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gecko-dev/xpcom/string/nsUTF8Utils.h

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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
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef nsUTF8Utils_h_
#define nsUTF8Utils_h_
// This file may be used in two ways: if MOZILLA_INTERNAL_API is defined, this
// file will provide signatures for the Mozilla abstract string types. It will
// use XPCOM assertion/debugging macros, etc.
#include "nscore.h"
#include "mozilla/Assertions.h"
#include "mozilla/SSE.h"
#include "nsCharTraits.h"
class UTF8traits
{
public:
static bool isASCII(char aChar)
{
return (aChar & 0x80) == 0x00;
}
static bool isInSeq(char aChar)
{
return (aChar & 0xC0) == 0x80;
}
static bool is2byte(char aChar)
{
return (aChar & 0xE0) == 0xC0;
}
static bool is3byte(char aChar)
{
return (aChar & 0xF0) == 0xE0;
}
static bool is4byte(char aChar)
{
return (aChar & 0xF8) == 0xF0;
}
static bool is5byte(char aChar)
{
return (aChar & 0xFC) == 0xF8;
}
static bool is6byte(char aChar)
{
return (aChar & 0xFE) == 0xFC;
}
};
/**
* Extract the next UCS-4 character from the buffer and return it. The
* pointer passed in is advanced to the start of the next character in the
* buffer. If non-null, the parameters err and overlong are filled in to
* indicate that the character was represented by an overlong sequence, or
* that an error occurred.
*/
class UTF8CharEnumerator
{
public:
static uint32_t NextChar(const char** aBuffer, const char* aEnd, bool* aErr)
{
NS_ASSERTION(aBuffer && *aBuffer, "null buffer!");
const char* p = *aBuffer;
*aErr = false;
if (p >= aEnd) {
*aErr = true;
return 0;
}
char c = *p++;
if (UTF8traits::isASCII(c)) {
*aBuffer = p;
return c;
}
uint32_t ucs4;
uint32_t minUcs4;
int32_t state = 0;
if (!CalcState(c, ucs4, minUcs4, state)) {
NS_ERROR("Not a UTF-8 string. This code should only be used for converting from known UTF-8 strings.");
*aErr = true;
return 0;
}
while (state--) {
if (p == aEnd) {
*aErr = true;
return 0;
}
c = *p++;
if (!AddByte(c, state, ucs4)) {
*aErr = true;
return 0;
}
}
if (ucs4 < minUcs4) {
// Overlong sequence
ucs4 = UCS2_REPLACEMENT_CHAR;
} else if (ucs4 >= 0xD800 &&
(ucs4 <= 0xDFFF || ucs4 >= UCS_END)) {
// Surrogates and code points outside the Unicode range.
ucs4 = UCS2_REPLACEMENT_CHAR;
}
*aBuffer = p;
return ucs4;
}
private:
static bool CalcState(char aChar, uint32_t& aUcs4, uint32_t& aMinUcs4,
int32_t& aState)
{
if (UTF8traits::is2byte(aChar)) {
aUcs4 = (uint32_t(aChar) << 6) & 0x000007C0L;
aState = 1;
aMinUcs4 = 0x00000080;
} else if (UTF8traits::is3byte(aChar)) {
aUcs4 = (uint32_t(aChar) << 12) & 0x0000F000L;
aState = 2;
aMinUcs4 = 0x00000800;
} else if (UTF8traits::is4byte(aChar)) {
aUcs4 = (uint32_t(aChar) << 18) & 0x001F0000L;
aState = 3;
aMinUcs4 = 0x00010000;
} else if (UTF8traits::is5byte(aChar)) {
aUcs4 = (uint32_t(aChar) << 24) & 0x03000000L;
aState = 4;
aMinUcs4 = 0x00200000;
} else if (UTF8traits::is6byte(aChar)) {
aUcs4 = (uint32_t(aChar) << 30) & 0x40000000L;
aState = 5;
aMinUcs4 = 0x04000000;
} else {
return false;
}
return true;
}
static bool AddByte(char aChar, int32_t aState, uint32_t& aUcs4)
{
if (UTF8traits::isInSeq(aChar)) {
int32_t shift = aState * 6;
aUcs4 |= (uint32_t(aChar) & 0x3F) << shift;
return true;
}
return false;
}
};
/**
* Extract the next UCS-4 character from the buffer and return it. The
* pointer passed in is advanced to the start of the next character in the
* buffer. If non-null, the err parameter is filled in if an error occurs.
*
* If an error occurs that causes UCS2_REPLACEMENT_CHAR to be returned, then
* the buffer will be updated to move only a single UCS-2 character.
*
* Any other error returns 0 and does not move the buffer position.
*/
class UTF16CharEnumerator
{
public:
static uint32_t NextChar(const char16_t** aBuffer, const char16_t* aEnd,
bool* aErr = nullptr)
{
NS_ASSERTION(aBuffer && *aBuffer, "null buffer!");
const char16_t* p = *aBuffer;
if (p >= aEnd) {
NS_ERROR("No input to work with");
if (aErr) {
*aErr = true;
}
return 0;
}
char16_t c = *p++;
if (!IS_SURROGATE(c)) { // U+0000 - U+D7FF,U+E000 - U+FFFF
if (aErr) {
*aErr = false;
}
*aBuffer = p;
return c;
} else if (NS_IS_HIGH_SURROGATE(c)) { // U+D800 - U+DBFF
if (p == aEnd) {
// Found a high surrogate at the end of the buffer. Flag this
// as an error and return the Unicode replacement
// character 0xFFFD.
NS_WARNING("Unexpected end of buffer after high surrogate");
if (aErr) {
*aErr = true;
}
*aBuffer = p;
return 0xFFFD;
}
// D800- DBFF - High Surrogate
char16_t h = c;
c = *p++;
if (NS_IS_LOW_SURROGATE(c)) {
// DC00- DFFF - Low Surrogate
// N = (H - D800) *400 + 10000 + (L - DC00)
uint32_t ucs4 = SURROGATE_TO_UCS4(h, c);
if (aErr) {
*aErr = false;
}
*aBuffer = p;
return ucs4;
} else {
// Found a high surrogate followed by something other than
// a low surrogate. Flag this as an error and return the
// Unicode replacement character 0xFFFD. Note that the
// pointer to the next character points to the second 16-bit
// value, not beyond it, as per Unicode 5.0.0 Chapter 3 C10,
// only the first code unit of an illegal sequence must be
// treated as an illegally terminated code unit sequence
// (also Chapter 3 D91, "isolated [not paired and ill-formed]
// UTF-16 code units in the range D800..DFFF are ill-formed").
NS_WARNING("got a High Surrogate but no low surrogate");
if (aErr) {
*aErr = true;
}
*aBuffer = p - 1;
return 0xFFFD;
}
} else { // U+DC00 - U+DFFF
// DC00- DFFF - Low Surrogate
// Found a low surrogate w/o a preceding high surrogate. Flag
// this as an error and return the Unicode replacement
// character 0xFFFD.
NS_WARNING("got a low Surrogate but no high surrogate");
if (aErr) {
*aErr = true;
}
*aBuffer = p;
return 0xFFFD;
}
MOZ_ASSERT_UNREACHABLE("Impossible UCS-2 character value.");
}
};
/**
* A character sink (see |copy_string| in nsAlgorithm.h) for converting
* UTF-8 to UTF-16
*/
class ConvertUTF8toUTF16
{
public:
typedef char value_type;
typedef char16_t buffer_type;
explicit ConvertUTF8toUTF16(buffer_type* aBuffer)
: mStart(aBuffer), mBuffer(aBuffer), mErrorEncountered(false)
{
}
size_t Length() const
{
return mBuffer - mStart;
}
bool ErrorEncountered() const
{
return mErrorEncountered;
}
void write(const value_type* aStart, uint32_t aN)
{
if (mErrorEncountered) {
return;
}
// algorithm assumes utf8 units won't
// be spread across fragments
const value_type* p = aStart;
const value_type* end = aStart + aN;
buffer_type* out = mBuffer;
for (; p != end /* && *p */;) {
bool err;
uint32_t ucs4 = UTF8CharEnumerator::NextChar(&p, end, &err);
if (err) {
mErrorEncountered = true;
mBuffer = out;
return;
}
if (ucs4 >= PLANE1_BASE) {
*out++ = (buffer_type)H_SURROGATE(ucs4);
*out++ = (buffer_type)L_SURROGATE(ucs4);
} else {
*out++ = ucs4;
}
}
mBuffer = out;
}
void write_terminator()
{
*mBuffer = buffer_type(0);
}
private:
buffer_type* const mStart;
buffer_type* mBuffer;
bool mErrorEncountered;
};
/**
* A character sink (see |copy_string| in nsAlgorithm.h) for computing
* the length of the UTF-16 string equivalent to a UTF-8 string.
*/
class CalculateUTF8Length
{
public:
typedef char value_type;
CalculateUTF8Length()
: mLength(0), mErrorEncountered(false)
{
}
size_t Length() const
{
return mLength;
}
void write(const value_type* aStart, uint32_t aN)
{
// ignore any further requests
if (mErrorEncountered) {
return;
}
// algorithm assumes utf8 units won't
// be spread across fragments
const value_type* p = aStart;
const value_type* end = aStart + aN;
for (; p < end /* && *p */; ++mLength) {
if (UTF8traits::isASCII(*p)) {
p += 1;
} else if (UTF8traits::is2byte(*p)) {
p += 2;
} else if (UTF8traits::is3byte(*p)) {
p += 3;
} else if (UTF8traits::is4byte(*p)) {
// Because a UTF-8 sequence of 4 bytes represents a codepoint
// greater than 0xFFFF, it will become a surrogate pair in the
// UTF-16 string, so add 1 more to mLength.
// This doesn't happen with is5byte and is6byte because they
// are illegal UTF-8 sequences (greater than 0x10FFFF) so get
// converted to a single replacement character.
// However, there is one case when a 4 byte UTF-8 sequence will
// only generate 2 UTF-16 bytes. If we have a properly encoded
// sequence, but with an invalid value (too small or too big),
// that will result in a replacement character being written
// This replacement character is encoded as just 1 single
// UTF-16 character, which is 2 bytes.
// The below code therefore only adds 1 to mLength if the UTF8
// data will produce a decoded character which is greater than
// or equal to 0x010000 and less than 0x0110000.
// A 4byte UTF8 character is encoded as
// 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
// Bit 1-3 on the first byte, and bit 5-6 on the second byte,
// map to bit 17-21 in the final result. If these bits are
// between 0x01 and 0x11, that means that the final result is
// between 0x010000 and 0x110000. The below code reads these
// bits out and assigns them to c, but shifted up 4 bits to
// avoid having to shift twice.
// It doesn't matter what to do in the case where p + 4 > end
// since no UTF16 characters will be written in that case by
// ConvertUTF8toUTF16. Likewise it doesn't matter what we do if
// any of the surrogate bits are wrong since no UTF16
// characters will be written in that case either.
if (p + 4 <= end) {
uint32_t c = ((uint32_t)(p[0] & 0x07)) << 6 |
((uint32_t)(p[1] & 0x30));
if (c >= 0x010 && c < 0x110) {
++mLength;
}
}
p += 4;
} else if (UTF8traits::is5byte(*p)) {
p += 5;
} else if (UTF8traits::is6byte(*p)) {
p += 6;
} else { // error
++mLength; // to account for the decrement below
break;
}
}
if (p != end) {
NS_ERROR("Not a UTF-8 string. This code should only be used for converting from known UTF-8 strings.");
--mLength; // The last multi-byte char wasn't complete, discard it.
mErrorEncountered = true;
}
}
private:
size_t mLength;
bool mErrorEncountered;
};
/**
* A character sink (see |copy_string| in nsAlgorithm.h) for
* converting UTF-16 to UTF-8. Treats invalid UTF-16 data as 0xFFFD
* (0xEFBFBD in UTF-8).
*/
class ConvertUTF16toUTF8
{
public:
typedef char16_t value_type;
typedef char buffer_type;
// The error handling here is more lenient than that in
// |ConvertUTF8toUTF16|, but it's that way for backwards
// compatibility.
explicit ConvertUTF16toUTF8(buffer_type* aBuffer)
: mStart(aBuffer), mBuffer(aBuffer)
{
}
size_t Size() const
{
return mBuffer - mStart;
}
void write(const value_type* aStart, uint32_t aN)
{
buffer_type* out = mBuffer; // gcc isn't smart enough to do this!
for (const value_type* p = aStart, *end = aStart + aN; p < end; ++p) {
value_type c = *p;
if (!(c & 0xFF80)) { // U+0000 - U+007F
*out++ = (char)c;
} else if (!(c & 0xF800)) { // U+0100 - U+07FF
*out++ = 0xC0 | (char)(c >> 6);
*out++ = 0x80 | (char)(0x003F & c);
} else if (!IS_SURROGATE(c)) { // U+0800 - U+D7FF,U+E000 - U+FFFF
*out++ = 0xE0 | (char)(c >> 12);
*out++ = 0x80 | (char)(0x003F & (c >> 6));
*out++ = 0x80 | (char)(0x003F & c);
} else if (NS_IS_HIGH_SURROGATE(c)) { // U+D800 - U+DBFF
// D800- DBFF - High Surrogate
value_type h = c;
++p;
if (p == end) {
// Treat broken characters as the Unicode
// replacement character 0xFFFD (0xEFBFBD in
// UTF-8)
*out++ = '\xEF';
*out++ = '\xBF';
*out++ = '\xBD';
NS_WARNING("String ending in half a surrogate pair!");
break;
}
c = *p;
if (NS_IS_LOW_SURROGATE(c)) {
// DC00- DFFF - Low Surrogate
// N = (H - D800) *400 + 10000 + ( L - DC00 )
uint32_t ucs4 = SURROGATE_TO_UCS4(h, c);
// 0001 0000-001F FFFF
*out++ = 0xF0 | (char)(ucs4 >> 18);
*out++ = 0x80 | (char)(0x003F & (ucs4 >> 12));
*out++ = 0x80 | (char)(0x003F & (ucs4 >> 6));
*out++ = 0x80 | (char)(0x003F & ucs4);
} else {
// Treat broken characters as the Unicode
// replacement character 0xFFFD (0xEFBFBD in
// UTF-8)
*out++ = '\xEF';
*out++ = '\xBF';
*out++ = '\xBD';
// The pointer to the next character points to the second
// 16-bit value, not beyond it, as per Unicode 5.0.0
// Chapter 3 C10, only the first code unit of an illegal
// sequence must be treated as an illegally terminated
// code unit sequence (also Chapter 3 D91, "isolated [not
// paired and ill-formed] UTF-16 code units in the range
// D800..DFFF are ill-formed").
p--;
NS_WARNING("got a High Surrogate but no low surrogate");
}
} else { // U+DC00 - U+DFFF
// Treat broken characters as the Unicode replacement
// character 0xFFFD (0xEFBFBD in UTF-8)
*out++ = '\xEF';
*out++ = '\xBF';
*out++ = '\xBD';
// DC00- DFFF - Low Surrogate
NS_WARNING("got a low Surrogate but no high surrogate");
}
}
mBuffer = out;
}
void write_terminator()
{
*mBuffer = buffer_type(0);
}
private:
buffer_type* const mStart;
buffer_type* mBuffer;
};
/**
* A character sink (see |copy_string| in nsAlgorithm.h) for computing
* the number of bytes a UTF-16 would occupy in UTF-8. Treats invalid
* UTF-16 data as 0xFFFD (0xEFBFBD in UTF-8).
*/
class CalculateUTF8Size
{
public:
typedef char16_t value_type;
CalculateUTF8Size()
: mSize(0)
{
}
size_t Size() const
{
return mSize;
}
void write(const value_type* aStart, uint32_t aN)
{
// Assume UCS2 surrogate pairs won't be spread across fragments.
for (const value_type* p = aStart, *end = aStart + aN; p < end; ++p) {
value_type c = *p;
if (!(c & 0xFF80)) { // U+0000 - U+007F
mSize += 1;
} else if (!(c & 0xF800)) { // U+0100 - U+07FF
mSize += 2;
} else if (0xD800 != (0xF800 & c)) { // U+0800 - U+D7FF,U+E000 - U+FFFF
mSize += 3;
} else if (0xD800 == (0xFC00 & c)) { // U+D800 - U+DBFF
++p;
if (p == end) {
// Treat broken characters as the Unicode
// replacement character 0xFFFD (0xEFBFBD in
// UTF-8)
mSize += 3;
NS_WARNING("String ending in half a surrogate pair!");
break;
}
c = *p;
if (0xDC00 == (0xFC00 & c)) {
mSize += 4;
} else {
// Treat broken characters as the Unicode
// replacement character 0xFFFD (0xEFBFBD in
// UTF-8)
mSize += 3;
// The next code unit is the second 16-bit value, not
// the one beyond it, as per Unicode 5.0.0 Chapter 3 C10,
// only the first code unit of an illegal sequence must
// be treated as an illegally terminated code unit
// sequence (also Chapter 3 D91, "isolated [not paired and
// ill-formed] UTF-16 code units in the range D800..DFFF
// are ill-formed").
p--;
NS_WARNING("got a high Surrogate but no low surrogate");
}
} else { // U+DC00 - U+DFFF
// Treat broken characters as the Unicode replacement
// character 0xFFFD (0xEFBFBD in UTF-8)
mSize += 3;
NS_WARNING("got a low Surrogate but no high surrogate");
}
}
}
private:
size_t mSize;
};
#ifdef MOZILLA_INTERNAL_API
/**
* A character sink that performs a |reinterpret_cast|-style conversion
* from char to char16_t.
*/
class LossyConvertEncoding8to16
{
public:
typedef char value_type;
typedef char input_type;
typedef char16_t output_type;
public:
explicit LossyConvertEncoding8to16(char16_t* aDestination) :
mDestination(aDestination)
{
}
void
write(const char* aSource, uint32_t aSourceLength)
{
#ifdef MOZILLA_MAY_SUPPORT_SSE2
if (mozilla::supports_sse2()) {
write_sse2(aSource, aSourceLength);
return;
}
#endif
const char* done_writing = aSource + aSourceLength;
while (aSource < done_writing) {
*mDestination++ = (char16_t)(unsigned char)(*aSource++);
}
}
void
write_sse2(const char* aSource, uint32_t aSourceLength);
void
write_terminator()
{
*mDestination = (char16_t)(0);
}
private:
char16_t* mDestination;
};
/**
* A character sink that performs a |reinterpret_cast|-style conversion
* from char16_t to char.
*/
class LossyConvertEncoding16to8
{
public:
typedef char16_t value_type;
typedef char16_t input_type;
typedef char output_type;
explicit LossyConvertEncoding16to8(char* aDestination)
: mDestination(aDestination)
{
}
void
write(const char16_t* aSource, uint32_t aSourceLength)
{
#ifdef MOZILLA_MAY_SUPPORT_SSE2
if (mozilla::supports_sse2()) {
write_sse2(aSource, aSourceLength);
return;
}
#endif
const char16_t* done_writing = aSource + aSourceLength;
while (aSource < done_writing) {
*mDestination++ = (char)(*aSource++);
}
}
#ifdef MOZILLA_MAY_SUPPORT_SSE2
void
write_sse2(const char16_t* aSource, uint32_t aSourceLength);
#endif
void
write_terminator()
{
*mDestination = '\0';
}
private:
char* mDestination;
};
#endif // MOZILLA_INTERNAL_API
#endif /* !defined(nsUTF8Utils_h_) */
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