text: // Tencent is pleased to support the open source community by making RapidJSON available.
  // 
  // Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved.
  //
  // Licensed under the MIT License (the "License"); you may not use this file except
  // in compliance with the License. You may obtain a copy of the License at
  //
  // http://opensource.org/licenses/MIT
  //
  // Unless required by applicable law or agreed to in writing, software distributed 
  // under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR 
  // CONDITIONS OF ANY KIND, either express or implied. See the License for the 
  // specific language governing permissions and limitations under the License.
  
  #ifndef RAPIDJSON_WRITER_H_
  #define RAPIDJSON_WRITER_H_
  
  #include "stream.h"
  #include "internal/stack.h"
  #include "internal/strfunc.h"
  #include "internal/dtoa.h"
  #include "internal/itoa.h"
  #include "stringbuffer.h"
  #include <new>      // placement new
  
  #if defined(RAPIDJSON_SIMD) && defined(_MSC_VER)
  #include <intrin.h>
  #pragma intrinsic(_BitScanForward)
  #endif
  #ifdef RAPIDJSON_SSE42
  #include <nmmintrin.h>
  #elif defined(RAPIDJSON_SSE2)
  #include <emmintrin.h>
  #endif
  
  #ifdef _MSC_VER
  RAPIDJSON_DIAG_PUSH
  RAPIDJSON_DIAG_OFF(4127) // conditional expression is constant
  #endif
  
  #ifdef __clang__
  RAPIDJSON_DIAG_PUSH
  RAPIDJSON_DIAG_OFF(padded)
  #endif
  
  RAPIDJSON_NAMESPACE_BEGIN
  
  ///////////////////////////////////////////////////////////////////////////////
  // WriteFlag
  
  /*! \def RAPIDJSON_WRITE_DEFAULT_FLAGS 
      \ingroup RAPIDJSON_CONFIG
      \brief User-defined kWriteDefaultFlags definition.
  
      User can define this as any \c WriteFlag combinations.
  */
  #ifndef RAPIDJSON_WRITE_DEFAULT_FLAGS
  #define RAPIDJSON_WRITE_DEFAULT_FLAGS kWriteNoFlags
  #endif
  
  //! Combination of writeFlags
  enum WriteFlag {
      kWriteNoFlags = 0,              //!< No flags are set.
      kWriteValidateEncodingFlag = 1, //!< Validate encoding of JSON strings.
      kWriteDefaultFlags = RAPIDJSON_WRITE_DEFAULT_FLAGS  //!< Default write flags. Can be customized by defining RAPIDJSON_WRITE_DEFAULT_FLAGS
  };
  
  //! JSON writer
  /*! Writer implements the concept Handler.
      It generates JSON text by events to an output os.
  
      User may programmatically calls the functions of a writer to generate JSON text.
  
      On the other side, a writer can also be passed to objects that generates events, 
  
      for example Reader::Parse() and Document::Accept().
  
      \tparam OutputStream Type of output stream.
      \tparam SourceEncoding Encoding of source string.
      \tparam TargetEncoding Encoding of output stream.
      \tparam StackAllocator Type of allocator for allocating memory of stack.
      \note implements Handler concept
  */
  template<typename OutputStream, typename SourceEncoding = UTF8<>, typename TargetEncoding = UTF8<>, typename StackAllocator = CrtAllocator, unsigned writeFlags = kWriteDefaultFlags>
  class Writer {
  public:
      typedef typename SourceEncoding::Ch Ch;
  
      static const int kDefaultMaxDecimalPlaces = 324;
  
      //! Constructor
      /*! \param os Output stream.
          \param stackAllocator User supplied allocator. If it is null, it will create a private one.
          \param levelDepth Initial capacity of stack.
      */
      explicit
      Writer(OutputStream& os, StackAllocator* stackAllocator = 0, size_t levelDepth = kDefaultLevelDepth) : 
          os_(&os), level_stack_(stackAllocator, levelDepth * sizeof(Level)), maxDecimalPlaces_(kDefaultMaxDecimalPlaces), hasRoot_(false) {}
  
      explicit
      Writer(StackAllocator* allocator = 0, size_t levelDepth = kDefaultLevelDepth) :
          os_(0), level_stack_(allocator, levelDepth * sizeof(Level)), maxDecimalPlaces_(kDefaultMaxDecimalPlaces), hasRoot_(false) {}
  
      //! Reset the writer with a new stream.
      /*!
          This function reset the writer with a new stream and default settings,
          in order to make a Writer object reusable for output multiple JSONs.
  
          \param os New output stream.
          \code
          Writer<OutputStream> writer(os1);
          writer.StartObject();
          // ...
          writer.EndObject();
  
          writer.Reset(os2);
          writer.StartObject();
          // ...
          writer.EndObject();
          \endcode
      */
      void Reset(OutputStream& os) {
          os_ = &os;
          hasRoot_ = false;
          level_stack_.Clear();
      }
  
      //! Checks whether the output is a complete JSON.
      /*!
          A complete JSON has a complete root object or array.
      */
      bool IsComplete() const {
          return hasRoot_ && level_stack_.Empty();
      }
  
      int GetMaxDecimalPlaces() const {
          return maxDecimalPlaces_;
      }
  
      //! Sets the maximum number of decimal places for double output.
      /*!
          This setting truncates the output with specified number of decimal places.
  
          For example, 
  
          \code
          writer.SetMaxDecimalPlaces(3);
          writer.StartArray();
          writer.Double(0.12345);                 // "0.123"
          writer.Double(0.0001);                  // "0.0"
          writer.Double(1.234567890123456e30);    // "1.234567890123456e30" (do not truncate significand for positive exponent)
          writer.Double(1.23e-4);                 // "0.0"                  (do truncate significand for negative exponent)
          writer.EndArray();
          \endcode
  
          The default setting does not truncate any decimal places. You can restore to this setting by calling
          \code
          writer.SetMaxDecimalPlaces(Writer::kDefaultMaxDecimalPlaces);
          \endcode
      */
      void SetMaxDecimalPlaces(int maxDecimalPlaces) {
          maxDecimalPlaces_ = maxDecimalPlaces;
      }
  
      /*!@name Implementation of Handler
          \see Handler
      */
      //@{
  
      bool Null()                 { Prefix(kNullType);   return WriteNull(); }
      bool Bool(bool b)           { Prefix(b ? kTrueType : kFalseType); return WriteBool(b); }
      bool Int(int i)             { Prefix(kNumberType); return WriteInt(i); }
      bool Uint(unsigned u)       { Prefix(kNumberType); return WriteUint(u); }
      bool Int64(int64_t i64)     { Prefix(kNumberType); return WriteInt64(i64); }
      bool Uint64(uint64_t u64)   { Prefix(kNumberType); return WriteUint64(u64); }
  
      //! Writes the given \c double value to the stream
      /*!
          \param d The value to be written.
          \return Whether it is succeed.
      */
      bool Double(double d)       { Prefix(kNumberType); return WriteDouble(d); }
  
      bool RawNumber(const Ch* str, SizeType length, bool copy = false) {
          (void)copy;
          Prefix(kNumberType);
          return WriteString(str, length);
      }
  
      bool String(const Ch* str, SizeType length, bool copy = false) {
          (void)copy;
          Prefix(kStringType);
          return WriteString(str, length);
      }
  
  #if RAPIDJSON_HAS_STDSTRING
      bool String(const std::basic_string<Ch>& str) {
          return String(str.data(), SizeType(str.size()));
      }
  #endif
  
      bool StartObject() {
          Prefix(kObjectType);
          new (level_stack_.template Push<Level>()) Level(false);
          return WriteStartObject();
      }
  
      bool Key(const Ch* str, SizeType length, bool copy = false) { return String(str, length, copy); }
  
      bool EndObject(SizeType memberCount = 0) {
          (void)memberCount;
          RAPIDJSON_ASSERT(level_stack_.GetSize() >= sizeof(Level));
          RAPIDJSON_ASSERT(!level_stack_.template Top<Level>()->inArray);
          level_stack_.template Pop<Level>(1);
          bool ret = WriteEndObject();
          if (RAPIDJSON_UNLIKELY(level_stack_.Empty()))   // end of json text
              os_->Flush();
          return ret;
      }
  
      bool StartArray() {
          Prefix(kArrayType);
          new (level_stack_.template Push<Level>()) Level(true);
          return WriteStartArray();
      }
  
      bool EndArray(SizeType elementCount = 0) {
          (void)elementCount;
          RAPIDJSON_ASSERT(level_stack_.GetSize() >= sizeof(Level));
          RAPIDJSON_ASSERT(level_stack_.template Top<Level>()->inArray);
          level_stack_.template Pop<Level>(1);
          bool ret = WriteEndArray();
          if (RAPIDJSON_UNLIKELY(level_stack_.Empty()))   // end of json text
              os_->Flush();
          return ret;
      }
      //@}
  
      /*! @name Convenience extensions */
      //@{
  
      //! Simpler but slower overload.
      bool String(const Ch* str) { return String(str, internal::StrLen(str)); }
      bool Key(const Ch* str) { return Key(str, internal::StrLen(str)); }
  
      //@}
  
      //! Write a raw JSON value.
      /*!
          For user to write a stringified JSON as a value.
  
          \param json A well-formed JSON value. It should not contain null character within [0, length - 1] range.
          \param length Length of the json.
          \param type Type of the root of json.
      */
      bool RawValue(const Ch* json, size_t length, Type type) { Prefix(type); return WriteRawValue(json, length); }
  
  protected:
      //! Information for each nested level
      struct Level {
          Level(bool inArray_) : valueCount(0), inArray(inArray_) {}
          size_t valueCount;  //!< number of values in this level
          bool inArray;       //!< true if in array, otherwise in object
      };
  
      static const size_t kDefaultLevelDepth = 32;
  
      bool WriteNull()  {
          PutReserve(*os_, 4);
          PutUnsafe(*os_, 'n'); PutUnsafe(*os_, 'u'); PutUnsafe(*os_, 'l'); PutUnsafe(*os_, 'l'); return true;
      }
  
      bool WriteBool(bool b)  {
          if (b) {
              PutReserve(*os_, 4);
              PutUnsafe(*os_, 't'); PutUnsafe(*os_, 'r'); PutUnsafe(*os_, 'u'); PutUnsafe(*os_, 'e');
          }
          else {
              PutReserve(*os_, 5);
              PutUnsafe(*os_, 'f'); PutUnsafe(*os_, 'a'); PutUnsafe(*os_, 'l'); PutUnsafe(*os_, 's'); PutUnsafe(*os_, 'e');
          }
          return true;
      }
  
      bool WriteInt(int i) {
          char buffer[11];
          const char* end = internal::i32toa(i, buffer);
          PutReserve(*os_, static_cast<size_t>(end - buffer));
          for (const char* p = buffer; p != end; ++p)
              PutUnsafe(*os_, static_cast<typename TargetEncoding::Ch>(*p));
          return true;
      }
  
      bool WriteUint(unsigned u) {
          char buffer[10];
          const char* end = internal::u32toa(u, buffer);
          PutReserve(*os_, static_cast<size_t>(end - buffer));
          for (const char* p = buffer; p != end; ++p)
              PutUnsafe(*os_, static_cast<typename TargetEncoding::Ch>(*p));
          return true;
      }
  
      bool WriteInt64(int64_t i64) {
          char buffer[21];
          const char* end = internal::i64toa(i64, buffer);
          PutReserve(*os_, static_cast<size_t>(end - buffer));
          for (const char* p = buffer; p != end; ++p)
              PutUnsafe(*os_, static_cast<typename TargetEncoding::Ch>(*p));
          return true;
      }
  
      bool WriteUint64(uint64_t u64) {
          char buffer[20];
          char* end = internal::u64toa(u64, buffer);
          PutReserve(*os_, static_cast<size_t>(end - buffer));
          for (char* p = buffer; p != end; ++p)
              PutUnsafe(*os_, static_cast<typename TargetEncoding::Ch>(*p));
          return true;
      }
  
      bool WriteDouble(double d) {
          if (internal::Double(d).IsNanOrInf())
              return false;
          
          char buffer[25];
          char* end = internal::dtoa(d, buffer, maxDecimalPlaces_);
          PutReserve(*os_, static_cast<size_t>(end - buffer));
          for (char* p = buffer; p != end; ++p)
              PutUnsafe(*os_, static_cast<typename TargetEncoding::Ch>(*p));
          return true;
      }
  
      bool WriteString(const Ch* str, SizeType length)  {
          static const typename TargetEncoding::Ch hexDigits[16] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
          static const char escape[256] = {
  #define Z16 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
              //0    1    2    3    4    5    6    7    8    9    A    B    C    D    E    F
              'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', 'b', 't', 'n', 'u', 'f', 'r', 'u', 'u', // 00
              'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', 'u', // 10
                0,   0, '"',   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0, // 20
              Z16, Z16,                                                                       // 30~4F
                0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,'\\',   0,   0,   0, // 50
              Z16, Z16, Z16, Z16, Z16, Z16, Z16, Z16, Z16, Z16                                // 60~FF
  #undef Z16
          };
  
          if (TargetEncoding::supportUnicode)
              PutReserve(*os_, 2 + length * 6); // "\uxxxx..."
          else
              PutReserve(*os_, 2 + length * 12);  // "\uxxxx\uyyyy..."
  
          PutUnsafe(*os_, '\"');
          GenericStringStream<SourceEncoding> is(str);
          while (ScanWriteUnescapedString(is, length)) {
              const Ch c = is.Peek();
              if (!TargetEncoding::supportUnicode && static_cast<unsigned>(c) >= 0x80) {
                  // Unicode escaping
                  unsigned codepoint;
                  if (RAPIDJSON_UNLIKELY(!SourceEncoding::Decode(is, &codepoint)))
                      return false;
                  PutUnsafe(*os_, '\\');
                  PutUnsafe(*os_, 'u');
                  if (codepoint <= 0xD7FF || (codepoint >= 0xE000 && codepoint <= 0xFFFF)) {
                      PutUnsafe(*os_, hexDigits[(codepoint >> 12) & 15]);
                      PutUnsafe(*os_, hexDigits[(codepoint >>  8) & 15]);
                      PutUnsafe(*os_, hexDigits[(codepoint >>  4) & 15]);
                      PutUnsafe(*os_, hexDigits[(codepoint      ) & 15]);
                  }
                  else {
                      RAPIDJSON_ASSERT(codepoint >= 0x010000 && codepoint <= 0x10FFFF);
                      // Surrogate pair
                      unsigned s = codepoint - 0x010000;
                      unsigned lead = (s >> 10) + 0xD800;
                      unsigned trail = (s & 0x3FF) + 0xDC00;
                      PutUnsafe(*os_, hexDigits[(lead >> 12) & 15]);
                      PutUnsafe(*os_, hexDigits[(lead >>  8) & 15]);
                      PutUnsafe(*os_, hexDigits[(lead >>  4) & 15]);
                      PutUnsafe(*os_, hexDigits[(lead      ) & 15]);
                      PutUnsafe(*os_, '\\');
                      PutUnsafe(*os_, 'u');
                      PutUnsafe(*os_, hexDigits[(trail >> 12) & 15]);
                      PutUnsafe(*os_, hexDigits[(trail >>  8) & 15]);
                      PutUnsafe(*os_, hexDigits[(trail >>  4) & 15]);
                      PutUnsafe(*os_, hexDigits[(trail      ) & 15]);                    
                  }
              }
              else if ((sizeof(Ch) == 1 || static_cast<unsigned>(c) < 256) && RAPIDJSON_UNLIKELY(escape[static_cast<unsigned char>(c)]))  {
                  is.Take();
                  PutUnsafe(*os_, '\\');
                  PutUnsafe(*os_, static_cast<typename TargetEncoding::Ch>(escape[static_cast<unsigned char>(c)]));
                  if (escape[static_cast<unsigned char>(c)] == 'u') {
                      PutUnsafe(*os_, '0');
                      PutUnsafe(*os_, '0');
                      PutUnsafe(*os_, hexDigits[static_cast<unsigned char>(c) >> 4]);
                      PutUnsafe(*os_, hexDigits[static_cast<unsigned char>(c) & 0xF]);
                  }
              }
              else if (RAPIDJSON_UNLIKELY(!(writeFlags & kWriteValidateEncodingFlag ? 
                  Transcoder<SourceEncoding, TargetEncoding>::Validate(is, *os_) :
                  Transcoder<SourceEncoding, TargetEncoding>::TranscodeUnsafe(is, *os_))))
                  return false;
          }
          PutUnsafe(*os_, '\"');
          return true;
      }
  
      bool ScanWriteUnescapedString(GenericStringStream<SourceEncoding>& is, size_t length) {
          return RAPIDJSON_LIKELY(is.Tell() < length);
      }
  
      bool WriteStartObject() { os_->Put('{'); return true; }
      bool WriteEndObject()   { os_->Put('}'); return true; }
      bool WriteStartArray()  { os_->Put('['); return true; }
      bool WriteEndArray()    { os_->Put(']'); return true; }
  
      bool WriteRawValue(const Ch* json, size_t length) {
          PutReserve(*os_, length);
          for (size_t i = 0; i < length; i++) {
              RAPIDJSON_ASSERT(json[i] != '\0');
              PutUnsafe(*os_, json[i]);
          }
          return true;
      }
  
      void Prefix(Type type) {
          (void)type;
          if (RAPIDJSON_LIKELY(level_stack_.GetSize() != 0)) { // this value is not at root
              Level* level = level_stack_.template Top<Level>();
              if (level->valueCount > 0) {
                  if (level->inArray) 
                      os_->Put(','); // add comma if it is not the first element in array
                  else  // in object
                      os_->Put((level->valueCount % 2 == 0) ? ',' : ':');
              }
              if (!level->inArray && level->valueCount % 2 == 0)
                  RAPIDJSON_ASSERT(type == kStringType);  // if it's in object, then even number should be a name
              level->valueCount++;
          }
          else {
              RAPIDJSON_ASSERT(!hasRoot_);    // Should only has one and only one root.
              hasRoot_ = true;
          }
      }
  
      OutputStream* os_;
      internal::Stack<StackAllocator> level_stack_;
      int maxDecimalPlaces_;
      bool hasRoot_;
  
  private:
      // Prohibit copy constructor & assignment operator.
      Writer(const Writer&);
      Writer& operator=(const Writer&);
  };
  
  // Full specialization for StringStream to prevent memory copying
  
  template<>
  inline bool Writer<StringBuffer>::WriteInt(int i) {
      char *buffer = os_->Push(11);
      const char* end = internal::i32toa(i, buffer);
      os_->Pop(static_cast<size_t>(11 - (end - buffer)));
      return true;
  }
  
  template<>
  inline bool Writer<StringBuffer>::WriteUint(unsigned u) {
      char *buffer = os_->Push(10);
      const char* end = internal::u32toa(u, buffer);
      os_->Pop(static_cast<size_t>(10 - (end - buffer)));
      return true;
  }
  
  template<>
  inline bool Writer<StringBuffer>::WriteInt64(int64_t i64) {
      char *buffer = os_->Push(21);
      const char* end = internal::i64toa(i64, buffer);
      os_->Pop(static_cast<size_t>(21 - (end - buffer)));
      return true;
  }
  
  template<>
  inline bool Writer<StringBuffer>::WriteUint64(uint64_t u) {
      char *buffer = os_->Push(20);
      const char* end = internal::u64toa(u, buffer);
      os_->Pop(static_cast<size_t>(20 - (end - buffer)));
      return true;
  }
  
  template<>
  inline bool Writer<StringBuffer>::WriteDouble(double d) {
      if (internal::Double(d).IsNanOrInf())
          return false;
      
      char *buffer = os_->Push(25);
      char* end = internal::dtoa(d, buffer, maxDecimalPlaces_);
      os_->Pop(static_cast<size_t>(25 - (end - buffer)));
      return true;
  }
  
  #if defined(RAPIDJSON_SSE2) || defined(RAPIDJSON_SSE42)
  template<>
  inline bool Writer<StringBuffer>::ScanWriteUnescapedString(StringStream& is, size_t length) {
      if (length < 16)
          return RAPIDJSON_LIKELY(is.Tell() < length);
  
      if (!RAPIDJSON_LIKELY(is.Tell() < length))
          return false;
  
      const char* p = is.src_;
      const char* end = is.head_ + length;
      const char* nextAligned = reinterpret_cast<const char*>((reinterpret_cast<size_t>(p) + 15) & static_cast<size_t>(~15));
      const char* endAligned = reinterpret_cast<const char*>(reinterpret_cast<size_t>(end) & static_cast<size_t>(~15));
      if (nextAligned > end)
          return true;
  
      while (p != nextAligned)
          if (*p < 0x20 || *p == '\"' || *p == '\\') {
              is.src_ = p;
              return RAPIDJSON_LIKELY(is.Tell() < length);
          }
          else
              os_->PutUnsafe(*p++);
  
      // The rest of string using SIMD
      static const char dquote[16] = { '\"', '\"', '\"', '\"', '\"', '\"', '\"', '\"', '\"', '\"', '\"', '\"', '\"', '\"', '\"', '\"' };
      static const char bslash[16] = { '\\', '\\', '\\', '\\', '\\', '\\', '\\', '\\', '\\', '\\', '\\', '\\', '\\', '\\', '\\', '\\' };
      static const char space[16]  = { 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19, 0x19 };
      const __m128i dq = _mm_loadu_si128(reinterpret_cast<const __m128i *>(&dquote[0]));
      const __m128i bs = _mm_loadu_si128(reinterpret_cast<const __m128i *>(&bslash[0]));
      const __m128i sp = _mm_loadu_si128(reinterpret_cast<const __m128i *>(&space[0]));
  
      for (; p != endAligned; p += 16) {
          const __m128i s = _mm_load_si128(reinterpret_cast<const __m128i *>(p));
          const __m128i t1 = _mm_cmpeq_epi8(s, dq);
          const __m128i t2 = _mm_cmpeq_epi8(s, bs);
          const __m128i t3 = _mm_cmpeq_epi8(_mm_max_epu8(s, sp), sp); // s < 0x20 <=> max(s, 0x19) == 0x19
          const __m128i x = _mm_or_si128(_mm_or_si128(t1, t2), t3);
          unsigned short r = static_cast<unsigned short>(_mm_movemask_epi8(x));
          if (RAPIDJSON_UNLIKELY(r != 0)) {   // some of characters is escaped
              SizeType len;
  #ifdef _MSC_VER         // Find the index of first escaped
              unsigned long offset;
              _BitScanForward(&offset, r);
              len = offset;
  #else
              len = static_cast<SizeType>(__builtin_ffs(r) - 1);
  #endif
              char* q = reinterpret_cast<char*>(os_->PushUnsafe(len));
              for (size_t i = 0; i < len; i++)
                  q[i] = p[i];
  
              p += len;
              break;
          }
          _mm_storeu_si128(reinterpret_cast<__m128i *>(os_->PushUnsafe(16)), s);
      }
  
      is.src_ = p;
      return RAPIDJSON_LIKELY(is.Tell() < length);
  }
  #endif // defined(RAPIDJSON_SSE2) || defined(RAPIDJSON_SSE42)
  
  RAPIDJSON_NAMESPACE_END
  
  #ifdef _MSC_VER
  RAPIDJSON_DIAG_POP
  #endif
  
  #ifdef __clang__
  RAPIDJSON_DIAG_POP
  #endif
  
  #endif // RAPIDJSON_RAPIDJSON_H_
  