New asynchronous PNG_Canvas interface.

4 files changed, 222 insertions, 16 deletions

diff --git a/libdimensionxx/dimensionxx/png.hpp b/libdimensionxx/dimensionxx/png.hpp
index 07d7c18..c2cdbd5 100644
--- a/libdimensionxx/dimensionxx/png.hpp
+++ b/libdimensionxx/dimensionxx/png.hpp
@@ -25,6 +25,7 @@
 
 #include <istream>
 #include <ostream>
+#include <memory>
 
 namespace Dimension
 {
@@ -35,18 +36,15 @@ namespace Dimension
   {
   public:
     // Input PNG_Canvas; read the Canvas from istr now
-    explicit PNG_Canvas(std::istream& istr)
-      : Canvas(), m_istr(&istr), m_ostr(0), m_written(false) { read(); }
+    explicit PNG_Canvas(std::istream& istr);
 
     // Output PNG_Canvas; write the Canvas to ostr at destruction, or when
     // write() is called.
-    PNG_Canvas(unsigned int x, unsigned int y, std::ostream& ostr)
-      : Canvas(x, y), m_istr(0), m_ostr(&ostr), m_written(false) { }
+    PNG_Canvas(unsigned int x, unsigned int y, std::ostream& ostr);
 
     // I/O PNG_Canvas; read the Canvas from istr now, and write to ostr at
     // destruction or then write() is called.
-    PNG_Canvas(std::istream& istr, std::ostream& ostr)
-      : Canvas(), m_istr(&istr), m_ostr(&ostr), m_written(false) { read(); }
+    PNG_Canvas(std::istream& istr, std::ostream& ostr);
 
     // Call write() if we're an output PNG_Canvas, but trap any exceptions and
     // report a dmnsn_error() instead.
@@ -56,12 +54,23 @@ namespace Dimension
     // error.
     void write();
 
+    // Write the Canvas to the output stream in the background
+    Progress write_async();
+
+    // Construct an input or I/O PNG_Canvas in the background
+    static Progress read_async(std::istream& istr);
+    explicit PNG_Canvas(Progress& progress);
+    explicit PNG_Canvas(Progress& progress, std::ostream& ostr);
+
   protected:
     // In case a derived class needs to set m_canvas after we're constructed
-    PNG_Canvas(std::ostream* ostr)
-      : Canvas(), m_istr(0), m_ostr(ostr), m_written(false) { }
+    explicit PNG_Canvas(std::ostream& ostr);
 
   private:
+    // Copying prohibited
+    PNG_Canvas(const PNG_Canvas&);
+    PNG_Canvas& operator=(const PNG_Canvas&);
+
     std::istream* m_istr;
     std::ostream* m_ostr;
     bool m_written;
@@ -69,10 +78,6 @@ namespace Dimension
     // Read the Canvas from a PNG file, and throw a Dimension_Error upon
     // failure.
     void read();
-
-    // Copying prohibited
-    PNG_Canvas(const PNG_Canvas&);
-    PNG_Canvas& operator=(const PNG_Canvas&);
   };
 }
 
diff --git a/libdimensionxx/dimensionxx/progress.hpp b/libdimensionxx/dimensionxx/progress.hpp
index 72099c4..b9df870 100644
--- a/libdimensionxx/dimensionxx/progress.hpp
+++ b/libdimensionxx/dimensionxx/progress.hpp
@@ -22,16 +22,71 @@
 #define DIMENSIONXX_PROGRESS_HPP
 
 #include <tr1/memory> // For tr1::shared_ptr
+#include <list>
 
 // dmnsn_canvas* wrapper.
 
 namespace Dimension
 {
+  // Base class for persisting objects
+  class Persist_Base
+  {
+  public:
+    virtual ~Persist_Base() = 0;
+
+  protected:
+    Persist_Base() { }
+
+  private:
+    // Copying prohibited
+    Persist_Base(const Persist_Base&);
+    Persist_Base& operator=(const Persist_Base&);
+  };
+
+  // Class for persisting objects
+  template <typename T>
+  class Persist : public Persist_Base
+  {
+  public:
+    Persist(T* t) : m_t(t) { }
+    virtual ~Persist() { delete m_t; }
+
+    T* persisted() const { return m_t; }
+
+  private:
+    T* m_t;
+  };
+
+  // Class for persisting many objects
+  class Persister
+  {
+  public:
+    // Persister();
+    // Persister(const Persister& persister);
+    // ~Persister();
+
+    // Persister& operator=(const Persister& persister);
+
+    template <typename T>
+    void persist(T* t);
+
+    // Access the first persisted element
+    template <typename T>
+    Persist<T>& first();
+
+  private:
+    // Copy-assignment prohibited
+    Persister& operator=(const Persister&);
+
+    std::list<std::tr1::shared_ptr<Persist_Base> > m_persists;
+  };
+
   // dmnsn_progress* wrapper class to represent an asynchronous worker thread
   class Progress
   {
   public:
     explicit Progress(dmnsn_progress* progress);
+    Progress(dmnsn_progress* progress, const Persister& persister);
     // Progress(const Progress& progress);
 
     // Finishes the job without throwing
@@ -47,6 +102,9 @@ namespace Dimension
     // Wait for job to finish, throwing if the job failed
     void finish();
 
+    // Access the set of persisted objects
+    Persister& persister();
+
     // Access the wrapped C object.
     dmnsn_progress*       dmnsn();
     const dmnsn_progress* dmnsn() const;
@@ -56,7 +114,22 @@ namespace Dimension
     Progress& operator=(const Progress&);
 
     std::tr1::shared_ptr<dmnsn_progress*> m_progress;
+    Persister m_persister;
   };
+
+  template <typename T>
+  void
+  Persister::persist(T* t)
+  {
+    m_persists.push_back(std::tr1::shared_ptr<Persist_Base>(new Persist<T>(t)));
+  }
+
+  template <typename T>
+  Persist<T>&
+  Persister::first()
+  {
+    return dynamic_cast<Persist<T>&>(*m_persists.front());
+  }
 }
 
 #endif /* DIMENSIONXX_PROGRESS_HPP */
diff --git a/libdimensionxx/png.cpp b/libdimensionxx/png.cpp
index 029e431..41162e6 100644
--- a/libdimensionxx/png.cpp
+++ b/libdimensionxx/png.cpp
@@ -24,6 +24,22 @@
 
 namespace Dimension
 {
+  PNG_Canvas::PNG_Canvas(std::istream& istr)
+    : Canvas(), m_istr(&istr), m_ostr(0), m_written(false)
+  {
+    read();
+  }
+
+  PNG_Canvas::PNG_Canvas(unsigned int x, unsigned int y, std::ostream& ostr)
+    : Canvas(x, y), m_istr(0), m_ostr(&ostr), m_written(false)
+  { }
+
+  PNG_Canvas::PNG_Canvas(std::istream& istr, std::ostream& ostr)
+    : Canvas(), m_istr(&istr), m_ostr(&ostr), m_written(false)
+  {
+    read();
+  }
+
   // PNG_Canvas destructor.  Call write() to write the PNG file if not already
   // written, but catch any exceptions and instead report the error with
   // dmnsn_error() to avoid throwing from a destructor.
@@ -52,20 +68,109 @@ namespace Dimension
       // Don't call write() if we're not an output PNG_Canvas...
       throw Dimension_Error("Attempt to write canvas to PNG without an output"
                             " stream.");
-    }      
+    }
 
     // Make the C++/C I/O interface
     FILE_Cookie cookie(*m_ostr);
 
     // Write the PNG file
     if (dmnsn_png_write_canvas(m_canvas, cookie.file())) {
-      // The actual write operation failed, for some reason.
+      // The actual write operation failed, for some reason
       throw Dimension_Error("Writing canvas to PNG failed.");
     }
 
     m_written = true; // We've written the file now, don't do it again
   }
 
+  // Write a PNG file in the background
+  Progress
+  PNG_Canvas::write_async()
+  {
+    if (m_written) {
+      // Does writing a PNG file twice make sense?
+      throw Dimension_Error("Attempt to write canvas to PNG twice.");
+    }
+
+    if (!m_ostr) {
+      // Don't call write_async() if we're not an output PNG_Canvas...
+      throw Dimension_Error("Attempt to write canvas to PNG without an output"
+                            " stream.");
+    }
+
+    m_written = true; // We've written the file now, don't do it again
+
+    // Object to persist local variables past function return
+    Persister persister;
+
+    // Make the C++/C I/O interface
+    FILE_Cookie* cookie = new FILE_Cookie(*m_ostr);
+    persister.persist(cookie);
+
+    // Return the Progress object
+    return Progress(dmnsn_png_write_canvas_async(m_canvas, cookie->file()),
+                    persister);
+  }
+
+  // Read a PNG file in the background
+  Progress
+  PNG_Canvas::read_async(std::istream& istr)
+  {
+    // Object to persist local variables past function return
+    Persister persister;
+
+    // Store a pointer to a dmnsn_canvas* in the persister to later construct
+    // the PNG_Canvas
+    dmnsn_canvas** canvas = new dmnsn_canvas*;
+    persister.persist(canvas);
+
+    // Make the C++/C I/O interface
+    FILE_Cookie* cookie = new FILE_Cookie(istr);
+    persister.persist(cookie);
+
+    // Return the Progress object
+    return Progress(dmnsn_png_read_canvas_async(canvas, cookie->file()),
+                    persister);
+  }
+
+  // Construct an input PNG_Canvas from a background task
+  PNG_Canvas::PNG_Canvas(Progress& progress)
+    : Canvas(), m_istr(0), m_ostr(0), m_written(false)
+  {
+    dmnsn_canvas** canvas
+      = progress.persister().first<dmnsn_canvas*>().persisted();
+
+    try {
+      progress.finish();
+    } catch (...) {
+      dmnsn_delete_canvas(*canvas);
+      throw;
+    }
+
+    m_canvas = *canvas;
+  }
+
+  // Construct an I/O PNG_Canvas from a background task
+  PNG_Canvas::PNG_Canvas(Progress& progress, std::ostream& ostr)
+    : Canvas(), m_istr(0), m_ostr(&ostr), m_written(false)
+  {
+    dmnsn_canvas** canvas
+      = progress.persister().first<dmnsn_canvas*>().persisted();
+
+    try {
+      progress.finish();
+    } catch (...) {
+      dmnsn_delete_canvas(*canvas);
+      throw;
+    }
+
+    m_canvas = *canvas;
+  }
+
+  // Protected constructor which sets the canvas to NULL for now
+  PNG_Canvas::PNG_Canvas(std::ostream& ostr)
+    : Canvas(), m_istr(0), m_ostr(&ostr), m_written(false)
+  { }
+
   // Read a canvas from a PNG file.  Uses the FILE_Cookie() interface to make a
   // FILE* corresponding to an std::istream (including std::istringstream, etc).
   void PNG_Canvas::read()
@@ -75,7 +180,7 @@ namespace Dimension
       // so this REALLY shouldn't happen.
       throw Dimension_Error("Attempt to read canvas from PNG without an input"
                             " stream.");
-    }      
+    }
 
     // Make the C++/C I/O interface
     FILE_Cookie cookie(*m_istr);
diff --git a/libdimensionxx/progress.cpp b/libdimensionxx/progress.cpp
index d09ac9b..ca74571 100644
--- a/libdimensionxx/progress.cpp
+++ b/libdimensionxx/progress.cpp
@@ -22,13 +22,20 @@
 
 namespace Dimension
 {
+  Persist_Base::~Persist_Base()
+  { }
+
   Progress::Progress(dmnsn_progress* progress)
     : m_progress(new dmnsn_progress*(progress))
   { }
 
+  Progress::Progress(dmnsn_progress* progress, const Persister& persister)
+    : m_progress(new dmnsn_progress*(progress)), m_persister(persister)
+  { }
+
   Progress::~Progress()
   {
-    if (m_progress.unique()) {
+    if (m_progress && m_progress.unique()) {
       try {
         dmnsn_finish_progress(dmnsn());
       } catch (...) {
@@ -73,20 +80,36 @@ namespace Dimension
   {
     if (m_progress.unique()) {
       dmnsn_finish_progress(dmnsn());
+      m_progress.reset();
     } else {
       throw Dimension_Error("Attempt to finish non-unique Progress.");
     }
   }
 
+  // Access the set of persisted objects
+  Persister&
+  Progress::persister()
+  {
+    return m_persister;
+  }
+
   dmnsn_progress*
   Progress::dmnsn()
   {
+    if (!m_progress) {
+      throw Dimension_Error("Attempting to access finished array.");
+    }
+
     return *m_progress;
   }
 
   const dmnsn_progress*
   Progress::dmnsn() const
   {
+    if (!m_progress) {
+      throw Dimension_Error("Attempting to access finished array.");
+    }
+
     return *m_progress;
   }
 }