From 965524520500cc6a81dddb95ca427cb1a6830f96 Mon Sep 17 00:00:00 2001
From: "B. Watson" <urchlay@slackware.uk>
Date: Mon, 6 Apr 2026 07:41:01 -0400
Subject: Rewrite txbuf_append_str() in asm. 6826 bytes free.

---
 src/main.c  |  6 ------
 src/txbuf.s | 29 +++++++++++++++++++++++++----
 2 files changed, 25 insertions(+), 10 deletions(-)

(limited to 'src')

diff --git a/src/main.c b/src/main.c
index 66ced7f..1f533b3 100644
--- a/src/main.c
+++ b/src/main.c
@@ -33,12 +33,6 @@ void txbuf_init(void) {
 	txbuflen = tx_buf[0] = 0;
 }
 
-void txbuf_append_str(const char *str) {
-	while(*str) {
-		txbuf_append_chr(*str++);
-	}
-}
-
 void txbuf_append_str2(const char *s1, const char *s2) {
 	txbuf_append_str(s1);
 	txbuf_append_str(s2);
diff --git a/src/txbuf.s b/src/txbuf.s
index 4783660..bc1d1c2 100644
--- a/src/txbuf.s
+++ b/src/txbuf.s
@@ -7,7 +7,7 @@
  tx_buf = $a200 ; MUST agree with src/rxtxbuf.h!
 
  .import _txbuflen
- .export _txbuf_append_chr
+ .export _txbuf_append_chr, _txbuf_append_str
  .importzp sreg ; avoid ptr1 & friends, callers may use
 
 _txbuf_append_chr:
@@ -23,7 +23,28 @@ _txbuf_append_chr:
  txa
  sta (sreg),y
  inc _txbuflen
- bne @ret
+ bne ret
  inc _txbuflen+1
-@ret:
- rts
+ret:
+ rts ; always returns with Y == 0
+
+;; void txbuf_append_str(const char *str) {
+;; 	while(*str) {
+;; 		txbuf_append_chr(*str++);
+;; 	}
+;; }
+
+; compiles to 52 bytes.
+; this routine is 22 bytes, ~57% smaller.
+_txbuf_append_str:
+ sta sreg+2
+ stx sreg+3
+ ldy #0
+@loop:
+ lda (sreg+2),y
+ beq ret
+ jsr _txbuf_append_chr
+ inc sreg+2
+ bne @loop
+ inc sreg+3
+ bne @loop
-- 
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