2 files changed, 247 insertions, 37 deletions

diff --git a/src/fstring.h b/src/fstring.h
index 287641f..db54cdd 100644
--- a/src/fstring.h
+++ b/src/fstring.h
@@ -20,6 +20,7 @@ class FBasicString
 {
 private:
         typedef struct FStringChunk<chr> Chunk;
+        typedef struct FBasicString<chr, chralloc, chunkalloc> MyType;
 
 public:
         FBasicString() :
@@ -48,8 +49,31 @@ public:
                 append( pData, nLength );
         }
 
+        FBasicString( MyType &rSrc ) :
+                nLength( 0 ),
+                pnRefs( NULL ),
+                pFirst( NULL ),
+                pLast( NULL )
+        {
+                joinShare( rSrc );
+        }
+
+        FBasicString( const FBasicString<chr, chralloc, chunkalloc> &rSrc ) :
+                nLength( 0 ),
+                pnRefs( NULL ),
+                pFirst( NULL ),
+                pLast( NULL )
+        {
+                // Here we have no choice but to copy, since the other guy is a const.
+                // In the case that the source were flat, we could get a reference, it
+                // would make some things faster, but not matter in many other cases.
+
+                copyFrom( rSrc );
+        }
+
         virtual ~FBasicString()
         {
+                clear();
         }
 
         void append( const chr *pData )
@@ -58,7 +82,7 @@ public:
                 for( nLen = 0; pData[nLen] != (chr)0; nLen++ );
                 
                 Chunk *pNew = newChunk( nLen );
-                memcpy( pNew->pData, pData, nLen * sizeof(chr) );
+                cpy( pNew->pData, pData, nLen );
 
                 appendChunk( pNew );
         }
@@ -67,7 +91,7 @@ public:
         {
                 Chunk *pNew = newChunk( nLen );
                 
-                memcpy( pNew->pData, pData, nLen * sizeof(chr) );
+                cpy( pNew->pData, pData, nLen );
 
                 appendChunk( pNew );
         }
@@ -78,7 +102,7 @@ public:
                 for( nLen = 0; pData[nLen] != (chr)0; nLen++ );
                 
                 Chunk *pNew = newChunk( nLen );
-                memcpy( pNew->pData, pData, nLen * sizeof(chr) );
+                cpy( pNew->pData, pData, nLen );
 
                 prependChunk( pNew );
         }
@@ -87,7 +111,7 @@ public:
         {
                 Chunk *pNew = newChunk( nLen );
                 
-                memcpy( pNew->pData, pData, nLen * sizeof(chr) );
+                cpy( pNew->pData, pData, nLen );
 
                 prependChunk( pNew );
         }
@@ -97,18 +121,25 @@ public:
                 if( pFirst == NULL )
                         return;
 
-                Chunk *i = pFirst;
-                for(;;)
+                if( isShared() )
                 {
-                        Chunk *n = i->pNext;
-                        aChr.deallocate( i->pData, i->nLength+1 );
-                        aChunk.deallocate( i, 1 );
-                        if( n == NULL )
-                                break;
-                        i = n;
+                        decRefs();
+                }
+                else
+                {
+                        Chunk *i = pFirst;
+                        for(;;)
+                        {
+                                Chunk *n = i->pNext;
+                                aChr.deallocate( i->pData, i->nLength+1 );
+                                aChunk.deallocate( i, 1 );
+                                if( n == NULL )
+                                        break;
+                                i = n;
+                        }
+                        pFirst = pLast = NULL;
+                        nLength = 0;
                 }
-                pFirst = pLast = NULL;
-                nLength = 0;
         }
 
         chr *c_str()
@@ -120,14 +151,14 @@ public:
                 return pFirst->pData;
         }
 
-        FBasicString<chr, chralloc, chunkalloc> &operator +=( const chr *pData )
+        MyType &operator +=( const chr *pData )
         {
                 append( pData );
 
                 return (*this);
         }
 
-        FBasicString<chr, chralloc, chunkalloc> &operator =( const chr *pData )
+        MyType &operator =( const chr *pData )
         {
                 clear();
                 append( pData );
@@ -135,6 +166,27 @@ public:
                 return (*this);
         }
 
+        MyType &operator =( const MyType &rSrc )
+        {
+                if( rSrc.isFlat() )
+                {
+                        joinShare( rSrc );
+                }
+                else
+                {
+                        copyFrom( rSrc );
+                }
+
+                return (*this);
+        }
+        
+        MyType &operator =( MyType &rSrc )
+        {
+                joinShare( rSrc );
+
+                return (*this);
+        }
+
         bool operator ==( const chr *pData )
         {
                 if( pFirst == NULL ) {
@@ -160,7 +212,12 @@ public:
                 return !(*this == pData);
         }
 
+        chr &operator[]( long nIndex )
+        {
+                flatten();
 
+                return pFirst->pData[nIndex];
+        }
 
 private:
         void flatten()
@@ -171,12 +228,37 @@ private:
                 if( pFirst == NULL )
                         return;
 
+                unShare();
+
                 Chunk *pNew = newChunk( nLength );
                 chr *pos = pNew->pData;
                 Chunk *i = pFirst;
                 for(;;)
                 {
-                        memcpy( pos, i->pData, i->nLength*sizeof(chr) );
+                        cpy( pos, i->pData, i->nLength );
+                        pos += i->nLength;
+                        i = i->pNext;
+                        if( i == NULL )
+                                break;
+                }
+                clear();
+
+                appendChunk( pNew );
+        }
+        
+        void copyFrom( const FBasicString<chr, chralloc, chunkalloc> &rSrc )
+        {
+                if( rSrc.pFirst == NULL )
+                        return;
+                
+                decRefs();
+
+                Chunk *pNew = newChunk( rSrc.nLength );
+                chr *pos = pNew->pData;
+                Chunk *i = rSrc.pFirst;
+                for(;;)
+                {
+                        cpy( pos, i->pData, i->nLength );
                         pos += i->nLength;
                         i = i->pNext;
                         if( i == NULL )
@@ -187,12 +269,12 @@ private:
                 appendChunk( pNew );
         }
         
-        bool isFlat()
+        bool isFlat() const
         {
                 return (pFirst == pLast);
         }
 
-        bool isShared()
+        bool isShared() const
         {
                 return (pnRefs != NULL);
         }
@@ -210,11 +292,14 @@ private:
                 pNew->pNext = NULL;
                 pNew->nLength = nLen;
                 pNew->pData = aChr.allocate( nLen+1 );
+                pNew->pData[nLen] = (chr)0;
                 return pNew;
         }
 
         void appendChunk( Chunk *pNewChunk )
         {
+                unShare();
+
                 if( pFirst == NULL )
                         pLast = pFirst = pNewChunk;
                 else
@@ -228,6 +313,8 @@ private:
         
         void prependChunk( Chunk *pNewChunk )
         {
+                unShare();
+
                 if( pFirst == NULL )
                         pLast = pFirst = pNewChunk;
                 else
@@ -239,9 +326,123 @@ private:
                 nLength += pNewChunk->nLength;
         }
 
+        void joinShare( MyType &rSrc )
+        {
+                clear();
+
+                if( !rSrc.isFlat() )
+                        rSrc.flatten();
+
+                rSrc.initCount();
+                pnRefs = rSrc.pnRefs;
+                (*pnRefs)++;
+                nLength = rSrc.nLength;
+                pFirst = rSrc.pFirst;
+                pLast = rSrc.pLast;
+        }
+        
+        void joinShare( const MyType &rSrc )
+        {
+                clear();
+
+                if( !rSrc.isFlat() )
+                        return;
+
+                if( !rSrc.isShared() )
+                {
+                        rSrc.pnRefs = new uint32_t;
+                        (*rSrc.pnRefs) = 1;
+                }
+                pnRefs = rSrc.pnRefs;
+                (*pnRefs)++;
+                nLength = rSrc.nLength;
+                pFirst = rSrc.pFirst;
+                pLast = rSrc.pLast;
+        }
+
+        /**
+         * This takes an object that was shared and makes a copy of the base data
+         * that was being shared so that this copy can be changed.  This should be
+         * added before any call that will change this object;
+         */
+        void unShare()
+        {
+                if( isShared() == false )
+                        return;
+
+                Chunk *pNew = newChunk( nLength );
+                chr *pos = pNew->pData;
+                Chunk *i = pFirst;
+                for(;;)
+                {
+                        cpy( pos, i->pData, i->nLength );
+                        pos += i->nLength;
+                        i = i->pNext;
+                        if( i == NULL )
+                                break;
+                }
+                decRefs();
+                appendChunk( pNew );
+                decRefs();
+        }
+
+        /**
+         * This decrements our ref count and pulls us out of the share.  If the ref
+         * count hits zero because of this, it destroys the share.  This is not
+         * safe to call on it's own, it's much better to call unShare.
+         */
+        void decRefs()
+        {
+                if( isShared() )
+                {
+                        (*pnRefs)--;
+                        if( (*pnRefs) == 0 )
+                                destroyShare();
+                        else
+                        {
+                                pnRefs = NULL;
+                                pFirst = NULL;
+                                pLast = NULL;
+                                nLength = 0;
+                        }
+                }
+        }
+
+        /**
+         * While the unShare function removes an instance from a share, this
+         * function destroys the data that was in the share, removing the share
+         * itself.  This should only be called when the refcount for the share has
+         * or is about to reach zero.
+         */
+        void destroyShare()
+        {
+                delete pnRefs;
+                pnRefs = NULL;
+                clear();
+        }
+
+        void cpy( chr *dest, const chr *src, long count )
+        {
+                for( int j = 0; j < count; j++ )
+                {
+                        *dest = *src;
+                        dest++;
+                        src++;
+                }
+        }
+
+        void initCount() const
+        {
+                if( !isShared() )
+                {
+                        pnRefs = new uint32_t;
+                        (*pnRefs) = 1;
+                }
+        }
+
 private:
         long nLength;
-        uint32_t *pnRefs;
+        mutable uint32_t *pnRefs;
         Chunk *pFirst;
         Chunk *pLast;
 
diff --git a/src/tests/fstring.cpp b/src/tests/fstring.cpp
index 26905ac..cb85282 100644
--- a/src/tests/fstring.cpp
+++ b/src/tests/fstring.cpp
@@ -1,28 +1,37 @@
 #include "fstring.h"
 
-int main( int argc, char *argv )
+FString genThing()
 {
-        FString str("[] this won't be in there", 3);
-
-        str.append("Hello");
-        str.append(" th");
-        str.append("ere.");
+        FString bob;
+        bob.append("ab ");
+        bob += "cd ";
+        bob += "efg";
 
-        if( str == "[] Hello there." )
-                printf("1) check\n");
+    printf("---bob------\n%08X: %s\n", (unsigned int)bob.c_str(), bob.c_str() );
+        return bob;
+}
 
-        if( str != "[] Hello there. " )
-                printf("2) check\n");
+#define pem printf("---------\n%08X: %s\n%08X: %s\n", (unsigned int)str.c_str(), str.c_str(), (unsigned int)str2.c_str(), str2.c_str() );
+int main( int argc, char *argv )
+{
+        FString str("th");
 
-        if( str != "[] Hello there." )
-                printf("3) failed\n");
-        else
-                printf("3) check\n");
+        str.prepend("Hello ");
+        str.append("ere.");
 
-        str += "  How are you?";
+        FString str2( str );
+        pem;
+        str += "  What's up?";
+        pem;
+        str2 += "  How are you?";
+        pem;
+        str = str2;
+        pem;
 
-        str.prepend("Bob says:  ");
+        str2 = genThing();
+        pem;
 
-        printf("%s\n", str.c_str() );
+        str = str2;
+        pem;
 }