From c86db64880d52630c372aa24f7aadf0036fb3fcf Mon Sep 17 00:00:00 2001
From: Jesse Plamondon-Willard <Pathoschild@users.noreply.github.com>
Date: Sun, 4 Aug 2019 16:37:10 -0400
Subject: encapsulate gzip logic for reuse (#654)
---
src/SMAPI.Web/Framework/Compression/GzipHelper.cs | 89 ++++++++++++++++++++++
src/SMAPI.Web/Framework/Compression/IGzipHelper.cs | 17 +++++
2 files changed, 106 insertions(+)
create mode 100644 src/SMAPI.Web/Framework/Compression/GzipHelper.cs
create mode 100644 src/SMAPI.Web/Framework/Compression/IGzipHelper.cs
(limited to 'src/SMAPI.Web/Framework/Compression')
diff --git a/src/SMAPI.Web/Framework/Compression/GzipHelper.cs b/src/SMAPI.Web/Framework/Compression/GzipHelper.cs
new file mode 100644
index 00000000..cc8f4737
--- /dev/null
+++ b/src/SMAPI.Web/Framework/Compression/GzipHelper.cs
@@ -0,0 +1,89 @@
+using System;
+using System.IO;
+using System.IO.Compression;
+using System.Text;
+
+namespace StardewModdingAPI.Web.Framework.Compression
+{
+ /// <summary>Handles GZip compression logic.</summary>
+ internal class GzipHelper : IGzipHelper
+ {
+ /*********
+ ** Fields
+ *********/
+ /// <summary>The first bytes in a valid zip file.</summary>
+ /// <remarks>See <a href="https://en.wikipedia.org/wiki/Zip_(file_format)#File_headers"/>.</remarks>
+ private const uint GzipLeadBytes = 0x8b1f;
+
+
+ /*********
+ ** Public methods
+ *********/
+ /// <summary>Compress a string.</summary>
+ /// <param name="text">The text to compress.</param>
+ /// <remarks>Derived from <a href="https://stackoverflow.com/a/17993002/262123"/>.</remarks>
+ public string CompressString(string text)
+ {
+ // get raw bytes
+ byte[] buffer = Encoding.UTF8.GetBytes(text);
+
+ // compressed
+ byte[] compressedData;
+ using (MemoryStream stream = new MemoryStream())
+ {
+ using (GZipStream zipStream = new GZipStream(stream, CompressionLevel.Optimal, leaveOpen: true))
+ zipStream.Write(buffer, 0, buffer.Length);
+
+ stream.Position = 0;
+ compressedData = new byte[stream.Length];
+ stream.Read(compressedData, 0, compressedData.Length);
+ }
+
+ // prefix length
+ byte[] zipBuffer = new byte[compressedData.Length + 4];
+ Buffer.BlockCopy(compressedData, 0, zipBuffer, 4, compressedData.Length);
+ Buffer.BlockCopy(BitConverter.GetBytes(buffer.Length), 0, zipBuffer, 0, 4);
+
+ // return string representation
+ return Convert.ToBase64String(zipBuffer);
+ }
+
+ /// <summary>Decompress a string.</summary>
+ /// <param name="rawText">The compressed text.</param>
+ /// <remarks>Derived from <a href="https://stackoverflow.com/a/17993002/262123"/>.</remarks>
+ public string DecompressString(string rawText)
+ {
+ // get raw bytes
+ byte[] zipBuffer;
+ try
+ {
+ zipBuffer = Convert.FromBase64String(rawText);
+ }
+ catch
+ {
+ return rawText; // not valid base64, wasn't compressed by the log parser
+ }
+
+ // skip if not gzip
+ if (BitConverter.ToUInt16(zipBuffer, 4) != GzipHelper.GzipLeadBytes)
+ return rawText;
+
+ // decompress
+ using (MemoryStream memoryStream = new MemoryStream())
+ {
+ // read length prefix
+ int dataLength = BitConverter.ToInt32(zipBuffer, 0);
+ memoryStream.Write(zipBuffer, 4, zipBuffer.Length - 4);
+
+ // read data
+ byte[] buffer = new byte[dataLength];
+ memoryStream.Position = 0;
+ using (GZipStream gZipStream = new GZipStream(memoryStream, CompressionMode.Decompress))
+ gZipStream.Read(buffer, 0, buffer.Length);
+
+ // return original string
+ return Encoding.UTF8.GetString(buffer);
+ }
+ }
+ }
+}
diff --git a/src/SMAPI.Web/Framework/Compression/IGzipHelper.cs b/src/SMAPI.Web/Framework/Compression/IGzipHelper.cs
new file mode 100644
index 00000000..a000865e
--- /dev/null
+++ b/src/SMAPI.Web/Framework/Compression/IGzipHelper.cs
@@ -0,0 +1,17 @@
+namespace StardewModdingAPI.Web.Framework.Compression
+{
+ /// <summary>Handles GZip compression logic.</summary>
+ internal interface IGzipHelper
+ {
+ /*********
+ ** Methods
+ *********/
+ /// <summary>Compress a string.</summary>
+ /// <param name="text">The text to compress.</param>
+ string CompressString(string text);
+
+ /// <summary>Decompress a string.</summary>
+ /// <param name="rawText">The compressed text.</param>
+ string DecompressString(string rawText);
+ }
+}
--
cgit