subbuf.patch

diff --git a/src/core/Buf.pm6 b/src/core/Buf.pm6
index bd500edbc..07cb09b4f 100644
--- a/src/core/Buf.pm6
+++ b/src/core/Buf.pm6
@@ -170,11 +170,78 @@ my role Blob[::T = uint8] does Positional[T] does Stringy is repr('VMArray') is
         self.^name ~ '.new(' ~ self.join(',') ~ ')';
     }
 
-    method subbuf(Blob:D: $from, $length?) {
+    proto method subbuf(|) {*}
+    multi method subbuf(Blob:D: $from) {
+        nqp::stmts(
+          (my int $elems = nqp::elems(self)),
+            nqp::stmts(
+              (my int $pos),
+              (my int $todo),
+                  ($pos = nqp::istype($from, Callable) ?? $from($elems) !! $from.Int),
+                  ($todo = $elems - $pos),
+              nqp::if(
+                nqp::islt_i($pos, 0),
+                X::OutOfRange.new(
+                  :what('From argument to subbuf'), :got($from.gist), :range("0..$elems"),
+                  :comment("use *-{abs $pos} if you want to index relative to the end"),
+                ).fail,
+                nqp::if(
+                  nqp::isgt_i($pos, $elems),
+                  X::OutOfRange.new(
+                    :what('From argument to subbuf'), :got($from.gist), :range("0..$elems"),
+                  ).fail,
+                  nqp::if(
+                    nqp::isle_i($todo, 0),
+                    nqp::create(self), # we want zero elements; return empty Blob
+                    nqp::stmts(
+                      (my $subbuf := nqp::create(self)),
+                      nqp::setelems($subbuf, $todo),
+                      (my int $i = -1),
+                      --$pos,
+                      nqp::while(
+                        nqp::islt_i(++$i,$todo),
+                        nqp::bindpos_i($subbuf, $i, nqp::atpos_i(self, ++$pos))),
+                      $subbuf))))))
+    }
+
+    multi method subbuf(Blob:D: Range $from) {
+        nqp::stmts(
+          (my int $elems = nqp::elems(self)),
+            nqp::stmts(
+              (my int $pos),
+              (my int $todo),
+                  $from.int-bounds($pos, my int $max),
+                  ($todo = nqp::add_i(nqp::sub_i($max, $pos), 1)),
+              nqp::if(
+                nqp::islt_i($pos, 0),
+                X::OutOfRange.new(
+                  :what('From argument to subbuf'), :got($from.gist), :range("0..$elems"),
+                  :comment("use *-{abs $pos} if you want to index relative to the end"),
+                ).fail,
+                nqp::if(
+                  nqp::isgt_i($pos, $elems),
+                  X::OutOfRange.new(
+                    :what('From argument to subbuf'), :got($from.gist), :range("0..$elems"),
+                  ).fail,
+                  nqp::if(
+                    nqp::isle_i($todo, 0),
+                    nqp::create(self), # we want zero elements; return empty Blob
+                    nqp::stmts(
+                      (my $subbuf := nqp::create(self)),
+                      nqp::setelems($subbuf, $todo),
+                      (my int $i = -1),
+                      --$pos,
+                      nqp::while(
+                        nqp::islt_i(++$i,$todo),
+                        nqp::bindpos_i($subbuf, $i, nqp::atpos_i(self, ++$pos))),
+                      $subbuf))))))
+    }
+
+    multi method subbuf(Blob:D: $from, $length) {
         nqp::stmts(
           (my int $elems = nqp::elems(self)),
           nqp::if(
-            $length.DEFINITE && $length < 0,
+            nqp::islt_i($length, 0),
             X::OutOfRange.new(
               :what('Len element to subbuf'), :got($length), :range("0..$elems"),
             ).fail,
@@ -188,7 +255,7 @@ my role Blob[::T = uint8] does Positional[T] does Stringy is repr('VMArray') is
                   ($todo = nqp::add_i(nqp::sub_i($max, $pos), 1))),
                 nqp::stmts(
                   ($pos = nqp::istype($from, Callable) ?? $from($elems) !! $from.Int),
-                  ($todo = $length.DEFINITE ?? $length.Int min $elems - $pos !! $elems - $pos))),
+                  ($todo = $length.Int min $elems - $pos))),
               nqp::if(
                 nqp::islt_i($pos, 0),
                 X::OutOfRange.new(