[Buf] Str.encode and Buf.decode

Also a few other goodies, such as the Stringy role.
A bunch of tests now pass in t/spec/S32-str/encode.rakudo.

build/Makefile.in

@@ -190,6 +190,8 @@ CORE_SOURCES = \
   src/core/Num.pm \
   src/core/Rat.pm \
   src/core/Complex.pm \
+  src/core/Stringy.pm \
+  src/core/Buf.pm \
   src/core/Str.pm \
   src/core/Whatever.pm \
   src/core/Pair.pm \

src/core/Buf.pm

@@ -0,0 +1,42 @@
+role Buf[::T = Int] does Stringy {
+    has @.contents;
+
+    multi method new(@contents) {
+        self.bless(*, :contents(@contents.list));
+    }
+
+    multi method new(*@contents) {
+        self.bless(*, :contents(@contents.list));
+    }
+
+    multi method decode($encoding = 'UTF-8') {
+        my @contents = @.contents;
+        my $str = ~Q:PIR {
+            $P0 = find_lex '@contents'
+
+            .local pmc iterator
+            iterator = iter $P0
+            .local pmc sb
+            sb = new 'StringBuilder'
+            sb = unicode:""
+            loop:
+              unless iterator goto done
+              $P1 = shift iterator
+              $I1 = $P1
+              $S1 = chr $I1
+              sb .= $S1
+              goto loop
+            done:
+              %r = sb
+        };
+        return $str;
+    }
+
+    multi method elems() {
+        @.contents.elems;
+    }
+}
+
+our multi sub infix:<eqv>(Buf $a, Buf $b) {
+    return $a.contents ~~ $b.contents;
+}

src/core/Str.pm

@@ -1,4 +1,4 @@
-augment class Str {
+augment class Str does Stringy {
     multi method Bool { ?(pir::istrue__IP(self)); }
 
     method Str() { self }
@@ -19,4 +19,29 @@ augment class Str {
     method s() {
         self.e ?? pir::stat__ISI(self, 1) !! Any;
     }
+
+    # XXX: We have no $?ENC or $?NF compile-time constants yet.
+    multi method encode($encoding = 'UTF-8', $nf = '') {
+        my @bytes = Q:PIR {
+            .local int bin_coding, i, max, byte
+            .local string bin_string
+            .local pmc it, result
+            $P0 = find_lex 'self'
+            $S0 = $P0
+            bin_coding = find_encoding 'fixed_8'
+            bin_string = trans_encoding $S0, bin_coding
+            result = new ['Parcel']
+            i = 0
+            max = length bin_string
+          bytes_loop:
+            if i >= max goto bytes_done
+            byte = ord bin_string, i
+            push result, byte
+            inc i
+            goto bytes_loop
+          bytes_done:
+            %r = result
+        };
+        return Buf.new(@bytes);
+    }
 }

src/core/Stringy.pm

@@ -0,0 +1,2 @@
+role Stringy {
+}