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<! "@(#)apis.so 10.14 (Sleepycat) 12/16/98">
<!Copyright 1997, 1998 by Sleepycat Software, Inc. All rights reserved.>
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<head>
<title>Berkeley DB Reference Guide: Architecture</title>
<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
<meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btr
ee,hash,hashing,transaction,transactions,locking,logging,access method,access me
thods,java,C,C++">
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<h3>Berkeley DB Reference Guide: Architecture</h3>
<p>
<h1 align=center>Available APIs</h1>
<h1>C</h1>
The Berkeley DB library is written entirely in ANSI C. C applications use a
single include file, #include <db.h>.
<h1>C++</h1>
The C++ classes provide a thin wrapper around the C API, with the major
advantages being improved encapsulation and an optional exception
mechanism for errors. C++ applications use a single include file,
#include <db_cxx.h>.
<p> The classes and methods are named in a fashion that directly
corresponds to structures and functions in the C interface. Likewise,
arguments to methods appear in the same order as the C interface, except
to remove the explicit <b>this</b> pointer. The #defines used for flags
are identical between the C and C++ interfaces.
<p>
As a rule, each C++ object has exactly one structure from the underlying C
API associated with it.
The C structure is allocated with each constructor call and deallocated
with each destructor call.
Thus, the rules the user needs to follow in allocating and deallocating
structures are the same between the C and C++ interfaces.
<p>
To ensure portability to many platforms, both new and old, we make few
assumptions about the C++ compiler and library.
For example, we do not expect STL, templates or namespaces to be available.
The newest C++ feature used is exceptions, which are used liberally to
transmit error information.
Even the use of exceptions can be disabled at runtime, by using
set_error_model.
<h1>JAVA</h1>
The Java classes provide a layer around the C API that is almost
identical to the C++ layer.
The classes and methods are, for the most part identical to the C++
layer. Db constants and #defines are represented as "static final int"
values. Errors conditions appear as Java exceptions.
<p>
As in C++, each Java object has exactly one structure from the underlying C
API associated with it. The Java structure is allocated with each constructor
or open call, but is deallocated only when the Java garbage collector does so.
Because the timing or ordering of garbage collection is not predictable,
the user should take
care to do a <b>close</b> when finished with any object that has such a
method.
<p>
<h1>Dbm/Ndbm, Hsearch</h1>
Berkeley DB supports the standard UNIX interfaces <a href="../../api_c/historic/dbm.html">dbm/ndbm</a> and
<a href="../../api_c/historic/hsearch.html">hsearch</a>.
After including a new header file and recompiling, <a href="../../api_c/historic/dbm.html">dbm/ndbm</a>
programs will run orders of magnitude faster and their underlying
databases can grow as large as you like (historic <a href="../../api_c/historic/dbm.html">dbm/ndbm</a>
applications will fail when some number of entries are inserted into
the database, where the number depends on the effectiveness of the
hashing function on the particular data set).
<p>
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