add request2mask()

2020-01-29 13:41:45 -08:00
parent b54b9fb78d
commit 31412aff2e
4 changed files with 148 additions and 1 deletions
@@ -0,0 +1,75 @@
+/**
+ * Copyright - See the COPYRIGHT that is included with this distribution.
+ * pvxs is distributed subject to a Software License Agreement found
+ * in file LICENSE that is included with this distribution.
+ */
+
+#include "pvrequest.h"
+#include "dataimpl.h"
+
+namespace pvxs {
+namespace impl {
+
+BitMask request2mask(const FieldDesc* desc, const Value& pvRequest)
+{
+    auto fields = pvRequest["field"];
+    // pre-select top wildcard bit, which will always be permitted
+    BitMask ret({0u}, desc->size());
+    // have we found at least one requested field?
+    bool foundrequested = false;
+
+    if(fields.type()==TypeCode::Struct) {
+        auto rdesc = Value::Helper::desc(fields);
+
+        if(rdesc->mlookup.empty())
+            foundrequested = true; // empty is wildcard
+
+        // iterate pvRequest fields
+        for(auto& pair : rdesc->mlookup) {
+            auto crdesc = rdesc + pair.second;
+
+            if(crdesc->code==TypeCode::Struct) {
+                // attempt to match up with actual structure
+                auto it = desc->mlookup.find(pair.first);
+                if(it!=desc->mlookup.end()) {
+                    // match found
+                    auto cdesc = desc + it->second;
+
+                    ret[it->second] = true;
+                    foundrequested = true;
+
+                    if(crdesc->mlookup.empty() && cdesc->code==TypeCode::Struct) {
+                        // implicit select of all fields sub-struct
+
+                        for(auto& pair2 : cdesc->mlookup)
+                            ret[it->second + pair2.second] = true;
+                    }
+
+                } else {
+                    // request of non-existant field
+                }
+            }
+        }
+
+    } else if(!fields.valid()) {
+        foundrequested = true;
+
+    } else {
+        // .fields isn't a sub-struct
+    }
+
+    if(!foundrequested)
+        throw std::runtime_error("pvRequest selects no fields");
+
+    if(ret.findSet(1)==ret.size()) {
+        // empty mask is wildcard
+        for(auto bit : range(desc->size()))
+            ret[bit] = true;
+
+    }
+
+    return ret;
+}
+
+
+}} // namespace pvxs::impl