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<th colspan="3" align="center">Chapter 25.
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<h2 class="title"><a id="DbstlDbt"></a>Chapter 25.
DbstlDbt </h2>
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<p>You can persist all bytes in a chunk of contiguous memory by constructing an <a class="link" href="DbstlDbt.html" title="Chapter 25. DbstlDbt">DbstlDbt</a>
object A(use malloc to allocate the required number of bytes for A.data and copy the bytes to be stored into A.data, set other fields as necessary) and store A into a container, e.g. </p>
<p>db_vector<DbstlDbt>, this stores the bytes rather than the object A into the underlying database. The <a class="link" href="DbstlDbt.html" title="Chapter 25. DbstlDbt">DbstlDbt</a>
class can help you avoid memory leaks, so it is strongly recommended that you use <a class="link" href="DbstlDbt.html" title="Chapter 25. DbstlDbt">DbstlDbt</a>
rather than Dbt class.</p>
<p><a class="link" href="DbstlDbt.html" title="Chapter 25. DbstlDbt">DbstlDbt</a>
derives from Dbt class, and it does an deep copy on copy construction and assignment --by calling malloc to allocate its own memory and then copying the bytes to it; Conversely the destructor will free the memory on destruction if the data pointer is non-NULL. The destructor assumes the memory is allocated via malloc, hence why you are required to call malloc to allocate memory in order to use <a class="link" href="DbstlDbt.html" title="Chapter 25. DbstlDbt">DbstlDbt</a>
.</p>
<p><a class="link" href="DbstlDbt.html" title="Chapter 25. DbstlDbt">DbstlDbt</a>
simply inherits all methods from Dbt with no extra new methods except the constructors/destructor and assignment operator, so it is easy to use.</p>
<p>In practice you rarely need to use <a class="link" href="DbstlDbt.html" title="Chapter 25. DbstlDbt">DbstlDbt</a>
or Dbt because dbstl enables you to store any complex objects or primitive data. Only when you need to store raw bytes, e.g. a bitmap, do you need to use <a class="link" href="DbstlDbt.html" title="Chapter 25. DbstlDbt">DbstlDbt</a>
.</p>
<p>Hence, <a class="link" href="DbstlDbt.html" title="Chapter 25. DbstlDbt">DbstlDbt</a>
is the right class to use to store any object into Berkeley DB via dbstl without memory leaks.</p>
<p>Don't free the memory referenced by <a class="link" href="DbstlDbt.html" title="Chapter 25. DbstlDbt">DbstlDbt</a>
objects, it will be freed when the <a class="link" href="DbstlDbt.html" title="Chapter 25. DbstlDbt">DbstlDbt</a>
object is destructed.</p>
<p>Please refer to the two examples using <a class="link" href="DbstlDbt.html" title="Chapter 25. DbstlDbt">DbstlDbt</a>
in TestAssoc::test_arbitrary_object_storage and TestAssoc::test_char_star_string_storage member functions, which illustrate how to correctly use <a class="link" href="DbstlDbt.html" title="Chapter 25. DbstlDbt">DbstlDbt</a>
in order to store raw bytes.</p>
<p>This class handles the task of allocating and de-allocating memory internally. Although it can be used to store data which cannot be handled by the <a class="link" href="DbstlElemTraits.html" title="Chapter 26. DbstlElemTraits">DbstlElemTraits</a>
class, in practice, it is usually more convenient to register callbacks in the <a class="link" href="DbstlElemTraits.html" title="Chapter 26. DbstlElemTraits">DbstlElemTraits</a>
class for the type you are storing/retrieving using dbstl. </p>
<h4><a id="id1570745"></a> Public Members </h4>
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<a class="xref" href="DbstlDbt.html#stlDbstlDbtDbstlDbt" title="DbstlDbt">
DbstlDbt
</a>
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<td>
<p>Construct an object with an existing chunk of memory of size1 bytes, refered by data1,. </p> </td>
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<a class="xref" href="stlDbstlDbtdstr_DbstlDbt.html" title="~DbstlDbt">
~DbstlDbt
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<p>The memory will be free'ed by the destructor. </p> </td>
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<a class="xref" href="stlDbstlDbtoperator_assign.html" title="operator=">
operator=
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<p>The memory will be reallocated if neccessary. </p> </td>
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<h4><a id="id1570961"></a>
Group</h4>
<p>
<a class="xref" href="dbstl_helper_classes.html" title="Chapter 21. Dbstl Helper Classes">
Dbstl Helper Classes </a>
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<p>
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<div class="sect1" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h2 class="title" style="clear: both"><a id="stlDbstlDbtDbstlDbt"></a>
DbstlDbt
</h2>
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<div class="sect2" lang="en" xml:lang="en">
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<h3 class="title"><a id="func_details"></a>
Function Details</h3>
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<pre class="programlisting">
DbstlDbt(void *data1,
u_int32_t size1)
</pre>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage"></div>
<p>Construct an object with an existing chunk of memory of size1 bytes, refered by data1,. </p>
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<pre class="programlisting">
DbstlDbt()
</pre>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage"></div>
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<pre class="programlisting">
DbstlDbt(const DbstlDbt &d)
</pre>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage"></div>
<p>This copy constructor does a deep copy. </p>
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<h3 class="title"><a id="id1570948"></a>
Class</h3>
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<a class="link" href="DbstlDbt.html" title="Chapter 25. DbstlDbt">
DbstlDbt</a>
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