rebase on slyce

Author: glyn

Cargo.toml

@@ -11,3 +11,4 @@ pest = "2.1.3"
 pest_derive = "2.1.0"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0.57"
+slyce = "0.2.1"

src/ast.rs

@@ -5,7 +5,7 @@
  */
 
 use serde_json::Value;
-use std::cmp::Ordering;
+use slyce::Slice;
 use std::iter;
 
 /// A path is a tree of selector nodes.
@@ -63,13 +63,6 @@ pub enum UnionElement {
     Index(i64),
 }
 
-#[derive(Debug)]
-pub struct Slice {
-    pub start: Option<isize>,
-    pub end: Option<isize>,
-    pub step: Option<isize>,
-}
-
 type Iter<'a> = Box<dyn Iterator<Item = &'a Value> + 'a>;
 
 impl Path {
@@ -101,7 +94,7 @@ impl UnionElement {
             UnionElement::Name(name) => Box::new(v.get(name).into_iter()),
             UnionElement::Slice(slice) => {
                 if let Value::Array(arr) = v {
-                    Box::new(array_slice(arr, slice.start, slice.end, slice.step))
+                    Box::new(slice.apply(arr))
                 } else {
                     Box::new(iter::empty())
                 }
@@ -111,59 +104,6 @@ impl UnionElement {
     }
 }
 
-fn array_slice(
-    arr: &[Value],
-    optional_start: Option<isize>,
-    optional_end: Option<isize>,
-    optional_step: Option<isize>,
-) -> Iter<'_> {
-    let step = optional_step.unwrap_or(1);
-
-    let len = arr.len();
-
-    let start = optional_start
-        .map(|s| if s < 0 { s + (len as isize) } else { s })
-        .unwrap_or(if step > 0 { 0 } else { (len as isize) - 1 });
-
-    let end = optional_end
-        .map(|e| if e < 0 { e + (len as isize) } else { e })
-        .unwrap_or(if step > 0 { len as isize } else { -1 });
-
-    let mut sl = vec![];
-    match step.cmp(&0) {
-        Ordering::Greater => {
-            let strt = if start < 0 { 0 } else { start as usize }; // avoid CPU attack
-            let e = if end > (len as isize) {
-                len
-            } else {
-                end as usize
-            }; // avoid CPU attack
-            for i in (strt..e).step_by(step as usize) {
-                if i < len {
-                    sl.push(&arr[i]);
-                }
-            }
-        }
-
-        Ordering::Less => {
-            let strt = if start > (len as isize) {
-                len as isize
-            } else {
-                start
-            }; // avoid CPU attack
-            let e = if end < -1 { -1 } else { end }; // avoid CPU attack
-            for i in (-strt..-e).step_by(-step as usize) {
-                if 0 <= -i && -i < (len as isize) {
-                    sl.push(&arr[-i as usize]);
-                }
-            }
-        }
-
-        Ordering::Equal => (),
-    }
-    Box::new(sl.into_iter())
-}
-
 fn abs_index(index: i64, node: &Value) -> usize {
     if index >= 0 {
         index as usize

src/parser.rs

@@ -6,6 +6,7 @@
 
 pub use crate::ast::*;
 use crate::pest::Parser;
+use slyce::{Index, Slice};
 
 #[derive(Parser)]
 #[grammar = "grammar.pest"]
@@ -94,7 +95,11 @@ fn parse_union_array_slice(matcher_rule: pest::iterators::Pair<Rule>) -> UnionEl
         }
     }
 
-    UnionElement::Slice(Slice { start, end, step })
+    UnionElement::Slice(Slice {
+        start: start.map(Index::from).unwrap_or_default(),
+        end: end.map(Index::from).unwrap_or_default(),
+        step,
+    })
 }
 
 fn unescape(contents: &str) -> String {

tests/cts.json

@@ -599,7 +599,7 @@
     "document": [0, 1, 2, 3],
 		"result": [2, 1, 0]
 	}, {
-		"name": "union array slice, larger negative step",
+    "name": "union array slice, larger negative step",
 		"selector": "$[::-2]",
     "document": [0, 1, 2, 3],
 		"result": [3, 1]
@@ -667,12 +667,12 @@
     "document": [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 		"result": []
 	}, {
-		"name": "union array slice, default indices with empty array",
+    "name": "union array slice, default indices with empty array",
 		"selector": "$[:]",
     "document": [],
 		"result": []
 	}, {
-		"name": "union array slice, negative step with empty array",
+    "name": "union array slice, negative step with empty array",
 		"selector": "$[::-1]",
     "document": [],
 		"result": []
@@ -702,7 +702,7 @@
     "document": [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 		"result": [9, 8, 7, 6, 5, 4, 3, 2, 1]
 	}, {
-		"name": "union array slice, excessively small to value with negative step",
+    "name": "union array slice, excessively small to value with negative step",
 		"selector": "$[3:-113667776004:-1]",
     "document": [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
 		"result": [3, 2, 1, 0]