Implement inline structs.

c++/src/capnproto/layout.c++

@@ -415,7 +415,7 @@ struct WireHelpers {
     ref->structRef.set(size);
 
     // Build the StructBuilder.
-    return StructBuilder(segment, ptr, reinterpret_cast<WireReference*>(ptr + size.data));
+    return StructBuilder(segment, ptr, reinterpret_cast<WireReference*>(ptr + size.data), 0 * BITS);
   }
 
   static CAPNPROTO_ALWAYS_INLINE(StructBuilder getWritableStructReference(
@@ -442,7 +442,7 @@ struct WireHelpers {
           "Trying to update struct with incorrect reference count.");
     }
 
-    return StructBuilder(segment, ptr, reinterpret_cast<WireReference*>(ptr + size.data));
+    return StructBuilder(segment, ptr, reinterpret_cast<WireReference*>(ptr + size.data), 0 * BITS);
   }
 
   static CAPNPROTO_ALWAYS_INLINE(ListBuilder initListReference(
@@ -603,7 +603,7 @@ struct WireHelpers {
     if (ref == nullptr || ref->isNull()) {
     useDefault:
       if (defaultValue == nullptr) {
-        return StructReader(nullptr, nullptr, nullptr, 0 * WORDS, 0 * REFERENCES, 0 * BITS,
+        return StructReader(nullptr, nullptr, nullptr, 0 * BITS, 0 * REFERENCES, 0 * BITS,
                             std::numeric_limits<int>::max());
       }
       segment = nullptr;
@@ -637,7 +637,7 @@ struct WireHelpers {
 
     return StructReader(
         segment, ptr, reinterpret_cast<const WireReference*>(ptr + ref->structRef.dataSize.get()),
-        ref->structRef.dataSize.get(),
+        ref->structRef.dataSize.get() * BITS_PER_WORD,
         ref->structRef.refCount.get(),
         0 * BITS, nestingLimit - 1);
   }
@@ -752,7 +752,8 @@ struct WireHelpers {
       }
 
       return ListReader(segment, ptr, size, wordsPerElement * BITS_PER_WORD,
-          tag->structRef.dataSize.get(), tag->structRef.refCount.get(), nestingLimit - 1);
+          tag->structRef.dataSize.get() * BITS_PER_WORD,
+          tag->structRef.refCount.get(), nestingLimit - 1);
 
     } else {
       // The elements of the list are NOT structs.
@@ -774,28 +775,17 @@ struct WireHelpers {
         // old version of the protocol.  We need to verify that the struct's first field matches
         // what the sender sent us.
 
-        WordCount dataSize;
-        WireReferenceCount referenceCount;
+        BitCount dataSize = 0 * BITS;
+        WireReferenceCount referenceCount = 0 * REFERENCES;
 
         switch (ref->listRef.elementSize()) {
-          case FieldSize::VOID:
-            dataSize = 0 * WORDS;
-            referenceCount = 0 * REFERENCES;
-            break;
-
-          case FieldSize::BIT:
-          case FieldSize::BYTE:
-          case FieldSize::TWO_BYTES:
-          case FieldSize::FOUR_BYTES:
-          case FieldSize::EIGHT_BYTES:
-            dataSize = 1 * WORDS;
-            referenceCount = 0 * REFERENCES;
-            break;
-
-          case FieldSize::REFERENCE:
-            dataSize = 0 * WORDS;
-            referenceCount = 1 * REFERENCES;
-            break;
+          case FieldSize::VOID: break;
+          case FieldSize::BIT: dataSize = 1 * BITS; break;
+          case FieldSize::BYTE: dataSize = 8 * BITS; break;
+          case FieldSize::TWO_BYTES: dataSize = 16 * BITS; break;
+          case FieldSize::FOUR_BYTES: dataSize = 32 * BITS; break;
+          case FieldSize::EIGHT_BYTES: dataSize = 64 * BITS; break;
+          case FieldSize::REFERENCE: referenceCount = 1 * REFERENCES; break;
 
           case FieldSize::INLINE_COMPOSITE:
             FAIL_CHECK();
@@ -978,7 +968,7 @@ StructReader StructBuilder::asReader() const {
   static_assert(sizeof(WireReference::structRef.refCount) == 2,
       "Has the maximum reference count changed?");
   return StructReader(segment, data, references,
-      0xffff * WORDS, 0xffff * REFERENCES, 0 * BITS, std::numeric_limits<int>::max());
+      0xffffffff * BITS, 0xffff * REFERENCES, 0 * BITS, std::numeric_limits<int>::max());
 }
 
 StructReader StructReader::readRootTrusted(const word* location) {
@@ -998,7 +988,7 @@ StructReader StructReader::readRoot(
 }
 
 StructReader StructReader::readEmpty() {
-  return StructReader(nullptr, nullptr, nullptr, 0 * WORDS, 0 * REFERENCES, 0 * BITS,
+  return StructReader(nullptr, nullptr, nullptr, 0 * BITS, 0 * REFERENCES, 0 * BITS,
                       std::numeric_limits<int>::max());
 }
 
@@ -1031,7 +1021,7 @@ StructBuilder ListBuilder::getStructElement(
     ElementCount index, decltype(WORDS/ELEMENTS) elementSize, WordCount structDataSize) const {
   word* structPtr = ptr + elementSize * index;
   return StructBuilder(segment, structPtr,
-      reinterpret_cast<WireReference*>(structPtr + structDataSize));
+      reinterpret_cast<WireReference*>(structPtr + structDataSize), 0 * BITS);
 }
 
 ListBuilder ListBuilder::initListElement(
@@ -1087,9 +1077,9 @@ ListReader ListBuilder::asReader(FieldSize elementSize) const {
                     std::numeric_limits<int>::max());
 }
 
-ListReader ListBuilder::asReader(WordCount dataSize, WireReferenceCount referenceCount) const {
+ListReader ListBuilder::asReader(BitCount dataSize, WireReferenceCount referenceCount) const {
   return ListReader(segment, ptr, elementCount,
-      (dataSize + referenceCount * WORDS_PER_REFERENCE) * BITS_PER_WORD / ELEMENTS,
+      (dataSize + referenceCount * WORDS_PER_REFERENCE * BITS_PER_WORD) / ELEMENTS,
       dataSize, referenceCount, std::numeric_limits<int>::max());
 }
 
@@ -1103,7 +1093,7 @@ StructReader ListReader::getStructElement(ElementCount index) const {
   const byte* structPtr = reinterpret_cast<const byte*>(ptr) + indexBit / BITS_PER_BYTE;
   return StructReader(
       segment, structPtr,
-      reinterpret_cast<const WireReference*>(structPtr + structDataSize * BYTES_PER_WORD),
+      reinterpret_cast<const WireReference*>(structPtr + structDataSize / BITS_PER_BYTE),
       structDataSize, structReferenceCount, indexBit % BITS_PER_BYTE, nestingLimit - 1);
 }
 

c++/src/capnproto/test-util.h

@@ -57,6 +57,9 @@ using ::capnproto::test::TestUnion;
 using ::capnproto::test::TestUnionDefaults;
 using ::capnproto::test::TestNestedTypes;
 using ::capnproto::test::TestUsing;
+using ::capnproto::test::TestInlineLayout;
+using ::capnproto::test::TestInlineUnions;
+using ::capnproto::test::TestInlineDefaults;
 
 void initTestMessage(test::TestAllTypes::Builder builder);
 void initTestMessage(test::TestDefaults::Builder builder);

c++/src/capnproto/test.capnp

@@ -213,7 +213,6 @@ struct TestUnion {
   bit5 @42: Bool;
   bit6 @43: Bool;
   bit7 @44: Bool;
-  byte0 @49: UInt8;
 
   # Interleave two unions to be really annoying.
   # Also declare in reverse order to make sure union discriminant values are sorted by field number
@@ -233,6 +232,8 @@ struct TestUnion {
     u3f0s8 @48: Int8;
     u3f0s1 @46: Bool;
   }
+
+  byte0 @49: UInt8;
 }
 
 struct TestUnionDefaults {
@@ -274,3 +275,140 @@ struct TestUsing {
   outerNestedEnum @1 :OuterNestedEnum = bar;
   innerNestedEnum @0 :NestedEnum = quux;
 }
+
+struct TestInline0 fixed(0 bits) {}
+struct TestInline1 fixed(1 bits) { f @0: Bool; }
+struct TestInline8 fixed(8 bits) { f0 @0: Bool; f1 @1: Bool; f2 @2: Bool; }
+struct TestInline16 fixed(16 bits) { f0 @0: UInt8; f1 @1: UInt8; }
+struct TestInline32 fixed(32 bits) { f0 @0: UInt8; f1 @1: UInt16; }
+struct TestInline64 fixed(64 bits) { f0 @0: UInt8; f1 @1: UInt32; }
+struct TestInline128 fixed(2 words) { f0 @0: UInt64; f1 @1: UInt64; }
+struct TestInline192 fixed(3 words) { f0 @0: UInt64; f1 @1: UInt64; f2 @2: UInt64; }
+
+struct TestInline0p fixed(0 bits, 1 pointers) { f @0 :Inline(TestInline0); p0 @1 :Text; }
+struct TestInline1p fixed(1 bits, 1 pointers) { f @0 :Inline(TestInline1); p0 @1 :Text; }
+struct TestInline8p fixed(8 bits, 1 pointers) { f @0 :Inline(TestInline8); p0 @1 :Text; }
+struct TestInline16p fixed(16 bits, 2 pointers) { f @0 :Inline(TestInline16); p0 @1 :Text; p1 @2 :Text; }
+struct TestInline32p fixed(32 bits, 2 pointers) { f @0 :Inline(TestInline32); p0 @1 :Text; p1 @2 :Text; }
+struct TestInline64p fixed(64 bits, 2 pointers) { f @0 :Inline(TestInline64); p0 @1 :Text; p1 @2 :Text; }
+struct TestInline128p fixed(2 words, 3 pointers) { f @0 :Inline(TestInline128); p0 @1 :Text; p1 @2 :Text; p2 @3 :Text; }
+struct TestInline192p fixed(3 words, 3 pointers) { f @0 :Inline(TestInline192); p0 @1 :Text; p1 @2 :Text; p2 @3 :Text; }
+
+struct TestInlineLayout {
+  f0 @0 :Inline(TestInline0);
+  f1 @1 :Inline(TestInline1);
+  f8 @2 :Inline(TestInline8);
+  f16 @3 :Inline(TestInline16);
+  f32 @4 :Inline(TestInline32);
+  f64 @5 :Inline(TestInline64);
+  f128 @6 :Inline(TestInline128);
+  f192 @7 :Inline(TestInline192);
+
+  f0p @8 :Inline(TestInline0p);
+  f1p @9 :Inline(TestInline1p);
+  f8p @10 :Inline(TestInline8p);
+  f16p @11 :Inline(TestInline16p);
+  f32p @12 :Inline(TestInline32p);
+  f64p @13 :Inline(TestInline64p);
+  f128p @14 :Inline(TestInline128p);
+  f192p @15 :Inline(TestInline192p);
+
+  f1Offset @16 :Inline(TestInline1);
+  bit @17 :Bool;
+}
+
+struct TestInlineUnions {
+  union0 @0 union {
+    f0 @4 :Inline(TestInline0);
+    f1 @5 :Inline(TestInline1);
+    f8 @6 :Inline(TestInline8);
+    f16 @7 :Inline(TestInline16);
+    f32 @8 :Inline(TestInline32);
+    f64 @9 :Inline(TestInline64);
+    f128 @10 :Inline(TestInline128);
+    f192 @11 :Inline(TestInline192);
+
+    f0p @12 :Inline(TestInline0p);
+    f1p @13 :Inline(TestInline1p);
+    f8p @14 :Inline(TestInline8p);
+    f16p @15 :Inline(TestInline16p);
+    f32p @16 :Inline(TestInline32p);
+    f64p @17 :Inline(TestInline64p);
+    f128p @18 :Inline(TestInline128p);
+    f192p @19 :Inline(TestInline192p);
+  }
+
+  # Pack one bit in order to make pathological situation for union1.
+  bit0 @20: Bool;
+
+  union1 @1 union {
+    f0 @21 :Inline(TestInline0);
+    f1 @22 :Inline(TestInline1);
+    f8 @23 :Inline(TestInline8);
+    f16 @24 :Inline(TestInline16);
+    f32 @25 :Inline(TestInline32);
+    f64 @26 :Inline(TestInline64);
+    f128 @27 :Inline(TestInline128);
+    f192 @28 :Inline(TestInline192);
+  }
+
+  # Fill in the rest of that bitfield from earlier.
+  bit2 @29: Bool;
+  bit3 @30: Bool;
+  bit4 @31: Bool;
+  bit5 @32: Bool;
+  bit6 @33: Bool;
+  bit7 @34: Bool;
+
+  # Interleave two unions to be really annoying.
+  union2 @2 union {
+    f1p @35 :Inline(TestInline1p);
+    f8p @37 :Inline(TestInline8p);
+    f16p @40 :Inline(TestInline16p);
+    f32p @42 :Inline(TestInline32p);
+    f64p @44 :Inline(TestInline64p);
+    f128p @46 :Inline(TestInline128p);
+    f192p @48 :Inline(TestInline192p);
+  }
+
+  union3 @3 union {
+    f1p @36 :Inline(TestInline1p);
+    f8p @38 :Inline(TestInline8p);
+    f16p @41 :Inline(TestInline16p);
+    f32p @43 :Inline(TestInline32p);
+    f64p @45 :Inline(TestInline64p);
+    f128p @47 :Inline(TestInline128p);
+    f192p @49 :Inline(TestInline192p);
+  }
+
+  byte0 @39: UInt8;
+}
+
+struct TestInlineDefaults {
+  normal @0 :TestInlineLayout = (
+      f0 = (),
+      f1 = (f = true),
+      f8 = (f0 = true, f1 = false, f2 = true),
+      f16 = (f0 = 123, f1 = 45),
+      f32 = (f0 = 67, f1 = 8901),
+      f64 = (f0 = 234, f1 = 567890123),
+      f128 = (f0 = 1234567890123, f1 = 4567890123456),
+      f192 = (f0 = 7890123456789, f1 = 2345678901234, f2 = 5678901234567),
+
+      f0p = (p0 = "foo"),
+      f1p = (f = (f = false), p0 = "bar"),
+      f8p = (f = (f0 = true, f1 = true, f2 = false), p0 = "baz"),
+      f16p = (f = (f0 = 98, f1 = 76), p0 = "qux", p1 = "quux"),
+      f32p = (f = (f0 = 54, f1 = 32109), p0 = "corge", p1 = "grault"),
+      f64p = (f = (f0 = 87, f1 = 654321098), p0 = "garply", p1 = "waldo"),
+      f128p = (f = (f0 = 7654321098765, f1 = 4321098765432),
+               p0 = "fred", p1 = "plugh", p2 = "xyzzy"),
+      f192p = (f = (f0 = 1098765432109, f1 = 8765432109876, f2 = 5432109876543),
+               p0 = "thud", p1 = "foobar", p2 = "barbaz"));
+
+  unions @1 :TestInlineUnions = (
+      union0 = f32(f0 = 67, f1 = 8901),
+      union1 = f128(f0 = 1234567890123, f1 = 4567890123456),
+      union2 = f1p(p0 = "foo"),
+      union3 = f16p(f = (f0 = 98, f1 = 76), p0 = "qux", p1 = "quux"));
+}

c++/src/capnproto/type-safety.h

@@ -651,6 +651,11 @@ inline constexpr decltype(BYTES / ELEMENTS) bytesPerElement() {
   return sizeof(T) * BYTES / ELEMENTS;
 }
 
+template <typename T>
+inline constexpr decltype(BITS / ELEMENTS) bitsPerElement() {
+  return sizeof(T) * 8 * BITS / ELEMENTS;
+}
+
 #ifndef __CDT_PARSER__
 
 template <typename T, typename U>

compiler/capnproto-compiler.cabal

@@ -4,6 +4,13 @@ cabal-version:  >=1.2
 build-type:     Simple
 author:         kenton
 
+-- How to get stack traces:
+-- 1. Compile normally and do not clean.
+-- 2. Add "-prof -fprof-auto -osuf .prof.o" to ghc-options and compile again.
+--    (TODO:  Figure out how to add these through "cabal configure" instead of by editing
+--    this file.  --enable-executable-profiling alone doesn't appear to get the job done.)
+-- 3. Run with +RTS -xc -RTS on the command line.
+
 executable capnpc
   hs-source-dirs:  src
   main-is:         Main.hs

compiler/src/CxxGenerator.hs

@@ -88,6 +88,7 @@ hashString str =
 isPrimitive t@(BuiltinType _) = not $ isBlob t
 isPrimitive (EnumType _) = True
 isPrimitive (StructType _) = False
+isPrimitive (InlineStructType _) = False
 isPrimitive (InterfaceType _) = False
 isPrimitive (ListType _) = False
 
@@ -96,8 +97,12 @@ isBlob (BuiltinType BuiltinData) = True
 isBlob _ = False
 
 isStruct (StructType _) = True
+isStruct (InlineStructType _) = True
 isStruct _ = False
 
+isInlineStruct (InlineStructType _) = True
+isInlineStruct _ = False
+
 isList (ListType _) = True
 isList _ = False
 
@@ -130,18 +135,30 @@ cxxTypeString (BuiltinType BuiltinText) = " ::capnproto::Text"
 cxxTypeString (BuiltinType BuiltinData) = " ::capnproto::Data"
 cxxTypeString (EnumType desc) = globalName $ DescEnum desc
 cxxTypeString (StructType desc) = globalName $ DescStruct desc
+cxxTypeString (InlineStructType desc) = globalName $ DescStruct desc
 cxxTypeString (InterfaceType desc) = globalName $ DescInterface desc
 cxxTypeString (ListType t) = concat [" ::capnproto::List<", cxxTypeString t, ">"]
 
-cxxFieldSizeString Size0 = "VOID";
-cxxFieldSizeString Size1 = "BIT";
-cxxFieldSizeString Size8 = "BYTE";
-cxxFieldSizeString Size16 = "TWO_BYTES";
-cxxFieldSizeString Size32 = "FOUR_BYTES";
-cxxFieldSizeString Size64 = "EIGHT_BYTES";
+cxxFieldSizeString SizeVoid = "VOID";
+cxxFieldSizeString (SizeData Size1) = "BIT";
+cxxFieldSizeString (SizeData Size8) = "BYTE";
+cxxFieldSizeString (SizeData Size16) = "TWO_BYTES";
+cxxFieldSizeString (SizeData Size32) = "FOUR_BYTES";
+cxxFieldSizeString (SizeData Size64) = "EIGHT_BYTES";
 cxxFieldSizeString SizeReference = "REFERENCE";
 cxxFieldSizeString (SizeInlineComposite _ _) = "INLINE_COMPOSITE";
 
+fieldOffsetInteger VoidOffset = "0"
+fieldOffsetInteger (DataOffset _ o) = show o
+fieldOffsetInteger (PointerOffset o) = show o
+fieldOffsetInteger (InlineCompositeOffset d p ds ps) = let
+    bitSize = dataSectionBits ds
+    bitOffset = case ds of
+        DataSectionWords _ -> d * 64
+        _ -> d * bitSize
+    in printf "%d * ::capnproto::BITS, %d * ::capnproto::BITS, \
+              \%d * ::capnproto::REFERENCES, %d * ::capnproto::REFERENCES" bitOffset bitSize p ps
+
 isDefaultZero VoidDesc = True
 isDefaultZero (BoolDesc    b) = not b
 isDefaultZero (Int8Desc    i) = i == 0
@@ -221,6 +238,7 @@ fieldContext parent desc = mkStrContext context where
     context "fieldIsPrimitive" = MuBool $ isPrimitive $ fieldType desc
     context "fieldIsBlob" = MuBool $ isBlob $ fieldType desc
     context "fieldIsStruct" = MuBool $ isStruct $ fieldType desc
+    context "fieldIsInlineStruct" = MuBool $ isInlineStruct $ fieldType desc
     context "fieldIsList" = MuBool $ isList $ fieldType desc
     context "fieldIsNonStructList" = MuBool $ isNonStructList $ fieldType desc
     context "fieldIsPrimitiveList" = MuBool $ isPrimitiveList $ fieldType desc
@@ -231,7 +249,7 @@ fieldContext parent desc = mkStrContext context where
             Nothing -> muNull
     context "fieldType" = MuVariable $ cxxTypeString $ fieldType desc
     context "fieldBlobType" = MuVariable $ blobTypeString $ fieldType desc
-    context "fieldOffset" = MuVariable $ fieldOffset desc
+    context "fieldOffset" = MuVariable $ fieldOffsetInteger $ fieldOffset desc
     context "fieldDefaultMask" = case fieldDefaultValue desc of
         Nothing -> MuVariable ""
         Just v -> MuVariable (if isDefaultZero v then "" else ", " ++ defaultMask v)
@@ -283,8 +301,8 @@ structContext parent desc = mkStrContext context where
     context "structFullName" = MuVariable $ fullName (DescStruct desc)
     context "structFields" = MuList $ map (fieldContext context) $ structFields desc
     context "structUnions" = MuList $ map (unionContext context) $ structUnions desc
-    context "structDataSize" = MuVariable $ packingDataSize $ structPacking desc
-    context "structReferenceCount" = MuVariable $ packingReferenceCount $ structPacking desc
+    context "structDataSize" = MuVariable $ dataSectionWordSize $ structDataSize desc
+    context "structReferenceCount" = MuVariable $ structPointerCount desc
     context "structNestedEnums" =
         MuList $ map (enumContext context) [m | DescEnum m <- structMembers desc]
     context "structNestedStructs" =

compiler/src/Grammar.hs

@@ -95,7 +95,8 @@ data Declaration = UsingDecl (Located String) DeclName
                  | ConstantDecl (Located String) TypeExpression [Annotation] (Located FieldValue)
                  | EnumDecl (Located String) [Annotation] [Declaration]
                  | EnumerantDecl (Located String) (Located Integer) [Annotation]
-                 | StructDecl (Located String) [Annotation] [Declaration]
+                 | StructDecl (Located String) (Maybe (Located (Integer, Integer)))
+                              [Annotation] [Declaration]
                  | FieldDecl (Located String) (Located Integer)
                              TypeExpression [Annotation] (Maybe (Located FieldValue))
                  | UnionDecl (Located String) (Located Integer) [Annotation] [Declaration]
@@ -110,7 +111,7 @@ declarationName (UsingDecl n _)          = Just n
 declarationName (ConstantDecl n _ _ _)   = Just n
 declarationName (EnumDecl n _ _)         = Just n
 declarationName (EnumerantDecl n _ _)    = Just n
-declarationName (StructDecl n _ _)       = Just n
+declarationName (StructDecl n _ _ _)     = Just n
 declarationName (FieldDecl n _ _ _ _)    = Just n
 declarationName (UnionDecl n _ _ _)      = Just n
 declarationName (InterfaceDecl n _ _)    = Just n
@@ -122,7 +123,7 @@ declImports (UsingDecl _ name) = maybeToList (declNameImport name)
 declImports (ConstantDecl _ t ann _) = typeImports t ++ concatMap annotationImports ann
 declImports (EnumDecl _ ann decls) = concatMap annotationImports ann ++ concatMap declImports decls
 declImports (EnumerantDecl _ _ ann) = concatMap annotationImports ann
-declImports (StructDecl _ ann decls) = concatMap annotationImports ann ++
+declImports (StructDecl _ _ ann decls) = concatMap annotationImports ann ++
                                          concatMap declImports decls
 declImports (FieldDecl _ _ t ann _) = typeImports t ++ concatMap annotationImports ann
 declImports (UnionDecl _ _ ann decls) = concatMap annotationImports ann ++

compiler/src/Lexer.hs

@@ -49,6 +49,7 @@ keywords =
     , (UnionKeyword, "union")
     , (InterfaceKeyword, "interface")
     , (AnnotationKeyword, "annotation")
+    , (FixedKeyword, "fixed")
     ]
 
 languageDef :: T.LanguageDef st

compiler/src/Parser.hs

@@ -24,6 +24,7 @@
 module Parser (parseFile) where
 
 import Data.Generics
+import Data.Maybe(fromMaybe)
 import Text.Parsec hiding (tokens)
 import Token
 import Grammar
@@ -65,6 +66,7 @@ tokenErrorString StructKeyword = "keyword \"struct\""
 tokenErrorString UnionKeyword = "keyword \"union\""
 tokenErrorString InterfaceKeyword = "keyword \"interface\""
 tokenErrorString AnnotationKeyword = "keyword \"annotation\""
+tokenErrorString FixedKeyword = "keyword \"fixed\""
 
 type TokenParser = Parsec [Located Token] [ParseError]
 
@@ -120,6 +122,7 @@ structKeyword = tokenParser (matchSimpleToken StructKeyword) <?> "\"struct\""
 unionKeyword = tokenParser (matchSimpleToken UnionKeyword) <?> "\"union\""
 interfaceKeyword = tokenParser (matchSimpleToken InterfaceKeyword) <?> "\"interface\""
 annotationKeyword = tokenParser (matchSimpleToken AnnotationKeyword) <?> "\"annotation\""
+fixedKeyword = tokenParser (matchSimpleToken FixedKeyword) <?> "\"fixed\""
 
 exactIdentifier s = tokenParser (matchSimpleToken $ Identifier s) <?> "\"" ++ s ++ "\""
 
@@ -223,9 +226,39 @@ enumerantDecl = do
 structDecl statements = do
     structKeyword
     name <- located typeIdentifier
+    fixed <- optionMaybe fixedSpec
     annotations <- many annotation
     children <- parseBlock structLine statements
-    return (StructDecl name annotations children)
+    return (StructDecl name fixed annotations children)
+
+fixedSpec = do
+    fixedKeyword
+    Located pos sizes <- located $ parenthesizedList fixedSize
+    (dataSize, pointerSize) <- foldM combineFixedSizes (Nothing, Nothing) sizes
+    return $ Located pos (fromMaybe 0 dataSize, fromMaybe 0 pointerSize)
+
+data FixedSize = FixedData Integer | FixedPointers Integer
+
+combineFixedSizes :: (Maybe Integer, Maybe Integer) -> FixedSize
+                  -> TokenParser (Maybe Integer, Maybe Integer)
+combineFixedSizes (Nothing, p) (FixedData d) = return (Just d, p)
+combineFixedSizes (Just _, _) (FixedData _) =
+    fail "Multiple data section size specifications."
+combineFixedSizes (d, Nothing) (FixedPointers p) = return (d, Just p)
+combineFixedSizes (_, Just _) (FixedPointers _) =
+    fail "Multiple pointer section size specifications."
+
+fixedSize = do
+    size <- literalInt
+    (exactIdentifier "bit" >> return (FixedData size))
+        <|> (exactIdentifier "bits" >> return (FixedData size))
+        <|> (exactIdentifier "byte" >> return (FixedData (8 * size)))
+        <|> (exactIdentifier "bytes" >> return (FixedData (8 * size)))
+        <|> (exactIdentifier "word" >> return (FixedData (64 * size)))
+        <|> (exactIdentifier "words" >> return (FixedData (64 * size)))
+        <|> (exactIdentifier "pointer" >> return (FixedPointers size))
+        <|> (exactIdentifier "pointers" >> return (FixedPointers size))
+        <?> "\"bits\", \"bytes\", \"words\", or \"pointers\""
 
 structLine :: Maybe [Located Statement] -> TokenParser Declaration
 structLine Nothing = usingDecl <|> constantDecl <|> fieldDecl <|> annotationDecl

compiler/src/Token.hs

@@ -74,6 +74,7 @@ data Token = Identifier String
            | UnionKeyword
            | InterfaceKeyword
            | AnnotationKeyword
+           | FixedKeyword
            deriving (Data, Typeable, Show, Eq)
 
 data Statement = Line TokenSequence

compiler/src/c++-header.mustache

@@ -295,6 +295,7 @@ inline {{fieldType}}::Builder {{typeFullName}}::Builder::init{{fieldTitleCase}}(
 {{/fieldIsBlob}}
 {{! ------------------------------------------------------------------------------------------- }}
 {{#fieldIsStruct}}
+{{^fieldIsInlineStruct}}
 inline {{fieldType}}::Reader {{typeFullName}}::Reader::get{{fieldTitleCase}}() {
 {{#fieldUnion}}
   CAPNPROTO_INLINE_DPRECOND(which() == {{unionTitleCase}}::{{fieldUpperCase}},
@@ -324,6 +325,34 @@ inline {{fieldType}}::Builder {{typeFullName}}::Builder::get{{fieldTitleCase}}()
       {{#fieldDefaultBytes}}DEFAULT_{{fieldUpperCase}}.words{{/fieldDefaultBytes}}
       {{^fieldDefaultBytes}}nullptr{{/fieldDefaultBytes}}));
 }
+{{/fieldIsInlineStruct}}
+{{#fieldIsInlineStruct}}
+inline {{fieldType}}::Reader {{typeFullName}}::Reader::get{{fieldTitleCase}}() {
+{{#fieldUnion}}
+  CAPNPROTO_INLINE_DPRECOND(which() == {{unionTitleCase}}::{{fieldUpperCase}},
+                            "Must check which() before get()ing a union member.");
+{{/fieldUnion}}
+  return {{fieldType}}::Reader(_reader.getInlineStructField(
+      {{fieldOffset}}));
+}
+
+inline {{fieldType}}::Builder {{typeFullName}}::Builder::init{{fieldTitleCase}}() {
+{{#fieldUnion}}
+  _builder.setDataField<{{unionTitleCase}}::Which>(
+      {{unionTagOffset}} * ::capnproto::ELEMENTS, {{unionTitleCase}}::{{fieldUpperCase}});
+{{/fieldUnion}}
+  return {{fieldType}}::Builder(_builder.initInlineStructField(
+      {{fieldOffset}}));
+}
+inline {{fieldType}}::Builder {{typeFullName}}::Builder::get{{fieldTitleCase}}() {
+{{#fieldUnion}}
+  CAPNPROTO_INLINE_DPRECOND(which() == {{unionTitleCase}}::{{fieldUpperCase}},
+                            "Must check which() before get()ing a union member.");
+{{/fieldUnion}}
+  return {{fieldType}}::Builder(_builder.getInlineStructField(
+      {{fieldOffset}}));
+}
+{{/fieldIsInlineStruct}}
 {{/fieldIsStruct}}
 {{! ------------------------------------------------------------------------------------------- }}
 {{#fieldIsList}}