517 lines
20 KiB
Tcl
517 lines
20 KiB
Tcl
|
set rcsid {$Id: capi3.tcl,v 1.10 2007/04/27 17:16:22 drh Exp $}
|
||
|
|
source common.tcl
|
||
|
|
header {C/C++ Interface For SQLite Version 3}
|
||
|
|
|
||
|
|
proc AddHyperlinks {txt} {
|
||
|
|
regsub -all {([^:alnum:>])(sqlite3_\w+)(\([^\)]*\))} $txt \
|
||
|
|
{\1<a href="capi3ref.html#\2">\2</a>\3} t2
|
||
|
|
puts $t2
|
||
|
|
}
|
||
|
|
|
||
|
|
AddHyperlinks {
|
||
|
|
<h2>C/C++ Interface For SQLite Version 3</h2>
|
||
|
|
|
||
|
|
<h3>1.0 Overview</h3>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
SQLite version 3.0 is a new version of SQLite, derived from
|
||
|
|
the SQLite 2.8.13 code base, but with an incompatible file format
|
||
|
|
and API.
|
||
|
|
SQLite version 3.0 was created to answer demand for the following features:
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<ul>
|
||
|
|
<li>Support for UTF-16.</li>
|
||
|
|
<li>User-definable text collating sequences.</li>
|
||
|
|
<li>The ability to store BLOBs in indexed columns.</li>
|
||
|
|
</ul>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
It was necessary to move to version 3.0 to implement these features because
|
||
|
|
each requires incompatible changes to the database file format. Other
|
||
|
|
incompatible changes, such as a cleanup of the API, were introduced at the
|
||
|
|
same time under the theory that it is best to get your incompatible changes
|
||
|
|
out of the way all at once.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The API for version 3.0 is similar to the version 2.X API,
|
||
|
|
but with some important changes. Most noticeably, the "<tt>sqlite_</tt>"
|
||
|
|
prefix that occurs on the beginning of all API functions and data
|
||
|
|
structures are changed to "<tt>sqlite3_</tt>".
|
||
|
|
This avoids confusion between the two APIs and allows linking against both
|
||
|
|
SQLite 2.X and SQLite 3.0 at the same time.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
There is no agreement on what the C datatype for a UTF-16
|
||
|
|
string should be. Therefore, SQLite uses a generic type of void*
|
||
|
|
to refer to UTF-16 strings. Client software can cast the void*
|
||
|
|
to whatever datatype is appropriate for their system.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<h3>2.0 C/C++ Interface</h3>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The API for SQLite 3.0 includes 83 separate functions in addition
|
||
|
|
to several data structures and #defines. (A complete
|
||
|
|
<a href="capi3ref.html">API reference</a> is provided as a separate document.)
|
||
|
|
Fortunately, the interface is not nearly as complex as its size implies.
|
||
|
|
Simple programs can still make do with only 3 functions:
|
||
|
|
<a href="capi3ref.html#sqlite3_open">sqlite3_open()</a>,
|
||
|
|
<a href="capi3ref.html#sqlite3_exec">sqlite3_exec()</a>, and
|
||
|
|
<a href="capi3ref.html#sqlite3_close">sqlite3_close()</a>.
|
||
|
|
More control over the execution of the database engine is provided
|
||
|
|
using
|
||
|
|
<a href="capi3ref.html#sqlite3_prepare">sqlite3_prepare()</a>
|
||
|
|
to compile an SQLite statement into byte code and
|
||
|
|
<a href="capi3ref.html#sqlite3_prepare">sqlite3_step()</a>
|
||
|
|
to execute that bytecode.
|
||
|
|
A family of routines with names beginning with
|
||
|
|
<a href="capi3ref.html#sqlite3_column_blob">sqlite3_column_</a>
|
||
|
|
is used to extract information about the result set of a query.
|
||
|
|
Many interface functions come in pairs, with both a UTF-8 and
|
||
|
|
UTF-16 version. And there is a collection of routines
|
||
|
|
used to implement user-defined SQL functions and user-defined
|
||
|
|
text collating sequences.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
|
||
|
|
<h4>2.1 Opening and closing a database</h4>
|
||
|
|
|
||
|
|
<blockquote><pre>
|
||
|
|
typedef struct sqlite3 sqlite3;
|
||
|
|
int sqlite3_open(const char*, sqlite3**);
|
||
|
|
int sqlite3_open16(const void*, sqlite3**);
|
||
|
|
int sqlite3_close(sqlite3*);
|
||
|
|
const char *sqlite3_errmsg(sqlite3*);
|
||
|
|
const void *sqlite3_errmsg16(sqlite3*);
|
||
|
|
int sqlite3_errcode(sqlite3*);
|
||
|
|
</pre></blockquote>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The sqlite3_open() routine returns an integer error code rather than
|
||
|
|
a pointer to the sqlite3 structure as the version 2 interface did.
|
||
|
|
The difference between sqlite3_open()
|
||
|
|
and sqlite3_open16() is that sqlite3_open16() takes UTF-16 (in host native
|
||
|
|
byte order) for the name of the database file. If a new database file
|
||
|
|
needs to be created, then sqlite3_open16() sets the internal text
|
||
|
|
representation to UTF-16 whereas sqlite3_open() sets the text
|
||
|
|
representation to UTF-8.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The opening and/or creating of the database file is deferred until the
|
||
|
|
file is actually needed. This allows options and parameters, such
|
||
|
|
as the native text representation and default page size, to be
|
||
|
|
set using PRAGMA statements.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The sqlite3_errcode() routine returns a result code for the most
|
||
|
|
recent major API call. sqlite3_errmsg() returns an English-language
|
||
|
|
text error message for the most recent error. The error message is
|
||
|
|
represented in UTF-8 and will be ephemeral - it could disappear on
|
||
|
|
the next call to any SQLite API function. sqlite3_errmsg16() works like
|
||
|
|
sqlite3_errmsg() except that it returns the error message represented
|
||
|
|
as UTF-16 in host native byte order.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The error codes for SQLite version 3 are unchanged from version 2.
|
||
|
|
They are as follows:
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<blockquote><pre>
|
||
|
|
#define SQLITE_OK 0 /* Successful result */
|
||
|
|
#define SQLITE_ERROR 1 /* SQL error or missing database */
|
||
|
|
#define SQLITE_INTERNAL 2 /* An internal logic error in SQLite */
|
||
|
|
#define SQLITE_PERM 3 /* Access permission denied */
|
||
|
|
#define SQLITE_ABORT 4 /* Callback routine requested an abort */
|
||
|
|
#define SQLITE_BUSY 5 /* The database file is locked */
|
||
|
|
#define SQLITE_LOCKED 6 /* A table in the database is locked */
|
||
|
|
#define SQLITE_NOMEM 7 /* A malloc() failed */
|
||
|
|
#define SQLITE_READONLY 8 /* Attempt to write a readonly database */
|
||
|
|
#define SQLITE_INTERRUPT 9 /* Operation terminated by sqlite_interrupt() */
|
||
|
|
#define SQLITE_IOERR 10 /* Some kind of disk I/O error occurred */
|
||
|
|
#define SQLITE_CORRUPT 11 /* The database disk image is malformed */
|
||
|
|
#define SQLITE_NOTFOUND 12 /* (Internal Only) Table or record not found */
|
||
|
|
#define SQLITE_FULL 13 /* Insertion failed because database is full */
|
||
|
|
#define SQLITE_CANTOPEN 14 /* Unable to open the database file */
|
||
|
|
#define SQLITE_PROTOCOL 15 /* Database lock protocol error */
|
||
|
|
#define SQLITE_EMPTY 16 /* (Internal Only) Database table is empty */
|
||
|
|
#define SQLITE_SCHEMA 17 /* The database schema changed */
|
||
|
|
#define SQLITE_TOOBIG 18 /* Too much data for one row of a table */
|
||
|
|
#define SQLITE_CONSTRAINT 19 /* Abort due to contraint violation */
|
||
|
|
#define SQLITE_MISMATCH 20 /* Data type mismatch */
|
||
|
|
#define SQLITE_MISUSE 21 /* Library used incorrectly */
|
||
|
|
#define SQLITE_NOLFS 22 /* Uses OS features not supported on host */
|
||
|
|
#define SQLITE_AUTH 23 /* Authorization denied */
|
||
|
|
#define SQLITE_ROW 100 /* sqlite_step() has another row ready */
|
||
|
|
#define SQLITE_DONE 101 /* sqlite_step() has finished executing */
|
||
|
|
</pre></blockquote>
|
||
|
|
|
||
|
|
<h4>2.2 Executing SQL statements</h4>
|
||
|
|
|
||
|
|
<blockquote><pre>
|
||
|
|
typedef int (*sqlite_callback)(void*,int,char**, char**);
|
||
|
|
int sqlite3_exec(sqlite3*, const char *sql, sqlite_callback, void*, char**);
|
||
|
|
</pre></blockquote>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The sqlite3_exec function works much as it did in SQLite version 2.
|
||
|
|
Zero or more SQL statements specified in the second parameter are compiled
|
||
|
|
and executed. Query results are returned to a callback routine.
|
||
|
|
See the <a href="capi3ref.html#sqlite3_exec">API reference</a> for additional
|
||
|
|
information.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
In SQLite version 3, the sqlite3_exec routine is just a wrapper around
|
||
|
|
calls to the prepared statement interface.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<blockquote><pre>
|
||
|
|
typedef struct sqlite3_stmt sqlite3_stmt;
|
||
|
|
int sqlite3_prepare(sqlite3*, const char*, int, sqlite3_stmt**, const char**);
|
||
|
|
int sqlite3_prepare16(sqlite3*, const void*, int, sqlite3_stmt**, const void**);
|
||
|
|
int sqlite3_finalize(sqlite3_stmt*);
|
||
|
|
int sqlite3_reset(sqlite3_stmt*);
|
||
|
|
</pre></blockquote>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The sqlite3_prepare interface compiles a single SQL statement into byte code
|
||
|
|
for later execution. This interface is now the preferred way of accessing
|
||
|
|
the database.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The SQL statement is a UTF-8 string for sqlite3_prepare().
|
||
|
|
The sqlite3_prepare16() works the same way except
|
||
|
|
that it expects a UTF-16 string as SQL input.
|
||
|
|
Only the first SQL statement in the input string is compiled.
|
||
|
|
The fourth parameter is filled in with a pointer to the next (uncompiled)
|
||
|
|
SQLite statement in the input string, if any.
|
||
|
|
The sqlite3_finalize() routine deallocates a prepared SQL statement.
|
||
|
|
All prepared statements must be finalized before the database can be
|
||
|
|
closed.
|
||
|
|
The sqlite3_reset() routine resets a prepared SQL statement so that it
|
||
|
|
can be executed again.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The SQL statement may contain tokens of the form "?" or "?nnn" or ":aaa"
|
||
|
|
where "nnn" is an integer and "aaa" is an identifier.
|
||
|
|
Such tokens represent unspecified literal values (or "wildcards")
|
||
|
|
to be filled in later by the
|
||
|
|
<a href="capi3ref.html#sqlite3_bind_blob">sqlite3_bind</a> interface.
|
||
|
|
Each wildcard has an associated number which is its sequence in the
|
||
|
|
statement or the "nnn" in the case of a "?nnn" form.
|
||
|
|
It is allowed for the same wildcard
|
||
|
|
to occur more than once in the same SQL statement, in which case
|
||
|
|
all instance of that wildcard will be filled in with the same value.
|
||
|
|
Unbound wildcards have a value of NULL.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<blockquote><pre>
|
||
|
|
int sqlite3_bind_blob(sqlite3_stmt*, int, const void*, int n, void(*)(void*));
|
||
|
|
int sqlite3_bind_double(sqlite3_stmt*, int, double);
|
||
|
|
int sqlite3_bind_int(sqlite3_stmt*, int, int);
|
||
|
|
int sqlite3_bind_int64(sqlite3_stmt*, int, long long int);
|
||
|
|
int sqlite3_bind_null(sqlite3_stmt*, int);
|
||
|
|
int sqlite3_bind_text(sqlite3_stmt*, int, const char*, int n, void(*)(void*));
|
||
|
|
int sqlite3_bind_text16(sqlite3_stmt*, int, const void*, int n, void(*)(void*));
|
||
|
|
int sqlite3_bind_value(sqlite3_stmt*, int, const sqlite3_value*);
|
||
|
|
</pre></blockquote>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
There is an assortment of sqlite3_bind routines used to assign values
|
||
|
|
to wildcards in a prepared SQL statement. Unbound wildcards
|
||
|
|
are interpreted as NULLs. Bindings are not reset by sqlite3_reset().
|
||
|
|
But wildcards can be rebound to new values after an sqlite3_reset().
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
After an SQL statement has been prepared (and optionally bound), it
|
||
|
|
is executed using:
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<blockquote><pre>
|
||
|
|
int sqlite3_step(sqlite3_stmt*);
|
||
|
|
</pre></blockquote>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The sqlite3_step() routine return SQLITE_ROW if it is returning a single
|
||
|
|
row of the result set, or SQLITE_DONE if execution has completed, either
|
||
|
|
normally or due to an error. It might also return SQLITE_BUSY if it is
|
||
|
|
unable to open the database file. If the return value is SQLITE_ROW, then
|
||
|
|
the following routines can be used to extract information about that row
|
||
|
|
of the result set:
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<blockquote><pre>
|
||
|
|
const void *sqlite3_column_blob(sqlite3_stmt*, int iCol);
|
||
|
|
int sqlite3_column_bytes(sqlite3_stmt*, int iCol);
|
||
|
|
int sqlite3_column_bytes16(sqlite3_stmt*, int iCol);
|
||
|
|
int sqlite3_column_count(sqlite3_stmt*);
|
||
|
|
const char *sqlite3_column_decltype(sqlite3_stmt *, int iCol);
|
||
|
|
const void *sqlite3_column_decltype16(sqlite3_stmt *, int iCol);
|
||
|
|
double sqlite3_column_double(sqlite3_stmt*, int iCol);
|
||
|
|
int sqlite3_column_int(sqlite3_stmt*, int iCol);
|
||
|
|
long long int sqlite3_column_int64(sqlite3_stmt*, int iCol);
|
||
|
|
const char *sqlite3_column_name(sqlite3_stmt*, int iCol);
|
||
|
|
const void *sqlite3_column_name16(sqlite3_stmt*, int iCol);
|
||
|
|
const unsigned char *sqlite3_column_text(sqlite3_stmt*, int iCol);
|
||
|
|
const void *sqlite3_column_text16(sqlite3_stmt*, int iCol);
|
||
|
|
int sqlite3_column_type(sqlite3_stmt*, int iCol);
|
||
|
|
</pre></blockquote>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The
|
||
|
|
<a href="capi3ref.html#sqlite3_column_count">sqlite3_column_count()</a>
|
||
|
|
function returns the number of columns in
|
||
|
|
the results set. sqlite3_column_count() can be called at any time after
|
||
|
|
sqlite3_prepare().
|
||
|
|
<a href="capi3ref.html#sqlite3_data_count">sqlite3_data_count()</a>
|
||
|
|
works similarly to
|
||
|
|
sqlite3_column_count() except that it only works following sqlite3_step().
|
||
|
|
If the previous call to sqlite3_step() returned SQLITE_DONE or an error code,
|
||
|
|
then sqlite3_data_count() will return 0 whereas sqlite3_column_count() will
|
||
|
|
continue to return the number of columns in the result set.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>Returned data is examined using the other sqlite3_column_***() functions,
|
||
|
|
all of which take a column number as their second parameter. Columns are
|
||
|
|
zero-indexed from left to right. Note that this is different to parameters,
|
||
|
|
which are indexed starting at one.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The sqlite3_column_type() function returns the
|
||
|
|
datatype for the value in the Nth column. The return value is one
|
||
|
|
of these:
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<blockquote><pre>
|
||
|
|
#define SQLITE_INTEGER 1
|
||
|
|
#define SQLITE_FLOAT 2
|
||
|
|
#define SQLITE_TEXT 3
|
||
|
|
#define SQLITE_BLOB 4
|
||
|
|
#define SQLITE_NULL 5
|
||
|
|
</pre></blockquote>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The sqlite3_column_decltype() routine returns text which is the
|
||
|
|
declared type of the column in the CREATE TABLE statement. For an
|
||
|
|
expression, the return type is an empty string. sqlite3_column_name()
|
||
|
|
returns the name of the Nth column. sqlite3_column_bytes() returns
|
||
|
|
the number of bytes in a column that has type BLOB or the number of bytes
|
||
|
|
in a TEXT string with UTF-8 encoding. sqlite3_column_bytes16() returns
|
||
|
|
the same value for BLOBs but for TEXT strings returns the number of bytes
|
||
|
|
in a UTF-16 encoding.
|
||
|
|
sqlite3_column_blob() return BLOB data.
|
||
|
|
sqlite3_column_text() return TEXT data as UTF-8.
|
||
|
|
sqlite3_column_text16() return TEXT data as UTF-16.
|
||
|
|
sqlite3_column_int() return INTEGER data in the host machines native
|
||
|
|
integer format.
|
||
|
|
sqlite3_column_int64() returns 64-bit INTEGER data.
|
||
|
|
Finally, sqlite3_column_double() return floating point data.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
It is not necessary to retrieve data in the format specify by
|
||
|
|
sqlite3_column_type(). If a different format is requested, the data
|
||
|
|
is converted automatically.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
Data format conversions can invalidate the pointer returned by
|
||
|
|
prior calls to sqlite3_column_blob(), sqlite3_column_text(), and/or
|
||
|
|
sqlite3_column_text16(). Pointers might be invalided in the following
|
||
|
|
cases:
|
||
|
|
</p>
|
||
|
|
<ul>
|
||
|
|
<li><p>
|
||
|
|
The initial content is a BLOB and sqlite3_column_text()
|
||
|
|
or sqlite3_column_text16()
|
||
|
|
is called. A zero-terminator might need to be added to the string.
|
||
|
|
</p></li>
|
||
|
|
<li><p>
|
||
|
|
The initial content is UTF-8 text and sqlite3_column_bytes16() or
|
||
|
|
sqlite3_column_text16() is called. The content must be converted to UTF-16.
|
||
|
|
</p></li>
|
||
|
|
<li><p>
|
||
|
|
The initial content is UTF-16 text and sqlite3_column_bytes() or
|
||
|
|
sqlite3_column_text() is called. The content must be converted to UTF-8.
|
||
|
|
</p></li>
|
||
|
|
</ul>
|
||
|
|
<p>
|
||
|
|
Note that conversions between UTF-16be and UTF-16le
|
||
|
|
are always done in place and do
|
||
|
|
not invalidate a prior pointer, though of course the content of the buffer
|
||
|
|
that the prior pointer points to will have been modified. Other kinds
|
||
|
|
of conversion are done in place when it is possible, but sometime it is
|
||
|
|
not possible and in those cases prior pointers are invalidated.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The safest and easiest to remember policy is this: assume that any
|
||
|
|
result from
|
||
|
|
<ul>
|
||
|
|
<li>sqlite3_column_blob(),</li>
|
||
|
|
<li>sqlite3_column_text(), or</li>
|
||
|
|
<li>sqlite3_column_text16()</li>
|
||
|
|
</ul>
|
||
|
|
is invalided by subsequent calls to
|
||
|
|
<ul>
|
||
|
|
<li>sqlite3_column_bytes(),</li>
|
||
|
|
<li>sqlite3_column_bytes16(),</li>
|
||
|
|
<li>sqlite3_column_text(), or</li>
|
||
|
|
<li>sqlite3_column_text16().</li>
|
||
|
|
</ul>
|
||
|
|
This means that you should always call sqlite3_column_bytes() or
|
||
|
|
sqlite3_column_bytes16() <u>before</u> calling sqlite3_column_blob(),
|
||
|
|
sqlite3_column_text(), or sqlite3_column_text16().
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<h4>2.3 User-defined functions</h4>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
User defined functions can be created using the following routine:
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<blockquote><pre>
|
||
|
|
typedef struct sqlite3_value sqlite3_value;
|
||
|
|
int sqlite3_create_function(
|
||
|
|
sqlite3 *,
|
||
|
|
const char *zFunctionName,
|
||
|
|
int nArg,
|
||
|
|
int eTextRep,
|
||
|
|
void*,
|
||
|
|
void (*xFunc)(sqlite3_context*,int,sqlite3_value**),
|
||
|
|
void (*xStep)(sqlite3_context*,int,sqlite3_value**),
|
||
|
|
void (*xFinal)(sqlite3_context*)
|
||
|
|
);
|
||
|
|
int sqlite3_create_function16(
|
||
|
|
sqlite3*,
|
||
|
|
const void *zFunctionName,
|
||
|
|
int nArg,
|
||
|
|
int eTextRep,
|
||
|
|
void*,
|
||
|
|
void (*xFunc)(sqlite3_context*,int,sqlite3_value**),
|
||
|
|
void (*xStep)(sqlite3_context*,int,sqlite3_value**),
|
||
|
|
void (*xFinal)(sqlite3_context*)
|
||
|
|
);
|
||
|
|
#define SQLITE_UTF8 1
|
||
|
|
#define SQLITE_UTF16 2
|
||
|
|
#define SQLITE_UTF16BE 3
|
||
|
|
#define SQLITE_UTF16LE 4
|
||
|
|
#define SQLITE_ANY 5
|
||
|
|
</pre></blockquote>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The nArg parameter specifies the number of arguments to the function.
|
||
|
|
A value of 0 indicates that any number of arguments is allowed. The
|
||
|
|
eTextRep parameter specifies what representation text values are expected
|
||
|
|
to be in for arguments to this function. The value of this parameter should
|
||
|
|
be one of the parameters defined above. SQLite version 3 allows multiple
|
||
|
|
implementations of the same function using different text representations.
|
||
|
|
The database engine chooses the function that minimization the number
|
||
|
|
of text conversions required.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
Normal functions specify only xFunc and leave xStep and xFinal set to NULL.
|
||
|
|
Aggregate functions specify xStep and xFinal and leave xFunc set to NULL.
|
||
|
|
There is no separate sqlite3_create_aggregate() API.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The function name is specified in UTF-8. A separate sqlite3_create_function16()
|
||
|
|
API works the same as sqlite_create_function()
|
||
|
|
except that the function name is specified in UTF-16 host byte order.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
Notice that the parameters to functions are now pointers to sqlite3_value
|
||
|
|
structures instead of pointers to strings as in SQLite version 2.X.
|
||
|
|
The following routines are used to extract useful information from these
|
||
|
|
"values":
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<blockquote><pre>
|
||
|
|
const void *sqlite3_value_blob(sqlite3_value*);
|
||
|
|
int sqlite3_value_bytes(sqlite3_value*);
|
||
|
|
int sqlite3_value_bytes16(sqlite3_value*);
|
||
|
|
double sqlite3_value_double(sqlite3_value*);
|
||
|
|
int sqlite3_value_int(sqlite3_value*);
|
||
|
|
long long int sqlite3_value_int64(sqlite3_value*);
|
||
|
|
const unsigned char *sqlite3_value_text(sqlite3_value*);
|
||
|
|
const void *sqlite3_value_text16(sqlite3_value*);
|
||
|
|
int sqlite3_value_type(sqlite3_value*);
|
||
|
|
</pre></blockquote>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
Function implementations use the following APIs to acquire context and
|
||
|
|
to report results:
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<blockquote><pre>
|
||
|
|
void *sqlite3_aggregate_context(sqlite3_context*, int nbyte);
|
||
|
|
void *sqlite3_user_data(sqlite3_context*);
|
||
|
|
void sqlite3_result_blob(sqlite3_context*, const void*, int n, void(*)(void*));
|
||
|
|
void sqlite3_result_double(sqlite3_context*, double);
|
||
|
|
void sqlite3_result_error(sqlite3_context*, const char*, int);
|
||
|
|
void sqlite3_result_error16(sqlite3_context*, const void*, int);
|
||
|
|
void sqlite3_result_int(sqlite3_context*, int);
|
||
|
|
void sqlite3_result_int64(sqlite3_context*, long long int);
|
||
|
|
void sqlite3_result_null(sqlite3_context*);
|
||
|
|
void sqlite3_result_text(sqlite3_context*, const char*, int n, void(*)(void*));
|
||
|
|
void sqlite3_result_text16(sqlite3_context*, const void*, int n, void(*)(void*));
|
||
|
|
void sqlite3_result_value(sqlite3_context*, sqlite3_value*);
|
||
|
|
void *sqlite3_get_auxdata(sqlite3_context*, int);
|
||
|
|
void sqlite3_set_auxdata(sqlite3_context*, int, void*, void (*)(void*));
|
||
|
|
</pre></blockquote>
|
||
|
|
|
||
|
|
<h4>2.4 User-defined collating sequences</h4>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The following routines are used to implement user-defined
|
||
|
|
collating sequences:
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<blockquote><pre>
|
||
|
|
sqlite3_create_collation(sqlite3*, const char *zName, int eTextRep, void*,
|
||
|
|
int(*xCompare)(void*,int,const void*,int,const void*));
|
||
|
|
sqlite3_create_collation16(sqlite3*, const void *zName, int eTextRep, void*,
|
||
|
|
int(*xCompare)(void*,int,const void*,int,const void*));
|
||
|
|
sqlite3_collation_needed(sqlite3*, void*,
|
||
|
|
void(*)(void*,sqlite3*,int eTextRep,const char*));
|
||
|
|
sqlite3_collation_needed16(sqlite3*, void*,
|
||
|
|
void(*)(void*,sqlite3*,int eTextRep,const void*));
|
||
|
|
</pre></blockquote>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The sqlite3_create_collation() function specifies a collating sequence name
|
||
|
|
and a comparison function to implement that collating sequence. The
|
||
|
|
comparison function is only used for comparing text values. The eTextRep
|
||
|
|
parameter is one of SQLITE_UTF8, SQLITE_UTF16LE, SQLITE_UTF16BE, or
|
||
|
|
SQLITE_ANY to specify which text representation the comparison function works
|
||
|
|
with. Separate comparison functions can exist for the same collating
|
||
|
|
sequence for each of the UTF-8, UTF-16LE and UTF-16BE text representations.
|
||
|
|
The sqlite3_create_collation16() works like sqlite3_create_collation() except
|
||
|
|
that the collation name is specified in UTF-16 host byte order instead of
|
||
|
|
in UTF-8.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The sqlite3_collation_needed() routine registers a callback which the
|
||
|
|
database engine will invoke if it encounters an unknown collating sequence.
|
||
|
|
The callback can lookup an appropriate comparison function and invoke
|
||
|
|
sqlite_3_create_collation() as needed. The fourth parameter to the callback
|
||
|
|
is the name of the collating sequence in UTF-8. For sqlite3_collation_need16()
|
||
|
|
the callback sends the collating sequence name in UTF-16 host byte order.
|
||
|
|
</p>
|
||
|
|
}
|
||
|
|
footer $rcsid
|