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+
+<font color="#7f001f"><p>
+<b>Note:</b>
+This document was written in 2004 as a guide to helping programmers
+move from using SQLite version 2 to SQLite version 3. The information
+in this document is still essentially correct, however there have been
+many changes and enhancements over the years. We recommend that the
+following documents be used instead:
+<ul>
+<li><a href="cintro.html">An Introduction To The SQLite C/C++ Interface</a></li>
+<li><a href="c3ref/intro.html">SQLite C/C++ Reference Guide</a></li>
+</ul>
+</p>
+</font>
+
+<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="c3ref/intro.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="c3ref/open.html">sqlite3_open()</a>, <a href="c3ref/exec.html">sqlite3_exec()</a>, and <a href="c3ref/close.html">sqlite3_close()</a>.
+More control over the execution of the database engine is provided
+using <a href="c3ref/prepare.html">sqlite3_prepare_v2()</a>
+to compile an SQLite statement into byte code and
+<a href="c3ref/step.html">sqlite3_step()</a> to execute that bytecode.
+A family of routines with names beginning with
+<a href="c3ref/column_blob.html">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 <a href="c3ref/exec.html">sqlite3_exec()</a> 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.
+</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 fifth 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="c3ref/bind_blob.html">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="c3ref/column_count.html">sqlite3_column_count()</a>
+function returns the number of columns in
+the results set. sqlite3_column_count() can be called at any time after
+<a href="c3ref/prepare.html">sqlite3_prepare_v2()</a>. <a href="c3ref/data_count.html">sqlite3_data_count()</a> works similarly to
+<a href="c3ref/column_count.html">sqlite3_column_count()</a> except that it only works following <a href="c3ref/step.html">sqlite3_step()</a>.
+If the previous call to <a href="c3ref/step.html">sqlite3_step()</a> returned SQLITE_DONE or an error code,
+then <a href="c3ref/data_count.html">sqlite3_data_count()</a> will return 0 whereas <a href="c3ref/column_count.html">sqlite3_column_count()</a> will
+continue to return the number of columns in the result set.
+</p>
+
+<p>Returned data is examined using the other
+<a href="c3ref/column_blob.html">sqlite3_column_***()</a> 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 <a href="c3ref/column_blob.html">sqlite3_column_type()</a> 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>
+<p align="center"><small><i>This page last modified on <a href="https://sqlite.org/docsrc/honeypot" id="mtimelink" data-href="https://sqlite.org/docsrc/finfo/pages/capi3.in?m=2524a93030a47da74">2009-10-30 17:27:52</a> UTC </small></i></p>
+