1 files changed, 67 insertions, 0 deletions
diff --git a/vendor/pest_meta/src/optimizer/unroller.rs b/vendor/pest_meta/src/optimizer/unroller.rs
new file mode 100644
index 000000000..fff17336d
--- /dev/null
+++ b/vendor/pest_meta/src/optimizer/unroller.rs
@@ -0,0 +1,67 @@
+// pest. The Elegant Parser
+// Copyright (c) 2018 Dragoș Tiselice
+//
+// Licensed under the Apache License, Version 2.0
+// <LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0> or the MIT
+// license <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. All files in the project carrying such notice may not be copied,
+// modified, or distributed except according to those terms.
+
+use ast::*;
+
+pub fn unroll(rule: Rule) -> Rule {
+    match rule {
+        Rule { name, ty, expr } => Rule {
+            name,
+            ty,
+            expr: expr.map_bottom_up(|expr| match expr {
+                Expr::RepOnce(expr) => Expr::Seq(expr.clone(), Box::new(Expr::Rep(expr))),
+                Expr::RepExact(expr, num) => (1..num + 1)
+                    .map(|_| *expr.clone())
+                    .rev()
+                    .fold(None, |rep, expr| match rep {
+                        None => Some(expr),
+                        Some(rep) => Some(Expr::Seq(Box::new(expr), Box::new(rep))),
+                    })
+                    .unwrap(),
+                Expr::RepMin(expr, min) => (1..min + 2)
+                    .map(|i| {
+                        if i <= min {
+                            *expr.clone()
+                        } else {
+                            Expr::Rep(expr.clone())
+                        }
+                    })
+                    .rev()
+                    .fold(None, |rep, expr| match rep {
+                        None => Some(expr),
+                        Some(rep) => Some(Expr::Seq(Box::new(expr), Box::new(rep))),
+                    })
+                    .unwrap(),
+                Expr::RepMax(expr, max) => (1..max + 1)
+                    .map(|_| Expr::Opt(expr.clone()))
+                    .rev()
+                    .fold(None, |rep, expr| match rep {
+                        None => Some(expr),
+                        Some(rep) => Some(Expr::Seq(Box::new(expr), Box::new(rep))),
+                    })
+                    .unwrap(),
+                Expr::RepMinMax(expr, min, max) => (1..max + 1)
+                    .map(|i| {
+                        if i <= min {
+                            *expr.clone()
+                        } else {
+                            Expr::Opt(expr.clone())
+                        }
+                    })
+                    .rev()
+                    .fold(None, |rep, expr| match rep {
+                        None => Some(expr),
+                        Some(rep) => Some(Expr::Seq(Box::new(expr), Box::new(rep))),
+                    })
+                    .unwrap(),
+                expr => expr,
+            }),
+        },
+    }
+}