diff --git a/lib/std/io/io_formatter_private.c3 b/lib/std/io/io_formatter_private.c3
index 1e75c1414..991497aa3 100644
--- a/lib/std/io/io_formatter_private.c3
+++ b/lib/std/io/io_formatter_private.c3
@@ -128,7 +128,7 @@ fn uint simple_atoi(char* buf, usz maxlen, usz* len_ptr) @inline @private
 	while (len < maxlen)
 	{
 		char c = buf[len];
-		if (c < '0' || c > '9') break;
+		if (!c.is_digit()) break;
 		i = i * 10 + c - '0';
 		len++;
 	}
@@ -657,7 +657,7 @@ fn int! printf_parse_format_field(
 	char* format_ptr, usz format_len, usz* index_ptr) @inline @private
 {
 	char c = format_ptr[*index_ptr];
-	if (c >= '0' && c <= '9') return simple_atoi(format_ptr, format_len, index_ptr);
+	if (c.is_digit()) return simple_atoi(format_ptr, format_len, index_ptr);
 	if (c != '*') return 0;
 	printf_advance_format(format_len, index_ptr)!;
 	any val = next_any(args_ptr, args_len, args_index_ptr)!;
diff --git a/lib/std/io/io_stream.c3 b/lib/std/io/io_stream.c3
index 0204bd4e4..a10ac04db 100644
--- a/lib/std/io/io_stream.c3
+++ b/lib/std/io/io_stream.c3
@@ -46,6 +46,8 @@ fn bool Stream.supports_read_from(s) @inline => (bool)s.fns.read_stream_fn;
 fn bool Stream.supports_write_to(s) @inline => (bool)s.fns.write_stream_fn;
 fn bool Stream.supports_pushback_byte(s) @inline => s.fns.pushback_byte_fn || s.fns.seek_fn;
 fn bool Stream.supports_write(s) @inline => s.fns.write_fn || s.fns.write_byte_fn;
+fn bool Stream.supports_read_byte(s) @inline => (bool)s.fns.read_byte_fn;
+fn bool Stream.supports_write_byte(s) @inline => (bool)s.fns.write_byte_fn;
 
 fn void! Stream.destroy(self) @inline @maydiscard
 {
@@ -127,6 +129,13 @@ fn usz! Stream.read_all(self, char[] buffer) @inline
 	return n;
 }
 
+fn usz! Stream.write_all(self, char[] buffer) @inline
+{
+	usz n = self.write(buffer)!;
+	if (n != buffer.len) return IoError.INCOMPLETE_WRITE?;
+	return n;
+}
+
 fn String! Stream.treadline(self) => self.readline(mem::temp()) @inline;
 
 fn String! Stream.readline(self, Allocator* using = mem::heap())