From 967c2b29409f447645f55dbc7fd20077ae07ae36 Mon Sep 17 00:00:00 2001
From: Krishnan Parthasarathi <krisis@users.noreply.github.com>
Date: Mon, 30 May 2016 23:57:15 +0530
Subject: [PATCH] Handled possible short writes to httpResponseWriter (#1804)

* XL: Handled possible short writes to httpResponseWriter

* Added tests for Range Header combinations
---
 erasure-readfile.go |  4 ++--
 server_xl_test.go   | 31 ++++++++++++++++++++-----------
 xl-v1-object.go     | 15 ++++++++-------
 3 files changed, 30 insertions(+), 20 deletions(-)

diff --git a/erasure-readfile.go b/erasure-readfile.go
index 5edaab574..02d9eac0b 100644
--- a/erasure-readfile.go
+++ b/erasure-readfile.go
@@ -19,7 +19,7 @@ package main
 import "errors"
 
 // ReadFile - decoded erasure coded file.
-func (e erasure) ReadFile(volume, path string, bufferOffset int64, startOffset int64, buffer []byte) (int64, error) {
+func (e erasure) ReadFile(volume, path string, startOffset int64, buffer []byte) (int64, error) {
 	// Calculate the current encoded block size.
 	curEncBlockSize := getEncodedBlockLen(int64(len(buffer)), e.DataBlocks)
 	offsetEncOffset := getEncodedBlockLen(startOffset, e.DataBlocks)
@@ -89,7 +89,7 @@ func (e erasure) ReadFile(volume, path string, bufferOffset int64, startOffset i
 	}
 
 	// Copy data blocks.
-	copy(buffer, dataBlocks[bufferOffset:])
+	copy(buffer, dataBlocks)
 
 	// Relenquish memory.
 	dataBlocks = nil
diff --git a/server_xl_test.go b/server_xl_test.go
index c6eff8e3d..69cf96d75 100644
--- a/server_xl_test.go
+++ b/server_xl_test.go
@@ -920,18 +920,27 @@ func (s *MyAPIXLSuite) TestPartialContent(c *C) {
 	c.Assert(response.StatusCode, Equals, http.StatusOK)
 
 	// Prepare request
-	request, err = s.newRequest("GET", testAPIXLServer.URL+"/partial-content/bar", 0, nil)
-	c.Assert(err, IsNil)
-	request.Header.Add("Range", "bytes=6-7")
+	var table = []struct {
+		byteRange      string
+		expectedString string
+	}{
+		{"6-7", "Wo"},
+		{"6-", "World"},
+		{"-7", "o World"},
+	}
+	for _, t := range table {
+		request, err = s.newRequest("GET", testAPIXLServer.URL+"/partial-content/bar", 0, nil)
+		c.Assert(err, IsNil)
+		request.Header.Add("Range", "bytes="+t.byteRange)
 
-	client = http.Client{}
-	response, err = client.Do(request)
-	c.Assert(err, IsNil)
-	c.Assert(response.StatusCode, Equals, http.StatusPartialContent)
-	partialObject, err := ioutil.ReadAll(response.Body)
-	c.Assert(err, IsNil)
-
-	c.Assert(string(partialObject), Equals, "Wo")
+		client = http.Client{}
+		response, err = client.Do(request)
+		c.Assert(err, IsNil)
+		c.Assert(response.StatusCode, Equals, http.StatusPartialContent)
+		partialObject, err := ioutil.ReadAll(response.Body)
+		c.Assert(err, IsNil)
+		c.Assert(string(partialObject), Equals, t.expectedString)
+	}
 }
 
 func (s *MyAPIXLSuite) TestListObjectsHandlerErrors(c *C) {
diff --git a/xl-v1-object.go b/xl-v1-object.go
index a0a6abd33..3fc9ef889 100644
--- a/xl-v1-object.go
+++ b/xl-v1-object.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bytes"
 	"crypto/md5"
 	"encoding/hex"
 	"io"
@@ -63,27 +64,27 @@ func (xl xlObjects) GetObject(bucket, object string, startOffset int64, length i
 			}
 			var buffer = make([]byte, curBlockSize)
 			var n int64
-			n, err = erasure.ReadFile(bucket, pathJoin(object, part.Name), partOffset, beginOffset, buffer)
+			n, err = erasure.ReadFile(bucket, pathJoin(object, part.Name), beginOffset, buffer)
 			if err != nil {
 				return err
 			}
 			if length > int64(len(buffer)) {
-				var m int
-				m, err = writer.Write(buffer)
+				var m int64
+				m, err = io.Copy(writer, bytes.NewReader(buffer[partOffset:]))
 				if err != nil {
 					return err
 				}
-				length -= int64(m)
+				length -= m
 			} else {
-				_, err = writer.Write(buffer[:length])
+				_, err = io.CopyN(writer, bytes.NewReader(buffer[partOffset:]), length)
 				if err != nil {
 					return err
 				}
 				return nil
 			}
-			totalLeft -= partOffset + n
+			totalLeft -= n
 			beginOffset += n
-			// Reset part offset to 0 to read rest of the parts from the beginning.
+			// Reset part offset to 0 to read rest of the part from the beginning.
 			partOffset = 0
 		}
 	}