diff --git a/src/kicad_sexpr.gleam b/src/kicad_sexpr.gleam
index 98a1120..be94e27 100644
--- a/src/kicad_sexpr.gleam
+++ b/src/kicad_sexpr.gleam
@@ -1,13 +1,11 @@
 import gleam/float
 import gleam/int
 import gleam/io
-
 import gleam/list
 import gleam/result
 import gleam/string
 import kicad_sexpr/decode
 import kicad_sexpr/parse
-
 import kicad_sexpr/token
 import simplifile
 
@@ -41,7 +39,7 @@ pub fn main() -> Nil {
   let #(successfully_read, _failed_to_read) =
     file_names
     |> list.map(fn(file_name) {
-      simplifile.read(file_name)
+      simplifile.read_bits(file_name)
       |> result.map(fn(res) { #(file_name, res) })
       |> result.map_error(fn(res) { #(file_name, res) })
     })
diff --git a/src/kicad_sexpr/parse.gleam b/src/kicad_sexpr/parse.gleam
index 3f475bf..18c598a 100644
--- a/src/kicad_sexpr/parse.gleam
+++ b/src/kicad_sexpr/parse.gleam
@@ -1,8 +1,6 @@
-import gleam/bool
 import gleam/float
 import gleam/int
 import gleam/list
-import gleam/option.{type Option, None, Some}
 import gleam/result
 import gleam/string
 
@@ -11,9 +9,10 @@ pub type ParseError {
   UnexpectedTokenCharacter(got: String, expected: String)
   UnexpectedNameCharacter(got: String)
   UnexpectedNumberCharacter(got: String)
-  UnexpectedTrailingString(got: String)
   UnterminatedString(got: String)
   InvalidNumber(got: String)
+  UnexpectedTrailingData(got: BitArray)
+  InvalidUtf8Character(got: BitArray)
 }
 
 pub type SExpr {
@@ -25,7 +24,7 @@ pub type SExpr {
 }
 
 pub type Parsed(a) =
-  Result(#(a, String), ParseError)
+  Result(#(a, BitArray), ParseError)
 
 pub fn sexpr_to_pretty_string(sexpr: SExpr) -> String {
   do_sexpr_to_pretty_string(sexpr, "")
@@ -47,170 +46,218 @@ fn do_sexpr_to_pretty_string(sexpr: SExpr, pad: String) -> String {
   }
 }
 
-pub fn run(source: String) -> Result(SExpr, ParseError) {
-  let source = string.trim(source)
+pub fn run(source: BitArray) -> Result(SExpr, ParseError) {
+  let source = trim_start(source)
   use #(token, rest) <- result.try(attribute(source))
-  case string.trim(rest) {
-    "" -> Ok(token)
-    rest -> Error(UnexpectedTrailingString(rest))
+  case trim_start(rest) {
+    <<>> -> Ok(token)
+    rest -> Error(UnexpectedTrailingData(rest))
   }
 }
 
-pub fn token(source: String) -> Parsed(SExpr) {
-  use #(name, rest) <- result.try(name(source))
-  use #(attributes, rest) <- result.try(attributes(rest))
-  Ok(#(Token(name:, attributes:), rest))
-}
-
-fn name_char(source: String) -> Parsed(String) {
+fn trim_start(source: BitArray) -> BitArray {
   case source {
-    "" -> Error(UnexpectedEndOfFile)
-    "a" <> rest -> Ok(#("a", rest))
-    "b" <> rest -> Ok(#("b", rest))
-    "c" <> rest -> Ok(#("c", rest))
-    "d" <> rest -> Ok(#("d", rest))
-    "e" <> rest -> Ok(#("e", rest))
-    "f" <> rest -> Ok(#("f", rest))
-    "g" <> rest -> Ok(#("g", rest))
-    "h" <> rest -> Ok(#("h", rest))
-    "i" <> rest -> Ok(#("i", rest))
-    "j" <> rest -> Ok(#("j", rest))
-    "k" <> rest -> Ok(#("k", rest))
-    "l" <> rest -> Ok(#("l", rest))
-    "m" <> rest -> Ok(#("m", rest))
-    "n" <> rest -> Ok(#("n", rest))
-    "o" <> rest -> Ok(#("o", rest))
-    "p" <> rest -> Ok(#("p", rest))
-    "q" <> rest -> Ok(#("q", rest))
-    "r" <> rest -> Ok(#("r", rest))
-    "s" <> rest -> Ok(#("s", rest))
-    "t" <> rest -> Ok(#("t", rest))
-    "u" <> rest -> Ok(#("u", rest))
-    "v" <> rest -> Ok(#("v", rest))
-    "w" <> rest -> Ok(#("w", rest))
-    "x" <> rest -> Ok(#("x", rest))
-    "y" <> rest -> Ok(#("y", rest))
-    "z" <> rest -> Ok(#("z", rest))
-    "_" <> rest -> Ok(#("_", rest))
-    _ ->
-      Error(UnexpectedNameCharacter(string.first(source) |> result.unwrap("")))
+    <<32, rest:bits>>
+    | <<9, rest:bits>>
+    | <<10, rest:bits>>
+    | <<11, rest:bits>>
+    | <<12, rest:bits>>
+    | <<13, rest:bits>> -> trim_start(rest)
+    _ -> source
   }
 }
 
-pub fn name(source: String) -> Parsed(String) {
-  use #(char, rest) <- result.try(name_char(source))
-  do_name(rest, char)
+@external(erlang, "gleam_stdlib", "identity")
+@external(javascript, "../gleam_stdlib.mjs", "codepoint")
+fn utf_codepoint_unsafe(a: Int) -> UtfCodepoint
+
+fn name_char(source: BitArray) -> Parsed(UtfCodepoint) {
+  case source {
+    <<>> -> Error(UnexpectedEndOfFile)
+    <<65 as i, rest:bits>>
+    | <<66 as i, rest:bits>>
+    | <<67 as i, rest:bits>>
+    | <<68 as i, rest:bits>>
+    | <<69 as i, rest:bits>>
+    | <<70 as i, rest:bits>>
+    | <<71 as i, rest:bits>>
+    | <<72 as i, rest:bits>>
+    | <<73 as i, rest:bits>>
+    | <<74 as i, rest:bits>>
+    | <<75 as i, rest:bits>>
+    | <<76 as i, rest:bits>>
+    | <<77 as i, rest:bits>>
+    | <<78 as i, rest:bits>>
+    | <<79 as i, rest:bits>>
+    | <<80 as i, rest:bits>>
+    | <<81 as i, rest:bits>>
+    | <<82 as i, rest:bits>>
+    | <<83 as i, rest:bits>>
+    | <<84 as i, rest:bits>>
+    | <<85 as i, rest:bits>>
+    | <<86 as i, rest:bits>>
+    | <<87 as i, rest:bits>>
+    | <<88 as i, rest:bits>>
+    | <<89 as i, rest:bits>>
+    | <<90 as i, rest:bits>>
+    | <<97 as i, rest:bits>>
+    | <<98 as i, rest:bits>>
+    | <<99 as i, rest:bits>>
+    | <<100 as i, rest:bits>>
+    | <<101 as i, rest:bits>>
+    | <<102 as i, rest:bits>>
+    | <<103 as i, rest:bits>>
+    | <<104 as i, rest:bits>>
+    | <<105 as i, rest:bits>>
+    | <<106 as i, rest:bits>>
+    | <<107 as i, rest:bits>>
+    | <<108 as i, rest:bits>>
+    | <<109 as i, rest:bits>>
+    | <<110 as i, rest:bits>>
+    | <<111 as i, rest:bits>>
+    | <<112 as i, rest:bits>>
+    | <<113 as i, rest:bits>>
+    | <<114 as i, rest:bits>>
+    | <<115 as i, rest:bits>>
+    | <<116 as i, rest:bits>>
+    | <<117 as i, rest:bits>>
+    | <<118 as i, rest:bits>>
+    | <<119 as i, rest:bits>>
+    | <<120 as i, rest:bits>>
+    | <<121 as i, rest:bits>>
+    | <<122 as i, rest:bits>>
+    | <<48 as i, rest:bits>>
+    | <<49 as i, rest:bits>>
+    | <<50 as i, rest:bits>>
+    | <<51 as i, rest:bits>>
+    | <<52 as i, rest:bits>>
+    | <<53 as i, rest:bits>>
+    | <<54 as i, rest:bits>>
+    | <<55 as i, rest:bits>>
+    | <<56 as i, rest:bits>>
+    | <<57 as i, rest:bits>>
+    | <<95 as i, rest:bits>>
+    | <<42 as i, rest:bits>>
+    | <<45 as i, rest:bits>>
+    | <<46 as i, rest:bits>> -> Ok(#(utf_codepoint_unsafe(i), rest))
+    <<cp:utf8_codepoint, _:bits>> ->
+      Error(UnexpectedNameCharacter(string.from_utf_codepoints([cp])))
+    source -> Error(InvalidUtf8Character(source))
+  }
 }
 
-fn do_name(source: String, result: String) -> Parsed(String) {
+fn do_name(source: BitArray, result: List(UtfCodepoint)) -> Parsed(String) {
   case name_char(source) {
-    Ok(#(char, rest)) -> do_name(rest, result <> char)
-    Error(_) -> Ok(#(result, source))
+    Ok(#(cp, rest)) -> do_name(rest, [cp, ..result])
+    Error(_) ->
+      Ok(#(result |> list.reverse |> string.from_utf_codepoints, source))
   }
 }
 
-pub fn attributes(source: String) -> Parsed(List(SExpr)) {
-  do_attributes(source, [])
-}
-
-fn do_attributes(source: String, attributes: List(SExpr)) -> Parsed(List(SExpr)) {
-  case string.trim_start(source) {
-    "" -> Error(UnexpectedEndOfFile)
-    ")" <> rest -> Ok(#(list.reverse(attributes), rest))
+fn do_attributes(source: BitArray, attrs: List(SExpr)) -> Parsed(List(SExpr)) {
+  case trim_start(source) {
+    <<>> -> Error(UnexpectedEndOfFile)
+    <<41, rest:bits>> -> Ok(#(attrs |> list.reverse, rest))
     source -> {
-      use #(attribute, rest) <- result.try(attribute(source))
-      do_attributes(rest, [attribute, ..attributes])
+      use #(attr, rest) <- result.try(attribute(source))
+      do_attributes(rest, [attr, ..attrs])
     }
   }
 }
 
-pub fn attribute(source: String) -> Parsed(SExpr) {
+fn attribute(source: BitArray) -> Parsed(SExpr) {
   case source {
-    "" -> Error(UnexpectedEndOfFile)
-    "(" <> rest -> {
-      use #(token, rest) <- result.try(token(rest))
-      Ok(#(token, rest))
+    <<>> -> Error(UnexpectedEndOfFile)
+    <<40, rest:bits>> -> {
+      use #(cp, rest) <- result.try(name_char(rest))
+      use #(name, rest) <- result.try(do_name(rest, [cp]))
+      use #(attributes, rest) <- result.try(do_attributes(rest, []))
+      Ok(#(Token(name:, attributes:), rest))
     }
-    "\"" <> rest -> {
-      use #(str, rest) <- result.try(string(rest))
+    <<34, rest:bits>> -> {
+      use #(str, rest) <- result.try(do_string(rest, []))
       Ok(#(String(str), rest))
     }
+    <<45 as i, rest:bits>>
+    | <<48 as i, rest:bits>>
+    | <<49 as i, rest:bits>>
+    | <<50 as i, rest:bits>>
+    | <<51 as i, rest:bits>>
+    | <<52 as i, rest:bits>>
+    | <<53 as i, rest:bits>>
+    | <<54 as i, rest:bits>>
+    | <<55 as i, rest:bits>>
+    | <<56 as i, rest:bits>>
+    | <<57 as i, rest:bits>> ->
+      do_number(rest, #([utf_codepoint_unsafe(i)], False))
     source -> {
-      use <- option.lazy_unwrap(try_number(source))
-      use #(name, rest) <- result.try(name(source))
+      use #(cp, rest) <- result.try(name_char(source))
+      use #(name, rest) <- result.try(do_name(rest, [cp]))
       Ok(#(Name(name), rest))
     }
   }
 }
 
-pub fn string(source: String) -> Parsed(String) {
-  use <- bool.guard(source == "", Error(UnexpectedEndOfFile))
-  do_string(source, "")
-}
-
-fn do_string(source: String, result: String) -> Parsed(String) {
-  case string.split_once(source, "\"") {
-    Ok(#(start, rest)) ->
-      case string.last(start) {
-        Ok("\\") -> do_string(rest, result <> "\"" <> start)
-        _ ->
-          Ok(#(
-            result <> start,
-            // |> string.replace("\\n", "\n")
-            // |> string.replace("\\r", "\r")
-            // |> string.replace("\\t", "\t")
-            // |> string.replace("\\f", "\f")
-            rest,
-          ))
-      }
-    Error(Nil) -> Error(UnterminatedString(source))
-  }
-}
-
-fn number_char(source: String) -> Parsed(String) {
+fn do_string(source: BitArray, acc: List(UtfCodepoint)) -> Parsed(String) {
   case source {
-    "" -> Error(UnexpectedEndOfFile)
-    "." <> rest -> Ok(#(".", rest))
-    "-" <> rest -> Ok(#("-", rest))
-    "0" <> rest -> Ok(#("0", rest))
-    "1" <> rest -> Ok(#("1", rest))
-    "2" <> rest -> Ok(#("2", rest))
-    "3" <> rest -> Ok(#("3", rest))
-    "4" <> rest -> Ok(#("4", rest))
-    "5" <> rest -> Ok(#("5", rest))
-    "6" <> rest -> Ok(#("6", rest))
-    "7" <> rest -> Ok(#("7", rest))
-    "8" <> rest -> Ok(#("8", rest))
-    "9" <> rest -> Ok(#("9", rest))
-    _ ->
-      Error(UnexpectedNumberCharacter(string.first(source) |> result.unwrap("")))
+    <<>> ->
+      Error(UnterminatedString(
+        acc |> list.reverse |> string.from_utf_codepoints,
+      ))
+    <<34, rest:bits>> ->
+      Ok(#(acc |> list.reverse |> string.from_utf_codepoints, rest))
+    <<92, 48, rest:bits>> -> do_string(rest, [utf_codepoint_unsafe(0), ..acc])
+    <<92, 97, rest:bits>> -> do_string(rest, [utf_codepoint_unsafe(7), ..acc])
+    <<92, 98, rest:bits>> -> do_string(rest, [utf_codepoint_unsafe(8), ..acc])
+    <<92, 116, rest:bits>> -> do_string(rest, [utf_codepoint_unsafe(9), ..acc])
+    <<92, 110, rest:bits>> -> do_string(rest, [utf_codepoint_unsafe(10), ..acc])
+    <<92, 118, rest:bits>> -> do_string(rest, [utf_codepoint_unsafe(11), ..acc])
+    <<92, 102, rest:bits>> -> do_string(rest, [utf_codepoint_unsafe(12), ..acc])
+    <<92, 114, rest:bits>> -> do_string(rest, [utf_codepoint_unsafe(13), ..acc])
+    <<92, cp:utf8_codepoint, rest:bits>> -> do_string(rest, [cp, ..acc])
+    <<cp:utf8_codepoint, rest:bits>> -> do_string(rest, [cp, ..acc])
+    source -> Error(InvalidUtf8Character(source))
   }
 }
 
-pub fn try_number(source: String) -> Option(Parsed(SExpr)) {
-  case number_char(source) {
-    Ok(#(char, rest)) -> Some(do_number(rest, char))
-    Error(_) -> None
-  }
-}
-
-fn do_number(source: String, result: String) -> Parsed(SExpr) {
-  case number_char(source) {
-    Ok(#(char, rest)) -> do_number(rest, result <> char)
-    Error(_) -> {
-      case int.parse(result) {
-        Ok(n) -> Ok(#(Int(n), source))
-        Error(Nil) -> {
-          let result = case result {
-            "-." <> rest -> "-0." <> rest
-            "." <> rest -> "0." <> rest
-            result -> result
-          }
-          case float.parse(result) {
+fn do_number(
+  source: BitArray,
+  acc: #(List(UtfCodepoint), Bool),
+) -> Parsed(SExpr) {
+  case source, acc {
+    <<>>, _ -> Error(UnexpectedEndOfFile)
+    <<46 as i, _:bits>>, #(cps, True) ->
+      Error(InvalidNumber(
+        [utf_codepoint_unsafe(i), ..cps]
+        |> list.reverse
+        |> string.from_utf_codepoints,
+      ))
+    <<46 as i, rest:bits>>, #(cps, False) ->
+      do_number(rest, #([utf_codepoint_unsafe(i), ..cps], True))
+    <<48 as i, rest:bits>>, #(cps, has_decimal)
+    | <<49 as i, rest:bits>>, #(cps, has_decimal)
+    | <<50 as i, rest:bits>>, #(cps, has_decimal)
+    | <<51 as i, rest:bits>>, #(cps, has_decimal)
+    | <<52 as i, rest:bits>>, #(cps, has_decimal)
+    | <<53 as i, rest:bits>>, #(cps, has_decimal)
+    | <<54 as i, rest:bits>>, #(cps, has_decimal)
+    | <<55 as i, rest:bits>>, #(cps, has_decimal)
+    | <<56 as i, rest:bits>>, #(cps, has_decimal)
+    | <<57 as i, rest:bits>>, #(cps, has_decimal)
+    -> do_number(rest, #([utf_codepoint_unsafe(i), ..cps], has_decimal))
+    source, #(cps, has_decimal) -> {
+      let str = cps |> list.reverse |> string.from_utf_codepoints
+      case has_decimal {
+        True ->
+          case float.parse(str) {
             Ok(n) -> Ok(#(Float(n), source))
-            Error(Nil) -> Error(InvalidNumber(result))
+            Error(Nil) -> Error(InvalidNumber(str))
+          }
+        False ->
+          case int.parse(str) {
+            Ok(n) -> Ok(#(Int(n), source))
+            Error(Nil) -> Error(InvalidNumber(str))
           }
-        }
       }
     }
   }