diff --git a/ChangeLog b/ChangeLog
index b47e7bc5..1fc92ec3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2009-11-22  Tatsuhiro Tsujikawa  <t-tujikawa@users.sourceforge.net>
+
+	Added FromHex()
+	* src/util.cc
+	* src/util.h
+	* test/UtilTest.cc
+
 2009-11-22  Tatsuhiro Tsujikawa  <t-tujikawa@users.sourceforge.net>
 
 	Added _metadataGetMode member variable. It toggles the action when
diff --git a/src/util.cc b/src/util.cc
index bf13e526..308d2660 100644
--- a/src/util.cc
+++ b/src/util.cc
@@ -298,6 +298,41 @@ std::string toHex(const std::string& src)
   return toHex(reinterpret_cast<const unsigned char*>(src.c_str()), src.size());
 }
 
+static unsigned int hexCharToUInt(unsigned char ch)
+{
+
+  if('a' <= ch && ch <= 'f') {
+    ch -= 'a';
+    ch += 10;
+  } else if('A' <= ch && ch <= 'F') {
+    ch -= 'A';
+    ch += 10;
+  } else if('0' <= ch && ch <= '9') {
+    ch -= '0';
+  } else {
+    ch = 255;
+  }
+  return ch;
+}
+
+std::string fromHex(const std::string& src)
+{
+  std::string dest;
+  if(src.size()%2) {
+    return dest;
+  }
+  for(size_t i = 0; i < src.size(); i += 2) {
+      unsigned char high = hexCharToUInt(src[i]);
+      unsigned char low = hexCharToUInt(src[i+1]);
+      if(high == 255 || low == 255) {
+	dest.clear();
+	return dest;
+      }
+      dest += (high*16+low);
+  }
+  return dest;
+}
+
 FILE* openFile(const std::string& filename, const std::string& mode) {
   FILE* file = fopen(filename.c_str(), mode.c_str());
   return file;
diff --git a/src/util.h b/src/util.h
index 9ab0e70e..3db8c31a 100644
--- a/src/util.h
+++ b/src/util.h
@@ -170,6 +170,11 @@ std::string toHex(const char* src, size_t len);
 
 std::string toHex(const std::string& src);
 
+// Converts hexadecimal ascii string 'src' into packed binary form and
+// return the result. If src is not well formed, then empty string is
+// returned.
+std::string fromHex(const std::string& src);
+
 FILE* openFile(const std::string& filename, const std::string& mode);
 
 bool isPowerOf(int num, int base);
diff --git a/test/UtilTest.cc b/test/UtilTest.cc
index b27e6181..bb1f958f 100644
--- a/test/UtilTest.cc
+++ b/test/UtilTest.cc
@@ -56,6 +56,7 @@ class UtilTest:public CppUnit::TestFixture {
   CPPUNIT_TEST(testParseIndexPath);
   CPPUNIT_TEST(testCreateIndexPathMap);
   CPPUNIT_TEST(testGenerateRandomData);
+  CPPUNIT_TEST(testFromHex);
   CPPUNIT_TEST_SUITE_END();
 private:
 
@@ -100,6 +101,7 @@ public:
   void testParseIndexPath();
   void testCreateIndexPathMap();
   void testGenerateRandomData();
+  void testFromHex();
 };
 
 
@@ -800,4 +802,23 @@ void UtilTest::testGenerateRandomData()
   CPPUNIT_ASSERT(memcmp(data1, data2, sizeof(data1)) != 0);
 }
 
+void UtilTest::testFromHex()
+{
+  std::string src;
+  std::string dest;
+
+  src = "0011fF";
+  dest = util::fromHex(src);
+  CPPUNIT_ASSERT_EQUAL((size_t)3, dest.size());
+  CPPUNIT_ASSERT_EQUAL((char)0x00, dest[0]);
+  CPPUNIT_ASSERT_EQUAL((char)0x11, dest[1]);
+  CPPUNIT_ASSERT_EQUAL((char)0xff, dest[2]);
+
+  src = "0011f";
+  CPPUNIT_ASSERT(util::fromHex(src).empty());
+
+  src = "001g";
+  CPPUNIT_ASSERT(util::fromHex(src).empty());
+}
+
 } // namespace aria2