ARCHIVE_READ_OPEN(3) BSD Library Functions Manual ARCHIVE_READ_OPEN(3)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 *, void *buff, size_t size);
DESCRIPTIONarchive_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 descrip‐
tor 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 file‐
name 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 ssize_t archive_read_callback(struct archive *,
void *client_data, const void **buffer)
typedef off_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 process‐
ing 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 ALSOtar(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)BSD February 2, 2012 BSD
