Fix seek for ColumnStream (#5224)

vonzshik · vonzshik · commit c2440b8cdaa9 · 2023-08-25T19:21:47.000+03:00
Fixes #5223 (cherry picked from commit 820cfcd) # Conflicts: # src/Npgsql/Internal/NpgsqlReadBuffer.Stream.cs # test/Npgsql.Tests/ReaderTests.cs
diff --git a/src/Npgsql/NpgsqlReadBuffer.Stream.cs b/src/Npgsql/NpgsqlReadBuffer.Stream.cs
@@ -64,7 +64,7 @@ public override long Position
                 {
                     if (value < 0)
                         throw new ArgumentOutOfRangeException(nameof(value), "Non - negative number required.");
-                    Seek(_start + value, SeekOrigin.Begin);
+                    Seek(value, SeekOrigin.Begin);
                 }
             }
 
@@ -86,24 +86,25 @@ public override long Seek(long offset, SeekOrigin origin)
                     var tempPosition = unchecked(_start + (int)offset);
                     if (offset < 0 || tempPosition < _start)
                         throw new IOException(seekBeforeBegin);
-                    _buf.ReadPosition = _start;
-                    return tempPosition;
+                    _buf.ReadPosition = tempPosition;
+                    _read = (int)offset;
+                    return _read;
                 }
                 case SeekOrigin.Current:
                 {
                     var tempPosition = unchecked(_buf.ReadPosition + (int)offset);
                     if (unchecked(_buf.ReadPosition + offset) < _start || tempPosition < _start)
                         throw new IOException(seekBeforeBegin);
-                    _buf.ReadPosition = tempPosition;
-                    return tempPosition;
+                    _read += (int)offset;
+                    return _read;
                 }
                 case SeekOrigin.End:
                 {
-                    var tempPosition = unchecked(_len + (int)offset);
-                    if (unchecked(_len + offset) < _start || tempPosition < _start)
+                    var tempPosition = unchecked(_start + _len + (int)offset);
+                    if (unchecked(_start + _len + offset) < _start || tempPosition < _start)
                         throw new IOException(seekBeforeBegin);
-                    _buf.ReadPosition = tempPosition;
-                    return tempPosition;
+                    _read = _len + (int)offset;
+                    return _read;
                 }
                 default:
                     throw new ArgumentOutOfRangeException(nameof(origin), "Invalid seek origin.");
diff --git a/test/Npgsql.Tests/ReaderTests.cs b/test/Npgsql.Tests/ReaderTests.cs
@@ -1508,6 +1508,50 @@ static Func<NpgsqlDataReader, int, Task<Stream>> BuildStreamGetter(bool isAsync)
                 ? (Func<NpgsqlDataReader, int, Task<Stream>>)((r, index) => r.GetStreamAsync(index))
                 : (r, index) => Task.FromResult(r.GetStream(index));
 
+        [Test, IssueLink("https://github.com/npgsql/npgsql/issues/5223")]
+        public async Task GetStream_seek()
+        {
+            // Sequential doesn't allow to seek
+            if (IsSequential)
+                return;
+
+            await using var conn = await OpenConnectionAsync();
+            await using var cmd = conn.CreateCommand();
+            cmd.CommandText = "SELECT 'abcdefgh'";
+            await using var reader = await cmd.ExecuteReaderAsync();
+            await reader.ReadAsync();
+
+            var buffer = new byte[4];
+
+            await using var stream = reader.GetStream(0);
+            Assert.IsTrue(stream.CanSeek);
+
+            var seekPosition = stream.Seek(-1, SeekOrigin.End);
+            Assert.That(seekPosition, Is.EqualTo(stream.Length - 1));
+            var read = stream.Read(buffer);
+            Assert.That(read, Is.EqualTo(1));
+            Assert.That(Encoding.ASCII.GetString(buffer, 0, 1), Is.EqualTo("h"));
+            read = stream.Read(buffer);
+            Assert.That(read, Is.EqualTo(0));
+
+            seekPosition = stream.Seek(2, SeekOrigin.Begin);
+            Assert.That(seekPosition, Is.EqualTo(2));
+            read = stream.Read(buffer);
+            Assert.That(read, Is.EqualTo(buffer.Length));
+            Assert.That(Encoding.ASCII.GetString(buffer), Is.EqualTo("cdef"));
+
+            seekPosition = stream.Seek(-3, SeekOrigin.Current);
+            Assert.That(seekPosition, Is.EqualTo(3));
+            read = stream.Read(buffer);
+            Assert.That(read, Is.EqualTo(buffer.Length));
+            Assert.That(Encoding.ASCII.GetString(buffer), Is.EqualTo("defg"));
+
+            stream.Position = 1;
+            read = stream.Read(buffer);
+            Assert.That(read, Is.EqualTo(buffer.Length));
+            Assert.That(Encoding.ASCII.GetString(buffer), Is.EqualTo("bcde"));
+        }
+
         #endregion GetBytes / GetStream
 
         #region GetChars / GetTextReader

Original file line number	Diff line number	Diff line change
`@@ -64,7 +64,7 @@ public override long Position`
`64`	`64`	`{`
`65`	`65`	`if (value < 0)`
`66`	`66`	`throw new ArgumentOutOfRangeException(nameof(value), "Non - negative number required.");`
`67`		`- Seek(_start + value, SeekOrigin.Begin);`
	`67`	`+ Seek(value, SeekOrigin.Begin);`
`68`	`68`	`}`
`69`	`69`	`}`
`70`	`70`
`@@ -86,24 +86,25 @@ public override long Seek(long offset, SeekOrigin origin)`
`86`	`86`	`var tempPosition = unchecked(_start + (int)offset);`
`87`	`87`	`if (offset < 0 \|\| tempPosition < _start)`
`88`	`88`	`throw new IOException(seekBeforeBegin);`
`89`		`- _buf.ReadPosition = _start;`
`90`		`- return tempPosition;`
	`89`	`+ _buf.ReadPosition = tempPosition;`
	`90`	`+ _read = (int)offset;`
	`91`	`+ return _read;`
`91`	`92`	`}`
`92`	`93`	`case SeekOrigin.Current:`
`93`	`94`	`{`
`94`	`95`	`var tempPosition = unchecked(_buf.ReadPosition + (int)offset);`
`95`	`96`	`if (unchecked(_buf.ReadPosition + offset) < _start \|\| tempPosition < _start)`
`96`	`97`	`throw new IOException(seekBeforeBegin);`
`97`		`- _buf.ReadPosition = tempPosition;`
`98`		`- return tempPosition;`
	`98`	`+ _read += (int)offset;`
	`99`	`+ return _read;`
`99`	`100`	`}`
`100`	`101`	`case SeekOrigin.End:`
`101`	`102`	`{`
`102`		`- var tempPosition = unchecked(_len + (int)offset);`
`103`		`- if (unchecked(_len + offset) < _start \|\| tempPosition < _start)`
	`103`	`+ var tempPosition = unchecked(_start + _len + (int)offset);`
	`104`	`+ if (unchecked(_start + _len + offset) < _start \|\| tempPosition < _start)`
`104`	`105`	`throw new IOException(seekBeforeBegin);`
`105`		`- _buf.ReadPosition = tempPosition;`
`106`		`- return tempPosition;`
	`106`	`+ _read = _len + (int)offset;`
	`107`	`+ return _read;`
`107`	`108`	`}`
`108`	`109`	`default:`
`109`	`110`	`throw new ArgumentOutOfRangeException(nameof(origin), "Invalid seek origin.");`