[llvm] r194655 - Add dyn_cast<> support to YAML I/O's IO class

[Nick Kledzik]

This is a stepping stone to supporting some semantic level checking which is only relevant when doing input.    Yes, I cringe too when the Input/Output symmetry is broken.  

In particular, I’m working on a way to encode mach-o as yaml for test cases.  I need to handle semantic errors like an invalid symbol index in a relocation.  I’ll need to only do the checks when inputting and then set an error_code just as if there had been a syntax error in the yaml.

-Nick

On Nov 13, 2013, at 7:30 PM, Sean Silva <silvas at purdue.edu> wrote:
> Out of curiousity what is use case for this? One of the things I like about YAMLIO is that both input and output "work from a single point of truth"; being able to distinguish when we are inputting from when we are outputting seems like it could be problematic as it circumvents that property of the interface.
> 
> -- Sean Silva
> 
> 
> On Wed, Nov 13, 2013 at 9:38 PM, Nick Kledzik <kledzik at apple.com> wrote:
> Author: kledzik
> Date: Wed Nov 13 20:38:07 2013
> New Revision: 194655
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=194655&view=rev
> Log:
> Add dyn_cast<> support to YAML I/O's IO class
> 
> Modified:
>     llvm/trunk/include/llvm/Support/YAMLTraits.h
>     llvm/trunk/lib/Support/YAMLTraits.cpp
>     llvm/trunk/unittests/Support/YAMLIOTest.cpp
> 
> Modified: llvm/trunk/include/llvm/Support/YAMLTraits.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/YAMLTraits.h?rev=194655&r1=194654&r2=194655&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/Support/YAMLTraits.h (original)
> +++ llvm/trunk/include/llvm/Support/YAMLTraits.h Wed Nov 13 20:38:07 2013
> @@ -18,6 +18,7 @@
>  #include "llvm/ADT/StringRef.h"
>  #include "llvm/ADT/StringSwitch.h"
>  #include "llvm/ADT/Twine.h"
> +#include "llvm/Support/Casting.h"
>  #include "llvm/Support/Compiler.h"
>  #include "llvm/Support/SourceMgr.h"
>  #include "llvm/Support/YAMLParser.h"
> @@ -317,7 +318,7 @@ public:
>    IO(void *Ctxt=NULL);
>    virtual ~IO();
> 
> -  virtual bool outputting() = 0;
> +  virtual bool outputting() const = 0;
> 
>    virtual unsigned beginSequence() = 0;
>    virtual bool preflightElement(unsigned, void *&) = 0;
> @@ -694,8 +695,10 @@ public:
>    // To set alternate error reporting.
>    void setDiagHandler(llvm::SourceMgr::DiagHandlerTy Handler, void *Ctxt = 0);
> 
> +  static bool classof(const IO *io) { return !io->outputting(); }
> +
>  private:
> -  virtual bool outputting();
> +  virtual bool outputting() const;
>    virtual bool mapTag(StringRef, bool);
>    virtual void beginMapping();
>    virtual void endMapping();
> @@ -819,7 +822,9 @@ public:
>    Output(llvm::raw_ostream &, void *Ctxt=NULL);
>    virtual ~Output();
> 
> -  virtual bool outputting();
> +  static bool classof(const IO *io) { return io->outputting(); }
> +
> +  virtual bool outputting() const;
>    virtual bool mapTag(StringRef, bool);
>    virtual void beginMapping();
>    virtual void endMapping();
> 
> Modified: llvm/trunk/lib/Support/YAMLTraits.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/YAMLTraits.cpp?rev=194655&r1=194654&r2=194655&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Support/YAMLTraits.cpp (original)
> +++ llvm/trunk/lib/Support/YAMLTraits.cpp Wed Nov 13 20:38:07 2013
> @@ -59,7 +59,7 @@ void Input::setDiagHandler(SourceMgr::Di
>    SrcMgr.setDiagHandler(Handler, Ctxt);
>  }
> 
> -bool Input::outputting() {
> +bool Input::outputting() const {
>    return false;
>  }
> 
> @@ -382,7 +382,7 @@ Output::Output(raw_ostream &yout, void *
>  Output::~Output() {
>  }
> 
> -bool Output::outputting() {
> +bool Output::outputting() const {
>    return true;
>  }
> 
> 
> Modified: llvm/trunk/unittests/Support/YAMLIOTest.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Support/YAMLIOTest.cpp?rev=194655&r1=194654&r2=194655&view=diff
> ==============================================================================
> --- llvm/trunk/unittests/Support/YAMLIOTest.cpp (original)
> +++ llvm/trunk/unittests/Support/YAMLIOTest.cpp Wed Nov 13 20:38:07 2013
> @@ -1074,6 +1074,76 @@ TEST(YAMLIO, TestTaggedDocumentsWriteAnd
>  }
> 
> 
> +//===----------------------------------------------------------------------===//
> +//  Test dyn_cast<> on IO object
> +//===----------------------------------------------------------------------===//
> +
> +struct DynCast {
> +  int value;
> +};
> +typedef std::vector<DynCast> DynCastSequence;
> +
> +LLVM_YAML_IS_SEQUENCE_VECTOR(DynCast)
> +
> +namespace llvm {
> +namespace yaml {
> +  template <>
> +  struct MappingTraits<DynCast> {
> +    static void mapping(IO &io, DynCast& info) {
> +      // Change 10 to 13 when writing yaml.
> +      if (Output *output = dyn_cast<Output>(&io)) {
> +        (void)output;
> +        if (info.value == 10)
> +          info.value = 13;
> +      }
> +      io.mapRequired("value", info.value);
> +      // Change 20 to 23 when parsing yaml.
> +      if (Input *input = dyn_cast<Input>(&io)) {
> +        (void)input;
> +        if (info.value == 20)
> +          info.value = 23;
> +      }
> +    }
> +  };
> +}
> +}
> +
> +//
> +// Test writing then reading back a sequence of mappings
> +//
> +TEST(YAMLIO, TestDynCast) {
> +  std::string intermediate;
> +  {
> +    DynCast entry1;
> +    entry1.value = 10;
> +    DynCast entry2;
> +    entry2.value = 20;
> +    DynCast entry3;
> +    entry3.value = 30;
> +    DynCastSequence seq;
> +    seq.push_back(entry1);
> +    seq.push_back(entry2);
> +    seq.push_back(entry3);
> +
> +    llvm::raw_string_ostream ostr(intermediate);
> +    Output yout(ostr);
> +    yout << seq;
> +  }
> +
> +  {
> +    Input yin(intermediate);
> +    DynCastSequence seq2;
> +    yin >> seq2;
> +
> +    EXPECT_FALSE(yin.error());
> +    EXPECT_EQ(seq2.size(), 3UL);
> +    EXPECT_EQ(seq2[0].value, 13);   // Verify changed to 13.
> +    EXPECT_EQ(seq2[1].value, 23);   // Verify changed to 23.
> +    EXPECT_EQ(seq2[2].value, 30);   // Verify stays same.
> +  }
> +}
> +
> +
> 
>  //===----------------------------------------------------------------------===//
>  //  Test error handling
> 
> 
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