"base64" --- Codificações de dados em Base16, Base32, Base64, Base85
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**Código Fonte:** Lib/base64.py

======================================================================

This module provides functions for encoding binary data to printable
ASCII characters and decoding such encodings back to binary data. It
provides encoding and decoding functions for the encodings specified
in **RFC 3548**, which defines the Base16, Base32, and Base64
algorithms, and for the de-facto standard Ascii85 and Base85
encodings.

The **RFC 3548** encodings are suitable for encoding binary data so
that it can safely sent by email, used as parts of URLs, or included
as part of an HTTP POST request.  The encoding algorithm is not the
same as the **uuencode** program.

There are two interfaces provided by this module.  The modern
interface supports encoding *bytes-like objects* to ASCII "bytes", and
decoding *bytes-like objects* or strings containing ASCII to "bytes".
Both base-64 alphabets defined in **RFC 3548** (normal, and URL- and
filesystem-safe) are supported.

A interface legada não oferece suporte a decodificação de strings, mas
fornece funções para codificação e decodificação de e para *objetos
arquivo*. Ele oferece suporte a apenas o alfabeto padrão Base64 e
adiciona novas linhas a cada 76 caracteres conforme **RFC 2045**. Note
que se você estiver procurando por suporte para **RFC 2045** você
provavelmente vai querer conferir o pacote "email".

Alterado na versão 3.3: Strings Unicode exclusivamente ASCII agora são
aceitas pelas funções de decodificação da interface moderna.

Alterado na versão 3.4: Quaisquer *objetos bytes ou similares* agora
são aceitos por todas as funções de codificação e decodificação neste
módulo. Adicionado suporte a ASCII85/Base85.

A interface moderna oferece:

base64.b64encode(s, altchars=None)

   Codifica o *objeto bytes ou similar* *s* usando Base64 e retorna o
   "bytes" codificado.

   Os *altchars* opcionais devem ser um *objeto bytes ou similar* de
   pelo menos comprimento 2 (caracteres adicionais são ignorados) que
   especifica um alfabeto alternativo para os caracteres "+" e "/".
   Isso permite que um aplicativo, por exemplo, gerar strings Base64
   seguras para URL ou sistema de arquivos. O padrão é "None", para o
   qual o alfabeto Base64 padrão é usado.

base64.b64decode(s, altchars=None, validate=False)

   Decodifica o *objeto bytes ou similar* ou string ASCII *s*
   codificada em Base64 e retorna o "bytes" decodificado.

   *Altchars* opcionais devem ser um *objeto bytes ou similar* ou
   string ASCII de pelo menos 2 (caracteres adicionais são ignorados)
   que especifica o alfabeto alternativo usado ao invés do "+" e "/"
   caracteres.

   A "binascii.Error" exception is raised if *s* is incorrectly
   padded.

   If *validate* is "False" (the default), characters that are neither
   in the normal base-64 alphabet nor the alternative alphabet are
   discarded prior to the padding check.  If *validate* is "True",
   these non-alphabet characters in the input result in a
   "binascii.Error".

base64.standard_b64encode(s)

   Encode *bytes-like object* *s* using the standard Base64 alphabet
   and return the encoded "bytes".

base64.standard_b64decode(s)

   Decode *bytes-like object* or ASCII string *s* using the standard
   Base64 alphabet and return the decoded "bytes".

base64.urlsafe_b64encode(s)

   Encode *bytes-like object* *s* using the URL- and filesystem-safe
   alphabet, which substitutes "-" instead of "+" and "_" instead of
   "/" in the standard Base64 alphabet, and return the encoded
   "bytes".  The result can still contain "=".

base64.urlsafe_b64decode(s)

   Decode *bytes-like object* or ASCII string *s* using the URL- and
   filesystem-safe alphabet, which substitutes "-" instead of "+" and
   "_" instead of "/" in the standard Base64 alphabet, and return the
   decoded "bytes".

base64.b32encode(s)

   Encode the *bytes-like object* *s* using Base32 and return the
   encoded "bytes".

base64.b32decode(s, casefold=False, map01=None)

   Decode the Base32 encoded *bytes-like object* or ASCII string *s*
   and return the decoded "bytes".

   *casefold* opcional é uma flag especificando se um alfabeto
   minúsculo é aceitável como entrada. Por razões de segurança, o
   padrão é "False".

   **RFC 3548** allows for optional mapping of the digit 0 (zero) to
   the letter O (oh), and for optional mapping of the digit 1 (one) to
   either the letter I (eye) or letter L (el).  The optional argument
   *map01* when not "None", specifies which letter the digit 1 should
   be mapped to (when *map01* is not "None", the digit 0 is always
   mapped to the letter O).  For security purposes the default is
   "None", so that 0 and 1 are not allowed in the input.

   A "binascii.Error" is raised if *s* is incorrectly padded or if
   there are non-alphabet characters present in the input.

base64.b16encode(s)

   Encode the *bytes-like object* *s* using Base16 and return the
   encoded "bytes".

base64.b16decode(s, casefold=False)

   Decode the Base16 encoded *bytes-like object* or ASCII string *s*
   and return the decoded "bytes".

   *casefold* opcional é uma flag especificando se um alfabeto
   minúsculo é aceitável como entrada. Por razões de segurança, o
   padrão é "False".

   A "binascii.Error" is raised if *s* is incorrectly padded or if
   there are non-alphabet characters present in the input.

base64.a85encode(b, *, foldspaces=False, wrapcol=0, pad=False, adobe=False)

   Encode the *bytes-like object* *b* using Ascii85 and return the
   encoded "bytes".

   *foldspaces* is an optional flag that uses the special short
   sequence 'y' instead of 4 consecutive spaces (ASCII 0x20) as
   supported by 'btoa'. This feature is not supported by the
   "standard" Ascii85 encoding.

   *wrapcol* controls whether the output should have newline ("b'\n'")
   characters added to it. If this is non-zero, each output line will
   be at most this many characters long.

   *pad* controls whether the input is padded to a multiple of 4
   before encoding. Note that the "btoa" implementation always pads.

   *adobe* controls whether the encoded byte sequence is framed with
   "<~" and "~>", which is used by the Adobe implementation.

   Novo na versão 3.4.

base64.a85decode(b, *, foldspaces=False, adobe=False, ignorechars=b' \t\n\r\v')

   Decode the Ascii85 encoded *bytes-like object* or ASCII string *b*
   and return the decoded "bytes".

   *foldspaces* is a flag that specifies whether the 'y' short
   sequence should be accepted as shorthand for 4 consecutive spaces
   (ASCII 0x20). This feature is not supported by the "standard"
   Ascii85 encoding.

   *adobe* controla se a entrada está no formato Adobe Ascii85  (ou
   seja, cercada por <~ e ~>).

   *ignorechars* should be a *bytes-like object* or ASCII string
   containing characters to ignore from the input. This should only
   contain whitespace characters, and by default contains all
   whitespace characters in ASCII.

   Novo na versão 3.4.

base64.b85encode(b, pad=False)

   Encode the *bytes-like object* *b* using base85 (as used in e.g.
   git-style binary diffs) and return the encoded "bytes".

   If *pad* is true, the input is padded with "b'\0'" so its length is
   a multiple of 4 bytes before encoding.

   Novo na versão 3.4.

base64.b85decode(b)

   Decode the base85-encoded *bytes-like object* or ASCII string *b*
   and return the decoded "bytes".  Padding is implicitly removed, if
   necessary.

   Novo na versão 3.4.

A interface legada:

base64.decode(input, output)

   Decode the contents of the binary *input* file and write the
   resulting binary data to the *output* file. *input* and *output*
   must be *file objects*. *input* will be read until
   "input.readline()" returns an empty bytes object.

base64.decodebytes(s)

   Decode the *bytes-like object* *s*, which must contain one or more
   lines of base64 encoded data, and return the decoded "bytes".

   Novo na versão 3.1.

base64.decodestring(s)

   Deprecated alias of "decodebytes()".

   Obsoleto desde a versão 3.1.

base64.encode(input, output)

   Encode the contents of the binary *input* file and write the
   resulting base64 encoded data to the *output* file. *input* and
   *output* must be *file objects*. *input* will be read until
   "input.read()" returns an empty bytes object. "encode()" inserts a
   newline character ("b'\n'") after every 76 bytes of the output, as
   well as ensuring that the output always ends with a newline, as per
   **RFC 2045** (MIME).

base64.encodebytes(s)

   Encode the *bytes-like object* *s*, which can contain arbitrary
   binary data, and return "bytes" containing the base64-encoded data,
   with newlines ("b'\n'") inserted after every 76 bytes of output,
   and ensuring that there is a trailing newline, as per **RFC 2045**
   (MIME).

   Novo na versão 3.1.

base64.encodestring(s)

   Deprecated alias of "encodebytes()".

   Obsoleto desde a versão 3.1.

Um exemplo de uso do módulo:

>>> import base64
>>> encoded = base64.b64encode(b'data to be encoded')
>>> encoded
b'ZGF0YSB0byBiZSBlbmNvZGVk'
>>> data = base64.b64decode(encoded)
>>> data
b'data to be encoded'

Ver também:

  Módulo "binascii"
     Módulo de suporte contendo conversões ASCII para binário e
     binário para ASCII.

  **RFC 1521** - MIME (Multipurpose Internet Mail Extensions) Part
  One: Mechanisms for Specifying and Describing the Format of Internet
  Message Bodies
     Section 5.2, "Base64 Content-Transfer-Encoding," provides the
     definition of the base64 encoding.
