just a base64 encoder written for fun (#380)

misc/base64_encode.nu

@@ -0,0 +1,63 @@
+let dictionary = [
+  'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S',
+  'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l',
+  'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4',
+  '5', '6', '7', '8', '9', '+', '/'
+]
+
+let padding_char = '='
+
+def base64_encode [input: string] {
+  mut result = ""
+  mut counter = 0
+  mut left_carry = 0
+
+  if ($input | is-empty) {
+    error make {msg: "input is empty"}
+  }
+
+  for char in ($input | split chars) {
+    let char_bin = ($char | into binary)
+    let char_int = ($char_bin | into int)
+
+    if $counter mod 3 == 0 {
+      let index = ($char_int bit-shr 2)
+      $result += ($dictionary | get $index)
+      $left_carry = ($char_int bit-and 0x3)
+    } else if $counter mod 3 == 1 {
+      let index = (($left_carry bit-shl 4) bit-or ($char_int bit-shr 4))
+      $result += ($dictionary | get $index)
+      $left_carry = ($char_int bit-and 0xF)
+    } else if $counter mod 3 == 2 {
+      mut index = (($left_carry bit-shl 2) bit-or ($char_int bit-shr 6))
+      $result += ($dictionary | get $index)
+      $index = ($char_int bit-and 0x3F)
+      $result += ($dictionary | get $index)
+    }
+
+    $counter += 1
+  }
+
+  if $counter != 0 {
+    if $counter mod 3 == 1 {
+      $result += ($dictionary | get ($left_carry bit-shl 4))
+      $result += $padding_char
+      $result += $padding_char
+    } else if $counter mod 3 == 2 {
+      $result += ($dictionary | get ($left_carry bit-shl 2))
+      $result += $padding_char
+    }
+  }
+
+  $result
+}
+
+# Test Cases
+# base64_encode "nushell", "bnVzaGVsbA=="
+# base64_encode "hello", "aGVsbG8="
+# base64_encode "world", "d29ybGQ="
+# base64_encode "now is the time for all good mean to come to the aid of their country", "bm93IGlzIHRoZSB0aW1lIGZvciBhbGwgZ29vZCBtZWFuIHRvIGNvbWUgdG8gdGhlIGFpZCBvZiB0aGVpciBjb3VudHJ5
+# base64_encode "crab", "Y3JhYg=="
+# base64_encode "the brown fox jump over the lazy dog!"), "dGhlIGJyb3duIGZveCBqdW1wIG92ZXIgdGhlIGxhenkgZG9nIQ=="
+# base64_encode "", error
+# base64_encode "a", "YQ=="