Replace SkipBytes and SeekOffset with Offset setter (#12375)

src/System.Reflection.Metadata/src/System/Reflection/Metadata/BlobReader.cs

@@ -16,7 +16,7 @@ public unsafe struct BlobReader
         /// <summary>An array containing the '\0' character.</summary>
         private static readonly char[] s_nullCharArray = new char[1] { '\0' };
 
-        internal const int InvalidCompressedInteger = Int32.MaxValue;
+        internal const int InvalidCompressedInteger = int.MaxValue;
 
         private readonly MemoryBlock _block;
 
@@ -90,9 +90,25 @@ internal string GetDebuggerDisplay()
         public int Length => _block.Length;
 
         /// <summary>
-        /// Offset from start of underlying memory block to current position.
+        /// Gets or sets the offset from start of the blob to the current position.
         /// </summary>
-        public int Offset => (int)(_currentPointer - _block.Pointer);
+        /// <exception cref="BadImageFormatException">Offset is set outside the bounds of underlying reader.</exception>
+        public int Offset
+        {
+            get
+            {
+                return (int)(_currentPointer - _block.Pointer);
+            }
+            set
+            {
+                if (unchecked((uint)value) > (uint)_block.Length)
+                {
+                    Throw.OutOfBounds();
+                }
+
+                _currentPointer = _block.Pointer + value;
+            }
+        }
 
         /// <summary>
         /// Bytes remaining from current position to end of underlying memory block.
@@ -107,37 +123,6 @@ public void Reset()
             _currentPointer = _block.Pointer;
         }
 
-        /// <summary>
-        /// Repositions the reader to the given offset from the start of the underlying memory block.
-        /// </summary>
-        /// <exception cref="BadImageFormatException">Offset is outside the bounds of underlying reader.</exception>
-        public void SeekOffset(int offset)
-        {
-            if (!TrySeekOffset(offset))
-            {
-                Throw.OutOfBounds();
-            }
-        }
-
-        internal bool TrySeekOffset(int offset)
-        {
-            if (unchecked((uint)offset) >= (uint)_block.Length)
-            {
-                return false;
-            }
-
-            _currentPointer = _block.Pointer + offset;
-            return true;
-        }
-
-        /// <summary>
-        /// Repositions the reader forward by the given number of bytes.
-        /// </summary>
-        public void SkipBytes(int count)
-        {
-            GetCurrentPointerAndAdvance(count);
-        }
-
         /// <summary>
         /// Repositions the reader forward by the number of bytes required to satisfy the given alignment.
         /// </summary>

src/System.Reflection.Metadata/src/System/Reflection/Metadata/IL/MethodBodyBlock.cs

@@ -153,7 +153,7 @@ public static MethodBodyBlock Create(BlobReader reader)
             }
 
             var ilBlock = reader.GetMemoryBlockAt(0, ilSize);
-            reader.SkipBytes(ilSize);
+            reader.Offset += ilSize;
 
             ImmutableArray<ExceptionRegion> exceptionHandlers;
             if (hasExceptionHandlers)
@@ -174,7 +174,7 @@ public static MethodBodyBlock Create(BlobReader reader)
                 }
                 else
                 {
-                    reader.SkipBytes(2); // skip over reserved field
+                    reader.Offset += 2; // skip over reserved field
                     exceptionHandlers = ReadSmallExceptionHandlers(ref reader, dataSize / 12);
                 }
             }

src/System.Reflection.Metadata/src/System/Reflection/Metadata/MetadataReader.cs

@@ -63,6 +63,7 @@ public unsafe MetadataReader(byte* metadata, int length, MetadataReaderOptions o
         /// <exception cref="ArgumentNullException"><paramref name="metadata"/> is null.</exception>
         /// <exception cref="ArgumentException">The encoding of <paramref name="utf8Decoder"/> is not <see cref="UTF8Encoding"/>.</exception>
         /// <exception cref="PlatformNotSupportedException">The current platform is big-endian.</exception>
+        /// <exception cref="BadImageFormatException">Bad metadata header.</exception>
         public unsafe MetadataReader(byte* metadata, int length, MetadataReaderOptions options, MetadataStringDecoder utf8Decoder)
         {
             // Do not throw here when length is 0. We'll throw BadImageFormatException later on, so that the caller doesn't need to 
@@ -206,7 +207,7 @@ private void ReadMetadataHeader(ref BlobReader memReader, out string versionStri
 
             int numberOfBytesRead;
             versionString = memReader.GetMemoryBlockAt(0, versionStringSize).PeekUtf8NullTerminated(0, null, UTF8Decoder, out numberOfBytesRead, '\0');
-            memReader.SkipBytes(versionStringSize);
+            memReader.Offset += versionStringSize;
         }
 
         private MetadataKind GetMetadataKind(string versionString)

src/System.Reflection.Metadata/tests/Metadata/MetadataReaderTests.cs

@@ -2756,7 +2756,7 @@ private static unsafe byte[] ObfuscateWithExtraData(byte[] unobfuscated, bool se
                     blobReader.ReadUInt16(); // minor version
                     blobReader.ReadUInt32(); // reserved
                     int versionStringSize = blobReader.ReadInt32();
-                    blobReader.SkipBytes(versionStringSize);
+                    blobReader.Offset += versionStringSize;
 
                     // read stream headers to collect offsets and sizes to adjust later
                     blobReader.ReadUInt16(); // reserved