Introduce CS_INTERRUPT_CB and corresponding return values: CS_INT_*.

Define CS_INTERRUPT_CB's numeric value alongside other CS_*_CBs';
start a new 94xx range to avoid confusion with properties.
(Sybase/SAP ctlib has no such callback.)  Allow specification on
either the connection or the context level as usual, with the help of
a shim installed on demand to minimize interference with tds_select's
optimization for the no-handler case.  For CS_INT_*, copy TDS_INT_*
and confirm their equality at compile time as with CS_NULLTERM et al.

Signed-off-by: Aaron M. Ucko <ucko@ncbi.nlm.nih.gov>

include/cspublic.h

@@ -69,6 +69,7 @@ extern "C"
 typedef CS_RETCODE(*CS_CSLIBMSG_FUNC) (CS_CONTEXT *, CS_CLIENTMSG *);
 typedef CS_RETCODE(*CS_CLIENTMSG_FUNC) (CS_CONTEXT *, CS_CONNECTION *, CS_CLIENTMSG *);
 typedef CS_RETCODE(*CS_SERVERMSG_FUNC) (CS_CONTEXT *, CS_CONNECTION *, CS_SERVERMSG *);
+typedef CS_RETCODE(*CS_INTERRUPT_FUNC) (CS_CONNECTION *);
 
 
 #define CS_IODATA          TDS_STATIC_CAST(CS_INT, 1600)
@@ -437,6 +438,7 @@ enum
 #define CS_SECSESSION_CB	8
 #define CS_SIGNAL_CB		100
 #define CS_MESSAGE_CB		9119
+#define CS_INTERRUPT_CB		9400
 
 /* string types */
 #define CS_NULLTERM	-9
@@ -773,6 +775,11 @@ enum
 #define CS_SERVERMSG_TYPE 4701
 #define CS_ALLMSG_TYPE 4702
 
+/* CS_INTERRUPT_CB return values */
+#define CS_INT_CONTINUE 1
+#define CS_INT_CANCEL 2
+#define CS_INT_TIMEOUT 3
+
 CS_RETCODE cs_convert(CS_CONTEXT * ctx, CS_DATAFMT * srcfmt, CS_VOID * srcdata, CS_DATAFMT * destfmt, CS_VOID * destdata,
 		      CS_INT * resultlen);
 CS_RETCODE cs_ctx_alloc(CS_INT version, CS_CONTEXT ** ctx);

include/ctlib.h

@@ -152,6 +152,7 @@ struct _cs_context
 	CS_CSLIBMSG_FUNC _cslibmsg_cb;
 	CS_CLIENTMSG_FUNC _clientmsg_cb;
 	CS_SERVERMSG_FUNC _servermsg_cb;
+	CS_INTERRUPT_FUNC _interrupt_cb;
 	/* code changes start here - CS_CONFIG - 01*/
 	void *userdata;
 	int userdata_len;
@@ -190,6 +191,7 @@ struct _cs_connection
 	TDSSOCKET *tds_socket;
 	CS_CLIENTMSG_FUNC _clientmsg_cb;
 	CS_SERVERMSG_FUNC _servermsg_cb;
+	CS_INTERRUPT_FUNC _interrupt_cb;
 	void *userdata;
 	int userdata_len;
 	CS_LOCALE *locale;
@@ -380,6 +382,7 @@ typedef union
  */
 TDSRET _ct_handle_server_message(const TDSCONTEXT * ctxptr, TDSSOCKET * tdsptr, TDSMESSAGE * msgptr);
 int _ct_handle_client_message(const TDSCONTEXT * ctxptr, TDSSOCKET * tdsptr, TDSMESSAGE * msgptr);
+int _ct_handle_interrupt(void * ptr);
 TDS_SERVER_TYPE _ct_get_server_type(TDSSOCKET *tds, int datatype);
 int _ct_bind_data(CS_CONTEXT *ctx, TDSRESULTINFO * resinfo, TDSRESULTINFO *bindinfo, CS_INT offset);
 int _ct_get_client_type(const TDSCOLUMN *col, bool describe);

include/freetds/tds.h

@@ -1009,6 +1009,7 @@ typedef struct tds_multiple
 /* forward declaration */
 typedef struct tds_context TDSCONTEXT;
 typedef int (*err_handler_t) (const TDSCONTEXT *, TDSSOCKET *, TDSMESSAGE *);
+typedef int (*int_handler_t) (void *);
 
 struct tds_context
 {

src/ctlib/ct.c

@@ -362,6 +362,10 @@ ct_callback(CS_CONTEXT * ctx, CS_CONNECTION * con, CS_INT action, CS_INT type, C
 		case CS_SERVERMSG_CB:
 			out_func = (CS_VOID *) (con ? con->_servermsg_cb : ctx->_servermsg_cb);
 			break;
+		case CS_INTERRUPT_CB:
+			out_func = (CS_VOID *) (con ? con->_interrupt_cb
+						: ctx->_interrupt_cb);
+			break;
 		default:
 			_ctclient_msg(ctx, con, "ct_callback()", 1, 1, 1, 5, "%d, %s", type, "type");
 			return CS_FAIL;
@@ -389,6 +393,14 @@ ct_callback(CS_CONTEXT * ctx, CS_CONNECTION * con, CS_INT action, CS_INT type, C
 		else
 			ctx->_servermsg_cb = (CS_SERVERMSG_FUNC) funcptr;
 		break;
+	case CS_INTERRUPT_CB:
+		/* install shim on demand */
+		ctx->tds_ctx->int_handler = _ct_handle_interrupt;
+		if (con)
+			con->_interrupt_cb = (CS_INTERRUPT_FUNC) funcptr;
+		else
+			ctx->_interrupt_cb = (CS_INTERRUPT_FUNC) funcptr;
+		break;
 	default:
 		_ctclient_msg(ctx, con, "ct_callback()", 1, 1, 1, 5, "%d, %s", type, "type");
 		return CS_FAIL;

src/ctlib/ctutil.c

@@ -54,6 +54,9 @@ TEST_EQUAL(t12,CS_COMPUTEFMT_RESULT,TDS_COMPUTEFMT_RESULT);
 TEST_EQUAL(t13,CS_ROWFMT_RESULT,TDS_ROWFMT_RESULT);
 TEST_EQUAL(t14,CS_MSG_RESULT,TDS_MSG_RESULT);
 TEST_EQUAL(t15,CS_DESCRIBE_RESULT,TDS_DESCRIBE_RESULT);
+TEST_EQUAL(t16,CS_INT_CONTINUE,TDS_INT_CONTINUE);
+TEST_EQUAL(t17,CS_INT_CANCEL,TDS_INT_CANCEL);
+TEST_EQUAL(t18,CS_INT_TIMEOUT,TDS_INT_TIMEOUT);
 
 #define TEST_ATTRIBUTE(t,sa,fa,sb,fb) \
 	TDS_COMPILE_CHECK(t,sizeof(((sa*)0)->fa) == sizeof(((sb*)0)->fb) && TDS_OFFSET(sa,fa) == TDS_OFFSET(sb,fb))
@@ -161,6 +164,21 @@ _ct_handle_client_message(const TDSCONTEXT * ctx_tds, TDSSOCKET * tds, TDSMESSAG
 	return TDS_INT_CANCEL;
 }
 
+/*
+ * interrupt handler, installed on demand to avoid gratuitously interfering
+ * with tds_select's optimization for the no-handler case */
+int
+_ct_handle_interrupt(void * ptr)
+{
+	CS_CONNECTION *con = (CS_CONNECTION *) ptr;
+	if (con->_interrupt_cb)
+		return (*con->_interrupt_cb)(con);
+	else if (con->ctx->_interrupt_cb)
+		return (*con->ctx->_interrupt_cb)(con);
+	else
+		return TDS_INT_CONTINUE;
+}
+
 /* message handler */
 TDSRET
 _ct_handle_server_message(const TDSCONTEXT * ctx_tds, TDSSOCKET * tds, TDSMESSAGE * msg)