1 files changed, 72 insertions, 0 deletions
diff --git a/stdlib/source/lux/data/text/buffer.lux b/stdlib/source/lux/data/text/buffer.lux
new file mode 100644
index 000000000..423a1ba3c
--- /dev/null
+++ b/stdlib/source/lux/data/text/buffer.lux
@@ -0,0 +1,72 @@
+(.module:
+  lux
+  (lux (data [product]
+             text/format
+             (coll [row #+ Row "row/" Fold<Row>]))
+       (lang ["_" host])
+       (type abstract)
+       [host #+ import:])
+  [//])
+
+(`` (for {(~~ (static _.jvm))
+          (as-is (import: java/lang/CharSequence)
+
+                 (import: java/lang/Appendable
+                   (append [CharSequence] Appendable))
+
+                 (import: java/lang/StringBuilder
+                   (new [int])
+                   (toString [] String)))}))
+
+(`` (abstract: #export Buffer
+      {#.doc "Immutable text buffer for efficient text concatenation."}
+
+      (for {(~~ (static _.jvm))
+            [Nat (-> StringBuilder StringBuilder)]}
+           ## default
+           (Row Text))
+
+      (def: #export empty
+        Buffer
+        (:abstraction (for {(~~ (static _.jvm))
+                            [+0 id]}
+                           ## default
+                           row.empty)))
+
+      (def: #export (append chunk buffer)
+        (-> Text Buffer Buffer)
+        (for {(~~ (static _.jvm))
+              (let [[capacity transform] (:representation buffer)
+                    append! (: (-> Text StringBuilder StringBuilder)
+                               (function (_ chunk builder)
+                                 (exec (Appendable::append [(:coerce CharSequence chunk)]
+                                                           builder)
+                                   builder)))]
+                (:abstraction [(n/+ (//.size chunk) capacity)
+                               (|>> transform (append! chunk))]))}
+             ## default
+             (|> buffer :representation (row.add chunk) :abstraction)))
+
+      (def: #export (size buffer)
+        (-> Buffer Nat)
+        (for {(~~ (static _.jvm))
+              (|> buffer :representation product.left)}
+             ## default
+             (row/fold (function (_ chunk total)
+                         (n/+ (//.size chunk) total))
+                       +0
+                       (:representation buffer))))
+
+      (def: #export (text buffer)
+        (-> Buffer Text)
+        (for {(~~ (static _.jvm))
+              (let [[capacity transform] (:representation buffer)]
+                (|> (StringBuilder::new [(.int capacity)])
+                    transform
+                    (StringBuilder::toString [])))}
+             ## default
+             (row/fold (function (_ chunk total)
+                         (format total chunk))
+                       ""
+                       (:representation buffer))))
+      ))