Data commit

Task/Variable-length-quantity/Icon/variable-length-quantity.icon

@@ -0,0 +1,30 @@
+procedure main()
+every i := 2097152 | 2097151 | 1 | 127 | 128 | 589723405834 | 165 | 256 do
+   write(image(i)," = ",string2hex(v := uint2vlq(i))," = ",vlq2uint(v))
+end
+
+procedure vlq2uint(s)    #: decode a variable length quantity
+   if *s > 0 then {
+      i := 0
+      s ? while h := ord(move(1)) do {
+         if (pos(0) & h > 128) | (not pos(0) & h < 128) then fail
+         i := 128 * i + h % 128
+         }
+      return i
+      }
+end
+
+procedure uint2vlq(i,c)  #: encode a whole number as a variable length quantity
+   if "integer" == type(-1 < i) then
+      return if i = 0 then
+         char((/c := 0)) | ""
+      else
+         uint2vlq(i/128,1) || char((i % 128) + ((/c := 0) | 128) )
+end
+
+procedure string2hex(s)  #: convert a string to hex
+   h := ""
+   every i := ord(!s) do
+      h ||:= "0123456789abcdef"[i/16+1] || "0123456789abcdef"[i%16+1]
+   return h
+end