From 1f820d0ae813694c40da9639aa7ec048b79fecbd Mon Sep 17 00:00:00 2001
From: Colin Leroy-Mira <colin@colino.net>
Date: Thu, 11 Jan 2024 19:31:04 +0100
Subject: [PATCH] Rewrite fgets in asm

-104 bytes, -1% cycles
---
 libsrc/apple2/statvfs.s   |   6 +-
 libsrc/common/fgets.c     |  68 ----------------------
 libsrc/common/fgets.s     | 119 ++++++++++++++++++++++++++++++++++++++
 libsrc/runtime/pushptr1.s |  14 +++++
 4 files changed, 135 insertions(+), 72 deletions(-)
 delete mode 100644 libsrc/common/fgets.c
 create mode 100644 libsrc/common/fgets.s
 create mode 100644 libsrc/runtime/pushptr1.s

diff --git a/libsrc/apple2/statvfs.s b/libsrc/apple2/statvfs.s
index 6274bb52b..8fcf46af8 100644
--- a/libsrc/apple2/statvfs.s
+++ b/libsrc/apple2/statvfs.s
@@ -6,7 +6,7 @@
 
         .export         _statvfs
         .import         _dio_query_sectsize
-        .import         mli_file_info, pushax, popax, popptr1
+        .import         mli_file_info, pushax, popax, popptr1, pushptr1
         .include        "zeropage.inc"
         .include        "apple2.inc"
         .include        "errno.inc"
@@ -45,9 +45,7 @@ _statvfs:
         sty     vol_sep         ; Register '/' index
         lda     #$00
         sta     (ptr1),y        ; Cut pathname at first slash
-:       lda     ptr1
-        ldx     ptr1+1
-        jsr     pushax
+:       jsr     pushptr1
 
         jsr     mli_file_info
 
diff --git a/libsrc/common/fgets.c b/libsrc/common/fgets.c
deleted file mode 100644
index 21a991fd6..000000000
--- a/libsrc/common/fgets.c
+++ /dev/null
@@ -1,68 +0,0 @@
-/*
-** Ullrich von Bassewitz, 11.08.1998
-**
-** char* fgets (char* s, int size, FILE* f);
-*/
-
-
-
-#include <stdio.h>
-#include <errno.h>
-#include "_file.h"
-
-
-
-/*****************************************************************************/
-/*                                   Code                                    */
-/*****************************************************************************/
-
-
-
-char* __fastcall__ fgets (char* s, unsigned size, register FILE* f)
-{
-    register char* p = s;
-    unsigned i;
-    int c;
-
-    if (size == 0) {
-        /* Invalid size */
-        return (char*) _seterrno (EINVAL);
-    }
-
-    /* Read input */
-    i = 0;
-    while (--size) {
-
-        /* Get next character */
-        if ((c = fgetc (f)) == EOF) {
-            /* Error or EOF */
-            if ((f->f_flags & _FERROR) != 0 || i == 0) {
-                /* ERROR or EOF on first char */
-                *p = '\0';
-                return 0;
-            } else {
-                /* EOF with data already read */
-                break;
-            }
-        }
-
-        /* One char more */
-        *p = c;
-        ++p;
-        ++i;
-
-        /* Stop at end of line */
-        if ((char)c == '\n') {
-            break;
-        }
-    }
-
-    /* Terminate the string */
-    *p = '\0';
-
-    /* Done */
-    return s;
-}
-
-
-
diff --git a/libsrc/common/fgets.s b/libsrc/common/fgets.s
new file mode 100644
index 000000000..465658191
--- /dev/null
+++ b/libsrc/common/fgets.s
@@ -0,0 +1,119 @@
+;
+; Colin Leroy-Mira, 2024
+;
+; char* __fastcall__ fgets (char* s, unsigned size, register FILE* f)
+;
+
+        .export         _fgets
+        .import         _fgetc, popptr1, pushptr1, popax, pushax, return0, ___errno
+        .importzp       ptr1, ptr4
+
+        .include        "errno.inc"
+        .include        "stdio.inc"
+        .include        "_file.inc"
+
+        .macpack        cpu
+
+terminate_ptr:
+        lda     #$00
+        tax
+        .if (.cpu .bitand ::CPU_ISET_65SC02)
+        sta     (ptr4)
+        .else
+        tay
+        sta     (ptr4),y
+        .endif
+        rts
+
+_fgets:
+        sta     ptr1
+        stx     ptr1+1
+
+        jsr     popax
+        sta     size
+        stx     size+1
+
+        jsr     popax
+        sta     ptr4
+        stx     ptr4+1
+        sta     buf
+        stx     buf+1
+
+        .if (.cpu .bitand ::CPU_ISET_65SC02)
+        stz     didread
+        .else
+        lda     #$00            ; We have read nothing yet
+        sta     didread
+        .endif
+
+        ; Check size
+        lda     size
+        ora     size+1
+        bne     read_loop
+        lda     #EINVAL
+        sta     ___errno
+        jmp     return0
+
+read_loop:
+        lda     size            ; Dec size
+        bne     :+
+        dec     size+1
+:       dec     size
+
+        bne     :+              ; Check bound
+        ldx     size+1
+        beq     done
+
+:       jsr     pushptr1        ; Push ptr1 for backup and load it to AX for fgetc
+        jsr     _fgetc          ; Read a char
+
+        pha
+        jsr     popptr1         ; Get ptr1 back
+        pla
+
+        cpx     #<EOF
+        beq     got_eof
+
+        ldy     #$01
+        sty     didread         ; We read at least one char
+
+        .if (.cpu .bitand ::CPU_ISET_65SC02)
+        sta     (ptr4)
+        .else
+        dey
+        sta     (ptr4),y
+        .endif
+
+        inc     ptr4
+        bne     :+
+        inc     ptr4+1
+
+:       cmp     #$0A            ; Stop at \n
+        beq     done
+
+        clc
+        bcc     read_loop
+
+got_eof:
+        lda     didread
+        beq     stopped_at_first_char
+        ldy     #_FILE::f_flags
+        lda     (ptr1),y
+        and     #_FERROR
+        bne     stopped_at_first_char
+
+done:
+        jsr     terminate_ptr
+        ldx     #>buf
+        lda     #<buf
+        rts
+
+stopped_at_first_char:
+        jmp     terminate_ptr
+
+        .bss
+
+c:      .res 1
+buf:    .res 2
+size:   .res 2
+didread:.res 1
diff --git a/libsrc/runtime/pushptr1.s b/libsrc/runtime/pushptr1.s
new file mode 100644
index 000000000..ca934d6c1
--- /dev/null
+++ b/libsrc/runtime/pushptr1.s
@@ -0,0 +1,14 @@
+;
+; Colin Leroy-Mira, 2024
+;
+; CC65 runtime: Push ptr1 to stack.
+; A/X destroyed (set to ptr1)
+
+        .export         pushptr1
+        .import         pushax
+        .importzp       ptr1
+
+pushptr1:
+        lda     ptr1
+        ldx     ptr1+1
+        jmp     pushax