X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=ext%2FDB_File%2FDB_File.pm;h=0491d6bb4299c5a3b8c5f242f595431ed77f2ff7;hb=8e07c86ebc651fe92eb7e3b25f801f57cfb8dd6f;hp=4cff8da4a975f550397610942ef6f179b9e168e2;hpb=fec02dd38faf8f83471b031857d89cb76fea1ca0;p=p5sagit%2Fp5-mst-13.2.git diff --git a/ext/DB_File/DB_File.pm b/ext/DB_File/DB_File.pm index 4cff8da..0491d6b 100644 --- a/ext/DB_File/DB_File.pm +++ b/ext/DB_File/DB_File.pm @@ -1,8 +1,8 @@ # DB_File.pm -- Perl 5 interface to Berkeley DB # # written by Paul Marquess (pmarquess@bfsec.bt.co.uk) -# last modified 23rd June 1994 -# version 0.1 +# last modified 7th October 1995 +# version 1.0 package DB_File::HASHINFO ; use Carp; @@ -170,6 +170,8 @@ sub CLEAR { croak "DB_File::BTREEINFO::CLEAR is not implemented" } package DB_File ; use Carp; +$VERSION = 1.0 ; + #typedef enum { DB_BTREE, DB_HASH, DB_RECNO } DBTYPE; $DB_BTREE = TIEHASH DB_File::BTREEINFO ; $DB_HASH = TIEHASH DB_File::HASHINFO ; @@ -177,7 +179,7 @@ $DB_RECNO = TIEHASH DB_File::RECNOINFO ; require TieHash; require Exporter; -require AutoLoader; +use AutoLoader; require DynaLoader; @ISA = qw(TieHash Exporter DynaLoader); @EXPORT = qw( @@ -213,10 +215,6 @@ require DynaLoader; ); sub AUTOLOAD { - if (@_ > 1) { - $AutoLoader::AUTOLOAD = $AUTOLOAD; - goto &AutoLoader::AUTOLOAD; - } local($constname); ($constname = $AUTOLOAD) =~ s/.*:://; $val = constant($constname, @_ ? $_[0] : 0); @@ -246,3 +244,353 @@ bootstrap DB_File @liblist; 1; __END__ + +=cut + +=head1 NAME + +DB_File - Perl5 access to Berkeley DB + +=head1 SYNOPSIS + + use DB_File ; + + [$X =] tie %hash, DB_File, $filename [, $flags, $mode, $DB_HASH] ; + [$X =] tie %hash, DB_File, $filename, $flags, $mode, $DB_BTREE ; + [$X =] tie @array, DB_File, $filename, $flags, $mode, $DB_RECNO ; + + $status = $X->del($key [, $flags]) ; + $status = $X->put($key, $value [, $flags]) ; + $status = $X->get($key, $value [, $flags]) ; + $status = $X->seq($key, $value [, $flags]) ; + $status = $X->sync([$flags]) ; + $status = $X->fd ; + + untie %hash ; + untie @array ; + +=head1 DESCRIPTION + +B is a module which allows Perl programs to make use of the +facilities provided by Berkeley DB. If you intend to use this +module you should really have a copy of the Berkeley DB manualpage at +hand. The interface defined here mirrors the Berkeley DB interface +closely. + +Berkeley DB is a C library which provides a consistent interface to a +number of database formats. B provides an interface to all +three of the database types currently supported by Berkeley DB. + +The file types are: + +=over 5 + +=item DB_HASH + +This database type allows arbitrary key/data pairs to be stored in data +files. This is equivalent to the functionality provided by other +hashing packages like DBM, NDBM, ODBM, GDBM, and SDBM. Remember though, +the files created using DB_HASH are not compatible with any of the +other packages mentioned. + +A default hashing algorithm, which will be adequate for most +applications, is built into Berkeley DB. If you do need to use your own +hashing algorithm it is possible to write your own in Perl and have +B use it instead. + +=item DB_BTREE + +The btree format allows arbitrary key/data pairs to be stored in a +sorted, balanced binary tree. + +As with the DB_HASH format, it is possible to provide a user defined +Perl routine to perform the comparison of keys. By default, though, the +keys are stored in lexical order. + +=item DB_RECNO + +DB_RECNO allows both fixed-length and variable-length flat text files +to be manipulated using the same key/value pair interface as in DB_HASH +and DB_BTREE. In this case the key will consist of a record (line) +number. + +=back + +=head2 How does DB_File interface to Berkeley DB? + +B allows access to Berkeley DB files using the tie() mechanism +in Perl 5 (for full details, see L). This facility +allows B to access Berkeley DB files using either an +associative array (for DB_HASH & DB_BTREE file types) or an ordinary +array (for the DB_RECNO file type). + +In addition to the tie() interface, it is also possible to use most of +the functions provided in the Berkeley DB API. + +=head2 Differences with Berkeley DB + +Berkeley DB uses the function dbopen() to open or create a database. +Below is the C prototype for dbopen(). + + DB* + dbopen (const char * file, int flags, int mode, + DBTYPE type, const void * openinfo) + +The parameter C is an enumeration which specifies which of the 3 +interface methods (DB_HASH, DB_BTREE or DB_RECNO) is to be used. +Depending on which of these is actually chosen, the final parameter, +I points to a data structure which allows tailoring of the +specific interface method. + +This interface is handled slightly differently in B. Here is +an equivalent call using B. + + tie %array, DB_File, $filename, $flags, $mode, $DB_HASH ; + +The C, C and C parameters are the direct +equivalent of their dbopen() counterparts. The final parameter $DB_HASH +performs the function of both the C and C parameters in +dbopen(). + +In the example above $DB_HASH is actually a reference to a hash +object. B has three of these pre-defined references. Apart +from $DB_HASH, there is also $DB_BTREE and $DB_RECNO. + +The keys allowed in each of these pre-defined references is limited to +the names used in the equivalent C structure. So, for example, the +$DB_HASH reference will only allow keys called C, C, +C, C, C and C. + +To change one of these elements, just assign to it like this + + $DB_HASH{cachesize} = 10000 ; + + +=head2 RECNO + + +In order to make RECNO more compatible with Perl the array offset for all +RECNO arrays begins at 0 rather than 1 as in Berkeley DB. + + +=head2 In Memory Databases + +Berkeley DB allows the creation of in-memory databases by using NULL +(that is, a C<(char *)0 in C) in place of the filename. B +uses C instead of NULL to provide this functionality. + + +=head2 Using the Berkeley DB Interface Directly + +As well as accessing Berkeley DB using a tied hash or array, it is also +possible to make direct use of most of the functions defined in the +Berkeley DB documentation. + + +To do this you need to remember the return value from the tie. + + $db = tie %hash, DB_File, "filename" + +Once you have done that, you can access the Berkeley DB API functions +directly. + + $db->put($key, $value, R_NOOVERWRITE) ; + +All the functions defined in L are available except for +close() and dbopen() itself. The B interface to these +functions have been implemented to mirror the the way Berkeley DB +works. In particular note that all the functions return only a status +value. Whenever a Berkeley DB function returns data via one of its +parameters, the B equivalent does exactly the same. + +All the constants defined in L are also available. + +Below is a list of the functions available. + +=over 5 + +=item get + +Same as in C except that the flags parameter is optional. +Remember the value associated with the key you request is returned in +the $value parameter. + +=item put + +As usual the flags parameter is optional. + +If you use either the R_IAFTER or R_IBEFORE flags, the key parameter +will have the record number of the inserted key/value pair set. + +=item del + +The flags parameter is optional. + +=item fd + +As in I. + +=item seq + +The flags parameter is optional. + +Both the key and value parameters will be set. + +=item sync + +The flags parameter is optional. + +=back + +=head1 EXAMPLES + +It is always a lot easier to understand something when you see a real +example. So here are a few. + +=head2 Using HASH + + use DB_File ; + use Fcntl ; + + tie %h, "DB_File", "hashed", O_RDWR|O_CREAT, 0640, $DB_HASH ; + + # Add a key/value pair to the file + $h{"apple"} = "orange" ; + + # Check for existence of a key + print "Exists\n" if $h{"banana"} ; + + # Delete + delete $h{"apple"} ; + + untie %h ; + +=head2 Using BTREE + +Here is sample of code which used BTREE. Just to make life more +interesting the default comparision function will not be used. Instead +a Perl sub, C, will be used to do a case insensitive +comparison. + + use DB_File ; + use Fcntl ; + + sub Compare + { + my ($key1, $key2) = @_ ; + + "\L$key1" cmp "\L$key2" ; + } + + $DB_BTREE->{compare} = 'Compare' ; + + tie %h, 'DB_File', "tree", O_RDWR|O_CREAT, 0640, $DB_BTREE ; + + # Add a key/value pair to the file + $h{'Wall'} = 'Larry' ; + $h{'Smith'} = 'John' ; + $h{'mouse'} = 'mickey' ; + $h{'duck'} = 'donald' ; + + # Delete + delete $h{"duck"} ; + + # Cycle through the keys printing them in order. + # Note it is not necessary to sort the keys as + # the btree will have kept them in order automatically. + foreach (keys %h) + { print "$_\n" } + + untie %h ; + +Here is the output from the code above. + + mouse + Smith + Wall + + +=head2 Using RECNO + + use DB_File ; + use Fcntl ; + + $DB_RECNO->{psize} = 3000 ; + + tie @h, DB_File, "text", O_RDWR|O_CREAT, 0640, $DB_RECNO ; + + # Add a key/value pair to the file + $h[0] = "orange" ; + + # Check for existence of a key + print "Exists\n" if $h[1] ; + + untie @h ; + + + +=head1 CHANGES + +=head2 0.1 + +First Release. + +=head2 0.2 + +When B is opening a database file it no longer terminates the +process if I returned an error. This allows file protection +errors to be caught at run time. Thanks to Judith Grass + for spotting the bug. + +=head2 0.3 + +Added prototype support for multiple btree compare callbacks. + +=head 1.0 + +B has been in use for over a year. To reflect that, the +version number has been incremented to 1.0. + +Added complete support for multiple concurrent callbacks. + +Using the I method on an empty list didn't work properly. This +has been fixed. + +=head1 WARNINGS + +If you happen find any other functions defined in the source for this +module that have not been mentioned in this document -- beware. I may +drop them at a moments notice. + +If you cannot find any, then either you didn't look very hard or the +moment has passed and I have dropped them. + +=head1 BUGS + +Some older versions of Berkeley DB had problems with fixed length +records using the RECNO file format. The newest version at the time of +writing was 1.85 - this seems to have fixed the problems with RECNO. + +I am sure there are bugs in the code. If you do find any, or can +suggest any enhancements, I would welcome your comments. + +=head1 AVAILABILITY + +Berkeley DB is available via the hold C in the +directory C. It is I under the GPL. + +=head1 SEE ALSO + +L, L, L, L, L + +Berkeley DB is available from F in the directory +F. + +=head1 AUTHOR + +The DB_File interface was written by Paul Marquess +. +Questions about the DB system itself may be addressed to Keith Bostic +. + +=cut