src/inspector/string-16.cc

// Copyright 2016 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/inspector/string-16.h"

#include <algorithm>
#include <cctype>
#include <cstdlib>
#include <cstring>
#include <limits>
#include <string>

#include "src/base/platform/platform.h"
#include "src/conversions.h"

namespace v8_inspector {

namespace {

bool isASCII(UChar c) { return !(c & ~0x7F); }

bool isSpaceOrNewLine(UChar c) {
  return isASCII(c) && c <= ' ' && (c == ' ' || (c <= 0xD && c >= 0x9));
}

int charactersToInteger(const UChar* characters, size_t length,
                        bool* ok = nullptr) {
  std::vector<char> buffer;
  buffer.reserve(length + 1);
  for (size_t i = 0; i < length; ++i) {
    if (!isASCII(characters[i])) {
      if (ok) *ok = false;
      return 0;
    }
    buffer.push_back(static_cast<char>(characters[i]));
  }
  buffer.push_back('\0');

  char* endptr;
  int64_t result =
      static_cast<int64_t>(std::strtol(buffer.data(), &endptr, 10));
  if (ok) {
    *ok = !(*endptr) && result <= std::numeric_limits<int>::max() &&
          result >= std::numeric_limits<int>::min();
  }
  return static_cast<int>(result);
}

const UChar replacementCharacter = 0xFFFD;
using UChar32 = uint32_t;

inline int inlineUTF8SequenceLengthNonASCII(char b0) {
  if ((b0 & 0xC0) != 0xC0) return 0;
  if ((b0 & 0xE0) == 0xC0) return 2;
  if ((b0 & 0xF0) == 0xE0) return 3;
  if ((b0 & 0xF8) == 0xF0) return 4;
  return 0;
}

inline int inlineUTF8SequenceLength(char b0) {
  return isASCII(b0) ? 1 : inlineUTF8SequenceLengthNonASCII(b0);
}

// Once the bits are split out into bytes of UTF-8, this is a mask OR-ed
// into the first byte, depending on how many bytes follow.  There are
// as many entries in this table as there are UTF-8 sequence types.
// (I.e., one byte sequence, two byte... etc.). Remember that sequences
// for *legal* UTF-8 will be 4 or fewer bytes total.
static const unsigned char firstByteMark[7] = {0x00, 0x00, 0xC0, 0xE0,
                                               0xF0, 0xF8, 0xFC};

typedef enum {
  conversionOK,     // conversion successful
  sourceExhausted,  // partial character in source, but hit end
  targetExhausted,  // insuff. room in target for conversion
  sourceIllegal     // source sequence is illegal/malformed
} ConversionResult;

ConversionResult convertUTF16ToUTF8(const UChar** sourceStart,
                                    const UChar* sourceEnd, char** targetStart,
                                    char* targetEnd, bool strict) {
  ConversionResult result = conversionOK;
  const UChar* source = *sourceStart;
  char* target = *targetStart;
  while (source < sourceEnd) {
    UChar32 ch;
    uint32_t bytesToWrite = 0;
    const UChar32 byteMask = 0xBF;
    const UChar32 byteMark = 0x80;
    const UChar* oldSource =
        source;  // In case we have to back up because of target overflow.
    ch = static_cast<uint16_t>(*source++);
    // If we have a surrogate pair, convert to UChar32 first.
    if (ch >= 0xD800 && ch <= 0xDBFF) {
      // If the 16 bits following the high surrogate are in the source buffer...
      if (source < sourceEnd) {
        UChar32 ch2 = static_cast<uint16_t>(*source);
        // If it's a low surrogate, convert to UChar32.
        if (ch2 >= 0xDC00 && ch2 <= 0xDFFF) {
          ch = ((ch - 0xD800) << 10) + (ch2 - 0xDC00) + 0x0010000;
          ++source;
        } else if (strict) {  // it's an unpaired high surrogate
          --source;           // return to the illegal value itself
          result = sourceIllegal;
          break;
        }
      } else {     // We don't have the 16 bits following the high surrogate.
        --source;  // return to the high surrogate
        result = sourceExhausted;
        break;
      }
    } else if (strict) {
      // UTF-16 surrogate values are illegal in UTF-32
      if (ch >= 0xDC00 && ch <= 0xDFFF) {
        --source;  // return to the illegal value itself
        result = sourceIllegal;
        break;
      }
    }
    // Figure out how many bytes the result will require
    if (ch < (UChar32)0x80) {
      bytesToWrite = 1;
    } else if (ch < (UChar32)0x800) {
      bytesToWrite = 2;
    } else if (ch < (UChar32)0x10000) {
      bytesToWrite = 3;
    } else if (ch < (UChar32)0x110000) {
      bytesToWrite = 4;
    } else {
      bytesToWrite = 3;
      ch = replacementCharacter;
    }

    target += bytesToWrite;
    if (target > targetEnd) {
      source = oldSource;  // Back up source pointer!
      target -= bytesToWrite;
      result = targetExhausted;
      break;
    }
    switch (bytesToWrite) {  // note: everything falls through.
      case 4:
        *--target = static_cast<char>((ch | byteMark) & byteMask);
        ch >>= 6;
      case 3:
        *--target = static_cast<char>((ch | byteMark) & byteMask);
        ch >>= 6;
      case 2:
        *--target = static_cast<char>((ch | byteMark) & byteMask);
        ch >>= 6;
      case 1:
        *--target = static_cast<char>(ch | firstByteMark[bytesToWrite]);
    }
    target += bytesToWrite;
  }
  *sourceStart = source;
  *targetStart = target;
  return result;
}

/**
 * Is this code point a BMP code point (U+0000..U+ffff)?
 * @param c 32-bit code point
 * @return TRUE or FALSE
 * @stable ICU 2.8
 */
#define U_IS_BMP(c) ((uint32_t)(c) <= 0xffff)

/**
 * Is this code point a supplementary code point (U+10000..U+10ffff)?
 * @param c 32-bit code point
 * @return TRUE or FALSE
 * @stable ICU 2.8
 */
#define U_IS_SUPPLEMENTARY(c) ((uint32_t)((c)-0x10000) <= 0xfffff)

/**
 * Is this code point a surrogate (U+d800..U+dfff)?
 * @param c 32-bit code point
 * @return TRUE or FALSE
 * @stable ICU 2.4
 */
#define U_IS_SURROGATE(c) (((c)&0xfffff800) == 0xd800)

/**
 * Get the lead surrogate (0xd800..0xdbff) for a
 * supplementary code point (0x10000..0x10ffff).
 * @param supplementary 32-bit code point (U+10000..U+10ffff)
 * @return lead surrogate (U+d800..U+dbff) for supplementary
 * @stable ICU 2.4
 */
#define U16_LEAD(supplementary) (UChar)(((supplementary) >> 10) + 0xd7c0)

/**
 * Get the trail surrogate (0xdc00..0xdfff) for a
 * supplementary code point (0x10000..0x10ffff).
 * @param supplementary 32-bit code point (U+10000..U+10ffff)
 * @return trail surrogate (U+dc00..U+dfff) for supplementary
 * @stable ICU 2.4
 */
#define U16_TRAIL(supplementary) (UChar)(((supplementary)&0x3ff) | 0xdc00)

// This must be called with the length pre-determined by the first byte.
// If presented with a length > 4, this returns false.  The Unicode
// definition of UTF-8 goes up to 4-byte sequences.
static bool isLegalUTF8(const unsigned char* source, int length) {
  unsigned char a;
  const unsigned char* srcptr = source + length;
  switch (length) {
    default:
      return false;
    // Everything else falls through when "true"...
    case 4:
      if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;
    case 3:
      if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;
    case 2:
      if ((a = (*--srcptr)) > 0xBF) return false;

      // no fall-through in this inner switch
      switch (*source) {
        case 0xE0:
          if (a < 0xA0) return false;
          break;
        case 0xED:
          if (a > 0x9F) return false;
          break;
        case 0xF0:
          if (a < 0x90) return false;
          break;
        case 0xF4:
          if (a > 0x8F) return false;
          break;
        default:
          if (a < 0x80) return false;
      }

    case 1:
      if (*source >= 0x80 && *source < 0xC2) return false;
  }
  if (*source > 0xF4) return false;
  return true;
}

// Magic values subtracted from a buffer value during UTF8 conversion.
// This table contains as many values as there might be trailing bytes
// in a UTF-8 sequence.
static const UChar32 offsetsFromUTF8[6] = {0x00000000UL,
                                           0x00003080UL,
                                           0x000E2080UL,
                                           0x03C82080UL,
                                           static_cast<UChar32>(0xFA082080UL),
                                           static_cast<UChar32>(0x82082080UL)};

static inline UChar32 readUTF8Sequence(const char*& sequence, size_t length) {
  UChar32 character = 0;

  // The cases all fall through.
  switch (length) {
    case 6:
      character += static_cast<unsigned char>(*sequence++);
      character <<= 6;
    case 5:
      character += static_cast<unsigned char>(*sequence++);
      character <<= 6;
    case 4:
      character += static_cast<unsigned char>(*sequence++);
      character <<= 6;
    case 3:
      character += static_cast<unsigned char>(*sequence++);
      character <<= 6;
    case 2:
      character += static_cast<unsigned char>(*sequence++);
      character <<= 6;
    case 1:
      character += static_cast<unsigned char>(*sequence++);
  }

  return character - offsetsFromUTF8[length - 1];
}

ConversionResult convertUTF8ToUTF16(const char** sourceStart,
                                    const char* sourceEnd, UChar** targetStart,
                                    UChar* targetEnd, bool* sourceAllASCII,
                                    bool strict) {
  ConversionResult result = conversionOK;
  const char* source = *sourceStart;
  UChar* target = *targetStart;
  UChar orAllData = 0;
  while (source < sourceEnd) {
    int utf8SequenceLength = inlineUTF8SequenceLength(*source);
    if (sourceEnd - source < utf8SequenceLength) {
      result = sourceExhausted;
      break;
    }
    // Do this check whether lenient or strict
    if (!isLegalUTF8(reinterpret_cast<const unsigned char*>(source),
                     utf8SequenceLength)) {
      result = sourceIllegal;
      break;
    }

    UChar32 character = readUTF8Sequence(source, utf8SequenceLength);

    if (target >= targetEnd) {
      source -= utf8SequenceLength;  // Back up source pointer!
      result = targetExhausted;
      break;
    }

    if (U_IS_BMP(character)) {
      // UTF-16 surrogate values are illegal in UTF-32
      if (U_IS_SURROGATE(character)) {
        if (strict) {
          source -= utf8SequenceLength;  // return to the illegal value itself
          result = sourceIllegal;
          break;
        }
        *target++ = replacementCharacter;
        orAllData |= replacementCharacter;
      } else {
        *target++ = static_cast<UChar>(character);  // normal case
        orAllData |= character;
      }
    } else if (U_IS_SUPPLEMENTARY(character)) {
      // target is a character in range 0xFFFF - 0x10FFFF
      if (target + 1 >= targetEnd) {
        source -= utf8SequenceLength;  // Back up source pointer!
        result = targetExhausted;
        break;
      }
      *target++ = U16_LEAD(character);
      *target++ = U16_TRAIL(character);
      orAllData = 0xffff;
    } else {
      if (strict) {
        source -= utf8SequenceLength;  // return to the start
        result = sourceIllegal;
        break;  // Bail out; shouldn't continue
      } else {
        *target++ = replacementCharacter;
        orAllData |= replacementCharacter;
      }
    }
  }
  *sourceStart = source;
  *targetStart = target;

  if (sourceAllASCII) *sourceAllASCII = !(orAllData & ~0x7f);

  return result;
}

// Helper to write a three-byte UTF-8 code point to the buffer, caller must
// check room is available.
static inline void putUTF8Triple(char*& buffer, UChar ch) {
  *buffer++ = static_cast<char>(((ch >> 12) & 0x0F) | 0xE0);
  *buffer++ = static_cast<char>(((ch >> 6) & 0x3F) | 0x80);
  *buffer++ = static_cast<char>((ch & 0x3F) | 0x80);
}

}  // namespace

// static
String16 String16::fromInteger(int number) {
  char arr[50];
  v8::internal::Vector<char> buffer(arr, arraysize(arr));
  return String16(IntToCString(number, buffer));
}

// static
String16 String16::fromInteger(size_t number) {
  const size_t kBufferSize = 50;
  char buffer[kBufferSize];
#if !defined(_WIN32) && !defined(_WIN64)
  v8::base::OS::SNPrintF(buffer, kBufferSize, "%zu", number);
#else
  v8::base::OS::SNPrintF(buffer, kBufferSize, "%Iu", number);
#endif
  return String16(buffer);
}

// static
String16 String16::fromDouble(double number) {
  char arr[50];
  v8::internal::Vector<char> buffer(arr, arraysize(arr));
  return String16(DoubleToCString(number, buffer));
}

// static
String16 String16::fromDouble(double number, int precision) {
  std::unique_ptr<char[]> str(
      v8::internal::DoubleToPrecisionCString(number, precision));
  return String16(str.get());
}

int String16::toInteger(bool* ok) const {
  return charactersToInteger(characters16(), length(), ok);
}

String16 String16::stripWhiteSpace() const {
  if (!length()) return String16();

  size_t start = 0;
  size_t end = length() - 1;

  // skip white space from start
  while (start <= end && isSpaceOrNewLine(characters16()[start])) ++start;

  // only white space
  if (start > end) return String16();

  // skip white space from end
  while (end && isSpaceOrNewLine(characters16()[end])) --end;

  if (!start && end == length() - 1) return *this;
  return String16(characters16() + start, end + 1 - start);
}

String16Builder::String16Builder() {}

void String16Builder::append(const String16& s) {
  m_buffer.insert(m_buffer.end(), s.characters16(),
                  s.characters16() + s.length());
}

void String16Builder::append(UChar c) { m_buffer.push_back(c); }

void String16Builder::append(char c) {
  UChar u = c;
  m_buffer.push_back(u);
}

void String16Builder::append(const UChar* characters, size_t length) {
  m_buffer.insert(m_buffer.end(), characters, characters + length);
}

void String16Builder::append(const char* characters, size_t length) {
  m_buffer.insert(m_buffer.end(), characters, characters + length);
}

void String16Builder::appendNumber(int number) {
  const int kBufferSize = 11;
  char buffer[kBufferSize];
  int chars = v8::base::OS::SNPrintF(buffer, kBufferSize, "%d", number);
  DCHECK_GT(kBufferSize, chars);
  m_buffer.insert(m_buffer.end(), buffer, buffer + chars);
}

void String16Builder::appendNumber(size_t number) {
  const int kBufferSize = 20;
  char buffer[kBufferSize];
#if !defined(_WIN32) && !defined(_WIN64)
  int chars = v8::base::OS::SNPrintF(buffer, kBufferSize, "%zu", number);
#else
  int chars = v8::base::OS::SNPrintF(buffer, kBufferSize, "%Iu", number);
#endif
  DCHECK_GT(kBufferSize, chars);
  m_buffer.insert(m_buffer.end(), buffer, buffer + chars);
}

String16 String16Builder::toString() {
  return String16(m_buffer.data(), m_buffer.size());
}

void String16Builder::reserveCapacity(size_t capacity) {
  m_buffer.reserve(capacity);
}

String16 String16::fromUTF8(const char* stringStart, size_t length) {
  if (!stringStart || !length) return String16();

  std::vector<UChar> buffer(length);
  UChar* bufferStart = buffer.data();

  UChar* bufferCurrent = bufferStart;
  const char* stringCurrent = stringStart;
  if (convertUTF8ToUTF16(&stringCurrent, stringStart + length, &bufferCurrent,
                         bufferCurrent + buffer.size(), 0,
                         true) != conversionOK)
    return String16();

  size_t utf16Length = bufferCurrent - bufferStart;
  return String16(bufferStart, utf16Length);
}

std::string String16::utf8() const {
  size_t length = this->length();

  if (!length) return std::string("");

  // Allocate a buffer big enough to hold all the characters
  // (an individual UTF-16 UChar can only expand to 3 UTF-8 bytes).
  // Optimization ideas, if we find this function is hot:
  //  * We could speculatively create a CStringBuffer to contain 'length'
  //    characters, and resize if necessary (i.e. if the buffer contains
  //    non-ascii characters). (Alternatively, scan the buffer first for
  //    ascii characters, so we know this will be sufficient).
  //  * We could allocate a CStringBuffer with an appropriate size to
  //    have a good chance of being able to write the string into the
  //    buffer without reallocing (say, 1.5 x length).
  if (length > std::numeric_limits<unsigned>::max() / 3) return std::string();
  std::vector<char> bufferVector(length * 3);
  char* buffer = bufferVector.data();
  const UChar* characters = m_impl.data();

  ConversionResult result =
      convertUTF16ToUTF8(&characters, characters + length, &buffer,
                         buffer + bufferVector.size(), false);
  DCHECK(
      result !=
      targetExhausted);  // (length * 3) should be sufficient for any conversion

  // Only produced from strict conversion.
  DCHECK(result != sourceIllegal);

  // Check for an unconverted high surrogate.
  if (result == sourceExhausted) {
    // This should be one unpaired high surrogate. Treat it the same
    // was as an unpaired high surrogate would have been handled in
    // the middle of a string with non-strict conversion - which is
    // to say, simply encode it to UTF-8.
    DCHECK((characters + 1) == (m_impl.data() + length));
    DCHECK((*characters >= 0xD800) && (*characters <= 0xDBFF));
    // There should be room left, since one UChar hasn't been
    // converted.
    DCHECK((buffer + 3) <= (buffer + bufferVector.size()));
    putUTF8Triple(buffer, *characters);
  }

  return std::string(bufferVector.data(), buffer - bufferVector.data());
}

}  // namespace v8_inspector