Initial implementation of a utility for converting native data

structures to and from YAML using traits.  The first client will
be the test suite of lld.  The documentation will show up at:

   http://llvm.org/docs/YamlIO.html




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170019 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 1114 insertions, 0 deletions

diff --git a/include/llvm/Support/YAMLTraits.h b/include/llvm/Support/YAMLTraits.h
new file mode 100644
index 0000000000..4376165e53
--- /dev/null
+++ b/include/llvm/Support/YAMLTraits.h
@@ -0,0 +1,1114 @@
+//===- llvm/Supporrt/YAMLTraits.h -------------------------------*- C++ -*-===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_YAML_TRAITS_H_
+#define LLVM_YAML_TRAITS_H_
+
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DenseMapInfo.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/StringSwitch.h"
+#include "llvm/ADT/Twine.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/SourceMgr.h"
+#include "llvm/Support/system_error.h"
+#include "llvm/Support/type_traits.h"
+#include "llvm/Support/YAMLParser.h"
+#include "llvm/Support/raw_ostream.h"
+
+
+namespace llvm {
+namespace yaml {
+
+
+/// This class should be specialized by any type that needs to be converted
+/// to/from a YAML mapping.  For example:
+///
+///     struct ScalarBitSetTraits<MyStruct> {
+///       static void mapping(IO &io, MyStruct &s) {
+///         io.mapRequired("name", s.name);
+///         io.mapRequired("size", s.size);
+///         io.mapOptional("age",  s.age);
+///       }
+///     };
+template<class T>
+struct MappingTraits {
+  // Must provide:
+  // static void mapping(IO &io, T &fields);
+};
+
+
+/// This class should be specialized by any integral type that converts
+/// to/from a YAML scalar where there is a one-to-one mapping between
+/// in-memory values and a string in YAML.  For example:
+///
+///     struct ScalarEnumerationTraits<Colors> {
+///         static void enumeration(IO &io, Colors &value) {
+///           io.enumCase(value, "red",   cRed);
+///           io.enumCase(value, "blue",  cBlue);
+///           io.enumCase(value, "green", cGreen);
+///         }
+///       };
+template<typename T>
+struct ScalarEnumerationTraits {
+  // Must provide:
+  // static void enumeration(IO &io, T &value);
+};
+
+
+/// This class should be specialized by any integer type that is a union
+/// of bit values and the YAML representation is a flow sequence of
+/// strings.  For example:
+///
+///      struct ScalarBitSetTraits<MyFlags> {
+///        static void bitset(IO &io, MyFlags &value) {
+///          io.bitSetCase(value, "big",   flagBig);
+///          io.bitSetCase(value, "flat",  flagFlat);
+///          io.bitSetCase(value, "round", flagRound);
+///        }
+///      };
+template<typename T>
+struct ScalarBitSetTraits {
+  // Must provide:
+  // static void bitset(IO &io, T &value);
+};
+
+
+/// This class should be specialized by type that requires custom conversion
+/// to/from a yaml scalar.  For example:
+///
+///    template<>
+///    struct ScalarTraits<MyType> {
+///      static void output(const MyType &val, void*, llvm::raw_ostream &out) {
+///        // stream out custom formatting
+///        out << llvm::format("%x", val);
+///      }
+///      static StringRef input(StringRef scalar, void*, MyType &value) {
+///        // parse scalar and set `value`
+///        // return empty string on success, or error string
+///        return StringRef();
+///      }
+///    };
+template<typename T>
+struct ScalarTraits {
+  // Must provide:
+  //
+  // Function to write the value as a string:
+  //static void output(const T &value, void *ctxt, llvm::raw_ostream &out);
+  //
+  // Function to convert a string to a value.  Returns the empty
+  // StringRef on success or an error string if string is malformed:
+  //static StringRef input(StringRef scalar, void *ctxt, T &value);
+};
+
+
+/// This class should be specialized by any type that needs to be converted
+/// to/from a YAML sequence.  For example:
+///
+///    template<>
+///    struct SequenceTraits< std::vector<MyType> > {
+///      static size_t size(IO &io, std::vector<MyType> &seq) {
+///        return seq.size();
+///      }
+///      static MyType& element(IO &, std::vector<MyType> &seq, size_t index) {
+///        if ( index >= seq.size() )
+///          seq.resize(index+1);
+///        return seq[index];
+///      }
+///    };
+template<typename T>
+struct SequenceTraits {
+  // Must provide:
+  // static size_t size(IO &io, T &seq);
+  // static T::value_type& element(IO &io, T &seq, size_t index);
+  //
+  // The following is option and will cause generated YAML to use
+  // a flow sequence (e.g. [a,b,c]).
+  // static const bool flow = true;
+};
+
+
+/// This class should be specialized by any type that needs to be converted
+/// to/from a list of YAML documents.
+template<typename T>
+struct DocumentListTraits {
+  // Must provide:
+  // static size_t size(IO &io, T &seq);
+  // static T::value_type& element(IO &io, T &seq, size_t index);
+};
+
+
+// Only used by compiler if both template types are the same
+template <typename T, T>
+struct SameType;
+
+// Only used for better diagnostics of missing traits
+template <typename T>
+struct MissingTrait;
+
+
+
+// Test if ScalarEnumerationTraits<T> is defined on type T.
+template <class T>
+struct has_ScalarEnumerationTraits
+{
+  typedef void (*Signature_enumeration)(class IO&, T&);
+
+  template <typename U>
+  static char test(SameType<Signature_enumeration, &U::enumeration>*);
+
+  template <typename U>
+  static double test(...);
+
+public:
+  static bool const value = (sizeof(test<ScalarEnumerationTraits<T> >(0)) == 1);
+};
+
+
+// Test if ScalarBitSetTraits<T> is defined on type T.
+template <class T>
+struct has_ScalarBitSetTraits
+{
+  typedef void (*Signature_bitset)(class IO&, T&);
+
+  template <typename U>
+  static char test(SameType<Signature_bitset, &U::bitset>*);
+
+  template <typename U>
+  static double test(...);
+
+public:
+  static bool const value = (sizeof(test<ScalarBitSetTraits<T> >(0)) == 1);
+};
+
+
+// Test if ScalarTraits<T> is defined on type T.
+template <class T>
+struct has_ScalarTraits
+{
+  typedef llvm::StringRef (*Signature_input)(llvm::StringRef, void*, T&);
+  typedef void (*Signature_output)(const T&, void*, llvm::raw_ostream&);
+
+  template <typename U>
+  static char test(SameType<Signature_input, &U::input>*,
+                   SameType<Signature_output, &U::output>*);
+
+  template <typename U>
+  static double test(...);
+
+public:
+  static bool const value = (sizeof(test<ScalarTraits<T> >(0,0)) == 1);
+};
+
+
+// Test if MappingTraits<T> is defined on type T.
+template <class T>
+struct has_MappingTraits
+{
+  typedef void (*Signature_mapping)(class IO&, T&);
+
+  template <typename U>
+  static char test(SameType<Signature_mapping, &U::mapping>*);
+
+  template <typename U>
+  static double test(...);
+
+public:
+  static bool const value = (sizeof(test<MappingTraits<T> >(0)) == 1);
+};
+
+
+// Test if SequenceTraits<T> is defined on type T
+// and SequenceTraits<T>::flow is *not* defined.
+template <class T>
+struct has_SequenceTraits
+{
+  typedef size_t (*Signature_size)(class IO&, T&);
+
+  template <typename U>
+  static char test(SameType<Signature_size, &U::size>*);
+
+  template <typename U>
+  static double test(...);
+
+  template <typename U> static
+  char flowtest( char[sizeof(&U::flow)] ) ;
+
+  template <typename U>
+  static double flowtest(...);
+
+public:
+  static bool const value =  (sizeof(test<SequenceTraits<T> >(0)) == 1)
+                          && (sizeof(flowtest<T>(0)) != 1);
+};
+
+
+// Test if SequenceTraits<T> is defined on type T
+// and SequenceTraits<T>::flow is defined.
+template <class T>
+struct has_FlowSequenceTraits
+{
+  typedef size_t (*Signature_size)(class IO&, T&);
+
+  template <typename U>
+  static char test(SameType<Signature_size, &U::size>*);
+
+  template <typename U>
+  static double test(...);
+
+  template <typename U> static
+  char flowtest( char[sizeof(&U::flow)] ) ;
+
+  template <typename U>
+  static double flowtest(...);
+
+public:
+  static bool const value =  (sizeof(test<SequenceTraits<T> >(0)) == 1)
+                          && (sizeof(flowtest<T>(0)) == 1);
+};
+
+
+// Test if DocumentListTraits<T> is defined on type T
+template <class T>
+struct has_DocumentListTraits
+{
+  typedef size_t (*Signature_size)(class IO&, T&);
+
+  template <typename U>
+  static char test(SameType<Signature_size, &U::size>*);
+
+  template <typename U>
+  static double test(...);
+
+public:
+  static bool const value =  (sizeof(test<DocumentListTraits<T> >(0)) == 1);
+};
+
+
+
+
+template<typename T>
+struct missingTraits : public  llvm::integral_constant<bool,
+                                         !has_ScalarEnumerationTraits<T>::value
+                                      && !has_ScalarBitSetTraits<T>::value
+                                      && !has_ScalarTraits<T>::value
+                                      && !has_MappingTraits<T>::value
+                                      && !has_SequenceTraits<T>::value
+                                      && !has_FlowSequenceTraits<T>::value
+                                      && !has_DocumentListTraits<T>::value >  {};
+
+
+// Base class for Input and Output.
+class IO {
+public:
+
+  IO(void *Ctxt=NULL);
+  virtual ~IO();
+
+  virtual bool outputting() = 0;
+
+  virtual unsigned beginSequence() = 0;
+  virtual bool preflightElement(unsigned, void *&) = 0;
+  virtual void postflightElement(void*) = 0;
+  virtual void endSequence() = 0;
+
+  virtual unsigned beginFlowSequence() = 0;
+  virtual bool preflightFlowElement(unsigned, void *&) = 0;
+  virtual void postflightFlowElement(void*) = 0;
+  virtual void endFlowSequence() = 0;
+
+  virtual void beginMapping() = 0;
+  virtual void endMapping() = 0;
+  virtual bool preflightKey(const char*, bool, bool, bool &, void *&) = 0;
+  virtual void postflightKey(void*) = 0;
+
+  virtual void beginEnumScalar() = 0;
+  virtual bool matchEnumScalar(const char*, bool) = 0;
+  virtual void endEnumScalar() = 0;
+
+  virtual bool beginBitSetScalar(bool &) = 0;
+  virtual bool bitSetMatch(const char*, bool) = 0;
+  virtual void endBitSetScalar() = 0;
+
+  virtual void scalarString(StringRef &) = 0;
+
+  virtual void setError(const Twine &) = 0;
+
+  template <typename T>
+  void enumCase(T &Val, const char* Str, const T ConstVal) {
+    if ( matchEnumScalar(Str, (Val == ConstVal)) ) {
+      Val = ConstVal;
+    }
+  }
+
+  // allow anonymous enum values to be used with LLVM_YAML_STRONG_TYPEDEF
+  template <typename T>
+  void enumCase(T &Val, const char* Str, const uint32_t ConstVal) {
+    if ( matchEnumScalar(Str, (Val == static_cast<T>(ConstVal))) ) {
+      Val = ConstVal;
+    }
+  }
+
+  template <typename T>
+  void bitSetCase(T &Val, const char* Str, const T ConstVal) {
+    if ( bitSetMatch(Str, ((Val & ConstVal) == ConstVal)) ) {
+      Val = Val | ConstVal;
+    }
+  }
+
+  // allow anonymous enum values to be used with LLVM_YAML_STRONG_TYPEDEF
+  template <typename T>
+  void bitSetCase(T &Val, const char* Str, const uint32_t ConstVal) {
+    if ( bitSetMatch(Str, ((Val & ConstVal) == ConstVal)) ) {
+      Val = Val | ConstVal;
+    }
+  }
+
+  void *getContext();
+  void setContext(void *);
+
+  template <typename T>
+  void mapRequired(const char* Key, T& Val) {
+    this->processKey(Key, Val, true);
+  }
+
+  template <typename T>
+  typename llvm::enable_if_c<has_SequenceTraits<T>::value,void>::type
+  mapOptional(const char* Key, T& Val) {
+    // omit key/value instead of outputting empty sequence
+    if ( this->outputting() && !(Val.begin() != Val.end()) )
+      return;
+    this->processKey(Key, Val, false);
+  }
+
+  template <typename T>
+  typename llvm::enable_if_c<!has_SequenceTraits<T>::value,void>::type
+  mapOptional(const char* Key, T& Val) {
+    this->processKey(Key, Val, false);
+  }
+
+  template <typename T>
+  void mapOptional(const char* Key, T& Val, const T& Default) {
+    this->processKeyWithDefault(Key, Val, Default, false);
+  }
+
+
+private:
+  template <typename T>
+  void processKeyWithDefault(const char *Key, T &Val, const T& DefaultValue,
+                                                                bool Required) {
+    void *SaveInfo;
+    bool UseDefault;
+    const bool sameAsDefault = (Val == DefaultValue);
+    if ( this->preflightKey(Key, Required, sameAsDefault, UseDefault,
+                                                                  SaveInfo) ) {
+      yamlize(*this, Val, Required);
+      this->postflightKey(SaveInfo);
+    }
+    else {
+      if ( UseDefault )
+        Val = DefaultValue;
+    }
+  }
+
+  template <typename T>
+  void processKey(const char *Key, T &Val, bool Required) {
+    void *SaveInfo;
+    bool UseDefault;
+    if ( this->preflightKey(Key, Required, false, UseDefault, SaveInfo) ) {
+      yamlize(*this, Val, Required);
+      this->postflightKey(SaveInfo);
+    }
+  }
+
+private:
+  void  *Ctxt;
+};
+
+
+
+template<typename T>
+typename llvm::enable_if_c<has_ScalarEnumerationTraits<T>::value,void>::type
+yamlize(IO &io, T &Val, bool) {
+  io.beginEnumScalar();
+  ScalarEnumerationTraits<T>::enumeration(io, Val);
+  io.endEnumScalar();
+}
+
+template<typename T>
+typename llvm::enable_if_c<has_ScalarBitSetTraits<T>::value,void>::type
+yamlize(IO &io, T &Val, bool) {
+  bool DoClear;
+  if ( io.beginBitSetScalar(DoClear) ) {
+    if ( DoClear )
+      Val = static_cast<T>(0);
+    ScalarBitSetTraits<T>::bitset(io, Val);
+    io.endBitSetScalar();
+  }
+}
+
+
+template<typename T>
+typename llvm::enable_if_c<has_ScalarTraits<T>::value,void>::type
+yamlize(IO &io, T &Val, bool) {
+  if ( io.outputting() ) {
+    std::string Storage;
+    llvm::raw_string_ostream Buffer(Storage);
+    ScalarTraits<T>::output(Val, io.getContext(), Buffer);
+    StringRef Str = Buffer.str();
+    io.scalarString(Str);
+  }
+  else {
+    StringRef Str;
+    io.scalarString(Str);
+    StringRef Result = ScalarTraits<T>::input(Str, io.getContext(), Val);
+    if ( !Result.empty() ) {
+      io.setError(llvm::Twine(Result));
+    }
+  }
+}
+
+
+template<typename T>
+typename llvm::enable_if_c<has_MappingTraits<T>::value, void>::type
+yamlize(IO &io, T &Val, bool) {
+  io.beginMapping();
+  MappingTraits<T>::mapping(io, Val);
+  io.endMapping();
+}
+
+#ifndef BUILDING_YAMLIO
+template<typename T>
+typename llvm::enable_if_c<missingTraits<T>::value, void>::type
+yamlize(IO &io, T &Val, bool) {
+  char missing_yaml_trait_for_type[sizeof(MissingTrait<T>)];
+}
+#endif
+
+template<typename T>
+typename llvm::enable_if_c<has_SequenceTraits<T>::value,void>::type
+yamlize(IO &io, T &Seq, bool) {
+  unsigned incount = io.beginSequence();
+  unsigned count = io.outputting() ? SequenceTraits<T>::size(io, Seq) : incount;
+  for(unsigned i=0; i < count; ++i) {
+    void *SaveInfo;
+    if ( io.preflightElement(i, SaveInfo) ) {
+      yamlize(io, SequenceTraits<T>::element(io, Seq, i), true);
+      io.postflightElement(SaveInfo);
+    }
+  }
+  io.endSequence();
+}
+
+template<typename T>
+typename llvm::enable_if_c<has_FlowSequenceTraits<T>::value,void>::type
+yamlize(IO &io, T &Seq, bool) {
+  unsigned incount = io.beginFlowSequence();
+  unsigned count = io.outputting() ? SequenceTraits<T>::size(io, Seq) : incount;
+  for(unsigned i=0; i < count; ++i) {
+    void *SaveInfo;
+    if ( io.preflightFlowElement(i, SaveInfo) ) {
+      yamlize(io, SequenceTraits<T>::element(io, Seq, i), true);
+      io.postflightFlowElement(SaveInfo);
+    }
+  }
+  io.endFlowSequence();
+}
+
+
+
+// Clients of YAML I/O only see declaration of the traits for built-in
+// types.  The implementation is in the LLVM Support library.  Without
+// this #ifdef, every client would get a copy of the implementation of
+// these traits.
+#ifndef BUILDING_YAMLIO
+template<>
+struct ScalarTraits<bool> {
+  static void output(const bool &, void*, llvm::raw_ostream &);
+  static llvm::StringRef input(llvm::StringRef , void*, bool &);
+};
+
+template<>
+struct ScalarTraits<StringRef> {
+  static void output(const StringRef &, void*, llvm::raw_ostream &);
+  static llvm::StringRef input(llvm::StringRef , void*, StringRef &);
+};
+
+template<>
+struct ScalarTraits<uint8_t> {
+  static void output(const uint8_t &, void*, llvm::raw_ostream &);
+  static llvm::StringRef input(llvm::StringRef , void*, uint8_t &);
+};
+
+template<>
+struct ScalarTraits<uint16_t> {
+  static void output(const uint16_t &, void*, llvm::raw_ostream &);
+  static llvm::StringRef input(llvm::StringRef , void*, uint16_t &);
+};
+
+template<>
+struct ScalarTraits<uint32_t> {
+  static void output(const uint32_t &, void*, llvm::raw_ostream &);
+  static llvm::StringRef input(llvm::StringRef , void*, uint32_t &);
+};
+
+template<>
+struct ScalarTraits<uint64_t> {
+  static void output(const uint64_t &, void*, llvm::raw_ostream &);
+  static llvm::StringRef input(llvm::StringRef , void*, uint64_t &);
+};
+
+template<>
+struct ScalarTraits<int8_t> {
+  static void output(const int8_t &, void*, llvm::raw_ostream &);
+  static llvm::StringRef input(llvm::StringRef , void*, int8_t &);
+};
+
+template<>
+struct ScalarTraits<int16_t> {
+  static void output(const int16_t &, void*, llvm::raw_ostream &);
+  static llvm::StringRef input(llvm::StringRef , void*, int16_t &);
+};
+
+template<>
+struct ScalarTraits<int32_t> {
+  static void output(const int32_t &, void*, llvm::raw_ostream &);
+  static llvm::StringRef input(llvm::StringRef , void*, int32_t &);
+};
+
+template<>
+struct ScalarTraits<int64_t> {
+  static void output(const int64_t &, void*, llvm::raw_ostream &);
+  static llvm::StringRef input(llvm::StringRef , void*, int64_t &);
+};
+
+template<>
+struct ScalarTraits<float> {
+  static void output(const float &, void*, llvm::raw_ostream &);
+  static llvm::StringRef input(llvm::StringRef , void*, float &);
+};
+
+template<>
+struct ScalarTraits<double> {
+  static void output(const double &, void*, llvm::raw_ostream &);
+  static llvm::StringRef input(llvm::StringRef , void*, double &);
+};
+#endif
+
+
+
+// Utility for use within MappingTraits<>::mapping() method
+// to [de]normalize an object for use with YAML conversion.
+template <typename TNorm, typename TFinal>
+struct MappingNormalization {
+  MappingNormalization(IO &i_o, TFinal &Obj)
+      : io(i_o), BufPtr(NULL), Result(Obj) {
+    if ( io.outputting() ) {
+      BufPtr = new (&Buffer) TNorm(io, Obj);
+    }
+    else {
+      BufPtr = new (&Buffer) TNorm(io);
+    }
+  }
+
+  ~MappingNormalization() {
+    if ( ! io.outputting() ) {
+      Result = BufPtr->denormalize(io);
+    }
+    BufPtr->~TNorm();
+  }
+
+  TNorm* operator->() { return BufPtr; }
+
+private:
+  typedef typename llvm::AlignedCharArrayUnion<TNorm> Storage;
+
+  Storage       Buffer;
+  IO           &io;
+  TNorm        *BufPtr;
+  TFinal       &Result;
+};
+
+
+
+// Utility for use within MappingTraits<>::mapping() method
+// to [de]normalize an object for use with YAML conversion.
+template <typename TNorm, typename TFinal>
+struct MappingNormalizationHeap {
+  MappingNormalizationHeap(IO &i_o, TFinal &Obj)
+    : io(i_o), BufPtr(NULL), Result(Obj) {
+    if ( io.outputting() ) {
+      BufPtr = new (&Buffer) TNorm(io, Obj);
+    }
+    else {
+      BufPtr = new TNorm(io);
+    }
+  }
+
+  ~MappingNormalizationHeap() {
+    if ( io.outputting() ) {
+      BufPtr->~TNorm();
+    }
+    else {
+      Result = BufPtr->denormalize(io);
+    }
+  }
+
+  TNorm* operator->() { return BufPtr; }
+
+private:
+  typedef typename llvm::AlignedCharArrayUnion<TNorm> Storage;
+
+  Storage       Buffer;
+  IO           &io;
+  TNorm        *BufPtr;
+  TFinal       &Result;
+};
+
+
+
+///
+/// The Input class is used to parse a yaml document into in-memory structs
+/// and vectors.
+///
+/// It works by using YAMLParser to do a syntax parse of the entire yaml
+/// document, then the Input class builds a graph of HNodes which wraps
+/// each yaml Node.  The extra layer is buffering.  The low level yaml
+/// parser only lets you look at each node once.  The buffering layer lets
+/// you search and interate multiple times.  This is necessary because
+/// the mapRequired() method calls may not be in the same order
+/// as the keys in the document.
+///
+class Input : public IO {
+public:
+  // Construct a yaml Input object from a StringRef and optional user-data.
+  Input(StringRef InputContent, void *Ctxt=NULL);
+
+  // Check if there was an syntax or semantic error during parsing.
+  llvm::error_code error();
+
+  // To set alternate error reporting.
+  void setDiagHandler(llvm::SourceMgr::DiagHandlerTy Handler, void *Ctxt = 0);
+
+private:
+  virtual bool outputting();
+  virtual void beginMapping();
+  virtual void endMapping();
+  virtual bool preflightKey(const char *, bool, bool, bool &, void *&);
+  virtual void postflightKey(void *);
+  virtual unsigned beginSequence();
+  virtual void endSequence();
+  virtual bool preflightElement(unsigned index, void *&);
+  virtual void postflightElement(void *);
+  virtual unsigned beginFlowSequence();
+  virtual bool preflightFlowElement(unsigned , void *&);
+  virtual void postflightFlowElement(void *);
+  virtual void endFlowSequence();
+  virtual void beginEnumScalar();
+  virtual bool matchEnumScalar(const char*, bool);
+  virtual void endEnumScalar();
+  virtual bool beginBitSetScalar(bool &);
+  virtual bool bitSetMatch(const char *, bool );
+  virtual void endBitSetScalar();
+  virtual void scalarString(StringRef &);
+  virtual void setError(const Twine &message);
+
+  class HNode {
+  public:
+    HNode(Node *n) : _node(n) { }
+    static inline bool classof(const HNode *) { return true; }
+
+    Node *_node;
+  };
+
+  class EmptyHNode : public HNode {
+  public:
+    EmptyHNode(Node *n) : HNode(n) { }
+    static inline bool classof(const HNode *n) {
+      return NullNode::classof(n->_node);
+    }
+    static inline bool classof(const EmptyHNode *) { return true; }
+  };
+
+  class ScalarHNode : public HNode {
+  public:
+    ScalarHNode(Node *n, StringRef s) : HNode(n), _value(s) { }
+
+    StringRef value() const { return _value; }
+
+    static inline bool classof(const HNode *n) {
+      return ScalarNode::classof(n->_node);
+    }
+    static inline bool classof(const ScalarHNode *) { return true; }
+  protected:
+    StringRef _value;
+  };
+
+  class MapHNode : public HNode {
+  public:
+    MapHNode(Node *n) : HNode(n) { }
+
+    static inline bool classof(const HNode *n) {
+      return MappingNode::classof(n->_node);
+    }
+    static inline bool classof(const MapHNode *) { return true; }
+
+    struct StrMappingInfo {
+      static StringRef getEmptyKey() { return StringRef(); }
+      static StringRef getTombstoneKey() { return StringRef(" ", 0); }
+      static unsigned getHashValue(StringRef const val) {
+                                                return llvm::HashString(val); }
+      static bool isEqual(StringRef const lhs,
+                          StringRef const rhs) { return lhs.equals(rhs); }
+    };
+    typedef llvm::DenseMap<StringRef, HNode*, StrMappingInfo> NameToNode;
+
+    bool isValidKey(StringRef key);
+
+    NameToNode                        Mapping;
+    llvm::SmallVector<const char*, 6> ValidKeys;
+  };
+
+  class SequenceHNode : public HNode {
+  public:
+    SequenceHNode(Node *n) : HNode(n) { }
+
+    static inline bool classof(const HNode *n) {
+      return SequenceNode::classof(n->_node);
+    }
+    static inline bool classof(const SequenceHNode *) { return true; }
+
+    std::vector<HNode*> Entries;
+  };
+
+  Input::HNode *createHNodes(Node *node);
+  void setError(HNode *hnode, const Twine &message);
+  void setError(Node *node, const Twine &message);
+
+
+public:
+  // These are only used by operator>>. They could be private
+  // if those templated things could be made friends.
+  bool setCurrentDocument();
+  void nextDocument();
+
+private:
+  llvm::yaml::Stream              *Strm;
+  llvm::SourceMgr                  SrcMgr;
+  llvm::error_code                 EC;
+  llvm::BumpPtrAllocator           Allocator;
+  llvm::yaml::document_iterator    DocIterator;
+  std::vector<bool>                BitValuesUsed;
+  HNode                           *CurrentNode;
+  bool                             ScalarMatchFound;
+};
+
+
+
+
+///
+/// The Output class is used to generate a yaml document from in-memory structs
+/// and vectors.
+///
+class Output : public IO {
+public:
+  Output(llvm::raw_ostream &, void *Ctxt=NULL);
+  virtual ~Output();
+
+  virtual bool outputting();
+  virtual void beginMapping();
+  virtual void endMapping();
+  virtual bool preflightKey(const char *key, bool, bool, bool &, void *&);
+  virtual void postflightKey(void *);
+  virtual unsigned beginSequence();
+  virtual void endSequence();
+  virtual bool preflightElement(unsigned, void *&);
+  virtual void postflightElement(void *);
+  virtual unsigned beginFlowSequence();
+  virtual bool preflightFlowElement(unsigned, void *&);
+  virtual void postflightFlowElement(void *);
+  virtual void endFlowSequence();
+  virtual void beginEnumScalar();
+  virtual bool matchEnumScalar(const char*, bool);
+  virtual void endEnumScalar();
+  virtual bool beginBitSetScalar(bool &);
+  virtual bool bitSetMatch(const char *, bool );
+  virtual void endBitSetScalar();
+  virtual void scalarString(StringRef &);
+  virtual void setError(const Twine &message);
+
+public:
+  // These are only used by operator<<. They could be private
+  // if that templated operator could be made a friend.
+  void beginDocuments();
+  bool preflightDocument(unsigned);
+  void postflightDocument();
+  void endDocuments();
+
+private:
+  void output(StringRef s);
+  void outputUpToEndOfLine(StringRef s);
+  void newLineCheck();
+  void outputNewLine();
+  void paddedKey(StringRef key);
+
+  enum InState { inSeq, inFlowSeq, inMapFirstKey, inMapOtherKey };
+
+  llvm::raw_ostream       &Out;
+  SmallVector<InState, 8>  StateStack;
+  int                      Column;
+  int                      ColumnAtFlowStart;
+  bool                     NeedBitValueComma;
+  bool                     NeedFlowSequenceComma;
+  bool                     EnumerationMatchFound;
+  bool                     NeedsNewLine;
+};
+
+
+
+
+/// YAML I/O does conversion based on types. But often native data types
+/// are just a typedef of built in intergral types (e.g. int).  But the C++
+/// type matching system sees through the typedef and all the typedefed types
+/// look like a built in type. This will cause the generic YAML I/O conversion
+/// to be used. To provide better control over the YAML conversion, you can
+/// use this macro instead of typedef.  It will create a class with one field
+/// and automatic conversion operators to and from the base type.
+/// Based on BOOST_STRONG_TYPEDEF
+#define LLVM_YAML_STRONG_TYPEDEF(_base, _type)                                 \
+    struct _type {                                                             \
+        _type() { }                                                            \
+        _type(const _base v) : value(v) { }                                    \
+        _type(const _type &v) : value(v.value) {}                              \
+        _type &operator=(const _type &rhs) { value = rhs.value; return *this; }\
+        _type &operator=(const _base &rhs) { value = rhs; return *this; }      \
+        operator const _base & () const { return value; }                      \
+        bool operator==(const _type &rhs) const { return value == rhs.value; } \
+        bool operator==(const _base &rhs) const { return value == rhs; }       \
+        bool operator<(const _type &rhs) const { return value < rhs.value; }   \
+        _base value;                                                           \
+    };
+
+
+
+///
+/// Use these types instead of uintXX_t in any mapping to have
+/// its yaml output formatted as hexadecimal.
+///
+LLVM_YAML_STRONG_TYPEDEF(uint8_t, Hex8)
+LLVM_YAML_STRONG_TYPEDEF(uint16_t, Hex16)
+LLVM_YAML_STRONG_TYPEDEF(uint32_t, Hex32)
+LLVM_YAML_STRONG_TYPEDEF(uint64_t, Hex64)
+
+
+// Clients of YAML I/O only see declaration of the traits for Hex*
+// types.  The implementation is in the LLVM Support library.  Without
+// this #ifdef, every client would get a copy of the implementation of
+// these traits.
+#ifndef BUILDING_YAMLIO
+template<>
+struct ScalarTraits<Hex8> {
+  static void output(const Hex8 &, void*, llvm::raw_ostream &);
+  static llvm::StringRef input(llvm::StringRef , void*, Hex8 &);
+};
+
+template<>
+struct ScalarTraits<Hex16> {
+  static void output(const Hex16 &, void*, llvm::raw_ostream &);
+  static llvm::StringRef input(llvm::StringRef , void*, Hex16 &);
+};
+
+template<>
+struct ScalarTraits<Hex32> {
+  static void output(const Hex32 &, void*, llvm::raw_ostream &);
+  static llvm::StringRef input(llvm::StringRef , void*, Hex32 &);
+};
+
+template<>
+struct ScalarTraits<Hex64> {
+  static void output(const Hex64 &, void*, llvm::raw_ostream &);
+  static llvm::StringRef input(llvm::StringRef , void*, Hex64 &);
+};
+#endif
+
+
+// Define non-member operator>> so that Input can stream in a document list.
+template <typename T>
+inline
+typename llvm::enable_if_c<has_DocumentListTraits<T>::value,Input &>::type
+operator>>(Input &yin, T &docList) {
+  int i = 0;
+  while ( yin.setCurrentDocument() ) {
+    yamlize(yin, DocumentListTraits<T>::element(yin, docList, i), true);
+    if ( yin.error() )
+      return yin;
+    yin.nextDocument();
+    ++i;
+  }
+  return yin;
+}
+
+// Define non-member operator>> so that Input can stream in a map as a document.
+template <typename T>
+inline
+typename llvm::enable_if_c<has_MappingTraits<T>::value,Input &>::type
+operator>>(Input &yin, T &docMap) {
+  yin.setCurrentDocument();
+  yamlize(yin, docMap, true);
+  return yin;
+}
+
+// Define non-member operator>> so that Input can stream in a sequence as
+// a document.
+template <typename T>
+inline
+typename llvm::enable_if_c<has_SequenceTraits<T>::value,Input &>::type
+operator>>(Input &yin, T &docSeq) {
+  yin.setCurrentDocument();
+  yamlize(yin, docSeq, true);
+  return yin;
+}
+
+#ifndef BUILDING_YAMLIO
+// Provide better error message about types missing a trait specialization
+template <typename T>
+inline
+typename llvm::enable_if_c<missingTraits<T>::value,Input &>::type
+operator>>(Input &yin, T &docSeq) {
+  char missing_yaml_trait_for_type[sizeof(MissingTrait<T>)];
+  return yin;
+}
+#endif
+
+
+// Define non-member operator<< so that Output can stream out document list.
+template <typename T>
+inline
+typename llvm::enable_if_c<has_DocumentListTraits<T>::value,Output &>::type
+operator<<(Output &yout, T &docList) {
+  yout.beginDocuments();
+  const size_t count = DocumentListTraits<T>::size(yout, docList);
+  for(size_t i=0; i < count; ++i) {
+    if ( yout.preflightDocument(i) ) {
+      yamlize(yout, DocumentListTraits<T>::element(yout, docList, i), true);
+      yout.postflightDocument();
+    }
+  }
+  yout.endDocuments();
+  return yout;
+}
+
+// Define non-member operator<< so that Output can stream out a map.
+template <typename T>
+inline
+typename llvm::enable_if_c<has_MappingTraits<T>::value,Output &>::type
+operator<<(Output &yout, T &map) {
+  yout.beginDocuments();
+  if ( yout.preflightDocument(0) ) {
+    yamlize(yout, map, true);
+    yout.postflightDocument();
+  }
+  yout.endDocuments();
+  return yout;
+}
+
+// Define non-member operator<< so that Output can stream out a sequence.
+template <typename T>
+inline
+typename llvm::enable_if_c<has_SequenceTraits<T>::value,Output &>::type
+operator<<(Output &yout, T &seq) {
+  yout.beginDocuments();
+  if ( yout.preflightDocument(0) ) {
+    yamlize(yout, seq, true);
+    yout.postflightDocument();
+  }
+  yout.endDocuments();
+  return yout;
+}
+
+#ifndef BUILDING_YAMLIO
+// Provide better error message about types missing a trait specialization
+template <typename T>
+inline
+typename llvm::enable_if_c<missingTraits<T>::value,Output &>::type
+operator<<(Output &yout, T &seq) {
+  char missing_yaml_trait_for_type[sizeof(MissingTrait<T>)];
+  return yout;
+}
+#endif
+
+
+} // namespace yaml
+} // namespace llvm
+
+
+/// Utility for declaring that a std::vector of a particular type
+/// should be considered a YAML sequence.
+#define LLVM_YAML_IS_SEQUENCE_VECTOR(_type)                                 \
+  namespace llvm {                                                          \
+  namespace yaml {                                                          \
+    template<>                                                              \
+    struct SequenceTraits< std::vector<_type> > {                           \
+      static size_t size(IO &io, std::vector<_type> &seq) {                 \
+        return seq.size();                                                  \
+      }                                                                     \
+      static _type& element(IO &io, std::vector<_type> &seq, size_t index) {\
+        if ( index >= seq.size() )                                          \
+          seq.resize(index+1);                                              \
+        return seq[index];                                                  \
+      }                                                                     \
+    };                                                                      \
+  }                                                                         \
+  }
+
+/// Utility for declaring that a std::vector of a particular type
+/// should be considered a YAML flow sequence.
+#define LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(_type)                            \
+  namespace llvm {                                                          \
+  namespace yaml {                                                          \
+    template<>                                                              \
+    struct SequenceTraits< std::vector<_type> > {                           \
+      static size_t size(IO &io, std::vector<_type> &seq) {                 \
+        return seq.size();                                                  \
+      }                                                                     \
+      static _type& element(IO &io, std::vector<_type> &seq, size_t index) {\
+        if ( index >= seq.size() )                                          \
+          seq.resize(index+1);                                              \
+        return seq[index];                                                  \
+      }                                                                     \
+      static const bool flow = true;                                        \
+    };                                                                      \
+  }                                                                         \
+  }
+
+/// Utility for declaring that a std::vector of a particular type
+/// should be considered a YAML document list.
+#define LLVM_YAML_IS_DOCUMENT_LIST_VECTOR(_type)                            \
+  namespace llvm {                                                          \
+  namespace yaml {                                                          \
+    template<>                                                              \
+    struct DocumentListTraits< std::vector<_type> > {                       \
+      static size_t size(IO &io, std::vector<_type> &seq) {                 \
+        return seq.size();                                                  \
+      }                                                                     \
+      static _type& element(IO &io, std::vector<_type> &seq, size_t index) {\
+        if ( index >= seq.size() )                                          \
+          seq.resize(index+1);                                              \
+        return seq[index];                                                  \
+      }                                                                     \
+    };                                                                      \
+  }                                                                         \
+  }
+
+
+
+#endif // LLVM_YAML_TRAITS_H_