fdputd(3)

lib/libio.c

@@ -1,30 +1,72 @@
-#ifndef _LIBIO_H
+#include <unistd.h>
 
-#	define _LIBIO_H
-
-int
-fdputs(int fd, const char *s){
+static int
+_strlen(char *s){
 	int i;
-	int r;
 
 	for(i = 0; s[i] != '\0'; ++i);
 
-	/* DANGER */
+	return i;
+}
+
+static int write1(int fd, int c){
+	int *s;
+	s = &c;
+	while(write(fd, s, 1) != 1);
+}
+
+int fdputd(int fd, int d){
+	int r;
+	int s;
+
+	r = 0;
+	/* Just an implementation looking for a math person to improve it... */
+	if(d < 100){
+		s = d < 10 ? 1 : 10;
+		goto put;
+	}
+	for(s = 10; d > (s *= 10););
+put:	while(s > 0){
+		r += write1(fd, (d - (d % s)) / s + '0', 1);
+		if((s /= 10) == 0)
+			r += write1(fd, "\n", 1);
+	}
+}
+
+int
+fdputs(int fd, char *s){
+	int i;
+	int r;
+
+	i = _strlen(s);
+	r = 0;
+
+	/* RACE CONDITION */
+	/* This leaves s as an invalid string while the write(2) syscall is
+	 * performed, which can take a non-trivial amount of time. This
+	 * implementation is unsuitable when s is shared between threads or
+	 * whatever the CS term for that is. */
 	s[i] = '\n';
-	r = write(fd, s, i + 1);
+	for(
+		r = 0;
+		(r += write(fd, s, i + 1)) < i + 1;
+		s += r, i -= r
+	);
 	s[i] = '\0';
-	/* /danger */
 
 	return r;
 }
 
-#	ifndef _STDIO_H
-
-int
-puts(const char *s){
-	return fdputs(1, s);
+/* Another possible implementation would take char **s and leave *s at the next
+ * non-digit. But that's less simple; just while(isdigit(*s)) ++s;. */
+unsigned int
+parse_uint(char *s){
+	unsigned int r;
+	for(
+		r = 0;
+		isdigit(*s);
+		r = r * 10 + *s - '0',
+			++s
+	);
+	return r;
 }
-
-#	endif /* ifndef _STDIO_H */
-
-#endif /* ifndef _LIBIO_H */

lib/libio.h

@@ -0,0 +1,6 @@
+#ifndef _LIBIO_H
+#	define _LIBIO_H
+int fdputd(int fd, int d);
+int fdputs(int fd, char *s);
+int parse_uint(char *s);
+#endif /* ifndef _LIBIO_H */