perf: use memory efficient char counting

README.md

@@ -10,7 +10,7 @@
 
 
 [Demo](examples/arduino/README.md) of CLI running on Arduino Nano.
-Memory usage: 17KiB ROM, 500B static RAM. Most of static RAM is used by help strings.
+Memory usage: 15KiB of ROM and 0.5KiB of static RAM. Most of static RAM is used by help strings.
 
 ![Arduino Demo](examples/arduino/demo.gif)
 

embedded-cli/src/editor.rs

@@ -95,7 +95,7 @@ impl<B: Buffer> Editor<B> {
 
     pub fn insert(&mut self, text: &str) -> Option<&str> {
         let remaining = self.buffer.len() - self.valid;
-        let chars = text.chars().count();
+        let chars = utils::char_count(text);
         let text = text.as_bytes();
         if remaining < text.len() {
             //TODO: try to grow buffer
@@ -118,8 +118,7 @@ impl<B: Buffer> Editor<B> {
     }
 
     pub fn len(&self) -> usize {
-        //TODO: use another usize to store len
-        self.text().chars().count()
+        utils::char_count(self.text())
     }
 
     pub fn move_left(&mut self) -> bool {

embedded-cli/src/utils.rs

@@ -23,6 +23,17 @@ pub fn char_byte_index(text: &str, char_index: usize) -> Option<usize> {
     None
 }
 
+pub fn char_count(text: &str) -> usize {
+    let mut accum = Utf8Accum::default();
+    let mut count = 0;
+    for &b in text.as_bytes() {
+        if accum.push_byte(b).is_some() {
+            count += 1;
+        }
+    }
+    count
+}
+
 /// Function to rotate `buf` by `mid` elements
 ///
 /// Not using `core::slice::rotate_left` since it
@@ -112,4 +123,11 @@ mod tests {
             assert_eq!(utils::char_byte_index(text, pos), expected)
         }
     }
+
+    #[rstest]
+    #[case("abcdef")]
+    #[case("abcd абв 佐佗佟𑿁 𑿆𑿌")]
+    fn char_count(#[case] text: &str) {
+        assert_eq!(utils::char_count(text), text.chars().count())
+    }
 }

examples/arduino/README.md

@@ -2,7 +2,7 @@
 
 This example shows how to build cli with Arduino Nano.
 Another Arduino can also be used, but you will have to tweak configs.
-Example uses ~17KiB of ROM and ~0.5KiB of static RAM.
+Example uses ~15KiB of ROM and ~0.5KiB of static RAM.
 Most of RAM is taken by derived implementations for help and autocomplete
 that don't use progmem. In future this should be fixed.
 
@@ -23,7 +23,7 @@ tio /dev/ttyUSB0 --map ODELBS
 
 # Memory usage
 
-Memory usage might vary depending on compiler version and build environment.
+Memory usage might vary depending on compiler version, build environment and library version.
 To find out total ROM usage run:
 
 ```shell
@@ -33,13 +33,13 @@ cargo bloat --release
 Example output:
 ```
 File  .text    Size        Crate Name
-1.7%  52.5%  8.7KiB  arduino_cli arduino_cli::__avr_device_rt_main
-0.2%   7.5%  1.3KiB         core <core::iter::adapters::skip::Skip<I> as core::iter::traits::iterator::Iterator>::next
-0.2%   6.0%   1016B embedded_cli embedded_cli::autocomplete::Autocompletion::merge_autocompletion
-0.1%   4.3%    738B embedded_cli embedded_cli::token::Tokens::remove
-0.1%   3.2%    538B embedded_cli embedded_cli::token::Tokens::new
-0.8%  23.7%  3.9KiB              And 27 smaller methods. Use -n N to show more.
-3.2% 100.0% 16.6KiB              .text section size, the file size is 517.3KiB
+1.6%  54.5%  8.1KiB  arduino_cli arduino_cli::try_run
+0.2%   6.7%   1016B embedded_cli embedded_cli::autocomplete::Autocompletion::merge_autocompletion
+0.1%   3.6%    538B embedded_cli embedded_cli::token::Tokens::new
+0.1%   3.5%    530B embedded_cli embedded_cli::help::HelpRequest::from_tokens
+0.1%   3.1%    472B embedded_cli embedded_cli::token::Tokens::remove
+0.8%  25.4%  3.8KiB              And 34 smaller methods. Use -n N to show more.
+3.0% 100.0% 14.8KiB              .text section size, the file size is 498.4KiB
 ```
 
 To find total static memory usage:
@@ -54,7 +54,7 @@ cargo build --release && \
 
 Example output:
 ```
-RAM usage: 489
+RAM usage: 506
 ```
 
 To further analyze used space: