From e9ccf5e2f26d57fadb17f7912ecc9b97838b8642 Mon Sep 17 00:00:00 2001
From: Avril <flanchan@cumallover.me>
Date: Tue, 13 Jul 2021 19:27:55 +0100
Subject: [PATCH] Basic implementation of more sensible string mutating
 functions for display format string creation. (`strncat_n()`, `strncpy_n()`.)
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TODO: Better `dest` parameter bounds checking.

Fortune for naka's current commit: Future small blessing − 末小吉
---
 src/display.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/display.c b/src/display.c
index eba9cca..174126f 100644
--- a/src/display.c
+++ b/src/display.c
@@ -11,7 +11,24 @@
 #define FLAGSET(f, flag) (( (f) & (flag) ) == (flag))
 #define DFLAGSET(f, flagname) FLAGSET(f, DISPF_SHOW_ ## flagname)
 
-//TODO: This probably won't work. Write wrappers for strncpy(), strncat() that return number of bytes written isntead of useless pointer that we already have.
+// Returns number of bytes written to `dest`. Otherwise same as `strncpy()`.
+static usize strncpy_n(char*pOUT dest, const char* restrict src, usize n)
+{
+	usize i;
+	for(i=0;i<n;i++)
+		if(! (*dest++ = *src++)) return i;
+	dest[i] = 0;
+	return i;
+}
+
+// Returns number of bytes written to (dest+strlen(dest)). Otherwise same as `strncat()`.
+static inline usize strncat_n(char*pOUT dest, const char* restrict src, usize n)
+{
+	usize dl = strlen(dest);
+	return strncpy_n(dest+dl, src, n);
+}
+
+//TODO: This works, but seems inherantly unsafe. Rewrite to use the above `strn*_n()` functions for better length tracking.
 static usize _display_get_fmt(dispflags_t flags, bool matched, usize _len, char str[pOUT _len])
 {
 	register usize len = _len;