Doc/c-api/bytes.rst
.. highlight:: c
.. _bytesobjects:
These functions raise :exc:TypeError when expecting a bytes parameter and
called with a non-bytes parameter.
.. index:: pair: object; bytes
.. c:type:: PyBytesObject
This subtype of :c:type:PyObject represents a Python bytes object.
.. c:var:: PyTypeObject PyBytes_Type
This instance of :c:type:PyTypeObject represents the Python bytes type; it
is the same object as :class:bytes in the Python layer.
.. c:function:: 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.
.. c:function:: 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.
.. c:function:: PyObject* PyBytes_FromString(const char *v)
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.
.. c:function:: PyObject* PyBytes_FromStringAndSize(const char *v, Py_ssize_t len)
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.
.. deprecated:: 3.15
PyBytes_FromStringAndSize(NULL, len) is :term:soft deprecated,
use the :c:type:PyBytesWriter API instead.
.. c:function:: PyObject* PyBytes_FromFormat(const char *format, ...)
Take a C :c:func: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:
.. % XXX: This should be exactly the same as the table in PyErr_Format. .. % One should just refer to the other.
.. tabularcolumns:: |l|l|L|
+-------------------+---------------+--------------------------------+
| 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 | :c:type:\ | Equivalent to | | | Py_ssize_t | 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.
.. c:function:: PyObject* PyBytes_FromFormatV(const char *format, va_list vargs)
Identical to :c:func:PyBytes_FromFormat except that it takes exactly two
arguments.
.. c:function:: PyObject* PyBytes_FromObject(PyObject *o)
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.
.. c:function:: Py_ssize_t PyBytes_Size(PyObject *o)
Return the length of the bytes in bytes object o.
.. c:function:: Py_ssize_t PyBytes_GET_SIZE(PyObject *o)
Similar to :c:func:PyBytes_Size, but without error checking.
.. c:function:: char* PyBytes_AsString(PyObject *o)
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, :c:func:PyBytes_AsString returns NULL
and raises :exc:TypeError.
.. c:function:: char* PyBytes_AS_STRING(PyObject *string)
Similar to :c:func:PyBytes_AsString, but without error checking.
.. c:function:: int PyBytes_AsStringAndSize(PyObject *obj, char **buffer, Py_ssize_t *length)
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 :exc: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, :c:func:PyBytes_AsStringAndSize
returns -1 and raises :exc:TypeError.
.. versionchanged:: 3.5
Previously, :exc:TypeError was raised when embedded null bytes were
encountered in the bytes object.
.. c:function:: void PyBytes_Concat(PyObject **bytes, PyObject *newpart)
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 discarded and the value
of *bytes will be set to NULL; 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.
.. c:function:: void PyBytes_ConcatAndDel(PyObject **bytes, PyObject *newpart)
Create a new bytes object in *bytes containing the contents of newpart
appended to bytes. This version releases the :term: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.
.. c:function:: PyObject* PyBytes_Join(PyObject *sep, PyObject *iterable)
Similar to sep.join(iterable) in Python.
sep must be Python :class:bytes object.
(Note that :c:func:PyUnicode_Join accepts NULL separator and treats
it as a space, whereas :c:func:PyBytes_Join doesn't accept NULL
separator.)
iterable must be an iterable object yielding objects that implement the
:ref:buffer protocol <bufferobjects>.
On success, return a new :class:bytes object.
On error, set an exception and return NULL.
.. versionadded:: 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.
.. c:function:: int _PyBytes_Resize(PyObject **bytes, Py_ssize_t newsize)
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, :exc:MemoryError is set, and -1 is
returned.
.. deprecated:: 3.15
The function is :term:soft deprecated,
use the :c:type:PyBytesWriter API instead.
.. c:function:: PyObject *PyBytes_Repr(PyObject *bytes, int smartquotes)
Get the string representation of bytes. This function is currently used to
implement :meth:!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 :term:strong reference to a
:class:str object containing the representation. On failure, this
returns NULL with an exception set.
.. c:function:: PyObject *PyBytes_DecodeEscape(const char *s, Py_ssize_t len, const char *errors, Py_ssize_t unicode, const char *recode_encoding)
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 :term:strong reference to a Python
:class:bytes object containing the unescaped string. On failure, this
function returns NULL with an exception set.
.. versionchanged:: 3.9 unicode and recode_encoding are now unused.
.. _pybyteswriter:
The :c:type:PyBytesWriter API can be used to create a Python :class:bytes
object.
.. versionadded:: 3.15
.. c: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 :c:func:PyBytesWriter_Finish on
success, or :c:func:PyBytesWriter_Discard on error.
Create, Finish, Discard ^^^^^^^^^^^^^^^^^^^^^^^
.. c:function:: PyBytesWriter* PyBytesWriter_Create(Py_ssize_t size)
Create a :c:type: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 :c:func:PyBytesWriter_GetData.
This function does not overallocate.
On error, set an exception and return NULL.
size must be positive or zero.
.. c:function:: PyObject* PyBytesWriter_Finish(PyBytesWriter *writer)
Finish a :c:type:PyBytesWriter created by
:c:func:PyBytesWriter_Create.
On success, return a Python :class: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 :c:func:PyBytesWriter_Finish.
.. c:function:: PyObject* PyBytesWriter_FinishWithSize(PyBytesWriter *writer, Py_ssize_t size)
Similar to :c:func:PyBytesWriter_Finish, but resize the writer
to size bytes before creating the :class:bytes object.
.. c:function:: PyObject* PyBytesWriter_FinishWithPointer(PyBytesWriter *writer, void *buf)
Similar to :c:func:PyBytesWriter_Finish, but resize the writer
using buf pointer before creating the :class: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);
.. c:function:: void PyBytesWriter_Discard(PyBytesWriter *writer)
Discard a :c:type:PyBytesWriter created by :c:func: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 :c:func:PyBytesWriter_Discard.
High-level API ^^^^^^^^^^^^^^
.. c:function:: 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.
.. c:function:: int PyBytesWriter_Format(PyBytesWriter *writer, const char *format, ...)
Similar to :c:func: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 ^^^^^^^
.. c:function:: Py_ssize_t PyBytesWriter_GetSize(PyBytesWriter *writer)
Get the writer size.
The function cannot fail.
.. c:function:: void* PyBytesWriter_GetData(PyBytesWriter *writer)
Get the writer data: start of the internal buffer.
The pointer is valid until :c:func:PyBytesWriter_Finish or
:c:func:PyBytesWriter_Discard is called on writer.
The function cannot fail.
Low-level API ^^^^^^^^^^^^^
.. c:function:: 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.
.. c:function:: 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.
.. c:function:: void* PyBytesWriter_GrowAndUpdatePointer(PyBytesWriter *writer, Py_ssize_t size, void *buf)
Similar to :c:func: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;