shell: add .walmethodslist

The command is heavily inspired by .vfslist
and lists all the registered custom WAL methods.

Author: psarna

src/main.c

@@ -3975,6 +3975,11 @@ int sqlite3_file_control(sqlite3 *db, const char *zDbName, int op, void *pArg){
     }else if( op==SQLITE_FCNTL_DATA_VERSION ){
       *(unsigned int*)pArg = sqlite3PagerDataVersion(pPager);
       rc = SQLITE_OK;
+#ifndef SQLITE_OMIT_WAL
+    }else if( op==SQLITE_FCNTL_WAL_METHODS_POINTER ){
+      *(libsql_wal_methods**)pArg = sqlite3PagerWalMethods(pPager);
+      rc = SQLITE_OK;
+#endif
     }else if( op==SQLITE_FCNTL_RESERVE_BYTES ){
       int iNew = *(int*)pArg;
       *(int*)pArg = sqlite3BtreeGetRequestedReserve(pBtree);

src/pager.c

@@ -7050,6 +7050,15 @@ sqlite3_vfs *sqlite3PagerVfs(Pager *pPager){
   return pPager->pVfs;
 }
 
+#ifndef SQLITE_OMIT_WAL
+/*
+** Return the WAL methods structure for the pager.
+*/
+libsql_wal_methods *sqlite3PagerWalMethods(Pager *pPager){
+  return pPager->pWalMethods;
+}
+#endif
+
 /*
 ** Return the file handle for the database file associated
 ** with the pager.  This might return NULL if the file has

src/pager.h

@@ -214,6 +214,9 @@ u32 sqlite3PagerDataVersion(Pager*);
 int sqlite3PagerMemUsed(Pager*);
 const char *sqlite3PagerFilename(const Pager*, int);
 sqlite3_vfs *sqlite3PagerVfs(Pager*);
+#ifndef SQLITE_OMIT_WAL
+libsql_wal_methods *sqlite3PagerWalMethods(Pager*);
+#endif
 sqlite3_file *sqlite3PagerFile(Pager*);
 sqlite3_file *sqlite3PagerJrnlFile(Pager*);
 const char *sqlite3PagerJournalname(Pager*);

src/shell.c.in

@@ -10836,6 +10836,24 @@ static int do_meta_command(char *zLine, ShellState *p){
     }
   }else
 
+#ifndef SQLITE_OMIT_WAL
+  if( c=='w' && cli_strncmp(azArg[0], "walmethodslist", n)==0 ){
+    libsql_wal_methods *pWal;
+    libsql_wal_methods *pCurrent = 0;
+    if( p->db ){
+      sqlite3_file_control(p->db, "main", SQLITE_FCNTL_WAL_METHODS_POINTER, &pCurrent);
+    }
+    for(pWal=libsql_wal_methods_find(0); pWal; pWal=libsql_wal_methods_next(pWal)){
+      
+      utf8_printf(p->out, "wal.zName      = \"%s\"%s\n", libsql_wal_methods_name(pWal),
+           pWal==pCurrent ? "  <--- CURRENT" : "");
+      if( libsql_wal_methods_next(pWal) ){
+        raw_printf(p->out, "-----------------------------------\n");
+      }
+    }
+  }else
+#endif
+
   if( c=='w' && cli_strncmp(azArg[0], "wheretrace", n)==0 ){
     unsigned int x = nArg>=2 ? (unsigned int)integerValue(azArg[1]) : 0xffffffff;
     sqlite3_test_control(SQLITE_TESTCTRL_TRACEFLAGS, 3, &x);

src/sqlite.h.in

@@ -1012,6 +1012,13 @@ struct sqlite3_io_methods {
 ** ^When there are multiple VFS shims in the stack, this opcode finds the
 ** upper-most shim only.
 **
+** <li>[[SQLITE_FCNTL_WAL_METHODS_POINTER]]
+** ^The [SQLITE_FCNTL_WAL_METHODS_POINTER] opcode finds a pointer to the top-level
+** WAL methods currently in use.  ^(The argument X in
+** sqlite3_file_control(db,SQLITE_FCNTL_WAL_METHODS_POINTER,X) must be
+** of type "[libsql_wal_methods] **".  This opcodes will set *X
+** to a pointer to the top-level WAL methods.)^
+**
 ** <li>[[SQLITE_FCNTL_PRAGMA]]
 ** ^Whenever a [PRAGMA] statement is parsed, an [SQLITE_FCNTL_PRAGMA] 
 ** file control is sent to the open [sqlite3_file] object corresponding
@@ -1242,6 +1249,9 @@ struct sqlite3_io_methods {
 #define SQLITE_FCNTL_EXTERNAL_READER        40
 #define SQLITE_FCNTL_CKSM_FILE              41
 
+// libSQL extension
+#define SQLITE_FCNTL_WAL_METHODS_POINTER   129
+
 /* deprecated names */
 #define SQLITE_GET_LOCKPROXYFILE      SQLITE_FCNTL_GET_LOCKPROXYFILE
 #define SQLITE_SET_LOCKPROXYFILE      SQLITE_FCNTL_SET_LOCKPROXYFILE
@@ -7733,6 +7743,9 @@ libsql_wal_methods *libsql_wal_methods_find(const char *zName);
 int libsql_wal_methods_register(libsql_wal_methods*);
 int libsql_wal_methods_unregister(libsql_wal_methods*);
 
+libsql_wal_methods *libsql_wal_methods_next(libsql_wal_methods *w);
+const char *libsql_wal_methods_name(libsql_wal_methods *w);
+
 /*
 ** CAPI3REF: Mutexes
 **

src/wal.c

@@ -4209,4 +4209,12 @@ int libsql_wal_methods_unregister(libsql_wal_methods *pWalMethods) {
   return SQLITE_OK;
 }
 
+libsql_wal_methods *libsql_wal_methods_next(libsql_wal_methods *w) {
+  return w->pNext;
+}
+
+const char *libsql_wal_methods_name(libsql_wal_methods *w) {
+  return w->zName;
+}
+
 #endif /* #ifndef SQLITE_OMIT_WAL */