libarchive/archive_write.3 - third_party/libarchive - Git at Google

 .\" Copyright (c) 2003-2011 Tim Kientzle
 .\" All rights reserved.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
 .\" modification, are permitted provided that the following conditions
 .\" are met:
 .\" 1. Redistributions of source code must retain the above copyright
 .\"    notice, this list of conditions and the following disclaimer.
 .\" 2. Redistributions in binary form must reproduce the above copyright
 .\"    notice, this list of conditions and the following disclaimer in the
 .\"    documentation and/or other materials provided with the distribution.
 .\"
 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
 .\" $FreeBSD$
 .\"
 .Dd February 2, 2012
 .Dt ARCHIVE_WRITE 3
 .Os
 .Sh NAME
 .Nm archive_write
 .Nd functions for creating archives
 .Sh LIBRARY
 Streaming Archive Library (libarchive, -larchive)
 .Sh SYNOPSIS
 .In archive.h
 .Sh DESCRIPTION
 These functions provide a complete API for creating streaming
 archive files.
 The general process is to first create the
 .Tn struct archive
 object, set any desired options, initialize the archive, append entries, then
 close the archive and release all resources.
 .\"
 .Ss Create archive object
 See
 .Xr archive_write_new 3 .
 .Pp
 To write an archive, you must first obtain an initialized
 .Tn struct archive
 object from
 .Fn archive_write_new .
 .\"
 .Ss Enable filters and formats, configure block size and padding
 See
 .Xr archive_write_filter 3 ,
 .Xr archive_write_format 3
 and
 .Xr archive_write_blocksize 3 .
 .Pp
 You can then modify this object for the desired operations with the
 various
 .Fn archive_write_set_XXX
 functions.
 In particular, you will need to invoke appropriate
 .Fn archive_write_add_XXX
 and
 .Fn archive_write_set_XXX
 functions to enable the corresponding compression and format
 support.
 .\"
 .Ss Set options
 See
 .Xr archive_read_set_options 3 .
 .\"
 .Ss Open archive
 See
 .Xr archive_write_open 3 .
 .Pp
 Once you have prepared the
 .Tn struct archive
 object, you call
 .Fn archive_write_open
 to actually open the archive and prepare it for writing.
 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,
 .Ft "FILE *"
 object, or a block of memory from which to write the archive data.
 .\"
 .Ss Produce archive
 See
 .Xr archive_write_header 3
 and
 .Xr archive_write_data 3 .
 .Pp
 Individual archive entries are written in a three-step
 process:
 You first initialize a
 .Tn struct archive_entry
 structure with information about the new entry.
 At a minimum, you should set the pathname of the
 entry and provide a
 .Va struct stat
 with a valid
 .Va st_mode
 field, which specifies the type of object and
 .Va st_size
 field, which specifies the size of the data portion of the object.
 .\"
 .Ss Release resources
 See
 .Xr archive_write_free 3 .
 .Pp
 After all entries have been written, use the
 .Fn archive_write_free
 function to release all resources.
 .\"
 .Sh EXAMPLE
 The following sketch illustrates basic usage of the library.
 In this example,
 the callback functions are simply wrappers around the standard
 .Xr open 2 ,
 .Xr write 2 ,
 and
 .Xr close 2
 system calls.
 .Bd -literal -offset indent
 #ifdef __linux__
 #define	_FILE_OFFSET_BITS 64
 #endif
 #include <sys/stat.h>
 #include <archive.h>
 #include <archive_entry.h>
 #include <fcntl.h>
 #include <stdlib.h>
 #include <unistd.h>

 struct mydata {
   const char *name;
   int fd;
 };

 int
 myopen(struct archive *a, void *client_data)
 {
   struct mydata *mydata = client_data;

   mydata->fd = open(mydata->name, O_WRONLY | O_CREAT, 0644);
   if (mydata->fd >= 0)
     return (ARCHIVE_OK);
   else
     return (ARCHIVE_FATAL);
 }

 la_ssize_t
 mywrite(struct archive *a, void *client_data, const void *buff, size_t n)
 {
   struct mydata *mydata = client_data;

   return (write(mydata->fd, buff, n));
 }

 int
 myclose(struct archive *a, void *client_data)
 {
   struct mydata *mydata = client_data;

   if (mydata->fd > 0)
     close(mydata->fd);
   return (0);
 }

 void
 write_archive(const char *outname, const char **filename)
 {
   struct mydata *mydata = malloc(sizeof(struct mydata));
   struct archive *a;
   struct archive_entry *entry;
   struct stat st;
   char buff[8192];
   int len;
   int fd;

   a = archive_write_new();
   mydata->name = outname;
   /* Set archive format and filter according to output file extension.
    * If it fails, set default format. Platform depended function.
    * See supported formats in archive_write_set_format_filter_by_ext.c */
   if (archive_write_set_format_filter_by_ext(a, outname) != ARCHIVE_OK)  {
     archive_write_add_filter_gzip(a);
     archive_write_set_format_ustar(a);
   }
   archive_write_open(a, mydata, myopen, mywrite, myclose);
   while (*filename) {
     stat(*filename, &st);
     entry = archive_entry_new();
     archive_entry_copy_stat(entry, &st);
     archive_entry_set_pathname(entry, *filename);
     archive_write_header(a, entry);
     if ((fd = open(*filename, O_RDONLY)) != -1) {
       len = read(fd, buff, sizeof(buff));
       while (len > 0) {
         archive_write_data(a, buff, len);
         len = read(fd, buff, sizeof(buff));
       }
       close(fd);
     }
     archive_entry_free(entry);
     filename++;
   }
   archive_write_free(a);
 }

 int main(int argc, const char **argv)
 {
   const char *outname;
   argv++;
   outname = *argv++;
   write_archive(outname, argv);
   return 0;
 }
 .Ed
 .Sh SEE ALSO
 .Xr tar 1 ,
 .Xr libarchive 3 ,
 .Xr archive_write_set_options 3 ,
 .Xr cpio 5 ,
 .Xr mtree 5 ,
 .Xr tar 5
 .Sh HISTORY
 The
 .Nm libarchive
 library first appeared in
 .Fx 5.3 .
 .Sh AUTHORS
 .An -nosplit
 The
 .Nm libarchive
 library was written by
 .An Tim Kientzle Aq kientzle@acm.org .
 .Sh BUGS
 There are many peculiar bugs in historic tar implementations that may cause
 certain programs to reject archives written by this library.
 For example, several historic implementations calculated header checksums
 incorrectly and will thus reject valid archives; GNU tar does not fully support
 pax interchange format; some old tar implementations required specific
 field terminations.
 .Pp
 The default pax interchange format eliminates most of the historic
 tar limitations and provides a generic key/value attribute facility
 for vendor-defined extensions.
 One oversight in POSIX is the failure to provide a standard attribute
 for large device numbers.
 This library uses
 .Dq SCHILY.devminor
 and
 .Dq SCHILY.devmajor
 for device numbers that exceed the range supported by the backwards-compatible
 ustar header.
 These keys are compatible with Joerg Schilling's
 .Nm star
 archiver.
 Other implementations may not recognize these keys and will thus be unable
 to correctly restore device nodes with large device numbers from archives
 created by this library.
	.\" Copyright (c) 2003-2011 Tim Kientzle
	.\" All rights reserved.
	.\"
	.\" Redistribution and use in source and binary forms, with or without
	.\" modification, are permitted provided that the following conditions
	.\" are met:
	.\" 1. Redistributions of source code must retain the above copyright
	.\" notice, this list of conditions and the following disclaimer.
	.\" 2. Redistributions in binary form must reproduce the above copyright
	.\" notice, this list of conditions and the following disclaimer in the
	.\" documentation and/or other materials provided with the distribution.
	.\"
	.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	.\" SUCH DAMAGE.
	.\"
	.\" $FreeBSD$
	.\"
	.Dd February 2, 2012
	.Dt ARCHIVE_WRITE 3
	.Os
	.Sh NAME
	.Nm archive_write
	.Nd functions for creating archives
	.Sh LIBRARY
	Streaming Archive Library (libarchive, -larchive)
	.Sh SYNOPSIS
	.In archive.h
	.Sh DESCRIPTION
	These functions provide a complete API for creating streaming
	archive files.
	The general process is to first create the
	.Tn struct archive
	object, set any desired options, initialize the archive, append entries, then
	close the archive and release all resources.
	.\"
	.Ss Create archive object
	See
	.Xr archive_write_new 3 .
	.Pp
	To write an archive, you must first obtain an initialized
	.Tn struct archive
	object from
	.Fn archive_write_new .
	.\"
	.Ss Enable filters and formats, configure block size and padding
	See
	.Xr archive_write_filter 3 ,
	.Xr archive_write_format 3
	and
	.Xr archive_write_blocksize 3 .
	.Pp
	You can then modify this object for the desired operations with the
	various
	.Fn archive_write_set_XXX
	functions.
	In particular, you will need to invoke appropriate
	.Fn archive_write_add_XXX
	and
	.Fn archive_write_set_XXX
	functions to enable the corresponding compression and format
	support.
	.\"
	.Ss Set options
	See
	.Xr archive_read_set_options 3 .
	.\"
	.Ss Open archive
	See
	.Xr archive_write_open 3 .
	.Pp
	Once you have prepared the
	.Tn struct archive
	object, you call
	.Fn archive_write_open
	to actually open the archive and prepare it for writing.
	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,
	.Ft "FILE *"
	object, or a block of memory from which to write the archive data.
	.\"
	.Ss Produce archive
	See
	.Xr archive_write_header 3
	and
	.Xr archive_write_data 3 .
	.Pp
	Individual archive entries are written in a three-step
	process:
	You first initialize a
	.Tn struct archive_entry
	structure with information about the new entry.
	At a minimum, you should set the pathname of the
	entry and provide a
	.Va struct stat
	with a valid
	.Va st_mode
	field, which specifies the type of object and
	.Va st_size
	field, which specifies the size of the data portion of the object.
	.\"
	.Ss Release resources
	See
	.Xr archive_write_free 3 .
	.Pp
	After all entries have been written, use the
	.Fn archive_write_free
	function to release all resources.
	.\"
	.Sh EXAMPLE
	The following sketch illustrates basic usage of the library.
	In this example,
	the callback functions are simply wrappers around the standard
	.Xr open 2 ,
	.Xr write 2 ,
	and
	.Xr close 2
	system calls.
	.Bd -literal -offset indent
	#ifdef __linux__
	#define _FILE_OFFSET_BITS 64
	#endif
	#include <sys/stat.h>
	#include <archive.h>
	#include <archive_entry.h>
	#include <fcntl.h>
	#include <stdlib.h>
	#include <unistd.h>

	struct mydata {
	const char *name;
	int fd;
	};

	int
	myopen(struct archive a, void client_data)
	{
	struct mydata *mydata = client_data;

	mydata->fd = open(mydata->name, O_WRONLY \| O_CREAT, 0644);
	if (mydata->fd >= 0)
	return (ARCHIVE_OK);
	else
	return (ARCHIVE_FATAL);
	}

	la_ssize_t
	mywrite(struct archive a, void client_data, const void *buff, size_t n)
	{
	struct mydata *mydata = client_data;

	return (write(mydata->fd, buff, n));
	}

	int
	myclose(struct archive a, void client_data)
	{
	struct mydata *mydata = client_data;

	if (mydata->fd > 0)
	close(mydata->fd);
	return (0);
	}

	void
	write_archive(const char outname, const char *filename)
	{
	struct mydata *mydata = malloc(sizeof(struct mydata));
	struct archive *a;
	struct archive_entry *entry;
	struct stat st;
	char buff[8192];
	int len;
	int fd;

	a = archive_write_new();
	mydata->name = outname;
	/* Set archive format and filter according to output file extension.
	* If it fails, set default format. Platform depended function.
	* See supported formats in archive_write_set_format_filter_by_ext.c */
	if (archive_write_set_format_filter_by_ext(a, outname) != ARCHIVE_OK) {
	archive_write_add_filter_gzip(a);
	archive_write_set_format_ustar(a);
	}
	archive_write_open(a, mydata, myopen, mywrite, myclose);
	while (*filename) {
	stat(*filename, &st);
	entry = archive_entry_new();
	archive_entry_copy_stat(entry, &st);
	archive_entry_set_pathname(entry, *filename);
	archive_write_header(a, entry);
	if ((fd = open(*filename, O_RDONLY)) != -1) {
	len = read(fd, buff, sizeof(buff));
	while (len > 0) {
	archive_write_data(a, buff, len);
	len = read(fd, buff, sizeof(buff));
	}
	close(fd);
	}
	archive_entry_free(entry);
	filename++;
	}
	archive_write_free(a);
	}

	int main(int argc, const char **argv)
	{
	const char *outname;
	argv++;
	outname = *argv++;
	write_archive(outname, argv);
	return 0;
	}
	.Ed
	.Sh SEE ALSO
	.Xr tar 1 ,
	.Xr libarchive 3 ,
	.Xr archive_write_set_options 3 ,
	.Xr cpio 5 ,
	.Xr mtree 5 ,
	.Xr tar 5
	.Sh HISTORY
	The
	.Nm libarchive
	library first appeared in
	.Fx 5.3 .
	.Sh AUTHORS
	.An -nosplit
	The
	.Nm libarchive
	library was written by
	.An Tim Kientzle Aq kientzle@acm.org .
	.Sh BUGS
	There are many peculiar bugs in historic tar implementations that may cause
	certain programs to reject archives written by this library.
	For example, several historic implementations calculated header checksums
	incorrectly and will thus reject valid archives; GNU tar does not fully support
	pax interchange format; some old tar implementations required specific
	field terminations.
	.Pp
	The default pax interchange format eliminates most of the historic
	tar limitations and provides a generic key/value attribute facility
	for vendor-defined extensions.
	One oversight in POSIX is the failure to provide a standard attribute
	for large device numbers.
	This library uses
	.Dq SCHILY.devminor
	and
	.Dq SCHILY.devmajor
	for device numbers that exceed the range supported by the backwards-compatible
	ustar header.
	These keys are compatible with Joerg Schilling's
	.Nm star
	archiver.
	Other implementations may not recognize these keys and will thus be unable
	to correctly restore device nodes with large device numbers from archives
	created by this library.