base64 implement in awk & hexdump

base64.awk

#!/usr/bin/awk -f
# from https://sites.google.com/site/dannychouinard/Home/unix-linux-trinkets/little-utilities/base64-and-base85-encoding-awk-scripts
#
# compatible with busybox:
#   no od, awk not print \0

function encode64() {
  while( "hexdump -e ' \"%07.7_ax \" 16/1 \"%02x \" \"\n\"'" | getline ) {
    for(c=9; c<=length($0); c++) {
      d=index("0123456789abcdef",substr($0,c,1));
      if(d--) {
        for(b=1; b<=4; b++ ) {
          o=o*2+int(d/8); d=(d*2)%16;
          if(++obc==6) {
            printf substr(b64,o+1,1);
            if(++rc>75) { printf("\n"); rc=0; }
            obc=0; o=0;
          }
        }
      }
    }
  }
  if(obc) {
    while(obc++<6) { o=o*2; }
    printf "%c",substr(b64,o+1,1);
  }
  print "==";
}
function putchar(c) {
  if(c==0)
   system("echo -ne \"\\00\"")
  else
   printf "%c",o;
}
function decode64() {
  while( getline < "/dev/stdin" ) {
    for(i=1;i<=length($0);i++) {
      c=index(b64,substr($0,i,1));
      if(c--) {
        for(b=0;b<6;b++) {
          o=o*2+int(c/32); c=(c*2)%64;
         #printf "\n[%s]", o > "/dev/stderr";
          if(++obc==8) { putchar(o); obc=0; o=0;  }
        }
      }
    }
  }
}
BEGIN {
  b64="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
  if(ARGV[1]=="d") { decode64(); exit; }
  encode64();
}