1 files changed, 268 insertions, 0 deletions
diff --git a/src/testing/iotest/reader.go b/src/testing/iotest/reader.go
new file mode 100644
index 0000000..770d87f
--- /dev/null
+++ b/src/testing/iotest/reader.go
@@ -0,0 +1,268 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package iotest implements Readers and Writers useful mainly for testing.
+package iotest
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+)
+
+// OneByteReader returns a Reader that implements
+// each non-empty Read by reading one byte from r.
+func OneByteReader(r io.Reader) io.Reader { return &oneByteReader{r} }
+
+type oneByteReader struct {
+	r io.Reader
+}
+
+func (r *oneByteReader) Read(p []byte) (int, error) {
+	if len(p) == 0 {
+		return 0, nil
+	}
+	return r.r.Read(p[0:1])
+}
+
+// HalfReader returns a Reader that implements Read
+// by reading half as many requested bytes from r.
+func HalfReader(r io.Reader) io.Reader { return &halfReader{r} }
+
+type halfReader struct {
+	r io.Reader
+}
+
+func (r *halfReader) Read(p []byte) (int, error) {
+	return r.r.Read(p[0 : (len(p)+1)/2])
+}
+
+// DataErrReader changes the way errors are handled by a Reader. Normally, a
+// Reader returns an error (typically EOF) from the first Read call after the
+// last piece of data is read. DataErrReader wraps a Reader and changes its
+// behavior so the final error is returned along with the final data, instead
+// of in the first call after the final data.
+func DataErrReader(r io.Reader) io.Reader { return &dataErrReader{r, nil, make([]byte, 1024)} }
+
+type dataErrReader struct {
+	r      io.Reader
+	unread []byte
+	data   []byte
+}
+
+func (r *dataErrReader) Read(p []byte) (n int, err error) {
+	// loop because first call needs two reads:
+	// one to get data and a second to look for an error.
+	for {
+		if len(r.unread) == 0 {
+			n1, err1 := r.r.Read(r.data)
+			r.unread = r.data[0:n1]
+			err = err1
+		}
+		if n > 0 || err != nil {
+			break
+		}
+		n = copy(p, r.unread)
+		r.unread = r.unread[n:]
+	}
+	return
+}
+
+// ErrTimeout is a fake timeout error.
+var ErrTimeout = errors.New("timeout")
+
+// TimeoutReader returns ErrTimeout on the second read
+// with no data. Subsequent calls to read succeed.
+func TimeoutReader(r io.Reader) io.Reader { return &timeoutReader{r, 0} }
+
+type timeoutReader struct {
+	r     io.Reader
+	count int
+}
+
+func (r *timeoutReader) Read(p []byte) (int, error) {
+	r.count++
+	if r.count == 2 {
+		return 0, ErrTimeout
+	}
+	return r.r.Read(p)
+}
+
+// ErrReader returns an io.Reader that returns 0, err from all Read calls.
+func ErrReader(err error) io.Reader {
+	return &errReader{err: err}
+}
+
+type errReader struct {
+	err error
+}
+
+func (r *errReader) Read(p []byte) (int, error) {
+	return 0, r.err
+}
+
+type smallByteReader struct {
+	r   io.Reader
+	off int
+	n   int
+}
+
+func (r *smallByteReader) Read(p []byte) (int, error) {
+	if len(p) == 0 {
+		return 0, nil
+	}
+	r.n = r.n%3 + 1
+	n := r.n
+	if n > len(p) {
+		n = len(p)
+	}
+	n, err := r.r.Read(p[0:n])
+	if err != nil && err != io.EOF {
+		err = fmt.Errorf("Read(%d bytes at offset %d): %v", n, r.off, err)
+	}
+	r.off += n
+	return n, err
+}
+
+// TestReader tests that reading from r returns the expected file content.
+// It does reads of different sizes, until EOF.
+// If r implements io.ReaderAt or io.Seeker, TestReader also checks
+// that those operations behave as they should.
+//
+// If TestReader finds any misbehaviors, it returns an error reporting them.
+// The error text may span multiple lines.
+func TestReader(r io.Reader, content []byte) error {
+	if len(content) > 0 {
+		n, err := r.Read(nil)
+		if n != 0 || err != nil {
+			return fmt.Errorf("Read(0) = %d, %v, want 0, nil", n, err)
+		}
+	}
+
+	data, err := io.ReadAll(&smallByteReader{r: r})
+	if err != nil {
+		return err
+	}
+	if !bytes.Equal(data, content) {
+		return fmt.Errorf("ReadAll(small amounts) = %q\n\twant %q", data, content)
+	}
+	n, err := r.Read(make([]byte, 10))
+	if n != 0 || err != io.EOF {
+		return fmt.Errorf("Read(10) at EOF = %v, %v, want 0, EOF", n, err)
+	}
+
+	if r, ok := r.(io.ReadSeeker); ok {
+		// Seek(0, 1) should report the current file position (EOF).
+		if off, err := r.Seek(0, 1); off != int64(len(content)) || err != nil {
+			return fmt.Errorf("Seek(0, 1) from EOF = %d, %v, want %d, nil", off, err, len(content))
+		}
+
+		// Seek backward partway through file, in two steps.
+		// If middle == 0, len(content) == 0, can't use the -1 and +1 seeks.
+		middle := len(content) - len(content)/3
+		if middle > 0 {
+			if off, err := r.Seek(-1, 1); off != int64(len(content)-1) || err != nil {
+				return fmt.Errorf("Seek(-1, 1) from EOF = %d, %v, want %d, nil", -off, err, len(content)-1)
+			}
+			if off, err := r.Seek(int64(-len(content)/3), 1); off != int64(middle-1) || err != nil {
+				return fmt.Errorf("Seek(%d, 1) from %d = %d, %v, want %d, nil", -len(content)/3, len(content)-1, off, err, middle-1)
+			}
+			if off, err := r.Seek(+1, 1); off != int64(middle) || err != nil {
+				return fmt.Errorf("Seek(+1, 1) from %d = %d, %v, want %d, nil", middle-1, off, err, middle)
+			}
+		}
+
+		// Seek(0, 1) should report the current file position (middle).
+		if off, err := r.Seek(0, 1); off != int64(middle) || err != nil {
+			return fmt.Errorf("Seek(0, 1) from %d = %d, %v, want %d, nil", middle, off, err, middle)
+		}
+
+		// Reading forward should return the last part of the file.
+		data, err := io.ReadAll(&smallByteReader{r: r})
+		if err != nil {
+			return fmt.Errorf("ReadAll from offset %d: %v", middle, err)
+		}
+		if !bytes.Equal(data, content[middle:]) {
+			return fmt.Errorf("ReadAll from offset %d = %q\n\twant %q", middle, data, content[middle:])
+		}
+
+		// Seek relative to end of file, but start elsewhere.
+		if off, err := r.Seek(int64(middle/2), 0); off != int64(middle/2) || err != nil {
+			return fmt.Errorf("Seek(%d, 0) from EOF = %d, %v, want %d, nil", middle/2, off, err, middle/2)
+		}
+		if off, err := r.Seek(int64(-len(content)/3), 2); off != int64(middle) || err != nil {
+			return fmt.Errorf("Seek(%d, 2) from %d = %d, %v, want %d, nil", -len(content)/3, middle/2, off, err, middle)
+		}
+
+		// Reading forward should return the last part of the file (again).
+		data, err = io.ReadAll(&smallByteReader{r: r})
+		if err != nil {
+			return fmt.Errorf("ReadAll from offset %d: %v", middle, err)
+		}
+		if !bytes.Equal(data, content[middle:]) {
+			return fmt.Errorf("ReadAll from offset %d = %q\n\twant %q", middle, data, content[middle:])
+		}
+
+		// Absolute seek & read forward.
+		if off, err := r.Seek(int64(middle/2), 0); off != int64(middle/2) || err != nil {
+			return fmt.Errorf("Seek(%d, 0) from EOF = %d, %v, want %d, nil", middle/2, off, err, middle/2)
+		}
+		data, err = io.ReadAll(r)
+		if err != nil {
+			return fmt.Errorf("ReadAll from offset %d: %v", middle/2, err)
+		}
+		if !bytes.Equal(data, content[middle/2:]) {
+			return fmt.Errorf("ReadAll from offset %d = %q\n\twant %q", middle/2, data, content[middle/2:])
+		}
+	}
+
+	if r, ok := r.(io.ReaderAt); ok {
+		data := make([]byte, len(content), len(content)+1)
+		for i := range data {
+			data[i] = 0xfe
+		}
+		n, err := r.ReadAt(data, 0)
+		if n != len(data) || err != nil && err != io.EOF {
+			return fmt.Errorf("ReadAt(%d, 0) = %v, %v, want %d, nil or EOF", len(data), n, err, len(data))
+		}
+		if !bytes.Equal(data, content) {
+			return fmt.Errorf("ReadAt(%d, 0) = %q\n\twant %q", len(data), data, content)
+		}
+
+		n, err = r.ReadAt(data[:1], int64(len(data)))
+		if n != 0 || err != io.EOF {
+			return fmt.Errorf("ReadAt(1, %d) = %v, %v, want 0, EOF", len(data), n, err)
+		}
+
+		for i := range data {
+			data[i] = 0xfe
+		}
+		n, err = r.ReadAt(data[:cap(data)], 0)
+		if n != len(data) || err != io.EOF {
+			return fmt.Errorf("ReadAt(%d, 0) = %v, %v, want %d, EOF", cap(data), n, err, len(data))
+		}
+		if !bytes.Equal(data, content) {
+			return fmt.Errorf("ReadAt(%d, 0) = %q\n\twant %q", len(data), data, content)
+		}
+
+		for i := range data {
+			data[i] = 0xfe
+		}
+		for i := range data {
+			n, err = r.ReadAt(data[i:i+1], int64(i))
+			if n != 1 || err != nil && (i != len(data)-1 || err != io.EOF) {
+				want := "nil"
+				if i == len(data)-1 {
+					want = "nil or EOF"
+				}
+				return fmt.Errorf("ReadAt(1, %d) = %v, %v, want 1, %s", i, n, err, want)
+			}
+			if data[i] != content[i] {
+				return fmt.Errorf("ReadAt(1, %d) = %q want %q", i, data[i:i+1], content[i:i+1])
+			}
+		}
+	}
+	return nil
+}