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Snippet: base64 decode — Parallax Forums

Snippet: base64 decode

ke4pjwke4pjw Posts: 842
edited 2023-01-16 04:37 in PASM2/Spin2 (P2)
{{
** Base64 decoding/encoding functions v0.1
** by Robert Quattlebaum <darco@deepdarc.com>
** PUBLIC DOMAIN
** 2008-04-18
** Converted to Spin2 by Terry E. Trapp, KE4PJW
** 2023-01-15

}}
PUB inplaceDecode(in_ptr) : rt | out_ptr,i,in,char,size
{{ Decodes a base64 encoded string in-place. Returns the size of the decoded data. }}
  out_ptr:=in_ptr
  size:=0
  repeat
    ifnot BYTE[in_ptr]
      quit
    repeat i from 0 to 3
      char:=BYTE[in_ptr++]
      'repeat while (char:=BYTE[in_ptr++])==" "
      ifnot char
        BYTE[@in][i]:="="
        in_ptr--
        quit
      else
        BYTE[@in][i]:=char

    i:=base64_decode_4(@in,out_ptr)
    out_ptr+=i
    size+=i
    debug(udec(size))
  while char AND i==3
  BYTE[out_ptr]:=0
  debug(udec(size))
  return (size)

pri base64_tlu(char) : rt | i
  case char
    "A".."Z": return (char-"A")
    "a".."z": return (char-"a"+26)
    "0".."9": return (char-"0"+52)
    "+": return (62)
    "/": return (63)
    other: return (0)
PUB base64_decode_4(inptr,outptr) : rt | retVal,i,out
  out:=0
  retVal:=3
  repeat i from 0 to 3
    debug(udec(i))
    if(BYTE[inptr][i]=="=")
      case i
        3: retVal:=2
        2: retVal:=1
        1: retVal:=0
        0: retVal:=0
      quit
    out|= base64_tlu(BYTE[inptr][i])<<((3-i)*6)

  if retVal
    repeat i from 0 to retVal-1
      BYTE[outptr][i]:=BYTE[@out][2-i]
  return (retVal)
CON
{{
┌──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│                                                   TERMS OF USE: MIT License                                                  │
├──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
│Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation    │
│files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy,    │
│modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software│
│is furnished to do so, subject to the following conditions:                                                                   │
│                                                                                                                              │
│The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.│
│                                                                                                                              │
│THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE          │
│WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR         │
│COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,   │
│ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                         │
└──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
}}
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