# 字节对象

当期望带一个字节串形参但却带一个非字节串形参被调用时，这些函数会引发 `TypeError`。

`PyBytesObject`

  这种 `PyObject` 的子类型表示一个 Python 字节对象。

PyTypeObject `PyBytes_Type`

  `PyTypeObject` 的实例代表一个 Python 字节类型，在 Python 层面它与 `bytes` 是相同的对象。

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.

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.

PyObject* `PyBytes_FromString`(const char *v)

  返回一个新字节对象，成功时返回字符串*v*的副本作为值，失败时返回*NULL*。形参*v*不能为*NULL*;它不会被检查。

PyObject* `PyBytes_FromStringAndSize`(const char *v, Py_ssize_t len)

  返回一个新字节对象，成功时将字符串*v*的副本作为值和长度*len*，失败时返回*NULL*。如果*v*为*NULL*，则字节对象的内容未初始化。

PyObject* `PyBytes_FromFormat`(const char *format, ...)

  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:

  格式字符 | 类型 | 注释
  --- | --- | ---
  `%%` | 不适用 | 文字%字符。
  `%c` | int | 一个字节，被表示为一个 C 语言的整型
  `%d` | int | Exactly equivalent to `printf("%d")`.
  `%u` | 无符号整型 | Exactly equivalent to `printf("%u")`.
  `%ld` | 长整型 | Exactly equivalent to `printf("%ld")`.
  `%lu` | 无符号长整型 | Exactly equivalent to `printf("%lu")`.
  `%zd` | Py_ssize_t | Exactly equivalent to `printf("%zd")`.
  `%zu` | size_t | Exactly equivalent to `printf("%zu")`.
  `%i` | int | Exactly equivalent to `printf("%i")`.
  `%x` | int | Exactly equivalent to `printf("%x")`.
  `%s` | char* | A null-terminated C character array.
  `%p` | 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.

PyObject* `PyBytes_FromFormatV`(const char *format, va_list vargs)

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

PyObject* `PyBytes_FromObject`(PyObject *o)

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

Py_ssize_t `PyBytes_Size`(PyObject *o)

  Return the length of the bytes in bytes object o.

Py_ssize_t `PyBytes_GET_SIZE`(PyObject *o)

  Macro form of `PyBytes_Size()` but without error checking.

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, `PyBytes_AsString()` returns NULL and raises `TypeError`.

char* `PyBytes_AS_STRING`(PyObject *string)

  Macro form of `PyBytes_AsString()` but without error checking.

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.

  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`.

  在 3.5 版更改: Previously, `TypeError` was raised when embedded null bytes were encountered in the bytes object.

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.

void `PyBytes_ConcatAndDel`(PyObject **bytes, PyObject *newpart)

  Create a new bytes object in *bytes containing the contents of newpart appended to bytes. This version decrements the reference count of newpart.

int `_PyBytes_Resize`(PyObject **bytes, Py_ssize_t newsize)

  A way to resize a bytes object even though it is “immutable”. Only use this to build up a brand new bytes object; don’t use this if the bytes may already be known in other parts of the code. It is an error to call this function if the refcount on the input bytes object is not one. 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.