text: // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
  // for details. All rights reserved. Use of this source code is governed by a
  // BSD-style license that can be found in the LICENSE file.
  
  #ifndef RUNTIME_PLATFORM_UNICODE_H_
  #define RUNTIME_PLATFORM_UNICODE_H_
  
  #include "platform/allocation.h"
  #include "platform/globals.h"
  
  namespace dart {
  
  class String;
  
  class Utf : AllStatic {
   public:
    static const int32_t kMaxCodePoint = 0x10FFFF;
    static const int32_t kInvalidChar = 0xFFFFFFFF;
  
    static bool IsLatin1(int32_t code_point) {
      return (code_point >= 0) && (code_point <= 0xFF);
    }
  
    static bool IsBmp(int32_t code_point) {
      return (code_point >= 0) && (code_point <= 0xFFFF);
    }
  
    static bool IsSupplementary(int32_t code_point) {
      return (code_point > 0xFFFF) && (code_point <= kMaxCodePoint);
    }
  
    // Returns true if the code point value is above Plane 17.
    static bool IsOutOfRange(int32_t code_point) {
      return (code_point < 0) || (code_point > kMaxCodePoint);
    }
  };
  
  class Utf8 : AllStatic {
   public:
    enum Type {
      kLatin1 = 0,     // Latin-1 code point [U+0000, U+00FF].
      kBMP,            // Basic Multilingual Plane code point [U+0000, U+FFFF].
      kSupplementary,  // Supplementary code point [U+010000, U+10FFFF].
    };
  
    // Returns the most restricted coding form in which the sequence of utf8
    // characters in 'utf8_array' can be represented in, and the number of
    // code units needed in that form.
    static intptr_t CodeUnitCount(const uint8_t* utf8_array,
                                  intptr_t array_len,
                                  Type* type);
  
    // Returns true if 'utf8_array' is a valid UTF-8 string.
    static bool IsValid(const uint8_t* utf8_array, intptr_t array_len);
  
    static intptr_t Length(int32_t ch);
    static intptr_t Length(const String& str);
  
    static intptr_t Encode(int32_t ch, char* dst);
    static intptr_t Encode(const String& src, char* dst, intptr_t len);
  
    static intptr_t Decode(const uint8_t* utf8_array,
                           intptr_t array_len,
                           int32_t* ch);
  
    static bool DecodeToLatin1(const uint8_t* utf8_array,
                               intptr_t array_len,
                               uint8_t* dst,
                               intptr_t len);
    static bool DecodeToUTF16(const uint8_t* utf8_array,
                              intptr_t array_len,
                              uint16_t* dst,
                              intptr_t len);
    static bool DecodeToUTF32(const uint8_t* utf8_array,
                              intptr_t array_len,
                              int32_t* dst,
                              intptr_t len);
    static intptr_t ReportInvalidByte(const uint8_t* utf8_array,
                                      intptr_t array_len,
                                      intptr_t len);
    static bool DecodeCStringToUTF32(const char* str, int32_t* dst, intptr_t len);
  
    static const int32_t kMaxOneByteChar = 0x7F;
    static const int32_t kMaxTwoByteChar = 0x7FF;
    static const int32_t kMaxThreeByteChar = 0xFFFF;
    static const int32_t kMaxFourByteChar = Utf::kMaxCodePoint;
  
   private:
    static bool IsTrailByte(uint8_t code_unit) {
      return (code_unit & 0xC0) == 0x80;
    }
  
    static bool IsNonShortestForm(uint32_t code_point, size_t num_code_units) {
      return code_point < kOverlongMinimum[num_code_units];
    }
  
    static bool IsLatin1SequenceStart(uint8_t code_unit) {
      // Check if utf8 sequence is the start of a codepoint <= U+00FF
      return (code_unit <= 0xC3);
    }
  
    static bool IsSupplementarySequenceStart(uint8_t code_unit) {
      // Check if utf8 sequence is the start of a codepoint >= U+10000.
      return (code_unit >= 0xF0);
    }
  
    static const int8_t kTrailBytes[];
    static const uint32_t kMagicBits[];
    static const uint32_t kOverlongMinimum[];
  };
  
  class Utf16 : AllStatic {
   public:
    // Returns the length of the code point in UTF-16 code units.
    static intptr_t Length(int32_t ch) {
      return (ch <= Utf16::kMaxCodeUnit) ? 1 : 2;
    }
  
    // Returns true if ch is a lead or trail surrogate.
    static bool IsSurrogate(uint32_t ch) { return (ch & 0xFFFFF800) == 0xD800; }
  
    // Returns true if ch is a lead surrogate.
    static bool IsLeadSurrogate(uint32_t ch) {
      return (ch & 0xFFFFFC00) == 0xD800;
    }
  
    // Returns true if ch is a low surrogate.
    static bool IsTrailSurrogate(uint32_t ch) {
      return (ch & 0xFFFFFC00) == 0xDC00;
    }
  
    // Returns the character at i and advances i to the next character
    // boundary.
    static int32_t Next(const uint16_t* characters, intptr_t* i, intptr_t len) {
      int32_t ch = characters[*i];
      if (Utf16::IsLeadSurrogate(ch) && (*i < (len - 1))) {
        int32_t ch2 = characters[*i + 1];
        if (Utf16::IsTrailSurrogate(ch2)) {
          ch = Utf16::Decode(ch, ch2);
          *i += 1;
        }
      }
      *i += 1;
      return ch;
    }
  
    // Decodes a surrogate pair into a supplementary code point.
    static int32_t Decode(uint16_t lead, uint16_t trail) {
      return 0x10000 + ((lead & 0x000003FF) << 10) + (trail & 0x3FF);
    }
  
    // Encodes a single code point.
    static void Encode(int32_t codepoint, uint16_t* dst);
  
    static const int32_t kMaxCodeUnit = 0xFFFF;
    static const int32_t kLeadSurrogateStart = 0xD800;
    static const int32_t kLeadSurrogateEnd = 0xDBFF;
    static const int32_t kTrailSurrogateStart = 0xDC00;
    static const int32_t kTrailSurrogateEnd = 0xDFFF;
  
   private:
    static const int32_t kLeadSurrogateOffset = (0xD800 - (0x10000 >> 10));
  
    static const int32_t kSurrogateOffset = (0x10000 - (0xD800 << 10) - 0xDC00);
  };
  
  class CaseMapping : AllStatic {
   public:
    // Maps a code point to uppercase.
    static int32_t ToUpper(int32_t code_point) {
      return Convert(code_point, kUppercase);
    }
  
    // Maps a code point to lowercase.
    static int32_t ToLower(int32_t code_point) {
      return Convert(code_point, kLowercase);
    }
  
   private:
    // Property is a delta to the uppercase mapping.
    static const int32_t kUppercase = 1;
  
    // Property is a delta to the uppercase mapping.
    static const int32_t kLowercase = 2;
  
    // Property is an index into the exception table.
    static const int32_t kException = 3;
  
    // Type bit-field parameters
    static const int32_t kTypeShift = 2;
    static const int32_t kTypeMask = 3;
  
    // The size of the stage 1 index.
    // TODO(cshapiro): improve indexing so this value is unnecessary.
    static const intptr_t kStage1Size = 261;
  
    // The size of a stage 2 block in bytes.
    static const intptr_t kBlockSizeLog2 = 8;
    static const intptr_t kBlockSize = 1 << kBlockSizeLog2;
  
    static int32_t Convert(int32_t ch, int32_t mapping) {
      if (Utf::IsLatin1(ch)) {
        int32_t info = stage2_[ch];
        if ((info & kTypeMask) == mapping) {
          ch += info >> kTypeShift;
        }
      } else if (ch <= (kStage1Size << kBlockSizeLog2)) {
        int16_t offset = stage1_[ch >> kBlockSizeLog2] << kBlockSizeLog2;
        int32_t info = stage2_[offset + (ch & (kBlockSize - 1))];
        int32_t type = info & kTypeMask;
        if (type == mapping) {
          ch += (info >> kTypeShift);
        } else if (type == kException) {
          ch += stage2_exception_[info >> kTypeShift][mapping - 1];
        }
      }
      return ch;
    }
  
    // Index into the data array.
    static const uint8_t stage1_[];
  
    // Data for small code points with one mapping
    static const int16_t stage2_[];
  
    // Data for large code points or code points with both mappings.
    static const int32_t stage2_exception_[][2];
  };
  
  class Latin1 {
   public:
    static const int32_t kMaxChar = 0xff;
    // Convert the character to Latin-1 case equivalent if possible.
    static inline uint16_t TryConvertToLatin1(uint16_t c) {
      switch (c) {
        // This are equivalent characters in unicode.
        case 0x39c:
        case 0x3bc:
          return 0xb5;
        // This is an uppercase of a Latin-1 character
        // outside of Latin-1.
        case 0x178:
          return 0xff;
      }
      return c;
    }
  };
  
  }  // namespace dart
  
  #endif  // RUNTIME_PLATFORM_UNICODE_H_
  