mirror of https://github.com/python/cpython
203 lines
9.0 KiB
ReStructuredText
203 lines
9.0 KiB
ReStructuredText
.. highlightlang:: c
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.. _bytesobjects:
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Bytes Objects
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-------------
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These functions raise :exc:`TypeError` when expecting a bytes parameter and are
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called with a non-bytes parameter.
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.. index:: object: bytes
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.. c:type:: PyBytesObject
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This subtype of :c:type:`PyObject` represents a Python bytes object.
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.. c:var:: PyTypeObject PyBytes_Type
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This instance of :c:type:`PyTypeObject` represents the Python bytes type; it
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is the same object as :class:`bytes` in the Python layer.
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.. c:function:: int PyBytes_Check(PyObject *o)
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Return true if the object *o* is a bytes object or an instance of a subtype
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of the bytes type.
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.. c:function:: int PyBytes_CheckExact(PyObject *o)
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Return true if the object *o* is a bytes object, but not an instance of a
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subtype of the bytes type.
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.. c:function:: PyObject* PyBytes_FromString(const char *v)
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Return a new bytes object with a copy of the string *v* as value on success,
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and *NULL* on failure. The parameter *v* must not be *NULL*; it will not be
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checked.
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.. c:function:: PyObject* PyBytes_FromStringAndSize(const char *v, Py_ssize_t len)
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Return a new bytes object with a copy of the string *v* as value and length
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*len* on success, and *NULL* on failure. If *v* is *NULL*, the contents of
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the bytes object are uninitialized.
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.. c:function:: PyObject* PyBytes_FromFormat(const char *format, ...)
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Take a C :c:func:`printf`\ -style *format* string and a variable number of
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arguments, calculate the size of the resulting Python bytes object and return
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a bytes object with the values formatted into it. The variable arguments
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must be C types and must correspond exactly to the format characters in the
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*format* string. The following format characters are allowed:
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.. % XXX: This should be exactly the same as the table in PyErr_Format.
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.. % One should just refer to the other.
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.. % XXX: The descriptions for %zd and %zu are wrong, but the truth is complicated
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.. % because not all compilers support the %z width modifier -- we fake it
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.. % when necessary via interpolating PY_FORMAT_SIZE_T.
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.. tabularcolumns:: |l|l|L|
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+-------------------+---------------+--------------------------------+
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| Format Characters | Type | Comment |
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+===================+===============+================================+
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| :attr:`%%` | *n/a* | The literal % character. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%c` | int | A single byte, |
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| | | represented as a C int. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%d` | int | Exactly equivalent to |
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| | | ``printf("%d")``. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%u` | unsigned int | Exactly equivalent to |
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| | | ``printf("%u")``. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%ld` | long | Exactly equivalent to |
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| | | ``printf("%ld")``. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%lu` | unsigned long | Exactly equivalent to |
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| | | ``printf("%lu")``. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%zd` | Py_ssize_t | Exactly equivalent to |
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| | | ``printf("%zd")``. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%zu` | size_t | Exactly equivalent to |
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| | | ``printf("%zu")``. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%i` | int | Exactly equivalent to |
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| | | ``printf("%i")``. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%x` | int | Exactly equivalent to |
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| | | ``printf("%x")``. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%s` | char\* | A null-terminated C character |
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| | | array. |
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+-------------------+---------------+--------------------------------+
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| :attr:`%p` | void\* | The hex representation of a C |
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| | | pointer. Mostly equivalent to |
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| | | ``printf("%p")`` except that |
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| | | it is guaranteed to start with |
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| | | the literal ``0x`` regardless |
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| | | of what the platform's |
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| | | ``printf`` yields. |
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+-------------------+---------------+--------------------------------+
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An unrecognized format character causes all the rest of the format string to be
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copied as-is to the result object, and any extra arguments discarded.
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.. c:function:: PyObject* PyBytes_FromFormatV(const char *format, va_list vargs)
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Identical to :c:func:`PyBytes_FromFormat` except that it takes exactly two
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arguments.
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.. c:function:: PyObject* PyBytes_FromObject(PyObject *o)
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Return the bytes representation of object *o* that implements the buffer
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protocol.
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.. c:function:: Py_ssize_t PyBytes_Size(PyObject *o)
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Return the length of the bytes in bytes object *o*.
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.. c:function:: Py_ssize_t PyBytes_GET_SIZE(PyObject *o)
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Macro form of :c:func:`PyBytes_Size` but without error checking.
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.. c:function:: char* PyBytes_AsString(PyObject *o)
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Return a pointer to the contents of *o*. The pointer
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refers to the internal buffer of *o*, which consists of ``len(o) + 1``
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bytes. The last byte in the buffer is always null, regardless of
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whether there are any other null bytes. The data must not be
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modified in any way, unless the object was just created using
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``PyBytes_FromStringAndSize(NULL, size)``. It must not be deallocated. If
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*o* is not a bytes object at all, :c:func:`PyBytes_AsString` returns *NULL*
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and raises :exc:`TypeError`.
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.. c:function:: char* PyBytes_AS_STRING(PyObject *string)
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Macro form of :c:func:`PyBytes_AsString` but without error checking.
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.. c:function:: int PyBytes_AsStringAndSize(PyObject *obj, char **buffer, Py_ssize_t *length)
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Return the null-terminated contents of the object *obj*
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through the output variables *buffer* and *length*.
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If *length* is *NULL*, the bytes object
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may not contain embedded null bytes;
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if it does, the function returns ``-1`` and a :exc:`ValueError` is raised.
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The buffer refers to an internal buffer of *obj*, which includes an
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additional null byte at the end (not counted in *length*). The data
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must not be modified in any way, unless the object was just created using
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``PyBytes_FromStringAndSize(NULL, size)``. It must not be deallocated. If
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*obj* is not a bytes object at all, :c:func:`PyBytes_AsStringAndSize`
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returns ``-1`` and raises :exc:`TypeError`.
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.. versionchanged:: 3.5
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Previously, :exc:`TypeError` was raised when embedded null bytes were
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encountered in the bytes object.
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.. c:function:: void PyBytes_Concat(PyObject **bytes, PyObject *newpart)
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Create a new bytes object in *\*bytes* containing the contents of *newpart*
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appended to *bytes*; the caller will own the new reference. The reference to
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the old value of *bytes* will be stolen. If the new object cannot be
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created, the old reference to *bytes* will still be discarded and the value
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of *\*bytes* will be set to *NULL*; the appropriate exception will be set.
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.. c:function:: void PyBytes_ConcatAndDel(PyObject **bytes, PyObject *newpart)
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Create a new bytes object in *\*bytes* containing the contents of *newpart*
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appended to *bytes*. This version decrements the reference count of
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*newpart*.
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.. c:function:: int _PyBytes_Resize(PyObject **bytes, Py_ssize_t newsize)
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A way to resize a bytes object even though it is "immutable". Only use this
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to build up a brand new bytes object; don't use this if the bytes may already
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be known in other parts of the code. It is an error to call this function if
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the refcount on the input bytes object is not one. Pass the address of an
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existing bytes object as an lvalue (it may be written into), and the new size
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desired. On success, *\*bytes* holds the resized bytes object and ``0`` is
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returned; the address in *\*bytes* may differ from its input value. If the
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reallocation fails, the original bytes object at *\*bytes* is deallocated,
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*\*bytes* is set to *NULL*, a memory exception is set, and ``-1`` is
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returned.
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