New experimental API for attaching client data to a database connection.

FossilOrigin-Name: d542837fdb42ebe810fc99225860d2cc7e6dd829a635bde820a09beff6bcb481

manifest

@@ -1,5 +1,5 @@
-C When\sa\sJS\sSQLTester\sscript\sthrows,\sreport\sthe\sexception\sdetails\sback\sto\sthe\sUI\sregardless\sof\swhether\sit's\sfatal.
+C New\sexperimental\sAPI\sfor\sattaching\sclient\sdata\sto\sa\sdatabase\sconnection.
-D 2023-08-30T14:20:02.025
+D 2023-08-30T15:20:15.256
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -668,7 +668,7 @@ F src/insert.c 3f0a94082d978bbdd33c38fefea15346c6c6bffb70bc645a71dc0f1f87dd3276
 F src/json.c ae840f87b418f039f5d336b488933d09396bd31e6b31e855b93055ccaee4e255
 F src/legacy.c d7874bc885906868cd51e6c2156698f2754f02d9eee1bae2d687323c3ca8e5aa
 F src/loadext.c 98cfba10989b3da6f1807ad42444017742db7f100a54f1032af7a8b1295912c0
-F src/main.c 6287177c498427658b892fd816434d36bf9b85b33bf65d5280b897c3b34cee8c
+F src/main.c 5c28d8b05896007a820fb1f4b9089c8e237813bf51f7de2ebc7ce88cb0f0b2ba
 F src/malloc.c 47b82c5daad557d9b963e3873e99c22570fb470719082c6658bf64e3012f7d23
 F src/mem0.c 6a55ebe57c46ca1a7d98da93aaa07f99f1059645
 F src/mem1.c 3bb59158c38e05f6270e761a9f435bf19827a264c13d1631c58b84bdc96d73b2
@@ -707,10 +707,10 @@ F src/resolve.c 37953a5f36c60bea413c3c04efcd433b6177009f508ef2ace0494728912fe2e9
 F src/rowset.c 8432130e6c344b3401a8874c3cb49fefe6873fec593294de077afea2dce5ec97
 F src/select.c 5f545a2c8702d4d3430bbb188cfec47d6c122d899061ef00cbe56af14591c574
 F src/shell.c.in 2f9be25294b68b07e7e81f0adcec4475aba6011b64f160e414efe226910c4d7b
-F src/sqlite.h.in 73a366c1c45d5ac9888cfe81c458826a44498531d106cfb4f328193ab5f6f17d
+F src/sqlite.h.in 9f1ae109025327841ecd4f1c7fbe5550a59959ccea444e4d6e388ee5d4135602
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
 F src/sqlite3ext.h 2f30b2671f4c03cd27a43f039e11251391066c97d11385f5f963bb40b03038ac
-F src/sqliteInt.h 025ed58a41968ef80d64cdc194caa8dd207b0256b147253d762fdac7a62408f9
+F src/sqliteInt.h 985a09af9a8ce7862318ff77550b9b172e684b5a10e55dd96796e08e48f6dbca
 F src/sqliteLimit.h 33b1c9baba578d34efe7dfdb43193b366111cdf41476b1e82699e14c11ee1fb6
 F src/status.c 160c445d7d28c984a0eae38c144f6419311ed3eace59b44ac6dafc20db4af749
 F src/table.c 0f141b58a16de7e2fbe81c308379e7279f4c6b50eb08efeec5892794a0ba30d1
@@ -2115,8 +2115,11 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P b530792a514d95c4e8f93cf2170d9fc4de367055fa1704fc171551c946024fa9
+P 273d3b05f630d399d42914e95c416b107b4746bbef129cfba9d00fd921666261
-R 27c4b366fbb2810d013255774a7479ce
+R ea42982c5b96fe2a959e6a802572e9d0
-U stephan
+T *branch * db-client-data
-Z 3efc7b20eec1af6f89785f42be992e20
+T *sym-db-client-data *
+T -sym-trunk *
+U drh
+Z da4f47e3406f7c1072eed31bdeabf988
 # Remove this line to create a well-formed Fossil manifest.

manifest.uuid

@@ -1 +1 @@
-273d3b05f630d399d42914e95c416b107b4746bbef129cfba9d00fd921666261
+d542837fdb42ebe810fc99225860d2cc7e6dd829a635bde820a09beff6bcb481

src/main.c

@@ -1253,6 +1253,14 @@ static int sqlite3Close(sqlite3 *db, int forceZombie){
   }
 #endif
 
+  while( db->pDbData ){
+    DbClientData *p = db->pDbData;
+    db->pDbData = p->pNext;
+    assert( p->pData!=0 );
+    if( p->xDestructor ) p->xDestructor(p->pData);
+    sqlite3_free(p);
+  }
+
   /* Convert the connection into a zombie and then close it.
   */
   db->eOpenState = SQLITE_STATE_ZOMBIE;
@@ -3710,6 +3718,55 @@ int sqlite3_collation_needed16(
 }
 #endif /* SQLITE_OMIT_UTF16 */
 
+/*
+** Find existing client data.
+*/
+void *sqlite3_get_clientdata(sqlite3 *db, const char *zName){
+  DbClientData *p;
+  for(p=db->pDbData; p && strcmp(p->zName,zName); p=p->pNext){}
+  return p;
+}
+
+/*
+** Add new client data to a database connection.
+*/
+int sqlite3_set_clientdata(
+  sqlite3 *db,                   /* Attach client data to this connection */
+  const char *zName,             /* Name of the client data */
+  void *pData,                   /* The client data itself */
+  void (*xDestructor)(void*)     /* Destructor */
+){
+  DbClientData *p, **pp;
+  pp = &db->pDbData;
+  for(p=db->pDbData; p && strcmp(p->zName,zName); p=p->pNext){
+    pp = &p->pNext;
+  }
+  if( p ){
+    if( p->pData && p->xDestructor ) p->xDestructor(p->pData);
+    if( pData==0 ){
+      *pp = p->pNext;
+      sqlite3_free(p);
+      return SQLITE_OK;
+    }
+  }else if( pData==0 ){
+    return SQLITE_OK;
+  }else{
+    size_t n = strlen(zName);
+    p = sqlite3_malloc64( sizeof(DbClientData)+n+1 );
+    if( p==0 ){
+      if( pData && xDestructor ) xDestructor(pData);
+      return SQLITE_NOMEM;
+    }
+    memcpy(p->zName, zName, n+1);
+    p->pNext = db->pDbData;
+    db->pDbData = p;
+  }
+  p->pData = pData;
+  p->xDestructor = xDestructor;
+  return SQLITE_OK;
+}
+
+
 #ifndef SQLITE_OMIT_DEPRECATED
 /*
 ** This function is now an anachronism. It used to be used to recover from a

src/sqlite.h.in

@@ -5325,6 +5325,7 @@ int sqlite3_finalize(sqlite3_stmt *pStmt);
 */
 int sqlite3_reset(sqlite3_stmt *pStmt);
 
+
 /*
 ** CAPI3REF: Create Or Redefine SQL Functions
 ** KEYWORDS: {function creation routines}
@@ -5879,32 +5880,32 @@ sqlite3 *sqlite3_context_db_handle(sqlite3_context*);
 ** METHOD: sqlite3_context
 **
 ** These functions may be used by (non-aggregate) SQL functions to
-** associate metadata with argument values. If the same value is passed to
+** associate auxiliary data with argument values. If the same argument
-** multiple invocations of the same SQL function during query execution, under
+** value is passed to multiple invocations of the same SQL function during
-** some circumstances the associated metadata may be preserved.  An example
+** query execution, under some circumstances the associated auxiliary data
-** of where this might be useful is in a regular-expression matching
+** might be preserved.  An example of where this might be useful is in a
-** function. The compiled version of the regular expression can be stored as
+** regular-expression matching function. The compiled version of the regular
-** metadata associated with the pattern string. 
+** expression can be stored as auxiliary data associated with the pattern string. 
 ** Then as long as the pattern string remains the same,
 ** the compiled regular expression can be reused on multiple
 ** invocations of the same function.
 **
-** ^The sqlite3_get_auxdata(C,N) interface returns a pointer to the metadata
+** ^The sqlite3_get_auxdata(C,N) interface returns a pointer to the auxiliary data
 ** associated by the sqlite3_set_auxdata(C,N,P,X) function with the Nth argument
 ** value to the application-defined function.  ^N is zero for the left-most
-** function argument.  ^If there is no metadata
+** function argument.  ^If there is no auxiliary data
 ** associated with the function argument, the sqlite3_get_auxdata(C,N) interface
 ** returns a NULL pointer.
 **
-** ^The sqlite3_set_auxdata(C,N,P,X) interface saves P as metadata for the N-th
+** ^The sqlite3_set_auxdata(C,N,P,X) interface saves P as auxiliary data for the
-** argument of the application-defined function.  ^Subsequent
+** N-th argument of the application-defined function.  ^Subsequent
 ** calls to sqlite3_get_auxdata(C,N) return P from the most recent
-** sqlite3_set_auxdata(C,N,P,X) call if the metadata is still valid or
+** sqlite3_set_auxdata(C,N,P,X) call if the auxiliary data is still valid or
-** NULL if the metadata has been discarded.
+** NULL if the auxiliary data has been discarded.
 ** ^After each call to sqlite3_set_auxdata(C,N,P,X) where X is not NULL,
 ** SQLite will invoke the destructor function X with parameter P exactly
-** once, when the metadata is discarded.
+** once, when the auxiliary data is discarded.
-** SQLite is free to discard the metadata at any time, including: <ul>
+** SQLite is free to discard the auxiliary data at any time, including: <ul>
 ** <li> ^(when the corresponding function parameter changes)^, or
 ** <li> ^(when [sqlite3_reset()] or [sqlite3_finalize()] is called for the
 **      SQL statement)^, or
@@ -5920,7 +5921,7 @@ sqlite3 *sqlite3_context_db_handle(sqlite3_context*);
 ** function implementation should not make any use of P after
 ** sqlite3_set_auxdata() has been called.
 **
-** ^(In practice, metadata is preserved between function calls for
+** ^(In practice, auxiliary data is preserved between function calls for
 ** function parameters that are compile-time constants, including literal
 ** values and [parameters] and expressions composed from the same.)^
 **
@@ -5930,10 +5931,60 @@ sqlite3 *sqlite3_context_db_handle(sqlite3_context*);
 **
 ** These routines must be called from the same thread in which
 ** the SQL function is running.
+**
+** See also: [sqlite3_get_clientdata()] and [sqlite3_set_clientdata()].
 */
 void *sqlite3_get_auxdata(sqlite3_context*, int N);
 void sqlite3_set_auxdata(sqlite3_context*, int N, void*, void (*)(void*));
 
+/*
+** CAPI3REF: Database Connection Client Data
+** METHOD: sqlite3
+**
+** These functions are used to associate one or more named pointers
+** with a [database connection].
+** A call to sqlite3_set_clientdata(D,N,P,X) causes the pointer P
+** to be attached to [database connection] D using name N.  Subsequent
+** calls to sqlite3_get_clientdata(D,N) will return a copy of pointer P
+** or a NULL pointer if there were no prior calls to
+** sqlite3_set_clientdata() with the same values of D and N.
+** Names are compared using strcmp() and are thus case sensitive.
+**
+** If P and X are both non-NULL, then the destructor X is invoked with
+** argument P on the first of the following occurrences:
+** <ul>
+** <li> An out-of-memory error occurs during the call to
+**      sqlite3_set_clientdata() which attempts to register pointer P.
+** <li> A subsequent call to sqlite3_set_clientdata(D,N,P,X) is made
+**      with the same D and N parameters.
+** <li> The database connection closes.  SQLite does not make any guarantees
+**      about the order in which destructors are called, only that all
+**      destructors will be called exactly once at some point during the
+**      database connection closingi process.
+** </ul>
+**
+** SQLite does not do anything with client data other than invoke
+** destructors on the client data at the appropriate time.  The intended
+** use for client data is to provide a mechanism for wrapper libraries
+** to store additional information about an SQLite database connection.
+**
+** There is no limit (other than available memory) on the number of different
+** client data pointers (with different names) that can be attached to a
+** single database connection.  However, the implementation is optimized
+** for the case of having only one or two different client data names.
+** Applications and wrapper libraries are discouraged from using more than
+** one client data name each.
+**
+** There is (currently) no way to enumerate the client data pointers
+** associated with a database connection.  The N parameter can be thought
+** of as a secret key such that only code that knows the secret key is able
+** to access the associated data.
+**
+** Database connection client data is only available for SQLite
+** version 3.44.0 ([dateof:3.44.0]) and later.
+*/
+void *sqlite3_get_clientdata(sqlite3*,const char*);
+int sqlite3_set_clientdata(sqlite3*, const char*, void*, void(*)(void*));
 
 /*
 ** CAPI3REF: Constants Defining Special Destructor Behavior

src/sqliteInt.h

@@ -1256,6 +1256,7 @@ typedef struct Column Column;
 typedef struct Cte Cte;
 typedef struct CteUse CteUse;
 typedef struct Db Db;
+typedef struct DbClientData DbClientData;
 typedef struct DbFixer DbFixer;
 typedef struct Schema Schema;
 typedef struct Expr Expr;
@@ -1734,6 +1735,7 @@ struct sqlite3 {
   i64 nDeferredCons;            /* Net deferred constraints this transaction. */
   i64 nDeferredImmCons;         /* Net deferred immediate constraints */
   int *pnBytesFreed;            /* If not NULL, increment this in DbFree() */
+  DbClientData *pDbData;        /* sqlite3_set_clientdata() content */
 #ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
   /* The following variables are all protected by the STATIC_MAIN
   ** mutex, not by sqlite3.mutex. They are used by code in notify.c.
@@ -4341,6 +4343,16 @@ struct CteUse {
 };
 
 
+/* Client data associated with sqlite3_set_clientdata() and
+** sqlite3_get_clientdata().
+*/
+struct DbClientData {
+  DbClientData *pNext;        /* Next in a linked list */
+  void *pData;                /* The data */
+  void (*xDestructor)(void*); /* Destructor.  Might be NULL */
+  char zName[1];              /* Name of this client data. MUST BE LAST */
+};
+
 #ifdef SQLITE_DEBUG
 /*
 ** An instance of the TreeView object is used for printing the content of