erl_tar.erl

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%% ``The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved via the world wide web at http://www.erlang.org/.
%% 
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and limitations
%% under the License.
%% 
%% The Initial Developer of the Original Code is Ericsson Utvecklings AB.
%% Portions created by Ericsson are Copyright 1999, Ericsson Utvecklings
%% AB. All Rights Reserved.''
%% 
%%     $Id$
%%
-module(erl_tar).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Purpose: Unix tar (tape archive) utility.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

-export([create/2, create/3, extract/1, extract/2, table/1, table/2,
	 open/2, close/1, add/3, add/4,
	 t/1, tt/1, format_error/1]).

-include_lib("kernel/include/file.hrl").

-record(add_opts,
	{read_info,				% Fun to use for read file/link info.
	 verbose = false}).			% Verbose on/off.

%% Opens a tar archive.

open(Name, Mode) ->
    case open_mode(Mode) of
	{ok, Access, Raw, Opts} ->
	    open1(Name, Access, Raw, Opts);
	{error, Reason} ->
	    {error, {Name, Reason}}
    end.

open1({binary,Bin}, read, _Raw, Opts) ->
    case file:open(Bin, [ram,binary,read]) of
	{ok,File} ->
	    case Opts of
		[compressed] -> ram_file:uncompress(File);
		[] -> ok
	    end,
	    {ok,{read,File}};
	Error ->
	    Error
    end;
open1({file, Fd}, read, _Raw, _Opts) ->
    {ok, {read, Fd}};
open1(Name, Access, Raw, Opts) ->
    case file:open(Name, Raw ++ [binary, Access|Opts]) of
	{ok, File} ->
	    {ok, {Access, File}};
	{error, Reason} ->
	    {error, {Name, Reason}}
    end.

%% Closes a tar archive.

close({read, File}) ->
    file:close(File),
    ok;
close({write, File}) ->
    PadResult = pad_file(File),
    file:close(File),
    PadResult;
close(_) ->
    {error, einval}.

%% Adds a file to a tape archive.

add(File, Name, Options) ->
    add(File, Name, Name, Options).

add({write, File}, Name, NameInArchive, Options) ->
    Opts = #add_opts{read_info=fun(F) -> file:read_link_info(F) end},
    add1(File, Name, NameInArchive, add_opts(Options, Opts));
add({read, _File}, _, _, _) ->
    {error, eacces};
add(_, _, _, _) ->
    {error, einval}.

add_opts([dereference|T], Opts) ->
    add_opts(T, Opts#add_opts{read_info=fun(F) -> file:read_file_info(F) end});
add_opts([verbose|T], Opts) ->
    add_opts(T, Opts#add_opts{verbose=true});
add_opts([_|T], Opts) ->
    add_opts(T, Opts);
add_opts([], Opts) ->
    Opts.

%% Creates a tar file Name containing the given files.

create(Name, Filenames) ->
    create(Name, Filenames, []).

%% Creates a tar archive Name containing the given files.
%% Accepted options: verbose, compressed, cooked

create(Name, FileList, Options) ->
    Mode = lists:filter(fun(X) -> (X=:=compressed) or (X=:=cooked) 
                        end, Options),
    case open(Name, [write|Mode]) of
	{ok, TarFile} ->
	    Add = fun(Nm) -> add(TarFile, Nm, Nm, Options) end,
	    Result = foreach_while_ok(Add, FileList),
	    case {Result, close(TarFile)} of
		{ok, Res} -> Res;
		{Res, _} -> Res
	    end;
	Reason ->
	    Reason
    end.

%% Extracts all files from the tar file Name.

extract(Name) ->
    extract(Name, []).

%% Extracts (all) files from the tar file Name.
%% Options accepted: keep_old_files, {files, ListOfFilesToExtract}, verbose,
%%		{cwd, AbsoluteDirectory}

extract(Name, Opts) ->
    case foldl_read(Name, fun extract1/4, [], extract_opts(Opts)) of
	[] ->
	    ok;
	Other ->
	    Other
    end.

%% Returns a list of names of the files in the tar file Name.
%% Options accepted: verbose

table(Name) ->
    table(Name, []).

%% Returns a list of names of the files in the tar file Name.
%% Options accepted: compressed, verbose, cooked.

table(Name, Opts) ->
    foldl_read(Name, fun table1/4, [], table_opts(Opts)).


%% Comments for printing the contents of a tape archive,
%% meant to be invoked from the shell.

t(Name) ->
    case table(Name) of
	{ok, List} ->
	    lists:foreach(fun(N) -> ok = io:format("~s\n", [N]) end, List);
	Error ->
	    Error
    end.

tt(Name) ->
    case table(Name, [verbose]) of
	{ok, List} ->
	    lists:foreach(fun print_header/1, List);
	Error ->
	    Error
    end.

print_header({Name, Type, Size, Mtime, Mode, Uid, Gid}) ->
    io:format("~s~s ~4w/~-4w ~7w ~s ~s\n",
	      [type_to_string(Type), mode_to_string(Mode),
	       Uid, Gid, Size, time_to_string(Mtime), Name]).

type_to_string(regular) -> "-";
type_to_string(directory) -> "d";
type_to_string(link) -> "l";
type_to_string(symlink) -> "s";
type_to_string(char) -> "c";
type_to_string(block) -> "b";
type_to_string(fifo) -> "f";
type_to_string(_) -> "?".

mode_to_string(Mode) ->
    mode_to_string(Mode, "xwrxwrxwr", []).

mode_to_string(Mode, [C|T], Acc) when Mode band 1 =:= 1 ->
    mode_to_string(Mode bsr 1, T, [C|Acc]);
mode_to_string(Mode, [_|T], Acc) ->
    mode_to_string(Mode bsr 1, T, [$-|Acc]);
mode_to_string(_, [], Acc) ->
    Acc.

time_to_string({{Y, Mon, Day}, {H, Min, _}}) ->
    io_lib:format("~s ~2w ~s:~s ~w", [month(Mon), Day, two_d(H), two_d(Min), Y]).

two_d(N) ->
    tl(integer_to_list(N + 100)).

month(1) -> "Jan";
month(2) -> "Feb";
month(3) -> "Mar";
month(4) -> "Apr";
month(5) -> "May";
month(6) -> "Jun";
month(7) -> "Jul";
month(8) -> "Aug";
month(9) -> "Sep";
month(10) -> "Oct";
month(11) -> "Nov";
month(12) -> "Dec".

%% Converts the short error reason to a descriptive string.

format_error(bad_header) -> "Bad directory header";
format_error(eof) -> "Unexpected end of file";
format_error(symbolic_link_too_long) -> "Symbolic link too long";
format_error({Name,Reason}) ->
    lists:flatten(io_lib:format("~s: ~s", [Name,format_error(Reason)]));
format_error(Atom) when is_atom(Atom) ->
    file:format_error(Atom);
format_error(Term) ->
    lists:flatten(io_lib:format("~p", [Term])).


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%
%%%	Useful definitions (also start of implementation).
%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% Offset for fields in the tar header.
%% Note that these offsets are ZERO-based as in the POSIX standard
%% document, while binaries use ONE-base offset.  Caveat Programmer.

-define(th_name, 0).
-define(th_mode, 100).
-define(th_uid, 108).
-define(th_gid, 116).
-define(th_size, 124).
-define(th_mtime, 136).
-define(th_chksum, 148).
-define(th_typeflag, 156).
-define(th_linkname, 157).
-define(th_magic, 257).
-define(th_version, 263).
-define(th_prefix, 345).

%% Length of these fields.

-define(th_name_len, 100).
-define(th_mode_len, 8).
-define(th_uid_len, 8).
-define(th_gid_len, 8).
-define(th_size_len, 12).
-define(th_mtime_len, 12).
-define(th_chksum_len, 8).
-define(th_linkname_len, 100).
-define(th_magic_len, 6).
-define(th_version_len, 2).
-define(th_prefix_len, 167).

-record(tar_header,
	{name,					% Name of file.
	 mode,					% Mode bits.
	 uid,					% User id.
	 gid,					% Group id.
	 size,					% Size of file
	 mtime,					% Last modified (seconds since
						% Jan 1, 1970).
	 chksum,				% Checksum of header.
	 typeflag = [],				% Type of file.
	 linkname = [],				% Name of link.
	 filler = [],
	 prefix}).				% Filename prefix.

-define(record_size, 512).
-define(block_size, (512*20)).



%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%
%%% 	Adding members to a tar archive.
%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

add1(TarFile, Name, NameInArchive, Opts) ->
    case read_file_and_info(Name, Opts) of
	{ok, Bin, Info} when Info#file_info.type =:= regular ->
	    Header = create_header(NameInArchive, Info),
	    add1(TarFile, Name, Header, Bin, Opts);
	{ok, PointsTo, Info} when Info#file_info.type =:= symlink ->
	    if
		length(PointsTo) > 100 ->
		    {error,{PointsTo,symbolic_link_too_long}};
		true ->
		    Info2 = Info#file_info{size=0},
		    Header = create_header(NameInArchive, Info2, PointsTo),
		    add1(TarFile, Name, Header, list_to_binary([]), Opts)
	    end;
	{ok, _, Info} when Info#file_info.type =:= directory ->
	    add_directory(TarFile, Name, NameInArchive, Info, Opts);
	{ok, _, #file_info{type=Type}} ->
	    {error, {bad_file_type, Name, Type}};
	{error, Reason} ->
	    {error, {Name, Reason}}
    end.

add1(Tar, Name, Header, Bin, Options) ->
    add_verbose(Options, "a ~s~n", [Name]),
    file:write(Tar, [Header, Bin, padding(size(Bin), ?record_size)]).

add_directory(TarFile, DirName, NameInArchive, Info, Options) ->
    case file:list_dir(DirName) of
	{ok, []} ->
	    add_verbose(Options, "a ~s~n", [DirName]),
	    Header = create_header(NameInArchive, Info),
	    file:write(TarFile, Header);
	{ok, Files} ->
	    Add = fun (File) ->
			  add1(TarFile,
			       filename:join(DirName, File),
			       filename:join(NameInArchive, File),
			       Options) end,
	    foreach_while_ok(Add, Files);
	{error, Reason} ->
	    {error, {DirName, Reason}}
    end.
    
%% Creates a header for file in a tar file.

create_header(Name, Info) ->
    create_header(Name, Info, []).
create_header(Name, #file_info {mode=Mode, uid=Uid, gid=Gid,
				size=Size, mtime=Mtime0, type=Type}, Linkname) ->
    Mtime = posix_time(erlang:localtime_to_universaltime(Mtime0)),
    {Prefix,Suffix} = split_filename(Name),
    H0 = [to_string(Suffix, 100),
	  to_octal(Mode, 8),
	  to_octal(Uid, 8),
	  to_octal(Gid, 8),
	  to_octal(Size, ?th_size_len),
	  to_octal(Mtime, ?th_mtime_len),
	  <<"        ">>,
	  file_type(Type),
	  to_string(Linkname, ?th_linkname_len),
	  "ustar",0,
	  "00",
	  zeroes(?th_prefix-?th_version-?th_version_len),
	  to_string(Prefix, ?th_prefix_len)],
    H = list_to_binary(H0),
    512 = size(H),				%Assertion.
    ChksumString = to_octal(checksum(H), 6, [0,$\s]),
    <<Before:?th_chksum/binary,_:?th_chksum_len/binary,After/binary>> = H,
    [Before,ChksumString|After].


file_type(regular) -> $0;
file_type(symlink) -> $2;
file_type(directory) -> $5.
    
to_octal(Int, Count) when Count > 1 ->
    to_octal(Int, Count-1, [0]).

to_octal(_, 0, Result) -> Result;
to_octal(Int, Count, Result) ->
    to_octal(Int div 8, Count-1, [Int rem 8 + $0|Result]).

to_string(Str0, Count) ->
    Str = list_to_binary(Str0),
    case size(Str) of
	Size when Size < Count ->
	    [Str|zeroes(Count-Size)];
	_ -> Str
    end.

%% Pads out end of file.

pad_file(File) ->
    {ok,Position} = file:position(File, {cur,0}),
    %% There must be at least one empty record at the end of the file.
    Zeros = zeroes(?block_size - (Position rem ?block_size)),
    file:write(File, Zeros).

split_filename(Name) when length(Name) =< ?th_name_len ->
    {"", Name};
split_filename(Name0) ->
    split_filename(lists:reverse(filename:split(Name0)), [], [], 0).

split_filename([Comp|Rest], Prefix, Suffix, Len) 
  when Len+length(Comp) < ?th_name_len ->
    split_filename(Rest, Prefix, [Comp|Suffix], Len+length(Comp)+1);
split_filename([Comp|Rest], Prefix, Suffix, Len) ->
    split_filename(Rest, [Comp|Prefix], Suffix, Len+length(Comp)+1);
split_filename([], Prefix, Suffix, _) ->
    {filename:join(Prefix),filename:join(Suffix)}.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%
%%% 	Retrieving files from a tape archive.
%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% Options used when reading a tar archive.

-record(read_opts,
	{cwd,					% Current working directory.
	 keep_old_files = false,		% Owerwrite or not.
	 files = all,				% Set of files to extract
						% (or all).
	 open_mode = [],			% Open mode options.
	 verbose = false}).			% Verbose on/off.

extract_opts(List) ->
    extract_opts(List, default_options()).

table_opts(List) ->
    read_opts(List, default_options()).

default_options() ->
    {ok, Cwd} = file:get_cwd(),
    #read_opts{cwd=Cwd}.

%% Parse options for extract.

extract_opts([keep_old_files|Rest], Opts) ->
    extract_opts(Rest, Opts#read_opts{keep_old_files=true});
extract_opts([{cwd, Cwd}|Rest], Opts) ->
    extract_opts(Rest, Opts#read_opts{cwd=Cwd});
extract_opts([{files, Files}|Rest], Opts) ->
    Set = ordsets:from_list(Files),
    extract_opts(Rest, Opts#read_opts{files=Set});
extract_opts([compressed|Rest], Opts=#read_opts{open_mode=OpenMode}) ->
    extract_opts(Rest, Opts#read_opts{open_mode=[compressed|OpenMode]});
extract_opts([cooked|Rest], Opts=#read_opts{open_mode=OpenMode}) ->
    extract_opts(Rest, Opts#read_opts{open_mode=[cooked|OpenMode]});
extract_opts([verbose|Rest], Opts) ->
    extract_opts(Rest, Opts#read_opts{verbose=true});
extract_opts([Other|Rest], Opts) ->
    extract_opts(Rest, read_opts([Other], Opts));
extract_opts([], Opts) ->
    Opts.

%% Common options for all read operations.

read_opts([compressed|Rest], Opts=#read_opts{open_mode=OpenMode}) ->
    read_opts(Rest, Opts#read_opts{open_mode=[compressed|OpenMode]});
read_opts([cooked|Rest], Opts=#read_opts{open_mode=OpenMode}) ->
    read_opts(Rest, Opts#read_opts{open_mode=[cooked|OpenMode]});
read_opts([verbose|Rest], Opts) ->
    read_opts(Rest, Opts#read_opts{verbose=true});
read_opts([_|Rest], Opts) ->
    read_opts(Rest, Opts);
read_opts([], Opts) ->
    Opts.

foldl_read(TarName, Fun, Accu, Opts) ->
    case open(TarName, [read|Opts#read_opts.open_mode]) of