diff --git a/configure.ac b/configure.ac
index 9d4437d7..226b9dcf 100644
--- a/configure.ac
+++ b/configure.ac
@@ -100,6 +100,7 @@ if test "x$with_libz" = "xyes"; then
     AC_DEFINE([HAVE_ZLIB], [1], [Define to 1 if you have zlib.])
     LIBS="$ZLIB_LIBS $LIBS"
     CPPFLAGS="$ZLIB_CFLAGS $CPPFLAGS"
+    AC_CHECK_FUNCS([gzbuffer gzsetparams])
   else
     AC_MSG_WARN([$ZLIB_PKG_ERRORS])
     if test "x$with_libz_requested" = "xyes"; then
diff --git a/src/BufferedFile.cc b/src/BufferedFile.cc
index d1af1c09..62b8e87d 100644
--- a/src/BufferedFile.cc
+++ b/src/BufferedFile.cc
@@ -59,7 +59,7 @@ BufferedFile::BufferedFile(const char* filename, const char* mode)
 {}
 
 BufferedFile::BufferedFile(FILE* fp)
-  : fp_(fp), open_(true), supportsColor_(fp_ ? isatty(fileno(fp_)) : false)
+  : fp_(fp), open_(fp_), supportsColor_(fp_ ? isatty(fileno(fp_)) : false)
 {}
 
 BufferedFile::~BufferedFile()
@@ -69,7 +69,8 @@ BufferedFile::~BufferedFile()
 
 BufferedFile::operator unspecified_bool_type() const
 {
-  return (!open_ || ferror(fp_)) ? 0 : &BufferedFile::good_state;
+  bool ok = isOpen() && !isError();
+  return ok ? &BufferedFile::good_state : 0;
 }
 
 size_t BufferedFile::read(void* ptr, size_t count)
@@ -94,7 +95,7 @@ char* BufferedFile::gets(char* s, int size)
 
 char* BufferedFile::getsn(char* s, int size)
 {
-  char* ptr = fgets(s, size, fp_);
+  char* ptr = gets(s, size);
   if(ptr) {
     int len = strlen(ptr);
     if(ptr[len-1] == '\n') {
@@ -128,17 +129,16 @@ std::string BufferedFile::getLine()
 
 int BufferedFile::close()
 {
-  if(open_) {
+  if (open_) {
     open_ = false;
     return fclose(fp_);
-  } else {
-    return 0;
   }
+  return 0;
 }
 
 bool BufferedFile::eof()
 {
-  return open_ && feof(fp_);
+  return !isOpen()|| isEOF();
 }
 
 size_t BufferedFile::transfer(std::ostream& out)
diff --git a/src/BufferedFile.h b/src/BufferedFile.h
index f0d78e07..7eb6a36d 100644
--- a/src/BufferedFile.h
+++ b/src/BufferedFile.h
@@ -56,18 +56,18 @@ public:
   // returns false.
   operator unspecified_bool_type() const;
   // wrapper for fread. Using 1 for 2nd argument of fread.
-  size_t read(void* ptr, size_t count);
+  virtual size_t read(void* ptr, size_t count);
   // wrapper for fwrite. Using 1 for 2nd argument of fwrite.
-  size_t write(const void* ptr, size_t count);
+  virtual size_t write(const void* ptr, size_t count);
   virtual size_t write(const char* str);
   // wrapper for fgets
-  char* gets(char* s, int size);
+  virtual char* gets(char* s, int size);
   // wrapper for fgets, but trailing '\n' is replaced with '\0'.
   char* getsn(char* s, int size);
   // Reads one line and returns it. The last '\n' is removed.
   std::string getLine();
   // wrapper for fclose
-  int close();
+  virtual int close();
   // Return true if open_ && feof(fp_) != 0. Otherwise returns false.
   bool eof();
   // Convenient method. Read data to end of file and write them into
@@ -83,15 +83,21 @@ public:
   static const char WRITE[];
   // Mode for append
   static const char APPEND[];
+
 private:
   // Don't allow copying
   BufferedFile(const BufferedFile&);
   BufferedFile& operator=(const BufferedFile&);
 
   FILE* fp_;
-  // true when file has been opened.
   bool open_;
   bool supportsColor_;
+
+protected:
+  virtual bool isError() const { return ferror(fp_); }
+  virtual bool isEOF() const { return feof(fp_); }
+  virtual bool isOpen() const { return open_; }
+
 };
 
 } // namespace aria2
diff --git a/src/GZipFile.cc b/src/GZipFile.cc
new file mode 100644
index 00000000..8acb1bd9
--- /dev/null
+++ b/src/GZipFile.cc
@@ -0,0 +1,161 @@
+/* <!-- copyright */
+/*
+ * aria2 - The high speed download utility
+ *
+ * Copyright (C) 2013 Nils Maier
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * In addition, as a special exception, the copyright holders give
+ * permission to link the code of portions of this program with the
+ * OpenSSL library under certain conditions as described in each
+ * individual source file, and distribute linked combinations
+ * including the two.
+ * You must obey the GNU General Public License in all respects
+ * for all of the code used other than OpenSSL.  If you modify
+ * file(s) with this exception, you may extend this exception to your
+ * version of the file(s), but you are not obligated to do so.  If you
+ * do not wish to do so, delete this exception statement from your
+ * version.  If you delete this exception statement from all source
+ * files in the program, then also delete it here.
+ */
+/* copyright --> */
+
+#include "GZipFile.h"
+
+#include <algorithm>
+#include <limits>
+
+#include "a2io.h"
+#include "util.h"
+
+namespace aria2 {
+
+GZipFile::GZipFile(const char* filename, const char* mode)
+  : BufferedFile(0), fp_(0), open_(false)
+{
+  FILE* fp =
+#ifdef __MINGW32__
+  a2fopen(utf8ToWChar(filename).c_str(), utf8ToWChar(mode).c_str());
+#else // !__MINGW32__
+  a2fopen(filename, mode);
+#endif // !__MINGW32__
+
+  open_  = fp;
+  if (open_) {
+    int fd = dup(fileno(fp));
+    if ((open_ = fd) >= 0) {
+      open_ = (fp_ = gzdopen(fd, mode));
+      if (!open_) {
+        ::close(fd);
+      }
+    }
+    if (open_) {
+#if HAVE_GZBUFFER
+      gzbuffer(fp_, 1<<17);
+#endif
+#if HAVE_GZSETPARAMS
+      gzsetparams(fp_, 2, Z_DEFAULT_STRATEGY);
+#endif
+    }
+    fclose(fp);
+  }
+}
+
+int GZipFile::close()
+{
+  if (open_) {
+    open_ = false;
+    return gzclose(fp_);
+  }
+  return 0;
+}
+
+bool GZipFile::isError() const
+{
+  int rv = 0;
+  const char *e = gzerror(fp_, &rv);
+  return (e != 0 && *e != 0) || rv != 0;
+}
+
+size_t GZipFile::read(void* ptr, size_t count)
+{
+  char *data = reinterpret_cast<char*>(ptr);
+  size_t read = 0;
+  while (count) {
+    size_t len = std::min(count, (size_t)std::numeric_limits<unsigned>::max());
+    int rv = gzread(fp_, data, len);
+    if (rv <= 0) {
+      break;
+    }
+    count -= rv;
+    read += rv;
+    data += rv;
+  }
+  return read;
+}
+
+size_t GZipFile::write(const void* ptr, size_t count)
+{
+  const char *data = reinterpret_cast<const char*>(ptr);
+  size_t written = 0;
+  while (count) {
+    size_t len = std::min(count, (size_t)std::numeric_limits<unsigned>::max());
+    int rv = gzwrite(fp_, data, len);
+    if (rv <= 0) {
+      break;
+    }
+    count -= rv;
+    written += rv;
+    data += rv;
+  }
+  return written;
+}
+
+char* GZipFile::gets(char* s, int size)
+{
+  return gzgets(fp_, s, size);
+}
+
+int GZipFile::flush()
+{
+  return gzflush(fp_, 0);
+}
+
+int GZipFile::vprintf(const char* format, va_list va)
+{
+  char *buf = 0;
+  size_t len;
+
+  int rv = ::vasprintf(&buf, format, va);
+  if (rv <= 0) {
+    // buf is undefined at this point
+    // do not attempt to free it
+    return rv;
+  }
+
+  len = strlen(buf);
+  if (len) {
+    rv = gzwrite(fp_, buf, len);
+  }
+
+  if (buf) {
+    free(buf);
+  }
+  return rv;
+}
+
+
+} // namespace aria2
diff --git a/src/GZipFile.h b/src/GZipFile.h
new file mode 100644
index 00000000..a447dccc
--- /dev/null
+++ b/src/GZipFile.h
@@ -0,0 +1,71 @@
+/* <!-- copyright */
+/*
+ * aria2 - The high speed download utility
+ *
+ * Copyright (C) 2013 Nils Maier
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * In addition, as a special exception, the copyright holders give
+ * permission to link the code of portions of this program with the
+ * OpenSSL library under certain conditions as described in each
+ * individual source file, and distribute linked combinations
+ * including the two.
+ * You must obey the GNU General Public License in all respects
+ * for all of the code used other than OpenSSL.  If you modify
+ * file(s) with this exception, you may extend this exception to your
+ * version of the file(s), but you are not obligated to do so.  If you
+ * do not wish to do so, delete this exception statement from your
+ * version.  If you delete this exception statement from all source
+ * files in the program, then also delete it here.
+ */
+/* copyright --> */
+
+#ifndef D_GZIP_FILE_H
+#define D_GZIP_FILE_H
+
+#include <zlib.h>
+
+#include "BufferedFile.h"
+
+namespace aria2 {
+
+class GZipFile: public BufferedFile {
+public:
+  GZipFile(const char* filename, const char* mode);
+  virtual ~GZipFile() {}
+  virtual int close();
+  virtual size_t read(void* ptr, size_t count);
+  virtual size_t write(const void* ptr, size_t count);
+  virtual char* gets(char* s, int size);
+  virtual int vprintf(const char* format, va_list va);
+  virtual int flush();
+private:
+  // Don't allow copying
+  GZipFile(const GZipFile&);
+  GZipFile& operator=(const GZipFile&);
+
+  gzFile fp_;
+  bool open_;
+
+protected:
+  virtual bool isError() const;
+  virtual bool isEOF() const { return gzeof(fp_); }
+  virtual bool isOpen() const { return open_; }
+};
+
+} // namespace aria2
+
+#endif // D_GZIP_FILE_H
diff --git a/src/Makefile.am b/src/Makefile.am
index 5388ba35..fb5bb20b 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -325,7 +325,8 @@ endif # HAVE_OPENSSL
 
 if HAVE_ZLIB
 SRCS += GZipEncoder.cc GZipEncoder.h\
-	GZipDecodingStreamFilter.cc GZipDecodingStreamFilter.h
+	GZipDecodingStreamFilter.cc GZipDecodingStreamFilter.h\
+	GZipFile.cc GzipFile.h
 endif # HAVE_ZLIB
 
 if HAVE_SQLITE3
diff --git a/src/SessionSerializer.cc b/src/SessionSerializer.cc
index 519cf338..6c4832f5 100644
--- a/src/SessionSerializer.cc
+++ b/src/SessionSerializer.cc
@@ -52,6 +52,10 @@
 #include "OptionParser.h"
 #include "OptionHandler.h"
 
+#if HAVE_ZLIB
+#include "GZipFile.h"
+#endif
+
 namespace aria2 {
 
 SessionSerializer::SessionSerializer
@@ -66,11 +70,20 @@ bool SessionSerializer::save(const std::string& filename) const
   std::string tempFilename = filename;
   tempFilename += "__temp";
   {
-    BufferedFile fp(tempFilename.c_str(), BufferedFile::WRITE);
-    if(!fp) {
+    SharedHandle<BufferedFile> fp;
+#if HAVE_ZLIB
+    if (filename.compare(filename.length() - 3, 3, ".gz") == 0) {
+      fp.reset(new GZipFile(tempFilename.c_str(), BufferedFile::WRITE));
+    }
+    else
+#endif
+    {
+     fp.reset(new BufferedFile(tempFilename.c_str(), BufferedFile::WRITE));
+    }
+    if(!fp || !*fp) {
       return false;
     }
-    if(!save(fp) || fp.close() == EOF) {
+    if(!save(*fp) || fp->close() == EOF) {
       return false;
     }
   }
@@ -92,12 +105,36 @@ bool writeOption(BufferedFile& fp, const SharedHandle<Option>& op)
                     false, false);
         for(std::vector<std::string>::const_iterator j = v.begin(),
               eoj = v.end(); j != eoj; ++j) {
-          if(fp.printf(" %s=%s\n", pref->k, (*j).c_str()) < 0) {
+          if (fp.write(" ", 1) != 1) {
+            return false;
+          }
+          if (fp.write(pref->k) == 0) {
+            return false;
+          }
+          if (fp.write("=", 1) != 1) {
+            return false;
+          }
+          if (!j->empty() && fp.write(j->c_str()) == 0) {
+            return false;
+          }
+          if (fp.write("\n", 1) != 1) {
             return false;
           }
         }
       } else {
-        if(fp.printf(" %s=%s\n", pref->k, op->get(pref).c_str()) < 0) {
+        if (fp.write(" ", 1) != 1) {
+          return false;
+        }
+        if (fp.write(pref->k) == 0) {
+          return false;
+        }
+        if (fp.write("=", 1) != 1) {
+          return false;
+        }
+        if (fp.write(op->get(pref).c_str()) == 0) {
+          return false;
+        }
+        if (fp.write("\n", 1) != 1) {
           return false;
         }
       }
@@ -152,14 +189,17 @@ bool writeDownloadResult
     }
     for(std::vector<std::string>::const_iterator i = uris.begin(),
           eoi = uris.end(); i != eoi; ++i) {
-      if(fp.printf("%s\t", (*i).c_str()) < 0) {
+      if (fp.write(i->c_str()) == 0 || fp.write("\t", 1) != 1) {
         return false;
       }
     }
-    if(fp.write("\n", 1) != 1) {
+    if(fp.write("\n gid=", 6) != 6) {
       return false;
     }
-    if(fp.printf(" gid=%s\n", dr->gid->toHex().c_str()) < 0) {
+    if(fp.write(dr->gid->toHex().c_str()) == 0) {
+       return false;
+    }
+    if(fp.write("\n", 1) != 1) {
       return false;
     }
   } else {
@@ -167,12 +207,12 @@ bool writeDownloadResult
       return true;
     } else {
       metainfoCache.insert(mi->getGID());
-      if(fp.printf("%s\n", mi->getUri().c_str()) < 0) {
+      if (fp.write(mi->getUri().c_str()) == 0 || fp.write("\n", 1) != 1) {
         return false;
       }
       // For downloads generated by metadata (e.g., BitTorrent,
       // Metalink), save gid of Metadata download.
-      if(fp.printf(" gid=%s\n", GroupId::toHex(mi->getGID()).c_str()) < 0) {
+      if (fp.write(" gid=", 5) != 5 || fp.write(GroupId::toHex(mi->getGID()).c_str()) == 0 || fp.write("\n", 1) != 1) {
         return false;
       }
     }
@@ -241,7 +281,7 @@ bool SessionSerializer::save(BufferedFile& fp) const
       // PREF_PAUSE was removed from option, so save it here looking
       // property separately.
       if(rg->isPauseRequested()) {
-        if(fp.printf(" %s=true\n", PREF_PAUSE->k) < 0) {
+        if (fp.write(" ", 1) != 1 || fp.write(PREF_PAUSE->k) == 0 || fp.write("\n", 1) != 1) {
           return false;
         }
       }
diff --git a/src/UriListParser.cc b/src/UriListParser.cc
index 5578bad7..5af1a473 100644
--- a/src/UriListParser.cc
+++ b/src/UriListParser.cc
@@ -45,10 +45,18 @@
 #include "BufferedFile.h"
 #include "OptionParser.h"
 
+#if HAVE_ZLIB
+#include "GZipFile.h"
+#endif
+
 namespace aria2 {
 
 UriListParser::UriListParser(const std::string& filename)
-  : fp_(filename.c_str(), BufferedFile::READ)
+#if HAVE_ZLIB
+  : fp_(new GZipFile(filename.c_str(), BufferedFile::READ))
+#else
+  : fp_(new BufferedFile(filename.c_str(), BufferedFile::READ))
+#endif
 {}
 
 UriListParser::~UriListParser() {}
@@ -63,9 +71,9 @@ void UriListParser::parseNext(std::vector<std::string>& uris, Option& op)
       // Read options
       std::stringstream ss;
       while(1) {
-        line_ = fp_.getLine();
+        line_ = fp_->getLine();
         if(line_.empty()) {
-          if(fp_.eof()) {
+          if(fp_->eof()) {
             break;
           } else if(!fp_) {
             throw DL_ABORT_EX("UriListParser:I/O error.");
@@ -84,9 +92,9 @@ void UriListParser::parseNext(std::vector<std::string>& uris, Option& op)
       optparser->parse(op, ss);
       return;
     }
-    line_ = fp_.getLine();
+    line_ = fp_->getLine();
     if(line_.empty()) {
-      if(fp_.eof()) {
+      if(fp_->eof()) {
         return;
       } else if(!fp_) {
         throw DL_ABORT_EX("UriListParser:I/O error.");
@@ -97,7 +105,11 @@ void UriListParser::parseNext(std::vector<std::string>& uris, Option& op)
 
 bool UriListParser::hasNext()
 {
-  return !line_.empty() || (fp_ && !fp_.eof());
+  bool rv = !line_.empty() || (fp_ && *fp_ && !fp_->eof());
+  if (!rv) {
+    fp_->close();
+  }
+  return rv;
 }
 
 } // namespace aria2
diff --git a/src/UriListParser.h b/src/UriListParser.h
index 24c7dfb3..976fa665 100644
--- a/src/UriListParser.h
+++ b/src/UriListParser.h
@@ -43,12 +43,13 @@
 
 #include "Option.h"
 #include "BufferedFile.h"
+#include "SharedHandle.h"
 
 namespace aria2 {
 
 class UriListParser {
 private:
-  BufferedFile fp_;
+  SharedHandle<BufferedFile> fp_;
 
   std::string line_;
 public:
diff --git a/test/Makefile.am b/test/Makefile.am
index 3b7a7790..2231fe45 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -3,7 +3,6 @@ TESTS = aria2c
 check_PROGRAMS = $(TESTS)
 aria2c_SOURCES = AllTest.cc\
 	TestUtil.cc TestUtil.h\
-	GZipDecoder.cc GZipDecoder.h\
 	SocketCoreTest.cc\
 	array_funTest.cc\
 	Base64Test.cc\
@@ -100,8 +99,9 @@ aria2c_SOURCES += FallocFileAllocationIteratorTest.cc
 endif  # HAVE_SOME_FALLOCATE
 
 if HAVE_ZLIB
-aria2c_SOURCES += GZipDecoderTest.cc\
-	GZipEncoderTest.cc\
+aria2c_SOURCES += \
+	GZipDecoder.cc GZipDecoder.h\
+	GZipDecoderTest.cc GZipEncoderTest.cc\
 	GZipDecodingStreamFilterTest.cc
 endif # HAVE_ZLIB
 
@@ -281,4 +281,4 @@ EXTRA_DIST = 4096chunk.txt\
 	base_uri.xml
 
 clean-local:
-	-rm -rf ${a2_test_outdir}
\ No newline at end of file
+	-rm -rf ${a2_test_outdir}