Represent bit fields as arrays

Author: kornilova203

bindgen/ir/Struct.cpp

@@ -8,10 +8,12 @@
 Field::Field(std::string name, std::shared_ptr<Type> type)
     : TypeAndName(std::move(name), std::move(type)) {}
 
-Field::Field(std::string name, std::shared_ptr<Type> type, uint64_t offset)
-    : TypeAndName(std::move(name), std::move(type)), offset(offset) {}
+Field::Field(std::string name, std::shared_ptr<Type> type,
+             uint64_t offsetInBits)
+    : TypeAndName(std::move(name), std::move(type)),
+      offsetInBits(offsetInBits) {}
 
-uint64_t Field::getOffset() const { return offset; }
+uint64_t Field::getOffsetInBits() const { return offsetInBits; }
 
 StructOrUnion::StructOrUnion(std::string name,
                              std::vector<std::shared_ptr<Field>> fields,
@@ -34,7 +36,7 @@ Struct::Struct(std::string name, std::vector<std::shared_ptr<Field>> fields,
       typeSize(typeSize), isPacked(isPacked) {}
 
 std::shared_ptr<TypeDef> Struct::generateTypeDef() {
-    if (fields.size() < SCALA_NATIVE_MAX_STRUCT_FIELDS) {
+    if (isRepresentedAsStruct()) {
         return std::make_shared<TypeDef>(getTypeAlias(), shared_from_this(),
                                          nullptr);
     } else {
@@ -56,7 +58,7 @@ std::string Struct::generateHelperClass() const {
     s << "  implicit class " << type << "_ops(val p: native.Ptr[" << type
       << "])"
       << " extends AnyVal {\n";
-    if (fields.size() <= SCALA_NATIVE_MAX_STRUCT_FIELDS) {
+    if (isRepresentedAsStruct()) {
         s << generateHelperClassMethodsForStructRepresentation();
     } else {
         s << generateHelperClassMethodsForArrayRepresentation();
@@ -72,6 +74,9 @@ std::string Struct::generateHelperClass() const {
 }
 
 bool Struct::hasHelperMethods() const {
+    if (isBitField()) {
+        return false;
+    }
     if (!isRepresentedAsStruct()) {
         return !fields.empty();
     }
@@ -176,7 +181,7 @@ Struct::generateGetterForStructRepresentation(unsigned fieldIndex) const {
 }
 
 bool Struct::isRepresentedAsStruct() const {
-    return fields.size() <= SCALA_NATIVE_MAX_STRUCT_FIELDS;
+    return fields.size() <= SCALA_NATIVE_MAX_STRUCT_FIELDS && !isBitField();
 }
 
 std::string
@@ -188,9 +193,10 @@ Struct::generateSetterForArrayRepresentation(unsigned int fieldIndex) const {
     std::string castedField = "p._1";
 
     PointerType pointerToFieldType = PointerType(field->getType());
-    if (field->getOffset() > 0) {
-        castedField = "(" + castedField + " + " +
-                      std::to_string(field->getOffset()) + ")";
+    uint64_t offsetInBytes = field->getOffsetInBits() / 8;
+    if (offsetInBytes > 0) {
+        castedField =
+            "(" + castedField + " + " + std::to_string(offsetInBytes) + ")";
     }
     castedField = "!" + castedField + ".cast[" + pointerToFieldType.str() + "]";
     if (isAliasForType<ArrayType>(field->getType().get()) ||
@@ -215,8 +221,9 @@ Struct::generateGetterForArrayRepresentation(unsigned fieldIndex) const {
     std::string methodBody;
 
     PointerType pointerToFieldType = PointerType(field->getType());
-    if (field->getOffset() > 0) {
-        methodBody = "(p._1 + " + std::to_string(field->getOffset()) + ")";
+    uint64_t offsetInBytes = field->getOffsetInBits() / 8;
+    if (offsetInBytes > 0) {
+        methodBody = "(p._1 + " + std::to_string(offsetInBytes) + ")";
     } else {
         methodBody = "p._1";
     }
@@ -233,7 +240,16 @@ Struct::generateGetterForArrayRepresentation(unsigned fieldIndex) const {
     s << "    def " << getter << ": " << returnType << " = " << methodBody
       << "\n";
     return s.str();
-    return "";
+}
+
+bool Struct::isBitField() const {
+    // TODO: find proper way to check it
+    for (const auto &field : fields) {
+        if (field->getOffsetInBits() % 8 != 0) {
+            return true;
+        }
+    }
+    return false;
 }
 
 Union::Union(std::string name, std::vector<std::shared_ptr<Field>> fields,

bindgen/ir/Struct.h

@@ -13,15 +13,15 @@ class Field : public TypeAndName {
   public:
     Field(std::string name, std::shared_ptr<Type> type);
 
-    Field(std::string name, std::shared_ptr<Type> type, uint64_t offset);
+    Field(std::string name, std::shared_ptr<Type> type, uint64_t offsetInBits);
 
-    uint64_t getOffset() const;
+    uint64_t getOffsetInBits() const;
 
   protected:
     /**
      * Offset in bytes from address of struct/union.
      */
-    uint64_t offset = 0;
+    uint64_t offsetInBits = 0;
 };
 
 class StructOrUnion {
@@ -99,6 +99,8 @@ class Struct : public StructOrUnion,
     std::string generateSetterForArrayRepresentation(unsigned fieldIndex) const;
 
     std::string generateGetterForArrayRepresentation(unsigned fieldIndex) const;
+
+    bool isBitField() const;
 };
 
 class Union : public StructOrUnion,

bindgen/visitor/TreeVisitor.cpp

@@ -135,9 +135,8 @@ void TreeVisitor::handleStruct(clang::RecordDecl *record, std::string name) {
             typeTranslator.translate(field->getType(), &name);
         uint64_t recordOffsetInBits =
             recordLayout.getFieldOffset(field->getFieldIndex());
-        assert(recordOffsetInBits % 8 == 0);
-        fields.push_back(std::make_shared<Field>(
-            field->getNameAsString(), ftype, recordOffsetInBits / 8));
+        fields.push_back(std::make_shared<Field>(field->getNameAsString(),
+                                                 ftype, recordOffsetInBits));
 
         cycleDetection.AddDependency(newName, field->getType());
     }

tests/samples/Struct.h

@@ -60,6 +60,13 @@ struct __attribute__((__packed__)) packedStruct { // no helper methods
     char a;
 };
 
+struct bitFieldStruct { // no helper methods
+    unsigned char b1 : 3;
+    unsigned char : 0; // start a new byte
+    unsigned char b2 : 6;
+    unsigned char b3 : 2;
+};
+
 char getCharFromAnonymousStruct(struct structWithAnonymousStruct *s);
 
 char getIntFromAnonymousStruct(struct structWithAnonymousStruct *s);

tests/samples/Struct.scala

@@ -14,6 +14,7 @@ object Struct {
   type struct_bigStruct = native.CArray[Byte, native.Nat.Digit[native.Nat._1, native.Nat.Digit[native.Nat._1, native.Nat._2]]]
   type struct_structWithAnonymousStruct = native.CStruct2[native.CInt, native.CArray[Byte, native.Nat._8]]
   type struct_packedStruct = native.CStruct1[native.CChar]
+  type struct_bitFieldStruct = native.CArray[Byte, native.Nat._2]
   type enum_struct_op = native.CUnsignedInt
   def setPoints(points: native.Ptr[struct_points], x1: native.CInt, y1: native.CInt, x2: native.CInt, y2: native.CInt): Unit = native.extern
   def getPoint(points: native.Ptr[struct_points], pointIndex: enum_pointIndex): native.CInt = native.extern