Delete unnecessary seek from SetLengthInternal on Unix (#44097)

Also, improve test coverage for FileStream.SetLength
dotnet · Nov 1, 2020 · c03edca · c03edca
1 parent 8d007a7
commit c03edca
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Showing 3 changed files with 27 additions and 18 deletions.
diff --git a/src/libraries/System.IO.FileSystem/tests/FileStream/SetLength.cs b/src/libraries/System.IO.FileSystem/tests/FileStream/SetLength.cs
@@ -137,5 +137,28 @@ public void SetLengthShorter()
                 Assert.Equal(0, fs.Position);
             }
         }
+
+        [Fact]
+        public void SetLengthMaxValue()
+        {
+            using (FileStream fs = new FileStream(GetTestFilePath(), FileMode.Create))
+            {
+                // Depending on the file system, this can:
+                // - Throw IOException : No space left on device
+                // - Throw ArgumentOutOfRangeException : Specified file length was too large for the file system.
+                // - Succeed.
+                try
+                {
+                    fs.SetLength(long.MaxValue);
+                }
+                catch (Exception e)
+                {
+                    Assert.True(e is IOException || e is ArgumentOutOfRangeException, $"Unexpected exception {e}");
+                    return;
+                }
+
+                Assert.Equal(long.MaxValue, fs.Length);
+            }
+        }
     }
 }
diff --git a/src/libraries/System.IO.MemoryMappedFiles/tests/MemoryMappedFile.CreateNew.Tests.cs b/src/libraries/System.IO.MemoryMappedFiles/tests/MemoryMappedFile.CreateNew.Tests.cs
@@ -112,7 +112,7 @@ public void TooLargeCapacity_Unix()
             // due to differences in OS behaviors and Unix not actually having a notion of
             // a view separate from a map.  It could also come from CreateNew, depending
             // on what backing store is being used.
-            Assert.Throws<IOException>(() =>
+            AssertExtensions.ThrowsAny<IOException, ArgumentOutOfRangeException>(() =>
             {
                 using (MemoryMappedFile mmf = MemoryMappedFile.CreateNew(null, (IntPtr.Size == 4) ? uint.MaxValue : long.MaxValue))
                 {

diff --git a/src/libraries/System.Private.CoreLib/src/System/IO/FileStream.Unix.cs b/src/libraries/System.Private.CoreLib/src/System/IO/FileStream.Unix.cs
@@ -401,28 +401,14 @@ private void SetLengthInternal(long value)
                 throw new IOException(SR.IO_SetLengthAppendTruncate);
             }
 
-            long origPos = _filePosition;
-
             VerifyOSHandlePosition();
 
-            if (_filePosition != value)
-            {
-                SeekCore(_fileHandle, value, SeekOrigin.Begin);
-            }
-
             CheckFileCall(Interop.Sys.FTruncate(_fileHandle, value));
 
-            // Return file pointer to where it was before setting length
-            if (origPos != value)
+            // Set file pointer to end of file
+            if (_filePosition > value)
             {
-                if (origPos < value)
-                {
-                    SeekCore(_fileHandle, origPos, SeekOrigin.Begin);
-                }
-                else
-                {
-                    SeekCore(_fileHandle, 0, SeekOrigin.End);
-                }
+                SeekCore(_fileHandle, 0, SeekOrigin.End);
             }
         }