diff options
Diffstat (limited to 'src/testing/iotest/reader.go')
| -rw-r--r-- | src/testing/iotest/reader.go | 174 |
1 files changed, 170 insertions, 4 deletions
diff --git a/src/testing/iotest/reader.go b/src/testing/iotest/reader.go index bc2f72a911..770d87f26b 100644 --- a/src/testing/iotest/reader.go +++ b/src/testing/iotest/reader.go @@ -6,7 +6,9 @@ package iotest import ( + "bytes" "errors" + "fmt" "io" ) @@ -90,13 +92,177 @@ func (r *timeoutReader) Read(p []byte) (int, error) { // ErrReader returns an io.Reader that returns 0, err from all Read calls. func ErrReader(err error) io.Reader { - return &alwaysErrReader{err: err} + return &errReader{err: err} } -type alwaysErrReader struct { +type errReader struct { err error } -func (aer *alwaysErrReader) Read(p []byte) (int, error) { - return 0, aer.err +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 } |