Store database storage to files, also loading

16 files changed, 333 insertions, 38 deletions

diff --git a/include/odhtdb/Database.hpp b/include/odhtdb/Database.hpp
index 926437a..a8833fc 100644
--- a/include/odhtdb/Database.hpp
+++ b/include/odhtdb/Database.hpp
@@ -10,6 +10,11 @@
 #include "Signature.hpp"
 #include "Permission.hpp"
 #include "DatabaseNode.hpp"
+#include "Encryption.hpp"
+#include "OwnedMemory.hpp"
+#ifdef DEBUG
+#undef DEBUG
+#endif
 #include <opendht/dhtrunner.h>
 #include <vector>
 #include <ntp/NtpClient.hpp>
@@ -117,31 +122,31 @@ namespace odhtdb
     class DatabaseCreateResponse
     {
     public:
-        DatabaseCreateResponse(LocalUser *nodeAdminUser, const std::shared_ptr<char*> &key, const std::shared_ptr<Hash> &hash);
+        DatabaseCreateResponse(LocalUser *nodeAdminUser, const std::shared_ptr<OwnedMemory> &key, const std::shared_ptr<Hash> &hash);
         
         const LocalUser* getNodeAdminUser() const;
         // Size of encryption key is odhtdb::KEY_BYTE_SIZE (found in Encryption.hpp)
-        const std::shared_ptr<char*> getNodeEncryptionKey() const;
+        const std::shared_ptr<OwnedMemory> getNodeEncryptionKey() const;
         const std::shared_ptr<Hash> getRequestHash() const;
     private:
         LocalUser *nodeAdminUser;
-        std::shared_ptr<char*> key;
+        std::shared_ptr<OwnedMemory> key;
         std::shared_ptr<Hash> hash;
     };
 
     class Database
     {
     public:
-        Database(const char *bootstrapNodeAddr, u16 port, boost::filesystem::path storageDir);
+        Database(const char *bootstrapNodeAddr, u16 port, const boost::filesystem::path &storageDir);
         ~Database();
 
-        void seed(const std::shared_ptr<Hash> hash, const std::shared_ptr<char*> encryptionKey);
+        void seed(const DatabaseNode &nodeToSeed);
         // Throws DatabaseCreateException on failure.
-        std::unique_ptr<DatabaseCreateResponse> create(const std::string &ownerName, const std::string &nodeName);
+        std::unique_ptr<DatabaseCreateResponse> create(const std::string &ownerName, const std::string &ownerPlainPassword, const std::string &nodeName);
         // Throws DatabaseAddException on failure
         void addData(const DatabaseNode &nodeInfo, LocalUser *userToPerformActionWith, DataView dataToAdd);
         // Throws PermissionDeniedException if user @userToPerformActionWith is not allowed to add user @userToAdd to group @groupToAddUserTo
-        void addUserToGroup(const DatabaseNode &nodeInfo, LocalUser *userToPerformActionWith, const std::string &userToAddName, const Signature::PublicKey &userToAddPublicKey, Group *groupToAddUserTo);
+        void addUser(const DatabaseNode &nodeInfo, LocalUser *userToPerformActionWith, const std::string &userToAddName, const Signature::PublicKey &userToAddPublicKey, Group *groupToAddUserTo);
         void commit();
 
         void setOnCreateNodeCallback(std::function<void(const DatabaseCreateNodeRequest&)> callbackFunc);
@@ -155,10 +160,10 @@ namespace odhtdb
         // Throws CommitAddException on failure
         void commitStagedAddObject(const std::unique_ptr<StagedObject> &stagedObject);
         ntp::NtpTimestamp getSyncedTimestampUtc() const;
-        void deserializeCreateRequest(const std::shared_ptr<dht::Value> &value, const Hash &hash, const std::shared_ptr<char*> encryptionKey);
-        void deserializeAddRequest(const std::shared_ptr<dht::Value> &value, const Hash &requestDataHash, const std::shared_ptr<char*> encryptionKey);
-        bool listenCreateData(std::shared_ptr<dht::Value> value, const Hash &hash, const std::shared_ptr<char*> encryptionKey);
-        bool listenAddData(std::shared_ptr<dht::Value> value, const Hash &requestDataHash, const std::shared_ptr<char*> encryptionKey);
+        void deserializeCreateRequest(const std::shared_ptr<dht::Value> &value, const Hash &hash, const std::shared_ptr<OwnedMemory> encryptionKey);
+        void deserializeAddRequest(const std::shared_ptr<dht::Value> &value, const Hash &requestDataHash, const std::shared_ptr<Hash> &nodeHash, const std::shared_ptr<OwnedMemory> encryptionKey);
+        bool listenCreateData(std::shared_ptr<dht::Value> value, const Hash &hash, const std::shared_ptr<OwnedMemory> encryptionKey);
+        bool listenAddData(std::shared_ptr<dht::Value> value, const Hash &requestDataHash, const std::shared_ptr<Hash> nodeHash, const std::shared_ptr<OwnedMemory> encryptionKey);
     private:
         dht::DhtRunner node;
         std::vector<std::unique_ptr<StagedObject>> stagedCreateObjects;
diff --git a/include/odhtdb/DatabaseNode.hpp b/include/odhtdb/DatabaseNode.hpp
index 3ca4be3..620cd40 100644
--- a/include/odhtdb/DatabaseNode.hpp
+++ b/include/odhtdb/DatabaseNode.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include "Hash.hpp"
+#include "OwnedMemory.hpp"
 #include <memory>
 
 namespace odhtdb
@@ -8,14 +9,16 @@ namespace odhtdb
     class DatabaseNode
     {
     public:
-        DatabaseNode(const std::shared_ptr<char*> &_encryptionKey, const std::shared_ptr<Hash> &_nodeHash) : 
+        DatabaseNode() {}
+        
+        DatabaseNode(const std::shared_ptr<OwnedMemory> &_encryptionKey, const std::shared_ptr<Hash> &_nodeHash) : 
             encryptionKey(_encryptionKey),
             nodeHash(_nodeHash)
         {
             
         }
         
-        const std::shared_ptr<char*> getNodeEncryptionKey() const
+        const std::shared_ptr<OwnedMemory> getNodeEncryptionKey() const
         {
             return encryptionKey;
         }
@@ -25,7 +28,7 @@ namespace odhtdb
             return nodeHash;
         }
     private:
-        std::shared_ptr<char*> encryptionKey;
+        std::shared_ptr<OwnedMemory> encryptionKey;
         std::shared_ptr<Hash> nodeHash;
     };
 }
diff --git a/include/odhtdb/DatabaseStorage.hpp b/include/odhtdb/DatabaseStorage.hpp
index ad4f70b..a2789f7 100644
--- a/include/odhtdb/DatabaseStorage.hpp
+++ b/include/odhtdb/DatabaseStorage.hpp
@@ -5,12 +5,14 @@
 #include "DataView.hpp"
 #include "Signature.hpp"
 #include "Encryption.hpp"
+#include "Group.hpp"
 #include <vector>
 #include <stdexcept>
+#include <boost/filesystem/path.hpp>
+#include <sibs/SafeDeserializer.hpp>
 
 namespace odhtdb
 {
-    class Group;
     class User;
     
     struct DatabaseStorageObject
@@ -52,12 +54,30 @@ namespace odhtdb
         DatabaseStorageNotFound(const std::string &errMsg) : std::runtime_error(errMsg) {}
     };
     
+    class DatabaseStorageCorrupt : public std::runtime_error
+    {
+    public:
+        DatabaseStorageCorrupt(const std::string &errMsg) : std::runtime_error(errMsg) {}
+    };
+    
     using DatabaseStorageMap = MapHash<DatabaseStorageObjectList*>;
     using DatabaseStorageQuarantineMap = Signature::MapPublicKey<std::vector<DatabaseStorageQuarantineObject*>>;
     
+    const int PASSWORD_SALT_LEN = 16;
+    const int HASHED_PASSWORD_LEN = 32;
+    
     class DatabaseStorage
     {
     public:
+        struct UserData
+        {
+            User *user;
+            u8 hashedPassword[HASHED_PASSWORD_LEN]; // All bytes are zero if user is not local
+        };
+        
+        // Throws DatabaseStorageCorrupt if storage is corrupted
+        DatabaseStorage(const boost::filesystem::path &storagePath);
+        
         // Throws DatabaseStorageAlreadyExists if data with hash already exists
         void createStorage(const Hash &hash, Group *creatorGroup, u64 timestamp, const u8 *data, usize dataSize);
         
@@ -68,28 +88,43 @@ namespace odhtdb
         // Throws DatabaseStorageAlreadyExists if same data has been added before (hash of @data, in @dataHash)
         void addToQuarantine(const Hash &dataHash, const Signature::PublicKey &creatorPublicKey, u64 timestamp, const u8 *data, usize dataSize);
         
-        void addUser(User *user, const Hash &hash);
+        // Return false if group with id already exists, otherwise return true
+        bool addGroup(const Hash &nodeHash, Group *group);
+        
+        // Return false if user public key already exists, otherwise return true
+        bool addUser(const Hash &nodeHash, User *user);
         
         // Returns nullptr if no storage with provided hash exists
         const DatabaseStorageObjectList* getStorage(const Hash &hash) const;
         
-        // Returns nullptr if no node with the user exists
-        const Hash* getNodeByUserPublicKey(const Signature::PublicKey &userPublicKey) const;
+        // Returns nullptr if a group with id @groupId doesn't exist in node @nodeHash or if no node with id @nodeHash exists
+        Group* getGroupById(const Hash &nodeHash, uint8_t groupId[GROUP_ID_LENGTH]);
         
-        // Returns nullptr if no user with public key exists
-        const User* getUserByPublicKey(const Signature::PublicKey &userPublicKey) const;
+        // Returns nullptr if a user with public key @publicKey doesn't exist in node @nodeHash or if no node with id @nodeHash exists
+        User* getUserByPublicKey(const Hash &nodeHash, Signature::PublicKey &userPublicKey);
         
-        // Returns nullptr if a group with id @groupId doesn't exist
-        Group* getGroupById(uint8_t groupId[16]);
+        // Return users in node, or nullptr if no node with id @nodeHash exists
+        const Signature::MapPublicKey<UserData*>* getUsersData(const Hash &nodeHash) const;
         
         // Update storage state (remove quarantine objects if they are too old, etc)
         void update();
     private:
+        void loadGroupsFromFile();
+        void loadUsersFromFile();
+        void loadDataFromFile();
+        void loadMetadataFromFile();
+        void loadStorageCreate(sibs::SafeDeserializer &deserializer);
+        void loadStorageAppend(sibs::SafeDeserializer &deserializer);
+    private:
         DatabaseStorageMap storageMap;
         DatabaseStorageQuarantineMap quarantineStorageMap;
         SetHash storedDataHash; // Prevent duplicate data from being added
-        Signature::MapPublicKey<Hash*> userPublicKeyNodeMap;
-        Signature::MapPublicKey<const User*> publicKeyUserMap;
-        DataViewMap<Group*> groupByIdMap;
+        MapHash<Signature::MapPublicKey<UserData*>*> nodePublicKeyUserDataMap;
+        MapHash<DataViewMap<Group*>*> nodeGroupByIdMap;
+        boost::filesystem::path groupsFilePath;
+        boost::filesystem::path usersFilePath;
+        boost::filesystem::path dataFilePath;
+        boost::filesystem::path metadataFilePath;
+        u8 passwordSalt[PASSWORD_SALT_LEN];
     };
 }
diff --git a/include/odhtdb/Encryption.hpp b/include/odhtdb/Encryption.hpp
index 4697b35..5271cbd 100644
--- a/include/odhtdb/Encryption.hpp
+++ b/include/odhtdb/Encryption.hpp
@@ -11,8 +11,8 @@
 
 namespace odhtdb
 {
-    const int NONCE_BYTE_SIZE = 24;
-    const int KEY_BYTE_SIZE = 32;
+    const int ENCRYPTION_NONCE_BYTE_SIZE = 24;
+    const int ENCRYPTION_KEY_BYTE_SIZE = 32;
     
     class EncryptionException : public std::runtime_error
     {
@@ -38,8 +38,8 @@ namespace odhtdb
         DataView getNonce() const;
         DataView getCipherText() const;
     private:
-        unsigned char key[KEY_BYTE_SIZE];
-        unsigned char nonce[NONCE_BYTE_SIZE];
+        unsigned char key[ENCRYPTION_KEY_BYTE_SIZE];
+        unsigned char nonce[ENCRYPTION_NONCE_BYTE_SIZE];
         unsigned char *cipherText;
         unsigned long long cipherTextLength;
     };
diff --git a/include/odhtdb/FileUtils.hpp b/include/odhtdb/FileUtils.hpp
new file mode 100644
index 0000000..7bfbe3e
--- /dev/null
+++ b/include/odhtdb/FileUtils.hpp
@@ -0,0 +1,22 @@
+#pragma once
+
+#include <boost/filesystem/path.hpp>
+#include <stdexcept>
+#include "OwnedMemory.hpp"
+#include "DataView.hpp"
+
+namespace odhtdb
+{
+    class FileException : public std::runtime_error
+    {
+    public:
+        FileException(const std::string &errMsg) : std::runtime_error(errMsg) {}
+    };
+    
+    // Throws FileException on error
+    OwnedMemory fileGetContent(const boost::filesystem::path &filepath);
+    
+    // Creates file if it doesn't exist.
+    // Throws FileException on error
+    void fileAppend(const boost::filesystem::path &filepath, const DataView &data);
+}
diff --git a/include/odhtdb/Group.hpp b/include/odhtdb/Group.hpp
index 315961d..890b2fc 100644
--- a/include/odhtdb/Group.hpp
+++ b/include/odhtdb/Group.hpp
@@ -21,13 +21,13 @@ namespace odhtdb
         }
     };
     
-    
+    const int GROUP_ID_LENGTH = 16;
 
     class Group
     {
         friend class User;
     public:
-        Group(const std::string &name, uint8_t id[16], const Permission &permission);
+        Group(const std::string &name, uint8_t id[GROUP_ID_LENGTH], const Permission &permission);
         ~Group();
 
         const std::string& getName() const;
@@ -38,7 +38,7 @@ namespace odhtdb
         void addUser(const User *user);
     private:
         std::string name;
-        uint8_t id[16];
+        uint8_t id[GROUP_ID_LENGTH];
         Permission permission;
         std::vector<const User*> users;
     };
diff --git a/include/odhtdb/LocalUser.hpp b/include/odhtdb/LocalUser.hpp
index d60cb38..0312a38 100644
--- a/include/odhtdb/LocalUser.hpp
+++ b/include/odhtdb/LocalUser.hpp
@@ -1,15 +1,16 @@
 #pragma once
 
 #include "User.hpp"
+#include "types.hpp"
 
 namespace odhtdb
 {
     class LocalUser : public User
     {
     public:
-        static LocalUser* create(const Signature::KeyPair &keyPair, const std::string &name, Group *group)
+        static LocalUser* create(const Signature::KeyPair &keyPair, const std::string &name, Group *group, const std::string &plainPassword)
         {
-            return new LocalUser(keyPair, name, group);
+            return new LocalUser(keyPair, name, group, plainPassword);
         }
         
         const Signature::PublicKey& getPublicKey() const override
@@ -21,9 +22,15 @@ namespace odhtdb
         {
             return keyPair.getPrivateKey();
         }
+        
+        const std::string& getPlainPassword() const
+        {
+            return plainPassword;
+        }
     private:
-        LocalUser(const Signature::KeyPair &_keyPair, const std::string &name, Group *group) : User(name, group), keyPair(_keyPair) {}
+        LocalUser(const Signature::KeyPair &_keyPair, const std::string &name, Group *group, const std::string &plainPassword);
     private:
         Signature::KeyPair keyPair;
+        std::string plainPassword;
     };
 }
diff --git a/include/odhtdb/LocalUserEncrypted.hpp b/include/odhtdb/LocalUserEncrypted.hpp
new file mode 100644
index 0000000..c250d13
--- /dev/null
+++ b/include/odhtdb/LocalUserEncrypted.hpp
@@ -0,0 +1,51 @@
+#pragma once
+
+#include "User.hpp"
+#include "types.hpp"
+#include "Encryption.hpp"
+
+namespace odhtdb
+{
+    struct EncryptedPrivateKey
+    {
+        u8 nonce[ENCRYPTION_NONCE_BYTE_SIZE];
+        u8 encryptedPrivateKey[16 + PRIVATE_KEY_NUM_BYTES];
+        
+        EncryptedPrivateKey();
+        EncryptedPrivateKey(const EncryptedPrivateKey &other);
+        
+        // Throws DecryptionException if password (or salt) is wrong
+        Signature::PrivateKey decrypt(const DataView &plainPassword, const DataView &salt) const;
+    };
+    
+    // Local user with encrypted private key
+    class LocalUserEncrypted : public User
+    {
+    public:
+        static LocalUserEncrypted* create(const Signature::PublicKey &publicKey, const EncryptedPrivateKey &encryptedPrivateKey, const std::string &name, Group *group)
+        {
+            return new LocalUserEncrypted(publicKey, encryptedPrivateKey, name, group);
+        }
+        
+        const Signature::PublicKey& getPublicKey() const override
+        {
+            return publicKey;
+        }
+        
+        const EncryptedPrivateKey& getPrivateKey() const
+        {
+            return encryptedPrivateKey;
+        }
+    private:
+        LocalUserEncrypted(const Signature::PublicKey &_publicKey, const EncryptedPrivateKey &_encryptedPrivateKey, const std::string &name, Group *group) : 
+            User(User::Type::LOCAL_ENCRYPTED, name, group),
+            publicKey(_publicKey),
+            encryptedPrivateKey(_encryptedPrivateKey)
+        {
+            
+        }
+    private:
+        Signature::PublicKey publicKey;
+        EncryptedPrivateKey encryptedPrivateKey;
+    };
+}
diff --git a/include/odhtdb/OwnedMemory.hpp b/include/odhtdb/OwnedMemory.hpp
new file mode 100644
index 0000000..5dcdf25
--- /dev/null
+++ b/include/odhtdb/OwnedMemory.hpp
@@ -0,0 +1,22 @@
+#pragma once
+
+#include "types.hpp"
+
+namespace odhtdb
+{
+    class OwnedMemory
+    {
+    public:
+        OwnedMemory() : data(nullptr), size(0) {}
+        OwnedMemory(void *_data, usize _size) : data(_data), size(_size) {}
+        OwnedMemory(OwnedMemory &&other);
+        ~OwnedMemory();
+        
+        // Do not allow copy of this struct, forcing move when returning a OwnedMemory in a function
+        OwnedMemory(OwnedMemory&) = delete;
+        OwnedMemory& operator = (OwnedMemory&) = delete;
+        
+        void *data;
+        usize size;
+    };
+}
diff --git a/include/odhtdb/PasswordHash.hpp b/include/odhtdb/PasswordHash.hpp
new file mode 100644
index 0000000..08b1857
--- /dev/null
+++ b/include/odhtdb/PasswordHash.hpp
@@ -0,0 +1,9 @@
+#pragma once
+
+#include "OwnedMemory.hpp"
+#include "DataView.hpp"
+
+namespace odhtdb
+{
+    OwnedMemory hashPassword(const DataView &plainPassword, const DataView &salt);
+}
diff --git a/include/odhtdb/Permission.hpp b/include/odhtdb/Permission.hpp
index 1ae2642..1e7bb0c 100644
--- a/include/odhtdb/Permission.hpp
+++ b/include/odhtdb/Permission.hpp
@@ -31,6 +31,9 @@ namespace odhtdb
     {
     public:
         // @permissionLevel is hierarchical access right. A group can only modify a group that has higher @permissionLevel value
+        Permission(u8 permissionLevel, u32 permissionFlags);
+        
+        // @permissionLevel is hierarchical access right. A group can only modify a group that has higher @permissionLevel value
         Permission(u8 permissionLevel, std::initializer_list<PermissionType> permissions);
         
         u8 getPermissionLevel() const { return permissionLevel; }
diff --git a/include/odhtdb/RemoteUser.hpp b/include/odhtdb/RemoteUser.hpp
index 181a4c4..9dc8f96 100644
--- a/include/odhtdb/RemoteUser.hpp
+++ b/include/odhtdb/RemoteUser.hpp
@@ -17,7 +17,7 @@ namespace odhtdb
             return publicKey;
         }
     private:
-        RemoteUser(const Signature::PublicKey &_publicKey, const std::string &name, Group *group) : User(name, group), publicKey(_publicKey){}
+        RemoteUser(const Signature::PublicKey &_publicKey, const std::string &name, Group *group) : User(User::Type::REMOTE, name, group), publicKey(_publicKey){}
     private:
         Signature::PublicKey publicKey;
     };
diff --git a/include/odhtdb/Signature.hpp b/include/odhtdb/Signature.hpp
index 62c41c3..db434ac 100644
--- a/include/odhtdb/Signature.hpp
+++ b/include/odhtdb/Signature.hpp
@@ -93,6 +93,8 @@ namespace odhtdb
         {
             friend class KeyPair;
         public:
+            static PrivateKey ZERO;
+            
             // Throws InvalidSignatureKeySize if size is not PRIVATE_KEY_NUM_BYTES
             PrivateKey(const char *data, size_t size);
             PrivateKey(const PrivateKey &other);
@@ -113,9 +115,12 @@ namespace odhtdb
         class KeyPair
         {
         public:
-            // Throws SignatureGenerationException if generation of private/public key pair fails (should never happen)
+            // Generate a new key pair, Throws SignatureGenerationException if generation of private/public key pair fails (should never happen)
             KeyPair();
             
+            // Create a key pair from existing public and private key
+            KeyPair(const PublicKey &publicKey, const PrivateKey &privateKey);
+            
             const PublicKey& getPublicKey() const { return publicKey; }
             const PrivateKey& getPrivateKey() const { return privateKey; }
         private:
diff --git a/include/odhtdb/User.hpp b/include/odhtdb/User.hpp
index fb37876..d6e551a 100644
--- a/include/odhtdb/User.hpp
+++ b/include/odhtdb/User.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include "Signature.hpp"
+#include "types.hpp"
 #include <string>
 #include <stdexcept>
 #include <vector>
@@ -22,16 +23,25 @@ namespace odhtdb
     class User
     {
     public:
+        enum class Type : u8
+        {
+            LOCAL,
+            LOCAL_ENCRYPTED,
+            REMOTE
+        };
+        
         virtual ~User(){}
         
         void addToGroup(Group *group);
         
+        Type getType() const { return type; }
         const std::string& getName() const { return name; }
         const std::vector<Group*>& getGroups() const { return groups; }
         virtual const Signature::PublicKey& getPublicKey() const = 0;
     protected:
-        User(const std::string &name, Group *group);
+        User(Type type, const std::string &name, Group *group);
     private:
+        Type type;
         std::string name;
         std::vector<Group*> groups;
     };
diff --git a/include/odhtdb/env.hpp b/include/odhtdb/env.hpp
new file mode 100644
index 0000000..bafc750
--- /dev/null
+++ b/include/odhtdb/env.hpp
@@ -0,0 +1,63 @@
+#pragma once
+
+#define OS_FAMILY_WINDOWS 0
+#define OS_FAMILY_POSIX 1
+
+#define OS_TYPE_WINDOWS 0
+#define OS_TYPE_LINUX 1
+
+#if defined(_WIN32) || defined(_WIN64)
+    #if defined(_WIN64)
+        #define SYS_ENV_64BIT
+    #else
+        #define SYS_ENV_32BIT
+    #endif
+    #define OS_FAMILY OS_FAMILY_WINDOWS
+    #define OS_TYPE OS_TYPE_WINDOWS
+
+	#ifndef UNICODE
+	#define UNICODE
+	#endif
+
+	#ifndef _UNICODE
+	#define _UNICODE
+	#endif
+
+	#ifndef WIN32_LEAN_AND_MEAN
+	#define WIN32_LEAN_AND_MEAN
+	#endif
+
+	#include <Windows.h>
+#endif
+
+#if defined(__linux__) || defined(__unix__) || defined(__APPLE__) || defined(_POSIX_VERSION)
+    #define OS_FAMILY OS_FAMILY_POSIX
+#endif
+
+#ifdef __linux__
+    #define OS_TYPE OS_TYPE_LINUX
+#endif
+
+#if defined(__GNUC__)
+    #if defined(__x86_64__) || defined(__pc64__)
+        #define SYS_ENV_64BIT
+    #else
+        #define SYS_ENV_32BIT
+    #endif
+#endif
+
+#if !defined(SYS_ENV_32BIT) && !defined(SYS_ENV_64BIT)
+    #error "System is not detected as either 32-bit or 64-bit"
+#endif
+
+#if !defined(OS_FAMILY)
+    #error "System not supported. Only Windows and Posix systems supported right now"
+#endif
+
+#if !defined(OS_TYPE)
+    #error "System not supported. Only Windows and linux systems supported right now"
+#endif
+
+#if !defined(DEBUG) && !defined(NDEBUG)
+#define DEBUG
+#endif
diff --git a/include/odhtdb/hex2bin.hpp b/include/odhtdb/hex2bin.hpp
new file mode 100644
index 0000000..96a2229
--- /dev/null
+++ b/include/odhtdb/hex2bin.hpp
@@ -0,0 +1,60 @@
+#pragma once
+
+#include <string>
+#include <stdexcept>
+
+namespace odhtdb
+{
+    class InvalidHexStringFormat : public std::runtime_error
+    {
+    public:
+        InvalidHexStringFormat(const std::string &errMsg) : std::runtime_error(errMsg) {}
+    };
+    
+    // Returns -1 if c is not a hex string (0-9a-fA-F)
+    static int __hexchar_to_num(int c)
+    {
+        if(c >= '0' && c <= '9')
+            return c - '0';
+        else if(c >= 'a' && c <= 'f')
+            return 10 + (c - 'a');
+        else if(c >= 'A' && c <= 'F')
+            return 10 + (c - 'A');
+        else
+            return -1;
+    }
+    
+    // Throws InvalidHexStringFormat on invalid input
+    static std::string hex2bin(const char *data, size_t dataSize)
+    {
+        if(dataSize % 2 != 0)
+            throw InvalidHexStringFormat("Input string size is not of an even size");
+        
+        std::string result;
+        result.resize(dataSize / 2);
+        
+        for(int i = 0; i < dataSize; i += 2)
+        {
+            int v = __hexchar_to_num(data[i]);
+            int v2 = __hexchar_to_num(data[i + 1]);
+            
+            if(v == -1)
+            {
+                std::string errMsg = "Invalid hex character: ";
+                errMsg += data[i];
+                throw InvalidHexStringFormat(errMsg);
+            }
+            
+            if(v2 == -1)
+            {
+                std::string errMsg = "Invalid hex character: ";
+                errMsg += data[i + 1];
+                throw InvalidHexStringFormat(errMsg);
+            }
+            
+            result[i / 2] = (v << 4) | v2;
+        }
+        
+        return result;
+    }
+}