Re: Patch for Review: _Jv_TempUTFString + JV_TEMP_UTF_STRING

[Mohan Embar <gnustuff at thisiscool dot com>]

Hi Bryce,

>> Here is the patch, rewritten to use the existing CNI functions.
>> To recap this supersedes and nullifies the cni.h + gcj.texi
>> patches as well as all other jvm.h patches.
>
>I'd still like to see it use JvAllocBytes instead of _Jv_Malloc. That 
>way you can get rid of the destructor and the "heapAllocated" field. 
>Even if it were slower, which it isn't, it will only be used in the 
>rare cases where the string is > 256 bytes.

I modified the testcase (attached) to do create a gazillion instances.
You invoke the test program with -stresstest, pipe stdout to some file
and read stderr on the console.

Here are my invocations on Linux (P450/256M/10G):

./TempUTFStrTest -stresstest > stress.out

and Windows XP (P733/1G/80G):

TempUTFStrTest.exe -stresstest > d:\temp\stress.out

I ran these tests four times on each platform with the unmodified jvm.h
in the patch I just submitted (http://gcc.gnu.org/ml/java-patches/2003-q3/msg00390.html)
as well as with a jvm.h modified as per the end of this email message.

Here are the reported timings:

Linux w/_Jv_AllocBytes():
22489
20609
22161
22397

Win32 w/_Jv_AllocBytes():
84692
85403
86444
86685

(Yes, I know my WinXP box is misconfigured. Maybe I need to enable 32 bit access for my HD...)

Linux w/_Jv_Malloc():
20250
14155
17221
21747

Win32 w/_Jv_Malloc():
72604
73205
73315
72385

Let me know if I'm doing something wrong or if your results differ.

-- Mohan
http://www.thisiscool.com/
http://www.animalsong.org/

--> jvm.h Modified for _Jv_AllocBytes()

---------------------------------------------------8<------------------------------------------------------------
Index: include/jvm.h
===================================================================
RCS file: /cvsroot/gcc/gcc/libjava/include/jvm.h,v
retrieving revision 1.56
diff -u -2 -r1.56 jvm.h
--- include/jvm.h	21 Jul 2003 01:54:05 -0000	1.56
+++ include/jvm.h	15 Aug 2003 04:25:48 -0000
@@ -245,4 +245,80 @@
 		  bool is_jar);
 
+/* Helper class which converts a jstring to a temporary char*.
+   Uses the supplied buffer, if non-null. Otherwise, allocates
+   the buffer on the heap. Use the JV_TEMP_UTF_STRING macro,
+   which follows, to automatically allocate a stack buffer if
+   the string is small enough. */
+class _Jv_TempUTFString
+{
+public:
+  _Jv_TempUTFString(jstring jstr, char* buf=0);
+  ~_Jv_TempUTFString();
+
+// Accessors
+  operator const char*() const
+  {
+    return buf_;
+  }
+  const char* buf() const
+  {
+    return buf_;
+  }
+  char* buf()
+  {
+    return buf_;
+  }
+
+private:
+  char* buf_;
+  bool heapAllocated_;
+};
+
+inline _Jv_TempUTFString::_Jv_TempUTFString (jstring jstr, char* buf)
+  : buf_(0), heapAllocated_(false)
+{
+  if (!jstr) return;
+  jsize len = JvGetStringUTFLength (jstr);
+  if (buf)
+    buf_ = buf;
+  else
+    {
+//    buf_ = (char*) _Jv_Malloc (len+1);
+      buf_ = (char*) _Jv_AllocBytes (len+1);
+//    heapAllocated_ = true;
+    }
+
+  JvGetStringUTFRegion (jstr, 0, jstr->length(), buf_);
+  buf_[len] = '\0';
+}
+
+inline _Jv_TempUTFString::~_Jv_TempUTFString ()
+{
+/*
+  if (heapAllocated_)
+    _Jv_Free (buf_);
+*/
+}
+
+/* Macro which uses _Jv_TempUTFString. Allocates a stack-based
+   buffer if the string and its null terminator are <= 256
+   characters in length. Otherwise, a heap-based buffer is
+   used. The parameters to this macro are the variable name
+   which is an instance of _Jv_TempUTFString (above) and a
+   jstring.
+   
+   Sample Usage:
+   
+   jstring jstr = getAJString();
+   JV_TEMP_UTF_STRING(utfstr, jstr);
+   printf("The string is: %s\n", utfstr.buf());
+   
+ */
+#define JV_TEMP_UTF_STRING(utfstr, jstr) \
+  jstring utfstr##thejstr = (jstr); \
+  jsize utfstr##_len = utfstr##thejstr ? JvGetStringUTFLength (utfstr##thejstr) + 1 : 0; \
+  char utfstr##_buf[utfstr##_len <= 256 ? utfstr##_len : 0]; \
+  _Jv_TempUTFString utfstr(utfstr##thejstr, sizeof(utfstr##_buf)==0 ? 0 : utfstr##_buf)
+
 // Delayed until after _Jv_AllocBytes is declared.
 //
---------------------------------------------------8<------------------------------------------------------------

Attachment: TempUTFStrTest.tar.bz2
Description: application/bzip2