compress/gzip: fix error handling in Read

The Read logic should not assume that only (0, io.EOF) is returned
instead of (n, io.EOF) where n is positive.

The fix done here is very similar to the fix to compress/zlib
in CL/20292.

Change-Id: Icb76258cdcf8cfa386a60bab330fefde46fc071d
Reviewed-on: https://go-review.googlesource.com/21308
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/compress/gzip/gunzip.go b/src/compress/gzip/gunzip.go
index 4a4f19443d2b442ee82e688cad28aa6b51bb670e..8ab2b5e5ecf6dd85972675e1b24d3d98ed37ce23 100644 (file)
--- a/src/compress/gzip/gunzip.go
+++ b/src/compress/gzip/gunzip.go
@@ -262,16 +262,13 @@ func (z *Reader) Read(p []byte) (n int, err error) {
        if z.err != nil {
                return 0, z.err
        }
-       if len(p) == 0 {
-               return 0, nil
-       }
 
-       n, err = z.decompressor.Read(p)
+       n, z.err = z.decompressor.Read(p)
        z.digest.Write(p[0:n])
        z.size += uint32(n)
-       if n != 0 || err != io.EOF {
-               z.err = err
-               return
+       if z.err != io.EOF {
+               // In the normal case we return here.
+               return n, z.err
        }
 
        // Finished file; check checksum + size.
@@ -280,28 +277,31 @@ func (z *Reader) Read(p []byte) (n int, err error) {
                        err = io.ErrUnexpectedEOF
                }
                z.err = err
-               return 0, err
+               return n, err
        }
        crc32, isize := get4(z.buf[0:4]), get4(z.buf[4:8])
        sum := z.digest.Sum32()
        if sum != crc32 || isize != z.size {
                z.err = ErrChecksum
-               return 0, z.err
+               return n, z.err
        }
+       z.digest.Reset()
+       z.size = 0
 
-       // File is ok; is there another?
+       // File is ok; check if there is another.
        if !z.multistream {
-               return 0, io.EOF
+               return n, io.EOF
        }
+       z.err = nil // Remove io.EOF
 
-       if err = z.readHeader(false); err != nil {
-               z.err = err
-               return
+       if z.err = z.readHeader(false); z.err != nil {
+               return n, z.err
        }
 
-       // Yes. Reset and read from it.
-       z.digest.Reset()
-       z.size = 0
+       // Read from next file, if necessary.
+       if n > 0 {
+               return n, nil
+       }
        return z.Read(p)
 }