SequencePointEncoder.cs

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using System;
using System.Diagnostics;
using System.Reflection.Metadata;
using System.Reflection.Metadata.Ecma335;
 
namespace IKVM.Reflection.Emit
{
 
    struct SequencePointEncoder
    {
 
        readonly BlobBuilder writer;
 
        bool localSignatureEncoded = false;
        bool sequencePointEncoded = false;
        int prevOffset = -1;
        int prevNonHiddenStartLine = -1;
        int prevNonHiddenStartColumn = -1;
 
        public SequencePointEncoder(BlobBuilder writer)
        {
            this.writer = writer ?? throw new ArgumentNullException(nameof(writer));
        }
 
        public void LocalSignature(StandaloneSignatureHandle localSignature)
        {
            if (localSignatureEncoded)
                throw new InvalidOperationException("Local Signature already encoded.");
            if (sequencePointEncoded)
                throw new InvalidOperationException("Sequence point already encoded.");
 
            // write local signature
            writer.WriteCompressedInteger(MetadataTokens.GetRowNumber(localSignature));
 
            localSignatureEncoded = true;
        }
 
        public void SequencePoint(DocumentHandle document, int offset, int startLine, int startColumn, int endLine, int endColumn, ref DocumentHandle previousDocument)
        {
            if (localSignatureEncoded == false)
                throw new InvalidOperationException("Local signature not already encoded.");
            if (offset <= prevOffset)
                throw new ArgumentException("Subsequent sequence points must appear at an offset greater than the previous sequence point.");
 
            // document passed, and different from previous, write new document-record
            if (document.IsNil == false && document != previousDocument)
            {
                // this isn't the initial header document, but a document-record, which requires a zero IL offset
                if (sequencePointEncoded)
                    writer.WriteCompressedInteger(0);
 
                writer.WriteCompressedInteger(MetadataTokens.GetRowNumber(document));
                previousDocument = document;
            }
 
            // IL offset or delta IL offset
            if (prevOffset == -1)
                writer.WriteCompressedInteger(offset);
            else
                writer.WriteCompressedInteger(offset - prevOffset);
 
            // hidden or non-hidden sequence point
            if (startLine == System.Reflection.Metadata.SequencePoint.HiddenLine)
            {
                writer.WriteCompressedInteger(0);
                writer.WriteCompressedInteger(0);
            }
            else
            {
                var deltaLines = endLine - startLine;
                var deltaColumns = endColumn - startColumn;
                Debug.Assert(startLine == System.Reflection.Metadata.SequencePoint.HiddenLine || deltaLines > 0 || deltaColumns > 0);
 
                // write change in lines; then change in columns (signed if change in lines)
                writer.WriteCompressedInteger(deltaLines);
                if (deltaLines == 0)
                    writer.WriteCompressedInteger(deltaColumns);
                else
                    writer.WriteCompressedSignedInteger(deltaColumns);
 
                // delta start lines & columns
                if (prevNonHiddenStartLine == -1)
                {
                    Debug.Assert(prevNonHiddenStartColumn == -1);
                    writer.WriteCompressedInteger(startLine);
                    writer.WriteCompressedInteger(startColumn);
                }
                else
                {
                    writer.WriteCompressedSignedInteger(startLine - prevNonHiddenStartLine);
                    writer.WriteCompressedSignedInteger(startColumn - prevNonHiddenStartColumn);
                }
 
                prevNonHiddenStartLine = startLine;
                prevNonHiddenStartColumn = startColumn;
            }
 
            prevOffset = offset;
            sequencePointEncoded = true;
        }
 
    }
 
}