perf: mappings encoder and decoder (#114)

* perf: MappingsEncoder

* perf: new mappings decoder

Author: SyMind

Cargo.lock

@@ -36,7 +36,6 @@ dyn-clone = "1"
 rustc-hash = "1"
 dashmap = "5"
 memchr = "2.6.4"
-arrayvec = "0.7.4"
 
 codspeed-criterion-compat = { version = "2.3.3", default-features = false, optional = true }
 simd-json = "=0.14.0-rc.2"

Cargo.toml

@@ -0,0 +1,171 @@
+use std::slice::Iter;
+
+use crate::{Mapping, OriginalLocation};
+
+const COM: u8 = 0x40; // END_SEGMENT_BIT
+const SEM: u8 = COM | 0x01; // NEXT_LINE
+const ERR: u8 = COM | 0x02; // INVALID
+
+const CONTINUATION_BIT: u8 = 0x20;
+const DATA_MASK: u8 = 0x1f;
+
+#[rustfmt::skip]
+const B64: [u8; 256] = [
+//  0    1    2    3    4    5    6    7    8    9    A    B    C    D    E    F    //
+   ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR,  // 0
+   ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR,  // 1
+   ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR,  62, COM, ERR, ERR,  63,  // 2
+    52,  53,  54,  55,  56,  57,  58,  59,  60,  61, ERR, SEM, ERR, ERR, ERR, ERR,  // 3
+   ERR,   0,   1,   2,   3,   4,   5,   6,   7,   8,   9,  10,  11,  12,  13,  14,  // 4
+    15,  16,  17,  18,  19,  20,  21,  22,  23,  24,  25, ERR, ERR, ERR, ERR, ERR,  // 5
+   ERR,  26,  27,  28,  29,  30,  31,  32,  33,  34,  35,  36,  37,  38,  39,  40,  // 6
+    41,  42,  43,  44,  45,  46,  47,  48,  49,  50,  51, ERR, ERR, ERR, ERR, ERR,  // 7
+   ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR,  // 8
+   ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR,  // 9
+   ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR,  // A
+   ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR,  // B
+   ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR,  // C
+   ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR,  // D
+   ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR,  // E
+   ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR, ERR,  // F
+];
+
+pub(crate) struct MappingsDecoder<'a> {
+  mappings_iter: Iter<'a, u8>,
+
+  current_data: [u32; 5],
+  current_data_pos: usize,
+  // current_value will include a sign bit at bit 0
+  current_value: i64,
+  current_value_pos: usize,
+  generated_line: u32,
+  generated_column: i64,
+}
+
+impl<'a> MappingsDecoder<'a> {
+  pub fn new(mappings: &'a str) -> Self {
+    Self {
+      mappings_iter: mappings.as_bytes().iter(),
+      current_data: [0u32, 0u32, 1u32, 0u32, 0u32],
+      current_data_pos: 0,
+      // current_value will include a sign bit at bit 0
+      current_value: 0,
+      current_value_pos: 0,
+      generated_line: 1,
+      generated_column: -1,
+    }
+  }
+}
+
+impl<'a> Iterator for MappingsDecoder<'a> {
+  type Item = Mapping;
+
+  fn next(&mut self) -> Option<Self::Item> {
+    for c in &mut self.mappings_iter {
+      let value = B64[*c as usize];
+      if value == ERR {
+        continue;
+      }
+      if (value & COM) != 0 {
+        let mapping = match self.current_data_pos {
+          1 => Some(Mapping {
+            generated_line: self.generated_line,
+            generated_column: self.current_data[0],
+            original: None,
+          }),
+          4 => Some(Mapping {
+            generated_line: self.generated_line,
+            generated_column: self.current_data[0],
+            original: Some(OriginalLocation {
+              source_index: self.current_data[1],
+              original_line: self.current_data[2],
+              original_column: self.current_data[3],
+              name_index: None,
+            }),
+          }),
+          5 => Some(Mapping {
+            generated_line: self.generated_line,
+            generated_column: self.current_data[0],
+            original: Some(OriginalLocation {
+              source_index: self.current_data[1],
+              original_line: self.current_data[2],
+              original_column: self.current_data[3],
+              name_index: Some(self.current_data[4]),
+            }),
+          }),
+          _ => None,
+        };
+        self.generated_column = self.current_data[0] as i64;
+        self.current_data_pos = 0;
+        if value == SEM {
+          self.generated_line += 1;
+          self.current_data[0] = 0;
+          self.generated_column = -1;
+        }
+        if mapping.is_some() {
+          return mapping;
+        }
+      } else if (value & CONTINUATION_BIT) == 0 {
+        // last sextet
+        self.current_value |= (value as i64) << self.current_value_pos;
+        let final_value = if (self.current_value & 1) != 0 {
+          -(self.current_value >> 1)
+        } else {
+          self.current_value >> 1
+        };
+        if self.current_data_pos < 5 {
+          self.current_data[self.current_data_pos] =
+            (self.current_data[self.current_data_pos] as i64 + final_value)
+              as u32;
+        }
+        self.current_data_pos += 1;
+        self.current_value_pos = 0;
+        self.current_value = 0;
+      } else {
+        self.current_value |=
+          ((value & DATA_MASK) as i64) << self.current_value_pos;
+        self.current_value_pos += 5;
+      }
+    }
+
+    // end current segment
+    let current_data_pos = self.current_data_pos;
+    self.current_data_pos = 0;
+    match current_data_pos {
+      1 => {
+        return Some(Mapping {
+          generated_line: self.generated_line,
+          generated_column: self.current_data[0],
+          original: None,
+        })
+      }
+      4 => {
+        return Some(Mapping {
+          generated_line: self.generated_line,
+          generated_column: self.current_data[0],
+          original: Some(OriginalLocation {
+            source_index: self.current_data[1],
+            original_line: self.current_data[2],
+            original_column: self.current_data[3],
+            name_index: None,
+          }),
+        })
+      }
+      5 => {
+        return Some(Mapping {
+          generated_line: self.generated_line,
+          generated_column: self.current_data[0],
+          original: Some(OriginalLocation {
+            source_index: self.current_data[1],
+            original_line: self.current_data[2],
+            original_column: self.current_data[3],
+            name_index: Some(self.current_data[4]),
+          }),
+        })
+      }
+      _ => (),
+    }
+
+    None
+  }
+}