bash/b64: encode arbitrary contents in base 64

bash/b64

@@ -0,0 +1,29 @@
+b64_encode() {
+  local idx=0 numerics table_idxs table_idx encoded
+  local table=( {A..Z} {a..z} {0..9} + / )
+
+  for (( ; idx < ${#1}; idx+=3 )); do
+    read -ra numerics < <(
+      printf '%d %d %d\n' "'${1:idx:1}" "'${1:idx+1:1}" "'${1:idx+2:1}"
+    )
+
+    (( table_idxs[0] = numerics[0] >> 2 ))
+    (( table_idxs[1] = (( (numerics[0] & 0x03) << 6) | (numerics[1] & 0xF0) >> 2) >> 2 ))
+    (( table_idxs[2] = (( (numerics[1] & 0x0F) << 4) | (numerics[2] & 0xC0) >> 4) >> 2 ))
+    (( table_idxs[3] = numerics[2] & 0x3F ))
+
+    for table_idx in "${table_idxs[@]}"; do
+      encoded+=${table[$table_idx]}
+    done
+  done
+
+  if (( ${#1} % 3 == 1 )); then
+    encoded=${encoded::-2}==
+  elif (( ${#1} % 3 == 2 )); then
+    encoded=${encoded::-1}=
+  fi
+
+  prints %s "$encoded"
+}
+
+b64_encode "$1"