diff --git a/_example/mod_vtable/Makefile b/_example/mod_vtable/Makefile
new file mode 100644
index 0000000..cdd4853
--- /dev/null
+++ b/_example/mod_vtable/Makefile
@@ -0,0 +1,24 @@
+ifeq ($(OS),Windows_NT)
+EXE=extension.exe
+EXT=sqlite3_mod_vtable.dll
+RM=cmd /c del
+LIBCURL=-lcurldll
+LDFLAG=
+else
+EXE=extension
+EXT=sqlite3_mod_vtable.so
+RM=rm
+LDFLAG=-fPIC
+LIBCURL=-lcurl
+endif
+
+all : $(EXE) $(EXT)
+
+$(EXE) : extension.go
+	go build $<
+
+$(EXT) : sqlite3_mod_vtable.cc
+	g++ $(LDFLAG) -shared -o $@ $< -lsqlite3 $(LIBCURL)
+
+clean :
+	@-$(RM) $(EXE) $(EXT)
diff --git a/_example/mod_vtable/extension.go b/_example/mod_vtable/extension.go
new file mode 100644
index 0000000..69ae2c7
--- /dev/null
+++ b/_example/mod_vtable/extension.go
@@ -0,0 +1,36 @@
+package main
+
+import (
+	"database/sql"
+	"fmt"
+	"github.com/mattn/go-sqlite3"
+	"log"
+)
+
+func main() {
+	sql.Register("sqlite3_with_extensions",
+		&sqlite3.SQLiteDriver{
+			Extensions: []string{
+				"sqlite3_mod_vtable",
+			},
+		})
+
+	db, err := sql.Open("sqlite3_with_extensions", ":memory:")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer db.Close()
+
+	db.Exec("create virtual table repo using github(id, full_name, description, html_url)")
+
+	rows, err := db.Query("select id, full_name, description, html_url from repo")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer rows.Close()
+	for rows.Next() {
+		var id, full_name, description, html_url string
+		rows.Scan(&id, &full_name, &description, &html_url)
+		fmt.Printf("%s: %s\n\t%s\n\t%s\n\n", id, full_name, description, html_url)
+	}
+}
diff --git a/_example/mod_vtable/picojson.h b/_example/mod_vtable/picojson.h
new file mode 100644
index 0000000..2142647
--- /dev/null
+++ b/_example/mod_vtable/picojson.h
@@ -0,0 +1,1040 @@
+/*
+ * Copyright 2009-2010 Cybozu Labs, Inc.
+ * Copyright 2011 Kazuho Oku
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * 
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY CYBOZU LABS, INC. ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
+ * EVENT SHALL CYBOZU LABS, INC. OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ * 
+ * The views and conclusions contained in the software and documentation are
+ * those of the authors and should not be interpreted as representing official
+ * policies, either expressed or implied, of Cybozu Labs, Inc.
+ *
+ */
+#ifndef picojson_h
+#define picojson_h
+
+#include <algorithm>
+#include <cassert>
+#include <cmath>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <iostream>
+#include <iterator>
+#include <map>
+#include <string>
+#include <vector>
+
+#ifdef _MSC_VER
+    #define SNPRINTF _snprintf_s
+    #pragma warning(push)
+    #pragma warning(disable : 4244) // conversion from int to char
+#else
+    #define SNPRINTF snprintf
+#endif
+
+namespace picojson {
+  
+  enum {
+    null_type,
+    boolean_type,
+    number_type,
+    string_type,
+    array_type,
+    object_type
+  };
+  
+  struct null {};
+  
+  class value {
+  public:
+    typedef std::vector<value> array;
+    typedef std::map<std::string, value> object;
+    union _storage {
+      bool boolean_;
+      double number_;
+      std::string* string_;
+      array* array_;
+      object* object_;
+    };
+  protected:
+    int type_;
+    _storage u_;
+  public:
+    value();
+    value(int type, bool);
+    explicit value(bool b);
+    explicit value(double n);
+    explicit value(const std::string& s);
+    explicit value(const array& a);
+    explicit value(const object& o);
+    explicit value(const char* s);
+    value(const char* s, size_t len);
+    ~value();
+    value(const value& x);
+    value& operator=(const value& x);
+    void swap(value& x);
+    template <typename T> bool is() const;
+    template <typename T> const T& get() const;
+    template <typename T> T& get();
+    bool evaluate_as_boolean() const;
+    const value& get(size_t idx) const;
+    const value& get(const std::string& key) const;
+    bool contains(size_t idx) const;
+    bool contains(const std::string& key) const;
+    std::string to_str() const;
+    template <typename Iter> void serialize(Iter os) const;
+    std::string serialize() const;
+  private:
+    template <typename T> value(const T*); // intentionally defined to block implicit conversion of pointer to bool
+  };
+  
+  typedef value::array array;
+  typedef value::object object;
+  
+  inline value::value() : type_(null_type) {}
+  
+  inline value::value(int type, bool) : type_(type) {
+    switch (type) {
+#define INIT(p, v) case p##type: u_.p = v; break
+      INIT(boolean_, false);
+      INIT(number_, 0.0);
+      INIT(string_, new std::string());
+      INIT(array_, new array());
+      INIT(object_, new object());
+#undef INIT
+    default: break;
+    }
+  }
+  
+  inline value::value(bool b) : type_(boolean_type) {
+    u_.boolean_ = b;
+  }
+  
+  inline value::value(double n) : type_(number_type) {
+    u_.number_ = n;
+  }
+  
+  inline value::value(const std::string& s) : type_(string_type) {
+    u_.string_ = new std::string(s);
+  }
+  
+  inline value::value(const array& a) : type_(array_type) {
+    u_.array_ = new array(a);
+  }
+  
+  inline value::value(const object& o) : type_(object_type) {
+    u_.object_ = new object(o);
+  }
+  
+  inline value::value(const char* s) : type_(string_type) {
+    u_.string_ = new std::string(s);
+  }
+  
+  inline value::value(const char* s, size_t len) : type_(string_type) {
+    u_.string_ = new std::string(s, len);
+  }
+  
+  inline value::~value() {
+    switch (type_) {
+#define DEINIT(p) case p##type: delete u_.p; break
+      DEINIT(string_);
+      DEINIT(array_);
+      DEINIT(object_);
+#undef DEINIT
+    default: break;
+    }
+  }
+  
+  inline value::value(const value& x) : type_(x.type_) {
+    switch (type_) {
+#define INIT(p, v) case p##type: u_.p = v; break
+      INIT(string_, new std::string(*x.u_.string_));
+      INIT(array_, new array(*x.u_.array_));
+      INIT(object_, new object(*x.u_.object_));
+#undef INIT
+    default:
+      u_ = x.u_;
+      break;
+    }
+  }
+  
+  inline value& value::operator=(const value& x) {
+    if (this != &x) {
+      this->~value();
+      new (this) value(x);
+    }
+    return *this;
+  }
+  
+  inline void value::swap(value& x) {
+    std::swap(type_, x.type_);
+    std::swap(u_, x.u_);
+  }
+  
+#define IS(ctype, jtype)			     \
+  template <> inline bool value::is<ctype>() const { \
+    return type_ == jtype##_type;		     \
+  }
+  IS(null, null)
+  IS(bool, boolean)
+  IS(int, number)
+  IS(double, number)
+  IS(std::string, string)
+  IS(array, array)
+  IS(object, object)
+#undef IS
+  
+#define GET(ctype, var)						\
+  template <> inline const ctype& value::get<ctype>() const {	\
+    assert("type mismatch! call vis<type>() before get<type>()" \
+	   && is<ctype>());				        \
+    return var;							\
+  }								\
+  template <> inline ctype& value::get<ctype>() {		\
+    assert("type mismatch! call is<type>() before get<type>()"	\
+	   && is<ctype>());					\
+    return var;							\
+  }
+  GET(bool, u_.boolean_)
+  GET(double, u_.number_)
+  GET(std::string, *u_.string_)
+  GET(array, *u_.array_)
+  GET(object, *u_.object_)
+#undef GET
+  
+  inline bool value::evaluate_as_boolean() const {
+    switch (type_) {
+    case null_type:
+      return false;
+    case boolean_type:
+      return u_.boolean_;
+    case number_type:
+      return u_.number_ != 0;
+    case string_type:
+      return ! u_.string_->empty();
+    default:
+      return true;
+    }
+  }
+  
+  inline const value& value::get(size_t idx) const {
+    static value s_null;
+    assert(is<array>());
+    return idx < u_.array_->size() ? (*u_.array_)[idx] : s_null;
+  }
+
+  inline const value& value::get(const std::string& key) const {
+    static value s_null;
+    assert(is<object>());
+    object::const_iterator i = u_.object_->find(key);
+    return i != u_.object_->end() ? i->second : s_null;
+  }
+
+  inline bool value::contains(size_t idx) const {
+    assert(is<array>());
+    return idx < u_.array_->size();
+  }
+
+  inline bool value::contains(const std::string& key) const {
+    assert(is<object>());
+    object::const_iterator i = u_.object_->find(key);
+    return i != u_.object_->end();
+  }
+  
+  inline std::string value::to_str() const {
+    switch (type_) {
+    case null_type:      return "null";
+    case boolean_type:   return u_.boolean_ ? "true" : "false";
+    case number_type:    {
+      char buf[256];
+      double tmp;
+      SNPRINTF(buf, sizeof(buf), fabs(u_.number_) < (1ULL << 53) && modf(u_.number_, &tmp) == 0 ? "%.f" : "%.17g", u_.number_);
+      return buf;
+    }
+    case string_type:    return *u_.string_;
+    case array_type:     return "array";
+    case object_type:    return "object";
+    default:             assert(0);
+#ifdef _MSC_VER
+      __assume(0);
+#endif
+    }
+    return std::string();
+  }
+  
+  template <typename Iter> void copy(const std::string& s, Iter oi) {
+    std::copy(s.begin(), s.end(), oi);
+  }
+  
+  template <typename Iter> void serialize_str(const std::string& s, Iter oi) {
+    *oi++ = '"';
+    for (std::string::const_iterator i = s.begin(); i != s.end(); ++i) {
+      switch (*i) {
+#define MAP(val, sym) case val: copy(sym, oi); break
+	MAP('"', "\\\"");
+	MAP('\\', "\\\\");
+	MAP('/', "\\/");
+	MAP('\b', "\\b");
+	MAP('\f', "\\f");
+	MAP('\n', "\\n");
+	MAP('\r', "\\r");
+	MAP('\t', "\\t");
+#undef MAP
+      default:
+	if ((unsigned char)*i < 0x20 || *i == 0x7f) {
+	  char buf[7];
+	  SNPRINTF(buf, sizeof(buf), "\\u%04x", *i & 0xff);
+	  copy(buf, buf + 6, oi);
+	  } else {
+	  *oi++ = *i;
+	}
+	break;
+      }
+    }
+    *oi++ = '"';
+  }
+  
+  template <typename Iter> void value::serialize(Iter oi) const {
+    switch (type_) {
+    case string_type:
+      serialize_str(*u_.string_, oi);
+      break;
+    case array_type: {
+      *oi++ = '[';
+      for (array::const_iterator i = u_.array_->begin();
+           i != u_.array_->end();
+           ++i) {
+	if (i != u_.array_->begin()) {
+	  *oi++ = ',';
+	}
+	i->serialize(oi);
+      }
+      *oi++ = ']';
+      break;
+    }
+    case object_type: {
+      *oi++ = '{';
+      for (object::const_iterator i = u_.object_->begin();
+	   i != u_.object_->end();
+	   ++i) {
+	if (i != u_.object_->begin()) {
+	  *oi++ = ',';
+	}
+	serialize_str(i->first, oi);
+	*oi++ = ':';
+	i->second.serialize(oi);
+      }
+      *oi++ = '}';
+      break;
+    }
+    default:
+      copy(to_str(), oi);
+      break;
+    }
+  }
+  
+  inline std::string value::serialize() const {
+    std::string s;
+    serialize(std::back_inserter(s));
+    return s;
+  }
+  
+  template <typename Iter> class input {
+  protected:
+    Iter cur_, end_;
+    int last_ch_;
+    bool ungot_;
+    int line_;
+  public:
+    input(const Iter& first, const Iter& last) : cur_(first), end_(last), last_ch_(-1), ungot_(false), line_(1) {}
+    int getc() {
+      if (ungot_) {
+	ungot_ = false;
+	return last_ch_;
+      }
+      if (cur_ == end_) {
+	last_ch_ = -1;
+	return -1;
+      }
+      if (last_ch_ == '\n') {
+	line_++;
+      }
+      last_ch_ = *cur_++ & 0xff;
+      return last_ch_;
+    }
+    void ungetc() {
+      if (last_ch_ != -1) {
+	assert(! ungot_);
+	ungot_ = true;
+      }
+    }
+    Iter cur() const { return cur_; }
+    int line() const { return line_; }
+    void skip_ws() {
+      while (1) {
+	int ch = getc();
+	if (! (ch == ' ' || ch == '\t' || ch == '\n' || ch == '\r')) {
+	  ungetc();
+	  break;
+	}
+      }
+    }
+    bool expect(int expect) {
+      skip_ws();
+      if (getc() != expect) {
+	ungetc();
+	return false;
+      }
+      return true;
+    }
+    bool match(const std::string& pattern) {
+      for (std::string::const_iterator pi(pattern.begin());
+	   pi != pattern.end();
+	   ++pi) {
+	if (getc() != *pi) {
+	  ungetc();
+	  return false;
+	}
+      }
+      return true;
+    }
+  };
+  
+  template<typename Iter> inline int _parse_quadhex(input<Iter> &in) {
+    int uni_ch = 0, hex;
+    for (int i = 0; i < 4; i++) {
+      if ((hex = in.getc()) == -1) {
+	return -1;
+      }
+      if ('0' <= hex && hex <= '9') {
+	hex -= '0';
+      } else if ('A' <= hex && hex <= 'F') {
+	hex -= 'A' - 0xa;
+      } else if ('a' <= hex && hex <= 'f') {
+	hex -= 'a' - 0xa;
+      } else {
+	in.ungetc();
+	return -1;
+      }
+      uni_ch = uni_ch * 16 + hex;
+    }
+    return uni_ch;
+  }
+  
+  template<typename String, typename Iter> inline bool _parse_codepoint(String& out, input<Iter>& in) {
+    int uni_ch;
+    if ((uni_ch = _parse_quadhex(in)) == -1) {
+      return false;
+    }
+    if (0xd800 <= uni_ch && uni_ch <= 0xdfff) {
+      if (0xdc00 <= uni_ch) {
+	// a second 16-bit of a surrogate pair appeared
+	return false;
+      }
+      // first 16-bit of surrogate pair, get the next one
+      if (in.getc() != '\\' || in.getc() != 'u') {
+	in.ungetc();
+	return false;
+      }
+      int second = _parse_quadhex(in);
+      if (! (0xdc00 <= second && second <= 0xdfff)) {
+	return false;
+      }
+      uni_ch = ((uni_ch - 0xd800) << 10) | ((second - 0xdc00) & 0x3ff);
+      uni_ch += 0x10000;
+    }
+    if (uni_ch < 0x80) {
+      out.push_back(uni_ch);
+    } else {
+      if (uni_ch < 0x800) {
+	out.push_back(0xc0 | (uni_ch >> 6));
+      } else {
+	if (uni_ch < 0x10000) {
+	  out.push_back(0xe0 | (uni_ch >> 12));
+	} else {
+	  out.push_back(0xf0 | (uni_ch >> 18));
+	  out.push_back(0x80 | ((uni_ch >> 12) & 0x3f));
+	}
+	out.push_back(0x80 | ((uni_ch >> 6) & 0x3f));
+      }
+      out.push_back(0x80 | (uni_ch & 0x3f));
+    }
+    return true;
+  }
+  
+  template<typename String, typename Iter> inline bool _parse_string(String& out, input<Iter>& in) {
+    while (1) {
+      int ch = in.getc();
+      if (ch < ' ') {
+	in.ungetc();
+	return false;
+      } else if (ch == '"') {
+	return true;
+      } else if (ch == '\\') {
+	if ((ch = in.getc()) == -1) {
+	  return false;
+	}
+	switch (ch) {
+#define MAP(sym, val) case sym: out.push_back(val); break
+	  MAP('"', '\"');
+	  MAP('\\', '\\');
+	  MAP('/', '/');
+	  MAP('b', '\b');
+	  MAP('f', '\f');
+	  MAP('n', '\n');
+	  MAP('r', '\r');
+	  MAP('t', '\t');
+#undef MAP
+	case 'u':
+	  if (! _parse_codepoint(out, in)) {
+	    return false;
+	  }
+	  break;
+	default:
+	  return false;
+	}
+      } else {
+	out.push_back(ch);
+      }
+    }
+    return false;
+  }
+  
+  template <typename Context, typename Iter> inline bool _parse_array(Context& ctx, input<Iter>& in) {
+    if (! ctx.parse_array_start()) {
+      return false;
+    }
+    size_t idx = 0;
+    if (in.expect(']')) {
+      return ctx.parse_array_stop(idx);
+    }
+    do {
+      if (! ctx.parse_array_item(in, idx)) {
+	return false;
+      }
+      idx++;
+    } while (in.expect(','));
+    return in.expect(']') && ctx.parse_array_stop(idx);
+  }
+  
+  template <typename Context, typename Iter> inline bool _parse_object(Context& ctx, input<Iter>& in) {
+    if (! ctx.parse_object_start()) {
+      return false;
+    }
+    if (in.expect('}')) {
+      return true;
+    }
+    do {
+      std::string key;
+      if (! in.expect('"')
+	  || ! _parse_string(key, in)
+	  || ! in.expect(':')) {
+	return false;
+      }
+      if (! ctx.parse_object_item(in, key)) {
+	return false;
+      }
+    } while (in.expect(','));
+    return in.expect('}');
+  }
+  
+  template <typename Iter> inline bool _parse_number(double& out, input<Iter>& in) {
+    std::string num_str;
+    while (1) {
+      int ch = in.getc();
+      if (('0' <= ch && ch <= '9') || ch == '+' || ch == '-' || ch == '.'
+	  || ch == 'e' || ch == 'E') {
+	num_str.push_back(ch);
+      } else {
+	in.ungetc();
+	break;
+      }
+    }
+    char* endp;
+    out = strtod(num_str.c_str(), &endp);
+    return endp == num_str.c_str() + num_str.size();
+  }
+  
+  template <typename Context, typename Iter> inline bool _parse(Context& ctx, input<Iter>& in) {
+    in.skip_ws();
+    int ch = in.getc();
+    switch (ch) {
+#define IS(ch, text, op) case ch: \
+      if (in.match(text) && op) { \
+	return true; \
+      } else { \
+	return false; \
+      }
+      IS('n', "ull", ctx.set_null());
+      IS('f', "alse", ctx.set_bool(false));
+      IS('t', "rue", ctx.set_bool(true));
+#undef IS
+    case '"':
+      return ctx.parse_string(in);
+    case '[':
+      return _parse_array(ctx, in);
+    case '{':
+      return _parse_object(ctx, in);
+    default:
+      if (('0' <= ch && ch <= '9') || ch == '-') {
+	in.ungetc();
+	double f;
+	if (_parse_number(f, in)) {
+	  ctx.set_number(f);
+	  return true;
+	} else {
+	  return false;
+	}
+      }
+      break;
+    }
+    in.ungetc();
+    return false;
+  }
+  
+  class deny_parse_context {
+  public:
+    bool set_null() { return false; }
+    bool set_bool(bool) { return false; }
+    bool set_number(double) { return false; }
+    template <typename Iter> bool parse_string(input<Iter>&) { return false; }
+    bool parse_array_start() { return false; }
+    template <typename Iter> bool parse_array_item(input<Iter>&, size_t) {
+      return false;
+    }
+    bool parse_array_stop(size_t) { return false; }
+    bool parse_object_start() { return false; }
+    template <typename Iter> bool parse_object_item(input<Iter>&, const std::string&) {
+      return false;
+    }
+  };
+  
+  class default_parse_context {
+  protected:
+    value* out_;
+  public:
+    default_parse_context(value* out) : out_(out) {}
+    bool set_null() {
+      *out_ = value();
+      return true;
+    }
+    bool set_bool(bool b) {
+      *out_ = value(b);
+      return true;
+    }
+    bool set_number(double f) {
+      *out_ = value(f);
+      return true;
+    }
+    template<typename Iter> bool parse_string(input<Iter>& in) {
+      *out_ = value(string_type, false);
+      return _parse_string(out_->get<std::string>(), in);
+    }
+    bool parse_array_start() {
+      *out_ = value(array_type, false);
+      return true;
+    }
+    template <typename Iter> bool parse_array_item(input<Iter>& in, size_t) {
+      array& a = out_->get<array>();
+      a.push_back(value());
+      default_parse_context ctx(&a.back());
+      return _parse(ctx, in);
+    }
+    bool parse_array_stop(size_t) { return true; }
+    bool parse_object_start() {
+      *out_ = value(object_type, false);
+      return true;
+    }
+    template <typename Iter> bool parse_object_item(input<Iter>& in, const std::string& key) {
+      object& o = out_->get<object>();
+      default_parse_context ctx(&o[key]);
+      return _parse(ctx, in);
+    }
+  private:
+    default_parse_context(const default_parse_context&);
+    default_parse_context& operator=(const default_parse_context&);
+  };
+
+  class null_parse_context {
+  public:
+    struct dummy_str {
+      void push_back(int) {}
+    };
+  public:
+    null_parse_context() {}
+    bool set_null() { return true; }
+    bool set_bool(bool) { return true; }
+    bool set_number(double) { return true; }
+    template <typename Iter> bool parse_string(input<Iter>& in) {
+      dummy_str s;
+      return _parse_string(s, in);
+    }
+    bool parse_array_start() { return true; }
+    template <typename Iter> bool parse_array_item(input<Iter>& in, size_t) {
+      return _parse(*this, in);
+    }
+    bool parse_array_stop(size_t) { return true; }
+    bool parse_object_start() { return true; }
+    template <typename Iter> bool parse_object_item(input<Iter>& in, const std::string&) {
+      return _parse(*this, in);
+    }
+  private:
+    null_parse_context(const null_parse_context&);
+    null_parse_context& operator=(const null_parse_context&);
+  };
+  
+  // obsolete, use the version below
+  template <typename Iter> inline std::string parse(value& out, Iter& pos, const Iter& last) {
+    std::string err;
+    pos = parse(out, pos, last, &err);
+    return err;
+  }
+  
+  template <typename Context, typename Iter> inline Iter _parse(Context& ctx, const Iter& first, const Iter& last, std::string* err) {
+    input<Iter> in(first, last);
+    if (! _parse(ctx, in) && err != NULL) {
+      char buf[64];
+      SNPRINTF(buf, sizeof(buf), "syntax error at line %d near: ", in.line());
+      *err = buf;
+      while (1) {
+	int ch = in.getc();
+	if (ch == -1 || ch == '\n') {
+	  break;
+	} else if (ch >= ' ') {
+	  err->push_back(ch);
+	}
+      }
+    }
+    return in.cur();
+  }
+  
+  template <typename Iter> inline Iter parse(value& out, const Iter& first, const Iter& last, std::string* err) {
+    default_parse_context ctx(&out);
+    return _parse(ctx, first, last, err);
+  }
+  
+  inline std::string parse(value& out, std::istream& is) {
+    std::string err;
+    parse(out, std::istreambuf_iterator<char>(is.rdbuf()),
+	  std::istreambuf_iterator<char>(), &err);
+    return err;
+  }
+  
+  template <typename T> struct last_error_t {
+    static std::string s;
+  };
+  template <typename T> std::string last_error_t<T>::s;
+  
+  inline void set_last_error(const std::string& s) {
+    last_error_t<bool>::s = s;
+  }
+  
+  inline const std::string& get_last_error() {
+    return last_error_t<bool>::s;
+  }
+
+  inline bool operator==(const value& x, const value& y) {
+    if (x.is<null>())
+      return y.is<null>();
+#define PICOJSON_CMP(type)					\
+    if (x.is<type>())						\
+      return y.is<type>() && x.get<type>() == y.get<type>()
+    PICOJSON_CMP(bool);
+    PICOJSON_CMP(double);
+    PICOJSON_CMP(std::string);
+    PICOJSON_CMP(array);
+    PICOJSON_CMP(object);
+#undef PICOJSON_CMP
+    assert(0);
+#ifdef _MSC_VER
+    __assume(0);
+#endif
+    return false;
+  }
+  
+  inline bool operator!=(const value& x, const value& y) {
+    return ! (x == y);
+  }
+}
+
+namespace std {
+  template<> inline void swap(picojson::value& x, picojson::value& y)
+    {
+      x.swap(y);
+    }
+}
+
+inline std::istream& operator>>(std::istream& is, picojson::value& x)
+{
+  picojson::set_last_error(std::string());
+  std::string err = picojson::parse(x, is);
+  if (! err.empty()) {
+    picojson::set_last_error(err);
+    is.setstate(std::ios::failbit);
+  }
+  return is;
+}
+
+inline std::ostream& operator<<(std::ostream& os, const picojson::value& x)
+{
+  x.serialize(std::ostream_iterator<char>(os));
+  return os;
+}
+#ifdef _MSC_VER
+    #pragma warning(pop)
+#endif
+
+#endif
+#ifdef TEST_PICOJSON
+#ifdef _MSC_VER
+    #pragma warning(disable : 4127) // conditional expression is constant
+#endif
+
+using namespace std;
+  
+static void plan(int num)
+{
+  printf("1..%d\n", num);
+}
+
+static bool success = true;
+
+static void ok(bool b, const char* name = "")
+{
+  static int n = 1;
+  if (! b)
+    success = false;
+  printf("%s %d - %s\n", b ? "ok" : "ng", n++, name);
+}
+
+template <typename T> void is(const T& x, const T& y, const char* name = "")
+{
+  if (x == y) {
+    ok(true, name);
+  } else {
+    ok(false, name);
+  }
+}
+
+#include <algorithm>
+#include <sstream>
+#include <float.h>
+#include <limits.h>
+
+int main(void)
+{
+  plan(85);
+
+  // constructors
+#define TEST(expr, expected) \
+    is(picojson::value expr .serialize(), string(expected), "picojson::value" #expr)
+  
+  TEST( (true),  "true");
+  TEST( (false), "false");
+  TEST( (42.0),   "42");
+  TEST( (string("hello")), "\"hello\"");
+  TEST( ("hello"), "\"hello\"");
+  TEST( ("hello", 4), "\"hell\"");
+
+  {
+    double a = 1;
+    for (int i = 0; i < 1024; i++) {
+      picojson::value vi(a);
+      std::stringstream ss;
+      ss << vi;
+      picojson::value vo;
+      ss >> vo;
+      double b = vo.get<double>();
+      if ((i < 53 && a != b) || fabs(a - b) / b > 1e-8) {
+        printf("ng i=%d a=%.18e b=%.18e\n", i, a, b);
+      }
+      a *= 2;
+    }
+  }
+  
+#undef TEST
+  
+#define TEST(in, type, cmp, serialize_test) {				\
+    picojson::value v;							\
+    const char* s = in;							\
+    string err = picojson::parse(v, s, s + strlen(s));			\
+    ok(err.empty(), in " no error");					\
+    ok(v.is<type>(), in " check type");					\
+    is<type>(v.get<type>(), cmp, in " correct output");			\
+    is(*s, '\0', in " read to eof");					\
+    if (serialize_test) {						\
+      is(v.serialize(), string(in), in " serialize");			\
+    }									\
+  }
+  TEST("false", bool, false, true);
+  TEST("true", bool, true, true);
+  TEST("90.5", double, 90.5, false);
+  TEST("1.7976931348623157e+308", double, DBL_MAX, false);
+  TEST("\"hello\"", string, string("hello"), true);
+  TEST("\"\\\"\\\\\\/\\b\\f\\n\\r\\t\"", string, string("\"\\/\b\f\n\r\t"),
+       true);
+  TEST("\"\\u0061\\u30af\\u30ea\\u30b9\"", string,
+       string("a\xe3\x82\xaf\xe3\x83\xaa\xe3\x82\xb9"), false);
+  TEST("\"\\ud840\\udc0b\"", string, string("\xf0\xa0\x80\x8b"), false);
+#undef TEST
+
+#define TEST(type, expr) {					       \
+    picojson::value v;						       \
+    const char *s = expr;					       \
+    string err = picojson::parse(v, s, s + strlen(s));		       \
+    ok(err.empty(), "empty " #type " no error");		       \
+    ok(v.is<picojson::type>(), "empty " #type " check type");	       \
+    ok(v.get<picojson::type>().empty(), "check " #type " array size"); \
+  }
+  TEST(array, "[]");
+  TEST(object, "{}");
+#undef TEST
+  
+  {
+    picojson::value v;
+    const char *s = "[1,true,\"hello\"]";
+    string err = picojson::parse(v, s, s + strlen(s));
+    ok(err.empty(), "array no error");
+    ok(v.is<picojson::array>(), "array check type");
+    is(v.get<picojson::array>().size(), size_t(3), "check array size");
+    ok(v.contains(0), "check contains array[0]");
+    ok(v.get(0).is<double>(), "check array[0] type");
+    is(v.get(0).get<double>(), 1.0, "check array[0] value");
+    ok(v.contains(1), "check contains array[1]");
+    ok(v.get(1).is<bool>(), "check array[1] type");
+    ok(v.get(1).get<bool>(), "check array[1] value");
+    ok(v.contains(2), "check contains array[2]");
+    ok(v.get(2).is<string>(), "check array[2] type");
+    is(v.get(2).get<string>(), string("hello"), "check array[2] value");
+    ok(!v.contains(3), "check not contains array[3]");
+  }
+  
+  {
+    picojson::value v;
+    const char *s = "{ \"a\": true }";
+    string err = picojson::parse(v, s, s + strlen(s));
+    ok(err.empty(), "object no error");
+    ok(v.is<picojson::object>(), "object check type");
+    is(v.get<picojson::object>().size(), size_t(1), "check object size");
+    ok(v.contains("a"), "check contains property");
+    ok(v.get("a").is<bool>(), "check bool property exists");
+    is(v.get("a").get<bool>(), true, "check bool property value");
+    is(v.serialize(), string("{\"a\":true}"), "serialize object");
+    ok(!v.contains("z"), "check not contains property");
+  }
+
+#define TEST(json, msg) do {				\
+    picojson::value v;					\
+    const char *s = json;				\
+    string err = picojson::parse(v, s, s + strlen(s));	\
+    is(err, string("syntax error at line " msg), msg);	\
+  } while (0)
+  TEST("falsoa", "1 near: oa");
+  TEST("{]", "1 near: ]");
+  TEST("\n\bbell", "2 near: bell");
+  TEST("\"abc\nd\"", "1 near: ");
+#undef TEST
+  
+  {
+    picojson::value v1, v2;
+    const char *s;
+    string err;
+    s = "{ \"b\": true, \"a\": [1,2,\"three\"], \"d\": 2 }";
+    err = picojson::parse(v1, s, s + strlen(s));
+    s = "{ \"d\": 2.0, \"b\": true, \"a\": [1,2,\"three\"] }";
+    err = picojson::parse(v2, s, s + strlen(s));
+    ok((v1 == v2), "check == operator in deep comparison");
+  }
+
+  {
+    picojson::value v1, v2;
+    const char *s;
+    string err;
+    s = "{ \"b\": true, \"a\": [1,2,\"three\"], \"d\": 2 }";
+    err = picojson::parse(v1, s, s + strlen(s));
+    s = "{ \"d\": 2.0, \"a\": [1,\"three\"], \"b\": true }";
+    err = picojson::parse(v2, s, s + strlen(s));
+    ok((v1 != v2), "check != operator for array in deep comparison");
+  }
+
+  {
+    picojson::value v1, v2;
+    const char *s;
+    string err;
+    s = "{ \"b\": true, \"a\": [1,2,\"three\"], \"d\": 2 }";
+    err = picojson::parse(v1, s, s + strlen(s));
+    s = "{ \"d\": 2.0, \"a\": [1,2,\"three\"], \"b\": false }";
+    err = picojson::parse(v2, s, s + strlen(s));
+    ok((v1 != v2), "check != operator for object in deep comparison");
+  }
+
+  {
+    picojson::value v1, v2;
+    const char *s;
+    string err;
+    s = "{ \"b\": true, \"a\": [1,2,\"three\"], \"d\": 2 }";
+    err = picojson::parse(v1, s, s + strlen(s));
+    picojson::object& o = v1.get<picojson::object>();
+    o.erase("b");
+    picojson::array& a = o["a"].get<picojson::array>();
+    picojson::array::iterator i;
+    i = std::remove(a.begin(), a.end(), picojson::value(std::string("three")));
+    a.erase(i, a.end());
+    s = "{ \"a\": [1,2], \"d\": 2 }";
+    err = picojson::parse(v2, s, s + strlen(s));
+    ok((v1 == v2), "check erase()");
+  }
+
+  ok(picojson::value(3.0).serialize() == "3",
+     "integral number should be serialized as a integer");
+  
+  {
+    const char* s = "{ \"a\": [1,2], \"d\": 2 }";
+    picojson::null_parse_context ctx;
+    string err;
+    picojson::_parse(ctx, s, s + strlen(s), &err);
+    ok(err.empty(), "null_parse_context");
+  }
+  
+  {
+    picojson::value v1, v2;
+    v1 = picojson::value(true);
+    swap(v1, v2);
+    ok(v1.is<picojson::null>(), "swap (null)");
+    ok(v2.get<bool>() == true, "swap (bool)");
+
+    v1 = picojson::value("a");
+    v2 = picojson::value(1.0);
+    swap(v1, v2);
+    ok(v1.get<double>() == 1.0, "swap (dobule)");
+    ok(v2.get<string>() == "a", "swap (string)");
+
+    v1 = picojson::value(picojson::object());
+    v2 = picojson::value(picojson::array());
+    swap(v1, v2);
+    ok(v1.is<picojson::array>(), "swap (array)");
+    ok(v2.is<picojson::object>(), "swap (object)");
+  }
+  
+  return success ? 0 : 1;
+}
+
+#endif
diff --git a/_example/mod_vtable/sqlite3_mod_vtable.cc b/_example/mod_vtable/sqlite3_mod_vtable.cc
new file mode 100644
index 0000000..4caf484
--- /dev/null
+++ b/_example/mod_vtable/sqlite3_mod_vtable.cc
@@ -0,0 +1,238 @@
+#include <string>
+#include <sstream>
+#include <sqlite3.h>
+#include <sqlite3ext.h>
+#include <curl/curl.h>
+#include "picojson.h"
+
+#ifdef _WIN32
+# define EXPORT __declspec(dllexport)
+#else
+# define EXPORT
+#endif
+
+SQLITE_EXTENSION_INIT1;
+
+typedef struct {
+  char* data;   // response data from server
+  size_t size;  // response size of data
+} MEMFILE;
+
+MEMFILE*
+memfopen() {
+  MEMFILE* mf = (MEMFILE*) malloc(sizeof(MEMFILE));
+  if (mf) {
+    mf->data = NULL;
+    mf->size = 0;
+  }
+  return mf;
+}
+
+void
+memfclose(MEMFILE* mf) {
+  if (mf->data) free(mf->data);
+  free(mf);
+}
+
+size_t
+memfwrite(char* ptr, size_t size, size_t nmemb, void* stream) {
+  MEMFILE* mf = (MEMFILE*) stream;
+  int block = size * nmemb;
+  if (!mf) return block; // through
+  if (!mf->data)
+    mf->data = (char*) malloc(block);
+  else
+    mf->data = (char*) realloc(mf->data, mf->size + block);
+  if (mf->data) {
+    memcpy(mf->data + mf->size, ptr, block);
+    mf->size += block;
+  }
+  return block;
+}
+
+char*
+memfstrdup(MEMFILE* mf) {
+  char* buf;
+  if (mf->size == 0) return NULL;
+  buf = (char*) malloc(mf->size + 1);
+  memcpy(buf, mf->data, mf->size);
+  buf[mf->size] = 0;
+  return buf;
+}
+
+static int
+my_connect(sqlite3 *db, void *pAux, int argc, const char * const *argv, sqlite3_vtab **ppVTab, char **c) {
+  std::stringstream ss;
+  ss << "CREATE TABLE " << argv[0]
+    << "(id int, full_name text, description text, html_url text)";
+  int rc = sqlite3_declare_vtab(db, ss.str().c_str());
+  *ppVTab = (sqlite3_vtab *) sqlite3_malloc(sizeof(sqlite3_vtab));
+  memset(*ppVTab, 0, sizeof(sqlite3_vtab));
+  return rc;
+}
+
+static int
+my_create(sqlite3 *db, void *pAux, int argc, const char * const * argv, sqlite3_vtab **ppVTab, char **c) {
+  return my_connect(db, pAux, argc, argv, ppVTab, c);
+}
+
+static int my_disconnect(sqlite3_vtab *pVTab) {
+  sqlite3_free(pVTab);
+  return SQLITE_OK;
+}
+
+static int
+my_destroy(sqlite3_vtab *pVTab) {
+  sqlite3_free(pVTab);
+  return SQLITE_OK;
+}
+
+typedef struct {
+  sqlite3_vtab_cursor base;
+  int index;
+  picojson::value* rows;
+} cursor;
+
+static int
+my_open(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor) {
+  MEMFILE* mf;
+  CURL* curl;
+  char* json;
+  CURLcode res = CURLE_OK;
+  char error[CURL_ERROR_SIZE] = {0};
+  char* cert_file = getenv("SSL_CERT_FILE");
+
+  mf = memfopen();
+  curl = curl_easy_init();
+  curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 1);
+  curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 2);
+  curl_easy_setopt(curl, CURLOPT_USERAGENT, "curl/7.29.0");
+  curl_easy_setopt(curl, CURLOPT_URL, "https://api.github.com/repositories");
+  if (cert_file)
+    curl_easy_setopt(curl, CURLOPT_CAINFO, cert_file);
+  curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1);
+  curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, error);
+  curl_easy_setopt(curl, CURLOPT_WRITEDATA, mf);
+  curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, memfwrite);
+  res = curl_easy_perform(curl);
+  curl_easy_cleanup(curl);
+  if (res != CURLE_OK) {
+    std::cerr << error << std::endl;
+    return SQLITE_FAIL;
+  }
+
+  picojson::value* v = new picojson::value;
+  std::string err;
+  picojson::parse(*v, mf->data, mf->data + mf->size, &err);
+  memfclose(mf);
+
+  if (!err.empty()) {
+    delete v;
+    std::cerr << err << std::endl;
+    return SQLITE_FAIL;
+  }
+
+  cursor *c = (cursor *)sqlite3_malloc(sizeof(cursor));
+  c->rows = v;
+  c->index = 0;
+  *ppCursor = &c->base;
+  return SQLITE_OK;
+}
+
+static int
+my_close(cursor *c) {
+  delete c->rows;
+  sqlite3_free(c);
+  return SQLITE_OK;
+}
+
+static int
+my_filter(cursor *c, int idxNum, const char *idxStr, int argc, sqlite3_value **argv) {
+  c->index = 0;
+  return SQLITE_OK;
+}
+
+static int
+my_next(cursor *c) {
+  c->index++;
+  return SQLITE_OK;
+}
+
+static int
+my_eof(cursor *c) {
+  return c->index >= c->rows->get<picojson::array>().size() ? 1 : 0;
+}
+
+static int
+my_column(cursor *c, sqlite3_context *ctxt, int i) {
+  picojson::value v = c->rows->get<picojson::array>()[c->index];
+  picojson::object row = v.get<picojson::object>();
+  const char* p = NULL;
+  switch (i) {
+  case 0:
+    p = row["id"].to_str().c_str();
+    break;
+  case 1:
+    p = row["full_name"].to_str().c_str();
+    break;
+  case 2:
+    p = row["description"].to_str().c_str();
+    break;
+  case 3:
+    p = row["html_url"].to_str().c_str();
+    break;
+  }
+  sqlite3_result_text(ctxt, strdup(p), strlen(p), free);
+  return SQLITE_OK;
+}
+
+static int
+my_rowid(cursor *c, sqlite3_int64 *pRowid) {
+  *pRowid = c->index;
+  return SQLITE_OK;
+}
+
+static int
+my_bestindex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo) {
+  return SQLITE_OK;
+}
+
+static const sqlite3_module module = {
+  0,
+  my_create,
+  my_connect,
+  my_bestindex,
+  my_disconnect,
+  my_destroy,
+  my_open,
+  (int (*)(sqlite3_vtab_cursor *)) my_close,
+  (int (*)(sqlite3_vtab_cursor *, int, char const *, int, sqlite3_value **)) my_filter,
+  (int (*)(sqlite3_vtab_cursor *)) my_next,
+  (int (*)(sqlite3_vtab_cursor *)) my_eof,
+  (int (*)(sqlite3_vtab_cursor *, sqlite3_context *, int)) my_column,
+  (int (*)(sqlite3_vtab_cursor *, sqlite3_int64 *)) my_rowid,
+  NULL, // my_update
+  NULL, // my_begin
+  NULL, // my_sync
+  NULL, // my_commit
+  NULL, // my_rollback
+  NULL, // my_findfunction
+  NULL, // my_rename
+};
+
+static void
+destructor(void *arg) {
+  return;
+}
+
+
+extern "C" {
+
+EXPORT int
+sqlite3_extension_init(sqlite3 *db, char **errmsg, const sqlite3_api_routines *api) {
+  SQLITE_EXTENSION_INIT2(api);
+  sqlite3_create_module_v2(db, "github", &module, NULL, destructor);
+  return 0;
+}
+
+}