NAME
archive_read_open,
archive_read_open2,
archive_read_open_fd,
archive_read_open_FILE,
archive_read_open_filename,
archive_read_open_memory —
functions
for reading streaming archives
LIBRARY
Streaming Archive Library (libarchive, -larchive)
SYNOPSIS
#include <archive.h>
int
archive_read_open(
struct archive *,
void *client_data,
archive_open_callback
*,
archive_read_callback *,
archive_close_callback *);
int
archive_read_open2(
struct archive *,
void *client_data,
archive_open_callback
*,
archive_read_callback *,
archive_skip_callback *,
archive_close_callback *);
int
archive_read_open_FILE(
struct
archive *,
FILE
*file);
int
archive_read_open_fd(
struct
archive *,
int fd,
size_t block_size);
int
archive_read_open_filename(
struct archive
*,
const char *filename,
size_t
block_size);
int
archive_read_open_memory(
struct
archive *,
const void
*buff,
size_t size);
DESCRIPTION
- archive_read_open()
- The same as archive_read_open2(), except
that the skip callback is assumed to be
NULL
.
- archive_read_open2()
- Freeze the settings, open the archive, and prepare for
reading entries. This is the most generic version of this call, which
accepts four callback functions. Most clients will want to use
archive_read_open_filename(),
archive_read_open_FILE(),
archive_read_open_fd(), or
archive_read_open_memory() instead. The library invokes
the client-provided functions to obtain raw bytes from the archive.
- archive_read_open_FILE()
- Like archive_read_open(), except that it
accepts a FILE * pointer. This function should not
be used with tape drives or other devices that require strict I/O
blocking.
- archive_read_open_fd()
- Like archive_read_open(), except that it
accepts a file descriptor and block size rather than a set of function
pointers. Note that the file descriptor will not be automatically closed
at end-of-archive. This function is safe for use with tape drives or other
blocked devices.
- archive_read_open_file()
- This is a deprecated synonym for
archive_read_open_filename().
- archive_read_open_filename()
- Like archive_read_open(), except that it
accepts a simple filename and a block size. A NULL filename represents
standard input. This function is safe for use with tape drives or other
blocked devices.
- archive_read_open_memory()
- Like archive_read_open(), except that it
accepts a pointer and size of a block of memory containing the archive
data.
A complete description of the struct archive and struct archive_entry objects
can be found in the overview manual page for
libarchive(3).
CLIENT CALLBACKS
The callback functions must match the following prototypes:
- typedef la_ssize_t
archive_read_callback(struct archive
*, void *client_data, const
void **buffer);
- typedef la_int64_t
archive_skip_callback(struct archive
*, void *client_data, off_t
request);
- typedef int
archive_open_callback(struct archive
*, void *client_data)
- typedef int
archive_close_callback(struct archive
*, void *client_data)
The open callback is invoked by
archive_open(). It should
return
ARCHIVE_OK if the underlying file or data source is
successfully opened. If the open fails, it should call
archive_set_error() to register an error code and message
and return
ARCHIVE_FATAL.
The read callback is invoked whenever the library requires raw bytes from the
archive. The read callback should read data into a buffer, set the
const void **buffer
argument to point to the available
data, and return a count of the number of bytes available. The library will
invoke the read callback again only after it has consumed this data. The
library imposes no constraints on the size of the data blocks returned. On
end-of-file, the read callback should return zero. On error, the read callback
should invoke
archive_set_error() to register an error code
and message and return -1.
The skip callback is invoked when the library wants to ignore a block of data.
The return value is the number of bytes actually skipped, which may differ
from the request. If the callback cannot skip data, it should return zero. If
the skip callback is not provided (the function pointer is
NULL ),
the library will invoke the read function
instead and simply discard the result. A skip callback can provide significant
performance gains when reading uncompressed archives from slow disk drives or
other media that can skip quickly.
The close callback is invoked by archive_close when the archive processing is
complete. The callback should return
ARCHIVE_OK on success.
On failure, the callback should invoke
archive_set_error()
to register an error code and message and return
ARCHIVE_FATAL.
RETURN VALUES
These functions return
ARCHIVE_OK on success, or
ARCHIVE_FATAL.
ERRORS
Detailed error codes and textual descriptions are available from the
archive_errno() and
archive_error_string()
functions.
SEE ALSO
tar(1),
libarchive(3),
archive_read(3),
archive_read_data(3),
archive_read_filter(3),
archive_read_format(3),
archive_read_set_options(3),
archive_util(3),
tar(5)