Implement get for string

boa_engine/src/builtins/string/mod.rs

@@ -633,9 +633,11 @@ impl String {
 
         match position {
             // 4. Let size be the length of S.
-            IntegerOrInfinity::Integer(i) if i >= 0 && i < string.len() as i64 => {
+            IntegerOrInfinity::Integer(i) if i >= 0 => {
                 // 6. Return the Number value for the numeric value of the code unit at index position within the String S.
-                Ok(u32::from(string.to_vec()[i as usize]).into())
+                Ok(string
+                    .get(i as usize)
+                    .map_or_else(JsValue::nan, JsValue::from))
             }
             // 5. If position < 0 or position ≥ size, return NaN.
             _ => Ok(JsValue::nan()),

boa_engine/src/builtins/uri/mod.rs

@@ -309,7 +309,7 @@ where
         }
 
         // b. Let C be the code unit at index k within string.
-        let c = string.to_vec()[k];
+        let c = string.get_expect(k);
 
         // c. If C is in unescapedSet, then
         if unescaped_set(c) {
@@ -384,7 +384,7 @@ where
         }
 
         // b. Let C be the code unit at index k within string.
-        let c = string.to_vec()[k];
+        let c = string.get_expect(k);
 
         // c. If C is not the code unit 0x0025 (PERCENT SIGN), then
         #[allow(clippy::if_not_else)]
@@ -406,9 +406,10 @@ where
             // iii. If the code units at index (k + 1) and (k + 2) within string do not represent
             // hexadecimal digits, throw a URIError exception.
             // iv. Let B be the 8-bit value represented by the two hexadecimal digits at index (k + 1) and (k + 2).
-            let b = decode_hex_byte(string.to_vec()[k + 1], string.to_vec()[k + 2]).ok_or_else(
-                || JsNativeError::uri().with_message("invalid hexadecimal digit found"),
-            )?;
+            let b = decode_hex_byte(string.get_expect(k + 1), string.get_expect(k + 2))
+                .ok_or_else(|| {
+                    JsNativeError::uri().with_message("invalid hexadecimal digit found")
+                })?;
 
             // v. Set k to k + 2.
             k += 2;
@@ -456,7 +457,7 @@ where
                     k += 1;
 
                     // b. If the code unit at index k within string is not the code unit 0x0025 (PERCENT SIGN), throw a URIError exception.
-                    if string.to_vec()[k] != 0x0025 {
+                    if string.get_expect(k) != 0x0025 {
                         return Err(JsNativeError::uri()
                             .with_message("escape characters must be preceded with a % sign")
                             .into());
@@ -464,7 +465,7 @@ where
 
                     // c. If the code units at index (k + 1) and (k + 2) within string do not represent hexadecimal digits, throw a URIError exception.
                     // d. Let B be the 8-bit value represented by the two hexadecimal digits at index (k + 1) and (k + 2).
-                    let b = decode_hex_byte(string.to_vec()[k + 1], string.to_vec()[k + 2])
+                    let b = decode_hex_byte(string.get_expect(k + 1), string.get_expect(k + 2))
                         .ok_or_else(|| {
                             JsNativeError::uri().with_message("invalid hexadecimal digit found")
                         })?;

boa_engine/src/string/mod.rs

@@ -46,7 +46,7 @@ use std::{
     str::FromStr,
 };
 
-use self::common::StaticJsStrings;
+use self::{common::StaticJsStrings, str::JsSliceIndex};
 
 fn alloc_overflow() -> ! {
     panic!("detected overflow during string allocation")
@@ -883,17 +883,6 @@ impl JsString {
         self.len() == 0
     }
 
-    // pub fn get<I>(&self, index: I) -> Option<<I::Output as ToOwned>::Owned>
-    // where
-    //     I: SliceIndex<[u16]>,
-    //     <I as SliceIndex<[u16]>>::Output: ToOwned,
-    // {
-    //     match self.as_slice() {
-    //         StringSlice::Ascii(v) => v.get(index).map(ToOwned::to_owned),
-    //         StringSlice::U16(v) => v.get(index).map(ToOwned::to_owned),
-    //     }
-    // }
-
     pub fn to_vec(&self) -> Vec<u16> {
         match self.as_str().variant() {
             JsStrVariant::Ascii(v) => v.bytes().map(u16::from).collect(),
@@ -924,6 +913,20 @@ impl JsString {
     pub fn is_static(&self) -> bool {
         self.ptr.is_tagged()
     }
+
+    pub fn get<'a, I>(&'a self, index: I) -> Option<I::Value>
+    where
+        I: JsSliceIndex<'a>,
+    {
+        I::get(self.as_str(), index)
+    }
+
+    pub fn get_expect<'a, I>(&'a self, index: I) -> I::Value
+    where
+        I: JsSliceIndex<'a>,
+    {
+        self.get(index).expect("Index out of bounds")
+    }
 }
 
 impl Clone for JsString {
@@ -1089,15 +1092,6 @@ impl Hash for JsString {
     }
 }
 
-// impl<I: SliceIndex<[u16]>> Index<I> for JsString {
-//     type Output = I::Output;
-
-//     #[inline]
-//     fn index(&self, index: I) -> &Self::Output {
-//         Index::index(&**self, index)
-//     }
-// }
-
 impl Ord for JsString {
     fn cmp(&self, other: &Self) -> std::cmp::Ordering {
         self.to_vec().cmp(&other.to_vec())

boa_engine/src/string/str.rs

@@ -1,3 +1,5 @@
+use std::slice::SliceIndex;
+
 use crate::{builtins::string::is_trimmable_whitespace, string::Iter};
 use boa_interner::JStrRef;
 
@@ -150,4 +152,62 @@ impl<'a> JsStr<'a> {
             }
         }
     }
+
+    pub fn get<I>(&'a self, index: I) -> Option<I::Value>
+    where
+        I: JsSliceIndex<'a>,
+    {
+        I::get(*self, index)
+    }
+}
+
+pub trait JsSliceIndex<'a>: SliceIndex<[u8]> + SliceIndex<[u16]> {
+    type Value;
+
+    fn get(_: JsStr<'a>, index: Self) -> Option<Self::Value>;
+}
+
+impl<'a> JsSliceIndex<'a> for usize {
+    type Value = u16;
+
+    fn get(value: JsStr<'a>, index: Self) -> Option<Self::Value> {
+        match value.variant() {
+            JsStrVariant::Ascii(v) => v.as_bytes().get(index).copied().map(u16::from),
+            JsStrVariant::U16(v) => v.get(index).copied(),
+        }
+    }
+}
+
+impl<'a> JsSliceIndex<'a> for std::ops::Range<usize> {
+    type Value = JsStr<'a>;
+
+    fn get(value: JsStr<'a>, index: Self) -> Option<Self::Value> {
+        match value.variant() {
+            JsStrVariant::Ascii(v) => {
+                let slice = v.as_bytes().get(index)?;
+                // SAFETY: Getting a sub-slice of an ASCII array, retuns an ASCII array, so this is safe.
+                let str = unsafe { std::str::from_utf8_unchecked(slice) };
+
+                // SAFETY: `from_utf8_unchecked` does not alter the string, so this is safe.
+                Some(unsafe { JsStr::ascii_unchecked(str) })
+            }
+            JsStrVariant::U16(v) => {
+                let slice = v.get(index)?;
+
+                // TODO: If we sub-slice an utf16 array, and the sub-slice has only ASCII characters then we need,
+                //       account for that.
+                //
+                // SAFETY:
+                Some(unsafe { JsStr::u16_unchecked(slice) })
+            }
+        }
+    }
+}
+
+impl<'a> JsSliceIndex<'a> for std::ops::RangeFull {
+    type Value = JsStr<'a>;
+
+    fn get(value: JsStr<'a>, _index: Self) -> Option<Self::Value> {
+        Some(value)
+    }
 }