Add an API to get TableInfo from ConstraintInfo through a lookup usin…

…g table_id

Code in P4 fuzzer uses ConstraintInfo to lookup TableInfo. Since p4fuzzer presubmit checks that any new code added to p4infra Github builds, we need to first sync this change to p4infra Github. This CL will enable these changes: https://critique.corp.google.com/cl/574299826. This is part of the work to support actions in P4-constraints by allowing users to add constraint annotations for actions. Please see the design doc at https://docs.google.com/document/d/11Nkn3_BAa43OX4I-_DPsoUokebGdRYx6QAk7eGVAyLc/edit?resourcekey=0-gO31LvkRyylb07KB1m3RMg for more information.

PUBLIC: [p4-fuzzer] Add ConstraintInfo API for retrieving TableInfo given table_id.
PiperOrigin-RevId: 574581354

p4_constraints/backend/constraint_info.cc

@@ -188,6 +188,13 @@ std::optional<AttributeInfo> GetAttributeInfo(
   return absl::nullopt;
 }
 
+const TableInfo* GetTableInfoOrNull(const ConstraintInfo& constraint_info,
+                                    uint32_t table_id) {
+  auto it = constraint_info.find(table_id);
+  if (it == constraint_info.end()) return nullptr;
+  return &it->second;
+}
+
 absl::StatusOr<ConstraintInfo> P4ToConstraintInfo(
     const p4::config::v1::P4Info& p4info) {
   // Allocate output.

p4_constraints/backend/constraint_info.h

@@ -83,6 +83,11 @@ using ConstraintInfo = absl::flat_hash_map<uint32_t, TableInfo>;
 absl::StatusOr<ConstraintInfo> P4ToConstraintInfo(
     const p4::config::v1::P4Info& p4info);
 
+// Returns a unique pointer to the TableInfo associated with a given table_id
+// or std::nullptr if the table_id cannot be found.
+const TableInfo* GetTableInfoOrNull(const ConstraintInfo& constraint_info,
+                                    uint32_t table_id);
+
 // Table entry attribute accessible in the constraint language, e.g. priority.
 struct AttributeInfo {
   std::string name;