Added OpenSSL lazy load

Implements #27

TODO.md

@@ -3,6 +3,7 @@
   "Digital Signature Appearances" document specification
 
 ### 1.0
+- Remove PdfEncryptMD5Base::GetMD5Binary and PdfEncryptMD5Base::GetMD5String and use common functions
 - PdfFontManager: Add font hash to cache descriptor
 - PdfField: Evaluate make a virtual getValueObject()
 - Evaluate removing PdfObject::Null and PdfVariant::Null and introduce nullptr_t constructor overloads

src/podofo/auxiliary/basetypes.h

@@ -46,6 +46,8 @@ namespace PoDoFo
         }
         charbuff_t(std::string&& str)
             : std::string(std::move(str)) { }
+        charbuff_t(const char* str, size_t size)
+            : std::string(str, size) { }
         explicit charbuff_t(const bufferview& view)
             : std::string(view.data(), view.size()) { }
         explicit charbuff_t(const std::string_view& view)

src/podofo/main/PdfCommon.cpp

@@ -5,6 +5,7 @@
  */
 
 #include <podofo/private/PdfDeclarationsPrivate.h>
+#include "podofo/private/OpenSSLInternal.h"
 #include "PdfCommon.h"
 #include "PdfFontManager.h"
 
@@ -19,6 +20,20 @@ PODOFO_EXPORT PdfLogSeverity s_MaxLogSeverity = PdfLogSeverity::Information;
 
 PODOFO_EXPORT LogMessageCallback s_LogMessageCallback;
 
+PODOFO_EXPORT ssl::OpenSSLMain s_SSL;
+
+void ssl::Init()
+{
+    // Initialize the OpenSSL singleton
+    static struct InitOpenSSL
+    {
+        InitOpenSSL()
+        {
+            s_SSL.Init();
+        }
+    } s_init;
+}
+
 void PdfCommon::AddFontDirectory(const string_view& path)
 {
     PdfFontManager::AddFontDirectory(path);

src/podofo/main/PdfDeclarations.h

@@ -771,6 +771,27 @@ enum class PdfBlendMode
     Luminosity,
 };
 
+enum class PdfSignatureType
+{
+    Unknown = 0,
+    PAdES_B = 1,
+    Pkcs7 = 2,
+};
+
+enum class PdfEncryptionAlgorithm
+{
+    Unknown = 0,
+    RSA,
+};
+
+enum class PdfHashingAlgorithm
+{
+    Unknown = 0,
+    SHA256,
+    SHA384,
+    SHA512,
+};
+
 };
 
 ENABLE_BITMASK_OPERATORS(PoDoFo::PdfSaveOptions);

src/podofo/main/PdfSignerCms.h

@@ -9,7 +9,6 @@
 
 #include <chrono>
 #include "PdfSigner.h"
-#include "PdfSigningCommon.h"
 
 extern "C"
 {
@@ -34,6 +33,8 @@ namespace PoDoFo
         nullable<std::chrono::seconds> SigningTimeUTC;
     };
 
+    using PdfSigningService = std::function<void(bufferview, bool, charbuff&)>;
+
     /** This class computes a CMS signature according to RFC 5652
      */
     class PODOFO_API PdfSignerCms : public PdfSigner

src/podofo/private/CmsContext.h

@@ -9,7 +9,7 @@
 
 #include <chrono>
 
-#include <podofo/main/PdfSigningCommon.h>
+#include <podofo/main/PdfDeclarations.h>
 
 extern "C"
 {