perf: optimize decode mappings (#101)

* reserve vec and remove clone

* remove reserve

* use arrayvec

* Fix clippy

Author: CPunisher

Cargo.lock

@@ -36,11 +36,11 @@ dyn-clone = "1"
 rustc-hash = "1"
 dashmap = "5"
 substring = "1"
-smallvec = "1.11.2"
 memchr = "2.6.4"
 str_indices = "0.4.3"
 
 codspeed-criterion-compat = { version = "2.3.3", default-features = false, optional = true }
+arrayvec = "0.7.4"
 
 [dev-dependencies]
 twox-hash = "1"

Cargo.toml

@@ -1,3 +1,4 @@
+use arrayvec::ArrayVec;
 use rustc_hash::FxHashMap as HashMap;
 use std::{
   borrow::{BorrowMut, Cow},
@@ -136,7 +137,7 @@ pub struct SegmentIter<'a> {
   original_column: u32,
   name_index: u32,
   line: &'a str,
-  nums: Vec<i64>,
+  nums: ArrayVec<i64, 5>,
   segment_cursor: usize,
 }
 
@@ -152,7 +153,7 @@ impl<'a> SegmentIter<'a> {
       generated_line: 0,
       segment_cursor: 0,
       generated_column: 0,
-      nums: Vec::with_capacity(5),
+      nums: ArrayVec::new(),
     }
   }
 
@@ -652,7 +653,7 @@ fn stream_chunks_of_source_map_final(
     }
   };
   for mapping in source_map.decoded_mappings() {
-    on_mapping(&mapping);
+    on_mapping(mapping);
   }
   result
 }
@@ -793,7 +794,7 @@ fn stream_chunks_of_source_map_full(
   };
 
   for mapping in source_map.decoded_mappings() {
-    on_mapping(&mapping);
+    on_mapping(mapping);
   }
   on_mapping(&Mapping {
     generated_line: final_line,
@@ -856,7 +857,7 @@ fn stream_chunks_of_source_map_lines_final(
     }
   };
   for mapping in source_map.decoded_mappings() {
-    on_mapping(&mapping);
+    on_mapping(mapping);
   }
   result
 }
@@ -924,7 +925,7 @@ fn stream_chunks_of_source_map_lines_full(
     }
   };
   for mapping in source_map.decoded_mappings() {
-    on_mapping(&mapping);
+    on_mapping(mapping);
   }
   while current_generated_line as usize <= lines.len() {
     on_chunk(

src/helpers.rs

@@ -232,12 +232,10 @@ impl SourceMap {
   }
 
   /// Get the decoded mappings in [SourceMap].
-  pub fn decoded_mappings(&'_ self) -> impl IntoIterator<Item = Mapping> + '_ {
+  pub fn decoded_mappings(&'_ self) -> &[Mapping] {
     self
       .decoded_mappings
       .get_or_init(|| decode_mappings(self).collect::<Vec<_>>())
-      .clone()
-      .into_iter()
   }
 
   /// Get the mappings string in [SourceMap].

src/source.rs

@@ -1,6 +1,8 @@
 //! Implements utilities for dealing with the sourcemap vlq encoding.
 //! forked from [rust-sourcemap](https://github.com/getsentry/rust-sourcemap/blob/851f12bfa6c4cf2c737b94734b27f7d9bfb4de86/src/vlq.rs)
 
+use arrayvec::ArrayVec;
+
 use crate::{Error, Result};
 
 const B64_CHARS: &[u8] =
@@ -265,7 +267,7 @@ const B64: [i8; 256] = [
 ];
 
 /// Parses a VLQ segment into a pre-allocated `Vec` instead of returning a new allocation.
-pub fn decode(segment: &str, rv: &mut Vec<i64>) -> Result<()> {
+pub fn decode(segment: &str, rv: &mut ArrayVec<i64, 5>) -> Result<()> {
   let mut cur = 0;
   let mut shift = 0;