text: /*!
   * UTF-8 Validation Code originally from:
   * ws: a node.js websocket client
   * Copyright(c) 2015 Einar Otto Stangvik <einaros@gmail.com>
   * MIT Licensed
   */
  
  #include <v8.h>
  #include <node.h>
  #include <node_version.h>
  #include <node_buffer.h>
  #include <node_object_wrap.h>
  #include <stdlib.h>
  #include <wchar.h>
  #include <stdio.h>
  #include "nan.h"
  
  using namespace v8;
  using namespace node;
  
  #define UNI_SUR_HIGH_START   (uint32_t) 0xD800
  #define UNI_SUR_LOW_END    (uint32_t) 0xDFFF
  #define UNI_REPLACEMENT_CHAR (uint32_t) 0x0000FFFD
  #define UNI_MAX_LEGAL_UTF32  (uint32_t) 0x0010FFFF
  
  static const uint8_t trailingBytesForUTF8[256] = {
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
    2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, 3,3,3,3,3,3,3,3,4,4,4,4,5,5,5,5
  };
  
  static const uint32_t offsetsFromUTF8[6] = {
    0x00000000, 0x00003080, 0x000E2080,
    0x03C82080, 0xFA082080, 0x82082080
  };
  
  static int isLegalUTF8(const uint8_t *source, const int length)
  {
    uint8_t a;
    const uint8_t *srcptr = source+length;
    switch (length) {
    default: return 0;
    /* Everything else falls through when "true"... */
    /* RFC3629 makes 5 & 6 bytes UTF-8 illegal
    case 6: if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return 0;
    case 5: if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return 0; */
    case 4: if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return 0;
    case 3: if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return 0;
    case 2: if ((a = (*--srcptr)) > 0xBF) return 0;
      switch (*source) {
        /* no fall-through in this inner switch */
        case 0xE0: if (a < 0xA0) return 0; break;
        case 0xED: if (a > 0x9F) return 0; break;
        case 0xF0: if (a < 0x90) return 0; break;
        case 0xF4: if (a > 0x8F) return 0; break;
        default:   if (a < 0x80) return 0;
      }
  
    case 1: if (*source >= 0x80 && *source < 0xC2) return 0;
    }
    if (*source > 0xF4) return 0;
    return 1;
  }
  
  int is_valid_utf8 (size_t len, char *value)
  {
    /* is the string valid UTF-8? */
    for (unsigned int i = 0; i < len; i++) {
      uint32_t ch = 0;
      uint8_t  extrabytes = trailingBytesForUTF8[(uint8_t) value[i]];
  
      if (extrabytes + i >= len)
        return 0;
  
      if (isLegalUTF8 ((uint8_t *) (value + i), extrabytes + 1) == 0) return 0;
  
      switch (extrabytes) {
        case 5 : ch += (uint8_t) value[i++]; ch <<= 6;
        case 4 : ch += (uint8_t) value[i++]; ch <<= 6;
        case 3 : ch += (uint8_t) value[i++]; ch <<= 6;
        case 2 : ch += (uint8_t) value[i++]; ch <<= 6;
        case 1 : ch += (uint8_t) value[i++]; ch <<= 6;
        case 0 : ch += (uint8_t) value[i];
      }
  
      ch -= offsetsFromUTF8[extrabytes];
  
      if (ch <= UNI_MAX_LEGAL_UTF32) {
        if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END)
          return 0;
      } else {
        return 0;
      }
    }
  
    return 1;
  }
  
  class Validation : public ObjectWrap
  {
  public:
  
    static void Initialize(v8::Local<v8::Object> target)
    {
      Nan::HandleScope scope;
      Local<FunctionTemplate> t = Nan::New<FunctionTemplate>(New);
      t->InstanceTemplate()->SetInternalFieldCount(1);
      Nan::SetMethod(t, "isValidUTF8", Validation::IsValidUTF8);
      Nan::Set(target, Nan::New<String>("Validation").ToLocalChecked(), Nan::GetFunction(t).ToLocalChecked());
    }
  
  protected:
  
    static NAN_METHOD(New)
    {
      Nan::HandleScope scope;
      Validation* validation = new Validation();
      validation->Wrap(info.This());
      info.GetReturnValue().Set(info.This());
    }
  
    static NAN_METHOD(IsValidUTF8)
    {
      Nan::HandleScope scope;
      if (!Buffer::HasInstance(info[0])) {
        return Nan::ThrowTypeError("First argument needs to be a buffer");
      }
      Local<Object> buffer_obj = Nan::To<v8::Object>(info[0]).ToLocalChecked();
      char *buffer_data = Buffer::Data(buffer_obj);
      size_t buffer_length = Buffer::Length(buffer_obj);
      info.GetReturnValue().Set(is_valid_utf8(buffer_length, buffer_data) == 1 ? Nan::True() : Nan::False());
    }
  };
  #if !NODE_VERSION_AT_LEAST(0,10,0)
  extern "C"
  #endif
  void init (Local<Object> target)
  {
    Nan::HandleScope scope;
    Validation::Initialize(target);
  }
  
  NODE_MODULE(validation, init)
  