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author | kientzle <kientzle@FreeBSD.org> | 2004-02-09 23:22:54 +0000 |
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committer | kientzle <kientzle@FreeBSD.org> | 2004-02-09 23:22:54 +0000 |
commit | af9413b539628b0758b4af66ffbb879fba49cc6d (patch) | |
tree | 20e1d80fd0a1d288a08af1696ee258bcd08f41d0 /lib/libarchive/archive_write.3 | |
parent | 6b6e533f7e91602d4ccb3353351eb9f816c2daf2 (diff) | |
download | FreeBSD-src-af9413b539628b0758b4af66ffbb879fba49cc6d.zip FreeBSD-src-af9413b539628b0758b4af66ffbb879fba49cc6d.tar.gz |
Initial import of libarchive.
What it is:
A library for reading and writing various streaming archive
formats, especially tar and cpio. Being a library, it should
be easy to incorporate into pkg_* tools, sysinstall, and any
other place that needs to read or write such archives.
Features:
* Full automatic detection of both compression and archive format.
* Extensible internal architecture to make it easy to add new formats.
* Support for "pax interchange format," a new POSIX-standard tar format
that eliminates essentially all of the restrictions of historic formats.
* BSD license
Thanks to: jkh for pushing me to start this work, gordon for
encouraging me to commit it, bde for answering endless style
questions, and many others for feedback and encouragement.
Status: Pretty good overall, though there are still a few rough edges and
the library could always use more testing. Feedback eagerly solicited.
Diffstat (limited to 'lib/libarchive/archive_write.3')
-rw-r--r-- | lib/libarchive/archive_write.3 | 368 |
1 files changed, 368 insertions, 0 deletions
diff --git a/lib/libarchive/archive_write.3 b/lib/libarchive/archive_write.3 new file mode 100644 index 0000000..2cebaab --- /dev/null +++ b/lib/libarchive/archive_write.3 @@ -0,0 +1,368 @@ +.\" Copyright (c) 2003-2004 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 October 1, 2003 +.Dt archive_write 3 +.Os +.Sh NAME +.Nm archive_write_new , +.Nm archive_write_set_format_cpio , +.Nm archive_write_set_format_pax , +.Nm archive_write_set_format_pax_restricted , +.Nm archive_write_set_format_shar , +.Nm archive_write_set_format_shar_binary , +.Nm archive_write_set_format_ustar , +.Nm archive_write_set_bytes_per_block , +.Nm archive_write_set_bytes_in_last_block , +.Nm archive_write_set_compressor_gzip , +.Nm archive_write_set_compressor_bzip2 , +.Nm archive_write_open , +.Nm archive_write_open_file , +.Nm archive_write_open_tar , +.Nm archive_write_prepare , +.Nm archive_write_header , +.Nm archive_write_data , +.Nm archive_write_finish +.Nd functions for creating archives +.Sh SYNOPSIS +.In archive.h +.Ft struct archive * +.Fn archive_write_new "void" +.Ft int +.Fn archive_write_set_bytes_per_block "archive *" "int bytes_per_block" +.Ft int +.Fn archive_write_set_bytes_in_last_block "archive *" "int" +.Ft int +.Fn archive_write_set_compressor_gzip "struct archive *" +.Ft int +.Fn archive_write_set_compressor_bzip2 "struct archive *" +.Ft int +.Fn archive_write_set_format_cpio "struct archive *" +.Ft int +.Fn archive_write_set_format_pax "struct archive *" +.Ft int +.Fn archive_write_set_format_pax_restricted "struct archive *" +.Ft int +.Fn archive_write_set_format_shar "struct archive *" +.Ft int +.Fn archive_write_set_format_shar_binary "struct archive *" +.Ft int +.Fn archive_write_set_format_ustar "struct archive *" +.Ft int +.Fn archive_write_open "struct archive *" "void *client_data" "archive_write_archive_callback *" "archive_open_archive_callback *" "archive_close_archive_callback *" +.Ft int +.Fn archive_write_open_file "struct archive *" "const char *filename" +.Ft int +.Fn archive_write_open_tar "struct archive *" "const char *archive_name" +.Ft int +.Fn archive_write_header "struct archive *" +.Ft int +.Fn archive_write_data "struct archive *" "const void *" "size_t" +.Ft int +.Fn archive_write_finish "struct archive *" +.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. +The following summary describes the functions in approximately +the order they are ordinarily used: +.Bl -tag -width indent +.It Fn archive_write_new +Allocates and initializes a +.Tn struct archive +object suitable for writing a tar archive. +.It Fn archive_write_set_bytes_per_block +Sets the block size used for writing the archive data. +Every call to the write callback function, except possibly the last one, will +use this value for the length. +The third parameter is a boolean that specifies whether or not the final block +written will be padded to the full block size. +If it is zero, the last block will not be padded. +If it is non-zero, padding will be added both before and after compression. +The default is to use a block size of 10240 bytes and to pad the last block. +.It Fn archive_write_set_bytes_in_last_block +Sets the block size used for writing the last block. +If this value is zero, the last block will be padded to the same size +as the other blocks. +Otherwise, the final block will be padded to a multiple of this size. +In particular, setting it to 1 will cause the final block to not be padded. +For compressed output, any padding generated by this option +is applied only after the compression. +The uncompressed data is always unpadded. +The default is to pad the last block to the full block size (note that +.Fn archive_write_open_file +affects this). +Unlike the other +.Dq set +functions, this function can be called after the archive is opened. +.It Fn archive_write_set_format_cpio , Fn archive_write_set_format_pax , Fn archive_write_set_format_pax_restricted , Fn archive_write_set_format_shar , Fn archive_write_set_format_shar_binary , Fn archive_write_set_format_ustar +Sets the format that will be used for the archive. +The library can write +POSIX octet-oriented cpio format archives, +POSIX-standard +.Dq pax interchange +format archives, +traditional +.Dq shar +archives, +enhanced +.Dq binary +shar archives that store a variety of file attributes and handle binary files, +and +POSIX-standard +.Dq ustar +archives. +The pax interchange format is a backwards-compatible tar format that +adds key/value attributes to each entry and supports arbitrary +filenames, linknames, uids, sizes, etc. +.Dq Restricted pax interchange format +is the library default; this is the same as pax format, but suppresses +the pax extended header for most normal files. +In most cases, this will result in ordinary ustar archives. +.It Fn archive_write_set_compression_gzip , Fn archive_write_set_compression_bzip2 +The resulting archive will be compressed as specified. +Note that the compressed output is always properly blocked. +.It Fn archive_write_open +Freeze the settings, open the archive, and prepare for writing entries. +This is the most generic form of this function, which accepts +pointers to three callback functions which will be invoked by +the library to write the constructed archive. +.It Fn archive_write_open_file +A convenience form of +.Fn archive_write_open +that accepts a filename. +A NULL argument indicates that the output should be written to standard output; +an argument of +.Dq - +will open a file with that name. +If you have not invoked +.Fn archive_write_set_bytes_in_last_block , +then +.Fn archive_write_open_file +will adjust the last-block padding depending on the file: +it will enable padding when writing to standard output or +to a character or block device node, it will disable padding otherwise. +You can override this by manually invoking +.Fn archive_write_set_bytes_in_last_block +either before or after calling +.Fn archive_write_open . +.It Fn archive_write_open_tar +A convenience form of +.Fn archive_write_open +that accepts an archive name in the same formats accepted by +.Xr tar 1 . +In particular, a +.Pa - +argument indicates that the output should be written to standard output. +.It Fn archive_write_header +Build and write a header using the data in the provided +.Tn struct archive_entry +structure. +.It Fn archive_write_data +Write data corresponding to the header just written. +.It Fn archive_write_finish +Complete the archive, invoke the close callback, and release +all resources. +.El +.Pp +The callback functions are defined as follows: +.Bl -item -offset indent +.It +.Ft typedef ssize_t +.Fn archive_write_archive_callback "struct archive *" "void *client_data" "void *buffer" "size_t length" +.It +.Ft typedef int +.Fn archive_open_archive_callback "struct archive *" "void *client_data" +.It +.Ft typedef int +.Fn archive_close_archive_callback "struct archive *" "void *client_data" +.El +For correct blocking, each call to the write callback function +should translate into a single +.Xr write 2 +system call. +This is especially critical when writing tar archives to tape drives. +.Pp +More information about tar archive formats and blocking can be found +in the +.Xr tar 5 +manual page. +.Pp +More information about the +.Va struct archive +object and the overall design of the library can be found in the +.Xr libarchive 3 +overview. +.Sh IMPLEMENTATION +Compression support is built-in to libarchive, which uses zlib and bzlib +to handle gzip and bzip2 compression, respectively. +.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 +void +write_archive(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; + + a = archive_write_new(); + mydata->name = name; + archive_write_set_compression_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); + fd = open(*filename, O_RDONLY); + len = read(fd, buff, sizeof(buff)); + while ( len >= 0 ) { + archive_write_data(a, buff, len); + len = read(fd, buff, sizeof(buff)); + } + archive_entry_free(entry); + filename++; + } + archive_write_finish(a); +} + +int +myopen(struct archive *a, void *client_data) +{ + struct mydata *mydata = client_data; + + mydata->fd = open(mydata->name, O_WRONLY | O_CREAT, 0644); + return (mydata->fd >= 0); +} + +ssize_t +mywrite(struct archive *a, void *client_data, 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); +} +.Ed +.Sh RETURN VALUES +Most functions return zero on success, non-zero on error. +The +.Fn archive_errno +and +.Fn archive_error_string +functions can be used to retrieve an appropriate error code and a +textual error message. +.Pp +.Fn archive_write_new +returns a pointer to a newly-allocated +.Tn struct archive +object. +.Pp +.Fn archive_write_data +returns a count of the number of bytes actually written. +On error, -1 is returned and the +.Fn archive_errno +and +.Fn archive_error_string +functions will return appropriate values. +Note that if the client-provided write callback function +returns -1, that error will be propagated back to the caller +through whatever API function resulted in that call, which +may include +.Fn archive_write_header , +.Fn archive_write_data , +or +.Fn archive_write_finish . +In such a case, the +.Fn archive_errno +or +.Fn archive_error_string +fields will not return useful information; you should use +client-private data to return error information +back to your mainline code. +.Sh SEE ALSO +.Xr tar 1 , +.Xr libarchive 3 , +.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 large device numbers archived by this library. |