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<h1 align="center">Using the GEDCOM parser library</h1>
<br>
<li><a href="#Start_and_end_callbacks">Start and end callbacks</a></li>
<li><a href="#Default_callbacks">Default callbacks</a></li>
+ </ul><li><a href="#C_object_model">C object model</a></li>
+ <ul>
+ <li><a href="#Main_functions">Main functions</a></li>
+ <li><a href="#Object_model_structure">Object model structure</a></li>
+ <li><a href="#User_data">User data</a><br>
+ </li>
</ul>
+
<li><a href="#Other_API_functions">Other API functions</a></li>
<ul>
</ul>
<li><a href="#Converting_character_sets">Converting character sets</a></li>
<li><a href="#Support_for_configure.in">Support for configure.in</a><br>
+<br>
</li>
- <li><a href="interface.html">Interface details</a><br>
+ <li><a href="interface.html">Interface details of the callback parser</a></li><li><a href="gomxref.html">C object model details</a><br>
</li>
+
</ul>
<hr width="100%" size="2">
<h2><a name="Overview"></a>Overview<br>
- </h2>
- The GEDCOM parser library is built as a callback-based parser (comparable
- to the SAX interface of XML). It comes with:<br>
+ </h2> The GEDCOM
+parser library provides two interfaces. At the one hand, it can be
+used as a callback-based parser (comparable to the SAX interface of
+XML); at the other hand, the parser can be used to convert the GEDCOM file
+into an object model (comparable to the DOM interface of XML). It comes
+with:<br>
<ul>
<li>a library (<code>libgedcom.so</code>), to be linked in the
-application program</li>
+application program, which implements the callback parser</li>
<li>a header file (<code>gedcom.h</code>), to be used in the sources
of the application program</li>
<li>a header file (<code>gedcom-tags.h</code>) that is also installed,
- but that is automatically included via <code>gedcom.h</code><br>
- </li>
+ but that is automatically included via <code>gedcom.h</code></li></ul>Additionally, if you want to use the GEDCOM C object model, the following should be used (note that <code>libgedcom.so</code> is also needed in this case, because the object model uses the callback parser internally):<br>
+<ul>
+ <li>a library (<code>libgedcom_gom.so</code>), to be linked in the application program, which implements the C object model</li>
+ <li>a header file (<code>gom.h</code>), to be used in the sources of the application program<br>
+ </li>
+
</ul>
+
Next to these, there is also a data directory in <code>$PREFIX/share/gedcom-parse</code>
that contains some additional stuff, but which is not immediately
important at first. I'll leave the description of the data directory
for later.<br>
<br>
- The very simplest call of the gedcom parser is simply the following
- piece of code (include of the gedcom header is assumed, as everywhere
+ The very simplest call of the gedcom callback parser is simply the following
+ piece of code (include of the <code>gedcom.h</code> header is assumed, as everywhere
in this manual):<br>
<blockquote><code>int result;<br>
is parse the entire file and return the result. The function returns
0 on success and 1 on failure. No other information is available
using this function only.<br>
- <br>
- The call to <code>gedcom_init</code>() should be one of the first calls
+<br>
+Alternatively, programs using the C object model should use the following (in this case, the inclusion of both <code>gedcom.h</code> and <code>gom.h</code> is required):<br>
+
+<blockquote><code>int result;<br>
+ ...<br>
+ <b>gedcom_init</b>();<br>
+ ...<br>
+ result = <b>gom_parse_file</b>("myfamily.ged");<br>
+ </code> </blockquote>
+The call to <code>gom_parse_file</code> will build the C object model, which is then a complete representation of the GEDCOM file.<br>
+<br>
+No matter which of the interfaces you use, the call to <code>gedcom_init</code>() should be one of the first calls
in your program. The requirement is that it should come before the first
call to <code>iconv_open</code> (part of the generic character set conversion
feature) in the program, either by your program itself, or indirectly by
the library calls it makes. Practically, it should e.g. come before
any calls to any GTK functions, because GTK uses <code>iconv_open</code>
- in its initialization. For the same reason it is also advised to put
-the <code>-lgedcom</code> option on the linking of the program as the last
-option, so that its initialization code is run first.<br>
+ in its initialization.<br>
+ <br>
+For the same reason it is also advised to put
+the <code>-lgedcom</code> option
+on the linking of the program as the last option, so that its initialization
+code is run first. In the case of using the C object model, the linking
+options should be: <code>-lgedcom_gom -lgedcom</code><br>
<br>
The next sections will refine this piece of code to be able to have
meaningful errors and the actual data that is in the file.<br>
<hr width="100%" size="2">
-<h2><a name="Error_handling"></a>Error handling</h2>
- Since this is a relatively simple topic, it is discussed before the
- actual callback mechanism, although it also uses a callback...<br>
- <br>
- The library can be used in several different circumstances, both
+<h2><a name="Error_handling"></a>Error handling</h2>The library can be used in several different circumstances, both
terminal-based as GUI-based. Therefore, it leaves the actual display
of the error message up to the application. For this, the application
needs to register a callback before parsing the GEDCOM file, which will
be called by the library on errors, warnings and messages.<br>
<br>
- A typical piece of code would be:<br>
+ A typical piece of code would be (<code>gom_parse_file</code> would be called in case the C object model is used):<br>
<blockquote><code>void <b>my_message_handler</b> (Gedcom_msg_type type,
char *msg)<br>
<hr width="100%" size="2">
<h2><a name="Data_callback_mechanism"></a>Data callback mechanism</h2>
The most important use of the parser is of course to get the data
-out of the GEDCOM file. As already mentioned, the parser uses a callback
- mechanism for that. In fact, the mechanism involves two levels.<br>
+out of the GEDCOM file. This section focuses on the callback mechanism (see the <a href="#C_object_model">next section</a> for the C object model). In fact, the mechanism involves two levels.<br>
<br>
The primary level is that each of the sections in a GEDCOM file is
notified to the application code via a "start element" callback and an
of the "upper" tags has been subscribed upon.<br>
+<hr width="100%" size="2"><br>
+<h2><a name="C_object_model"></a>C object model</h2>
+In the GEDCOM object model, all the data is immediately available after calling <code>gom_parse_file()</code>. For this, an entire model based on C structs is used. These structs are documented <a href="gomxref.html">here</a>,
+and follow the GEDCOM syntax quite closely. Each of the records in
+a GEDCOM file are modelled by a separate struct, and some common sub-structures
+have their own struct definition.<br>
+<br>
+<h3><a name="Main_functions"></a>Main functions<br>
+</h3>
+The following functions are available to get at these structs:<br>
+<ul>
+ <li>First, there are two functions to get the header record and the submission
+record (there can be only one of them in a GEDCOM file):<br>
+ <blockquote><code>struct header* gom_get_header();<br>
+struct submission* gom_get_submission();<br>
+ </code></blockquote>
+ </li>
+ <li>Further, for each of the other records, there are two functions, one
+to get the first of such records, and one to get a record via its cross-reference
+tag in the GEDCOM file:<br>
+ <blockquote><code>struct XXX* gom_get_first_XXX();<br>
+struct XXX* gom_get_XXX_by_xref(char* xref);</code><br>
+ </blockquote>
+ </li>
+</ul>
+<blockquote>The XXX stands for one of the following: <code>family, </code><code>individual, multimedia, note, repository, source, submitter, user_rec</code>.<br>
+</blockquote>
+<h3><a name="Object_model_structure"></a>Object model structure<br>
+</h3>
+All records of a certain type are linked together in a linked list. The
+above functions only give access to the first record of each linked list.
+ The others can be accessed by traversing the linked list via the <code>next</code> member of the structs. This means that e.g. the following piece of code will traverse the linked list of family records:<br>
+<blockquote><code>struct family* fam;<br>
+ <br>
+for (fam = gom_get_first_family() ; fam ; fam = fam->next) {<br>
+ ...<br>
+}</code><br>
+</blockquote>
+The <code>next</code> member of the last element in the list is guaranteed to have the <code>NULL</code> value.<br>
+<br>
+Actually, the linked list is a doubly-linked list: each record also has a <code>previous</code> member. But for implementation reasons the behaviour of this <code>previous</code> member on the edges of the linked list will not be guaranteed, i.e. it can be circular or terminated with <code>NULL</code>, no assumptions can be made in the application code.<br>
+<br>
+This linked-list model applies also to all sub-structures of the main record structs, i.e. each struct that has a <code>next </code>and <code>previous</code>
+member following the above conventions. This means that the following
+piece of code traverses all children of a family (see the details of the
+different structs <a href="gomxref.html">here</a>):<br>
+<blockquote><code>struct family* fam = ...;<br>
+ <br>
+struct xref_list* xrl;<br>
+for (xrl = fam->children ; xrl ; xrl = xrl->next) {<br>
+ ...<br>
+}</code> <br>
+</blockquote>
+Note that all character strings in the object model are encoded in UTF-8 (<a href="file:///home/verthezp/src/external/gedcom-parse/doc/encoding.html">Why UTF-8?</a>).<br>
+<h3><a name="User_data"></a>User data</h3>
+Each of the structs has an extra member called <code>extra</code> (of type <code>struct user_data*</code>).
+ This gathers all non-standard GEDCOM tags within the scope of the struct
+in a flat linked list, no matter what the internal structure of the non-standard
+tags is. Each element of the linked list has:<br>
+<ul>
+ <li>a level: the level number in the GEDCOM file</li>
+ <li>a tag: the tag given in the GEDCOM file</li>
+ <li>a value: the value, which can be a string value or a cross-reference value (one of the two will be non-NULL)<br>
+ </li>
+</ul>
+This way, none of the information in the GEDCOM file is lost, even the non-standard information.<br>
<hr width="100%" size="2">
<h2><a name="Other_API_functions"></a>Other API functions<br>
</h2>
- Although the above describes the basic interface of libgedcom, there
+
+ Although the above describes the basic interface of the gedcom parser, there
are some other functions that allow to customize the behaviour of the library.
These will be explained in the current section.<br>
<pre> </pre>
+<br>
<br>
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