JavaScriptCore/kjs/ustring.h

// -*- c-basic-offset: 2 -*-
/*
 *  Copyright (C) 1999-2000 Harri Porten (porten@kde.org)
 *  Copyright (C) 2004, 2005, 2006, 2007 Apple Inc. All rights reserved.
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Library General Public
 *  License as published by the Free Software Foundation; either
 *  version 2 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Library General Public License for more details.
 *
 *  You should have received a copy of the GNU Library General Public License
 *  along with this library; see the file COPYING.LIB.  If not, write to
 *  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 *  Boston, MA 02110-1301, USA.
 *
 */

#ifndef _KJS_USTRING_H_
#define _KJS_USTRING_H_

#include "JSLock.h"
#include "collector.h"
#include <stdint.h>
#include <wtf/Assertions.h>
#include <wtf/FastMalloc.h>
#include <wtf/PassRefPtr.h>
#include <wtf/RefPtr.h>
#include <wtf/Vector.h>

/* On some ARM platforms GCC won't pack structures by default so sizeof(UChar)
   will end up being != 2 which causes crashes since the code depends on that. */
#if COMPILER(GCC) && PLATFORM(FORCE_PACK)
#define PACK_STRUCT __attribute__((packed))
#else
#define PACK_STRUCT
#endif

/**
 * @internal
 */
namespace DOM {
  class DOMString;
  class AtomicString;
}
class KJScript;

namespace KJS {

  using WTF::PlacementNewAdoptType;
  using WTF::PlacementNewAdopt;

  class UString;

  /**
   * @short Unicode character.
   *
   * UChar represents a 16 bit Unicode character. It's internal data
   * representation is compatible to XChar2b and QChar. It's therefore
   * possible to exchange data with X and Qt with shallow copies.
   */
  struct UChar {
    /**
     * Construct a character with uninitialized value.    
     */
    UChar();
    /**
     * Construct a character with the value denoted by the arguments.
     * @param h higher byte
     * @param l lower byte
     */
    UChar(unsigned char h , unsigned char l);
    /**
     * Construct a character with the given value.
     * @param u 16 bit Unicode value
     */
    UChar(char u);
    UChar(unsigned char u);
    UChar(unsigned short u);
    /**
     * @return The higher byte of the character.
     */
    unsigned char high() const { return static_cast<unsigned char>(uc >> 8); }
    /**
     * @return The lower byte of the character.
     */
    unsigned char low() const { return static_cast<unsigned char>(uc); }
    /**
     * @return the 16 bit Unicode value of the character
     */
    unsigned short unicode() const { return uc; }

    unsigned short uc;
  } PACK_STRUCT;

  inline UChar::UChar() { }
  inline UChar::UChar(unsigned char h , unsigned char l) : uc(h << 8 | l) { }
  inline UChar::UChar(char u) : uc((unsigned char)u) { }
  inline UChar::UChar(unsigned char u) : uc(u) { }
  inline UChar::UChar(unsigned short u) : uc(u) { }

  /**
   * @short 8 bit char based string class
   */
  class CString {
  public:
    CString() : data(0), length(0) { }
    CString(const char *c);
    CString(const char *c, size_t len);
    CString(const CString &);

    ~CString();

    CString &append(const CString &);
    CString &operator=(const char *c);
    CString &operator=(const CString &);
    CString &operator+=(const CString &c) { return append(c); }

    size_t size() const { return length; }
    const char *c_str() const { return data; }
  private:
    char *data;
    size_t length;
  };

  /**
   * @short Unicode string class
   */
  class UString {
    friend bool operator==(const UString&, const UString&);

  public:
    /**
     * @internal
     */
    struct Rep {

      static PassRefPtr<Rep> create(UChar *d, int l);
      static PassRefPtr<Rep> createCopying(const UChar *d, int l);
      static PassRefPtr<Rep> create(PassRefPtr<Rep> base, int offset, int length);

      void destroy();
      
      bool baseIsSelf() const { return baseString == this; }
      UChar* data() const { return baseString->buf + baseString->preCapacity + offset; }
      int size() const { return len; }
      
      unsigned hash() const { if (_hash == 0) _hash = computeHash(data(), len); return _hash; }
      unsigned computedHash() const { ASSERT(_hash); return _hash; } // fast path for Identifiers

      static unsigned computeHash(const UChar *, int length);
      static unsigned computeHash(const char *);

      Rep* ref() { ASSERT(JSLock::lockCount() > 0); ++rc; return this; }
      ALWAYS_INLINE void deref() { ASSERT(JSLock::lockCount() > 0); if (--rc == 0) destroy(); }

      // unshared data
      int offset;
      int len;
      int rc;
      mutable unsigned _hash;
      bool isIdentifier;
      UString::Rep* baseString;
      size_t reportedCost;

      // potentially shared data
      UChar *buf;
      int usedCapacity;
      int capacity;
      int usedPreCapacity;
      int preCapacity;
      
      static Rep null;
      static Rep empty;
    };

  public:

    /**
     * Constructs a null string.
     */
    UString();
    /**
     * Constructs a string from a classical zero-terminated char string.
     */
    UString(const char *c);
    /**
     * Constructs a string from an array of Unicode characters of the specified
     * length.
     */
    UString(const UChar *c, int length);
    /**
     * If copy is false the string data will be adopted.
     * That means that the data will NOT be copied and the pointer will
     * be deleted when the UString object is modified or destroyed.
     * Behaviour defaults to a deep copy if copy is true.
     */
    UString(UChar *c, int length, bool copy);
    /**
     * Copy constructor. Makes a shallow copy only.
     */
    UString(const UString &s) : m_rep(s.m_rep) {}

    UString(const Vector<UChar>& buffer);

    /**
     * Convenience declaration only ! You'll be on your own to write the
     * implementation for a construction from DOM::DOMString.
     *
     * Note: feel free to contact me if you want to see a dummy header for
     * your favorite FooString class here !
     */
    UString(const DOM::DOMString&);
    /**
     * Convenience declaration only ! See UString(const DOM::DOMString&).
     */
    UString(const DOM::AtomicString&);

    /**
     * Concatenation constructor. Makes operator+ more efficient.
     */
    UString(const UString &, const UString &);
    /**
     * Destructor.
     */
    ~UString() {}

    // Special constructor for cases where we overwrite an object in place.
    UString(PlacementNewAdoptType) : m_rep(PlacementNewAdopt) { }

    /**
     * Constructs a string from an int.
     */
    static UString from(int i);
    /**
     * Constructs a string from an unsigned int.
     */
    static UString from(unsigned int u);
    /**
     * Constructs a string from a long int.
     */
    static UString from(long u);
    /**
     * Constructs a string from a double.
     */
    static UString from(double d);

    struct Range {
    public:
      Range(int pos, int len) : position(pos), length(len) {}
      Range() {}
      int position;
      int length;
    };

    UString spliceSubstringsWithSeparators(const Range *substringRanges, int rangeCount, const UString *separators, int separatorCount) const;

    /**
     * Append another string.
     */
    UString &append(const UString &);
    UString &append(const char *);
    UString &append(unsigned short);
    UString &append(char c) { return append(static_cast<unsigned short>(static_cast<unsigned char>(c))); }
    UString &append(UChar c) { return append(c.uc); }

    /**
     * @return The string converted to the 8-bit string type CString().
     * This method is not Unicode safe and shouldn't be used unless the string
     * is known to be ASCII.
     */
    CString cstring() const;
    /**
     * Convert the Unicode string to plain ASCII chars chopping of any higher
     * bytes. This method should only be used for *debugging* purposes as it
     * is neither Unicode safe nor free from side effects. In order not to
     * waste any memory the char buffer is static and *shared* by all UString
     * instances.
     */
    char *ascii() const;

    /**
     * Convert the string to UTF-8, assuming it is UTF-16 encoded.
     * In non-strict mode, this function is tolerant of badly formed UTF-16, it
     * can create UTF-8 strings that are invalid because they have characters in
     * the range U+D800-U+DDFF, U+FFFE, or U+FFFF, but the UTF-8 string is
     * guaranteed to be otherwise valid.
     * In strict mode, error is returned as null CString.
     */
    CString UTF8String(bool strict = false) const;

    /**
     * @see UString(const DOM::DOMString&).
     */
    DOM::DOMString domString() const;

    /**
     * Assignment operator.
     */
    UString &operator=(const char *c);
    /**
     * Appends the specified string.
     */
    UString &operator+=(const UString &s) { return append(s); }
    UString &operator+=(const char *s) { return append(s); }

    /**
     * @return A pointer to the internal Unicode data.
     */
    const UChar* data() const { return m_rep->data(); }
    /**
     * @return True if null.
     */
    bool isNull() const { return (m_rep == &Rep::null); }
    /**
     * @return True if null or zero length.
     */
    bool isEmpty() const { return (!m_rep->len); }
    /**
     * Use this if you want to make sure that this string is a plain ASCII
     * string. For example, if you don't want to lose any information when
     * using cstring() or ascii().
     *
     * @return True if the string doesn't contain any non-ASCII characters.
     */
    bool is8Bit() const;
    /**
     * @return The length of the string.
     */
    int size() const { return m_rep->size(); }
    /**
     * Const character at specified position.
     */
    const UChar operator[](int pos) const;

    /**
     * Attempts an conversion to a number. Apart from floating point numbers,
     * the algorithm will recognize hexadecimal representations (as
     * indicated by a 0x or 0X prefix) and +/- Infinity.
     * Returns NaN if the conversion failed.
     * @param tolerateTrailingJunk if true, toDouble can tolerate garbage after the number.
     * @param tolerateEmptyString if false, toDouble will turn an empty string into NaN rather than 0.
     */
    double toDouble(bool tolerateTrailingJunk, bool tolerateEmptyString) const;
    double toDouble(bool tolerateTrailingJunk) const;
    double toDouble() const;

    /**
     * Attempts an conversion to a 32-bit integer. ok will be set
     * according to the success.
     * @param tolerateEmptyString if false, toUInt32 will return false for *ok for an empty string.
     */
    uint32_t toUInt32(bool *ok = 0) const;
    uint32_t toUInt32(bool *ok, bool tolerateEmptyString) const;
    uint32_t toStrictUInt32(bool *ok = 0) const;

    /**
     * Attempts an conversion to an array index. The "ok" boolean will be set
     * to true if it is a valid array index according to the rule from
     * ECMA 15.2 about what an array index is. It must exactly match the string
     * form of an unsigned integer, and be less than 2^32 - 1.
     */
    unsigned toArrayIndex(bool *ok = 0) const;

    /**
     * @return Position of first occurrence of f starting at position pos.
     * -1 if the search was not successful.
     */
    int find(const UString &f, int pos = 0) const;
    int find(UChar, int pos = 0) const;
    /**
     * @return Position of first occurrence of f searching backwards from
     * position pos.
     * -1 if the search was not successful.
     */
    int rfind(const UString &f, int pos) const;
    int rfind(UChar, int pos) const;
    /**
     * @return The sub string starting at position pos and length len.
     */
    UString substr(int pos = 0, int len = -1) const;
    /**
     * Static instance of a null string.
     */
    static const UString &null();

    Rep* rep() const { return m_rep.get(); }
    UString(PassRefPtr<Rep> r) : m_rep(r) { ASSERT(m_rep); }

    size_t cost() const;

  private:
    size_t expandedSize(size_t size, size_t otherSize) const;
    int usedCapacity() const;
    int usedPreCapacity() const;
    void expandCapacity(int requiredLength);
    void expandPreCapacity(int requiredPreCap);

    RefPtr<Rep> m_rep;
  };

  inline bool operator==(const UChar &c1, const UChar &c2) {
    return (c1.uc == c2.uc);
  }
  bool operator==(const UString& s1, const UString& s2);
  inline bool operator!=(const UString& s1, const UString& s2) {
    return !KJS::operator==(s1, s2);
  }
  bool operator<(const UString& s1, const UString& s2);
  bool operator==(const UString& s1, const char *s2);
  inline bool operator!=(const UString& s1, const char *s2) {
    return !KJS::operator==(s1, s2);
  }
  inline bool operator==(const char *s1, const UString& s2) {
    return operator==(s2, s1);
  }
  inline bool operator!=(const char *s1, const UString& s2) {
    return !KJS::operator==(s1, s2);
  }
  bool operator==(const CString& s1, const CString& s2);
  inline UString operator+(const UString& s1, const UString& s2) {
    return UString(s1, s2);
  }
  
  int compare(const UString &, const UString &);

inline UString::UString()
  : m_rep(&Rep::null)
{
}

// Rule from ECMA 15.2 about what an array index is.
// Must exactly match string form of an unsigned integer, and be less than 2^32 - 1.
inline unsigned UString::toArrayIndex(bool *ok) const
{
    unsigned i = toStrictUInt32(ok);
    if (ok && i >= 0xFFFFFFFFU)
        *ok = false;
    return i;
}

// We'd rather not do shared substring append for small strings, since
// this runs too much risk of a tiny initial string holding down a
// huge buffer.
// FIXME: this should be size_t but that would cause warnings until we
// fix UString sizes to be size_t instead of int
static const int minShareSize = Collector::minExtraCostSize / sizeof(UChar);

inline size_t UString::cost() const
{
   size_t capacity = (m_rep->baseString->capacity + m_rep->baseString->preCapacity) * sizeof(UChar);
   size_t reportedCost = m_rep->baseString->reportedCost;
   ASSERT(capacity >= reportedCost);

   size_t capacityDelta = capacity - reportedCost;

   if (capacityDelta < static_cast<size_t>(minShareSize))
       return 0;

   m_rep->baseString->reportedCost = capacity;
   return capacityDelta;
}

} // namespace

#endif