Bytes Objects
*************

These functions raise "TypeError" when expecting a bytes parameter and
called with a non-bytes parameter.

type PyBytesObject

   This subtype of "PyObject" represents a Python bytes object.

PyTypeObject PyBytes_Type
    * Part of the Stable ABI.*

   This instance of "PyTypeObject" represents the Python bytes type;
   it is the same object as "bytes" in the Python layer.

int PyBytes_Check(PyObject *o)

   Return true if the object *o* is a bytes object or an instance of a
   subtype of the bytes type.  This function always succeeds.

int PyBytes_CheckExact(PyObject *o)

   Return true if the object *o* is a bytes object, but not an
   instance of a subtype of the bytes type.  This function always
   succeeds.

PyObject *PyBytes_FromString(const char *v)
    *Return value: New reference.** Part of the Stable ABI.** Thread
   safety: Atomic.*

   Return a new bytes object with a copy of the string *v* as value on
   success, and "NULL" on failure.  The parameter *v* must not be
   "NULL"; it will not be checked.

PyObject *PyBytes_FromStringAndSize(const char *v, Py_ssize_t len)
    *Return value: New reference.** Part of the Stable ABI.** Thread
   safety: Atomic.*

   Return a new bytes object with a copy of the string *v* as value
   and length *len* on success, and "NULL" on failure.  If *v* is
   "NULL", the contents of the bytes object are uninitialized.

   Soft deprecated since version 3.15: Use the "PyBytesWriter" API
   instead of "PyBytes_FromStringAndSize(NULL, len)".

PyObject *PyBytes_FromFormat(const char *format, ...)
    *Return value: New reference.** Part of the Stable ABI.** Thread
   safety: Atomic.*

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

   +---------------------+-----------------+----------------------------------+
   | Format Characters   | Type            | Comment                          |
   |=====================|=================|==================================|
   | "%%"                | *n/a*           | The literal % character.         |
   +---------------------+-----------------+----------------------------------+
   | "%c"                | int             | A single byte, represented as a  |
   |                     |                 | C int.                           |
   +---------------------+-----------------+----------------------------------+
   | "%d"                | int             | Equivalent to "printf("%d")".    |
   |                     |                 | [1]                              |
   +---------------------+-----------------+----------------------------------+
   | "%u"                | unsigned int    | Equivalent to "printf("%u")".    |
   |                     |                 | [1]                              |
   +---------------------+-----------------+----------------------------------+
   | "%ld"               | long            | Equivalent to "printf("%ld")".   |
   |                     |                 | [1]                              |
   +---------------------+-----------------+----------------------------------+
   | "%lu"               | unsigned long   | Equivalent to "printf("%lu")".   |
   |                     |                 | [1]                              |
   +---------------------+-----------------+----------------------------------+
   | "%zd"               | "Py_ssize_t"    | Equivalent to "printf("%zd")".   |
   |                     |                 | [1]                              |
   +---------------------+-----------------+----------------------------------+
   | "%zu"               | size_t          | Equivalent to "printf("%zu")".   |
   |                     |                 | [1]                              |
   +---------------------+-----------------+----------------------------------+
   | "%i"                | int             | Equivalent to "printf("%i")".    |
   |                     |                 | [1]                              |
   +---------------------+-----------------+----------------------------------+
   | "%x"                | int             | Equivalent to "printf("%x")".    |
   |                     |                 | [1]                              |
   +---------------------+-----------------+----------------------------------+
   | "%s"                | const char*     | A null-terminated C character    |
   |                     |                 | array.                           |
   +---------------------+-----------------+----------------------------------+
   | "%p"                | const void*     | The hex representation of a C    |
   |                     |                 | pointer. Mostly equivalent to    |
   |                     |                 | "printf("%p")" except that it is |
   |                     |                 | guaranteed to start with the     |
   |                     |                 | literal "0x" regardless of what  |
   |                     |                 | the platform’s "printf" yields.  |
   +---------------------+-----------------+----------------------------------+

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

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

PyObject *PyBytes_FromFormatV(const char *format, va_list vargs)
    *Return value: New reference.** Part of the Stable ABI.** Thread
   safety: Atomic.*

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

PyObject *PyBytes_FromObject(PyObject *o)
    *Return value: New reference.** Part of the Stable ABI.** Thread
   safety: Safe for concurrent use on the same object.*

   Return the bytes representation of object *o* that implements the
   buffer protocol.

   Note:

     If the object implements the buffer protocol, then the buffer
     must not be mutated while the bytes object is being created.

Py_ssize_t PyBytes_Size(PyObject *o)
    * Part of the Stable ABI.** Thread safety: Atomic.*

   Return the length of the bytes in bytes object *o*.

Py_ssize_t PyBytes_GET_SIZE(PyObject *o)
    * Thread safety: Atomic.*

   Similar to "PyBytes_Size()", but without error checking.

char *PyBytes_AsString(PyObject *o)
    * Part of the Stable ABI.** Thread safety: Safe to call from
   multiple threads with external synchronization only.*

   Return a pointer to the contents of *o*.  The pointer refers to the
   internal buffer of *o*, which consists of "len(o) + 1" bytes.  The
   last byte in the buffer is always null, regardless of whether there
   are any other null bytes.  The data must not be modified in any
   way, unless the object was just created using
   "PyBytes_FromStringAndSize(NULL, size)". It must not be
   deallocated.  If *o* is not a bytes object at all,
   "PyBytes_AsString()" returns "NULL" and raises "TypeError".

char *PyBytes_AS_STRING(PyObject *string)
    * Thread safety: Safe to call from multiple threads with external
   synchronization only.*

   Similar to "PyBytes_AsString()", but without error checking.

int PyBytes_AsStringAndSize(PyObject *obj, char **buffer, Py_ssize_t *length)
    * Part of the Stable ABI.** Thread safety: Safe to call from
   multiple threads with external synchronization only.*

   Return the null-terminated contents of the object *obj* through the
   output variables *buffer* and *length*. Returns "0" on success.

   If *length* is "NULL", the bytes object may not contain embedded
   null bytes; if it does, the function returns "-1" and a
   "ValueError" is raised.

   The buffer refers to an internal buffer of *obj*, which includes an
   additional null byte at the end (not counted in *length*).  The
   data must not be modified in any way, unless the object was just
   created using "PyBytes_FromStringAndSize(NULL, size)".  It must not
   be deallocated.  If *obj* is not a bytes object at all,
   "PyBytes_AsStringAndSize()" returns "-1" and raises "TypeError".

   Changed in version 3.5: Previously, "TypeError" was raised when
   embedded null bytes were encountered in the bytes object.

void PyBytes_Concat(PyObject **bytes, PyObject *newpart)
    * Part of the Stable ABI.** Thread safety: Safe for concurrent use
   on the same object.*

   Create a new bytes object in **bytes* containing the contents of
   *newpart* appended to *bytes*; the caller will own the new
   reference. The reference to the old value of *bytes* will be
   “*stolen*”. If the new object cannot be created, the old reference
   to *bytes* will still be “stolen”, the value of **bytes* will be
   set to "NULL", and the appropriate exception will be set.

   Note:

     If *newpart* implements the buffer protocol, then the buffer must
     not be mutated while the new bytes object is being created.

void PyBytes_ConcatAndDel(PyObject **bytes, PyObject *newpart)
    * Part of the Stable ABI.** Thread safety: Safe for concurrent use
   on the same object.*

   Create a new bytes object in **bytes* containing the contents of
   *newpart* appended to *bytes*.  This version releases the *strong
   reference* to *newpart* (i.e. decrements its reference count).

   Note:

     If *newpart* implements the buffer protocol, then the buffer must
     not be mutated while the new bytes object is being created.

PyObject *PyBytes_Join(PyObject *sep, PyObject *iterable)
    * Thread safety: Safe for concurrent use on the same object.*

   Similar to "sep.join(iterable)" in Python.

   *sep* must be Python "bytes" object. (Note that "PyUnicode_Join()"
   accepts "NULL" separator and treats it as a space, whereas
   "PyBytes_Join()" doesn’t accept "NULL" separator.)

   *iterable* must be an iterable object yielding objects that
   implement the buffer protocol.

   On success, return a new "bytes" object. On error, set an exception
   and return "NULL".

   Added in version 3.14.

   Note:

     If *iterable* objects implement the buffer protocol, then the
     buffers must not be mutated while the new bytes object is being
     created.

int _PyBytes_Resize(PyObject **bytes, Py_ssize_t newsize)
    * Thread safety: Safe to call without external synchronization on
   distinct objects.*

   Resize a bytes object. *newsize* will be the new length of the
   bytes object. You can think of it as creating a new bytes object
   and destroying the old one, only more efficiently. Pass the address
   of an existing bytes object as an lvalue (it may be written into),
   and the new size desired.  On success, **bytes* holds the resized
   bytes object and "0" is returned; the address in **bytes* may
   differ from its input value.  If the reallocation fails, the
   original bytes object at **bytes* is deallocated, **bytes* is set
   to "NULL", "MemoryError" is set, and "-1" is returned.

   Soft deprecated since version 3.15: Use the "PyBytesWriter" API
   instead.

PyObject *PyBytes_Repr(PyObject *bytes, int smartquotes)
    * Part of the Stable ABI.** Thread safety: Atomic.*

   Get the string representation of *bytes*. This function is
   currently used to implement "bytes.__repr__()" in Python.

   This function does not do type checking; it is undefined behavior
   to pass *bytes* as a non-bytes object or "NULL".

   If *smartquotes* is true, the representation will use a double-
   quoted string instead of single-quoted string when single-quotes
   are present in *bytes*. For example, the byte string "'Python'"
   would be represented as "b"'Python'"" when *smartquotes* is true,
   or "b'\'Python\''" when it is false.

   On success, this function returns a *strong reference* to a "str"
   object containing the representation. On failure, this returns
   "NULL" with an exception set.

PyObject *PyBytes_DecodeEscape(const char *s, Py_ssize_t len, const char *errors, Py_ssize_t unicode, const char *recode_encoding)
    * Part of the Stable ABI.** Thread safety: Atomic.*

   Unescape a backslash-escaped string *s*. *s* must not be "NULL".
   *len* must be the size of *s*.

   *errors* must be one of ""strict"", ""replace"", or ""ignore"". If
   *errors* is "NULL", then ""strict"" is used by default.

   On success, this function returns a *strong reference* to a Python
   "bytes" object containing the unescaped string. On failure, this
   function returns "NULL" with an exception set.

   Changed in version 3.9: *unicode* and *recode_encoding* are now
   unused.


PyBytesWriter
*************

The "PyBytesWriter" API can be used to create a Python "bytes" object.

Added in version 3.15.

type PyBytesWriter

   A bytes writer instance.

   The API is **not thread safe**: a writer should only be used by a
   single thread at the same time.

   The instance must be destroyed by "PyBytesWriter_Finish()" on
   success, or "PyBytesWriter_Discard()" on error.


Create, Finish, Discard
=======================

PyBytesWriter *PyBytesWriter_Create(Py_ssize_t size)

   Create a "PyBytesWriter" to write *size* bytes.

   If *size* is greater than zero, allocate *size* bytes, and set the
   writer size to *size*. The caller is responsible to write *size*
   bytes using "PyBytesWriter_GetData()". This function does not
   overallocate.

   On error, set an exception and return "NULL".

   *size* must be positive or zero.

PyObject *PyBytesWriter_Finish(PyBytesWriter *writer)

   Finish a "PyBytesWriter" created by "PyBytesWriter_Create()".

   On success, return a Python "bytes" object. On error, set an
   exception and return "NULL".

   The writer instance is invalid after the call in any case. No API
   can be called on the writer after "PyBytesWriter_Finish()".

PyObject *PyBytesWriter_FinishWithSize(PyBytesWriter *writer, Py_ssize_t size)

   Similar to "PyBytesWriter_Finish()", but resize the writer to
   *size* bytes before creating the "bytes" object.

PyObject *PyBytesWriter_FinishWithPointer(PyBytesWriter *writer, void *buf)

   Similar to "PyBytesWriter_Finish()", but resize the writer using
   *buf* pointer before creating the "bytes" object.

   Set an exception and return "NULL" if *buf* pointer is outside the
   internal buffer bounds.

   Function pseudo-code:

      Py_ssize_t size = (char*)buf - (char*)PyBytesWriter_GetData(writer);
      return PyBytesWriter_FinishWithSize(writer, size);

void PyBytesWriter_Discard(PyBytesWriter *writer)

   Discard a "PyBytesWriter" created by "PyBytesWriter_Create()".

   Do nothing if *writer* is "NULL".

   The writer instance is invalid after the call. No API can be called
   on the writer after "PyBytesWriter_Discard()".


High-level API
==============

int PyBytesWriter_WriteBytes(PyBytesWriter *writer, const void *bytes, Py_ssize_t size)

   Grow the *writer* internal buffer by *size* bytes, write *size*
   bytes of *bytes* at the *writer* end, and add *size* to the
   *writer* size.

   If *size* is equal to "-1", call "strlen(bytes)" to get the string
   length.

   On success, return "0". On error, set an exception and return "-1".

int PyBytesWriter_Format(PyBytesWriter *writer, const char *format, ...)

   Similar to "PyBytes_FromFormat()", but write the output directly at
   the writer end. Grow the writer internal buffer on demand. Then add
   the written size to the writer size.

   On success, return "0". On error, set an exception and return "-1".


Getters
=======

Py_ssize_t PyBytesWriter_GetSize(PyBytesWriter *writer)

   Get the writer size.

   The function does not invalidate pointers returned by
   "PyBytesWriter_GetData()".

   The function cannot fail.

void *PyBytesWriter_GetData(PyBytesWriter *writer)

   Get the writer data: start of the internal buffer.

   The pointer remains valid until a "PyBytesWriter" function other
   than "PyBytesWriter_GetData()" or "PyBytesWriter_GetSize()" is
   called on *writer*.

   The function cannot fail.


Low-level API
=============

int PyBytesWriter_Resize(PyBytesWriter *writer, Py_ssize_t size)

   Resize the writer to *size* bytes. It can be used to enlarge or to
   shrink the writer. This function typically overallocates to achieve
   amortized performance when resizing multiple times.

   Newly allocated bytes are left uninitialized.

   On success, return "0". On error, set an exception and return "-1".

   *size* must be positive or zero.

int PyBytesWriter_Grow(PyBytesWriter *writer, Py_ssize_t grow)

   Resize the writer by adding *grow* bytes to the current writer
   size. This function typically overallocates to achieve amortized
   performance when resizing multiple times.

   Newly allocated bytes are left uninitialized.

   On success, return "0". On error, set an exception and return "-1".

   *size* can be negative to shrink the writer.

void *PyBytesWriter_GrowAndUpdatePointer(PyBytesWriter *writer, Py_ssize_t size, void *buf)

   Similar to "PyBytesWriter_Grow()", but update also the *buf*
   pointer.

   The *buf* pointer is moved if the internal buffer is moved in
   memory. The *buf* relative position within the internal buffer is
   left unchanged.

   On error, set an exception and return "NULL".

   *buf* must not be "NULL".

   Function pseudo-code:

      Py_ssize_t pos = (char*)buf - (char*)PyBytesWriter_GetData(writer);
      if (PyBytesWriter_Grow(writer, size) < 0) {
          return NULL;
      }
      return (char*)PyBytesWriter_GetData(writer) + pos;
