making nsXPIDLString's NULL property equate to nsAString's IsVoid property,

discussed this change with dbaron and jst.
adding testcases for nsXPIDLString


git-svn-id: svn://10.0.0.236/branches/STRING_20040119_BRANCH@152401 18797224-902f-48f8-a5cc-f745e15eee43

mozilla/xpcom/string/public/nsTAString.h

@@ -298,7 +298,7 @@ class nsTAString_CharT
         /**
          * optional ctor for use by subclasses.
          *
-         * mData and mLength are intentionally left uninitialized.
+         * NOTE: mData and mLength are intentionally left uninitialized.
          */
       explicit
       nsTAString_CharT(PRUint32 flags)

mozilla/xpcom/string/public/nsTString.h

@@ -525,6 +525,13 @@ class nsTAutoString_CharT : public nsTString_CharT
   };
 
 
+  /**
+   * nsTXPIDLString extends nsTString such that:
+   *
+   *   (1) mData can be null
+   *   (2) objects of this type can be automatically cast to |const CharT*|
+   *   (3) getter_Copies method is supported to adopt data
+   */
 class nsTXPIDLString_CharT : public nsTString_CharT
   {
     public:
@@ -534,11 +541,20 @@ class nsTXPIDLString_CharT : public nsTString_CharT
     public:
 
       nsTXPIDLString_CharT()
-        : string_type(nsnull, 0, 0) {}
+        : string_type(NS_CONST_CAST(char_type*, char_traits::sEmptyBuffer), 0, F_TERMINATED | F_VOIDED) {}
 
         // copy-constructor required to avoid default
       nsTXPIDLString_CharT( const self_type& str )
-        : string_type(str) {}
+        : string_type(NS_CONST_CAST(char_type*, char_traits::sEmptyBuffer), 0, F_TERMINATED | F_VOIDED)
+        {
+          Assign(str);
+        }
+
+        // return nsnull if we are voided
+      const char_type* get() const
+        {
+          return (mFlags & F_VOIDED) ? nsnull : mData;
+        }
 
         // this case operator is the reason why this class cannot just be a
         // typedef for nsTString

mozilla/xpcom/string/public/nsTSubstring.h

@@ -362,6 +362,6 @@ class nsTSubstring_CharT : public nsTAString_CharT
           F_VOIDED     = 1 << 1,  // IsVoid returns true
           F_SHARED     = 1 << 2,  // mData[0] is prefixed with additional fields
           F_OWNED      = 1 << 3,  // mData is owned by this class
-          F_FIXED      = 1 << 4   // mData is pointing at nsTAutoString::mFixedBuf
+          F_FIXED      = 1 << 4   // mData is pointing at a fixed-size writable buffer
         };
   };

mozilla/xpcom/string/src/nsTSubstring.cpp

@@ -117,7 +117,7 @@ nsTSubstring_CharT::MutatePrep( size_type capacity, char_type** oldData, PRUint3
     *oldFlags = mFlags;
 
     mData = newData;
-    mFlags = (F_TERMINATED | F_SHARED);
+    mFlags = F_TERMINATED | F_SHARED;
 
     // mLength does not change
 
@@ -240,7 +240,7 @@ nsTSubstring_CharT::EnsureMutable()
 void
 nsTSubstring_CharT::Assign( const char_type* data, size_type length )
   {
-      // unfortunately, people do pass null sometimes :(
+      // unfortunately, some callers pass null :-(
     if (!data)
       {
         Truncate();
@@ -281,11 +281,16 @@ nsTSubstring_CharT::Assign( const self_type& str )
 
         mData = str.mData;
         mLength = str.mLength;
-        mFlags = (F_TERMINATED | F_SHARED);
+        mFlags = F_TERMINATED | F_SHARED;
 
         // get an owning reference to the mData
         nsStringHeader::FromData(mData)->AddRef();
       }
+    else if (str.mFlags & F_VOIDED)
+      {
+        // inherit the F_VOIDED attribute
+        SetIsVoid(PR_TRUE);
+      }
     else
       {
         // else, treat this like an ordinary assignment.
@@ -325,21 +330,22 @@ nsTSubstring_CharT::Assign( const abstract_string_type& readable )
 void
 nsTSubstring_CharT::Adopt( char_type* data, size_type length )
   {
-    ::ReleaseData(mData, mFlags);
-    mData = data;
-    if (mData)
+    if (data)
       {
+        ::ReleaseData(mData, mFlags);
+
         if (length == size_type(-1))
           length = char_traits::length(data);
+
+        mData = data;
         mLength = length;
-        mFlags = (F_TERMINATED | F_OWNED);
+        mFlags = F_TERMINATED | F_OWNED;
 
         STRING_STAT_INCREMENT(Adopt);
       }
     else
       {
-        mLength = 0;
-        mFlags = 0;
+        SetIsVoid(PR_TRUE);
       }
   }
 

mozilla/xpcom/tests/TestStrings.cpp

@@ -37,6 +37,7 @@
 
 #include <stdio.h>
 #include "nsString.h"
+#include "nsCRT.h"
 
 void test_assign_helper(const nsACString& in, nsACString &_retval)
   {
@@ -256,6 +257,56 @@ PRBool test_concat_2()
     return PR_FALSE;
   }
 
+PRBool test_xpidl_string()
+  {
+    nsXPIDLCString a, b;
+    a = b;
+    if (a != b)
+      return PR_FALSE;
+
+    a.Adopt(0);
+    if (a != b)
+      return PR_FALSE;
+
+    a.Append("foopy");
+    a.Assign(b);
+    if (a != b)
+      return PR_FALSE;
+
+    a.Insert("", 0);
+    a.Assign(b);
+    if (a != b)
+      return PR_FALSE;
+
+    const char text[] = "hello world";
+    *getter_Copies(a) = nsCRT::strdup(text);
+    if (strcmp(a, text) != 0)
+      return PR_FALSE;
+
+    b = a;
+    if (strcmp(a, b) != 0)
+      return PR_FALSE;
+
+    a.Adopt(0);
+    nsACString::const_iterator begin, end;
+    a.BeginReading(begin);
+    a.EndReading(end);
+    char *r = ToNewCString(Substring(begin, end));
+    if (strcmp(r, "") != 0)
+      return PR_FALSE;
+    nsMemory::Free(r);
+
+    a.Adopt(0);
+    if (a != (const char*) 0)
+      return PR_FALSE;
+
+    PRInt32 index = a.FindCharInSet("xyz");
+    if (index != kNotFound)
+      return PR_FALSE;
+
+    return PR_TRUE;
+  }
+
 //----
 
 typedef PRBool (*TestFunc)();
@@ -284,6 +335,7 @@ tests[] =
     { "test_cbufdesc", test_cbufdesc },
     { "test_concat", test_concat },
     { "test_concat_2", test_concat_2 },
+    { "test_xpidl_string", test_xpidl_string },
     { nsnull, nsnull }
   };