Manual Pages  — ARCHIVE_READ_OPEN

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 SYNOPSIS DESCRIPTION CLIENT CALLBACKS RETURN VALUES ERRORS SEE ALSO

Streaming Archive Library (libarchive, -larchive)

#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);

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.

These functions return ARCHIVE_OK on success, or ARCHIVE_FATAL.

Detailed error codes and textual descriptions are available from the archive_errno() and archive_error_string() functions.