Alessandro Bonazzi 5c7aa8c1c0 Patch level : 12.0 no-patch
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Aggiunta documentazione di sqlite 3
2020-11-29 00:32:36 +01:00

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<title>Obtain Values For URI Parameters</title>
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<a href="intro.html"><h2>SQLite C Interface</h2></a>
<h2>Obtain Values For URI Parameters</h2>
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<blockquote><pre>
const char *sqlite3_uri_parameter(const char *zFilename, const char *zParam);
int sqlite3_uri_boolean(const char *zFile, const char *zParam, int bDefault);
sqlite3_int64 sqlite3_uri_int64(const char*, const char*, sqlite3_int64);
const char *sqlite3_uri_key(const char *zFilename, int N);
</pre></blockquote>
<p>
These are utility routines, useful to <a href="../vfs.html">custom VFS implementations</a>,
that check if a database file was a URI that contained a specific query
parameter, and if so obtains the value of that query parameter.</p>
<p>The first parameter to these interfaces (hereafter referred to
as F) must be one of:
<ul>
<li> A database filename pointer created by the SQLite core and
passed into the xOpen() method of a VFS implemention, or
<li> A filename obtained from <a href="../c3ref/db_filename.html">sqlite3_db_filename()</a>, or
<li> A new filename constructed using <a href="../c3ref/create_filename.html">sqlite3_create_filename()</a>.
</ul>
If the F parameter is not one of the above, then the behavior is
undefined and probably undesirable. Older versions of SQLite were
more tolerant of invalid F parameters than newer versions.</p>
<p>If F is a suitable filename (as described in the previous paragraph)
and if P is the name of the query parameter, then
sqlite3_uri_parameter(F,P) returns the value of the P
parameter if it exists or a NULL pointer if P does not appear as a
query parameter on F. If P is a query parameter of F and it
has no explicit value, then sqlite3_uri_parameter(F,P) returns
a pointer to an empty string.</p>
<p>The sqlite3_uri_boolean(F,P,B) routine assumes that P is a boolean
parameter and returns true (1) or false (0) according to the value
of P. The sqlite3_uri_boolean(F,P,B) routine returns true (1) if the
value of query parameter P is one of "yes", "true", or "on" in any
case or if the value begins with a non-zero number. The
sqlite3_uri_boolean(F,P,B) routines returns false (0) if the value of
query parameter P is one of "no", "false", or "off" in any case or
if the value begins with a numeric zero. If P is not a query
parameter on F or if the value of P does not match any of the
above, then sqlite3_uri_boolean(F,P,B) returns (B!=0).</p>
<p>The sqlite3_uri_int64(F,P,D) routine converts the value of P into a
64-bit signed integer and returns that integer, or D if P does not
exist. If the value of P is something other than an integer, then
zero is returned.</p>
<p>The sqlite3_uri_key(F,N) returns a pointer to the name (not
the value) of the N-th query parameter for filename F, or a NULL
pointer if N is less than zero or greater than the number of query
parameters minus 1. The N value is zero-based so N should be 0 to obtain
the name of the first query parameter, 1 for the second parameter, and
so forth.</p>
<p>If F is a NULL pointer, then sqlite3_uri_parameter(F,P) returns NULL and
sqlite3_uri_boolean(F,P,B) returns B. If F is not a NULL pointer and
is not a database file pathname pointer that the SQLite core passed
into the xOpen VFS method, then the behavior of this routine is undefined
and probably undesirable.</p>
<p>Beginning with SQLite <a href="../releaselog/3_31_0.html">version 3.31.0</a> (2020-01-22) the input F
parameter can also be the name of a rollback journal file or WAL file
in addition to the main database file. Prior to version 3.31.0, these
routines would only work if F was the name of the main database file.
When the F parameter is the name of the rollback journal or WAL file,
it has access to all the same query parameters as were found on the
main database file.</p>
<p>See the <a href="../uri.html">URI filename</a> documentation for additional information.
</p><p>See also lists of
<a href="objlist.html">Objects</a>,
<a href="constlist.html">Constants</a>, and
<a href="funclist.html">Functions</a>.</p>