ARCHIVE_READ(3) | Library Functions Manual | ARCHIVE_READ(3) |
archive_read
—
#include <archive.h>
To read an archive, you must first obtain an initialized struct
archive object from archive_read_new
().
You can then modify this object for the desired operations with
the various archive_read_set_XXX
() and
archive_read_support_XXX
() functions. In particular,
you will need to invoke appropriate
archive_read_support_XXX
() functions to enable the
corresponding compression and format support. Note that these latter
functions perform two distinct operations: they cause the corresponding
support code to be linked into your program, and they enable the
corresponding auto-detect code. Unless you have specific constraints, you
will generally want to invoke
archive_read_support_filter_all
() and
archive_read_support_format_all
() to enable
auto-detect for all formats and compression types currently supported by the
library.
Once you have prepared the struct archive object, you call
archive_read_open
() to actually open the archive and
prepare it for reading. There are several variants of this function; the
most basic expects you to provide pointers to several functions that can
provide blocks of bytes from the archive. There are convenience forms that
allow you to specify a filename, file descriptor, FILE
* object, or a block of memory from which to read the archive data.
Note that the core library makes no assumptions about the size of the blocks
read; callback functions are free to read whatever block size is most
appropriate for the medium.
Each archive entry consists of a header followed by a certain
amount of data. You can obtain the next header with
archive_read_next_header
(), which returns a pointer
to an struct archive_entry structure with information about the current
archive element. If the entry is a regular file, then the header will be
followed by the file data. You can use
archive_read_data
() (which works much like the
read(2) system call) to read
this data from the archive, or
archive_read_data_block
() which provides a slightly
more efficient interface. You may prefer to use the higher-level
archive_read_data_skip
(), which reads and discards
the data for this entry,
archive_read_data_into_fd
(), which copies the data
to the provided file descriptor, or
archive_read_extract
(), which recreates the
specified entry on disk and copies data from the archive. In particular,
note that archive_read_extract
() uses the struct
archive_entry structure that you provide it, which may differ from the entry
just read from the archive. In particular, many applications will want to
override the pathname, file permissions, or ownership.
Once you have finished reading data from the archive, you should
call archive_read_close
() to close the archive, then
call archive_read_free
() to release all resources,
including all memory allocated by the library.
void list_archive(const char *name) { struct mydata *mydata; struct archive *a; struct archive_entry *entry; mydata = malloc(sizeof(struct mydata)); a = archive_read_new(); mydata->name = name; archive_read_support_filter_all(a); archive_read_support_format_all(a); archive_read_open(a, mydata, myopen, myread, myclose); while (archive_read_next_header(a, &entry) == ARCHIVE_OK) { printf("%s\n",archive_entry_pathname(entry)); archive_read_data_skip(a); } archive_read_free(a); free(mydata); } la_ssize_t myread(struct archive *a, void *client_data, const void **buff) { struct mydata *mydata = client_data; *buff = mydata->buff; return (read(mydata->fd, mydata->buff, 10240)); } int myopen(struct archive *a, void *client_data) { struct mydata *mydata = client_data; mydata->fd = open(mydata->name, O_RDONLY); return (mydata->fd >= 0 ? ARCHIVE_OK : ARCHIVE_FATAL); } int myclose(struct archive *a, void *client_data) { struct mydata *mydata = client_data; if (mydata->fd > 0) close(mydata->fd); return (ARCHIVE_OK); }
libarchive
library first appeared in
FreeBSD 5.3.
libarchive
library was written by
Tim Kientzle ⟨kientzle@acm.org⟩.
February 2, 2012 | NetBSD 9.0 |