HERE'S AN IMPLEMENTATION OF A BASE64 ENCODER, TO UNDERSTAND HOW THE ENCODING ALGORITHM WORKS, HERE I DESCRIBE STEP BY STEP HOW TO MANUALLY ENCODE STRINGS FOR EXAMPLE IF YOU WANT TO CONVERT "ciao" INTO BASE64:

• FIRST, YOU NEED TO SPLIT THE STRING LETTER BY LETTER:

  • c
  • i
  • a
  • o

• NEXT YOU NEED TO CONVERT EACH LETTER TO BINARY, SO:

  • 01100011
  • 01101001
  • 01100001
  • 01101111

• CONCATENATE ALL THE BINARY VALUES TOGETHER: 01100011011010010110000101101111

• THEN, DIVIDE THE RESULTING STRING INTO GROUPS OF 6 BITS:

  • 011000
  • 110110
  • 100101
  • 100001
  • 011011
  • 110000 <- HERE APPEND 4 ZEROS TO CREATE THE SIX-BIT STRING

• NOW YOU HAVE TO CONVERT EACH GROUP FROM BINARY TO DECIMAL, SO:

  • 24
  • 54
  • 37
  • 33
  • 27
  • 48

• THOSE INTEGER NUMBERS ARE CALLED BASE64 INDICES, EACH INDEX CORRESPONDS TO A LETTER. FOR THE COMPLETE LIST SEE "base64_enc.c". AFTER MATCHING INDEXES, CONVERT THEM TO LETTERS:

  • Y
  • 2
  • l
  • h
  • b
  • w

• TO FINISH CONCATENATE ALL LETTERS TO GET THE BASE64 STRING "Y2lhbw"

THE PROGRAM WORKS WITH BIT SHIFT, BITWISE OR AND BITWISE AND.