字符串编码转换
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字符串编码转换
字符串编码转换涉及宽字节表示法与UTF-8表示法之间的转换、宽字节表示法与UTF-16表示法之间的转换、UTF-8表示法与UTF-16表示法之间的转换、UTF-16表示法于ASCII表示法之间的转换、ASCII表示法宽字节表示法之间的转换。
相关文件
- base/strings/utf\\_string\\_conversions.h // 字符串编码转换定义
- base/strings/utf\\_string\\_conversions.cc // 字符串编码转换实现
- base/strings/utf\\_string\\_conversions\\_fuzzer.cc // 字符串编码转换实现
方法定义
// base/strings/utf_string_conversions.h
namespace base {
// These convert between UTF-8, -16, and -32 strings. They are potentially slow,
// so avoid unnecessary conversions. The low-level versions return a boolean
// indicating whether the conversion was 100% valid. In this case, it will still
// do the best it can and put the result in the output buffer. The versions that
// return strings ignore this error and just return the best conversion
// possible.
BASE_EXPORT bool WideToUTF8(const wchar_t* src, size_t src_len,
std::string* output);
BASE_EXPORT std::string WideToUTF8(WStringPiece wide) WARN_UNUSED_RESULT;
BASE_EXPORT bool UTF8ToWide(const char* src, size_t src_len,
std::wstring* output);
BASE_EXPORT std::wstring UTF8ToWide(StringPiece utf8) WARN_UNUSED_RESULT;
BASE_EXPORT bool WideToUTF16(const wchar_t* src,
size_t src_len,
std::u16string* output);
BASE_EXPORT std::u16string WideToUTF16(WStringPiece wide) WARN_UNUSED_RESULT;
BASE_EXPORT bool UTF16ToWide(const char16_t* src,
size_t src_len,
std::wstring* output);
BASE_EXPORT std::wstring UTF16ToWide(StringPiece16 utf16) WARN_UNUSED_RESULT;
BASE_EXPORT bool UTF8ToUTF16(const char* src,
size_t src_len,
std::u16string* output);
BASE_EXPORT std::u16string UTF8ToUTF16(StringPiece utf8) WARN_UNUSED_RESULT;
BASE_EXPORT bool UTF16ToUTF8(const char16_t* src,
size_t src_len,
std::string* output);
BASE_EXPORT std::string UTF16ToUTF8(StringPiece16 utf16) WARN_UNUSED_RESULT;
// This converts an ASCII string, typically a hardcoded constant, to a UTF16
// string.
BASE_EXPORT std::u16string ASCIIToUTF16(StringPiece ascii) WARN_UNUSED_RESULT;
// Converts to 7-bit ASCII by truncating. The result must be known to be ASCII
// beforehand.
BASE_EXPORT std::string UTF16ToASCII(StringPiece16 utf16) WARN_UNUSED_RESULT;
#if defined(WCHAR_T_IS_UTF16)
// This converts an ASCII string, typically a hardcoded constant, to a wide
// string.
BASE_EXPORT std::wstring ASCIIToWide(StringPiece ascii) WARN_UNUSED_RESULT;
// Converts to 7-bit ASCII by truncating. The result must be known to be ASCII
// beforehand.
BASE_EXPORT std::string WideToASCII(WStringPiece wide) WARN_UNUSED_RESULT;
#endif // defined(WCHAR_T_IS_UTF16)
// The conversion functions in this file should not be used to convert string
// literals. Instead, the corresponding prefixes (e.g. u"" for UTF16 or L"" for
// Wide) should be used. Deleting the overloads here catches these cases at
// compile time.
template <size_t N>
std::u16string WideToUTF16(const wchar_t (&str)[N]) {
static_assert(N == 0, "Error: Use the u\\"...\\" prefix instead.");
return std::u16string();
}
// TODO(crbug.com/1189439): Also disallow passing string constants in tests.
#if !defined(UNIT_TEST)
template <size_t N>
std::u16string ASCIIToUTF16(const char (&str)[N]) {
static_assert(N == 0, "Error: Use the u\\"...\\" prefix instead.");
return std::u16string();
}
// Mutable character arrays are usually only populated during runtime. Continue
// to allow this conversion.
template <size_t N>
std::u16string ASCIIToUTF16(char (&str)[N]) {
return ASCIIToUTF16(StringPiece(str));
}
#endif
} // namespace base方法实现
// base/strings/utf_string_conversions.cc
namespace base {
namespace {
constexpr int32_t kErrorCodePoint = 0xFFFD;
// Size coefficient ----------------------------------------------------------
// The maximum number of codeunits in the destination encoding corresponding to
// one codeunit in the source encoding.
template <typename SrcChar, typename DestChar>
struct SizeCoefficient {
static_assert(sizeof(SrcChar) < sizeof(DestChar),
"Default case: from a smaller encoding to the bigger one");
// ASCII symbols are encoded by one codeunit in all encodings.
static constexpr int value = 1;
};
template <>
struct SizeCoefficient<char16_t, char> {
// One UTF-16 codeunit corresponds to at most 3 codeunits in UTF-8.
static constexpr int value = 3;
};
#if defined(WCHAR_T_IS_UTF32)
template <>
struct SizeCoefficient<wchar_t, char> {
// UTF-8 uses at most 4 codeunits per character.
static constexpr int value = 4;
};
template <>
struct SizeCoefficient<wchar_t, char16_t> {
// UTF-16 uses at most 2 codeunits per character.
static constexpr int value = 2;
};
#endif // defined(WCHAR_T_IS_UTF32)
template <typename SrcChar, typename DestChar>
constexpr int size_coefficient_v =
SizeCoefficient<std::decay_t<SrcChar>, std::decay_t<DestChar>>::value;
// UnicodeAppendUnsafe --------------------------------------------------------
// Function overloads that write code_point to the output string. Output string
// has to have enough space for the codepoint.
// Convenience typedef that checks whether the passed in type is integral (i.e.
// bool, char, int or their extended versions) and is of the correct size.
template <typename Char, size_t N>
using EnableIfBitsAre = std::enable_if_t<std::is_integral<Char>::value &&
CHAR_BIT * sizeof(Char) == N,
bool>;
template <typename Char, EnableIfBitsAre<Char, 8> = true>
void UnicodeAppendUnsafe(Char* out, int32_t* size, uint32_t code_point) {
CBU8_APPEND_UNSAFE(out, *size, code_point);
}
template <typename Char, EnableIfBitsAre<Char, 16> = true>
void UnicodeAppendUnsafe(Char* out, int32_t* size, uint32_t code_point) {
CBU16_APPEND_UNSAFE(out, *size, code_point);
}
template <typename Char, EnableIfBitsAre<Char, 32> = true>
void UnicodeAppendUnsafe(Char* out, int32_t* size, uint32_t code_point) {
out[(*size)++] = code_point;
}
// DoUTFConversion ------------------------------------------------------------
// Main driver of UTFConversion specialized for different Src encodings.
// dest has to have enough room for the converted text.
template <typename DestChar>
bool DoUTFConversion(const char* src,
int32_t src_len,
DestChar* dest,
int32_t* dest_len) {
bool success = true;
for (int32_t i = 0; i < src_len;) {
int32_t code_point;
CBU8_NEXT(src, i, src_len, code_point);
if (!IsValidCodepoint(code_point)) {
success = false;
code_point = kErrorCodePoint;
}
UnicodeAppendUnsafe(dest, dest_len, code_point);
}
return success;
}
template <typename DestChar>
bool DoUTFConversion(const char16_t* src,
int32_t src_len,
DestChar* dest,
int32_t* dest_len) {
bool success = true;
auto ConvertSingleChar = [&success](char16_t in) -> int32_t {
if (!CBU16_IS_SINGLE(in) || !IsValidCodepoint(in)) {
success = false;
return kErrorCodePoint;
}
return in;
};
int32_t i = 0;
// Always have another symbol in order to avoid checking boundaries in the
// middle of the surrogate pair.
while (i < src_len - 1) {
int32_t code_point;
if (CBU16_IS_LEAD(src[i]) && CBU16_IS_TRAIL(src[i + 1])) {
code_point = CBU16_GET_SUPPLEMENTARY(src[i], src[i + 1]);
if (!IsValidCodepoint(code_point)) {
code_point = kErrorCodePoint;
success = false;
}
i += 2;
} else {
code_point = ConvertSingleChar(src[i]);
++i;
}
UnicodeAppendUnsafe(dest, dest_len, code_point);
}
if (i < src_len)
UnicodeAppendUnsafe(dest, dest_len, ConvertSingleChar(src[i]));
return success;
}
#if defined(WCHAR_T_IS_UTF32)
template <typename DestChar>
bool DoUTFConversion(const wchar_t* src,
int32_t src_len,
DestChar* dest,
int32_t* dest_len) {
bool success = true;
for (int32_t i = 0; i < src_len; ++i) {
int32_t code_point = src[i];
if (!IsValidCodepoint(code_point)) {
success = false;
code_point = kErrorCodePoint;
}
UnicodeAppendUnsafe(dest, dest_len, code_point);
}
return success;
}
#endif // defined(WCHAR_T_IS_UTF32)
// UTFConversion --------------------------------------------------------------
// Function template for generating all UTF conversions.
template <typename InputString, typename DestString>
bool UTFConversion(const InputString& src_str, DestString* dest_str) {
if (IsStringASCII(src_str)) {
dest_str->assign(src_str.begin(), src_str.end());
return true;
}
dest_str->resize(src_str.length() *
size_coefficient_v<typename InputString::value_type,
typename DestString::value_type>);
// Empty string is ASCII => it OK to call operator[].
auto* dest = &(*dest_str)[0];
// ICU requires 32 bit numbers.
int32_t src_len32 = static_cast<int32_t>(src_str.length());
int32_t dest_len32 = 0;
bool res = DoUTFConversion(src_str.data(), src_len32, dest, &dest_len32);
dest_str->resize(dest_len32);
dest_str->shrink_to_fit();
return res;
}
} // namespace
// UTF16 <-> UTF8 --------------------------------------------------------------
bool UTF8ToUTF16(const char* src, size_t src_len, std::u16string* output) {
return UTFConversion(StringPiece(src, src_len), output);
}
std::u16string UTF8ToUTF16(StringPiece utf8) {
std::u16string ret;
// Ignore the success flag of this call, it will do the best it can for
// invalid input, which is what we want here.
UTF8ToUTF16(utf8.data(), utf8.size(), &ret);
return ret;
}
bool UTF16ToUTF8(const char16_t* src, size_t src_len, std::string* output) {
return UTFConversion(StringPiece16(src, src_len), output);
}
std::string UTF16ToUTF8(StringPiece16 utf16) {
std::string ret;
// Ignore the success flag of this call, it will do the best it can for
// invalid input, which is what we want here.
UTF16ToUTF8(utf16.data(), utf16.length(), &ret);
return ret;
}
// UTF-16 <-> Wide -------------------------------------------------------------
#if defined(WCHAR_T_IS_UTF16)
// When wide == UTF-16 the conversions are a NOP.
bool WideToUTF16(const wchar_t* src, size_t src_len, std::u16string* output) {
output->assign(src, src + src_len);
return true;
}
std::u16string WideToUTF16(WStringPiece wide) {
return std::u16string(wide.begin(), wide.end());
}
bool UTF16ToWide(const char16_t* src, size_t src_len, std::wstring* output) {
output->assign(src, src + src_len);
return true;
}
std::wstring UTF16ToWide(StringPiece16 utf16) {
return std::wstring(utf16.begin(), utf16.end());
}
#elif defined(WCHAR_T_IS_UTF32)
bool WideToUTF16(const wchar_t* src, size_t src_len, std::u16string* output) {
return UTFConversion(base::WStringPiece(src, src_len), output);
}
std::u16string WideToUTF16(WStringPiece wide) {
std::u16string ret;
// Ignore the success flag of this call, it will do the best it can for
// invalid input, which is what we want here.
WideToUTF16(wide.data(), wide.length(), &ret);
return ret;
}
bool UTF16ToWide(const char16_t* src, size_t src_len, std::wstring* output) {
return UTFConversion(StringPiece16(src, src_len), output);
}
std::wstring UTF16ToWide(StringPiece16 utf16) {
std::wstring ret;
// Ignore the success flag of this call, it will do the best it can for
// invalid input, which is what we want here.
UTF16ToWide(utf16.data(), utf16.length(), &ret);
return ret;
}
#endif // defined(WCHAR_T_IS_UTF32)
// UTF-8 <-> Wide --------------------------------------------------------------
// UTF8ToWide is the same code, regardless of whether wide is 16 or 32 bits
bool UTF8ToWide(const char* src, size_t src_len, std::wstring* output) {
return UTFConversion(StringPiece(src, src_len), output);
}
std::wstring UTF8ToWide(StringPiece utf8) {
std::wstring ret;
// Ignore the success flag of this call, it will do the best it can for
// invalid input, which is what we want here.
UTF8ToWide(utf8.data(), utf8.length(), &ret);
return ret;
}
#if defined(WCHAR_T_IS_UTF16)
// Easy case since we can use the "utf" versions we already wrote above.
bool WideToUTF8(const wchar_t* src, size_t src_len, std::string* output) {
return UTF16ToUTF8(as_u16cstr(src), src_len, output);
}
std::string WideToUTF8(WStringPiece wide) {
return UTF16ToUTF8(StringPiece16(as_u16cstr(wide), wide.size()));
}
#elif defined(WCHAR_T_IS_UTF32)
bool WideToUTF8(const wchar_t* src, size_t src_len, std::string* output) {
return UTFConversion(WStringPiece(src, src_len), output);
}
std::string WideToUTF8(WStringPiece wide) {
std::string ret;
// Ignore the success flag of this call, it will do the best it can for
// invalid input, which is what we want here.
WideToUTF8(wide.data(), wide.length(), &ret);
return ret;
}
#endif // defined(WCHAR_T_IS_UTF32)
std::u16string ASCIIToUTF16(StringPiece ascii) {
DCHECK(IsStringASCII(ascii)) << ascii;
return std::u16string(ascii.begin(), ascii.end());
}
std::string UTF16ToASCII(StringPiece16 utf16) {
DCHECK(IsStringASCII(utf16)) << UTF16ToUTF8(utf16);
return std::string(utf16.begin(), utf16.end());
}
#if defined(WCHAR_T_IS_UTF16)
std::wstring ASCIIToWide(StringPiece ascii) {
DCHECK(IsStringASCII(ascii)) << ascii;
return std::wstring(ascii.begin(), ascii.end());
}
std::string WideToASCII(WStringPiece wide) {
DCHECK(IsStringASCII(wide)) << wide;
return std::string(wide.begin(), wide.end());
}
#endif // defined(WCHAR_T_IS_UTF16)
} // namespace basefuzzer
// Entry point for LibFuzzer.
extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
base::StringPiece string_piece_input(reinterpret_cast<const char*>(data),
size);
ignore_result(base::UTF8ToWide(string_piece_input));
base::UTF8ToWide(reinterpret_cast<const char*>(data), size,
&output_std_wstring);
ignore_result(base::UTF8ToUTF16(string_piece_input));
base::UTF8ToUTF16(reinterpret_cast<const char*>(data), size,
&output_string16);
// Test for char16_t.
if (size % 2 == 0) {
base::StringPiece16 string_piece_input16(
reinterpret_cast<const char16_t*>(data), size / 2);
ignore_result(base::UTF16ToWide(output_string16));
base::UTF16ToWide(reinterpret_cast<const char16_t*>(data), size / 2,
&output_std_wstring);
ignore_result(base::UTF16ToUTF8(string_piece_input16));
base::UTF16ToUTF8(reinterpret_cast<const char16_t*>(data), size / 2,
&output_std_string);
}
// Test for wchar_t.
size_t wchar_t_size = sizeof(wchar_t);
if (size % wchar_t_size == 0) {
ignore_result(base::WideToUTF8(output_std_wstring));
base::WideToUTF8(reinterpret_cast<const wchar_t*>(data),
size / wchar_t_size, &output_std_string);
ignore_result(base::WideToUTF16(output_std_wstring));
base::WideToUTF16(reinterpret_cast<const wchar_t*>(data),
size / wchar_t_size, &output_string16);
}
// Test for ASCII. This condition is needed to avoid hitting instant CHECK
// failures.
if (base::IsStringASCII(string_piece_input)) {
output_string16 = base::ASCIIToUTF16(string_piece_input);
base::StringPiece16 string_piece_input16(output_string16);
ignore_result(base::UTF16ToASCII(string_piece_input16));
}
return 0;
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