From 648d035a0fe6cd44fab7108f09314b9d75965231 Mon Sep 17 00:00:00 2001
From: orignal <i2porignal@yandex.ru>
Date: Tue, 19 May 2020 21:02:32 -0400
Subject: [PATCH] GzipNoCompression for datagrams

---
 libi2pd/Datagram.cpp |  4 ++--
 libi2pd/Gzip.cpp     | 22 ++++++++++++++++++++++
 libi2pd/Gzip.h       |  1 +
 3 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/libi2pd/Datagram.cpp b/libi2pd/Datagram.cpp
index 7eb20460..08cd86bf 100644
--- a/libi2pd/Datagram.cpp
+++ b/libi2pd/Datagram.cpp
@@ -127,8 +127,8 @@ namespace datagram
 		auto msg = NewI2NPMessage ();
 		uint8_t * buf = msg->GetPayload ();
 		buf += 4; // reserve for length
-		m_Deflator.SetCompressionLevel (m_Gzip ? Z_DEFAULT_COMPRESSION : Z_NO_COMPRESSION);
-		size_t size = m_Deflator.Deflate (payloads, buf, msg->maxLen - msg->len);
+		size_t size = m_Gzip ? m_Deflator.Deflate (payloads, buf, msg->maxLen - msg->len) :
+			 i2p::data::GzipNoCompression (payloads, buf, msg->maxLen - msg->len);
 		if (size)
 		{
 			htobe32buf (msg->GetPayload (), size); // length
diff --git a/libi2pd/Gzip.cpp b/libi2pd/Gzip.cpp
index f098987a..f36620ae 100644
--- a/libi2pd/Gzip.cpp
+++ b/libi2pd/Gzip.cpp
@@ -174,6 +174,28 @@ namespace data
 		htole32buf (out + inLen + 19, inLen);
 		return inLen + 23;
 	}
+
+	size_t GzipNoCompression (const std::vector<std::pair<const uint8_t *, size_t> >& bufs, uint8_t * out, size_t outLen)
+	{	
+		static const uint8_t gzipHeader[11] = { 0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x01 };
+		memcpy (out, gzipHeader, 11);
+		uint32_t crc = 0;
+		size_t len = 0, len1;
+		for (const auto& it: bufs)
+		{
+			len1 = len;
+			len += it.second;
+			if (outLen < len + 23) return 0;
+			memcpy (out + 15 + len1, it.first, it.second); 
+			crc = crc32 (crc, it.first, it.second);
+		}	
+		if (len > 0xffff) return 0;
+		htole32buf (out + len + 15, crc);
+		htole32buf (out + len + 19, len);
+		htole16buf (out + 11, len);
+		htole16buf (out + 13, 0xffff - len);
+		return len + 23;
+	}
 	
 } // data
 } // i2p
diff --git a/libi2pd/Gzip.h b/libi2pd/Gzip.h
index e5b8775e..16776d35 100644
--- a/libi2pd/Gzip.h
+++ b/libi2pd/Gzip.h
@@ -44,6 +44,7 @@ namespace data
 	};
 
 	size_t GzipNoCompression (const uint8_t * in, uint16_t inLen, uint8_t * out, size_t outLen); // for < 64K
+	size_t GzipNoCompression (const std::vector<std::pair<const uint8_t *, size_t> >& bufs, uint8_t * out, size_t outLen); // for total size < 64K
 		
 } // data
 } // i2p