Provided by: db6.0-util_6.0.19-3ubuntu1_amd64 
NAME
db6.0_codegen — generate application code for Berkeley DB
SYNOPSIS
db6.0_codegen [-Vv] [-a api] [-i file] [-o prefix]
DESCRIPTION
The db6.0_codegen utility generates application code to create and configure Berkeley DB
database environments and databases based on a simple description language and writes it to
one or more output files. The generated code may need modification, in the case of
complicated applications, but will usually significantly reduce the time required to create
Berkeley DB applications.
The options are as follows:
-a api
Generate code for the specified API (currently, only “c” is accepted).
-i file
Specify an input file; by default, standard input is used.
-o prefix
Specify an output file prefix; by default, “application” is used.
-V Write the library version number to standard output and exit.
-v Run in verbose mode.
The db6.0_codegen utility exits 0 on success, and >0 if an error occurs.
C Language Specific Information
By default, when the db6.0_codegen utility generates C-language code, the output file is
named “application.c”. The output filename can be specified with the -o option.
At the beginning of the output file is a list of public database environment (DB_ENV)
handles and database (DB) handles, as specified by the description language. The database
environment handle variables are named “XXX_dbenv”, where “XXX” is the name of the
environment in the input specification. For databases associated with a database
environment, the database handle variables are named “XXX_YYY”, where “XXX” is the name of
the environment, and “YYY” is the name of the database. For standalone databases, the
database handle variables are named “XXX”, where “XXX” is the name of the database.
There are two public functions in the output file: bdb_startup() and bdb_shutdown(). The
bdb_startup() function should be called to create and configure the database environments
and databases, and the bdb_shutdown() function should be called to gracefully shut down the
environments and databases.
Specification Language
The db6.0_codegen uses a simple description language:
• Lines in the input consist of white-space separated tokens.
• Tokens are case-insensitive.
• Empty lines and lines where the first non-space character is a hash mark (“#”) are
ignored. In addition, hash marks may appear in lines, in which case the content of the
line from the hash mark to the end of the line is ignored.
There are two top-level objects: “environment” and “database”, which correspond to database
environments and databases, respectively. These top-level objects can be associated with
keywords to describe their configuration and relationships.
For example, the following input would create two standalone databases:
database data_one {
type btree
}
database data_two {
type btree
}
In this case, there would be no DB_ENV handle, and the public DB handles would be:
DB *data_one;
DB *data_two;
For example, the following input would create a database environment which contains three
databases:
environment myenv {
database data_one {
type btree
}
database data_two {
type btree
}
database data_three {
type btree
}
}
In this case, the public DB_ENV and DB handles would be:
DB_ENV *myenv_dbenv;
DB *myenv_data_one;
DB *myenv_data_two;
DB *myenv_data_three;
A variety of keywords can be specified for the databases and the environments. For example,
the cache size can be specified for the database environment, and the page size can be
specified for the database, as well as for secondary relationships:
environment myenv {
cachesize 2 0 10
database data_one {
type btree
pagesize 1024
}
database data_two {
primary data_one
secondary_offset 10 15
type btree
pagesize 32768
}
database data_three {
type btree
pagesize 512
}
}
Environment Keywords
environment Start a database environment block.
There must be three tokens on the line: the keyword, the name of the
environment and an opening brace (“{”).
home Specify the database environment home directory.
There must be two tokens on the line: the keyword and the home directory.
cachesize Specify the database environment cache size.
There must be two tokens on the line: the keyword, the gigabytes of cache,
the bytes of cache, and the number of caches (the number of underlying
physical areas into which the cache is logically divided).
private Specify the database environment is private.
There must be one token on the line: the keyword by itself.
} End the database environment block.
There must be one token on the line: the keyword by itself.
Database Keywords
database Start a database block.
There must be three tokens on the line: the keyword, the name of the
database and an opening brace (“{”).
custom Specify a custom key-comparison routine. This is used when the Btree
database requires a specific sort that db6.0_codegen cannot generate. A
stub key comparison routine will be created and configured for the
database which should be modified as necessary. See the “key_type”
keyword for more information.
There must be one token on the line: the keyword by itself.
dupsort Configure the database to support sorted duplicates.
There must be one token on the line: the keyword by itself.
extentsize Configure the size of the Queue database extent files.
There must be two tokens on the line: the keyword and the extent file
size, as a number of pages.
key_type Configure a integral type key-comparison routine. This is used when the
Btree database key is an integral type (such as “unsigned int” or
“u_int32_t”). Any C-language integral type may be specified. See the
“custom” keyword for more information. A Btree comparison routine based
on the type of the key will be created and configured.
There must be two tokens on the line: the keyword and the type.
pagesize Configure the database page size.
There must be two tokens on the line: the keyword and the page size in
bytes.
primary Configure the database as a secondary index. A stub secondary callback
routine will be created and configured for the database, which should be
modified as necessary. See the “secondary_offset” keyword for more
information.
There must be two tokens on the line: the keyword and the name of the
primary database for which this database is a secondary.
recnum Configure the Btree database to support record number access.
There must be one token on the line: the keyword by itself.
re_len Configure the record length for a Queue database or a fixed-length Recno
database.
There must be two tokens on the line: the keyword and the length of a
record, in bytes.
secondary_offset Configure a secondary callback routine based on a byte string found in the
primary database's data item.
There must be three tokens on the line: the keyword, the byte offset from
the beginning of the primary data item where the secondary key occurs, and
the length of the secondary key in bytes.
transaction Configure the database (and, by extension, the database environment), to
be transactional.
There must be one token on the line: the keyword by itself.
type Configure the database type.
There must be two tokens on the line: the keyword and the type, where the
type is one of “btree”, “hash”, “queue” or “recno”.
} End the database environment block.
There must be one token on the line: the keyword by itself.
AUTHORS
Thorsten Glaser <tg@debian.org> wrote this manual page for the Debian project (but may be
used by others) after the original HTML format documentation Copyright © 1996,2008 Oracle.
All rights reserved.