diff --git a/core/io/io.odin b/core/io/io.odin
index bc23c4c86..bfa81d417 100644
--- a/core/io/io.odin
+++ b/core/io/io.odin
@@ -35,13 +35,16 @@ Error :: enum i32 {
 	Invalid_Offset,
 	Invalid_Unread,
 
+	Negative_Read,
+	Negative_Write,
+
 	// Empty is returned when a procedure has not been implemented for an io.Stream
 	Empty = -1,
 }
 
 Close_Proc       :: distinct proc(using s: Stream) -> Error;
 Flush_Proc       :: distinct proc(using s: Stream) -> Error;
-Seek_Proc        :: distinct proc(using s: Stream, offset: i64, whence: Seek_From) -> (i64, Error);
+Seek_Proc        :: distinct proc(using s: Stream, offset: i64, whence: Seek_From) -> (n: i64, err: Error);
 Size_Proc        :: distinct proc(using s: Stream) -> i64;
 Read_Proc        :: distinct proc(using s: Stream, p: []byte) -> (n: int, err: Error);
 Read_At_Proc     :: distinct proc(using s: Stream, p: []byte, off: i64) -> (n: int, err: Error);
@@ -120,7 +123,10 @@ destroy :: proc(s: Stream) -> Error {
 	if s.stream_vtable != nil && s.impl_destroy != nil {
 		return s->impl_destroy();
 	}
-	return close_err;
+	if close_err != .None {
+		return close_err;
+	}
+	return .Empty;
 }
 
 read :: proc(s: Reader, p: []byte) -> (n: int, err: Error) {
@@ -364,6 +370,11 @@ write_string :: proc(s: Writer, str: string) -> (n: int, err: Error) {
 }
 
 write_rune :: proc(s: Writer, r: rune) -> (n: int, err: Error) {
+	if r < utf8.RUNE_SELF {
+		err = write_byte(s, byte(r));
+		n = 1 if err == nil else 0;
+		return;
+	}
 	buf, w := utf8.encode_rune(r);
 	return write(s, buf[:w]);
 }
diff --git a/core/io/util.odin b/core/io/util.odin
index b618a6c23..2036aa570 100644
--- a/core/io/util.odin
+++ b/core/io/util.odin
@@ -48,7 +48,11 @@ _tee_reader_vtable := &Stream_VTable{
 	},
 };
 
-// tee_reader
+// tee_reader returns a Reader that writes to 'w' what it reads from 'r'
+// All reads from 'r' performed through it are matched with a corresponding write to 'w'
+// There is no internal buffering done
+// The write must complete before th read completes
+// Any error encountered whilst writing is reported as a 'read' error
 // tee_reader must call io.destroy when done with
 tee_reader :: proc(r: Reader, w: Writer, allocator := context.allocator) -> (out: Reader) {
 	t := new(Tee_Reader, allocator);
@@ -61,9 +65,8 @@ tee_reader :: proc(r: Reader, w: Writer, allocator := context.allocator) -> (out
 }
 
 
-// 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.
+// 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 {
 	r: Reader, // underlying reader
@@ -72,7 +75,7 @@ Limited_Reader :: struct {
 
 @(private)
 _limited_reader_vtable := &Stream_VTable{
-	impl_read = proc(using s: Stream, p: []byte) -> (n: int, err: Error) {
+	impl_read = proc(s: Stream, p: []byte) -> (n: int, err: Error) {
 		l := (^Limited_Reader)(s.stream_data);
 		if l.n <= 0 {
 			return 0, .EOF;
@@ -106,3 +109,84 @@ inline_limited_reader :: proc(l: ^Limited_Reader, r: Reader, n: i64) -> Reader {
 	l.n = n;
 	return limited_reader_to_reader(l);
 }
+
+// Section_Reader implements read, seek, and read_at on a section of an underlying Reader_At
+Section_Reader :: struct {
+	r: Reader_At,
+	base:  i64,
+	off:   i64,
+	limit: i64,
+}
+
+init_section_reader :: proc(s: ^Section_Reader, r: Reader_At, off: i64, n: i64) {
+	s.r = r;
+	s.off = off;
+	s.limit = off + n;
+	return;
+}
+section_reader_to_stream :: proc(s: ^Section_Reader) -> (out: Stream) {
+	out.stream_data = s;
+	out.stream_vtable = _section_reader_vtable;
+	return;
+}
+
+@(private)
+_section_reader_vtable := &Stream_VTable{
+	impl_read = proc(stream: Stream, p: []byte) -> (n: int, err: Error) {
+		s := (^Section_Reader)(stream.stream_data);
+		if s.off >= s.limit {
+			return 0, .EOF;
+		}
+		p := p;
+		if max := s.limit - s.off; i64(len(p)) > max {
+			p = p[0:max];
+		}
+		n, err = read_at(s.r, p, s.off);
+		s.off += i64(n);
+		return;
+	},
+	impl_read_at = proc(stream: Stream, p: []byte, off: i64) -> (n: int, err: Error) {
+		s := (^Section_Reader)(stream.stream_data);
+		p, off := p, off;
+
+		if off < 0 || off >= s.limit - s.base {
+			return 0, .EOF;
+		}
+		off += s.base;
+		if max := s.limit - off; i64(len(p)) > max {
+			p = p[0:max];
+			n, err = read_at(s.r, p, off);
+			if err == nil {
+				err = .EOF;
+			}
+			return;
+		}
+		return read_at(s.r, p, off);
+	},
+	impl_seek = proc(stream: Stream, offset: i64, whence: Seek_From) -> (n: i64, err: Error) {
+		s := (^Section_Reader)(stream.stream_data);
+
+		offset := offset;
+		switch whence {
+		case:
+			return 0, .Invalid_Whence;
+		case .Start:
+			offset += s.base;
+		case .Current:
+			offset += s.off;
+		case .End:
+			offset += s.limit;
+		}
+		if offset < s.base {
+			return 0, .Invalid_Offset;
+		}
+		s.off = offset;
+		n = offset - s.base;
+		return;
+	},
+	impl_size = proc(stream: Stream) -> i64 {
+		s := (^Section_Reader)(stream.stream_data);
+		return s.limit - s.base;
+	},
+};
+
diff --git a/core/strings/builder.odin b/core/strings/builder.odin
index 3506b4bc8..6ca5be27d 100644
--- a/core/strings/builder.odin
+++ b/core/strings/builder.odin
@@ -74,6 +74,16 @@ _builder_stream_vtable := &io.Stream_VTable{
 		}
 		return nil;
 	},
+	impl_size = proc(s: io.Stream) -> i64 {
+		b := (^Builder)(s.stream_data);
+		return i64(len(b.buf));
+	},
+	impl_destroy = proc(s: io.Stream) -> io.Error {
+		b := (^Builder)(s.stream_data);
+		flush_builder(b);
+		delete(b.buf);
+		return .None;
+	},
 };
 
 to_stream :: proc(b: ^Builder) -> io.Stream {
@@ -173,42 +183,23 @@ write_bytes :: proc(b: ^Builder, x: []byte) -> (n: int) {
 	return;
 }
 
-write_rune :: proc{
-	write_rune_builder,
-	write_rune_writer,
-};
-write_rune_builder :: proc(b: ^Builder, r: rune) -> int {
-	return write_rune_writer(to_writer(b), r);
-}
-write_rune_writer :: proc(w: io.Writer, r: rune) -> int {
-	if r < utf8.RUNE_SELF {
-		return _write_byte(w, byte(r));
-	}
-
-	s, n := utf8.encode_rune(r);
-	n, _ = io.write(w, s[:n]);
-	return n;
+write_rune_builder :: proc(b: ^Builder, r: rune) -> (int, io.Error) {
+	return io.write_rune(to_writer(b), r);
 }
 
 
-
-write_quoted_rune :: proc{
-	write_quoted_rune_builder,
-	write_quoted_rune_writer,
-};
-
 write_quoted_rune_builder :: proc(b: ^Builder, r: rune) -> (n: int) {
-	return write_quoted_rune_writer(to_writer(b), r);
+	return write_quoted_rune(to_writer(b), r);
 }
 
 @(private)
-_write_byte :: proc(w: io.Writer, r: byte) -> int {
-	err := io.write_byte(w, r);
+_write_byte :: proc(w: io.Writer, c: byte) -> int {
+	err := io.write_byte(w, c);
 	return 1 if err == nil else 0;
 }
 
-write_quoted_rune_writer :: proc(w: io.Writer, r: rune) -> (n: int) {
 
+write_quoted_rune :: proc(w: io.Writer, r: rune) -> (n: int) {
 	quote := byte('\'');
 	n += _write_byte(w, quote);
 	buf, width := utf8.encode_rune(r);
@@ -328,7 +319,8 @@ write_encoded_rune_writer :: proc(w: io.Writer, r: rune, write_quote := true) ->
 			case 2: n += write_string(w, s);
 			}
 		} else {
-			n += write_rune(w, r);
+			rn, _ := io.write_rune(w, r);
+			n += rn;
 		}
 
 	}
diff --git a/core/strings/conversion.odin b/core/strings/conversion.odin
index 41add2778..c03bed86a 100644
--- a/core/strings/conversion.odin
+++ b/core/strings/conversion.odin
@@ -1,5 +1,6 @@
 package strings
 
+import "core:io"
 import "core:unicode"
 import "core:unicode/utf8"
 
@@ -61,7 +62,7 @@ to_lower :: proc(s: string, allocator := context.allocator) -> string {
 	b: Builder;
 	init_builder(&b, 0, len(s), allocator);
 	for r in s {
-		write_rune(&b, unicode.to_lower(r));
+		write_rune_builder(&b, unicode.to_lower(r));
 	}
 	return to_string(b);
 }
@@ -69,7 +70,7 @@ to_upper :: proc(s: string, allocator := context.allocator) -> string {
 	b: Builder;
 	init_builder(&b, 0, len(s), allocator);
 	for r in s {
-		write_rune(&b, unicode.to_upper(r));
+		write_rune_builder(&b, unicode.to_upper(r));
 	}
 	return to_string(b);
 }
@@ -101,7 +102,7 @@ is_separator :: proc(r: rune) -> bool {
 }
 
 
-string_case_iterator :: proc(b: ^Builder, s: string, callback: proc(b: ^Builder, prev, curr, next: rune)) {
+string_case_iterator :: proc(w: io.Writer, s: string, callback: proc(w: io.Writer, prev, curr, next: rune)) {
 	prev, curr: rune;
 	for next in s {
 		if curr == 0 {
@@ -110,14 +111,14 @@ string_case_iterator :: proc(b: ^Builder, s: string, callback: proc(b: ^Builder,
 			continue;
 		}
 
-		callback(b, prev, curr, next);
+		callback(w, prev, curr, next);
 
 		prev = curr;
 		curr = next;
 	}
 
 	if len(s) > 0 {
-		callback(b, prev, curr, 0);
+		callback(w, prev, curr, 0);
 	}
 }
 
@@ -128,15 +129,16 @@ to_camel_case :: proc(s: string, allocator := context.allocator) -> string {
 	s = trim_space(s);
 	b: Builder;
 	init_builder(&b, 0, len(s), allocator);
+	w := to_writer(&b);
 
-	string_case_iterator(&b, s, proc(b: ^Builder, prev, curr, next: rune) {
+	string_case_iterator(w, s, proc(w: io.Writer, prev, curr, next: rune) {
 		if !is_delimiter(curr) {
 			if is_delimiter(prev) {
-				write_rune(b, unicode.to_upper(curr));
+				io.write_rune(w, unicode.to_upper(curr));
 			} else if unicode.is_lower(prev) {
-				write_rune(b, curr);
+				io.write_rune(w, curr);
 			} else {
-				write_rune(b, unicode.to_lower(curr));
+				io.write_rune(w, unicode.to_lower(curr));
 			}
 		}
 	});
@@ -150,15 +152,16 @@ to_pascal_case :: proc(s: string, allocator := context.allocator) -> string {
 	s = trim_space(s);
 	b: Builder;
 	init_builder(&b, 0, len(s), allocator);
+	w := to_writer(&b);
 
-	string_case_iterator(&b, s, proc(b: ^Builder, prev, curr, next: rune) {
+	string_case_iterator(w, s, proc(w: io.Writer, prev, curr, next: rune) {
 		if !is_delimiter(curr) {
 			if is_delimiter(prev) || prev == 0 {
-				write_rune(b, unicode.to_upper(curr));
+				io.write_rune(w, unicode.to_upper(curr));
 			} else if unicode.is_lower(prev) {
-				write_rune(b, curr);
+				io.write_rune(w, curr);
 			} else {
-				write_rune(b, unicode.to_lower(curr));
+				io.write_rune(w, unicode.to_lower(curr));
 			}
 		}
 	});
@@ -171,6 +174,7 @@ to_delimiter_case :: proc(s: string, delimiter: rune, all_upper_case: bool, allo
 	s = trim_space(s);
 	b: Builder;
 	init_builder(&b, 0, len(s), allocator);
+	w := to_writer(&b);
 
 	adjust_case := unicode.to_upper if all_upper_case else unicode.to_lower;
 
@@ -179,15 +183,15 @@ to_delimiter_case :: proc(s: string, delimiter: rune, all_upper_case: bool, allo
 	for next in s {
 		if is_delimiter(curr) {
 			if !is_delimiter(prev) {
-				write_rune(&b, delimiter);
+				io.write_rune(w, delimiter);
 			}
 		} else if unicode.is_upper(curr) {
 			if unicode.is_lower(prev) || (unicode.is_upper(prev) && unicode.is_lower(next)) {
-				write_rune(&b, delimiter);
+				io.write_rune(w, delimiter);
 			}
-			write_rune(&b, adjust_case(curr));
+			io.write_rune(w, adjust_case(curr));
 		} else if curr != 0 {
-			write_rune(&b, adjust_case(curr));
+			io.write_rune(w, adjust_case(curr));
 		}
 
 		prev = curr;
@@ -196,9 +200,9 @@ to_delimiter_case :: proc(s: string, delimiter: rune, all_upper_case: bool, allo
 
 	if len(s) > 0 {
 		if unicode.is_upper(curr) && unicode.is_lower(prev) && prev != 0 {
-			write_rune(&b, delimiter);
+			io.write_rune(w, delimiter);
 		}
-		write_rune(&b, adjust_case(curr));
+		io.write_rune(w, adjust_case(curr));
 	}
 
 	return to_string(b);
@@ -229,21 +233,22 @@ to_ada_case :: proc(s: string, allocator := context.allocator) -> string {
 	s = trim_space(s);
 	b: Builder;
 	init_builder(&b, 0, len(s), allocator);
+	w := to_writer(&b);
 
 	prev, curr: rune;
 
 	for next in s {
 		if is_delimiter(curr) {
 			if !is_delimiter(prev) {
-				write_rune(&b, delimiter);
+				io.write_rune(w, delimiter);
 			}
 		} else if unicode.is_upper(curr) {
 			if unicode.is_lower(prev) || (unicode.is_upper(prev) && unicode.is_lower(next)) {
-				write_rune(&b, delimiter);
+				io.write_rune(w, delimiter);
 			}
-			write_rune(&b, unicode.to_upper(curr));
+			io.write_rune(w, unicode.to_upper(curr));
 		} else if curr != 0 {
-			write_rune(&b, unicode.to_lower(curr));
+			io.write_rune(w, unicode.to_lower(curr));
 		}
 
 		prev = curr;
@@ -252,10 +257,10 @@ to_ada_case :: proc(s: string, allocator := context.allocator) -> string {
 
 	if len(s) > 0 {
 		if unicode.is_upper(curr) && unicode.is_lower(prev) && prev != 0 {
-			write_rune(&b, delimiter);
-			write_rune(&b, unicode.to_upper(curr));
+			io.write_rune(w, delimiter);
+			io.write_rune(w, unicode.to_upper(curr));
 		} else {
-			write_rune(&b, unicode.to_lower(curr));
+			io.write_rune(w, unicode.to_lower(curr));
 		}
 	}
 
diff --git a/core/strings/strings.odin b/core/strings/strings.odin
index 0306defc8..4b0230f59 100644
--- a/core/strings/strings.odin
+++ b/core/strings/strings.odin
@@ -1,5 +1,6 @@
 package strings
 
+import "core:io"
 import "core:mem"
 import "core:unicode/utf8"
 
@@ -814,6 +815,7 @@ expand_tabs :: proc(s: string, tab_size: int, allocator := context.allocator) ->
 
 	b: Builder;
 	init_builder(&b, allocator);
+	writer := to_writer(&b);
 	str := s;
 	column: int;
 
@@ -824,7 +826,7 @@ expand_tabs :: proc(s: string, tab_size: int, allocator := context.allocator) ->
 			expand := tab_size - column%tab_size;
 
 			for i := 0; i < expand; i += 1 {
-				write_byte(&b, ' ');
+				io.write_byte(writer, ' ');
 			}
 
 			column += expand;
@@ -835,7 +837,7 @@ expand_tabs :: proc(s: string, tab_size: int, allocator := context.allocator) ->
 				column += w;
 			}
 
-			write_rune(&b, r);
+			io.write_rune(writer, r);
 		}
 
 		str = str[w:];
@@ -874,9 +876,11 @@ centre_justify :: proc(str: string, length: int, pad: string, allocator := conte
 	init_builder(&b, allocator);
 	grow_builder(&b, len(str) + (remains/pad_len + 1)*len(pad));
 
-	write_pad_string(&b, pad, pad_len, remains/2);
-	write_string(&b, str);
-	write_pad_string(&b, pad, pad_len, (remains+1)/2);
+	w := to_writer(&b);
+
+	write_pad_string(w, pad, pad_len, remains/2);
+	io.write_string(w, str);
+	write_pad_string(w, pad, pad_len, (remains+1)/2);
 
 	return to_string(b);
 }
@@ -895,8 +899,10 @@ left_justify :: proc(str: string, length: int, pad: string, allocator := context
 	init_builder(&b, allocator);
 	grow_builder(&b, len(str) + (remains/pad_len + 1)*len(pad));
 
-	write_string(&b, str);
-	write_pad_string(&b, pad, pad_len, remains);
+	w := to_writer(&b);
+
+	io.write_string(w, str);
+	write_pad_string(w, pad, pad_len, remains);
 
 	return to_string(b);
 }
@@ -915,8 +921,10 @@ right_justify :: proc(str: string, length: int, pad: string, allocator := contex
 	init_builder(&b, allocator);
 	grow_builder(&b, len(str) + (remains/pad_len + 1)*len(pad));
 
-	write_pad_string(&b, pad, pad_len, remains);
-	write_string(&b, str);
+	w := to_writer(&b);
+
+	write_pad_string(w, pad, pad_len, remains);
+	io.write_string(w, str);
 
 	return to_string(b);
 }
@@ -925,19 +933,19 @@ right_justify :: proc(str: string, length: int, pad: string, allocator := contex
 
 
 @private
-write_pad_string :: proc(b: ^Builder, pad: string, pad_len, remains: int) {
+write_pad_string :: proc(w: io.Writer, pad: string, pad_len, remains: int) {
 	repeats := remains / pad_len;
 
 	for i := 0; i < repeats; i += 1 {
-		write_string(b, pad);
+		io.write_string(w, pad);
 	}
 
 	n := remains % pad_len;
 	p := pad;
 
 	for i := 0; i < n; i += 1 {
-		r, w := utf8.decode_rune_in_string(p);
-		write_rune(b, r);
-		p = p[w:];
+		r, width := utf8.decode_rune_in_string(p);
+		io.write_rune(w, r);
+		p = p[width:];
 	}
 }