From aa6f850b8d2308b99bc13776e6e7937aacb5d711 Mon Sep 17 00:00:00 2001
From: Colin Leroy-Mira <colin@colino.net>
Date: Thu, 11 Jan 2024 19:51:17 +0100
Subject: [PATCH] Rewrite gets in assembler

+19 bytes if used alone, because it pulls in fgets, but as code is
factorized, -128 bytes in programs using both fgets and gets.
---
 libsrc/common/gets.c | 63 --------------------------------------------
 libsrc/common/gets.s | 47 +++++++++++++++++++++++++++++++++
 test/ref/test_gets.c | 46 ++++++++++++++++++++++++++++++++
 3 files changed, 93 insertions(+), 63 deletions(-)
 delete mode 100644 libsrc/common/gets.c
 create mode 100644 libsrc/common/gets.s
 create mode 100644 test/ref/test_gets.c

diff --git a/libsrc/common/gets.c b/libsrc/common/gets.c
deleted file mode 100644
index 2936c70de..000000000
--- a/libsrc/common/gets.c
+++ /dev/null
@@ -1,63 +0,0 @@
-/*
-** gets.c
-**
-** Ullrich von Bassewitz, 11.08.1998
-*/
-
-
-
-#include <stdio.h>
-#include "_file.h"
-
-
-
-/*****************************************************************************/
-/*                                   Code                                    */
-/*****************************************************************************/
-
-
-
-char* __fastcall__ gets (char* s)
-{
-    register char* p = s;
-    int c;
-    unsigned i = 0;
-
-    while (1) {
-
-        /* Get next character */
-        if ((c = fgetc (stdin)) == EOF) {
-            /* Error or EOF */
-            *p = '\0';
-            if (stdin->f_flags & _FERROR) {
-                /* ERROR */
-                return 0;
-            } else {
-                /* EOF */
-                if (i) {
-                    return s;
-                } else {
-                    return 0;
-                }
-            }
-        }
-
-        /* One char more. Newline ends the input */
-        if ((char) c == '\n') {
-            *p = '\0';
-            break;
-        } else {
-            *p = c;
-            ++p;
-            ++i;
-        }
-
-    }
-
-    /* Done */
-    return s;
-}
-
-
-
-
diff --git a/libsrc/common/gets.s b/libsrc/common/gets.s
new file mode 100644
index 000000000..dfaf2def3
--- /dev/null
+++ b/libsrc/common/gets.s
@@ -0,0 +1,47 @@
+;
+; Colin Leroy-Mira, 2024
+;
+; char* __fastcall__ gets (char* s)
+;
+
+        .export         _gets
+        .import         _fgets, _stdin, popax, pushax
+        .importzp       ptr4
+
+_gets:
+        ; Push buffer
+        sta     ptr4
+        stx     ptr4+1
+        jsr     pushax
+
+        ; Push size (there's no limit!)
+        lda     #$FF
+        tax
+        jsr     pushax
+
+        lda     _stdin
+        ldx     _stdin+1
+
+        jsr     _fgets
+
+        ; Check return value
+        bne     :+
+        cpx     #$00
+        bne     :+
+        rts
+
+:       ; At least one byte written.
+        jsr     pushax          ; Store returned pointer
+
+        ; Remove \n if there is one.
+        lda     ptr4            ; _fgets returns with ptr4 at
+        bne     :+              ; end of buffer
+        dec     ptr4+1
+:       dec     ptr4
+        lda     (ptr4),y        ; _fgets returns with Y=0
+        cmp     #$0A
+        bne     :+
+        tya
+        sta     (ptr4),y        ; Set terminator over \n
+
+:       jmp     popax
diff --git a/test/ref/test_gets.c b/test/ref/test_gets.c
new file mode 100644
index 000000000..ee5b6fd58
--- /dev/null
+++ b/test/ref/test_gets.c
@@ -0,0 +1,46 @@
+/*
+  !!DESCRIPTION!! gets test
+  !!LICENCE!!     Public domain
+*/
+
+#include "common.h"
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <ctype.h>
+
+char buf[512];
+
+#define INFILE   "cf.in"
+
+#ifndef __CC65__
+/* Force declaration on host compiler, as gets() is deprecated for
+ * being dangerous as hell */
+char *gets (char *__s);
+#endif
+
+#ifdef NO_OLD_FUNC_DECL
+int main(int argc,char **argv)
+#else
+main(argc, argv)
+int argc;
+char *argv[];
+#endif
+{
+    /* Fake stdin with the reference file */
+    fclose(stdin);
+    stdin = fopen(INFILE, "r");
+    if (stdin == NULL) {
+        return EXIT_FAILURE;
+    }
+
+    while (gets(buf) != NULL)
+    {
+        printf("%s",buf);
+    }
+
+    fclose(stdin);
+    return 0;
+}