Not-See encoder (encode any character to blank string)

not-see.js

/* 
Blank character encoder/decoder
A tool to anti-censorship at Bilibili

Original author: https://not-see.pages.dev/ 
*/

const ALLOWED_BLANKS = [
  "\u0020",
  "\u3000",
  "\u205F",
  "\u2000",
  "\u2001",
  "\u2002",
  "\u2003",
  "\u2004",
  "\u2005",
  "\u2006",
  "\u2007",
  "\u2008",
  "\u2009",
  "\u200A",
  "\u202F",
  "\n",
];

const BLANKS_MAP = Object.fromEntries(
  ALLOWED_BLANKS.map((v, i) => [v.charCodeAt(0), i])
);

/**
 * @param {ArrayLike<number>} target
 * @returns {String}
 */
function encode(target) {
  return Array.from(target)
    .map((v) => ALLOWED_BLANKS[v >> 4] + ALLOWED_BLANKS[v & 0xf])
    .join("");
}

/**
 * @param {String} target
 * @returns {Uint8Array}
 */
function decode(target) {
  return new Uint8Array(
    Array.from(
      { length: target.length >> 1 },
      (_, k) =>
        (BLANKS_MAP[target.charCodeAt(k * 2)] << 4) +
        BLANKS_MAP[target.charCodeAt(k * 2 + 1)]
    )
  );
}

not_see.py

"""
Blank character encoder/decoder
A tool to anti-censorship at Bilibili

Credits:
    Original author: https://not-see.pages.dev/

Transplanted to Python by: mnixry@GitHub
"""


class NotSeeUtils:
    ALLOWED_BLANKS = [
        "\u0020",
        "\u3000",
        "\u205F",
        "\u2000",
        "\u2001",
        "\u2002",
        "\u2003",
        "\u2004",
        "\u2005",
        "\u2006",
        "\u2007",
        "\u2008",
        "\u2009",
        "\u200A",
        "\u202F",
        "\n",
    ]

    _BLANKS_MAP = {ord(s): i for i, s in enumerate(ALLOWED_BLANKS)}

    @classmethod
    def encode(cls, target: bytes) -> str:
        """
        Original code:

        ```javascript
        const encoded = Array.from(new TextEncoder().encode(src))
            .map((v) => `${spaces[v >> 4]}${spaces[v & 0xf]}`)
            .join("");
        ```
        """
        return "".join(
            map(
                lambda v: (cls.ALLOWED_BLANKS[v >> 4] + cls.ALLOWED_BLANKS[v & 0xF]),
                target,
            )
        )

    @classmethod
    def decode(cls, target: str) -> bytes:
        """
        Original code:

        ```javascript
        const decoded = new TextDecoder().decode(
            new Uint8Array(
            Array.from({ length: src.length >> 1 }, (_, k) => {
                return (
                (reverted[src.charCodeAt(k * 2)] << 4) +
                reverted[src.charCodeAt(k * 2 + 1)]
                );
            })
            )
        );
        ```

        """
        return bytes(
            (
                (cls._BLANKS_MAP[ord(target[i * 2])] << 4)
                + cls._BLANKS_MAP[ord(target[i * 2 + 1])]
            )
            for i in range(len(target) >> 1)
        )