diff --git a/launcher/CMakeLists.txt b/launcher/CMakeLists.txt
index cff07b4b..1a5579c8 100644
--- a/launcher/CMakeLists.txt
+++ b/launcher/CMakeLists.txt
@@ -494,6 +494,8 @@ set(API_SOURCES
     modplatform/modrinth/ModrinthAPI.cpp
     modplatform/helpers/NetworkModAPI.h
     modplatform/helpers/NetworkModAPI.cpp
+    modplatform/helpers/HashUtils.h
+    modplatform/helpers/HashUtils.cpp
 )
 
 set(FTB_SOURCES
diff --git a/launcher/modplatform/EnsureMetadataTask.cpp b/launcher/modplatform/EnsureMetadataTask.cpp
index 60c54c4e..42137398 100644
--- a/launcher/modplatform/EnsureMetadataTask.cpp
+++ b/launcher/modplatform/EnsureMetadataTask.cpp
@@ -3,81 +3,73 @@
 #include <MurmurHash2.h>
 #include <QDebug>
 
-#include "FileSystem.h"
 #include "Json.h"
+
 #include "minecraft/mod/Mod.h"
 #include "minecraft/mod/tasks/LocalModUpdateTask.h"
+
 #include "modplatform/flame/FlameAPI.h"
 #include "modplatform/flame/FlameModIndex.h"
 #include "modplatform/modrinth/ModrinthAPI.h"
 #include "modplatform/modrinth/ModrinthPackIndex.h"
+
 #include "net/NetJob.h"
-#include "tasks/MultipleOptionsTask.h"
 
 static ModPlatform::ProviderCapabilities ProviderCaps;
 
 static ModrinthAPI modrinth_api;
 static FlameAPI flame_api;
 
-EnsureMetadataTask::EnsureMetadataTask(Mod* mod, QDir dir, ModPlatform::Provider prov) : Task(nullptr), m_index_dir(dir), m_provider(prov)
+EnsureMetadataTask::EnsureMetadataTask(Mod* mod, QDir dir, ModPlatform::Provider prov)
+    : Task(nullptr), m_index_dir(dir), m_provider(prov), m_hashing_task(nullptr), m_current_task(nullptr)
 {
-    auto hash = getHash(mod);
-    if (hash.isEmpty())
-        emitFail(mod);
-    else
-        m_mods.insert(hash, mod);
+    auto hash_task = createNewHash(mod);
+    if (!hash_task)
+        return;
+    connect(hash_task.get(), &Task::succeeded, [this, hash_task, mod] { m_mods.insert(hash_task->getResult(), mod); });
+    connect(hash_task.get(), &Task::failed, [this, hash_task, mod] { emitFail(mod, "", RemoveFromList::No); });
+    hash_task->start();
 }
 
 EnsureMetadataTask::EnsureMetadataTask(QList<Mod*>& mods, QDir dir, ModPlatform::Provider prov)
-    : Task(nullptr), m_index_dir(dir), m_provider(prov)
+    : Task(nullptr), m_index_dir(dir), m_provider(prov), m_current_task(nullptr)
 {
+    m_hashing_task = new ConcurrentTask(this, "MakeHashesTask", 10);
     for (auto* mod : mods) {
-        if (!mod->valid()) {
-            emitFail(mod);
+        auto hash_task = createNewHash(mod);
+        if (!hash_task)
             continue;
-        }
-
-        auto hash = getHash(mod);
-        if (hash.isEmpty()) {
-            emitFail(mod);
-            continue;
-        }
-
-        m_mods.insert(hash, mod);
+        connect(hash_task.get(), &Task::succeeded, [this, hash_task, mod] { m_mods.insert(hash_task->getResult(), mod); });
+        connect(hash_task.get(), &Task::failed, [this, hash_task, mod] { emitFail(mod, "", RemoveFromList::No); });
+        m_hashing_task->addTask(hash_task);
     }
 }
 
-QString EnsureMetadataTask::getHash(Mod* mod)
+Hashing::Hasher::Ptr EnsureMetadataTask::createNewHash(Mod* mod)
 {
-    /* Here we create a mapping hash -> mod, because we need that relationship to parse the API routes */
-    QByteArray jar_data;
-    try {
-        jar_data = FS::read(mod->fileinfo().absoluteFilePath());
-    } catch (FS::FileSystemException& e) {
-        qCritical() << QString("Failed to open / read JAR file of %1").arg(mod->name());
-        qCritical() << QString("Reason: ") << e.cause();
+    if (!mod || !mod->valid() || mod->type() == Mod::MOD_FOLDER)
+        return nullptr;
 
-        return {};
+    return Hashing::createHasher(mod->fileinfo().absoluteFilePath(), m_provider);
+}
+
+QString EnsureMetadataTask::getExistingHash(Mod* mod)
+{
+    // Check for already computed hashes
+    // (linear on the number of mods vs. linear on the size of the mod's JAR)
+    auto it = m_mods.keyValueBegin();
+    while (it != m_mods.keyValueEnd()) {
+        if ((*it).second == mod)
+            break;
+        it++;
     }
 
-    switch (m_provider) {
-        case ModPlatform::Provider::MODRINTH: {
-            auto hash_type = ProviderCaps.hashType(ModPlatform::Provider::MODRINTH).first();
-
-            return QString(ProviderCaps.hash(ModPlatform::Provider::MODRINTH, jar_data, hash_type).toHex());
-        }
-        case ModPlatform::Provider::FLAME: {
-            QByteArray jar_data_treated;
-            for (char c : jar_data) {
-                // CF-specific
-                if (!(c == 9 || c == 10 || c == 13 || c == 32))
-                    jar_data_treated.push_back(c);
-            }
-
-            return QString::number(MurmurHash2(jar_data_treated, jar_data_treated.length()));
-        }
+    // We already have the hash computed
+    if (it != m_mods.keyValueEnd()) {
+        return (*it).first;
     }
 
+    // No existing hash
     return {};
 }
 
@@ -127,11 +119,9 @@ void EnsureMetadataTask::executeTask()
     }
 
     auto invalidade_leftover = [this] {
-        QMutableHashIterator<QString, Mod*> mods_iter(m_mods);
-        while (mods_iter.hasNext()) {
-            auto mod = mods_iter.next();
-            emitFail(mod.value());
-        }
+        for (auto mod = m_mods.constBegin(); mod != m_mods.constEnd(); mod++)
+            emitFail(mod.value(), mod.key(), RemoveFromList::No);
+        m_mods.clear();
 
         emitSucceeded();
     };
@@ -178,20 +168,44 @@ void EnsureMetadataTask::executeTask()
     version_task->start();
 }
 
-void EnsureMetadataTask::emitReady(Mod* m)
+void EnsureMetadataTask::emitReady(Mod* m, QString key, RemoveFromList remove)
 {
+    if (!m) {
+        qCritical() << "Tried to mark a null mod as ready.";
+        if (!key.isEmpty())
+            m_mods.remove(key);
+
+        return;
+    }
+
     qDebug() << QString("Generated metadata for %1").arg(m->name());
     emit metadataReady(m);
 
-    m_mods.remove(getHash(m));
+    if (remove == RemoveFromList::Yes) {
+        if (key.isEmpty())
+            key = getExistingHash(m);
+        m_mods.remove(key);
+    }
 }
 
-void EnsureMetadataTask::emitFail(Mod* m)
+void EnsureMetadataTask::emitFail(Mod* m, QString key, RemoveFromList remove)
 {
+    if (!m) {
+        qCritical() << "Tried to mark a null mod as failed.";
+        if (!key.isEmpty())
+            m_mods.remove(key);
+
+        return;
+    }
+
     qDebug() << QString("Failed to generate metadata for %1").arg(m->name());
     emit metadataFailed(m);
 
-    m_mods.remove(getHash(m));
+    if (remove == RemoveFromList::Yes) {
+        if (key.isEmpty())
+            key = getExistingHash(m);
+        m_mods.remove(key);
+    }
 }
 
 // Modrinth
diff --git a/launcher/modplatform/EnsureMetadataTask.h b/launcher/modplatform/EnsureMetadataTask.h
index 79db6976..a8b0851e 100644
--- a/launcher/modplatform/EnsureMetadataTask.h
+++ b/launcher/modplatform/EnsureMetadataTask.h
@@ -1,12 +1,14 @@
 #pragma once
 
 #include "ModIndex.h"
-#include "tasks/SequentialTask.h"
 #include "net/NetJob.h"
 
+#include "modplatform/helpers/HashUtils.h"
+
+#include "tasks/ConcurrentTask.h"
+
 class Mod;
 class QDir;
-class MultipleOptionsTask;
 
 class EnsureMetadataTask : public Task {
     Q_OBJECT
@@ -17,6 +19,8 @@ class EnsureMetadataTask : public Task {
 
     ~EnsureMetadataTask() = default;
 
+    Task::Ptr getHashingTask() { return m_hashing_task; }
+
    public slots:
     bool abort() override;
    protected slots:
@@ -31,10 +35,16 @@ class EnsureMetadataTask : public Task {
     auto flameProjectsTask() -> NetJob::Ptr;
 
     // Helpers
-    void emitReady(Mod*);
-    void emitFail(Mod*);
+    enum class RemoveFromList {
+        Yes,
+        No
+    };
+    void emitReady(Mod*, QString key = {}, RemoveFromList = RemoveFromList::Yes);
+    void emitFail(Mod*, QString key = {}, RemoveFromList = RemoveFromList::Yes);
 
-    auto getHash(Mod*) -> QString;
+    // Hashes and stuff
+    auto createNewHash(Mod*) -> Hashing::Hasher::Ptr;
+    auto getExistingHash(Mod*) -> QString;
 
    private slots:
     void modrinthCallback(ModPlatform::IndexedPack& pack, ModPlatform::IndexedVersion& ver, Mod*);
@@ -50,5 +60,6 @@ class EnsureMetadataTask : public Task {
     ModPlatform::Provider m_provider;
 
     QHash<QString, ModPlatform::IndexedVersion> m_temp_versions;
+    ConcurrentTask* m_hashing_task;
     NetJob* m_current_task;
 };
diff --git a/launcher/modplatform/ModIndex.cpp b/launcher/modplatform/ModIndex.cpp
index 3c4b7887..34fd9f30 100644
--- a/launcher/modplatform/ModIndex.cpp
+++ b/launcher/modplatform/ModIndex.cpp
@@ -19,6 +19,8 @@
 #include "modplatform/ModIndex.h"
 
 #include <QCryptographicHash>
+#include <QDebug>
+#include <QIODevice>
 
 namespace ModPlatform {
 
@@ -53,34 +55,26 @@ auto ProviderCapabilities::hashType(Provider p) -> QStringList
     }
     return {};
 }
-auto ProviderCapabilities::hash(Provider p, QByteArray& data, QString type) -> QByteArray
+
+auto ProviderCapabilities::hash(Provider p, QIODevice* device, QString type) -> QString
 {
+    QCryptographicHash::Algorithm algo = QCryptographicHash::Sha1;
     switch (p) {
         case Provider::MODRINTH: {
-            // NOTE: Data is the result of reading the entire JAR file!
-
-            // If 'type' was specified, we use that
-            if (!type.isEmpty() && hashType(p).contains(type)) {
-                if (type == "sha512")
-                    return QCryptographicHash::hash(data, QCryptographicHash::Sha512);
-                else if (type == "sha1")
-                    return QCryptographicHash::hash(data, QCryptographicHash::Sha1);
-            }
-
-            return QCryptographicHash::hash(data, QCryptographicHash::Sha512);
+            algo = (type == "sha1") ? QCryptographicHash::Sha1 : QCryptographicHash::Sha512;
+            break;
         }
         case Provider::FLAME:
-            // If 'type' was specified, we use that
-            if (!type.isEmpty() && hashType(p).contains(type)) {
-                if(type == "sha1")
-                    return QCryptographicHash::hash(data, QCryptographicHash::Sha1);
-                else if (type == "md5")
-                    return QCryptographicHash::hash(data, QCryptographicHash::Md5);
-            }
-            
+            algo = (type == "sha1") ? QCryptographicHash::Sha1 : QCryptographicHash::Md5;
             break;
     }
-    return {};
+
+    QCryptographicHash hash(algo);
+    if(!hash.addData(device))
+        qCritical() << "Failed to read JAR to create hash!";
+
+    Q_ASSERT(hash.result().length() == hash.hashLength(algo));
+    return { hash.result().toHex() };
 }
 
 }  // namespace ModPlatform
diff --git a/launcher/modplatform/ModIndex.h b/launcher/modplatform/ModIndex.h
index dc297d03..89fe1c5c 100644
--- a/launcher/modplatform/ModIndex.h
+++ b/launcher/modplatform/ModIndex.h
@@ -24,6 +24,8 @@
 #include <QVariant>
 #include <QVector>
 
+class QIODevice;
+
 namespace ModPlatform {
 
 enum class Provider {
@@ -36,7 +38,7 @@ class ProviderCapabilities {
     auto name(Provider) -> const char*;
     auto readableName(Provider) -> QString;
     auto hashType(Provider) -> QStringList;
-    auto hash(Provider, QByteArray&, QString type = "") -> QByteArray;
+    auto hash(Provider, QIODevice*, QString type = "") -> QString;
 };
 
 struct ModpackAuthor {
diff --git a/launcher/modplatform/helpers/HashUtils.cpp b/launcher/modplatform/helpers/HashUtils.cpp
new file mode 100644
index 00000000..a7bbaba5
--- /dev/null
+++ b/launcher/modplatform/helpers/HashUtils.cpp
@@ -0,0 +1,81 @@
+#include "HashUtils.h"
+
+#include <QDebug>
+#include <QFile>
+
+#include "FileSystem.h"
+
+#include <MurmurHash2.h>
+
+namespace Hashing {
+
+static ModPlatform::ProviderCapabilities ProviderCaps;
+
+Hasher::Ptr createHasher(QString file_path, ModPlatform::Provider provider)
+{
+    switch (provider) {
+        case ModPlatform::Provider::MODRINTH:
+            return createModrinthHasher(file_path);
+        case ModPlatform::Provider::FLAME:
+            return createFlameHasher(file_path);
+        default:
+            qCritical() << "[Hashing]"
+                        << "Unrecognized mod platform!";
+            return nullptr;
+    }
+}
+
+Hasher::Ptr createModrinthHasher(QString file_path)
+{
+    return new ModrinthHasher(file_path);
+}
+
+Hasher::Ptr createFlameHasher(QString file_path)
+{
+    return new FlameHasher(file_path);
+}
+
+void ModrinthHasher::executeTask()
+{
+    QFile file(m_path);
+
+    try {
+        file.open(QFile::ReadOnly);
+    } catch (FS::FileSystemException& e) {
+        qCritical() << QString("Failed to open JAR file in %1").arg(m_path);
+        qCritical() << QString("Reason: ") << e.cause();
+
+        emitFailed("Failed to open file for hashing.");
+        return;
+    }
+
+    auto hash_type = ProviderCaps.hashType(ModPlatform::Provider::MODRINTH).first();
+    m_hash = ProviderCaps.hash(ModPlatform::Provider::MODRINTH, &file, hash_type);
+
+    file.close();
+
+    if (m_hash.isEmpty()) {
+        emitFailed("Empty hash!");
+    } else {
+        emitSucceeded();
+    }
+}
+
+void FlameHasher::executeTask()
+{
+    // CF-specific
+    auto should_filter_out = [](char c) { return (c == 9 || c == 10 || c == 13 || c == 32); };
+
+    std::ifstream file_stream(m_path.toStdString(), std::ifstream::binary);
+    // TODO: This is very heavy work, but apparently QtConcurrent can't use move semantics, so we can't boop this to another thread.
+    // How do we make this non-blocking then?
+    m_hash = QString::number(MurmurHash2(std::move(file_stream), 4 * MiB, should_filter_out));
+
+    if (m_hash.isEmpty()) {
+        emitFailed("Empty hash!");
+    } else {
+        emitSucceeded();
+    }
+}
+
+}  // namespace Hashing
diff --git a/launcher/modplatform/helpers/HashUtils.h b/launcher/modplatform/helpers/HashUtils.h
new file mode 100644
index 00000000..38fddf03
--- /dev/null
+++ b/launcher/modplatform/helpers/HashUtils.h
@@ -0,0 +1,47 @@
+#pragma once
+
+#include <QString>
+
+#include "modplatform/ModIndex.h"
+#include "tasks/Task.h"
+
+namespace Hashing {
+
+class Hasher : public Task {
+   public:
+    using Ptr = shared_qobject_ptr<Hasher>;
+
+    Hasher(QString file_path) : m_path(std::move(file_path)) {}
+
+    /* We can't really abort this task, but we can say we aborted and finish our thing quickly :) */
+    bool abort() override { return true; }
+
+    void executeTask() override = 0;
+
+    QString getResult() const { return m_hash; };
+    QString getPath() const { return m_path; };
+
+   protected:
+    QString m_hash;
+    QString m_path;
+};
+
+class FlameHasher : public Hasher {
+   public:
+    FlameHasher(QString file_path) : Hasher(file_path) { setObjectName(QString("FlameHasher: %1").arg(file_path)); }
+
+    void executeTask() override;
+};
+
+class ModrinthHasher : public Hasher {
+   public:
+    ModrinthHasher(QString file_path) : Hasher(file_path) { setObjectName(QString("ModrinthHasher: %1").arg(file_path)); }
+
+    void executeTask() override;
+};
+
+Hasher::Ptr createHasher(QString file_path, ModPlatform::Provider provider);
+Hasher::Ptr createFlameHasher(QString file_path);
+Hasher::Ptr createModrinthHasher(QString file_path);
+
+}  // namespace Hashing
diff --git a/launcher/modplatform/modrinth/ModrinthCheckUpdate.cpp b/launcher/modplatform/modrinth/ModrinthCheckUpdate.cpp
index 79d8edf7..e2d27547 100644
--- a/launcher/modplatform/modrinth/ModrinthCheckUpdate.cpp
+++ b/launcher/modplatform/modrinth/ModrinthCheckUpdate.cpp
@@ -2,11 +2,14 @@
 #include "ModrinthAPI.h"
 #include "ModrinthPackIndex.h"
 
-#include "FileSystem.h"
 #include "Json.h"
 
 #include "ModDownloadTask.h"
 
+#include "modplatform/helpers/HashUtils.h"
+
+#include "tasks/ConcurrentTask.h"
+
 static ModrinthAPI api;
 static ModPlatform::ProviderCapabilities ProviderCaps;
 
@@ -32,6 +35,8 @@ void ModrinthCheckUpdate::executeTask()
     // Create all hashes
     QStringList hashes;
     auto best_hash_type = ProviderCaps.hashType(ModPlatform::Provider::MODRINTH).first();
+
+    ConcurrentTask hashing_task(this, "MakeModrinthHashesTask", 10);
     for (auto* mod : m_mods) {
         if (!mod->enabled()) {
             emit checkFailed(mod, tr("Disabled mods won't be updated, to prevent mod duplication issues!"));
@@ -44,25 +49,25 @@ void ModrinthCheckUpdate::executeTask()
         // need to generate a new hash if the current one is innadequate
         // (though it will rarely happen, if at all)
         if (mod->metadata()->hash_format != best_hash_type) {
-            QByteArray jar_data;
-
-            try {
-                jar_data = FS::read(mod->fileinfo().absoluteFilePath());
-            } catch (FS::FileSystemException& e) {
-                qCritical() << QString("Failed to open / read JAR file of %1").arg(mod->name());
-                qCritical() << QString("Reason: ") << e.cause();
-
-                failed(e.what());
-                return;
-            }
-
-            hash = QString(ProviderCaps.hash(ModPlatform::Provider::MODRINTH, jar_data, best_hash_type).toHex());
+            auto hash_task = Hashing::createModrinthHasher(mod->fileinfo().absoluteFilePath());
+            connect(hash_task.get(), &Task::succeeded, [&] {
+                QString hash (hash_task->getResult());
+                hashes.append(hash);
+                mappings.insert(hash, mod);
+            });
+            connect(hash_task.get(), &Task::failed, [this, hash_task] { failed("Failed to generate hash"); });
+            hashing_task.addTask(hash_task);
+        } else {
+            hashes.append(hash);
+            mappings.insert(hash, mod);
         }
-
-        hashes.append(hash);
-        mappings.insert(hash, mod);
     }
 
+    QEventLoop loop;
+    connect(&hashing_task, &Task::finished, [&loop]{ loop.quit(); });
+    hashing_task.start();
+    loop.exec();
+
     auto* response = new QByteArray();
     auto job = api.latestVersions(hashes, best_hash_type, m_game_versions, m_loaders, response);
 
diff --git a/launcher/tasks/ConcurrentTask.cpp b/launcher/tasks/ConcurrentTask.cpp
index b88cfb13..ab7cbd03 100644
--- a/launcher/tasks/ConcurrentTask.cpp
+++ b/launcher/tasks/ConcurrentTask.cpp
@@ -1,10 +1,11 @@
 #include "ConcurrentTask.h"
 
 #include <QDebug>
+#include <QCoreApplication>
 
 ConcurrentTask::ConcurrentTask(QObject* parent, QString task_name, int max_concurrent)
     : Task(parent), m_name(task_name), m_total_max_size(max_concurrent)
-{}
+{ setObjectName(task_name); }
 
 ConcurrentTask::~ConcurrentTask()
 {
@@ -36,8 +37,9 @@ void ConcurrentTask::executeTask()
 {
     m_total_size = m_queue.size();
 
-    for (int i = 0; i < m_total_max_size; i++)
-        startNext();
+    for (int i = 0; i < m_total_max_size; i++) {
+        QMetaObject::invokeMethod(this, &ConcurrentTask::startNext, Qt::QueuedConnection);
+    }
 }
 
 bool ConcurrentTask::abort()
@@ -91,6 +93,8 @@ void ConcurrentTask::startNext()
     setStepStatus(next->isMultiStep() ? next->getStepStatus() : next->getStatus());
     updateState();
 
+    QCoreApplication::processEvents();
+
     next->start();
 }
 
diff --git a/launcher/ui/dialogs/ModUpdateDialog.cpp b/launcher/ui/dialogs/ModUpdateDialog.cpp
index d73c8ebb..936fd99d 100644
--- a/launcher/ui/dialogs/ModUpdateDialog.cpp
+++ b/launcher/ui/dialogs/ModUpdateDialog.cpp
@@ -270,6 +270,10 @@ auto ModUpdateDialog::ensureMetadata() -> bool
         connect(modrinth_task, &EnsureMetadataTask::metadataFailed, [this, &should_try_others](Mod* candidate) {
             onMetadataFailed(candidate, should_try_others.find(candidate->internal_id()).value(), ModPlatform::Provider::MODRINTH);
         });
+
+        if (modrinth_task->getHashingTask())
+            seq.addTask(modrinth_task->getHashingTask());
+
         seq.addTask(modrinth_task);
     }
 
@@ -279,6 +283,10 @@ auto ModUpdateDialog::ensureMetadata() -> bool
         connect(flame_task, &EnsureMetadataTask::metadataFailed, [this, &should_try_others](Mod* candidate) {
             onMetadataFailed(candidate, should_try_others.find(candidate->internal_id()).value(), ModPlatform::Provider::FLAME);
         });
+
+        if (flame_task->getHashingTask())
+            seq.addTask(flame_task->getHashingTask());
+
         seq.addTask(flame_task);
     }
 
diff --git a/libraries/murmur2/src/MurmurHash2.cpp b/libraries/murmur2/src/MurmurHash2.cpp
index 3e52e6d1..b625efb1 100644
--- a/libraries/murmur2/src/MurmurHash2.cpp
+++ b/libraries/murmur2/src/MurmurHash2.cpp
@@ -1,86 +1,110 @@
 //-----------------------------------------------------------------------------
 // MurmurHash2 was written by Austin Appleby, and is placed in the public
 // domain. The author hereby disclaims copyright to this source code.
-
-// Note - This code makes a few assumptions about how your machine behaves -
-
-// 1. We can read a 4-byte value from any address without crashing
-// 2. sizeof(int) == 4
-
-// And it has a few limitations -
-
-// 1. It will not work incrementally.
-// 2. It will not produce the same results on little-endian and big-endian
-//    machines.
+//
+// This was modified as to possibilitate it's usage incrementally.
+// Those modifications are also placed in the public domain, and the author of
+// such modifications hereby disclaims copyright to this source code.
 
 #include "MurmurHash2.h"
 
 //-----------------------------------------------------------------------------
-// Platform-specific functions and macros
 
-// Microsoft Visual Studio
+// 'm' and 'r' are mixing constants generated offline.
+// They're not really 'magic', they just happen to work well.
+const uint32_t m = 0x5bd1e995;
+const int r = 24;
 
-#if defined(_MSC_VER)
-
-#define BIG_CONSTANT(x) (x)
-
-// Other compilers
-
-#else	// defined(_MSC_VER)
-
-#define BIG_CONSTANT(x) (x##LLU)
-
-#endif // !defined(_MSC_VER)
-
-//-----------------------------------------------------------------------------
-
-uint64_t MurmurHash2 ( const void* key, int len, uint32_t seed )
+uint32_t MurmurHash2(std::ifstream&& file_stream, std::size_t buffer_size, std::function<bool(char)> filter_out)
 {
-  // 'm' and 'r' are mixing constants generated offline.
-  // They're not really 'magic', they just happen to work well.
+    auto* buffer = new char[buffer_size];
+    char data[4];
 
-  const uint32_t m = 0x5bd1e995;
-  const int r = 24;
+    int read = 0;
+    uint32_t size = 0;
 
-  // Initialize the hash to a 'random' value
+    // We need the size without the filtered out characters before actually calculating the hash,
+    // to setup the initial value for the hash.
+    do {
+        file_stream.read(buffer, buffer_size);
+        read = file_stream.gcount();
+        for (int i = 0; i < read; i++) {
+            if (!filter_out(buffer[i]))
+                size += 1;
+        }
+    } while (!file_stream.eof());
 
-  uint32_t h = seed ^ len;
+    file_stream.clear();
+    file_stream.seekg(0, file_stream.beg);
 
-  // Mix 4 bytes at a time into the hash
-  const auto* data = (const unsigned char*) key;
-  while(len >= 4)
-  {
-    uint32_t k = *(uint32_t*)data;
+    int index = 0;
 
-    k *= m;
-    k ^= k >> r;
-    k *= m;
+    // This forces a seed of 1.
+    IncrementalHashInfo info{ (uint32_t)1 ^ size, (uint32_t)size };
+    do {
+        file_stream.read(buffer, buffer_size);
+        read = file_stream.gcount();
+        for (int i = 0; i < read; i++) {
+            char c = buffer[i];
 
-    h *= m;
-    h ^= k;
+            if (filter_out(c))
+                continue;
 
-    data += 4*sizeof(char);
-    len -= 4;
-  }
+            data[index] = c;
+            index = (index + 1) % 4;
 
-  // Handle the last few bytes of the input array
+            // Mix 4 bytes at a time into the hash
+            if (index == 0)
+                FourBytes_MurmurHash2((unsigned char*)&data, info);
+        }
+    } while (!file_stream.eof());
 
-  switch(len)
-  {
-  case 3: h ^= data[2] << 16;
-  case 2: h ^= data[1] << 8;
-  case 1: h ^= data[0];
-      h *= m;
-  };
+    // Do one last bit shuffle in the hash
+    FourBytes_MurmurHash2((unsigned char*)&data, info);
 
-  // Do a few final mixes of the hash to ensure the last few
-  // bytes are well-incorporated.
+    delete[] buffer;
 
-  h ^= h >> 13;
-  h *= m;
-  h ^= h >> 15;
+    file_stream.close();
+    return info.h;
+}
 
-  return h;
-} 
+void FourBytes_MurmurHash2(const unsigned char* data, IncrementalHashInfo& prev)
+{
+    if (prev.len >= 4) {
+        // Not the final mix
+        uint32_t k = *(uint32_t*)data;
+
+        k *= m;
+        k ^= k >> r;
+        k *= m;
+
+        prev.h *= m;
+        prev.h ^= k;
+
+        prev.len -= 4;
+    } else {
+        // The final mix
+
+        // Handle the last few bytes of the input array
+        switch (prev.len) {
+            case 3:
+                prev.h ^= data[2] << 16;
+            case 2:
+                prev.h ^= data[1] << 8;
+            case 1:
+                prev.h ^= data[0];
+                prev.h *= m;
+        };
+
+        // Do a few final mixes of the hash to ensure the last few
+        // bytes are well-incorporated.
+
+        prev.h ^= prev.h >> 13;
+        prev.h *= m;
+        prev.h ^= prev.h >> 15;
+
+        prev.len = 0;
+    }
+}
 
 //-----------------------------------------------------------------------------
diff --git a/libraries/murmur2/src/MurmurHash2.h b/libraries/murmur2/src/MurmurHash2.h
index c7b83bca..dc2c9681 100644
--- a/libraries/murmur2/src/MurmurHash2.h
+++ b/libraries/murmur2/src/MurmurHash2.h
@@ -1,30 +1,33 @@
 //-----------------------------------------------------------------------------
-// MurmurHash2 was written by Austin Appleby, and is placed in the public
-// domain. The author hereby disclaims copyright to this source code.
+// The original MurmurHash2 was written by Austin Appleby, and is placed in the
+// public domain. The author hereby disclaims copyright to this source code.
+//
+// This was modified as to possibilitate it's usage incrementally.
+// Those modifications are also placed in the public domain, and the author of
+// such modifications hereby disclaims copyright to this source code.
 
 #pragma once
 
-//-----------------------------------------------------------------------------
-// Platform-specific functions and macros
+#include <cstdint>
+#include <fstream>
 
-// Microsoft Visual Studio
-
-#if defined(_MSC_VER) && (_MSC_VER < 1600)
-
-typedef unsigned char uint8_t;
-typedef unsigned int uint32_t;
-typedef unsigned __int64 uint64_t;
-
-// Other compilers
-
-#else	// defined(_MSC_VER)
-
-#include <stdint.h>
-
-#endif // !defined(_MSC_VER)
+#include <functional>
 
 //-----------------------------------------------------------------------------
 
-uint64_t MurmurHash2        ( const void* key, int len, uint32_t seed = 1 );
+#define KiB 1024
+#define MiB 1024*KiB
+
+uint32_t MurmurHash2(
+    std::ifstream&& file_stream,
+    std::size_t buffer_size = 4*MiB,
+    std::function<bool(char)> filter_out = [](char) { return false; });
+
+struct IncrementalHashInfo {
+    uint32_t h;
+    uint32_t len;
+};
+
+void FourBytes_MurmurHash2(const unsigned char* data, IncrementalHashInfo& prev);
 
 //-----------------------------------------------------------------------------