error (unless it is NULL).

ERRORS
zip_source_layered() fails if:

[ZIP_ER_MEMORY]
    Required memory could not be allocated.

SEE ALSO
libzip(3), zip_file_add(3), zip_file_attributes_init(3), zip_file_replace(3), zip_source(3), zip_source_function(3), zip_source_pass_to_lower_layer(3)

HISTORY
zip_source_layered() and zip_source_layered_create() were added in libzip 1.10.

AUTHORS
Dieter Baron <dillo@nih.at> and Thomas Klausner <wiz@gatalith.at>