db_cxx.so

berkeley db 4.6.21的源码。berkeley db是一个简单的数据库管理系统

m4_comment([$Id: db_cxx.so,v 11.9 2000/03/22 22:02:14 bostic Exp $])

m4_ref_title(Upgrading m4_db Applications,
    Release 3.0: the Db class for C++ and Java,,
    upgrade.3.0/dbenv_cxx, upgrade.3.0/cxx)

m4_p([dnl
The static Db::open method and the DbInfo class have been removed in the
m4_db 3.0 release.  The way to open a database file is to use the new Db
constructor with two arguments, followed by set_XXX methods to configure
the Db object, and finally a call to the new (nonstatic) Db::open().  In
comparing the m4_db 3.0 release open method with the 2.X static open
method, the second argument is new.  It is a database name, which can
be null.  The DbEnv argument has been removed, as the environment is now
specified in the constructor.  The open method no longer returns a Db,
since it operates on one.])

m4_p([dnl
Here's a C++ example opening a m4_db database using the 2.X interface:])

m4_indent([dnl
// Note: by default, errors are thrown as exceptions
Db *table;
Db::open("lookup.db", DB_BTREE, DB_CREATE, 0644, dbenv, 0, &table);])

m4_p([dnl
In the m4_db 3.0 release, this code would be written as:])

m4_indent([dnl
// Note: by default, errors are thrown as exceptions
Db *table = new Db(dbenv, 0);
table-__GT__open("lookup.db", NULL, DB_BTREE, DB_CREATE, 0644);])

m4_p([dnl
Here's a Java example opening a m4_db database using the 2.X interface:])

m4_indent([dnl
// Note: errors are thrown as exceptions
Db table = Db.open("lookup.db", Db.DB_BTREE, Db.DB_CREATE, 0644, dbenv, 0);])

m4_p([dnl
In the m4_db 3.0 release, this code would be written as:])

m4_indent([dnl
// Note: errors are thrown as exceptions
Db table = new Db(dbenv, 0);
table.open("lookup.db", null, Db.DB_BTREE, Db.DB_CREATE, 0644);])

m4_p([dnl
Note that if the dbenv argument is  null, the database will not exist
within an environment.])

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