<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><title>Using the GEDCOM parser library</title>
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<h1 align="center">Using the GEDCOM parser library</h1>
<br>
<li><a href="#Error_treatment">Error treatment</a></li>
<li><a href="#Compatibility_mode">Compatibility mode</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>
+ </li>
+
+
<li><a href="interface.html">Interface details</a><br>
</li>
result = <b>gedcom_parse_file</b>("myfamily.ged");</code><br>
</blockquote>
In the above piece of code, <code>my_message_handler</code> is the callback
- that will be called for errors (<code>type=ERROR</code>), warnings (<code>
- type=WARNING</code>) and messages (<code>type=MESSAGE</code>). The
+ that will be called for errors (<code>type=ERROR</code>), warnings (<code>type=WARNING</code>) and messages (<code>type=MESSAGE</code>). The
callback must have the signature as in the example. For errors, the
<code> msg</code> passed to the callback will have the format:<br>
<blockquote><code>Error on line</code> <i><lineno></i>: <i><actual_message></i><br>
</blockquote>
Note that the entire string will be properly internationalized, and
-encoded in UTF-8 (see "Why UTF-8?" <i>LINK TBD</i>). Also,
+encoded in UTF-8 (<a href="encoding.html">Why UTF-8?</a>). Also,
no newline is appended, so that the application program can use it in any
way it wants. Warnings are similar, but use "Warning" instead of
"Error". Messages are plain text, without any prefix.<br>
<br>
void <b>my_header_end_cb</b> (Gedcom_ctxt self)<br>
{<br>
- printf("The header ends, context is %d\n", self); /* context
+ printf("The header ends, context is %d\n", (int)self); /* context
will print as "1" */<br>
}<br>
<br>
gedcom.h</code> (so no need to include <code>gedcom-tags.h</code> yourself).<br>
<br>
The example passes a simple integer as context, but an application could
- e.g. pass a <code>struct</code> that will contain the information for the
+ e.g. pass a <code>struct</code> (or an object in a C++ application) that will contain the information for the
header. In the end callback, the application could then e.g. do some
finalizing operations on the <code>struct</code> to put it in its database.<br>
<br>
</blockquote>
The subscription mechanism for elements is similar, only the signatures
of the callbacks differ. The signature for the start callback shows
- that the context of the parent line (e.g. the <code>struct</code> that
+ that the context of the parent line (here e.g. the <code>struct</code> that
describes the header) is passed to this start callback. The callback
-itself returns here the same context, but this can be its own context object
+itself returns here in this example the same context, but this can be its own context object
of course. The end callback is called with both the context of the
-parent and the context of itself, which will be the same in the example.
+parent and the context of itself, which in this example will be the same.
Again, the list of identifiers to use as a first argument for the
subscription function are detailed in the <a href="interface.html#Element_identifiers">
interface details</a> .<br>
raw value is just the raw string that occurs as value on the line next to
the tag (in UTF-8 encoding). The parsed value is the meaningful value
that is parsed from that raw string. The parsed tag is described in
- the section for record callbacks.<br>
+ the section for record callbacks above.<br>
<br>
The <code>Gedcom_val</code> type is meant to be an opaque type. The
only thing that needs to be known about it is that it can contain specific
<ul>
<li>The <code>Gedcom_val</code> argument of the end callback
is currently not used. It is there for future enhancements.</li>
- <li>There is also a <code>Gedcom_val</code> argument in
-the start callback for records. This argument is currently a string
-value giving the pointer in string form.</li>
+ <li>There are also two <code>Gedcom_val</code> arguments in
+the start callback for records. The first one (<code>xref</code>) contains the <code>xref_value</code> corresponding to the cross-reference (or <code>NULL</code> if there isn't one), the second one (<code>parsed_value</code>) contains the value that is parsed from the <code>raw_value</code>. See the <a href="interface.html#Record_identifiers">interface details</a>.</li>
</ul>
in various contexts. For simplicity, the example above doesn't take
this into account (the <code>parent</code> could be of different
types, depending on the context).<br>
+ <br>
+Note also that the default callback is not called when the parent context is <code>NULL</code><code></code>. This is e.g. the case if none of the "upper" tags has been subscribed upon.<br>
<hr width="100%" size="2">
</ul>
Note that, currently, no actual compatibility code is present, but this
is on the to-do list.<br>
+ <hr width="100%" size="2">
+ <h2><a name="Converting_character_sets"></a>Converting character sets</h2>
+All strings passed by the GEDCOM parser to the application are in UTF-8 encoding.
+ Typically, an application needs to convert this to something else to
+be able to display it.<br>
+ <br>
+The most common case is that the output character set is controlled by the <code>locale</code> mechanism (i.e. via the <code>LANG</code>, <code>LC_ALL</code> or <code>LC_CTYPE</code> environment variables), which also controls the <code>gettext</code>
+ mechanism in the application. <br>
+ <br>
+ <br>
+
+
- <hr width="100%" size="2">
+ The source distribution of <code>gedcom-parse</code> contains an example implementation (<code>utf8-locale.c</code> and <code>utf8-locale.h</code>
+ in the top directory). Feel free to use it in
+your source code (it is not part of the library, and it isn't installed anywhere,
+so you need to take over the source and header file in your application).
+ <br>
+ <br>
+
+Its interface is:<br>
+ <blockquote><pre><code>char *<b>convert_utf8_to_locale</b> (char *input, int *conv_failures);<br>char *<b>convert_locale_to_utf8</b> (char *input);<br></code></pre></blockquote>
+
+Both functions return a pointer to a static buffer that is overwritten on
+each call. To function properly, the application must first set the
+locale using the <code>setlocale</code> function (the second step detailed below).
+ All other steps given below, including setting up and closing down the conversion
+handles, are transparantly handled by the two functions. <br>
+ <br>
+If you pass a pointer to an integer to the first function, it will be set
+to the number of conversion failures, i.e. characters that couldn't be converted;
+you can also just pass <code>NULL</code> if you are not interested (note that usually, the interesting information is just whether there <i>were</i>
+ conversion failures or not, which is then given by the integer being bigger
+than zero or not). The second function doesn't need this, because any
+locale can be converted to UTF-8.<br>
+ <br>
+
+You can change the "?" that is output for characters that can't be converted
+to any string you want, using the following function before the conversion
+calls:<br>
+ <blockquote><pre><code>void <b>convert_set_unknown</b> (const char *unknown);</code></pre></blockquote>
+ <br>
+If you want to have your own functions for it instead of this example implementation, the following steps need to
+be taken by the application (more detailed info can be found in the info
+file of the GNU libc library in the "Generic Charset Conversion" section
+under "Character Set Handling" or online <a href="http://www.gnu.org/manual/glibc-2.2.3/html_chapter/libc_6.html#SEC99">here</a>):<br>
+ <ul>
+ <li>inclusion of some headers:</li>
+ </ul>
+ <blockquote>
+ <blockquote>
+ <pre><code>#include <locale.h> /* for setlocale */<br>#include <langinfo.h> /* for nl_langinfo */<br>#include <iconv.h> /* for iconv_* functions */<br></code></pre>
+ </blockquote>
+ </blockquote>
+ <ul>
+ <li>set the program's current locale to what the user configured in the environment:</li>
+ </ul>
+ <blockquote>
+ <blockquote>
+ <pre><code>setlocale(LC_ALL, "");</code><br></pre>
+ </blockquote>
+ </blockquote>
+ <ul>
+ <li>open a conversion handle for conversion from UTF-8 to the character set of the current locale (once for the entire program):</li>
+ </ul>
+ <blockquote>
+ <blockquote>
+ <pre><code>iconv_t iconv_handle;<br>...<br>iconv_handle = iconv_open(nl_langinfo(CODESET), "UTF-8");</code><br>if (iconv_handle == (iconv_t) -1)<br> /* signal an error */<br></pre>
+ </blockquote>
+ </blockquote>
+ <ul>
+ <li>then, every string can be converted using the following:</li>
+ </ul>
+ <blockquote>
+ <blockquote>
+ <pre><code>/* char* in_buf is the input buffer, size_t in_len is its length */<br>/* char* out_buf is the output buffer, size_t out_len is its length */<br><br>size_t nconv;<br>char *in_ptr = in_buf;<br>char *out_ptr = out_buf;<br>nconv = iconv(iconv_handle, &in_ptr, &in_len, &out_ptr, &out_len);</code></pre>
+ </blockquote>
+ </blockquote>
+ <blockquote>If the output buffer is not big enough, <code>iconv</code> will return -1 and set <code>errno</code> to <code>E2BIG</code>. Also, the <code>in_ptr</code> and <code>out_ptr</code> will point just after the last successfully converted character in the respective buffers, and the <code>in_len</code> and <code>out_len</code> will be updated to show the remaining lengths. There can be two strategies here:<br>
+ <ul>
+ <li>Make sure from the beginning
+that the output buffer is big enough. However, it's difficult to find
+an absolute maximum length in advance, even given the length of the input
+string.<br>
+ <br>
+ </li>
+ <li>Do the conversion in several steps, growing the output buffer each time to make more space, and calling <code>iconv</code>
+ consecutively until the conversion is complete. This is the preferred
+way (a function could be written to encapsulate all this).</li>
+ </ul>
+Another error case is when the conversion was unsuccessful (if one of the
+characters can't be represented in the target character set). The <code>iconv</code> function will then also return -1 and set <code>errno</code> to <code>EILSEQ</code>; the <code>in_ptr</code> will point to the character that couldn't be converted. In that case, again two strategies are possible:<br>
+ <ul>
+ <li>Just fail the conversion, and show an error. This is not very user friendly, of course.<br>
+ <br>
+ </li>
+ <li>Skip over the character that can't be converted and append a "?" to the output buffer, then call <code>iconv</code> again. Skipping over a UTF-8 character is fairly simple, as follows from the <a href="http://www.cl.cam.ac.uk/%7Emgk25/unicode.html#utf-8">encoding rules</a>:</li>
+ </ul>
+ <ol>
+ <ol>
+ <li>if the first byte is in binary 0xxxxxxx, then the character is only one byte long, just skip over that byte<br>
+ <br>
+ </li>
+ <li>if the first byte is in binary 11xxxxxx, then skip over that byte and all bytes 10xxxxxx that follow.<br>
+ </li>
+ </ol>
+ </ol>
+ </blockquote>
+ <ul>
+ <li>eventually, the conversion handle needs to be closed (when the program exits):<br>
+ </li>
+ </ul>
+ <blockquote>
+ <blockquote>
+ <pre><code>iconv_close(iconv_handle);<br></code></pre>
+ </blockquote>
+ </blockquote>
+ The example implementation
+mentioned above grows the output buffer dynamically and outputs "?" for characters
+that can't be converted.<br>
+
+ <hr width="100%" size="2">
+ <h2><a name="Support_for_configure.in"></a>Support for configure.in</h2>
+Programs using the GEDCOM parser library and using autoconf to configure
+their sources can use the following statements in configure.in (the example
+is checking for gedcom-parse, version 1.34):<br>
+ <blockquote><code>AC_CHECK_LIB(gedcom, gedcom_parse_file,,<br>
+ AC_MSG_ERROR(Cannot find libgedcom: Please install gedcom-parse))<br>
+AC_MSG_CHECKING(for libgedcom version)<br>
+AC_TRY_RUN([<br>
+#include <stdio.h><br>
+#include <stdlib.h><br>
+#include <gedcom.h><br>
+int<br>
+main()<br>
+{<br>
+if (GEDCOM_PARSE_VERSION >= 1034) exit(0);<br>
+exit(1);<br>
+}],<br>
+ac_gedcom_version_ok='yes',<br>
+ac_gedcom_version_ok='no',<br>
+ac_gedcom_version_ok='no')<br>
+if test "$ac_gedcom_version_ok" = 'yes' ; then<br>
+ AC_MSG_RESULT(ok)<br>
+else<br>
+ AC_MSG_RESULT(not ok)<br>
+ AC_MSG_ERROR(You need at least version 1.34 of gedcom-parse)<br>
+fi</code><br>
+ </blockquote>
+
+There are three preprocessor symbols defined for version checks in the header:<br>
+ <ul>
+ <li><code>GEDCOM_PARSE_VERSION_MAJOR</code></li>
+ <li><code>GEDCOM_PARSE_VERSION_MINOR</code></li>
+ <li><code>GEDCOM_PARSE_VERSION</code><br>
+ </li>
+ </ul>
+The last one is equal to <code>(GEDCOM_PARSE_VERSION_MAJOR * 1000) + GEDCOM_PARSE_VERSION_MINOR.</code><br>
+<hr width="100%" size="2">
<pre><font size="-1">$Id$<br>$Name$</font><br></pre>
projects / gedcom-parse.git / blobdiff