Add package io

core/io/util.odin

@@ -0,0 +1,90 @@
+package io
+
+import "core:runtime"
+
+@(private)
+Tee_Reader :: struct {
+	using stream: Stream,
+	r: Reader,
+	w: Writer,
+	allocator: runtime.Allocator,
+}
+
+@(private)
+_tee_reader_vtable := &Stream_VTable{
+	impl_read = proc(s: Stream, p: []byte) -> (n: int, err: Error) {
+		t := (^Tee_Reader)(s.data);
+		n, err = read(t.r, p);
+		if n > 0 {
+			if wn, werr := write(t.w, p[:n]); werr != nil {
+				return wn, werr;
+			}
+		}
+		return;
+	},
+	impl_destroy = proc(s: Stream) -> Error {
+		t := (^Tee_Reader)(s.data);
+		allocator := t.allocator;
+		free(t, allocator);
+		return .None;
+	},
+};
+
+// tee_reader
+// tee_reader must call io.destroy when done with
+tee_reader :: proc(r: Reader, w: Writer, allocator := context.allocator) -> Reader {
+	t := new(Tee_Reader, allocator);
+	t.r, t.w = r, w;
+	t.allocator = allocator;
+	t.data = t;
+	t.vtable = _tee_reader_vtable;
+	res, _ := to_reader(t^);
+	return res;
+}
+
+
+// A Limited_Reader reads from r but limits the amount of
+// data returned to just n bytes. Each call to read
+// updates n to reflect the new amount remaining.
+// read returns EOF when n <= 0 or when the underlying r returns EOF.
+Limited_Reader :: struct {
+	using stream: Stream,
+	r: Reader, // underlying reader
+	n: i64,    // max_bytes
+}
+
+@(private)
+_limited_reader_vtable := &Stream_VTable{
+	impl_read = proc(using s: Stream, p: []byte) -> (n: int, err: Error) {
+		l := (^Limited_Reader)(s.data);
+		if l.n <= 0 {
+			return 0, .EOF;
+		}
+		p := p;
+		if i64(len(p)) > l.n {
+			p = p[0:l.n];
+		}
+		n, err = read(l.r, p);
+		l.n -= i64(n);
+		return;
+	},
+};
+
+new_limited_reader :: proc(r: Reader, n: i64) -> ^Limited_Reader {
+	l := new(Limited_Reader);
+	l.vtable = _limited_reader_vtable;
+	l.data = l;
+	l.r = r;
+	l.n = n;
+	return l;
+}
+
+@(private="package")
+inline_limited_reader :: proc(l: ^Limited_Reader, r: Reader, n: i64) -> Reader {
+	l.vtable = _limited_reader_vtable;
+	l.data = l;
+	l.r = r;
+	l.n = n;
+	res, _ := to_reader(l^);
+	return res;
+}