From 45e0ded5cd688d00bd39feace0720cba4e63a298 Mon Sep 17 00:00:00 2001
From: Philippe Proulx <eeppeliteloop@gmail.com>
Date: Thu, 19 May 2022 21:50:36 -0400
Subject: [PATCH] Add bt2::Common{Field,FieldClass,Value,Message}<>::as<>()

Those new as() method templates conceptually cast their object to the
first template parameter. Those are shorthands to use specific types
within a template function, for example:

    template <typename FieldT, typename ValT>
    void g(bt2::Field field, const ValT val)
    {
        // ...
        field.as<FieldT>() = val;
        // ...
    }

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Change-Id: Ifc1f49487ac6ef9c143bf4c2faa3373f4eaccd9e
Reviewed-on: https://review.lttng.org/c/babeltrace/+/8099
Reviewed-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/10803
Tested-by: jenkins <jenkins@lttng.org>
---
 src/cpp-common/bt2/field-class.hpp | 6 ++++++
 src/cpp-common/bt2/field.hpp       | 6 ++++++
 src/cpp-common/bt2/message.hpp     | 6 ++++++
 src/cpp-common/bt2/value.hpp       | 6 ++++++
 4 files changed, 24 insertions(+)

diff --git a/src/cpp-common/bt2/field-class.hpp b/src/cpp-common/bt2/field-class.hpp
index 2a167b19..b630224f 100644
--- a/src/cpp-common/bt2/field-class.hpp
+++ b/src/cpp-common/bt2/field-class.hpp
@@ -373,6 +373,12 @@ public:
         return this->_libTypeIs(BT_FIELD_CLASS_TYPE_VARIANT_WITH_SIGNED_INTEGER_SELECTOR_FIELD);
     }
 
+    template <typename FieldClassT>
+    FieldClassT as() const noexcept
+    {
+        return FieldClassT {this->libObjPtr()};
+    }
+
     CommonBitArrayFieldClass<LibObjT> asBitArray() const noexcept;
     CommonIntegerFieldClass<LibObjT> asInteger() const noexcept;
     CommonBaseEnumerationFieldClass<LibObjT> asEnumeration() const noexcept;
diff --git a/src/cpp-common/bt2/field.hpp b/src/cpp-common/bt2/field.hpp
index 25d0034f..f1908b99 100644
--- a/src/cpp-common/bt2/field.hpp
+++ b/src/cpp-common/bt2/field.hpp
@@ -204,6 +204,12 @@ public:
         return this->cls().isVariant();
     }
 
+    template <typename FieldT>
+    FieldT as() const noexcept
+    {
+        return FieldT {this->libObjPtr()};
+    }
+
     CommonBoolField<LibObjT> asBool() const noexcept;
     CommonBitArrayField<LibObjT> asBitArray() const noexcept;
     CommonUnsignedIntegerField<LibObjT> asUnsignedInteger() const noexcept;
diff --git a/src/cpp-common/bt2/message.hpp b/src/cpp-common/bt2/message.hpp
index cc0f20ea..bc83c4b2 100644
--- a/src/cpp-common/bt2/message.hpp
+++ b/src/cpp-common/bt2/message.hpp
@@ -157,6 +157,12 @@ public:
         return Shared::createWithRef(*this);
     }
 
+    template <typename MessageT>
+    MessageT as() const noexcept
+    {
+        return MessageT {this->libObjPtr()};
+    }
+
     CommonStreamBeginningMessage<LibObjT> asStreamBeginning() const noexcept;
     CommonStreamEndMessage<LibObjT> asStreamEnd() const noexcept;
     CommonEventMessage<LibObjT> asEvent() const noexcept;
diff --git a/src/cpp-common/bt2/value.hpp b/src/cpp-common/bt2/value.hpp
index 5f265236..a065af6c 100644
--- a/src/cpp-common/bt2/value.hpp
+++ b/src/cpp-common/bt2/value.hpp
@@ -212,6 +212,12 @@ public:
         return Shared::createWithRef(*this);
     }
 
+    template <typename ValueT>
+    ValueT as() const noexcept
+    {
+        return ValueT {this->libObjPtr()};
+    }
+
     CommonNullValue<LibObjT> asNull() const noexcept;
     CommonBoolValue<LibObjT> asBool() const noexcept;
     CommonSignedIntegerValue<LibObjT> asSignedInteger() const noexcept;
-- 
2.34.1