libsql-sqlite: Add libsql_stmt_interrupt() API

This adds an API for interrupting a specific statement instead of all
pending operations like `sqlite3_interrupt()` does.

Author: penberg

libsql-sqlite3/src/sqlite.h.in

@@ -5390,6 +5390,8 @@ int sqlite3_finalize(sqlite3_stmt *pStmt);
 int sqlite3_reset(sqlite3_stmt *pStmt);
 
 
+void libsql_stmt_interrupt(sqlite3_stmt *stmt);
+
 /*
 ** CAPI3REF: Create Or Redefine SQL Functions
 ** KEYWORDS: {function creation routines}

libsql-sqlite3/src/vdbeInt.h

@@ -528,6 +528,7 @@ struct Vdbe {
   int nScan;              /* Entries in aScan[] */
   ScanStatus *aScan;      /* Scan definitions for sqlite3_stmt_scanstatus() */
 #endif
+  u8 isInterrupted;      /* True if the statement has been interrupted */
 };
 
 void libsql_inc_row_read(Vdbe *p, int count);

libsql-sqlite3/src/vdbeapi.c

@@ -888,6 +888,18 @@ static int sqlite3Step(Vdbe *p){
   return (rc&db->errMask);
 }
 
+/*
+** Interrupt the statement.
+*/
+void libsql_stmt_interrupt(sqlite3_stmt *pStmt){
+  Vdbe *v = (Vdbe*)pStmt;  /* the prepared statement */
+  if( vdbeSafetyNotNull(v) ){
+    (void)SQLITE_MISUSE_BKPT;
+    return;
+  }
+  v->isInterrupted = 1;
+}
+
 /*
 ** This is the top-level implementation of sqlite3_step().  Call
 ** sqlite3Step() to do most of the work.  If a schema error occurs,
@@ -902,6 +914,9 @@ int sqlite3_step(sqlite3_stmt *pStmt){
   if( vdbeSafetyNotNull(v) ){
     return SQLITE_MISUSE_BKPT;
   }
+  if( v->isInterrupted ){
+    return SQLITE_INTERRUPT;
+  }
   db = v->db;
   sqlite3_mutex_enter(db->mutex);
   while( (rc = sqlite3Step(v))==SQLITE_SCHEMA