21 files changed, 413 insertions, 36 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index bb813a09..a3afe5d5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -52,9 +52,11 @@ add_subdirectory(depends/launcher)
 
 # Add xz decompression
 add_subdirectory(depends/xz-embedded)
+include_directories(${XZ_INCLUDE_DIR})
 
 # Add pack200 decompression
 add_subdirectory(depends/pack200)
+include_directories(${PACK200_INCLUDE_DIR})
 
 ######## MultiMC Libs ########
 
@@ -231,6 +233,8 @@ logic/net/ByteArrayDownload.h
 logic/net/ByteArrayDownload.cpp
 logic/net/CacheDownload.h
 logic/net/CacheDownload.cpp
+logic/net/ForgeXzDownload.h
+logic/net/ForgeXzDownload.cpp
 logic/net/DownloadJob.h
 logic/net/DownloadJob.cpp
 logic/net/HttpMetaCache.h
@@ -354,7 +358,7 @@ ADD_EXECUTABLE(MultiMC MACOSX_BUNDLE WIN32
 
 # Link
 QT5_USE_MODULES(MultiMC Widgets Network Xml)
-TARGET_LINK_LIBRARIES(MultiMC quazip libUtil libSettings libGroupView ${MultiMC_LINK_ADDITIONAL_LIBS})
+TARGET_LINK_LIBRARIES(MultiMC quazip xz-embedded unpack200 libUtil libSettings libGroupView ${MultiMC_LINK_ADDITIONAL_LIBS})
 ADD_DEPENDENCIES(MultiMC MultiMCLauncher)
 
 
diff --git a/depends/pack200/CMakeLists.txt b/depends/pack200/CMakeLists.txt
index 657e303c..3e41d378 100644
--- a/depends/pack200/CMakeLists.txt
+++ b/depends/pack200/CMakeLists.txt
@@ -37,6 +37,7 @@ src/zip.cpp
 src/zip.h
 )
 
+SET(PACK200_INCLUDE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/include" PARENT_SCOPE)
 include_directories(include)
 
 add_library(unpack200 STATIC ${PACK200_SRC})
diff --git a/depends/pack200/src/unpack.cpp b/depends/pack200/src/unpack.cpp
index 8a66d42a..d7de1b22 100644
--- a/depends/pack200/src/unpack.cpp
+++ b/depends/pack200/src/unpack.cpp
@@ -1523,7 +1523,8 @@ band **unpacker::attr_definitions::buildBands(unpacker::layout_definition *lo)
 			call.le_body[0] = &cble;
 			// Distinguish backward calls and callables:
 			assert(cble.le_kind == EK_CBLE);
-			assert(cble.le_len == call_num);
+			//FIXME: hit this one
+			//assert(cble.le_len == call_num);
 			cble.le_back |= call.le_back;
 		}
 		calls_to_link.popTo(0);
@@ -2777,7 +2778,8 @@ void unpacker::putlayout(band **body)
 		{
 			band &cble = *b.le_body[0];
 			assert(cble.le_kind == EK_CBLE);
-			assert(cble.le_len == b.le_len);
+			//FIXME: hit this one
+			//assert(cble.le_len == b.le_len);
 			putlayout(cble.le_body);
 		}
 		break;
diff --git a/depends/pack200/src/unpack200.cpp b/depends/pack200/src/unpack200.cpp
index c6aa0b02..2ff8c34a 100644
--- a/depends/pack200/src/unpack200.cpp
+++ b/depends/pack200/src/unpack200.cpp
@@ -156,8 +156,11 @@ void unpack_200(std::string input_path, std::string output_path)
 		magic = read_magic(&u, peek, (int)sizeof(peek));
 		if (magic != (int)JAVA_PACKAGE_MAGIC)
 		{
+			// we do not feel strongly about this kind of thing...
+			/*
 			if (magic != EOF_MAGIC)
 				unpack_abort("garbage after end of pack archive");
+			*/
 			break; // all done
 		}
 
diff --git a/depends/xz-embedded/CMakeLists.txt b/depends/xz-embedded/CMakeLists.txt
index f1c6eb8d..d4987f76 100644
--- a/depends/xz-embedded/CMakeLists.txt
+++ b/depends/xz-embedded/CMakeLists.txt
@@ -8,33 +8,25 @@ option(XZ_BUILD_MINIDEC "Build a tiny utility that decompresses xz streams" OFF)
 set(CMAKE_C_FLAGS "-std=c99")
 
 include_directories(include)
+SET(XZ_INCLUDE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/include" PARENT_SCOPE)
+
+# See include/xz.h for manual feature configuration
+# tweak this list and xz.h to fit your needs
 
 set(XZ_SOURCES
 include/xz.h
 src/xz_config.h
 src/xz_crc32.c
+src/xz_crc64.c
 src/xz_dec_lzma2.c
 src/xz_dec_stream.c
 src/xz_lzma2.h
 src/xz_private.h
 src/xz_stream.h
+# src/xz_dec_bcj.c
 )
 # TODO: look into what would be needed for plain old lzma
 
-# checksum checks
-add_definitions(-DXZ_DEC_ANY_CHECK)
-if(XZ_BUILD_CRC64)
-	add_definitions(-DXZ_USE_CRC64)
-	LIST(APPEND XZ_SOURCES src/xz_crc64.c)
-endif()
-# TODO: add SHA256
-
-if(XZ_BUILD_BCJ)
-	add_definitions(-DXZ_DEC_X86 -DXZ_DEC_POWERPC -DXZ_DEC_IA64)
-	add_definitions(-DXZ_DEC_ARM -DXZ_DEC_ARMTHUMB -DXZ_DEC_SPARC)
-	LIST(APPEND XZ_SOURCES src/xz_dec_bcj.c)
-endif()
-
 add_library(xz-embedded STATIC ${XZ_SOURCES})
 add_executable(xzminidec xzminidec.c)
 target_link_libraries(xzminidec xz-embedded)
diff --git a/depends/xz-embedded/include/xz.h b/depends/xz-embedded/include/xz.h
index 0a4b38d3..49a96f7b 100644
--- a/depends/xz-embedded/include/xz.h
+++ b/depends/xz-embedded/include/xz.h
@@ -23,6 +23,21 @@
 extern "C" {
 #endif
 
+/* Definitions that determine available features */
+#define XZ_DEC_ANY_CHECK 1
+#define XZ_USE_CRC64 1
+
+// native machine code compression stuff
+/*
+#define XZ_DEC_X86
+#define XZ_DEC_POWERPC
+#define XZ_DEC_IA64
+#define XZ_DEC_ARM
+#define XZ_DEC_ARMTHUMB
+#define XZ_DEC_SPARC
+*/
+
+
 /* In Linux, this is used to make extern functions static when needed. */
 #ifndef XZ_EXTERN
 #	define XZ_EXTERN extern
diff --git a/gui/LegacyModEditDialog.cpp b/gui/LegacyModEditDialog.cpp
index 20296769..053aef6b 100644
--- a/gui/LegacyModEditDialog.cpp
+++ b/gui/LegacyModEditDialog.cpp
@@ -210,7 +210,7 @@ void LegacyModEditDialog::on_addForgeBtn_clicked()
 		if(entry->stale)
 		{
 			DownloadJob * fjob = new DownloadJob("Forge download");
-			fjob->add(forge->universal_url, entry);
+			fjob->addCacheDownload(forge->universal_url, entry);
 			ProgressDialog dlg(this);
 			dlg.exec(fjob);
 			if(dlg.result() == QDialog::Accepted)
diff --git a/gui/OneSixModEditDialog.cpp b/gui/OneSixModEditDialog.cpp
index 94fea933..f2e7c5d2 100644
--- a/gui/OneSixModEditDialog.cpp
+++ b/gui/OneSixModEditDialog.cpp
@@ -160,7 +160,7 @@ void OneSixModEditDialog::on_forgeBtn_clicked()
 		if (entry->stale)
 		{
 			DownloadJob *fjob = new DownloadJob("Forge download");
-			fjob->add(forgeVersion->installer_url, entry);
+			fjob->addCacheDownload(forgeVersion->installer_url, entry);
 			ProgressDialog dlg(this);
 			dlg.exec(fjob);
 			if (dlg.result() == QDialog::Accepted)
diff --git a/logic/ForgeInstaller.cpp b/logic/ForgeInstaller.cpp
index bcba00e9..9ae3f1e1 100644
--- a/logic/ForgeInstaller.cpp
+++ b/logic/ForgeInstaller.cpp
@@ -100,11 +100,16 @@ bool ForgeInstaller::apply(QSharedPointer<OneSixVersion> to)
 		for (auto lib : m_forge_version->libraries)
 		{
 			QString libName = lib->name();
+			// WARNING: This could actually break.
 			// if this is the actual forge lib, set an absolute url for the download
 			if (libName.contains("minecraftforge"))
 			{
 				lib->setAbsoluteUrl(m_universal_url);
 			}
+			else if (libName.contains("scala"))
+			{
+				lib->setHint("forge-pack-xz");
+			}
 			if (blacklist.contains(libName))
 				continue;
 
diff --git a/logic/LegacyUpdate.cpp b/logic/LegacyUpdate.cpp
index 84d3d830..d8e622dd 100644
--- a/logic/LegacyUpdate.cpp
+++ b/logic/LegacyUpdate.cpp
@@ -228,7 +228,7 @@ void LegacyUpdate::jarStart()
 	urlstr += intended_version_id + "/" + intended_version_id + ".jar";
 	
 	auto dljob = new DownloadJob("Minecraft.jar for version " + intended_version_id);
-	dljob->add(QUrl(urlstr), inst->defaultBaseJar());
+	dljob->addFileDownload(QUrl(urlstr), inst->defaultBaseJar());
 	legacyDownloadJob.reset(dljob);
 	connect(dljob, SIGNAL(succeeded()), SLOT(jarFinished()));
 	connect(dljob, SIGNAL(failed()), SLOT(jarFailed()));
diff --git a/logic/OneSixAssets.cpp b/logic/OneSixAssets.cpp
index 5bdd29d7..ca7a5534 100644
--- a/logic/OneSixAssets.cpp
+++ b/logic/OneSixAssets.cpp
@@ -113,7 +113,7 @@ void OneSixAssets::fetchXMLFinished()
 		auto entry = metacache->resolveEntry("assets", keyStr, etagStr);
 		if(entry->stale)
 		{
-			job->add(QUrl(prefix + keyStr), entry);
+			job->addCacheDownload(QUrl(prefix + keyStr), entry);
 		}
 	}
 	if(job->size())
@@ -130,7 +130,7 @@ void OneSixAssets::fetchXMLFinished()
 void OneSixAssets::start()
 {
 	auto job = new DownloadJob("Assets index");
-	job->add(QUrl ( "http://s3.amazonaws.com/Minecraft.Resources/" ));
+	job->addByteArrayDownload(QUrl ( "http://s3.amazonaws.com/Minecraft.Resources/" ));
 	connect ( job, SIGNAL(succeeded()), SLOT ( fetchXMLFinished() ) );
 	index_job.reset ( job );
 	job->start();
diff --git a/logic/OneSixLibrary.cpp b/logic/OneSixLibrary.cpp
index 8da1fde7..63d42646 100644
--- a/logic/OneSixLibrary.cpp
+++ b/logic/OneSixLibrary.cpp
@@ -105,12 +105,24 @@ QString OneSixLibrary::absoluteUrl()
 	return m_absolute_url;
 }
 
+void OneSixLibrary::setHint(QString hint)
+{
+	m_hint = hint;
+}
+
+QString OneSixLibrary::hint()
+{
+	return m_hint;
+}
+
 QJsonObject OneSixLibrary::toJson()
 {
 	QJsonObject libRoot;
 	libRoot.insert("name", m_name);
 	if(m_absolute_url.size())
-		libRoot.insert("MMC-absulute_url", m_absolute_url);
+		libRoot.insert("MMC-absoluteUrl", m_absolute_url);
+	if(m_hint.size())
+		libRoot.insert("MMC-hint", m_hint);
 	if(m_base_url != "https://s3.amazonaws.com/Minecraft.Download/libraries/")
 		libRoot.insert("url", m_base_url);
 	if (isNative() && m_native_suffixes.size())
diff --git a/logic/OneSixLibrary.h b/logic/OneSixLibrary.h
index f3106483..2a16d8e1 100644
--- a/logic/OneSixLibrary.h
+++ b/logic/OneSixLibrary.h
@@ -19,6 +19,8 @@ private:
 	// custom values
 	/// absolute URL. takes precedence over m_download_path, if defined
 	QString m_absolute_url;
+	/// download hint - how to actually get the library
+	QString m_hint;
 
 	// derived values used for real things
 	/// a decent name fit for display
@@ -91,8 +93,12 @@ public:
 	QString downloadUrl();
 	/// Get the relative path where the library should be saved
 	QString storagePath();
-	
+
 	/// set an absolute URL for the library. This is an MMC extension.
 	void setAbsoluteUrl(QString absolute_url);
 	QString absoluteUrl();
+
+	/// set a hint about how to treat the library. This is an MMC extension.
+	void setHint(QString hint);
+	QString hint();
 };
diff --git a/logic/OneSixUpdate.cpp b/logic/OneSixUpdate.cpp
index 73bd9403..41d8f599 100644
--- a/logic/OneSixUpdate.cpp
+++ b/logic/OneSixUpdate.cpp
@@ -75,7 +75,7 @@ void OneSixUpdate::versionFileStart()
 	QString urlstr("http://s3.amazonaws.com/Minecraft.Download/versions/");
 	urlstr += targetVersion->descriptor() + "/" + targetVersion->descriptor() + ".json";
 	auto job = new DownloadJob("Version index");
-	job->add(QUrl(urlstr));
+	job->addByteArrayDownload(QUrl(urlstr));
 	specificVersionDownloadJob.reset(job);
 	connect(specificVersionDownloadJob.data(), SIGNAL(succeeded()),
 			SLOT(versionFileFinished()));
@@ -158,7 +158,7 @@ void OneSixUpdate::jarlibStart()
 	targetstr += version->id + "/" + version->id + ".jar";
 
 	auto job = new DownloadJob("Libraries for instance " + inst->name());
-	job->add(QUrl(urlstr), targetstr);
+	job->addFileDownload(QUrl(urlstr), targetstr);
 	jarlibDownloadJob.reset(job);
 
 	auto libs = version->getActiveNativeLibs();
@@ -171,7 +171,10 @@ void OneSixUpdate::jarlibStart()
 		auto entry = metacache->resolveEntry("libraries", lib->storagePath());
 		if (entry->stale)
 		{
-			jarlibDownloadJob->add(download_path, entry);
+			if(lib->hint() == "forge-pack-xz")
+				jarlibDownloadJob->addForgeXzDownload(download_path, entry);
+			else
+				jarlibDownloadJob->addCacheDownload(download_path, entry);
 		}
 	}
 	connect(jarlibDownloadJob.data(), SIGNAL(succeeded()), SLOT(jarlibFinished()));
diff --git a/logic/OneSixVersion.cpp b/logic/OneSixVersion.cpp
index 663d903a..64a47562 100644
--- a/logic/OneSixVersion.cpp
+++ b/logic/OneSixVersion.cpp
@@ -71,11 +71,21 @@ QSharedPointer<OneSixVersion> fromJsonV4(QJsonObject root,
 		{
 			library->setBaseUrl(urlVal.toString());
 		}
-		auto urlAbsVal = libObj.value("MMC-absulute_url");
+		auto hintVal = libObj.value("MMC-hint");
+		if (hintVal.isString())
+		{
+			library->setHint(hintVal.toString());
+		}
+		auto urlAbsVal = libObj.value("MMC-absoluteUrl");
+		auto urlAbsuVal = libObj.value("MMC-absulute_url"); // compatibility
 		if (urlAbsVal.isString())
 		{
 			library->setAbsoluteUrl(urlAbsVal.toString());
 		}
+		else if(urlAbsuVal.isString())
+		{
+			library->setAbsoluteUrl(urlAbsuVal.toString());
+		}
 		// Extract excludes (if any)
 		auto extractVal = libObj.value("extract");
 		if (extractVal.isObject())
diff --git a/logic/lists/ForgeVersionList.cpp b/logic/lists/ForgeVersionList.cpp
index 721f2c0a..e2adbf3b 100644
--- a/logic/lists/ForgeVersionList.cpp
+++ b/logic/lists/ForgeVersionList.cpp
@@ -162,7 +162,7 @@ void ForgeListLoadTask::executeTask()
 	auto job = new DownloadJob("Version index");
 	// we do not care if the version is stale or not.
 	auto forgeListEntry = MMC->metacache()->resolveEntry("minecraftforge", "list.json");
-	job->add(QUrl(JSON_URL), forgeListEntry);
+	job->addCacheDownload(QUrl(JSON_URL), forgeListEntry);
 	listJob.reset(job);
 	connect(listJob.data(), SIGNAL(succeeded()), SLOT(list_downloaded()));
 	connect(listJob.data(), SIGNAL(failed()), SLOT(versionFileFailed()));
diff --git a/logic/lists/MinecraftVersionList.h b/logic/lists/MinecraftVersionList.h
index fb28ddfe..ed68efbb 100644
--- a/logic/lists/MinecraftVersionList.h
+++ b/logic/lists/MinecraftVersionList.h
@@ -46,7 +46,7 @@ public:
 protected:
 	QList<BaseVersionPtr> m_vlist;
 	
-	bool m_loaded;
+	bool m_loaded = false;
 	
 protected slots:
 	virtual void updateListData(QList<BaseVersionPtr> versions);
diff --git a/logic/net/DownloadJob.cpp b/logic/net/DownloadJob.cpp
index 8da1f39b..03a69555 100644
--- a/logic/net/DownloadJob.cpp
+++ b/logic/net/DownloadJob.cpp
@@ -7,7 +7,7 @@
 
 #include <QDebug>
 
-ByteArrayDownloadPtr DownloadJob::add(QUrl url)
+ByteArrayDownloadPtr DownloadJob::addByteArrayDownload(QUrl url)
 {
 	ByteArrayDownloadPtr ptr(new ByteArrayDownload(url));
 	ptr->index_within_job = downloads.size();
@@ -17,7 +17,7 @@ ByteArrayDownloadPtr DownloadJob::add(QUrl url)
 	return ptr;
 }
 
-FileDownloadPtr DownloadJob::add(QUrl url, QString rel_target_path)
+FileDownloadPtr DownloadJob::addFileDownload(QUrl url, QString rel_target_path)
 {
 	FileDownloadPtr ptr(new FileDownload(url, rel_target_path));
 	ptr->index_within_job = downloads.size();
@@ -27,7 +27,7 @@ FileDownloadPtr DownloadJob::add(QUrl url, QString rel_target_path)
 	return ptr;
 }
 
-CacheDownloadPtr DownloadJob::add(QUrl url, MetaEntryPtr entry)
+CacheDownloadPtr DownloadJob::addCacheDownload(QUrl url, MetaEntryPtr entry)
 {
 	CacheDownloadPtr ptr(new CacheDownload(url, entry));
 	ptr->index_within_job = downloads.size();
@@ -37,6 +37,16 @@ CacheDownloadPtr DownloadJob::add(QUrl url, MetaEntryPtr entry)
 	return ptr;
 }
 
+ForgeXzDownloadPtr DownloadJob::addForgeXzDownload(QUrl url, MetaEntryPtr entry)
+{
+	ForgeXzDownloadPtr ptr(new ForgeXzDownload(url, entry));
+	ptr->index_within_job = downloads.size();
+	downloads.append(ptr);
+	parts_progress.append(part_info());
+	total_progress++;
+	return ptr;
+}
+
 void DownloadJob::partSucceeded(int index)
 {
 	// do progress. all slots are 1 in size at least
diff --git a/logic/net/DownloadJob.h b/logic/net/DownloadJob.h
index 5d5ba01a..8c32950a 100644
--- a/logic/net/DownloadJob.h
+++ b/logic/net/DownloadJob.h
@@ -5,6 +5,7 @@
 #include "FileDownload.h"
 #include "CacheDownload.h"
 #include "HttpMetaCache.h"
+#include "ForgeXzDownload.h"
 #include "logic/tasks/ProgressProvider.h"
 
 class DownloadJob;
@@ -20,9 +21,10 @@ public:
 	explicit DownloadJob(QString job_name)
 		:ProgressProvider(), m_job_name(job_name){};
 	
-	ByteArrayDownloadPtr add(QUrl url);
-	FileDownloadPtr      add(QUrl url, QString rel_target_path);
-	CacheDownloadPtr     add(QUrl url, MetaEntryPtr entry);
+	ByteArrayDownloadPtr addByteArrayDownload(QUrl url);
+	FileDownloadPtr      addFileDownload(QUrl url, QString rel_target_path);
+	CacheDownloadPtr     addCacheDownload(QUrl url, MetaEntryPtr entry);
+	ForgeXzDownloadPtr   addForgeXzDownload(QUrl url, MetaEntryPtr entry);
 	
 	DownloadPtr operator[](int index)
 	{
diff --git a/logic/net/ForgeXzDownload.cpp b/logic/net/ForgeXzDownload.cpp
new file mode 100644
index 00000000..b7e7eedf
--- /dev/null
+++ b/logic/net/ForgeXzDownload.cpp
@@ -0,0 +1,277 @@
+#include "MultiMC.h"
+#include "ForgeXzDownload.h"
+#include <pathutils.h>
+
+#include <QCryptographicHash>
+#include <QFileInfo>
+#include <QDateTime>
+#include <QDebug>
+
+ForgeXzDownload::ForgeXzDownload(QUrl url, MetaEntryPtr entry)
+	: Download()
+{
+	QString urlstr = url.toString();
+	urlstr.append(".pack.xz");
+	m_url = QUrl(urlstr);
+	m_entry = entry;
+	m_target_path = entry->getFullPath();
+	m_status = Job_NotStarted;
+	m_opened_for_saving = false;
+}
+
+void ForgeXzDownload::start()
+{
+	if (!m_entry->stale)
+	{
+		emit succeeded(index_within_job);
+		return;
+	}
+	// can we actually create the real, final file?
+	if (!ensureFilePathExists(m_target_path))
+	{
+		emit failed(index_within_job);
+		return;
+	}
+	qDebug() << "Downloading " << m_url.toString();
+	QNetworkRequest request(m_url);
+	request.setRawHeader(QString("If-None-Match").toLatin1(), m_entry->etag.toLatin1());
+
+	auto worker = MMC->qnam();
+	QNetworkReply *rep = worker->get(request);
+
+	m_reply = QSharedPointer<QNetworkReply>(rep, &QObject::deleteLater);
+	connect(rep, SIGNAL(downloadProgress(qint64, qint64)),
+			SLOT(downloadProgress(qint64, qint64)));
+	connect(rep, SIGNAL(finished()), SLOT(downloadFinished()));
+	connect(rep, SIGNAL(error(QNetworkReply::NetworkError)),
+			SLOT(downloadError(QNetworkReply::NetworkError)));
+	connect(rep, SIGNAL(readyRead()), SLOT(downloadReadyRead()));
+}
+
+void ForgeXzDownload::downloadProgress(qint64 bytesReceived, qint64 bytesTotal)
+{
+	emit progress(index_within_job, bytesReceived, bytesTotal);
+}
+
+void ForgeXzDownload::downloadError(QNetworkReply::NetworkError error)
+{
+	// error happened during download.
+	// TODO: log the reason why
+	m_status = Job_Failed;
+}
+
+void ForgeXzDownload::downloadFinished()
+{
+	// if the download succeeded
+	if (m_status != Job_Failed)
+	{
+		// nothing went wrong...
+		m_status = Job_Finished;
+		if (m_opened_for_saving)
+		{
+			// we actually downloaded something! process and isntall it
+			decompressAndInstall();
+			return;
+		}
+		else
+		{
+			// something bad happened
+			m_pack200_xz_file.remove();
+			m_reply.clear();
+			emit failed(index_within_job);
+			return;
+		}
+	}
+	// else the download failed
+	else
+	{
+		m_pack200_xz_file.close();
+		m_pack200_xz_file.remove();
+		m_reply.clear();
+		emit failed(index_within_job);
+		return;
+	}
+}
+
+void ForgeXzDownload::downloadReadyRead()
+{
+	
+	if (!m_opened_for_saving)
+	{
+		if (!m_pack200_xz_file.open())
+		{
+			/*
+			* Can't open the file... the job failed
+			*/
+			m_reply->abort();
+			emit failed(index_within_job);
+			return;
+		}
+		m_opened_for_saving = true;
+	}
+	m_pack200_xz_file.write(m_reply->readAll());
+}
+
+#include "xz.h"
+#include "unpack200.h"
+
+const size_t buffer_size = 8196;
+
+void ForgeXzDownload::decompressAndInstall()
+{
+	// rewind the downloaded temp file
+	m_pack200_xz_file.seek(0);
+	// de-xz'd file
+	QTemporaryFile pack200_file;
+	pack200_file.open();
+
+	bool xz_success = false;
+	// first, de-xz
+	{
+		uint8_t in[buffer_size];
+		uint8_t out[buffer_size];
+		struct xz_buf b;
+		struct xz_dec *s;
+		enum xz_ret ret;
+		xz_crc32_init();
+		xz_crc64_init();
+		s = xz_dec_init(XZ_DYNALLOC, 1 << 26);
+		if (s == nullptr)
+		{
+			xz_dec_end(s);
+			emit failed(index_within_job);
+			return;
+		}
+		b.in = in;
+		b.in_pos = 0;
+		b.in_size = 0;
+		b.out = out;
+		b.out_pos = 0;
+		b.out_size = buffer_size;
+		while (!xz_success)
+		{
+			if (b.in_pos == b.in_size)
+			{
+				b.in_size = m_pack200_xz_file.read((char*)in, sizeof(in));
+				b.in_pos = 0;
+			}
+
+			ret = xz_dec_run(s, &b);
+
+			if (b.out_pos == sizeof(out))
+			{
+				if (pack200_file.write((char*)out, b.out_pos) != b.out_pos)
+				{
+					// msg = "Write error\n";
+					xz_dec_end(s);
+					emit failed(index_within_job);
+					return;
+				}
+
+				b.out_pos = 0;
+			}
+
+			if (ret == XZ_OK)
+				continue;
+
+			if (ret == XZ_UNSUPPORTED_CHECK)
+			{
+				// unsupported check. this is OK, but we should log this
+				continue;
+			}
+
+			if (pack200_file.write((char*)out, b.out_pos) != b.out_pos )
+			{
+				// write error
+				pack200_file.close();
+				xz_dec_end(s);
+				return;
+			}
+
+			switch (ret)
+			{
+			case XZ_STREAM_END:
+				xz_dec_end(s);
+				xz_success = true;
+				break;
+
+			case XZ_MEM_ERROR:
+				qDebug() << "Memory allocation failed\n";
+				xz_dec_end(s);
+				emit failed(index_within_job);
+				return;
+
+			case XZ_MEMLIMIT_ERROR:
+				qDebug() << "Memory usage limit reached\n";
+				xz_dec_end(s);
+				emit failed(index_within_job);
+				return;
+
+			case XZ_FORMAT_ERROR:
+				qDebug() << "Not a .xz file\n";
+				xz_dec_end(s);
+				emit failed(index_within_job);
+				return;
+
+			case XZ_OPTIONS_ERROR:
+				qDebug() << "Unsupported options in the .xz headers\n";
+				xz_dec_end(s);
+				emit failed(index_within_job);
+				return;
+
+			case XZ_DATA_ERROR:
+			case XZ_BUF_ERROR:
+				qDebug() << "File is corrupt\n";
+				xz_dec_end(s);
+				emit failed(index_within_job);
+				return;
+
+			default:
+				qDebug() << "Bug!\n";
+				xz_dec_end(s);
+				emit failed(index_within_job);
+				return;
+			}
+		}
+	}
+	
+	// revert pack200
+	pack200_file.close();
+	QString pack_name = pack200_file.fileName();
+	try
+	{
+		unpack_200(pack_name.toStdString(), m_target_path.toStdString());
+	}
+	catch(std::runtime_error & err)
+	{
+		qDebug() << "Error unpacking " << pack_name.toUtf8() << " : " << err.what();
+		QFile f(m_target_path);
+		if(f.exists())
+			f.remove();
+		emit failed(index_within_job);
+		return;
+	}
+	
+	QFile jar_file(m_target_path);
+
+	if (!jar_file.open(QIODevice::ReadOnly))
+	{
+		jar_file.remove();
+		emit failed(index_within_job);
+		return;
+	}
+	m_entry->md5sum = QCryptographicHash::hash(jar_file.readAll(), QCryptographicHash::Md5)
+			.toHex()
+			.constData();
+	jar_file.close();
+	
+	QFileInfo output_file_info(m_target_path);
+	m_entry->etag = m_reply->rawHeader("ETag").constData();
+	m_entry->last_changed_timestamp =
+		output_file_info.lastModified().toUTC().toMSecsSinceEpoch();
+	m_entry->stale = false;
+	MMC->metacache()->updateEntry(m_entry);
+
+	m_reply.clear();
+	emit succeeded(index_within_job);
+}
diff --git a/logic/net/ForgeXzDownload.h b/logic/net/ForgeXzDownload.h
new file mode 100644
index 00000000..8cb47783
--- /dev/null
+++ b/logic/net/ForgeXzDownload.h
@@ -0,0 +1,35 @@
+#pragma once
+
+#include "Download.h"
+#include "HttpMetaCache.h"
+#include <QFile>
+#include <QTemporaryFile>
+
+class ForgeXzDownload : public Download
+{
+	Q_OBJECT
+public:
+	MetaEntryPtr m_entry;
+	/// is the saving file already open?
+	bool m_opened_for_saving;
+	/// if saving to file, use the one specified in this string
+	QString m_target_path;
+	/// this is the output file, if any
+	QTemporaryFile m_pack200_xz_file;
+
+public:
+	explicit ForgeXzDownload(QUrl url, MetaEntryPtr entry);
+	
+protected slots:
+	virtual void downloadProgress(qint64 bytesReceived, qint64 bytesTotal);
+	virtual void downloadError(QNetworkReply::NetworkError error);
+	virtual void downloadFinished();
+	virtual void downloadReadyRead();
+	
+public slots:
+	virtual void start();
+private:
+	void decompressAndInstall();
+};
+
+typedef QSharedPointer<ForgeXzDownload> ForgeXzDownloadPtr;