Unitary changes (#599)

* Define SampleBlockFactory replacing static members of SampleBlock...

... This will become an abstract base class

* Sequence and WaveTrack only store SampleBlockFactory not Project...

... This adds a dependency from Track to SampleBlock which temporarily enlarges
a cycle in the dependency graph

* Register a global factory of SampleBlockFactory...

... so that later we can make an abstract SampleBlockFactory, separate from the
concrete implementation in terms of sqlite, and inject the dependency at startup
avoiding static dependency

* New concrete classes SqliteSampleBlock, SqliteSampleBlockFactory...

... separated from abstract base classes and put into a new source file,
breaking dependency cycles, and perhaps allowing easy reimplementation for other
databases in the future.

Note that the new file is a header-less plug-in!  Nothing depends on it.  It
uses static initialization to influence the program's behavior.

* Compile dependency on sqlite3.h limited to just two .cpp files...

... these are ProjectFileIO.cpp and SqliteSampleBlock.cpp.

But there is still close cooperation of ProjectFileIO and SqliteSampleBlock.cpp.
This suggests that these files ought to be merged, and perhaps ProjectFileIO
also needs to be split into abstract and concrete classes, and there should be
another injection of a factory function at startup.  That will make the choice
of database implementation even more modular.

Also removed one unnecessary inclusion of ProjectFileIO.h

* Fix crashes cutting and pasting cross-project...

... in case the source project is closed before the paste happens.

This caused destruction of the ProjectFileIO object and a closing of the sqlite
database with the sample data in it, leaving dangling references in the
SqliteSampleBlock objects.

The fix is that the SqliteSampleBlockFactory object holds a shared_ptr to the
ProjectFileIO object.  So the clipboard may own WaveTracks, which own WaveClips,
which own Sequences, which own SqliteSampleBlockFactories, which keep the
ProjectFileIO and the database connection alive until the clipboard is cleared.

The consequence of the fix is delayed closing of the entire database associated
with the source project.

If the source project is reopened before the clipboard is cleared, will there
be correct concurrent access to the same persistent store?  My preliminary
trials suggest this is so (reopening a saved project, deleting from it, closing
it again -- the clipboard contents are still unchanged and available).

src/SampleBlock.h

@@ -11,7 +11,8 @@ SampleBlock.h
 
 #include "ClientData.h" // to inherit
 
-#include <sqlite3.h>
+#include <functional>
+#include <memory>
 
 class AudacityProject;
 class ProjectFileIO;
@@ -19,7 +20,13 @@ class XMLWriter;
 
 class SampleBlock;
 using SampleBlockPtr = std::shared_ptr<SampleBlock>;
-using SampleBlockID = sqlite3_int64;
+class SampleBlockFactory;
+using SampleBlockFactoryPtr = std::shared_ptr<SampleBlockFactory>;
+using SampleBlockFactoryFactory =
+   std::function< SampleBlockFactoryPtr( AudacityProject& ) >;
+
+//using SampleBlockID = sqlite3_int64; // Trying not to depend on sqlite headers
+using SampleBlockID = long long;
 
 class MinMaxRMS
 {
@@ -29,107 +36,73 @@ public:
    float RMS;
 };
 
+class SqliteSampleBlockFactory;
+
+///\brief Abstract class allows access to contents of a block of sound samples,
+/// serialization as XML, and reference count management that can suppress
+/// reclamation of its storage
 class SampleBlock
 {
 public:
-   SampleBlock(AudacityProject *project);
    virtual ~SampleBlock();
 
-   static SampleBlockPtr Get(AudacityProject *project,
-                             SampleBlockID sbid);
+   virtual void Lock() = 0;
+   virtual void Unlock() = 0;
+   virtual void CloseLock() = 0;
+   
+   virtual SampleBlockID GetBlockID() = 0;
 
-   static SampleBlockPtr Create(AudacityProject *project,
-                                samplePtr src,
-                                size_t numsamples,
-                                sampleFormat srcformat);
-
-   static SampleBlockPtr CreateSilent(AudacityProject *project,
-                                      size_t numsamples,
-                                      sampleFormat srcformat);
-
-   static SampleBlockPtr CreateFromXML(AudacityProject *project,
-                                       sampleFormat srcformat,
-                                       const wxChar **attrs);
-
-   void Lock();
-   void Unlock();
-   void CloseLock();
-
-   bool SetSamples(samplePtr src, size_t numsamples, sampleFormat srcformat);
-
-   bool SetSilent(size_t numsamples, sampleFormat srcformat);
-
-   bool Commit();
-
-   void Delete();
-
-   SampleBlockID GetBlockID();
-
-   size_t GetSamples(samplePtr dest,
+   virtual size_t GetSamples(samplePtr dest,
                      sampleFormat destformat,
                      size_t sampleoffset,
-                     size_t numsamples);
-   sampleFormat GetSampleFormat() const;
-   size_t GetSampleCount() const;
+                     size_t numsamples) = 0;
 
-   bool GetSummary256(float *dest, size_t frameoffset, size_t numframes);
-   bool GetSummary64k(float *dest, size_t frameoffset, size_t numframes);
-   double GetSumMin() const;
-   double GetSumMax() const;
-   double GetSumRms() const;
+   virtual size_t GetSampleCount() const = 0;
+
+   virtual bool
+      GetSummary256(float *dest, size_t frameoffset, size_t numframes) = 0;
+   virtual bool
+      GetSummary64k(float *dest, size_t frameoffset, size_t numframes) = 0;
 
    /// Gets extreme values for the specified region
-   MinMaxRMS GetMinMaxRMS(size_t start, size_t len);
+   virtual MinMaxRMS GetMinMaxRMS(size_t start, size_t len) = 0;
 
    /// Gets extreme values for the entire block
-   MinMaxRMS GetMinMaxRMS() const;
+   virtual MinMaxRMS GetMinMaxRMS() const = 0;
 
-   size_t GetSpaceUsage() const;
-   void SaveXML(XMLWriter &xmlFile);
+   virtual size_t GetSpaceUsage() const = 0;
 
-private:
-   bool Load(SampleBlockID sbid);
-   bool GetSummary(float *dest,
-                   size_t frameoffset,
-                   size_t numframes,
-                   const char *srccolumn,
-                   size_t srcbytes);
-   size_t GetBlob(void *dest,
-                  sampleFormat destformat,
-                  const char *srccolumn,
-                  sampleFormat srcformat,
-                  size_t srcoffset,
-                  size_t srcbytes);
-   void CalcSummary();
+   virtual void SaveXML(XMLWriter &xmlFile) = 0;
+};
 
-private:
-   ProjectFileIO & mIO;
-   bool mValid;
-   bool mDirty;
-   bool mSilent;
-   int mRefCnt;
+///\brief abstract base class with methods to produce @ref SampleBlock objects
+class SampleBlockFactory
+{
+public:
+   // Install global function that produces a sample block factory object for
+   // a given project; the factory has methods that later make sample blocks.
+   // Return the previously installed factory.
+   static SampleBlockFactoryFactory RegisterFactoryFactory(
+      SampleBlockFactoryFactory newFactory );
 
-   SampleBlockID mBlockID;
+   // Invoke the installed factory (throw an exception if none was installed)
+   static SampleBlockFactoryPtr New( AudacityProject &project );
 
-   ArrayOf<char> mSamples;
-   size_t mSampleBytes;
-   size_t mSampleCount;
-   sampleFormat mSampleFormat;
+   virtual ~SampleBlockFactory();
 
-   ArrayOf<char> mSummary256;
-   size_t mSummary256Bytes;
-   ArrayOf<char> mSummary64k;
-   size_t mSummary64kBytes;
-   double mSumMin;
-   double mSumMax;
-   double mSumRms;
+   virtual SampleBlockPtr Get(SampleBlockID sbid) = 0;
 
-   const char *columns =
-      "sampleformat, summin, summax, sumrms, summary256, summary64k, samples";
+   virtual SampleBlockPtr Create(samplePtr src,
+      size_t numsamples,
+      sampleFormat srcformat) = 0;
 
-#if defined(WORDS_BIGENDIAN)
-#error All sample block data is little endian...big endian not yet supported
-#endif
+   virtual SampleBlockPtr CreateSilent(
+      size_t numsamples,
+      sampleFormat srcformat) = 0;
+
+   virtual SampleBlockPtr CreateFromXML(
+      sampleFormat srcformat,
+      const wxChar **attrs) = 0;
 };
 
 #endif