Implement gzip parsing and printing

SabreTools.Serialization/Deserializers/GZip.cs

@@ -1,5 +1,8 @@
+using System.Collections.Generic;
 using System.IO;
+using SabreTools.IO.Extensions;
 using SabreTools.Models.GZIP;
+using static SabreTools.Models.GZIP.Constants;
 
 namespace SabreTools.Serialization.Deserializers
 {
@@ -22,7 +25,28 @@ namespace SabreTools.Serialization.Deserializers
 
                 var archive = new Archive();
 
-                // TODO: Implement everything
+                #region Header
+
+                var header = ParseHeader(data);
+                if (header == null)
+                    return null;
+
+                archive.Header = header;
+
+                #endregion
+
+                // Seek to the end to read the trailer
+                data.Seek(-8, SeekOrigin.End);
+
+                #region Trailer
+
+                var trailer = ParseTrailer(data);
+                if (header == null)
+                    return null;
+
+                archive.Trailer = trailer;
+
+                #endregion
 
                 return archive;
             }
@@ -32,5 +56,106 @@ namespace SabreTools.Serialization.Deserializers
                 return null;
             }
         }
+
+        /// <summary>
+        /// Parse a Stream into a Header
+        /// </summary>
+        /// <param name="data">Stream to parse</param>
+        /// <returns>Filled Header on success, null on error</returns>
+        public static Header? ParseHeader(Stream data)
+        {
+            var obj = new Header();
+
+            obj.ID1 = data.ReadByteValue();
+            obj.ID2 = data.ReadByteValue();
+            if (obj.ID1 != ID1 || obj.ID2 != ID2)
+                return null;
+
+            obj.CM = (CompressionMethod)data.ReadByteValue();
+            obj.FLG = (Flags)data.ReadByteValue();
+            obj.MTIME = data.ReadUInt32LittleEndian();
+            obj.XFL = (ExtraFlags)data.ReadByteValue();
+            obj.OS = (OperatingSystem)data.ReadByteValue();
+
+#if NET20 || NET35
+            if ((obj.FLG & Flags.FEXTRA) != 0)
+#else
+            if (obj.FLG.HasFlag(Flags.FEXTRA))
+#endif
+            {
+                obj.XLEN = data.ReadUInt16LittleEndian();
+
+                // Cache the current position
+                long currentPosition = data.Position;
+
+                List<ExtraFieldData> extraFields = [];
+                while (data.Position < currentPosition + obj.XLEN)
+                {
+                    var extraField = ParseExtraFieldData(data);
+                    if (extraField == null)
+                        break;
+
+                    extraFields.Add(extraField);
+                }
+
+                obj.ExtraField = [.. extraFields];
+            }
+
+#if NET20 || NET35
+            if ((obj.FLG & Flags.FNAME) != 0)
+#else
+            if (obj.FLG.HasFlag(Flags.FNAME))
+#endif
+                obj.OriginalFileName = data.ReadNullTerminatedAnsiString();
+
+#if NET20 || NET35
+            if ((obj.FLG & Flags.FCOMMENT) != 0)
+#else
+            if (obj.FLG.HasFlag(Flags.FCOMMENT))
+#endif
+                obj.FileComment = data.ReadNullTerminatedAnsiString();
+
+
+#if NET20 || NET35
+            if ((obj.FLG & Flags.FHCRC) != 0)
+#else
+            if (obj.FLG.HasFlag(Flags.FHCRC))
+#endif
+                obj.CRC16 = data.ReadUInt16LittleEndian();
+
+            return obj;
+        }
+
+        /// <summary>
+        /// Parse a Stream into an ExtraFieldData
+        /// </summary>
+        /// <param name="data">Stream to parse</param>
+        /// <returns>Filled ExtraFieldData on success, null on error</returns>
+        public static ExtraFieldData? ParseExtraFieldData(Stream data)
+        {
+            var obj = new ExtraFieldData();
+
+            obj.SI1 = data.ReadByteValue();
+            obj.SI2 = data.ReadByteValue();
+            obj.LEN = data.ReadUInt16LittleEndian();
+            obj.Data = data.ReadBytes(obj.LEN);
+
+            return obj;
+        }
+
+        /// <summary>
+        /// Parse a Stream into a Trailer
+        /// </summary>
+        /// <param name="data">Stream to parse</param>
+        /// <returns>Filled Trailer on success, null on error</returns>
+        public static Trailer? ParseTrailer(Stream data)
+        {
+            var obj = new Trailer();
+
+            obj.CRC32 = data.ReadUInt32LittleEndian();
+            obj.ISIZE = data.ReadUInt32LittleEndian();
+
+            return obj;
+        }
     }
 }

SabreTools.Serialization/Printers/GZip.cs

@@ -16,7 +16,74 @@ namespace SabreTools.Serialization.Printers
             builder.AppendLine("-------------------------");
             builder.AppendLine();
 
-            // TODO: Implement
+            Print(builder, file.Header);
+            // TODO: Capture or print the compressed data
+            Print(builder, file.Trailer);
+        }
+
+        private static void Print(StringBuilder builder, Header? header)
+        {
+            builder.AppendLine("  Header:");
+            builder.AppendLine("  -------------------------");
+            if (header == null)
+            {
+                builder.AppendLine("  No header");
+                builder.AppendLine();
+                return;
+            }
+
+            builder.AppendLine(header.ID1, "  ID1");
+            builder.AppendLine(header.ID2, "  ID1");
+            builder.AppendLine($"  Compression method: {header.CM} (0x{(byte)header.CM:X2})");
+            builder.AppendLine($"  Flags: {header.FLG} (0x{(byte)header.FLG:X2})");
+            builder.AppendLine(header.MTIME, "  Last modified time");
+            builder.AppendLine($"  Extra flags: {header.XFL} (0x{(byte)header.XFL:X2})");
+            builder.AppendLine($"  Operating system: {header.OS} (0x{(byte)header.OS:X2})");
+            builder.AppendLine(header.XLEN, "  Extra length");
+            Print(builder, header.ExtraField);
+            builder.AppendLine(header.OriginalFileName, "  Original file name");
+            builder.AppendLine(header.FileComment, "  File comment");
+            builder.AppendLine(header.CRC16, "  CRC-16");
+            builder.AppendLine();
+        }
+
+        private static void Print(StringBuilder builder, ExtraFieldData[]? entries)
+        {
+            builder.AppendLine("  Extra Fields:");
+            builder.AppendLine("  -------------------------");
+            if (entries == null || entries.Length == 0)
+            {
+                builder.AppendLine("  No extra fields");
+                builder.AppendLine();
+                return;
+            }
+
+            for (int i = 0; i < entries.Length; i++)
+            {
+                var entry = entries[i];
+
+                builder.AppendLine($"  Extra Field {i}:");
+                builder.AppendLine(entry.SI1, "    Subfield ID1");
+                builder.AppendLine(entry.SI2, "    Subfield ID2");
+                builder.AppendLine(entry.LEN, "    Length");
+                builder.AppendLine(entry.Data, "    Data");
+            }
+        }
+
+        private static void Print(StringBuilder builder, Trailer? trailer)
+        {
+            builder.AppendLine("  Trailer:");
+            builder.AppendLine("  -------------------------");
+            if (trailer == null)
+            {
+                builder.AppendLine("  No trailer");
+                builder.AppendLine();
+                return;
+            }
+
+            builder.AppendLine(trailer.CRC32, "  CRC-32");
+            builder.AppendLine(trailer.ISIZE, "  Input size");
+            builder.AppendLine();
         }
     }
 }

SabreTools.Serialization/Wrappers/GZip.cs

@@ -15,6 +15,62 @@ namespace SabreTools.Serialization.Wrappers
 
         #endregion
 
+        #region Extension Properties
+
+        /// <summary>
+        /// Offset to the compressed data
+        /// </summary>
+        /// <remarks>Returns -1 on error</remarks>
+        public long DataOffset
+        {
+            get
+            {
+                if (_dataOffset != null)
+                    return _dataOffset.Value;
+
+                if (Header == null)
+                    return -1;
+
+                // Minimum offset is 10 bytes:
+                // - ID1 (1)
+                // - ID2 (1)
+                // - CompressionMethod (1)
+                // - Flags (1)
+                // - LastModifiedTime (4)
+                // - ExtraFlags (1)
+                // - OperatingSystem (1)
+                _dataOffset = 10;
+
+                // Add extra lengths
+                _dataOffset += Header.XLEN;
+                if (Header.OriginalFileName != null)
+                    _dataOffset += Header.OriginalFileName.Length + 1;
+                if (Header.FileComment != null)
+                    _dataOffset += Header.FileComment.Length + 1;
+                if (Header.CRC16 != null)
+                    _dataOffset += 2;
+
+                return _dataOffset.Value;
+            }
+        }
+
+        /// <inheritdoc cref="Archive.Header"/>
+        public Header? Header => Model.Header;
+
+        /// <inheritdoc cref="Archive.Trailer"/>
+        public Trailer? Trailer => Model.Trailer;
+
+        #endregion
+
+        #region Instance Variables
+
+        /// <summary>
+        /// Offset to the compressed data
+        /// </summary>
+        private long? _dataOffset = null;
+
+        #endregion
+
         #region Constructors
 
         /// <inheritdoc/>