Lower QR gen memory consumption

rs-matter/src/codec/base38.rs

@@ -120,6 +120,19 @@ pub fn encode(bytes: &[u8]) -> impl Iterator<Item = char> + '_ {
         )
 }
 
+pub fn encode_bits(bits: u32, bits_count: u8) -> impl Iterator<Item = char> {
+    assert!(bits_count <= 24);
+
+    let repeat = match bits_count / 8 {
+        3 => 5,
+        2 => 4,
+        1 => 2,
+        _ => unreachable!(),
+    };
+
+    encode_base38(bits, repeat)
+}
+
 fn encode_base38(mut value: u32, repeat: usize) -> impl Iterator<Item = char> {
     (0..repeat).map(move |_| {
         let remainder = value % RADIX;

rs-matter/src/pairing/mod.rs

@@ -88,10 +88,11 @@ pub fn print_pairing_code_and_qr(
     buf: &mut [u8],
 ) -> Result<(), Error> {
     let pairing_code = compute_pairing_code(comm_data);
-    let qr_code = compute_qr_code_text(dev_det, comm_data, discovery_capabilities, buf)?;
-
     pretty_print_pairing_code(&pairing_code);
-    print_qr_code(qr_code)?;
+
+    let (qr_code, remaining_buf) =
+        compute_qr_code_text(dev_det, comm_data, discovery_capabilities, &[], buf)?;
+    print_qr_code(qr_code, remaining_buf)?;
 
     Ok(())
 }