introduce os.EOF and io.ErrUnexpectedEOF.

remove io.ErrEOF.
rename io.FullRead to io.ReadFull, to match
   ReadAtLeast and ReadAll.
remove io.FullReader, because it is now unused.

R=r
DELTA=295  (88 added, 105 deleted, 102 changed)
OCL=30544
CL=30588

23 files changed, 147 insertions, 164 deletions

diff --git a/src/pkg/archive/tar/untar.go b/src/pkg/archive/tar/untar.go
index 8446cc215..3770d1da3 100644
--- a/src/pkg/archive/tar/untar.go
+++ b/src/pkg/archive/tar/untar.go
@@ -186,13 +186,13 @@ func (s *slicer) next(n int) (b []byte) {
 func (tr *Reader) readHeader() *Header {
 	header := make([]byte, blockSize);
 	var n int;
-	if n, tr.err = io.FullRead(tr.r, header); tr.err != nil {
+	if n, tr.err = io.ReadFull(tr.r, header); tr.err != nil {
 		return nil
 	}
 
 	// Two blocks of zero bytes marks the end of the archive.
 	if bytes.Equal(header, zeroBlock[0:blockSize]) {
-		if n, tr.err = io.FullRead(tr.r, header); tr.err != nil {
+		if n, tr.err = io.ReadFull(tr.r, header); tr.err != nil {
 			return nil
 		}
 		if !bytes.Equal(header, zeroBlock[0:blockSize]) {
diff --git a/src/pkg/archive/tar/untar_test.go b/src/pkg/archive/tar/untar_test.go
index d692e1ae2..3241c171e 100644
--- a/src/pkg/archive/tar/untar_test.go
+++ b/src/pkg/archive/tar/untar_test.go
@@ -124,7 +124,7 @@ func TestPartialRead(t *testing.T) {
 		t.Fatalf("Didn't get first file: %v", err);
 	}
 	buf := make([]byte, 4);
-	if n, err := io.FullRead(tr, buf); err != nil {
+	if n, err := io.ReadFull(tr, buf); err != nil {
 		t.Fatalf("Unexpected error: %v", err);
 	}
 	if expected := io.StringBytes("Kilt"); !bytes.Equal(buf, expected) {
@@ -137,7 +137,7 @@ func TestPartialRead(t *testing.T) {
 		t.Fatalf("Didn't get second file: %v", err);
 	}
 	buf = make([]byte, 6);
-	if n, err := io.FullRead(tr, buf); err != nil {
+	if n, err := io.ReadFull(tr, buf); err != nil {
 		t.Fatalf("Unexpected error: %v", err);
 	}
 	if expected := io.StringBytes("Google"); !bytes.Equal(buf, expected) {
diff --git a/src/pkg/bufio/bufio.go b/src/pkg/bufio/bufio.go
index 7bfbb089f..520fd3afc 100644
--- a/src/pkg/bufio/bufio.go
+++ b/src/pkg/bufio/bufio.go
@@ -113,7 +113,7 @@ func (b *Reader) fill() os.Error {
 // It returns the number of bytes read into p.
 // If nn < len(p), also returns an error explaining
 // why the read is short.  At EOF, the count will be
-// zero and err will be io.ErrEOF.
+// zero and err will be os.EOF.
 func (b *Reader) Read(p []byte) (nn int, err os.Error) {
 	nn = 0;
 	for len(p) > 0 {
@@ -131,18 +131,12 @@ func (b *Reader) Read(p []byte) (nn int, err os.Error) {
 				if b.err != nil {
 					return nn, b.err
 				}
-				if n == 0 {
-					return nn, io.ErrEOF
-				}
 				continue;
 			}
 			b.fill();
 			if b.err != nil {
 				return nn, b.err
 			}
-			if b.w == b.r {
-				return nn, io.ErrEOF
-			}
 		}
 		if n > b.w - b.r {
 			n = b.w - b.r
@@ -164,9 +158,6 @@ func (b *Reader) ReadByte() (c byte, err os.Error) {
 		if b.err != nil {
 			return 0, b.err
 		}
-		if b.w == b.r {
-			return 0, io.ErrEOF
-		}
 	}
 	c = b.buf[b.r];
 	b.r++;
@@ -205,9 +196,6 @@ func (b *Reader) ReadRune() (rune int, size int, err os.Error) {
 		}
 		if b.w - b.r == n {
 			// no bytes read
-			if b.r == b.w {
-				return 0, 0, io.ErrEOF
-			}
 			break;
 		}
 	}
@@ -259,12 +247,9 @@ func (b *Reader) ReadLineSlice(delim byte) (line []byte, err os.Error) {
 		n := b.Buffered();
 		b.fill();
 		if b.err != nil {
-			return nil, b.err
-		}
-		if b.Buffered() == n {	// no data added; end of file
 			line := b.buf[b.r:b.w];
 			b.r = b.w;
-			return line, io.ErrEOF
+			return line, b.err
 		}
 
 		// Search new part of buffer
diff --git a/src/pkg/bufio/bufio_test.go b/src/pkg/bufio/bufio_test.go
index 6e5135df7..dfb9e3ac8 100644
--- a/src/pkg/bufio/bufio_test.go
+++ b/src/pkg/bufio/bufio_test.go
@@ -46,7 +46,7 @@ func readBytes(buf *Reader) string {
 	nb := 0;
 	for {
 		c, e := buf.ReadByte();
-		if e == io.ErrEOF {
+		if e == os.EOF {
 			break
 		}
 		if e != nil {
@@ -88,7 +88,7 @@ func readLines(b *Reader) string {
 	s := "";
 	for {
 		s1, e := b.ReadLineString('\n', true);
-		if e == io.ErrEOF {
+		if e == os.EOF {
 			break
 		}
 		if e != nil {
@@ -106,7 +106,7 @@ func reads(buf *Reader, m int) string {
 	for {
 		n, e := buf.Read(b[nb:nb+m]);
 		nb += n;
-		if e == io.ErrEOF {
+		if e == os.EOF {
 			break
 		}
 	}
diff --git a/src/pkg/compress/flate/inflate.go b/src/pkg/compress/flate/inflate.go
index c07c94c6e..1e81aff73 100644
--- a/src/pkg/compress/flate/inflate.go
+++ b/src/pkg/compress/flate/inflate.go
@@ -543,11 +543,8 @@ func (f *inflater) dataBlock() os.Error {
 	f.b = 0;
 
 	// Length then ones-complement of length.
-	nr, err := f.r.Read(f.buf[0:4]);
+	nr, err := io.ReadFull(f.r, f.buf[0:4]);
 	f.roffset += int64(nr);
-	if nr < 4 && err == nil {
-		err = io.ErrEOF;
-	}
 	if err != nil {
 		return &ReadError{f.roffset, err};
 	}
@@ -564,11 +561,8 @@ func (f *inflater) dataBlock() os.Error {
 		if m > n {
 			m = n;
 		}
-		m, err := f.r.Read(f.hist[f.hp:f.hp+m]);
+		m, err := io.ReadFull(f.r, f.hist[f.hp:f.hp+m]);
 		f.roffset += int64(m);
-		if m == 0 && err == nil {
-			err = io.ErrEOF;
-		}
 		if err != nil {
 			return &ReadError{f.roffset, err};
 		}
diff --git a/src/pkg/compress/gzip/gunzip.go b/src/pkg/compress/gzip/gunzip.go
index 32cc3ecb0..f170e8bcd 100644
--- a/src/pkg/compress/gzip/gunzip.go
+++ b/src/pkg/compress/gzip/gunzip.go
@@ -116,11 +116,8 @@ func (z *GzipInflater) read2() (uint32, os.Error) {
 }
 
 func (z *GzipInflater) readHeader(save bool) os.Error {
-	n, err := io.FullRead(z.r, z.buf[0:10]);
+	n, err := io.ReadFull(z.r, z.buf[0:10]);
 	if err != nil {
-		if n != 0 && err == io.ErrEOF {
-			return HeaderError;
-		}
 		return err;
 	}
 	if z.buf[0] != gzipID1 || z.buf[1] != gzipID2 || z.buf[2] != gzipDeflate {
@@ -134,7 +131,7 @@ func (z *GzipInflater) readHeader(save bool) os.Error {
 	}
 	z.digest.Reset();
 	z.digest.Write(z.buf[0:10]);
-	
+
 	if z.flg & flagExtra != 0{
 		n, err := z.read2();
 		if err != nil {
@@ -142,7 +139,7 @@ func (z *GzipInflater) readHeader(save bool) os.Error {
 		}
 		data := make([]byte, n);
 		var nn int;
-		if nn, err = io.FullRead(z.r, data); err != nil {
+		if nn, err = io.ReadFull(z.r, data); err != nil {
 			return err;
 		}
 		if save {
@@ -196,17 +193,13 @@ func (z *GzipInflater) Read(p []byte) (n int, err os.Error) {
 	n, err = z.inflater.Read(p);
 	z.digest.Write(p[0:n]);
 	z.size += uint32(n);
-	if n != 0 || err != nil {
+	if n != 0 || err != os.EOF {
 		z.err = err;
 		return;
 	}
 
 	// Finished file; check checksum + size.
-	if _, err := io.FullRead(z.r, z.buf[0:8]); err != nil {
-		z.err = err;
-		return 0, err;
-	}
-	if err != nil {
+	if _, err := io.ReadFull(z.r, z.buf[0:8]); err != nil {
 		z.err = err;
 		return 0, err;
 	}
@@ -218,12 +211,7 @@ func (z *GzipInflater) Read(p []byte) (n int, err os.Error) {
 	}
 
 	// File is ok; is there another?
-	switch err = z.readHeader(false); {
-	case err == io.ErrEOF:
-		err = nil;
-		z.eof = true;
-		return;
-	case err != nil:
+	if err = z.readHeader(false); err != nil {
 		z.err = err;
 		return;
 	}
diff --git a/src/pkg/compress/gzip/gunzip_test.go b/src/pkg/compress/gzip/gunzip_test.go
index a481de927..7771b3dae 100644
--- a/src/pkg/compress/gzip/gunzip_test.go
+++ b/src/pkg/compress/gzip/gunzip_test.go
@@ -14,6 +14,7 @@ import (
 
 type gzipTest struct {
 	name string;
+	desc string;
 	raw string;
 	gzip []byte;
 	err os.Error;
@@ -22,6 +23,7 @@ type gzipTest struct {
 var gzipTests = []gzipTest {
 	gzipTest {	// has 1 empty fixed-huffman block
 		"empty.txt",
+		"empty.txt",
 		"",
 		[]byte {
 			0x1f, 0x8b, 0x08, 0x08, 0xf7, 0x5e, 0x14, 0x4a,
@@ -33,6 +35,7 @@ var gzipTests = []gzipTest {
 	},
 	gzipTest {	// has 1 non-empty fixed huffman block
 		"hello.txt",
+		"hello.txt",
 		"hello world\n",
 		[]byte {
 			0x1f, 0x8b, 0x08, 0x08, 0xc8, 0x58, 0x13, 0x4a,
@@ -46,6 +49,7 @@ var gzipTests = []gzipTest {
 	},
 	gzipTest {	// concatenation
 		"hello.txt",
+		"hello.txt x2",
 		"hello world\n"
 		"hello world\n",
 		[]byte {
@@ -66,6 +70,7 @@ var gzipTests = []gzipTest {
 	},
 	gzipTest {	// has dynamic huffman blocks
 		"gettysburg",
+		"gettysburg",
 		"  Four score and seven years ago our fathers brought forth on\n"
 		"this continent, a new nation, conceived in Liberty, and dedicated\n"
 		"to the proposition that all men are created equal.\n"
@@ -203,6 +208,7 @@ var gzipTests = []gzipTest {
 	},
 	gzipTest {	// has 1 non-empty fixed huffman block then garbage
 		"hello.txt",
+		"hello.txt + garbage",
 		"hello world\n",
 		[]byte {
 			0x1f, 0x8b, 0x08, 0x08, 0xc8, 0x58, 0x13, 0x4a,
@@ -210,12 +216,27 @@ var gzipTests = []gzipTest {
 			0x74, 0x78, 0x74, 0x00, 0xcb, 0x48, 0xcd, 0xc9,
 			0xc9, 0x57, 0x28, 0xcf, 0x2f, 0xca, 0x49, 0xe1,
 			0x02, 0x00, 0x2d, 0x3b, 0x08, 0xaf, 0x0c, 0x00,
-			0x00, 0x00, 'g', 'a', 'r', 'b', 'a', 'g', 'e', '!',
+			0x00, 0x00, 'g', 'a', 'r', 'b', 'a', 'g', 'e', '!', '!', '!',
 		},
 		HeaderError,
 	},
+	gzipTest {	// has 1 non-empty fixed huffman block not enough header
+		"hello.txt",
+		"hello.txt + garbage",
+		"hello world\n",
+		[]byte {
+			0x1f, 0x8b, 0x08, 0x08, 0xc8, 0x58, 0x13, 0x4a,
+			0x00, 0x03, 0x68, 0x65, 0x6c, 0x6c, 0x6f, 0x2e,
+			0x74, 0x78, 0x74, 0x00, 0xcb, 0x48, 0xcd, 0xc9,
+			0xc9, 0x57, 0x28, 0xcf, 0x2f, 0xca, 0x49, 0xe1,
+			0x02, 0x00, 0x2d, 0x3b, 0x08, 0xaf, 0x0c, 0x00,
+			0x00, 0x00, gzipID1,
+		},
+		io.ErrUnexpectedEOF,
+	},
 	gzipTest {	// has 1 non-empty fixed huffman block but corrupt checksum
 		"hello.txt",
+		"hello.txt + corrupt checksum",
 		"hello world\n",
 		[]byte {
 			0x1f, 0x8b, 0x08, 0x08, 0xc8, 0x58, 0x13, 0x4a,
@@ -229,6 +250,7 @@ var gzipTests = []gzipTest {
 	},
 	gzipTest {	// has 1 non-empty fixed huffman block but corrupt size
 		"hello.txt",
+		"hello.txt + corrupt size",
 		"hello world\n",
 		[]byte {
 			0x1f, 0x8b, 0x08, 0x08, 0xc8, 0x58, 0x13, 0x4a,
@@ -257,7 +279,7 @@ func TestGzipInflater(t *testing.T) {
 		b.Reset();
 		n, err := io.Copy(gzip, b);
 		if err != tt.err {
-			t.Errorf("%s: io.Copy: %s want %s", tt.name, err, tt.err);
+			t.Errorf("%s: io.Copy: %v want %v", tt.name, err, tt.err);
 		}
 		s := string(b.Data());
 		if s != tt.raw {
diff --git a/src/pkg/crypto/block/eax.go b/src/pkg/crypto/block/eax.go
index 7e1d7475c..301564074 100644
--- a/src/pkg/crypto/block/eax.go
+++ b/src/pkg/crypto/block/eax.go
@@ -150,7 +150,7 @@ func (cr *cmacReader) Read(p []byte) (n int, err os.Error) {
 	tag := cr.tag;
 	if len(tag) < cap(tag) {
 		nt := len(tag);
-		nn, err1 := io.FullRead(cr.r, tag[nt:cap(tag)]);
+		nn, err1 := io.ReadFull(cr.r, tag[nt:cap(tag)]);
 		tag = tag[0:nt+nn];
 		cr.tag = tag;
 		if err1 != nil {
diff --git a/src/pkg/crypto/block/ecb.go b/src/pkg/crypto/block/ecb.go
index 141d38cc8..d1f1dee0e 100644
--- a/src/pkg/crypto/block/ecb.go
+++ b/src/pkg/crypto/block/ecb.go
@@ -106,9 +106,9 @@ func (x *ecbDecrypter) Read(p []byte) (n int, err os.Error) {
 
 	// Read and decrypt directly in caller's buffer.
 	n, err = io.ReadAtLeast(x.r, p, x.blockSize);
-	if err == io.ErrEOF && n == 0 {
-		// EOF is okay on block boundary
-		err = nil;
+	if err == os.EOF && n > 0 {
+		// EOF is only okay on block boundary
+		err = os.ErrorString("block fragment at EOF during decryption");
 		return;
 	}
 	var i int;
diff --git a/src/pkg/exec/exec_test.go b/src/pkg/exec/exec_test.go
index a1bb1f50e..9a9fca2e7 100644
--- a/src/pkg/exec/exec_test.go
+++ b/src/pkg/exec/exec_test.go
@@ -18,16 +18,15 @@ func TestRunCat(t *testing.T) {
 	}
 	io.WriteString(cmd.Stdin, "hello, world\n");
 	cmd.Stdin.Close();
-	var buf [64]byte;
-	n, err1 := io.FullRead(cmd.Stdout, &buf);
-	if err1 != nil && err1 != io.ErrEOF {
-		t.Fatalf("reading from /bin/cat: %v", err1);
+	buf, err := io.ReadAll(cmd.Stdout);
+	if err != nil {
+		t.Fatalf("reading from /bin/cat: %v", err);
 	}
-	if string(buf[0:n]) != "hello, world\n" {
-		t.Fatalf("reading from /bin/cat: got %q", buf[0:n]);
+	if string(buf) != "hello, world\n" {
+		t.Fatalf("reading from /bin/cat: got %q", buf);
 	}
-	if err1 = cmd.Close(); err1 != nil {
-		t.Fatalf("closing /bin/cat: %v", err1);
+	if err = cmd.Close(); err != nil {
+		t.Fatalf("closing /bin/cat: %v", err);
 	}
 }
 
@@ -37,15 +36,14 @@ func TestRunEcho(t *testing.T) {
 	if err != nil {
 		t.Fatalf("opencmd /bin/echo: %v", err);
 	}
-	var buf [64]byte;
-	n, err1 := io.FullRead(cmd.Stdout, &buf);
-	if err1 != nil && err1 != io.ErrEOF {
-		t.Fatalf("reading from /bin/echo: %v", err1);
+	buf, err := io.ReadAll(cmd.Stdout);
+	if err != nil {
+		t.Fatalf("reading from /bin/echo: %v", err);
 	}
-	if string(buf[0:n]) != "hello world\n" {
-		t.Fatalf("reading from /bin/echo: got %q", buf[0:n]);
+	if string(buf) != "hello world\n" {
+		t.Fatalf("reading from /bin/echo: got %q", buf);
 	}
-	if err1 = cmd.Close(); err1 != nil {
-		t.Fatalf("closing /bin/echo: %v", err1);
+	if err = cmd.Close(); err != nil {
+		t.Fatalf("closing /bin/echo: %v", err);
 	}
 }
diff --git a/src/pkg/http/client_test.go b/src/pkg/http/client_test.go
index 6cde4a41c..ca4235879 100644
--- a/src/pkg/http/client_test.go
+++ b/src/pkg/http/client_test.go
@@ -25,11 +25,7 @@ func TestClient(t *testing.T) {
 		r.Body.Close();
 	}
 
-	// TODO: io.ErrEOF check is needed because we're sometimes getting
-	// this error when nothing is actually wrong.  rsc suspects a bug
-	// in bufio.  Can remove the ErrEOF check once the bug is fixed
-	// (expected to occur within a few weeks of this writing, 6/9/09).
-	if err != nil && err != io.ErrEOF {
+	if err != nil {
 		t.Errorf("Error fetching URL: %v", err);
 	} else {
 		s := string(b);
diff --git a/src/pkg/http/fs.go b/src/pkg/http/fs.go
index 108734c47..fd18096f0 100644
--- a/src/pkg/http/fs.go
+++ b/src/pkg/http/fs.go
@@ -142,7 +142,7 @@ func serveFileInternal(c *Conn, r *Request, name string, redirect bool) {
 	} else {
 		// read first chunk to decide between utf-8 text and binary
 		var buf [1024]byte;
-		n, err := io.FullRead(f, &buf);
+		n, err := io.ReadFull(f, &buf);
 		b := buf[0:n];
 		if isText(b) {
 			c.SetHeader("Content-Type", "text-plain; charset=utf-8");
diff --git a/src/pkg/http/request.go b/src/pkg/http/request.go
index 5356f5525..a0207ea71 100644
--- a/src/pkg/http/request.go
+++ b/src/pkg/http/request.go
@@ -151,8 +151,8 @@ func (req *Request) write(w io.Writer) os.Error {
 	io.WriteString(w, "\r\n");
 
 	if req.Body != nil {
-		nCopied, err := io.Copy(req.Body, w);
-		if err != nil && err != io.ErrEOF {
+		_, err := io.Copy(req.Body, w);
+		if err != nil {
 			return err;
 		}
 	}
diff --git a/src/pkg/io/bytebuffer.go b/src/pkg/io/bytebuffer.go
index 000c05352..11c8a1a87 100644
--- a/src/pkg/io/bytebuffer.go
+++ b/src/pkg/io/bytebuffer.go
@@ -103,10 +103,10 @@ func (b *ByteBuffer) Read(p []byte) (n int, err os.Error) {
 }
 
 // ReadByte reads and returns the next byte from the buffer.
-// If no byte is available, it returns error ErrEOF.
+// If no byte is available, it returns error os.EOF.
 func (b *ByteBuffer) ReadByte() (c byte, err os.Error) {
 	if b.off >= len(b.buf) {
-		return 0, ErrEOF;
+		return 0, os.EOF;
 	}
         c = b.buf[b.off];
 	b.off++;
diff --git a/src/pkg/io/io.go b/src/pkg/io/io.go
index ba0449ac1..d01f9ee3d 100644
--- a/src/pkg/io/io.go
+++ b/src/pkg/io/io.go
@@ -19,18 +19,25 @@ type Error struct {
 	os.ErrorString
 }
 
-// ErrEOF means that data was expected, but a read got EOF instead.
-var ErrEOF os.Error = &Error{"EOF"}
-
 // ErrShortWrite means that a write accepted fewer bytes than requested
 // but failed to return an explicit error.
 var ErrShortWrite os.Error = &Error{"short write"}
 
+// ErrUnexpectedEOF means that os.EOF was encountered in the
+// middle of reading a fixed-size block or data structure.
+var ErrUnexpectedEOF os.Error = &Error{"unexpected EOF"}
 
 // Reader is the interface that wraps the basic Read method.
-// An implementation of Read is allowed to use all of p for
-// scratch space during the call, even if it eventually returns
-// n < len(p).
+//
+// Read reads up to len(p) bytes into p.  It returns the number of bytes
+// read and any error encountered.  Even if Read returns n < len(p),
+// it may use all of p as scratch space during the call.
+// If some data is available but not len(p) bytes, Read conventionally
+// returns what is available rather than block waiting for more.
+//
+// At the end of the input stream, Read returns 0, os.EOF.
+// Read may return a non-zero number of bytes with a non-nil err.
+// In particular, a Read that exhausts the input may return n > 0, os.EOF.
 type Reader interface {
 	Read(p []byte) (n int, err os.Error);
 }
@@ -84,8 +91,11 @@ func WriteString(w Writer, s string) (n int, err os.Error) {
 	return w.Write(StringBytes(s))
 }
 
-// ReadAtLeast reads r into buf until at least min bytes have been read,
-// or until EOF or error.
+// ReadAtLeast reads from r into buf until it has read at least min bytes.
+// It returns the number of bytes copied and an error if fewer bytes were read.
+// The error is os.EOF only if no bytes were read.
+// If an EOF happens after reading fewer than min bytes,
+// ReadAtLeast returns ErrUnexpectedEOF.
 func ReadAtLeast(r Reader, buf []byte, min int) (n int, err os.Error) {
 	n = 0;
 	for n < min {
@@ -94,44 +104,27 @@ func ReadAtLeast(r Reader, buf []byte, min int) (n int, err os.Error) {
 			n += nn
 		}
 		if e != nil {
+			if e == os.EOF && n > 0 {
+				e = ErrUnexpectedEOF;
+			}
 			return n, e
 		}
-		if nn <= 0 {
-			return n, ErrEOF	// no error but insufficient data
-		}
 	}
 	return n, nil
 }
 
-// FullRead reads r until the buffer buf is full, or until EOF or error.
-func FullRead(r Reader, buf []byte) (n int, err os.Error) {
-	// TODO(rsc): 6g bug prevents obvious return
+// ReadFull reads exactly len(buf) bytes from r into buf.
+// It returns the number of bytes copied and an error if fewer bytes were read.
+// The error is os.EOF only if no bytes were read.
+// If an EOF happens after reading some but not all the bytes,
+// ReadFull returns ErrUnexpectedEOF.
+func ReadFull(r Reader, buf []byte) (n int, err os.Error) {
+	// TODO(rsc): 6g bug keeps us from writing the obvious 1-liner
 	n, err = ReadAtLeast(r, buf, len(buf));
 	return;
 }
 
-// Convert something that implements Read into something
-// whose Reads are always FullReads
-type fullRead struct {
-	r	Reader;
-}
-
-func (fr *fullRead) Read(p []byte) (n int, err os.Error) {
-	n, err = FullRead(fr.r, p);
-	return n, err
-}
-
-// MakeFullReader takes r, an implementation of Read, and returns an object
-// that still implements Read but always calls FullRead underneath.
-func MakeFullReader(r Reader) Reader {
-	if fr, ok := r.(*fullRead); ok {
-		// already a fullRead
-		return r
-	}
-	return &fullRead{r}
-}
-
-// Copy n copies n bytes (or until EOF is reached) from src to dst.
+// Copyn copies n bytes (or until an error) from src to dst.
 // It returns the number of bytes copied and the error, if any.
 func Copyn(src Reader, dst Writer, n int64) (written int64, err os.Error) {
 	buf := make([]byte, 32*1024);
@@ -151,7 +144,7 @@ func Copyn(src Reader, dst Writer, n int64) (written int64, err os.Error) {
 				break;
 			}
 			if nr != nw {
-				err = os.EIO;
+				err = ErrShortWrite;
 				break;
 			}
 		}
@@ -159,16 +152,13 @@ func Copyn(src Reader, dst Writer, n int64) (written int64, err os.Error) {
 			err = er;
 			break;
 		}
-		if nr == 0 {
-			err = ErrEOF;
-			break;
-		}
 	}
 	return written, err
 }
 
-// Copy copies from src to dst until EOF is reached.
-// It returns the number of bytes copied and the error, if any.
+// Copy copies from src to dst until either EOF is reached
+// on src or an error occurs.  It returns the number of bytes
+// copied and the error, if any.
 func Copy(src Reader, dst Writer) (written int64, err os.Error) {
 	buf := make([]byte, 32*1024);
 	for {
@@ -183,15 +173,15 @@ func Copy(src Reader, dst Writer) (written int64, err os.Error) {
 				break;
 			}
 			if nr != nw {
-				err = os.EIO;
+				err = ErrShortWrite;
 				break;
 			}
 		}
-		if er != nil {
-			err = er;
+		if er == os.EOF {
 			break;
 		}
-		if nr == 0 {
+		if er != nil {
+			err = er;
 			break;
 		}
 	}
@@ -208,6 +198,9 @@ type ByteReader struct {
 func (r ByteReader) Read(p []byte) (int, os.Error) {
 	n := len(p);
 	b := r.Data;
+	if len(b) == 0 {
+		return 0, os.EOF;
+	}
 	if n > len(b) {
 		n = len(b);
 	}
diff --git a/src/pkg/io/pipe.go b/src/pkg/io/pipe.go
index 1a443ddce..729094fde 100644
--- a/src/pkg/io/pipe.go
+++ b/src/pkg/io/pipe.go
@@ -104,6 +104,9 @@ func (p *pipe) CloseReader(rerr os.Error) os.Error {
 }
 
 func (p *pipe) CloseWriter(werr os.Error) os.Error {
+	if werr == nil {
+		werr = os.EOF;
+	}
 	if p == nil || p.wclosed {
 		return os.EINVAL;
 	}
diff --git a/src/pkg/io/pipe_test.go b/src/pkg/io/pipe_test.go
index 277f44525..02d5013f3 100644
--- a/src/pkg/io/pipe_test.go
+++ b/src/pkg/io/pipe_test.go
@@ -45,13 +45,14 @@ func reader(t *testing.T, r Reader, c chan int) {
 	var buf = make([]byte, 64);
 	for {
 		n, err := r.Read(buf);
+		if err == os.EOF {
+			c <- 0;
+			break;
+		}
 		if err != nil {
 			t.Errorf("read: %v", err);
 		}
 		c <- n;
-		if n == 0 {
-			break;
-		}
 	}
 }
 
@@ -101,7 +102,7 @@ func TestPipe3(t *testing.T) {
 	tot := 0;
 	for n := 1; n <= 256; n *= 2 {
 		nn, err := r.Read(rdat[tot:tot+n]);
-		if err != nil {
+		if err != nil && err != os.EOF {
 			t.Fatalf("read: %v", err);
 		}
 
@@ -111,6 +112,9 @@ func TestPipe3(t *testing.T) {
 			expect = 1;
 		} else if n == 256 {
 			expect = 0;
+			if err != os.EOF {
+				t.Fatalf("read at end: %v", err);
+			}
 		}
 		if nn != expect {
 			t.Fatalf("read %d, expected %d, got %d", n, expect, nn);
@@ -183,8 +187,12 @@ func TestPipeReadClose(t *testing.T) {
 		var buf = make([]byte, 64);
 		n, err := r.Read(buf);
 		<-c;
-		if err != tt.err {
-			t.Errorf("read from closed pipe: %v want %v", err, tt.err);
+		want := tt.err;
+		if want == nil {
+			want = os.EOF;
+		}
+		if err != want {
+			t.Errorf("read from closed pipe: %v want %v", err, want);
 		}
 		if n != 0 {
 			t.Errorf("read on closed pipe returned %d", n);
diff --git a/src/pkg/net/dialgoogle_test.go b/src/pkg/net/dialgoogle_test.go
index 1e0c0aaf0..3792195ce 100644
--- a/src/pkg/net/dialgoogle_test.go
+++ b/src/pkg/net/dialgoogle_test.go
@@ -24,7 +24,7 @@ func fetchGoogle(t *testing.T, fd net.Conn, network, addr string) {
 	n, err := fd.Write(req);
 
 	buf := make([]byte, 1000);
-	n, err = io.FullRead(fd, buf);
+	n, err = io.ReadFull(fd, buf);
 
 	if n < 1000 {
 		t.Errorf("fetchGoogle: short HTTP read from %s %s - %v", network, addr, err);
diff --git a/src/pkg/net/parse.go b/src/pkg/net/parse.go
index de47cb812..7d5dd8f88 100644
--- a/src/pkg/net/parse.go
+++ b/src/pkg/net/parse.go
@@ -50,7 +50,7 @@ func (f *file) readLine() (s string, ok bool) {
 	}
 	if len(f.data) < cap(f.data) {
 		ln := len(f.data);
-		n, err := io.FullRead(f.file, f.data[ln:cap(f.data)]);
+		n, err := io.ReadFull(f.file, f.data[ln:cap(f.data)]);
 		if n >= 0 {
 			f.data = f.data[0:ln+n];
 		}
diff --git a/src/pkg/os/file.go b/src/pkg/os/file.go
index 1562b1b0e..5b6115932 100644
--- a/src/pkg/os/file.go
+++ b/src/pkg/os/file.go
@@ -97,9 +97,21 @@ func (file *File) Close() Error {
 	return err;
 }
 
+type eofError int
+func (eofError) String() string {
+	return "EOF"
+}
+
+// EOF is the Error returned by Read when no more input is available.
+// Functions should return EOF only to signal a graceful end of input.
+// If the EOF occurs unexpectedly in a structured data stream,
+// the appropriate error is either io.ErrUnexpectedEOF or some other error
+// giving more detail.
+var EOF Error = eofError(0)
+
 // Read reads up to len(b) bytes from the File.
 // It returns the number of bytes read and an Error, if any.
-// EOF is signaled by a zero count with a nil Error.
+// EOF is signaled by a zero count with err set to EOF.
 // TODO(r): Add Pread, Pwrite (maybe ReadAt, WriteAt).
 func (file *File) Read(b []byte) (ret int, err Error) {
 	if file == nil {
@@ -109,6 +121,9 @@ func (file *File) Read(b []byte) (ret int, err Error) {
 	if n < 0 {
 		n = 0;
 	}
+	if n == 0 && e == 0 {
+		return 0, EOF
+	}
 	return n, ErrnoToError(e);
 }
 
diff --git a/src/pkg/os/os_test.go b/src/pkg/os/os_test.go
index 6a132f343..77b69447d 100644
--- a/src/pkg/os/os_test.go
+++ b/src/pkg/os/os_test.go
@@ -40,13 +40,13 @@ func size(name string, t *testing.T) uint64 {
 	len := 0;
 	for {
 		n, e := file.Read(&buf);
-		if n < 0 || e != nil {
-			t.Fatal("read failed:", err);
-		}
-		if n == 0 {
+		len += n;
+		if e == EOF {
 			break
 		}
-		len += n;
+		if e != nil {
+			t.Fatal("read failed:", err);
+		}
 	}
 	return uint64(len)
 }
diff --git a/src/pkg/strconv/fp_test.go b/src/pkg/strconv/fp_test.go
index 60d7ce6cf..f1993bb7e 100644
--- a/src/pkg/strconv/fp_test.go
+++ b/src/pkg/strconv/fp_test.go
@@ -105,7 +105,7 @@ func TestFp(t *testing.T) {
 	lineno := 0;
 	for {
 		line, err2 := b.ReadLineString('\n', false);
-		if err2 == io.ErrEOF {
+		if err2 == os.EOF {
 			break;
 		}
 		if err2 != nil {
diff --git a/src/pkg/time/zoneinfo.go b/src/pkg/time/zoneinfo.go
index 751afc931..c4fe814c3 100644
--- a/src/pkg/time/zoneinfo.go
+++ b/src/pkg/time/zoneinfo.go
@@ -16,7 +16,6 @@ import (
 )
 
 const (
-	maxFileSize = 8192;	// actual files are closer to 1K
 	headerSize = 4+16+4*7;
 
 	zoneDir = "/usr/share/zoneinfo/";
@@ -29,7 +28,6 @@ type TimeZoneError struct {
 
 var errShort = TimeZoneError{ "time: short zone file" }
 var errInvalid = TimeZoneError{ "time: invalid zone file" }
-var errLong = TimeZoneError{ "time: zone file too long" }
 
 // Simple I/O interface to binary blob of data.
 type data struct {
@@ -206,25 +204,8 @@ func parseinfo(bytes []byte) (zt []zonetime, err os.Error) {
 	return zt, nil
 }
 
-func readfile(name string, max int) (p []byte, err os.Error) {
-	f, e := os.Open(name, os.O_RDONLY, 0);
-	if e != nil {
-		return nil, e;
-	}
-	p = make([]byte, max);
-	n, err1 := io.FullRead(f, p);
-	f.Close();
-	if err1 == nil {	// too long
-		return nil, errLong;
-	}
-	if err1 != io.ErrEOF {
-		return nil, err1;
-	}
-	return p[0:n], nil;
-}
-
 func readinfofile(name string) ([]zonetime, os.Error) {
-	buf, err := readfile(name, maxFileSize);
+	buf, err := io.ReadFile(name);
 	if err != nil {
 		goto Error;
 	}