Add bubblebabble

Makefile

@@ -17,6 +17,7 @@ TARGETS += entropy
 TARGETS += freq
 TARGETS += histogram
 TARGETS += printy
+TARGETS += bubblebabble
 
 SCRIPTS += octets
 

README.md

@@ -313,10 +313,35 @@ Reads the first number of each line, and prints a histogram.
     0a ◙ # 1
     41 A ######## 8
     61 a ################ 16
-    $ echo 'aaaaaaaaAAAAAAAAaaaaaaaa' | freq | histogram -d 4
-    0a ◙  1
-    41 A ## 8
-    61 a #### 16
+    $ echo aaaaaabcccc | freq | histogram
+    0a ◙ # 1
+    61 a ###### 6
+    62 b # 1
+    63 c #### 4
+    $ echo aaaaaabcccc | freq | histogram | sort -nk 4
+    0a ◙ # 1
+    62 b # 1
+    63 c #### 4
+    61 a ###### 6
+
+
+## bubblebabble: print bubblebabble digest of input
+
+Prints a [bubblebabble digest](https://web.mit.edu/kenta/www/one/bubblebabble/spec/jrtrjwzi/draft-huima-01.txt)
+of the input.
+
+This is a *digest*, not a *hash*:
+it can be reversed.
+If you write `unbubblebabble` before I do,
+please send it to me :)
+
+    $ printf '' | bubblebabble
+    xexax
+    $ printf 1234567890 | bubblebabble
+    xesef-disof-gytuf-katof-movif-baxux
+    $ printf Pineapple | bubblebabble
+    xigak-nyryk-humil-bosek-sonax
+
 
 
 Example Recipes

bubblebabble.c

@@ -0,0 +1,53 @@
+#include <stdio.h>
+
+/** Compute bubble babble for input buffer.
+ *
+ * The generated output will be of length 6*((inlen/2)+1), including the
+ * trailing NULL.
+ *
+ * Test vectors:
+ *     `' (empty string) `xexax'
+ *     `1234567890'      `xesef-disof-gytuf-katof-movif-baxux'
+ *     `Pineapple'       `xigak-nyryk-humil-bosek-sonax'
+ */
+static char const consonants[] = "bcdfghklmnprstvz";
+static char const vowels[]     = "aeiouy";
+
+int
+main(int argc, char *argv[])
+{
+  int seed = 1;
+
+  putchar('x');
+  while (1) {
+    int c;
+
+    c = getchar();
+    if (EOF == c) {
+      putchar(vowels[seed % 6]);
+      putchar('x');
+      putchar(vowels[seed / 6]);
+      break;
+    }
+
+    putchar(vowels[(((c >> 6) & 3) + seed) % 6]);
+    putchar(consonants[(c >> 2) & 15]);
+    putchar(vowels[((c & 3) + (seed / 6)) % 6]);
+
+    seed = (seed * 5) + (c * 7);
+    c = getchar();
+    seed = (seed + c) % 36;
+
+    if (EOF == c) {
+      break;
+    }
+    putchar(consonants[(c >> 4) & 15]);
+    putchar('-');
+    putchar(consonants[c & 15]);
+  }
+
+  putchar('x');
+  putchar('\n');
+
+  return 0;
+}