Fixed\-length database has restrictions that each key should be a natural number and that the length of each value is limited.  However, time efficiency and space efficiency are higher than the other data structures as long as the use case is within the restriction..PPBecause the whole region of the database is mapped on memory by the `mmap' call and referred as a multidimensional array, the overhead related to the file I/O is minimized.  Due to this simple structure, fixed\-length database works faster than hash database, and its concurrency in multi\-thread environment is prominent..PPThe size of the database is proportional to the range of keys and the limit size of each value.  That is, the smaller the range of keys is or the smaller the length of each value is, the higher the space efficiency is.  For example, if the maximum key is 1000000 and the limit size of the value is 100 bytes, the size of the database will be about 100MB.  Because regions around referred records are only loaded on the RAM, you can increase the size of the database to the size of the virtual memory..SH FLEXIBLE IMPLEMENTATION OF TABLE DATABASE.PPTable database does not express simple key/value structure but expresses a structure like a table of relational database.  Each record is identified by the primary key and has a set of multiple columns named with arbitrary strings.  For example, a stuff in your company can be expressed by a record identified by the primary key of the employee ID number and structured by columns of his name, division, salary, and so on.  Unlike relational database, table database does not need to define any data schema and can contain records of various structures different from each other..PPTable database supports query functions with not only the primary key but also with conditions about arbitrary columns.  Each column condition is composed of the name of a column and a condition expression.  Operators of full matching, forward matching, regular expression matching, and so on are provided for the string type.  Operators of full matching, range matching and so on are provided for the number type.  A query can contain multiple conditions.  The order of the result set can be specified as the ascending or descending order of strings or numbers..PPYou can create indices for arbitrary columns to improve performance of search and sorting.  Although columns do not have data types, indices have types for strings or numbers.  The query optimizer uses indices in suitable way according to each query.  Indices are implemented as different files of B+ tree database..SH PRACTICAL FUNCTIONALITY.PPDatabases on the filesystem feature transaction mechanisms.  It is possible to commit a series of operations between the beginning and the end of the transaction in a lump, or to abort the transaction and perform rollback to the state before the transaction.  Two isolation levels are supported; serializable and read uncommitted.  Durability is secured by write ahead logging and shadow paging..PPTokyo Cabinet provides two modes to connect to a database: `reader' and `writer'.  A reader can perform retrieving but neither storing nor deleting.  A writer can perform all access methods.  Exclusion control between processes is performed when connecting to a database by file locking.  While a writer is connected to a database, neither readers nor writers can be connected.  While a reader is connected to a database, other readers can be connect, but writers can not.  According to this mechanism, data consistency is guaranteed with simultaneous connections in multitasking environment..PPFunctions of API of Tokyo cabinet are reentrant and available in multi\-thread environment.  Discrete database object can be operated in parallel entirely.  For simultaneous operations of the same database object, read\-write lock is used for exclusion control.  That is, while a writing thread is operating the database, other reading threads and writing threads are blocked.  However, while a reading thread is operating the database, reading threads are not blocked..SH SIMPLE BUT VARIOUS INTERFACES.PPTokyo Cabinet provides simple API based on the object oriented design.  Every operation for database is encapsulated and published as lucid methods as `open' (connect), `close' (disconnect), `put' (insert), `out' (remove), `get' (retrieve), and so on.  Because the three of hash, B+ tree, and fixed-length array database APIs are very similar with each other, porting an application from one to the other is easy.  Moreover, the abstract API is provided to handle these databases with the same interface.  Applications of the abstract API can determine the type of the database in runtime..PPThe utility API is also provided.  Such fundamental data structure as list and map are included.  And, some useful features; memory pool, string processing, encoding, are also included..PPSix kinds of API; the utility API, the hash database API, the B+ tree database API, the fixed\-length database API, the table database API, and the abstract database API, are provided for the C language.  Command line interfaces are also provided corresponding to each API.  They are useful for prototyping, test, and debugging.  Except for C, Tokyo Cabinet provides APIs for Perl, Ruby, Java, and Lua.  APIs for other languages will hopefully be provided by third party..PPIn cases that multiple processes access a database at the same time or some processes access a database on a remote host, the remote service is useful.  The remote service is composed of a database server and its access library.  Applications can access the database server by using the remote database API.  The server implements HTTP and the memcached protocol partly so that client programs on almost all platforms can access the server easily..SH HOW TO USE THE LIBRARY.PPTokyo Cabinet provides API of the C language and it is available by programs conforming to the C89 (ANSI C) standard or the C99 standard.  As the header files of Tokyo Cabinet are provided as `\fBtcutil.h\fR', `\fBtchdb.h\fR', and `\fBtcbdb.h\fR', applications should include one or more of them accordingly to use the API.  As the library is provided as `\fBlibtokyocabinet.a\fR' and `\fBlibtokyocabinet.so\fR' and they depends `\fBlibz.so\fR', `\fBlibrt.so\fR', `\fBlibpthread.so\fR', `\fBlibm.so\fR', and `\fBlibc.so\fR', linker options `\fB\-ltokyocabinet\fR', `\fB\-lz\fR', `\fB\-lbz2\fR', `\fB\-lrt\fR', `\fB\-lpthread\fR', `\fB\-lm\fR', and `\fB\-lc\fR' are required for build command.  A typical build command is the following..PP.RSgcc \-I/usr/local/include tc_example.c \-o tc_example \\.br  \-L/usr/local/lib \-ltokyocabinet \-lz \-lbz2 \-lrt \-lpthread \-lm \-lc.RE.PPYou can also use Tokyo Cabinet in programs written in C++.  Because each header is wrapped in C linkage (`\fBextern "C"\fR' block), you can simply include them into your C++ programs..SH LICENSE.PPTokyo Cabinet is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License or any later version..PPTokyo Cabinet is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details..PPYou should have received a copy of the GNU Lesser General Public License along with Tokyo Cabinet (See the file `\fBCOPYING\fR'); if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111\-1307 USA..PPTokyo Cabinet was written by Mikio Hirabayashi.  You can contact the author by e\-mail to `\fBmikio@users.sourceforge.net\fR'..SH SEE ALSO.PP.BR tcutil (3),.BR tchdb (3),.BR tcbdb (3),.BR tcfdb (3),.BR tctdb (3),.BR tcadb (3).PPPlease see.I http://tokyocabinet.sourceforge.net/spex\-en.htmlfor detail.