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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
/*
* A class which represents a fragment of text (eg inside a text
* node); if only codepoints below 256 are used, the text is stored as
* a char*; otherwise the text is stored as a char16_t*
*/
#ifndef nsTextFragment_h___
#define nsTextFragment_h___
#include "mozilla/Attributes.h"
#include "mozilla/MemoryReporting.h"
#include "nsCharTraits.h"
#include "nsString.h"
#include "nsStringBuffer.h"
#include "nsReadableUtils.h"
#include "nsISupportsImpl.h"
// XXX should this normalize the code to keep a \u0000 at the end?
// XXX nsTextFragmentPool?
/**
* A fragment of text. If mIs2b is 1 then the m2b pointer is valid
* otherwise the m1b pointer is valid. If m1b is used then each byte
* of data represents a single ucs2 character with the high byte being
* zero.
*
* This class does not have a virtual destructor therefore it is not
* meant to be subclassed.
*/
class nsTextFragment final {
public:
static nsresult Init();
static void Shutdown();
/**
* Default constructor. Initialize the fragment to be empty.
*/
nsTextFragment() : m1b(nullptr), mAllBits(0) {
MOZ_COUNT_CTOR(nsTextFragment);
NS_ASSERTION(sizeof(FragmentBits) == 4, "Bad field packing!");
}
~nsTextFragment();
/**
* Change the contents of this fragment to be a copy of the
* the argument fragment, or to "" if unable to allocate enough memory.
*/
nsTextFragment& operator=(const nsTextFragment& aOther);
/**
* Return true if this fragment is represented by char16_t data
*/
bool Is2b() const { return mState.mIs2b; }
/**
* Return true if this fragment contains Bidi text
* For performance reasons this flag is only set if explicitely requested (by
* setting the aUpdateBidi argument on SetTo or Append to true).
*/
bool IsBidi() const { return mState.mIsBidi; }
/**
* Get a pointer to constant char16_t data.
*/
const char16_t* Get2b() const {
MOZ_ASSERT(Is2b(), "not 2b text");
return static_cast<char16_t*>(m2b->Data());
}
/**
* Get a pointer to constant char data.
*/
const char* Get1b() const {
NS_ASSERTION(!Is2b(), "not 1b text");
return (const char*)m1b;
}
/**
* Get the length of the fragment. The length is the number of logical
* characters, not the number of bytes to store the characters.
*/
uint32_t GetLength() const { return mState.mLength; }
#define NS_MAX_TEXT_FRAGMENT_LENGTH (static_cast<uint32_t>(0x1FFFFFFF))
bool CanGrowBy(size_t n) const {
return n < (1 << 29) && mState.mLength + n < (1 << 29);
}
/**
* Change the contents of this fragment to be a copy of the given
* buffer. If aUpdateBidi is true, contents of the fragment will be scanned,
* and mState.mIsBidi will be turned on if it includes any Bidi characters.
* If aForce2b is true, aBuffer will be stored as char16_t as is. Then,
* you can access the value faster but may waste memory if all characters
* are less than U+0100.
*/
bool SetTo(const char16_t* aBuffer, uint32_t aLength, bool aUpdateBidi,
bool aForce2b);
bool SetTo(const nsString& aString, bool aUpdateBidi, bool aForce2b) {
if (MOZ_UNLIKELY(aString.Length() > NS_MAX_TEXT_FRAGMENT_LENGTH)) {
return false;
}
ReleaseText();
if (aForce2b && !aUpdateBidi) {
nsStringBuffer* buffer = nsStringBuffer::FromString(aString);
if (buffer) {
NS_ADDREF(m2b = buffer);
mState.mInHeap = true;
mState.mIs2b = true;
mState.mLength = aString.Length();
return true;
}
}
return SetTo(aString.get(), aString.Length(), aUpdateBidi, aForce2b);
}
/**
* Append aData to the end of this fragment. If aUpdateBidi is true, contents
* of the fragment will be scanned, and mState.mIsBidi will be turned on if
* it includes any Bidi characters.
* If aForce2b is true, the string will be stored as char16_t as is. Then,
* you can access the value faster but may waste memory if all characters
* are less than U+0100.
*/
bool Append(const char16_t* aBuffer, uint32_t aLength, bool aUpdateBidi,
bool aForce2b);
/**
* Append the contents of this string fragment to aString
*/
void AppendTo(nsAString& aString) const {
if (!AppendTo(aString, mozilla::fallible)) {
aString.AllocFailed(aString.Length() + GetLength());
}
}
/**
* Append the contents of this string fragment to aString
* @return false if an out of memory condition is detected, true otherwise
*/
[[nodiscard]] bool AppendTo(nsAString& aString,
const mozilla::fallible_t& aFallible) const {
if (mState.mIs2b) {
if (aString.IsEmpty()) {
m2b->ToString(mState.mLength, aString);
return true;
}
bool ok = aString.Append(Get2b(), mState.mLength, aFallible);
if (!ok) {
return false;
}
return true;
} else {
return AppendASCIItoUTF16(Substring(m1b, mState.mLength), aString,
aFallible);
}
}
/**
* Append a substring of the contents of this string fragment to aString.
* @param aOffset where to start the substring in this text fragment
* @param aLength the length of the substring
*/
void AppendTo(nsAString& aString, uint32_t aOffset, uint32_t aLength) const {
if (!AppendTo(aString, aOffset, aLength, mozilla::fallible)) {
aString.AllocFailed(aString.Length() + aLength);
}
}
/**
* Append a substring of the contents of this string fragment to aString.
* @param aString the string in which to append
* @param aOffset where to start the substring in this text fragment
* @param aLength the length of the substring
* @return false if an out of memory condition is detected, true otherwise
*/
[[nodiscard]] bool AppendTo(nsAString& aString, uint32_t aOffset,
uint32_t aLength,
const mozilla::fallible_t& aFallible) const {
if (mState.mIs2b) {
bool ok = aString.Append(Get2b() + aOffset, aLength, aFallible);
if (!ok) {
return false;
}
return true;
} else {
return AppendASCIItoUTF16(Substring(m1b + aOffset, aLength), aString,
aFallible);
}
}
/**
* Make a copy of the fragments contents starting at offset for
* count characters. The offset and count will be adjusted to
* lie within the fragments data. The fragments data is converted if
* necessary.
*/
void CopyTo(char16_t* aDest, uint32_t aOffset, uint32_t aCount);
/**
* Return the character in the text-fragment at the given
* index. This always returns a char16_t.
*/
char16_t CharAt(uint32_t aIndex) const {
MOZ_ASSERT(aIndex < mState.mLength, "bad index");
return mState.mIs2b ? Get2b()[aIndex]
: static_cast<unsigned char>(m1b[aIndex]);
}
/**
* IsHighSurrogateFollowedByLowSurrogateAt() returns true if character at
* aIndex is high surrogate and it's followed by low surrogate.
*/
inline bool IsHighSurrogateFollowedByLowSurrogateAt(uint32_t aIndex) const {
MOZ_ASSERT(aIndex < mState.mLength);
if (!mState.mIs2b || aIndex + 1 >= mState.mLength) {
return false;
}
return NS_IS_SURROGATE_PAIR(Get2b()[aIndex], Get2b()[aIndex + 1]);
}
/**
* IsLowSurrogateFollowingHighSurrogateAt() returns true if character at
* aIndex is low surrogate and it follows high surrogate.
*/
inline bool IsLowSurrogateFollowingHighSurrogateAt(uint32_t aIndex) const {
MOZ_ASSERT(aIndex < mState.mLength);
if (!mState.mIs2b || !aIndex) {
return false;
}
return NS_IS_SURROGATE_PAIR(Get2b()[aIndex - 1], Get2b()[aIndex]);
}
/**
* ScalarValueAt() returns a Unicode scalar value at aIndex. If the character
* at aIndex is a high surrogate followed by low surrogate, returns character
* code for the pair. If the index is low surrogate, or a high surrogate but
* not in a pair, returns 0.
*/
inline char32_t ScalarValueAt(uint32_t aIndex) const {
MOZ_ASSERT(aIndex < mState.mLength);
if (!mState.mIs2b) {
return static_cast<unsigned char>(m1b[aIndex]);
}
char16_t ch = Get2b()[aIndex];
if (!IS_SURROGATE(ch)) {
return ch;
}
if (aIndex + 1 < mState.mLength && NS_IS_HIGH_SURROGATE(ch)) {
char16_t nextCh = Get2b()[aIndex + 1];
if (NS_IS_LOW_SURROGATE(nextCh)) {
return SURROGATE_TO_UCS4(ch, nextCh);
}
}
return 0;
}
void SetBidi(bool aBidi) { mState.mIsBidi = aBidi; }
struct FragmentBits {
// uint32_t to ensure that the values are unsigned, because we
// want 0/1, not 0/-1!
// Making these bool causes Windows to not actually pack them,
// which causes crashes because we assume this structure is no more than
// 32 bits!
uint32_t mInHeap : 1;
uint32_t mIs2b : 1;
uint32_t mIsBidi : 1;
// Note that when you change the bits of mLength, you also need to change
// NS_MAX_TEXT_FRAGMENT_LENGTH.
uint32_t mLength : 29;
};
size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
/**
* Check whether the text in this fragment is the same as the text in the
* other fragment.
*/
[[nodiscard]] bool TextEquals(const nsTextFragment& aOther) const;
private:
void ReleaseText();
/**
* Scan the contents of the fragment and turn on mState.mIsBidi if it
* includes any Bidi characters.
*/
void UpdateBidiFlag(const char16_t* aBuffer, uint32_t aLength);
union {
nsStringBuffer* m2b;
const char* m1b; // This is const since it can point to shared data
};
union {
uint32_t mAllBits;
FragmentBits mState;
};
};
#endif /* nsTextFragment_h___ */