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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE section PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<section id="db_val_t" xmlns:xi="http://www.w3.org/2001/XInclude">
<sectioninfo>
<revhistory>
<revision>
<revnumber>$Revision$</revnumber>
<date>$Date$</date>
</revision>
</revhistory>
</sectioninfo>
<title>Type <type>db_val_t</type></title>
<para>
This structure represents a value in the database. Several data-types
are recognized and converted by the database <acronym>API</acronym>:
<itemizedlist>
<listitem>
<para>
<emphasis>DB_INT</emphasis> - Value in the database
represents an integer number.
</para>
</listitem>
<listitem>
<para>
<emphasis>DB_DOUBLE</emphasis> - Value in the database
represents a decimal number.
</para>
</listitem>
<listitem>
<para>
<emphasis>DB_STRING</emphasis> - Value in the database
represents a string.
</para>
</listitem>
<listitem>
<para>
<emphasis>DB_STR</emphasis> - Value in the database
represents a string.
</para>
</listitem>
<listitem>
<para>
<emphasis>DB_DATETIME</emphasis> - Value in the database
represents date and time.
</para>
</listitem>
<listitem>
<para>
<emphasis>DB_BLOB</emphasis> - Value in the database
represents binary large object.
</para>
</listitem>
</itemizedlist>
These data-types are automatically recognized, converted from internal
database representation and stored in a variable of corresponding type.
</para>
<programlisting>
typedef struct db_val {
db_type_t type; /* Type of the value */
int nul; /* NULL flag */
union {
int int_val; /* Integer value */
double double_val; /* Double value */
time_t time_val; /* Unix time_t value */
const char* string_val; /* Zero terminated string */
str str_val; /* str structure */
str blob_val; /* Structure describing blob */
} val;
} db_val_t;
</programlisting>
<note>
<para>
All macros expect pinter to <type>db_val_t</type> variable as a
parameter.
</para>
</note>
<itemizedlist>
<listitem>
<para>
<function>VAL_TYPE(value)</function> Macro.
</para>
<para>
Use this macro if you need to set/get the type of the value
</para>
<example>
<title>VAL_TYPE Macro</title>
<programlisting>
...
VAL_TYPE(val) = DB_INT;
if (VAL_TYPE(val) == DB_FLOAT)
...
</programlisting>
</example>
</listitem>
<listitem>
<para>
<function>VAL_NULL(value)</function> Macro.
</para>
<para>
Use this macro if you need to set/get the null flag. Non-zero
flag means that the corresponding cell in the database
contained no data (NULL value in <acronym>MySQL</acronym>
terminology).
</para>
<example>
<title>VAL_NULL Macro</title>
<programlisting>
...
if (VAL_NULL(val) == 1) {
printf("The cell is NULL");
}
...
</programlisting>
</example>
</listitem>
<listitem>
<para>
<function>VAL_INT(value)</function> Macro.
</para>
<para>
Use this macro if you need to access <type>integer</type> value
in <type>db_val_t</type> structure.
</para>
<example>
<title>VAL_INT Macro</title>
<programlisting>
...
if (VAL_TYPE(val) == DB_INT) {
printf("%d", VAL_INT(val));
}
...
</programlisting>
</example>
</listitem>
<listitem>
<para>
<function>VAL_DOUBLE(value)</function> Macro.
</para>
<para>
Use this macro if you need to access <type>double</type> value
in the <type>db_val_t</type> structure.
</para>
<example>
<title>VAL_DOUBLE Macro</title>
<programlisting>
...
if (VAL_TYPE(val) == DB_DOUBLE) {
printf("%f", VAL_DOUBLE(val));
}
...
</programlisting>
</example>
</listitem>
<listitem>
<para>
<function>VAL_TIME(value)</function> Macro.
</para>
<para>
Use this macro if you need to access <type>time_t</type> value
in <type>db_val_t</type> structure.
</para>
<example>
<title>VAL_TIME Macro</title>
<programlisting>
...
time_t tim;
if (VAL_TYPE(val) == DB_DATETIME) {
tim = VAL_TIME(val);
}
...
</programlisting>
</example>
</listitem>
<listitem>
<para>
<function>VAL_STRING(value)</function> Macro.
</para>
<para>
Use this macro if you need to access <type>string</type> value
in <type>db_val_t</type> structure.
</para>
<example>
<title>VAL_STRING Macro</title>
<programlisting>
...
if (VAL_TYPE(val) == DB_STRING) {
printf("%s", VAL_STRING(val));
}
...
</programlisting>
</example>
</listitem>
<listitem>
<para>
<function>VAL_STR(value)</function> Macro.
</para>
<para>
Use this macro if you need to access <type>str</type> structure
in <type>db_val_t</type> structure.
</para>
<example>
<title>VAL_STR Macro</title>
<programlisting>
...
if (VAL_TYPE(val) == DB_STR) {
printf("%.*s", VAL_STR(val).len, VAL_STR(val).s);
}
...
</programlisting>
</example>
</listitem>
<listitem>
<para>
<function>VAL_BLOB(value)</function> Macro.
</para>
<para>
Use this macro if you need to access <type>blob</type> value in <type>db_val_t</type> structure.
</para>
<example>
<title>VAL_STR Macro</title>
<programlisting>
...
if (VAL_TYPE(val) == DB_BLOB) {
printf("%.*s", VAL_BLOB(val).len, VAL_BLOB(val).s);
}
...
</programlisting>
</example>
</listitem>
</itemizedlist>
</section>
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