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diff --git a/docs/programmer_reference/am_misc_struct.html b/docs/programmer_reference/am_misc_struct.html index 25128a75..77d135c5 100644 --- a/docs/programmer_reference/am_misc_struct.html +++ b/docs/programmer_reference/am_misc_struct.html @@ -14,17 +14,16 @@ <body> <div xmlns="" class="navheader"> <div class="libver"> - <p>Library Version 11.2.5.3</p> + <p>Library Version 12.1.6.1</p> </div> <table width="100%" summary="Navigation header"> <tr> - <th colspan="3" align="center">Storing C/C++ structures/objects</th> + <th colspan="3" align="center">Storing C/C++ + structures/objects</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="am_misc_partial.html">Prev</a> </td> - <th width="60%" align="center">Chapter 4. - Access Method Wrapup - </th> + <th width="60%" align="center">Chapter 4. Access Method Wrapup </th> <td width="20%" align="right"> <a accesskey="n" href="am_misc_perm.html">Next</a></td> </tr> </table> @@ -34,16 +33,23 @@ <div class="titlepage"> <div> <div> - <h2 class="title" style="clear: both"><a id="am_misc_struct"></a>Storing C/C++ structures/objects</h2> + <h2 class="title" style="clear: both"><a id="am_misc_struct"></a>Storing C/C++ + structures/objects</h2> </div> </div> </div> - <p>Berkeley DB can store any kind of data, that is, it is entirely 8-bit clean. -How you use this depends, to some extent, on the application language -you are using. In the C/C++ languages, there are a couple of different -ways to store structures and objects.</p> - <p>First, you can do some form of run-length encoding and copy your -structure into another piece of memory before storing it:</p> + <p> + Berkeley DB can store any kind of data, that is, it is + entirely 8-bit clean. How you use this depends, to some + extent, on the application language you are using. In the + C/C++ languages, there are a couple of different ways to store + structures and objects. + </p> + <p> + First, you can do some form of run-length encoding and copy + your structure into another piece of memory before storing + it: + </p> <a id="prog_am23"></a> <pre class="programlisting">struct { char *data1; @@ -63,11 +69,15 @@ memcpy(p, &info.data2, sizeof(info.data2)); p += sizeof(info.data2); ... </pre> - <p>and so on, until all the fields of the structure have been loaded into -the byte array. If you want more examples, see the Berkeley DB logging -routines (for example, btree/btree_auto.c:__bam_split_log()). This -technique is generally known as "marshalling". If you use this -technique, you must then un-marshall the data when you read it back:</p> + <p> + and so on, until all the fields of the structure have been + loaded into the byte array. If you want more examples, see the + Berkeley DB logging routines (for example, + btree/btree_auto.c:__bam_split_log()). This technique is + generally known as "marshalling". If you use this technique, + you must then un-marshall the data when you read it + back: + </p> <a id="prog_am24"></a> <pre class="programlisting">struct { char *data1; @@ -87,27 +97,41 @@ memcpy(&info.data2, p, sizeof(info.data2)); p += sizeof(info.data2); ... </pre> - <p>and so on.</p> - <p>The second way to solve this problem only works if you have just one -variable length field in the structure. In that case, you can declare -the structure as follows:</p> + <p> + and so on. + </p> + <p> + The second way to solve this problem only works if you have + just one variable length field in the structure. In that case, + you can declare the structure as follows: + </p> <pre class="programlisting">struct { int a, b, c; u_int8_t buf[1]; } info;</pre> - <p>Then, let's say you have a string you want to store in this structure. -When you allocate the structure, you allocate it as:</p> + <p> + Then, let's say you have a string you want to store in this + structure. When you allocate the structure, you allocate it + as: + </p> <pre class="programlisting">malloc(sizeof(struct info) + strlen(string));</pre> - <p>Since the allocated memory is contiguous, you can the initialize the -structure as:</p> + <p> + Since the allocated memory is contiguous, you can the + initialize the structure as: + </p> <pre class="programlisting">info.a = 1; info.b = 2; info.c = 3; memcpy(&info.buf[0], string, strlen(string) + 1);</pre> - <p>and give it to Berkeley DB to store, with a length of:</p> + <p> + and give it to Berkeley DB to store, with a length + of: + </p> <pre class="programlisting">sizeof(struct info) + strlen(string);</pre> - <p>In this case, the structure can be copied out of the database and used -without any additional work.</p> + <p> + In this case, the structure can be copied out of the + database and used without any additional work. + </p> </div> <div class="navfooter"> <hr /> @@ -120,7 +144,8 @@ without any additional work.</p> <td width="40%" align="right"> <a accesskey="n" href="am_misc_perm.html">Next</a></td> </tr> <tr> - <td width="40%" align="left" valign="top">Partial record storage and retrieval </td> + <td width="40%" align="left" valign="top">Partial record storage and + retrieval </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> |