Unicode对象和编码解码器
***********************


Unicode对象
===========

自从python3.3中实现了:pep:*393* 以来，Unicode对象在内部使用各种表示形
式，以便在保持内存效率的同时处理完整范围的Unicode字符。对于所有代码点
都低于128、256或65536的字符串，有一些特殊情况；否则，代码点必须低于
1114112（这是完整的Unicode范围）。

"Py_UNICODE*" and UTF-8 representations are created on demand and
cached in the Unicode object.  The "Py_UNICODE*" representation is
deprecated and inefficient.

Due to the transition between the old APIs and the new APIs, Unicode
objects can internally be in two states depending on how they were
created:

* "canonical" Unicode objects are all objects created by a non-
  deprecated Unicode API.  They use the most efficient representation
  allowed by the implementation.

* "legacy" Unicode objects have been created through one of the
  deprecated APIs (typically "PyUnicode_FromUnicode()") and only bear
  the "Py_UNICODE*" representation; you will have to call
  "PyUnicode_READY()" on them before calling any other API.

注解:

  The "legacy" Unicode object will be removed in Python 3.12 with
  deprecated APIs. All Unicode objects will be "canonical" since then.
  See **PEP 623** for more information.


Unicode类型
-----------

These are the basic Unicode object types used for the Unicode
implementation in Python:

Py_UCS4
Py_UCS2
Py_UCS1

   These types are typedefs for unsigned integer types wide enough to
   contain characters of 32 bits, 16 bits and 8 bits, respectively.
   When dealing with single Unicode characters, use "Py_UCS4".

   3.3 新版功能.

Py_UNICODE

   This is a typedef of "wchar_t", which is a 16-bit type or 32-bit
   type depending on the platform.

   在 3.3 版更改: In previous versions, this was a 16-bit type or a
   32-bit type depending on whether you selected a "narrow" or "wide"
   Unicode version of Python at build time.

PyASCIIObject
PyCompactUnicodeObject
PyUnicodeObject

   These subtypes of "PyObject" represent a Python Unicode object.  In
   almost all cases, they shouldn't be used directly, since all API
   functions that deal with Unicode objects take and return "PyObject"
   pointers.

   3.3 新版功能.

PyTypeObject PyUnicode_Type

   This instance of "PyTypeObject" represents the Python Unicode type.
   It is exposed to Python code as "str".

The following APIs are really C macros and can be used to do fast
checks and to access internal read-only data of Unicode objects:

int PyUnicode_Check(PyObject *o)

   Return true if the object *o* is a Unicode object or an instance of
   a Unicode subtype.

int PyUnicode_CheckExact(PyObject *o)

   Return true if the object *o* is a Unicode object, but not an
   instance of a subtype.

int PyUnicode_READY(PyObject *o)

   Ensure the string object *o* is in the "canonical" representation.
   This is required before using any of the access macros described
   below.

   Returns "0" on success and "-1" with an exception set on failure,
   which in particular happens if memory allocation fails.

   3.3 新版功能.

   Deprecated since version 3.10, will be removed in version 3.12:
   This API will be removed with "PyUnicode_FromUnicode()".

Py_ssize_t PyUnicode_GET_LENGTH(PyObject *o)

   Return the length of the Unicode string, in code points.  *o* has
   to be a Unicode object in the "canonical" representation (not
   checked).

   3.3 新版功能.

Py_UCS1* PyUnicode_1BYTE_DATA(PyObject *o)
Py_UCS2* PyUnicode_2BYTE_DATA(PyObject *o)
Py_UCS4* PyUnicode_4BYTE_DATA(PyObject *o)

   Return a pointer to the canonical representation cast to UCS1, UCS2
   or UCS4 integer types for direct character access.  No checks are
   performed if the canonical representation has the correct character
   size; use "PyUnicode_KIND()" to select the right macro.  Make sure
   "PyUnicode_READY()" has been called before accessing this.

   3.3 新版功能.

PyUnicode_WCHAR_KIND
PyUnicode_1BYTE_KIND
PyUnicode_2BYTE_KIND
PyUnicode_4BYTE_KIND

   Return values of the "PyUnicode_KIND()" macro.

   3.3 新版功能.

   Deprecated since version 3.10, will be removed in version 3.12:
   "PyUnicode_WCHAR_KIND" is deprecated.

int PyUnicode_KIND(PyObject *o)

   Return one of the PyUnicode kind constants (see above) that
   indicate how many bytes per character this Unicode object uses to
   store its data.  *o* has to be a Unicode object in the "canonical"
   representation (not checked).

   3.3 新版功能.

void* PyUnicode_DATA(PyObject *o)

   Return a void pointer to the raw Unicode buffer.  *o* has to be a
   Unicode object in the "canonical" representation (not checked).

   3.3 新版功能.

void PyUnicode_WRITE(int kind, void *data, Py_ssize_t index, Py_UCS4 value)

   Write into a canonical representation *data* (as obtained with
   "PyUnicode_DATA()").  This macro does not do any sanity checks and
   is intended for usage in loops.  The caller should cache the *kind*
   value and *data* pointer as obtained from other macro calls.
   *index* is the index in the string (starts at 0) and *value* is the
   new code point value which should be written to that location.

   3.3 新版功能.

Py_UCS4 PyUnicode_READ(int kind, void *data, Py_ssize_t index)

   Read a code point from a canonical representation *data* (as
   obtained with "PyUnicode_DATA()").  No checks or ready calls are
   performed.

   3.3 新版功能.

Py_UCS4 PyUnicode_READ_CHAR(PyObject *o, Py_ssize_t index)

   Read a character from a Unicode object *o*, which must be in the
   "canonical" representation.  This is less efficient than
   "PyUnicode_READ()" if you do multiple consecutive reads.

   3.3 新版功能.

PyUnicode_MAX_CHAR_VALUE(o)

   Return the maximum code point that is suitable for creating another
   string based on *o*, which must be in the "canonical"
   representation.  This is always an approximation but more efficient
   than iterating over the string.

   3.3 新版功能.

int PyUnicode_ClearFreeList()

   清空释放列表。 返回所释放的条目数。

Py_ssize_t PyUnicode_GET_SIZE(PyObject *o)

   Return the size of the deprecated "Py_UNICODE" representation, in
   code units (this includes surrogate pairs as 2 units).  *o* has to
   be a Unicode object (not checked).

   Deprecated since version 3.3, will be removed in version 3.12: Part
   of the old-style Unicode API, please migrate to using
   "PyUnicode_GET_LENGTH()".

Py_ssize_t PyUnicode_GET_DATA_SIZE(PyObject *o)

   Return the size of the deprecated "Py_UNICODE" representation in
   bytes.  *o* has to be a Unicode object (not checked).

   Deprecated since version 3.3, will be removed in version 3.12: Part
   of the old-style Unicode API, please migrate to using
   "PyUnicode_GET_LENGTH()".

Py_UNICODE* PyUnicode_AS_UNICODE(PyObject *o)
const char* PyUnicode_AS_DATA(PyObject *o)

   Return a pointer to a "Py_UNICODE" representation of the object.
   The returned buffer is always terminated with an extra null code
   point.  It may also contain embedded null code points, which would
   cause the string to be truncated when used in most C functions.
   The "AS_DATA" form casts the pointer to "const char *".  The *o*
   argument has to be a Unicode object (not checked).

   在 3.3 版更改: This macro is now inefficient -- because in many
   cases the "Py_UNICODE" representation does not exist and needs to
   be created -- and can fail (return "NULL" with an exception set).
   Try to port the code to use the new "PyUnicode_nBYTE_DATA()" macros
   or use "PyUnicode_WRITE()" or "PyUnicode_READ()".

   Deprecated since version 3.3, will be removed in version 3.12: Part
   of the old-style Unicode API, please migrate to using the
   "PyUnicode_nBYTE_DATA()" family of macros.


Unicode字符属性
---------------

Unicode provides many different character properties. The most often
needed ones are available through these macros which are mapped to C
functions depending on the Python configuration.

int Py_UNICODE_ISSPACE(Py_UNICODE ch)

   Return "1" or "0" depending on whether *ch* is a whitespace
   character.

int Py_UNICODE_ISLOWER(Py_UNICODE ch)

   Return "1" or "0" depending on whether *ch* is a lowercase
   character.

int Py_UNICODE_ISUPPER(Py_UNICODE ch)

   Return "1" or "0" depending on whether *ch* is an uppercase
   character.

int Py_UNICODE_ISTITLE(Py_UNICODE ch)

   Return "1" or "0" depending on whether *ch* is a titlecase
   character.

int Py_UNICODE_ISLINEBREAK(Py_UNICODE ch)

   Return "1" or "0" depending on whether *ch* is a linebreak
   character.

int Py_UNICODE_ISDECIMAL(Py_UNICODE ch)

   Return "1" or "0" depending on whether *ch* is a decimal character.

int Py_UNICODE_ISDIGIT(Py_UNICODE ch)

   Return "1" or "0" depending on whether *ch* is a digit character.

int Py_UNICODE_ISNUMERIC(Py_UNICODE ch)

   Return "1" or "0" depending on whether *ch* is a numeric character.

int Py_UNICODE_ISALPHA(Py_UNICODE ch)

   Return "1" or "0" depending on whether *ch* is an alphabetic
   character.

int Py_UNICODE_ISALNUM(Py_UNICODE ch)

   Return "1" or "0" depending on whether *ch* is an alphanumeric
   character.

int Py_UNICODE_ISPRINTABLE(Py_UNICODE ch)

   Return "1" or "0" depending on whether *ch* is a printable
   character. Nonprintable characters are those characters defined in
   the Unicode character database as "Other" or "Separator", excepting
   the ASCII space (0x20) which is considered printable.  (Note that
   printable characters in this context are those which should not be
   escaped when "repr()" is invoked on a string. It has no bearing on
   the handling of strings written to "sys.stdout" or "sys.stderr".)

These APIs can be used for fast direct character conversions:

Py_UNICODE Py_UNICODE_TOLOWER(Py_UNICODE ch)

   Return the character *ch* converted to lower case.

   3.3 版后已移除: This function uses simple case mappings.

Py_UNICODE Py_UNICODE_TOUPPER(Py_UNICODE ch)

   Return the character *ch* converted to upper case.

   3.3 版后已移除: This function uses simple case mappings.

Py_UNICODE Py_UNICODE_TOTITLE(Py_UNICODE ch)

   Return the character *ch* converted to title case.

   3.3 版后已移除: This function uses simple case mappings.

int Py_UNICODE_TODECIMAL(Py_UNICODE ch)

   Return the character *ch* converted to a decimal positive integer.
   Return "-1" if this is not possible.  This macro does not raise
   exceptions.

int Py_UNICODE_TODIGIT(Py_UNICODE ch)

   Return the character *ch* converted to a single digit integer.
   Return "-1" if this is not possible.  This macro does not raise
   exceptions.

double Py_UNICODE_TONUMERIC(Py_UNICODE ch)

   Return the character *ch* converted to a double. Return "-1.0" if
   this is not possible.  This macro does not raise exceptions.

These APIs can be used to work with surrogates:

Py_UNICODE_IS_SURROGATE(ch)

   Check if *ch* is a surrogate ("0xD800 <= ch <= 0xDFFF").

Py_UNICODE_IS_HIGH_SURROGATE(ch)

   Check if *ch* is a high surrogate ("0xD800 <= ch <= 0xDBFF").

Py_UNICODE_IS_LOW_SURROGATE(ch)

   Check if *ch* is a low surrogate ("0xDC00 <= ch <= 0xDFFF").

Py_UNICODE_JOIN_SURROGATES(high, low)

   Join two surrogate characters and return a single Py_UCS4 value.
   *high* and *low* are respectively the leading and trailing
   surrogates in a surrogate pair.


Creating and accessing Unicode strings
--------------------------------------

To create Unicode objects and access their basic sequence properties,
use these APIs:

PyObject* PyUnicode_New(Py_ssize_t size, Py_UCS4 maxchar)
    *Return value: New reference.*

   Create a new Unicode object.  *maxchar* should be the true maximum
   code point to be placed in the string.  As an approximation, it can
   be rounded up to the nearest value in the sequence 127, 255, 65535,
   1114111.

   This is the recommended way to allocate a new Unicode object.
   Objects created using this function are not resizable.

   3.3 新版功能.

PyObject* PyUnicode_FromKindAndData(int kind, const void *buffer, Py_ssize_t size)
    *Return value: New reference.*

   Create a new Unicode object with the given *kind* (possible values
   are "PyUnicode_1BYTE_KIND" etc., as returned by
   "PyUnicode_KIND()").  The *buffer* must point to an array of *size*
   units of 1, 2 or 4 bytes per character, as given by the kind.

   3.3 新版功能.

PyObject* PyUnicode_FromStringAndSize(const char *u, Py_ssize_t size)
    *Return value: New reference.*

   Create a Unicode object from the char buffer *u*.  The bytes will
   be interpreted as being UTF-8 encoded.  The buffer is copied into
   the new object. If the buffer is not "NULL", the return value might
   be a shared object, i.e. modification of the data is not allowed.

   If *u* is "NULL", this function behaves like
   "PyUnicode_FromUnicode()" with the buffer set to "NULL".  This
   usage is deprecated in favor of "PyUnicode_New()", and will be
   removed in Python 3.12.

PyObject *PyUnicode_FromString(const char *u)
    *Return value: New reference.*

   Create a Unicode object from a UTF-8 encoded null-terminated char
   buffer *u*.

PyObject* PyUnicode_FromFormat(const char *format, ...)
    *Return value: New reference.*

   Take a C "printf()"-style *format* string and a variable number of
   arguments, calculate the size of the resulting Python Unicode
   string and return a string with the values formatted into it.  The
   variable arguments must be C types and must correspond exactly to
   the format characters in the *format* ASCII-encoded string. The
   following format characters are allowed:

   +---------------------+-----------------------+------------------------------------+
   | 格式字符            | 类型                  | 注释                               |
   |=====================|=======================|====================================|
   | "%%"                | *不适用*              | 文字%字符。                        |
   +---------------------+-----------------------+------------------------------------+
   | "%c"                | int                   | 单个字符，表示为C 语言的整型。     |
   +---------------------+-----------------------+------------------------------------+
   | "%d"                | int                   | 相当于 "printf("%d")". [1]         |
   +---------------------+-----------------------+------------------------------------+
   | "%u"                | unsigned int          | 相当于 "printf("%u")". [1]         |
   +---------------------+-----------------------+------------------------------------+
   | "%ld"               | 长整型                | 相当于 "printf("%ld")". [1]        |
   +---------------------+-----------------------+------------------------------------+
   | "%li"               | 长整型                | 相当于 "printf("%li")". [1]        |
   +---------------------+-----------------------+------------------------------------+
   | "%lu"               | unsigned long         | 相当于 "printf("%lu")". [1]        |
   +---------------------+-----------------------+------------------------------------+
   | "%lld"              | long long             | 相当于 "printf("%lld")". [1]       |
   +---------------------+-----------------------+------------------------------------+
   | "%lli"              | long long             | 相当于 "printf("%lli")". [1]       |
   +---------------------+-----------------------+------------------------------------+
   | "%llu"              | unsigned long long    | 相当于 "printf("%llu")". [1]       |
   +---------------------+-----------------------+------------------------------------+
   | "%zd"               | Py_ssize_t            | 相当于 "printf("%zd")". [1]        |
   +---------------------+-----------------------+------------------------------------+
   | "%zi"               | Py_ssize_t            | 相当于 "printf("%zi")". [1]        |
   +---------------------+-----------------------+------------------------------------+
   | "%zu"               | size_t                | 相当于 "printf("%zu")". [1]        |
   +---------------------+-----------------------+------------------------------------+
   | "%i"                | int                   | 相当于 "printf("%i")". [1]         |
   +---------------------+-----------------------+------------------------------------+
   | "%x"                | int                   | 相当于 "printf("%x")". [1]         |
   +---------------------+-----------------------+------------------------------------+
   | "%s"                | const char*           | 以 null 为终止符的 C 字符数组。    |
   +---------------------+-----------------------+------------------------------------+
   | "%p"                | const void*           | 一个 C 指针的十六进制表示形式。 基 |
   |                     |                       | 本等价于 "printf("%p")" 但它会确   |
   |                     |                       | 保以字面值 "0x" 开头，不论系统平台 |
   |                     |                       | 上 "printf" 的输出是什么。         |
   +---------------------+-----------------------+------------------------------------+
   | "%A"                | PyObject*             | "ascii()" 调用的结果。             |
   +---------------------+-----------------------+------------------------------------+
   | "%U"                | PyObject*             | A Unicode object.                  |
   +---------------------+-----------------------+------------------------------------+
   | "%V"                | PyObject*, const      | A Unicode object (which may be     |
   |                     | char*                 | "NULL") and a null-terminated C    |
   |                     |                       | character array as a second        |
   |                     |                       | parameter (which will be used, if  |
   |                     |                       | the first parameter is "NULL").    |
   +---------------------+-----------------------+------------------------------------+
   | "%S"                | PyObject*             | The result of calling              |
   |                     |                       | "PyObject_Str()".                  |
   +---------------------+-----------------------+------------------------------------+
   | "%R"                | PyObject*             | The result of calling              |
   |                     |                       | "PyObject_Repr()".                 |
   +---------------------+-----------------------+------------------------------------+

   An unrecognized format character causes all the rest of the format
   string to be copied as-is to the result string, and any extra
   arguments discarded.

   注解:

     The width formatter unit is number of characters rather than
     bytes. The precision formatter unit is number of bytes for ""%s""
     and ""%V"" (if the "PyObject*" argument is "NULL"), and a number
     of characters for ""%A"", ""%U"", ""%S"", ""%R"" and ""%V"" (if
     the "PyObject*" argument is not "NULL").

   [1] For integer specifiers (d, u, ld, li, lu, lld, lli, llu, zd,
       zi, zu, i, x): the 0-conversion flag has effect even when a
       precision is given.

   在 3.2 版更改: Support for ""%lld"" and ""%llu"" added.

   在 3.3 版更改: Support for ""%li"", ""%lli"" and ""%zi"" added.

   在 3.4 版更改: Support width and precision formatter for ""%s"",
   ""%A"", ""%U"", ""%V"", ""%S"", ""%R"" added.

PyObject* PyUnicode_FromFormatV(const char *format, va_list vargs)
    *Return value: New reference.*

   Identical to "PyUnicode_FromFormat()" except that it takes exactly
   two arguments.

PyObject* PyUnicode_FromEncodedObject(PyObject *obj, const char *encoding, const char *errors)
    *Return value: New reference.*

   Decode an encoded object *obj* to a Unicode object.

   "bytes", "bytearray" and other *bytes-like objects* are decoded
   according to the given *encoding* and using the error handling
   defined by *errors*. Both can be "NULL" to have the interface use
   the default values (see Built-in Codecs for details).

   All other objects, including Unicode objects, cause a "TypeError"
   to be set.

   The API returns "NULL" if there was an error.  The caller is
   responsible for decref'ing the returned objects.

Py_ssize_t PyUnicode_GetLength(PyObject *unicode)

   Return the length of the Unicode object, in code points.

   3.3 新版功能.

Py_ssize_t PyUnicode_CopyCharacters(PyObject *to, Py_ssize_t to_start, PyObject *from, Py_ssize_t from_start, Py_ssize_t how_many)

   Copy characters from one Unicode object into another.  This
   function performs character conversion when necessary and falls
   back to "memcpy()" if possible.  Returns "-1" and sets an exception
   on error, otherwise returns the number of copied characters.

   3.3 新版功能.

Py_ssize_t PyUnicode_Fill(PyObject *unicode, Py_ssize_t start, Py_ssize_t length, Py_UCS4 fill_char)

   Fill a string with a character: write *fill_char* into
   "unicode[start:start+length]".

   Fail if *fill_char* is bigger than the string maximum character, or
   if the string has more than 1 reference.

   Return the number of written character, or return "-1" and raise an
   exception on error.

   3.3 新版功能.

int PyUnicode_WriteChar(PyObject *unicode, Py_ssize_t index, Py_UCS4 character)

   Write a character to a string.  The string must have been created
   through "PyUnicode_New()".  Since Unicode strings are supposed to
   be immutable, the string must not be shared, or have been hashed
   yet.

   This function checks that *unicode* is a Unicode object, that the
   index is not out of bounds, and that the object can be modified
   safely (i.e. that it its reference count is one).

   3.3 新版功能.

Py_UCS4 PyUnicode_ReadChar(PyObject *unicode, Py_ssize_t index)

   Read a character from a string.  This function checks that
   *unicode* is a Unicode object and the index is not out of bounds,
   in contrast to the macro version "PyUnicode_READ_CHAR()".

   3.3 新版功能.

PyObject* PyUnicode_Substring(PyObject *str, Py_ssize_t start, Py_ssize_t end)
    *Return value: New reference.*

   Return a substring of *str*, from character index *start*
   (included) to character index *end* (excluded).  Negative indices
   are not supported.

   3.3 新版功能.

Py_UCS4* PyUnicode_AsUCS4(PyObject *u, Py_UCS4 *buffer, Py_ssize_t buflen, int copy_null)

   Copy the string *u* into a UCS4 buffer, including a null character,
   if *copy_null* is set.  Returns "NULL" and sets an exception on
   error (in particular, a "SystemError" if *buflen* is smaller than
   the length of *u*).  *buffer* is returned on success.

   3.3 新版功能.

Py_UCS4* PyUnicode_AsUCS4Copy(PyObject *u)

   Copy the string *u* into a new UCS4 buffer that is allocated using
   "PyMem_Malloc()".  If this fails, "NULL" is returned with a
   "MemoryError" set.  The returned buffer always has an extra null
   code point appended.

   3.3 新版功能.


Deprecated Py_UNICODE APIs
--------------------------

Deprecated since version 3.3, will be removed in version 3.12.

These API functions are deprecated with the implementation of **PEP
393**. Extension modules can continue using them, as they will not be
removed in Python 3.x, but need to be aware that their use can now
cause performance and memory hits.

PyObject* PyUnicode_FromUnicode(const Py_UNICODE *u, Py_ssize_t size)
    *Return value: New reference.*

   Create a Unicode object from the Py_UNICODE buffer *u* of the given
   size. *u* may be "NULL" which causes the contents to be undefined.
   It is the user's responsibility to fill in the needed data.  The
   buffer is copied into the new object.

   If the buffer is not "NULL", the return value might be a shared
   object. Therefore, modification of the resulting Unicode object is
   only allowed when *u* is "NULL".

   If the buffer is "NULL", "PyUnicode_READY()" must be called once
   the string content has been filled before using any of the access
   macros such as "PyUnicode_KIND()".

   Deprecated since version 3.3, will be removed in version 3.12: Part
   of the old-style Unicode API, please migrate to using
   "PyUnicode_FromKindAndData()", "PyUnicode_FromWideChar()", or
   "PyUnicode_New()".

Py_UNICODE* PyUnicode_AsUnicode(PyObject *unicode)

   Return a read-only pointer to the Unicode object's internal
   "Py_UNICODE" buffer, or "NULL" on error. This will create the
   "Py_UNICODE*" representation of the object if it is not yet
   available. The buffer is always terminated with an extra null code
   point. Note that the resulting "Py_UNICODE" string may also contain
   embedded null code points, which would cause the string to be
   truncated when used in most C functions.

   Deprecated since version 3.3, will be removed in version 3.12: Part
   of the old-style Unicode API, please migrate to using
   "PyUnicode_AsUCS4()", "PyUnicode_AsWideChar()",
   "PyUnicode_ReadChar()" or similar new APIs.

   Deprecated since version 3.3, will be removed in version 3.10.

PyObject* PyUnicode_TransformDecimalToASCII(Py_UNICODE *s, Py_ssize_t size)
    *Return value: New reference.*

   Create a Unicode object by replacing all decimal digits in
   "Py_UNICODE" buffer of the given *size* by ASCII digits 0--9
   according to their decimal value.  Return "NULL" if an exception
   occurs.

   Deprecated since version 3.3, will be removed in version 3.11: Part
   of the old-style "Py_UNICODE" API; please migrate to using
   "Py_UNICODE_TODECIMAL()".

Py_UNICODE* PyUnicode_AsUnicodeAndSize(PyObject *unicode, Py_ssize_t *size)

   Like "PyUnicode_AsUnicode()", but also saves the "Py_UNICODE()"
   array length (excluding the extra null terminator) in *size*. Note
   that the resulting "Py_UNICODE*" string may contain embedded null
   code points, which would cause the string to be truncated when used
   in most C functions.

   3.3 新版功能.

   Deprecated since version 3.3, will be removed in version 3.12: Part
   of the old-style Unicode API, please migrate to using
   "PyUnicode_AsUCS4()", "PyUnicode_AsWideChar()",
   "PyUnicode_ReadChar()" or similar new APIs.

Py_UNICODE* PyUnicode_AsUnicodeCopy(PyObject *unicode)

   Create a copy of a Unicode string ending with a null code point.
   Return "NULL" and raise a "MemoryError" exception on memory
   allocation failure, otherwise return a new allocated buffer (use
   "PyMem_Free()" to free the buffer). Note that the resulting
   "Py_UNICODE*" string may contain embedded null code points, which
   would cause the string to be truncated when used in most C
   functions.

   3.2 新版功能.

   Please migrate to using "PyUnicode_AsUCS4Copy()" or similar new
   APIs.

Py_ssize_t PyUnicode_GetSize(PyObject *unicode)

   Return the size of the deprecated "Py_UNICODE" representation, in
   code units (this includes surrogate pairs as 2 units).

   Deprecated since version 3.3, will be removed in version 3.12: Part
   of the old-style Unicode API, please migrate to using
   "PyUnicode_GET_LENGTH()".

PyObject* PyUnicode_FromObject(PyObject *obj)
    *Return value: New reference.*

   Copy an instance of a Unicode subtype to a new true Unicode object
   if necessary. If *obj* is already a true Unicode object (not a
   subtype), return the reference with incremented refcount.

   Objects other than Unicode or its subtypes will cause a
   "TypeError".


Locale Encoding
---------------

The current locale encoding can be used to decode text from the
operating system.

PyObject* PyUnicode_DecodeLocaleAndSize(const char *str, Py_ssize_t len, const char *errors)
    *Return value: New reference.*

   Decode a string from UTF-8 on Android and VxWorks, or from the
   current locale encoding on other platforms. The supported error
   handlers are ""strict"" and ""surrogateescape"" (**PEP 383**). The
   decoder uses ""strict"" error handler if *errors* is "NULL".  *str*
   must end with a null character but cannot contain embedded null
   characters.

   Use "PyUnicode_DecodeFSDefaultAndSize()" to decode a string from
   "Py_FileSystemDefaultEncoding" (the locale encoding read at Python
   startup).

   This function ignores the Python UTF-8 mode.

   参见: The "Py_DecodeLocale()" function.

   3.3 新版功能.

   在 3.7 版更改: The function now also uses the current locale
   encoding for the "surrogateescape" error handler, except on
   Android. Previously, "Py_DecodeLocale()" was used for the
   "surrogateescape", and the current locale encoding was used for
   "strict".

PyObject* PyUnicode_DecodeLocale(const char *str, const char *errors)
    *Return value: New reference.*

   Similar to "PyUnicode_DecodeLocaleAndSize()", but compute the
   string length using "strlen()".

   3.3 新版功能.

PyObject* PyUnicode_EncodeLocale(PyObject *unicode, const char *errors)
    *Return value: New reference.*

   Encode a Unicode object to UTF-8 on Android and VxWorks, or to the
   current locale encoding on other platforms. The supported error
   handlers are ""strict"" and ""surrogateescape"" (**PEP 383**). The
   encoder uses ""strict"" error handler if *errors* is "NULL". Return
   a "bytes" object. *unicode* cannot contain embedded null
   characters.

   Use "PyUnicode_EncodeFSDefault()" to encode a string to
   "Py_FileSystemDefaultEncoding" (the locale encoding read at Python
   startup).

   This function ignores the Python UTF-8 mode.

   参见: The "Py_EncodeLocale()" function.

   3.3 新版功能.

   在 3.7 版更改: The function now also uses the current locale
   encoding for the "surrogateescape" error handler, except on
   Android. Previously, "Py_EncodeLocale()" was used for the
   "surrogateescape", and the current locale encoding was used for
   "strict".


File System Encoding
--------------------

To encode and decode file names and other environment strings,
"Py_FileSystemDefaultEncoding" should be used as the encoding, and
"Py_FileSystemDefaultEncodeErrors" should be used as the error handler
(**PEP 383** and **PEP 529**). To encode file names to "bytes" during
argument parsing, the ""O&"" converter should be used, passing
"PyUnicode_FSConverter()" as the conversion function:

int PyUnicode_FSConverter(PyObject* obj, void* result)

   ParseTuple converter: encode "str" objects -- obtained directly or
   through the "os.PathLike" interface -- to "bytes" using
   "PyUnicode_EncodeFSDefault()"; "bytes" objects are output as-is.
   *result* must be a "PyBytesObject*" which must be released when it
   is no longer used.

   3.1 新版功能.

   在 3.6 版更改: 接受一个 *path-like object*。

To decode file names to "str" during argument parsing, the ""O&""
converter should be used, passing "PyUnicode_FSDecoder()" as the
conversion function:

int PyUnicode_FSDecoder(PyObject* obj, void* result)

   ParseTuple converter: decode "bytes" objects -- obtained either
   directly or indirectly through the "os.PathLike" interface -- to
   "str" using "PyUnicode_DecodeFSDefaultAndSize()"; "str" objects are
   output as-is. *result* must be a "PyUnicodeObject*" which must be
   released when it is no longer used.

   3.2 新版功能.

   在 3.6 版更改: 接受一个 *path-like object*。

PyObject* PyUnicode_DecodeFSDefaultAndSize(const char *s, Py_ssize_t size)
    *Return value: New reference.*

   Decode a string using "Py_FileSystemDefaultEncoding" and the
   "Py_FileSystemDefaultEncodeErrors" error handler.

   If "Py_FileSystemDefaultEncoding" is not set, fall back to the
   locale encoding.

   "Py_FileSystemDefaultEncoding" is initialized at startup from the
   locale encoding and cannot be modified later. If you need to decode
   a string from the current locale encoding, use
   "PyUnicode_DecodeLocaleAndSize()".

   参见: The "Py_DecodeLocale()" function.

   在 3.6 版更改: Use "Py_FileSystemDefaultEncodeErrors" error
   handler.

PyObject* PyUnicode_DecodeFSDefault(const char *s)
    *Return value: New reference.*

   Decode a null-terminated string using
   "Py_FileSystemDefaultEncoding" and the
   "Py_FileSystemDefaultEncodeErrors" error handler.

   If "Py_FileSystemDefaultEncoding" is not set, fall back to the
   locale encoding.

   Use "PyUnicode_DecodeFSDefaultAndSize()" if you know the string
   length.

   在 3.6 版更改: Use "Py_FileSystemDefaultEncodeErrors" error
   handler.

PyObject* PyUnicode_EncodeFSDefault(PyObject *unicode)
    *Return value: New reference.*

   Encode a Unicode object to "Py_FileSystemDefaultEncoding" with the
   "Py_FileSystemDefaultEncodeErrors" error handler, and return
   "bytes". Note that the resulting "bytes" object may contain null
   bytes.

   If "Py_FileSystemDefaultEncoding" is not set, fall back to the
   locale encoding.

   "Py_FileSystemDefaultEncoding" is initialized at startup from the
   locale encoding and cannot be modified later. If you need to encode
   a string to the current locale encoding, use
   "PyUnicode_EncodeLocale()".

   参见: The "Py_EncodeLocale()" function.

   3.2 新版功能.

   在 3.6 版更改: Use "Py_FileSystemDefaultEncodeErrors" error
   handler.


wchar_t Support
---------------

"wchar_t" support for platforms which support it:

PyObject* PyUnicode_FromWideChar(const wchar_t *w, Py_ssize_t size)
    *Return value: New reference.*

   Create a Unicode object from the "wchar_t" buffer *w* of the given
   *size*. Passing "-1" as the *size* indicates that the function must
   itself compute the length, using wcslen. Return "NULL" on failure.

Py_ssize_t PyUnicode_AsWideChar(PyObject *unicode, wchar_t *w, Py_ssize_t size)

   Copy the Unicode object contents into the "wchar_t" buffer *w*.  At
   most *size* "wchar_t" characters are copied (excluding a possibly
   trailing null termination character).  Return the number of
   "wchar_t" characters copied or "-1" in case of an error.  Note that
   the resulting "wchar_t*" string may or may not be null-terminated.
   It is the responsibility of the caller to make sure that the
   "wchar_t*" string is null-terminated in case this is required by
   the application. Also, note that the "wchar_t*" string might
   contain null characters, which would cause the string to be
   truncated when used with most C functions.

wchar_t* PyUnicode_AsWideCharString(PyObject *unicode, Py_ssize_t *size)

   Convert the Unicode object to a wide character string. The output
   string always ends with a null character. If *size* is not "NULL",
   write the number of wide characters (excluding the trailing null
   termination character) into **size*. Note that the resulting
   "wchar_t" string might contain null characters, which would cause
   the string to be truncated when used with most C functions. If
   *size* is "NULL" and the "wchar_t*" string contains null characters
   a "ValueError" is raised.

   Returns a buffer allocated by "PyMem_Alloc()" (use "PyMem_Free()"
   to free it) on success. On error, returns "NULL" and **size* is
   undefined. Raises a "MemoryError" if memory allocation is failed.

   3.2 新版功能.

   在 3.7 版更改: Raises a "ValueError" if *size* is "NULL" and the
   "wchar_t*" string contains null characters.


Built-in Codecs
===============

Python provides a set of built-in codecs which are written in C for
speed. All of these codecs are directly usable via the following
functions.

Many of the following APIs take two arguments encoding and errors, and
they have the same semantics as the ones of the built-in "str()"
string object constructor.

Setting encoding to "NULL" causes the default encoding to be used
which is ASCII.  The file system calls should use
"PyUnicode_FSConverter()" for encoding file names. This uses the
variable "Py_FileSystemDefaultEncoding" internally. This variable
should be treated as read-only: on some systems, it will be a pointer
to a static string, on others, it will change at run-time (such as
when the application invokes setlocale).

Error handling is set by errors which may also be set to "NULL"
meaning to use the default handling defined for the codec.  Default
error handling for all built-in codecs is "strict" ("ValueError" is
raised).

The codecs all use a similar interface.  Only deviation from the
following generic ones are documented for simplicity.


Generic Codecs
--------------

These are the generic codec APIs:

PyObject* PyUnicode_Decode(const char *s, Py_ssize_t size, const char *encoding, const char *errors)
    *Return value: New reference.*

   Create a Unicode object by decoding *size* bytes of the encoded
   string *s*. *encoding* and *errors* have the same meaning as the
   parameters of the same name in the "str()" built-in function.  The
   codec to be used is looked up using the Python codec registry.
   Return "NULL" if an exception was raised by the codec.

PyObject* PyUnicode_AsEncodedString(PyObject *unicode, const char *encoding, const char *errors)
    *Return value: New reference.*

   Encode a Unicode object and return the result as Python bytes
   object. *encoding* and *errors* have the same meaning as the
   parameters of the same name in the Unicode "encode()" method. The
   codec to be used is looked up using the Python codec registry.
   Return "NULL" if an exception was raised by the codec.

PyObject* PyUnicode_Encode(const Py_UNICODE *s, Py_ssize_t size, const char *encoding, const char *errors)
    *Return value: New reference.*

   Encode the "Py_UNICODE" buffer *s* of the given *size* and return a
   Python bytes object.  *encoding* and *errors* have the same meaning
   as the parameters of the same name in the Unicode "encode()"
   method.  The codec to be used is looked up using the Python codec
   registry.  Return "NULL" if an exception was raised by the codec.

   Deprecated since version 3.3, will be removed in version 3.11: Part
   of the old-style "Py_UNICODE" API; please migrate to using
   "PyUnicode_AsEncodedString()".


UTF-8 Codecs
------------

These are the UTF-8 codec APIs:

PyObject* PyUnicode_DecodeUTF8(const char *s, Py_ssize_t size, const char *errors)
    *Return value: New reference.*

   Create a Unicode object by decoding *size* bytes of the UTF-8
   encoded string *s*. Return "NULL" if an exception was raised by the
   codec.

PyObject* PyUnicode_DecodeUTF8Stateful(const char *s, Py_ssize_t size, const char *errors, Py_ssize_t *consumed)
    *Return value: New reference.*

   If *consumed* is "NULL", behave like "PyUnicode_DecodeUTF8()". If
   *consumed* is not "NULL", trailing incomplete UTF-8 byte sequences
   will not be treated as an error. Those bytes will not be decoded
   and the number of bytes that have been decoded will be stored in
   *consumed*.

PyObject* PyUnicode_AsUTF8String(PyObject *unicode)
    *Return value: New reference.*

   Encode a Unicode object using UTF-8 and return the result as Python
   bytes object.  Error handling is "strict".  Return "NULL" if an
   exception was raised by the codec.

const char* PyUnicode_AsUTF8AndSize(PyObject *unicode, Py_ssize_t *size)

   Return a pointer to the UTF-8 encoding of the Unicode object, and
   store the size of the encoded representation (in bytes) in *size*.
   The *size* argument can be "NULL"; in this case no size will be
   stored.  The returned buffer always has an extra null byte appended
   (not included in *size*), regardless of whether there are any other
   null code points.

   In the case of an error, "NULL" is returned with an exception set
   and no *size* is stored.

   This caches the UTF-8 representation of the string in the Unicode
   object, and subsequent calls will return a pointer to the same
   buffer.  The caller is not responsible for deallocating the buffer.

   3.3 新版功能.

   在 3.7 版更改: The return type is now "const char *" rather of
   "char *".

const char* PyUnicode_AsUTF8(PyObject *unicode)

   As "PyUnicode_AsUTF8AndSize()", but does not store the size.

   3.3 新版功能.

   在 3.7 版更改: The return type is now "const char *" rather of
   "char *".

PyObject* PyUnicode_EncodeUTF8(const Py_UNICODE *s, Py_ssize_t size, const char *errors)
    *Return value: New reference.*

   Encode the "Py_UNICODE" buffer *s* of the given *size* using UTF-8
   and return a Python bytes object.  Return "NULL" if an exception
   was raised by the codec.

   Deprecated since version 3.3, will be removed in version 3.11: Part
   of the old-style "Py_UNICODE" API; please migrate to using
   "PyUnicode_AsUTF8String()", "PyUnicode_AsUTF8AndSize()" or
   "PyUnicode_AsEncodedString()".


UTF-32 Codecs
-------------

These are the UTF-32 codec APIs:

PyObject* PyUnicode_DecodeUTF32(const char *s, Py_ssize_t size, const char *errors, int *byteorder)
    *Return value: New reference.*

   Decode *size* bytes from a UTF-32 encoded buffer string and return
   the corresponding Unicode object.  *errors* (if non-"NULL") defines
   the error handling. It defaults to "strict".

   If *byteorder* is non-"NULL", the decoder starts decoding using the
   given byte order:

      *byteorder == -1: little endian
      *byteorder == 0:  native order
      *byteorder == 1:  big endian

   If "*byteorder" is zero, and the first four bytes of the input data
   are a byte order mark (BOM), the decoder switches to this byte
   order and the BOM is not copied into the resulting Unicode string.
   If "*byteorder" is "-1" or "1", any byte order mark is copied to
   the output.

   After completion, **byteorder* is set to the current byte order at
   the end of input data.

   If *byteorder* is "NULL", the codec starts in native order mode.

   Return "NULL" if an exception was raised by the codec.

PyObject* PyUnicode_DecodeUTF32Stateful(const char *s, Py_ssize_t size, const char *errors, int *byteorder, Py_ssize_t *consumed)
    *Return value: New reference.*

   If *consumed* is "NULL", behave like "PyUnicode_DecodeUTF32()". If
   *consumed* is not "NULL", "PyUnicode_DecodeUTF32Stateful()" will
   not treat trailing incomplete UTF-32 byte sequences (such as a
   number of bytes not divisible by four) as an error. Those bytes
   will not be decoded and the number of bytes that have been decoded
   will be stored in *consumed*.

PyObject* PyUnicode_AsUTF32String(PyObject *unicode)
    *Return value: New reference.*

   Return a Python byte string using the UTF-32 encoding in native
   byte order. The string always starts with a BOM mark.  Error
   handling is "strict". Return "NULL" if an exception was raised by
   the codec.

PyObject* PyUnicode_EncodeUTF32(const Py_UNICODE *s, Py_ssize_t size, const char *errors, int byteorder)
    *Return value: New reference.*

   Return a Python bytes object holding the UTF-32 encoded value of
   the Unicode data in *s*.  Output is written according to the
   following byte order:

      byteorder == -1: little endian
      byteorder == 0:  native byte order (writes a BOM mark)
      byteorder == 1:  big endian

   If byteorder is "0", the output string will always start with the
   Unicode BOM mark (U+FEFF). In the other two modes, no BOM mark is
   prepended.

   If "Py_UNICODE_WIDE" is not defined, surrogate pairs will be output
   as a single code point.

   Return "NULL" if an exception was raised by the codec.

   Deprecated since version 3.3, will be removed in version 3.11: Part
   of the old-style "Py_UNICODE" API; please migrate to using
   "PyUnicode_AsUTF32String()" or "PyUnicode_AsEncodedString()".


UTF-16 Codecs
-------------

These are the UTF-16 codec APIs:

PyObject* PyUnicode_DecodeUTF16(const char *s, Py_ssize_t size, const char *errors, int *byteorder)
    *Return value: New reference.*

   Decode *size* bytes from a UTF-16 encoded buffer string and return
   the corresponding Unicode object.  *errors* (if non-"NULL") defines
   the error handling. It defaults to "strict".

   If *byteorder* is non-"NULL", the decoder starts decoding using the
   given byte order:

      *byteorder == -1: little endian
      *byteorder == 0:  native order
      *byteorder == 1:  big endian

   If "*byteorder" is zero, and the first two bytes of the input data
   are a byte order mark (BOM), the decoder switches to this byte
   order and the BOM is not copied into the resulting Unicode string.
   If "*byteorder" is "-1" or "1", any byte order mark is copied to
   the output (where it will result in either a "\ufeff" or a "\ufffe"
   character).

   After completion, **byteorder* is set to the current byte order at
   the end of input data.

   If *byteorder* is "NULL", the codec starts in native order mode.

   Return "NULL" if an exception was raised by the codec.

PyObject* PyUnicode_DecodeUTF16Stateful(const char *s, Py_ssize_t size, const char *errors, int *byteorder, Py_ssize_t *consumed)
    *Return value: New reference.*

   If *consumed* is "NULL", behave like "PyUnicode_DecodeUTF16()". If
   *consumed* is not "NULL", "PyUnicode_DecodeUTF16Stateful()" will
   not treat trailing incomplete UTF-16 byte sequences (such as an odd
   number of bytes or a split surrogate pair) as an error. Those bytes
   will not be decoded and the number of bytes that have been decoded
   will be stored in *consumed*.

PyObject* PyUnicode_AsUTF16String(PyObject *unicode)
    *Return value: New reference.*

   Return a Python byte string using the UTF-16 encoding in native
   byte order. The string always starts with a BOM mark.  Error
   handling is "strict". Return "NULL" if an exception was raised by
   the codec.

PyObject* PyUnicode_EncodeUTF16(const Py_UNICODE *s, Py_ssize_t size, const char *errors, int byteorder)
    *Return value: New reference.*

   Return a Python bytes object holding the UTF-16 encoded value of
   the Unicode data in *s*.  Output is written according to the
   following byte order:

      byteorder == -1: little endian
      byteorder == 0:  native byte order (writes a BOM mark)
      byteorder == 1:  big endian

   If byteorder is "0", the output string will always start with the
   Unicode BOM mark (U+FEFF). In the other two modes, no BOM mark is
   prepended.

   If "Py_UNICODE_WIDE" is defined, a single "Py_UNICODE" value may
   get represented as a surrogate pair. If it is not defined, each
   "Py_UNICODE" values is interpreted as a UCS-2 character.

   Return "NULL" if an exception was raised by the codec.

   Deprecated since version 3.3, will be removed in version 3.11: Part
   of the old-style "Py_UNICODE" API; please migrate to using
   "PyUnicode_AsUTF16String()" or "PyUnicode_AsEncodedString()".


UTF-7 Codecs
------------

These are the UTF-7 codec APIs:

PyObject* PyUnicode_DecodeUTF7(const char *s, Py_ssize_t size, const char *errors)
    *Return value: New reference.*

   Create a Unicode object by decoding *size* bytes of the UTF-7
   encoded string *s*.  Return "NULL" if an exception was raised by
   the codec.

PyObject* PyUnicode_DecodeUTF7Stateful(const char *s, Py_ssize_t size, const char *errors, Py_ssize_t *consumed)
    *Return value: New reference.*

   If *consumed* is "NULL", behave like "PyUnicode_DecodeUTF7()".  If
   *consumed* is not "NULL", trailing incomplete UTF-7 base-64
   sections will not be treated as an error.  Those bytes will not be
   decoded and the number of bytes that have been decoded will be
   stored in *consumed*.

PyObject* PyUnicode_EncodeUTF7(const Py_UNICODE *s, Py_ssize_t size, int base64SetO, int base64WhiteSpace, const char *errors)
    *Return value: New reference.*

   Encode the "Py_UNICODE" buffer of the given size using UTF-7 and
   return a Python bytes object.  Return "NULL" if an exception was
   raised by the codec.

   If *base64SetO* is nonzero, "Set O" (punctuation that has no
   otherwise special meaning) will be encoded in base-64.  If
   *base64WhiteSpace* is nonzero, whitespace will be encoded in
   base-64.  Both are set to zero for the Python "utf-7" codec.

   Deprecated since version 3.3, will be removed in version 3.11: Part
   of the old-style "Py_UNICODE" API; please migrate to using
   "PyUnicode_AsEncodedString()".


Unicode-Escape Codecs
---------------------

These are the "Unicode Escape" codec APIs:

PyObject* PyUnicode_DecodeUnicodeEscape(const char *s, Py_ssize_t size, const char *errors)
    *Return value: New reference.*

   Create a Unicode object by decoding *size* bytes of the Unicode-
   Escape encoded string *s*.  Return "NULL" if an exception was
   raised by the codec.

PyObject* PyUnicode_AsUnicodeEscapeString(PyObject *unicode)
    *Return value: New reference.*

   Encode a Unicode object using Unicode-Escape and return the result
   as a bytes object.  Error handling is "strict".  Return "NULL" if
   an exception was raised by the codec.

PyObject* PyUnicode_EncodeUnicodeEscape(const Py_UNICODE *s, Py_ssize_t size)
    *Return value: New reference.*

   Encode the "Py_UNICODE" buffer of the given *size* using Unicode-
   Escape and return a bytes object.  Return "NULL" if an exception
   was raised by the codec.

   Deprecated since version 3.3, will be removed in version 3.11: Part
   of the old-style "Py_UNICODE" API; please migrate to using
   "PyUnicode_AsUnicodeEscapeString()".


Raw-Unicode-Escape Codecs
-------------------------

These are the "Raw Unicode Escape" codec APIs:

PyObject* PyUnicode_DecodeRawUnicodeEscape(const char *s, Py_ssize_t size, const char *errors)
    *Return value: New reference.*

   Create a Unicode object by decoding *size* bytes of the Raw-
   Unicode-Escape encoded string *s*.  Return "NULL" if an exception
   was raised by the codec.

PyObject* PyUnicode_AsRawUnicodeEscapeString(PyObject *unicode)
    *Return value: New reference.*

   Encode a Unicode object using Raw-Unicode-Escape and return the
   result as a bytes object.  Error handling is "strict".  Return
   "NULL" if an exception was raised by the codec.

PyObject* PyUnicode_EncodeRawUnicodeEscape(const Py_UNICODE *s, Py_ssize_t size)
    *Return value: New reference.*

   Encode the "Py_UNICODE" buffer of the given *size* using Raw-
   Unicode-Escape and return a bytes object.  Return "NULL" if an
   exception was raised by the codec.

   Deprecated since version 3.3, will be removed in version 3.11: Part
   of the old-style "Py_UNICODE" API; please migrate to using
   "PyUnicode_AsRawUnicodeEscapeString()" or
   "PyUnicode_AsEncodedString()".


Latin-1 Codecs
--------------

These are the Latin-1 codec APIs: Latin-1 corresponds to the first 256
Unicode ordinals and only these are accepted by the codecs during
encoding.

PyObject* PyUnicode_DecodeLatin1(const char *s, Py_ssize_t size, const char *errors)
    *Return value: New reference.*

   Create a Unicode object by decoding *size* bytes of the Latin-1
   encoded string *s*.  Return "NULL" if an exception was raised by
   the codec.

PyObject* PyUnicode_AsLatin1String(PyObject *unicode)
    *Return value: New reference.*

   Encode a Unicode object using Latin-1 and return the result as
   Python bytes object.  Error handling is "strict".  Return "NULL" if
   an exception was raised by the codec.

PyObject* PyUnicode_EncodeLatin1(const Py_UNICODE *s, Py_ssize_t size, const char *errors)
    *Return value: New reference.*

   Encode the "Py_UNICODE" buffer of the given *size* using Latin-1
   and return a Python bytes object.  Return "NULL" if an exception
   was raised by the codec.

   Deprecated since version 3.3, will be removed in version 3.11: Part
   of the old-style "Py_UNICODE" API; please migrate to using
   "PyUnicode_AsLatin1String()" or "PyUnicode_AsEncodedString()".


ASCII Codecs
------------

These are the ASCII codec APIs.  Only 7-bit ASCII data is accepted.
All other codes generate errors.

PyObject* PyUnicode_DecodeASCII(const char *s, Py_ssize_t size, const char *errors)
    *Return value: New reference.*

   Create a Unicode object by decoding *size* bytes of the ASCII
   encoded string *s*.  Return "NULL" if an exception was raised by
   the codec.

PyObject* PyUnicode_AsASCIIString(PyObject *unicode)
    *Return value: New reference.*

   Encode a Unicode object using ASCII and return the result as Python
   bytes object.  Error handling is "strict".  Return "NULL" if an
   exception was raised by the codec.

PyObject* PyUnicode_EncodeASCII(const Py_UNICODE *s, Py_ssize_t size, const char *errors)
    *Return value: New reference.*

   Encode the "Py_UNICODE" buffer of the given *size* using ASCII and
   return a Python bytes object.  Return "NULL" if an exception was
   raised by the codec.

   Deprecated since version 3.3, will be removed in version 3.11: Part
   of the old-style "Py_UNICODE" API; please migrate to using
   "PyUnicode_AsASCIIString()" or "PyUnicode_AsEncodedString()".


Character Map Codecs
--------------------

This codec is special in that it can be used to implement many
different codecs (and this is in fact what was done to obtain most of
the standard codecs included in the "encodings" package). The codec
uses mapping to encode and decode characters.  The mapping objects
provided must support the "__getitem__()" mapping interface;
dictionaries and sequences work well.

These are the mapping codec APIs:

PyObject* PyUnicode_DecodeCharmap(const char *data, Py_ssize_t size, PyObject *mapping, const char *errors)
    *Return value: New reference.*

   Create a Unicode object by decoding *size* bytes of the encoded
   string *s* using the given *mapping* object.  Return "NULL" if an
   exception was raised by the codec.

   If *mapping* is "NULL", Latin-1 decoding will be applied.  Else
   *mapping* must map bytes ordinals (integers in the range from 0 to
   255) to Unicode strings, integers (which are then interpreted as
   Unicode ordinals) or "None".  Unmapped data bytes -- ones which
   cause a "LookupError", as well as ones which get mapped to "None",
   "0xFFFE" or "'\ufffe'", are treated as undefined mappings and cause
   an error.

PyObject* PyUnicode_AsCharmapString(PyObject *unicode, PyObject *mapping)
    *Return value: New reference.*

   Encode a Unicode object using the given *mapping* object and return
   the result as a bytes object.  Error handling is "strict".  Return
   "NULL" if an exception was raised by the codec.

   The *mapping* object must map Unicode ordinal integers to bytes
   objects, integers in the range from 0 to 255 or "None".  Unmapped
   character ordinals (ones which cause a "LookupError") as well as
   mapped to "None" are treated as "undefined mapping" and cause an
   error.

PyObject* PyUnicode_EncodeCharmap(const Py_UNICODE *s, Py_ssize_t size, PyObject *mapping, const char *errors)
    *Return value: New reference.*

   Encode the "Py_UNICODE" buffer of the given *size* using the given
   *mapping* object and return the result as a bytes object.  Return
   "NULL" if an exception was raised by the codec.

   Deprecated since version 3.3, will be removed in version 3.11: Part
   of the old-style "Py_UNICODE" API; please migrate to using
   "PyUnicode_AsCharmapString()" or "PyUnicode_AsEncodedString()".

The following codec API is special in that maps Unicode to Unicode.

PyObject* PyUnicode_Translate(PyObject *str, PyObject *table, const char *errors)
    *Return value: New reference.*

   Translate a string by applying a character mapping table to it and
   return the resulting Unicode object. Return "NULL" if an exception
   was raised by the codec.

   The mapping table must map Unicode ordinal integers to Unicode
   ordinal integers or "None" (causing deletion of the character).

   Mapping tables need only provide the "__getitem__()" interface;
   dictionaries and sequences work well.  Unmapped character ordinals
   (ones which cause a "LookupError") are left untouched and are
   copied as-is.

   *errors* has the usual meaning for codecs. It may be "NULL" which
   indicates to use the default error handling.

PyObject* PyUnicode_TranslateCharmap(const Py_UNICODE *s, Py_ssize_t size, PyObject *mapping, const char *errors)
    *Return value: New reference.*

   Translate a "Py_UNICODE" buffer of the given *size* by applying a
   character *mapping* table to it and return the resulting Unicode
   object. Return "NULL" when an exception was raised by the codec.

   Deprecated since version 3.3, will be removed in version 3.11: Part
   of the old-style "Py_UNICODE" API; please migrate to using
   "PyUnicode_Translate()". or generic codec based API


MBCS codecs for Windows
-----------------------

These are the MBCS codec APIs. They are currently only available on
Windows and use the Win32 MBCS converters to implement the
conversions.  Note that MBCS (or DBCS) is a class of encodings, not
just one.  The target encoding is defined by the user settings on the
machine running the codec.

PyObject* PyUnicode_DecodeMBCS(const char *s, Py_ssize_t size, const char *errors)
    *Return value: New reference.*

   Create a Unicode object by decoding *size* bytes of the MBCS
   encoded string *s*. Return "NULL" if an exception was raised by the
   codec.

PyObject* PyUnicode_DecodeMBCSStateful(const char *s, Py_ssize_t size, const char *errors, Py_ssize_t *consumed)
    *Return value: New reference.*

   If *consumed* is "NULL", behave like "PyUnicode_DecodeMBCS()". If
   *consumed* is not "NULL", "PyUnicode_DecodeMBCSStateful()" will not
   decode trailing lead byte and the number of bytes that have been
   decoded will be stored in *consumed*.

PyObject* PyUnicode_AsMBCSString(PyObject *unicode)
    *Return value: New reference.*

   Encode a Unicode object using MBCS and return the result as Python
   bytes object.  Error handling is "strict".  Return "NULL" if an
   exception was raised by the codec.

PyObject* PyUnicode_EncodeCodePage(int code_page, PyObject *unicode, const char *errors)
    *Return value: New reference.*

   Encode the Unicode object using the specified code page and return
   a Python bytes object.  Return "NULL" if an exception was raised by
   the codec. Use "CP_ACP" code page to get the MBCS encoder.

   3.3 新版功能.

PyObject* PyUnicode_EncodeMBCS(const Py_UNICODE *s, Py_ssize_t size, const char *errors)
    *Return value: New reference.*

   Encode the "Py_UNICODE" buffer of the given *size* using MBCS and
   return a Python bytes object.  Return "NULL" if an exception was
   raised by the codec.

   Deprecated since version 3.3, will be removed in version 4.0: Part
   of the old-style "Py_UNICODE" API; please migrate to using
   "PyUnicode_AsMBCSString()", "PyUnicode_EncodeCodePage()" or
   "PyUnicode_AsEncodedString()".


Methods & Slots
---------------


Methods and Slot Functions
==========================

The following APIs are capable of handling Unicode objects and strings
on input (we refer to them as strings in the descriptions) and return
Unicode objects or integers as appropriate.

They all return "NULL" or "-1" if an exception occurs.

PyObject* PyUnicode_Concat(PyObject *left, PyObject *right)
    *Return value: New reference.*

   Concat two strings giving a new Unicode string.

PyObject* PyUnicode_Split(PyObject *s, PyObject *sep, Py_ssize_t maxsplit)
    *Return value: New reference.*

   Split a string giving a list of Unicode strings.  If *sep* is
   "NULL", splitting will be done at all whitespace substrings.
   Otherwise, splits occur at the given separator.  At most *maxsplit*
   splits will be done.  If negative, no limit is set.  Separators are
   not included in the resulting list.

PyObject* PyUnicode_Splitlines(PyObject *s, int keepend)
    *Return value: New reference.*

   Split a Unicode string at line breaks, returning a list of Unicode
   strings. CRLF is considered to be one line break.  If *keepend* is
   "0", the Line break characters are not included in the resulting
   strings.

PyObject* PyUnicode_Join(PyObject *separator, PyObject *seq)
    *Return value: New reference.*

   Join a sequence of strings using the given *separator* and return
   the resulting Unicode string.

Py_ssize_t PyUnicode_Tailmatch(PyObject *str, PyObject *substr, Py_ssize_t start, Py_ssize_t end, int direction)

   Return "1" if *substr* matches "str[start:end]" at the given tail
   end (*direction* == "-1" means to do a prefix match, *direction* ==
   "1" a suffix match), "0" otherwise. Return "-1" if an error
   occurred.

Py_ssize_t PyUnicode_Find(PyObject *str, PyObject *substr, Py_ssize_t start, Py_ssize_t end, int direction)

   Return the first position of *substr* in "str[start:end]" using the
   given *direction* (*direction* == "1" means to do a forward search,
   *direction* == "-1" a backward search).  The return value is the
   index of the first match; a value of "-1" indicates that no match
   was found, and "-2" indicates that an error occurred and an
   exception has been set.

Py_ssize_t PyUnicode_FindChar(PyObject *str, Py_UCS4 ch, Py_ssize_t start, Py_ssize_t end, int direction)

   Return the first position of the character *ch* in "str[start:end]"
   using the given *direction* (*direction* == "1" means to do a
   forward search, *direction* == "-1" a backward search).  The return
   value is the index of the first match; a value of "-1" indicates
   that no match was found, and "-2" indicates that an error occurred
   and an exception has been set.

   3.3 新版功能.

   在 3.7 版更改: *start* and *end* are now adjusted to behave like
   "str[start:end]".

Py_ssize_t PyUnicode_Count(PyObject *str, PyObject *substr, Py_ssize_t start, Py_ssize_t end)

   Return the number of non-overlapping occurrences of *substr* in
   "str[start:end]".  Return "-1" if an error occurred.

PyObject* PyUnicode_Replace(PyObject *str, PyObject *substr, PyObject *replstr, Py_ssize_t maxcount)
    *Return value: New reference.*

   Replace at most *maxcount* occurrences of *substr* in *str* with
   *replstr* and return the resulting Unicode object. *maxcount* ==
   "-1" means replace all occurrences.

int PyUnicode_Compare(PyObject *left, PyObject *right)

   Compare two strings and return "-1", "0", "1" for less than, equal,
   and greater than, respectively.

   This function returns "-1" upon failure, so one should call
   "PyErr_Occurred()" to check for errors.

int PyUnicode_CompareWithASCIIString(PyObject *uni, const char *string)

   Compare a Unicode object, *uni*, with *string* and return "-1",
   "0", "1" for less than, equal, and greater than, respectively. It
   is best to pass only ASCII-encoded strings, but the function
   interprets the input string as ISO-8859-1 if it contains non-ASCII
   characters.

   This function does not raise exceptions.

PyObject* PyUnicode_RichCompare(PyObject *left, PyObject *right, int op)
    *Return value: New reference.*

   Rich compare two Unicode strings and return one of the following:

   * "NULL" in case an exception was raised

   * "Py_True" or "Py_False" for successful comparisons

   * "Py_NotImplemented" in case the type combination is unknown

   Possible values for *op* are "Py_GT", "Py_GE", "Py_EQ", "Py_NE",
   "Py_LT", and "Py_LE".

PyObject* PyUnicode_Format(PyObject *format, PyObject *args)
    *Return value: New reference.*

   Return a new string object from *format* and *args*; this is
   analogous to "format % args".

int PyUnicode_Contains(PyObject *container, PyObject *element)

   Check whether *element* is contained in *container* and return true
   or false accordingly.

   *element* has to coerce to a one element Unicode string. "-1" is
   returned if there was an error.

void PyUnicode_InternInPlace(PyObject **string)

   Intern the argument **string* in place.  The argument must be the
   address of a pointer variable pointing to a Python Unicode string
   object.  If there is an existing interned string that is the same
   as **string*, it sets **string* to it (decrementing the reference
   count of the old string object and incrementing the reference count
   of the interned string object), otherwise it leaves **string* alone
   and interns it (incrementing its reference count). (Clarification:
   even though there is a lot of talk about reference counts, think of
   this function as reference-count-neutral; you own the object after
   the call if and only if you owned it before the call.)

PyObject* PyUnicode_InternFromString(const char *v)
    *Return value: New reference.*

   A combination of "PyUnicode_FromString()" and
   "PyUnicode_InternInPlace()", returning either a new Unicode string
   object that has been interned, or a new ("owned") reference to an
   earlier interned string object with the same value.
