NAME
zip_source_function,
zip_source_function_create —
create
data source from function
LIBRARY
libzip (-lzip)
SYNOPSIS
#include <zip.h>
zip_source_t *
zip_source_function(
zip_t
*archive,
zip_source_callback fn,
void *userdata);
zip_source_t *
zip_source_function_create(
zip_source_callback
fn,
void *userdata,
zip_error_t *error);
DESCRIPTION
The functions
zip_source_function() and
zip_source_function_create() creates a zip source from the
user-provided function
fn, which must be of the
following type:
typedef zip_int64_t
(*zip_source_callback)(
void *userdata,
void *data,
zip_uint64_t len,
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
userdata argument supplied to the function. The next two
arguments are a buffer
data of size
len 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.
Depending on the uses, there are three useful sets of commands to be supported
by a
zip_source_callback():
-
-
- read source
- Providing streamed data (for file data added to archives).
Must support
ZIP_SOURCE_OPEN
,
ZIP_SOURCE_READ
,
ZIP_SOURCE_CLOSE
,
ZIP_SOURCE_STAT
, and
ZIP_SOURCE_ERROR
.
-
-
- seekable read source
- Same as previous, but from a source allowing reading from
arbitrary offsets (also for read-only zip archive). Must additionally
support
ZIP_SOURCE_SEEK
,
ZIP_SOURCE_TELL
, and
ZIP_SOURCE_SUPPORTS
.
-
-
- read/write source
- Same as previous, but additionally allowing writing (also
for writable zip archives). Must additionally support
ZIP_SOURCE_BEGIN_WRITE
,
ZIP_SOURCE_COMMIT_WRITE
,
ZIP_SOURCE_ROLLBACK_WRITE
,
ZIP_SOURCE_SEEK_WRITE
,
ZIP_SOURCE_TELL_WRITE
, and
ZIP_SOURCE_REMOVE
.
ZIP_SOURCE_BEGIN_WRITE
Prepare the source for writing. Use this to create any temporary file(s).
ZIP_SOURCE_BEGIN_WRITE_CLONING
Prepare the source for writing, keeping the first
len
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
ZIP_SOURCE_ROLLBACK_WRITE
).
The next write should happen at byte
offset.
ZIP_SOURCE_CLOSE
Reading is done.
ZIP_SOURCE_COMMIT_WRITE
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.
ZIP_SOURCE_ERROR
Get error information.
data 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
zip_errors(3) for details on the
error codes. If the source stores error information in a zip_error_t, use
zip_error_to_data(3) and
return its return value. Otherwise, return 2 * sizeof(int).
ZIP_SOURCE_FREE
Clean up and free all resources, including
userdata. The
callback function will not be called again.
ZIP_SOURCE_OPEN
Prepare for reading.
ZIP_SOURCE_READ
Read data into the buffer
data of size
len. Return the number of bytes placed into
data on success, and zero for end-of-file.
ZIP_SOURCE_REMOVE
Remove the underlying file. This is called if a zip archive is empty when
closed.
ZIP_SOURCE_ROLLBACK_WRITE
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.
ZIP_SOURCE_SEEK
Specify position to read next byte from, like
fseek(3). Use
ZIP_SOURCE_GET_ARGS(3) to
decode the arguments into the following struct:
struct zip_source_args_seek {
zip_int64_t offset;
int whence;
};
If the size of the source's data is known, use
zip_source_seek_compute_offset(3)
to validate the arguments and compute the new offset.
ZIP_SOURCE_SEEK_WRITE
Specify position to write next byte to, like
fseek(3). See
ZIP_SOURCE_SEEK
for details.
ZIP_SOURCE_STAT
Get meta information for the input data.
data points to an
allocated
struct zip_stat, which should be initialized
using
zip_stat_init(3) and then
filled in.
For uncompressed, unencrypted data, all information is optional. However, fill
in as much information as is readily available.
If the data is compressed,
ZIP_STAT_COMP_METHOD
,
ZIP_STAT_SIZE
, and
ZIP_STAT_CRC
must be filled in.
If the data is encrypted,
ZIP_STAT_ENCRYPTION_METHOD
,
ZIP_STAT_COMP_METHOD
,
ZIP_STAT_SIZE
, and
ZIP_STAT_CRC
must be filled in.
Information only available after the source has been read (e.g., size) can be
omitted in an earlier call.
NOTE:
zip_source_function() may be called with this argument even
after being called with
ZIP_SOURCE_CLOSE
.
Return sizeof(struct zip_stat) on success.
ZIP_SOURCE_SUPPORTS
Return bitmap specifying which commands are supported. Use
zip_source_make_command_bitmap(3).
If this command is not implemented, the source is assumed to be a read source
without seek support.
ZIP_SOURCE_TELL
Return the current read offset in the source, like
ftell(3).
ZIP_SOURCE_TELL_WRITE
Return the current write offset in the source, like
ftell(3).
ZIP_SOURCE_WRITE
Write data to the source. Return number of bytes written.
Return Values
Commands should return -1 on error.
ZIP_SOURCE_ERROR
will be called to retrieve the error code. On success, commands return 0,
unless specified otherwise in the description above.
Calling Conventions
The library will always issue
ZIP_SOURCE_OPEN
before
issuing
ZIP_SOURCE_READ
,
ZIP_SOURCE_SEEK
, or
ZIP_SOURCE_TELL
. When it no longer wishes to read from
this source, it will issue
ZIP_SOURCE_CLOSE
. If the
library wishes to read the data again, it will issue
ZIP_SOURCE_OPEN
a second time. If the function is
unable to provide the data again, it should return -1.
ZIP_SOURCE_BEGIN_WRITE
or
ZIP_SOURCE_BEGIN_WRITE_CLONING
will be called before
ZIP_SOURCE_WRITE
,
ZIP_SOURCE_SEEK_WRITE
, or
ZIP_SOURCE_TELL_WRITE
. When writing is complete,
either
ZIP_SOURCE_COMMIT_WRITE
or
ZIP_SOURCE_ROLLBACK_WRITE
will be called.
ZIP_SOURCE_STAT
can be issued at any time.
ZIP_SOURCE_ERROR
will only be issued in response to the
function returning -1.
ZIP_SOURCE_FREE
will be the last command issued; if
ZIP_SOURCE_OPEN
was called and succeeded,
ZIP_SOURCE_CLOSE
will be called before
ZIP_SOURCE_FREE
, and similarly for
ZIP_SOURCE_BEGIN_WRITE
or
ZIP_SOURCE_BEGIN_WRITE_CLONING
and
ZIP_SOURCE_COMMIT_WRITE
or
ZIP_SOURCE_ROLLBACK_WRITE
.
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_function() fails if:
-
-
- [
ZIP_ER_MEMORY
]
- Required memory could not be allocated.
SEE ALSO
libzip(3),
zip_add(3),
zip_replace(3),
zip_source(3),
zip_stat_init(3)
HISTORY
zip_source_function() and
zip_source_function_create() were added in libzip 1.0.
AUTHORS
Dieter Baron
<
dillo@nih.at> and
Thomas Klausner
<
tk@giga.or.at>