ustring.h

/*
 *  This file is part of the KDE libraries
 *  Copyright (C) 1999-2000 Harri Porten ([email protected])
 *  Copyright (C) 2004 Apple Computer, Inc.
 *
 *  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 "kjs/global.h"

#include <wtf/AlwaysInline.h>
#include <wtf/FastMalloc.h>
#include <wtf/RefPtr.h>
#include <wtf/PassRefPtr.h>
#include <wtf/Vector.h>

#include <assert.h>
#include "collector.h"
#if HAVE_STDINT_H
#include <stdint.h>
#endif

/* 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 defined(WTF_COMPILER_GCC) && PLATFORM(FORCE_PACK)
#define PACK_STRUCT __attribute__((packed))
#else
#define PACK_STRUCT
#endif

/**
 * @internal
 */
namespace DOM
{
class DOMString;
}
class QString;
class QConstString;

namespace KJS
{

class UString;

/**
 * @short Unicode character.
 *
 * UChar represents a 16 bit Unicode character. Its internal data
 * representation is compatible to XChar2b and QChar. It's therefore
 * possible to exchange data with X and Qt with shallow copies.
 */
struct KJS_EXPORT 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 KJS_EXPORT CString
{
public:
    CString() : data(nullptr), length(0) { }
    CString(const char *c);
    CString(const char *c, size_t len);
    CString(const CString &);

    ~CString();

    CString &operator=(const char *c);
    CString &operator=(const CString &);

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

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

public:
    /**
     * @internal
     */
    struct KJS_EXPORT 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);    // fast path for Identifiers
            return _hash;
        }
        static unsigned computeHash(const UChar *, int length);
        static unsigned computeHash(const char *s, int length);
        static unsigned computeHash(const char *);

        Rep *ref()
        {
            ++rc;
            return this;
        }
        ALWAYS_INLINE void deref()
        {
            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 an empty string.
     */
    enum Empty { empty };
    UString(Empty);
    /**
     * Constructs a string from the single character c.
     */
    explicit UString(char c);
    /**
     * Constructs a string from a classical zero determined char string.
     */
    UString(const char *c);
    UString(const char *c, size_t length);
    /**
     * 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 &operator=(const UString &s) { m_rep = s.m_rep; return *this; }

    UString(const Vector<UChar> &buffer);

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

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

    /**
     * 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);

    static bool equal(const UString::Rep *a, const UString::Rep *b);

    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 &subStr, int subPos, int subLength = -1);
    UString &append(const UString &t);
    UString &append(const char *t);
    UString &append(const char *t, int tSize);
    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().
     */
    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.
     * Since 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.
     */
    CString UTF8String() const;

    /**
     * @see UString(const QString&).
     */
    KJS_EXTERNAL_EXPORT DOM::DOMString domString() const;
    /**
     * @see UString(const QString&).
     */
    KJS_EXTERNAL_EXPORT QString qstring() const;
    /**
     * @see UString(const QString&).
     */
    KJS_EXTERNAL_EXPORT QConstString qconststring() const;

    /**
     * Assignment operator.
     */
    UString &operator=(const char *c);
    UString &operator=(Empty);
    /**
     * 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.
     */
    uint32_t toStrictUInt32(bool *ok = nullptr) 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 = nullptr) 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();

    /**
     * Maximum permitted string length
     * @since 5.20
     */
    static size_t maxUChars();

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

    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);
    void set(const char *c, int len);

    RefPtr<Rep> m_rep;
};

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

KJS_EXPORT int compare(const UString &, const UString &);

// Given a first byte, gives the length of the UTF-8 sequence it begins.
// Returns 0 for bytes that are not legal starts of UTF-8 sequences.
// Only allows sequences of up to 4 bytes, since that works for all Unicode characters (U-00000000 to U-0010FFFF).
int UTF8SequenceLength(char);

// Takes a null-terminated C-style string with a UTF-8 sequence in it and converts it to a character.
// Only allows Unicode characters (U-00000000 to U-0010FFFF).
// Returns -1 if the sequence is not valid (including presence of extra bytes).
int decodeUTF8Sequence(const char *);

KJS_EXPORT 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

namespace WTF
{

template<typename T> struct DefaultHash;
template<typename T> struct StrHash;

template<> struct StrHash<KJS::UString::Rep *> {
    static unsigned hash(const KJS::UString::Rep *key)
    {
        return key->hash();
    }
    static bool equal(const KJS::UString::Rep *a, const KJS::UString::Rep *b)
    {
        return KJS::UString::equal(a, b);
    }
    static const bool safeToCompareToEmptyOrDeleted = false;
};

template<> struct DefaultHash<KJS::UString::Rep *> {
    typedef StrHash<KJS::UString::Rep *> Hash;
};
} // namespace WTF

#endif