Function _b32encode

Lib/base64.py:163–196

(alphabet, s)

_b32rev = {}

def _b32encode(alphabet, s):
    # Delay the initialization of the table to not waste memory
    # if the function is never called
    if alphabet not in _b32tab2:
        b32tab = [bytes((i,)) for i in alphabet]
        _b32tab2[alphabet] = [a + b for a in b32tab for b in b32tab]
        b32tab = None

    if not isinstance(s, bytes_types):
        s = memoryview(s).tobytes()
    leftover = len(s) % 5
    # Pad the last quantum with zero bits if necessary
    if leftover:
        s = s + b'\0' * (5 - leftover)  # Don't use += !
    encoded = bytearray()
    from_bytes = int.from_bytes
    b32tab2 = _b32tab2[alphabet]
    for i in range(0, len(s), 5):
        c = from_bytes(s[i: i + 5])              # big endian
        encoded += (b32tab2[c >> 30] +           # bits 1 - 10
                    b32tab2[(c >> 20) & 0x3ff] + # bits 11 - 20
                    b32tab2[(c >> 10) & 0x3ff] + # bits 21 - 30
                    b32tab2[c & 0x3ff]           # bits 31 - 40
                   )
    # Adjust for any leftover partial quanta
    if leftover == 1:
        encoded[-6:] = b'======'
    elif leftover == 2:
        encoded[-4:] = b'===='
    elif leftover == 3:
        encoded[-3:] = b'==='
    elif leftover == 4:
        encoded[-1:] = b'='
    return bytes(encoded)

def _b32decode(alphabet, s, casefold=False, map01=None):
    # Delay the initialization of the table to not waste memory