From 9935ca9e91f79b4f5ee6e9a7f94912b7992e8858 Mon Sep 17 00:00:00 2001
From: Sebastian Harl <sh@tokkee.org>
Date: Mon, 1 Dec 2014 17:34:59 +0100
Subject: [PATCH] store: Added sdb_store_expr_typed.

This function creates an expression which evaluates another expression in the
context of an object's sibling. The sibling is specified by type and refers to
a parent or child node of the specified type.
---
 src/core/store-private.h |  1 +
 src/core/store_expr.c    | 31 ++++++++++++++++++++++++++++++-
 src/include/core/store.h | 12 ++++++++++++
 3 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/src/core/store-private.h b/src/core/store-private.h
index d2ea3f9..3ae6c43 100644
--- a/src/core/store-private.h
+++ b/src/core/store-private.h
@@ -108,6 +108,7 @@ typedef struct {
  */
 
 enum {
+	TYPED_EXPR  = -3, /* obj type stored in data.data.integer */
 	ATTR_VALUE  = -2, /* attr name stored in data.data.string */
 	FIELD_VALUE = -1, /* field type stored in data.data.integer */
 	/*  0: const value (stored in data) */
diff --git a/src/core/store_expr.c b/src/core/store_expr.c
index d5b22c7..a0047a1 100644
--- a/src/core/store_expr.c
+++ b/src/core/store_expr.c
@@ -59,6 +59,8 @@ expr_init(sdb_object_t *obj, va_list ap)
 	if (type <= 0) {
 		if (! value)
 			return -1;
+		if ((type == TYPED_EXPR) && (! left))
+			return -1;
 	} else {
 		if (value)
 			return -1;
@@ -127,13 +129,28 @@ sdb_store_expr_create(int op, sdb_store_expr_t *left, sdb_store_expr_t *right)
 	return e;
 } /* sdb_store_expr_create */
 
+sdb_store_expr_t *
+sdb_store_expr_typed(int typ, sdb_store_expr_t *expr)
+{
+	sdb_data_t value = { SDB_TYPE_INTEGER, { .integer = typ } };
+	sdb_store_expr_t *e;
+
+	if ((typ < SDB_HOST) || (SDB_ATTRIBUTE < typ))
+		return NULL;
+
+	e = SDB_STORE_EXPR(sdb_object_create("store-typedexpr", expr_type,
+				TYPED_EXPR, expr, NULL, &value));
+	e->data_type = expr->data_type;
+	return e;
+} /* sdb_store_expr_typed */
+
 sdb_store_expr_t *
 sdb_store_expr_fieldvalue(int field)
 {
 	sdb_data_t value = { SDB_TYPE_INTEGER, { .integer = field } };
 	sdb_store_expr_t *e;
 
-	if ((field < 0) || (SDB_FIELD_BACKEND < field))
+	if ((field < SDB_FIELD_NAME) || (SDB_FIELD_BACKEND < field))
 		return NULL;
 	e = SDB_STORE_EXPR(sdb_object_create("store-fieldvalue", expr_type,
 				FIELD_VALUE, NULL, NULL, &value));
@@ -200,6 +217,18 @@ sdb_store_expr_eval(sdb_store_expr_t *expr, sdb_store_obj_t *obj,
 		}
 		return status;
 	}
+	else if (expr->type == TYPED_EXPR) {
+		int typ = (int)expr->data.data.integer;
+		if (typ != obj->type) {
+			/* we support self-references and { service, metric } -> host */
+			if ((typ != SDB_HOST)
+					|| ((obj->type != SDB_SERVICE)
+						&& (obj->type != SDB_METRIC)))
+				return -1;
+			obj = obj->parent;
+		}
+		return sdb_store_expr_eval(expr->left, obj, res, filter);
+	}
 
 	if (sdb_store_expr_eval(expr->left, obj, &v1, filter))
 		return -1;
diff --git a/src/include/core/store.h b/src/include/core/store.h
index d3862b4..5507436 100644
--- a/src/include/core/store.h
+++ b/src/include/core/store.h
@@ -332,6 +332,18 @@ sdb_store_get_attr(sdb_store_obj_t *obj, const char *name, sdb_data_t *res,
 sdb_store_expr_t *
 sdb_store_expr_create(int op, sdb_store_expr_t *left, sdb_store_expr_t *right);
 
+/*
+ * sdb_store_expr_typed:
+ * Creates an expression which evaluates in the context of an object's sibling
+ * as specified by the given type.
+ *
+ * Returns:
+ *  - an expression object on success
+ *  - NULL else
+ */
+sdb_store_expr_t *
+sdb_store_expr_typed(int typ, sdb_store_expr_t *expr);
+
 /*
  * sdb_store_expr_fieldvalue:
  * Creates an expression which evaluates to the value of the specified
-- 
2.30.2