diff --git a/.github/workflows/cmake.yml b/.github/workflows/cmake.yml
index 72339ba..32c3c17 100644
--- a/.github/workflows/cmake.yml
+++ b/.github/workflows/cmake.yml
@@ -55,11 +55,10 @@ jobs:
           ${{matrix.platform.msys-env}}-zlib
 
     - name: Configure CMake
-      run: cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=${{matrix.build-type}} -DBUILD_STATIC=${{matrix.build-static}}
+      run: cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=${{matrix.build-type}} -DBUILD_STATIC=${{matrix.build-static}} -DBUILD_TESTING=ON
 
     - name: Build
       run: cmake --build build
 
     - name: Test
-      working-directory: build
-      run: ctest --output-on-failure
+      run: ctest --test-dir build --output-on-failure
diff --git a/CMakeLists.txt b/CMakeLists.txt
index d03744d..0f90e1a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -55,6 +55,7 @@ endif()
 message(STATUS "OPENSSL_FOUND: ${OPENSSL_FOUND}")
 message(STATUS "USE_OUR_OWN_MD5: ${USE_OUR_OWN_MD5}")
 message(STATUS "BUILD_STATIC: ${BUILD_STATIC}")
+message(STATUS "BUILD_TESTING: ${BUILD_TESTING}")
 
 add_definitions(-DHAVE_CONFIG_H)
 configure_file(${CMAKE_CURRENT_SOURCE_DIR}/lib/unshield_config.h.in ${CMAKE_CURRENT_BINARY_DIR}/lib/unshield_config.h)
@@ -84,4 +85,6 @@ add_subdirectory(src)
 install(FILES man/unshield.1 DESTINATION ${CMAKE_INSTALL_MANDIR}/man1)
 install(FILES ${CMAKE_CURRENT_BINARY_DIR}/libunshield.pc DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig)
 
-add_subdirectory(test)
+if (BUILD_TESTING)
+    add_subdirectory(test)
+endif ()
diff --git a/lib/file.c b/lib/file.c
index c385b9f..daf2a32 100644
--- a/lib/file.c
+++ b/lib/file.c
@@ -314,8 +314,8 @@ static bool unshield_reader_open_volume(UnshieldReader* reader, int volume)/*{{{
 #if VERBOSE >= 2
   unshield_trace("Open volume %i", volume);
 #endif
-  
-  FCLOSE(reader->volume_file);
+
+  FCLOSE(reader->unshield, reader->volume_file);
 
   reader->volume_file = unshield_fopen_for_reading(reader->unshield, volume, CABINET_SUFFIX);
   if (!reader->volume_file)
@@ -328,8 +328,7 @@ static bool unshield_reader_open_volume(UnshieldReader* reader, int volume)/*{{{
     uint8_t tmp[COMMON_HEADER_SIZE];
     uint8_t* p = tmp;
 
-    if (COMMON_HEADER_SIZE != 
-        fread(&tmp, 1, COMMON_HEADER_SIZE, reader->volume_file))
+    if (COMMON_HEADER_SIZE != unshield_fread(reader->unshield, &tmp, 1, COMMON_HEADER_SIZE, reader->volume_file))
       goto exit;
 
     if (!unshield_read_common_header(&p, &common_header))
@@ -346,8 +345,8 @@ static bool unshield_reader_open_volume(UnshieldReader* reader, int volume)/*{{{
         uint8_t five_header[VOLUME_HEADER_SIZE_V5];
         uint8_t* p = five_header;
 
-        if (VOLUME_HEADER_SIZE_V5 != 
-            fread(&five_header, 1, VOLUME_HEADER_SIZE_V5, reader->volume_file))
+        if (VOLUME_HEADER_SIZE_V5 !=
+            unshield_fread(reader->unshield, &five_header, 1, VOLUME_HEADER_SIZE_V5, reader->volume_file))
           goto exit;
 
         reader->volume_header.data_offset                = READ_UINT32(p); p += 4;
@@ -383,8 +382,8 @@ static bool unshield_reader_open_volume(UnshieldReader* reader, int volume)/*{{{
         uint8_t six_header[VOLUME_HEADER_SIZE_V6];
         uint8_t* p = six_header;
 
-        if (VOLUME_HEADER_SIZE_V6 != 
-            fread(&six_header, 1, VOLUME_HEADER_SIZE_V6, reader->volume_file))
+        if (VOLUME_HEADER_SIZE_V6 !=
+            unshield_fread(reader->unshield, &six_header, 1, VOLUME_HEADER_SIZE_V6, reader->volume_file))
           goto exit;
 
         reader->volume_header.data_offset                       = READ_UINT32(p); p += 4;
@@ -486,7 +485,7 @@ static bool unshield_reader_open_volume(UnshieldReader* reader, int volume)/*{{{
   else
     reader->volume_bytes_left = volume_bytes_left_expanded;
 
-  fseek(reader->volume_file, data_offset, SEEK_SET);
+  unshield_fseek(reader->unshield, reader->volume_file, data_offset, SEEK_SET);
 
   reader->volume = volume;
   success = true;
@@ -532,7 +531,7 @@ static bool unshield_reader_read(UnshieldReader* reader, void* buffer, size_t si
 
 #if VERBOSE >= 3
     unshield_trace("Trying to read 0x%x bytes from offset %08x in volume %i", 
-        bytes_to_read, ftell(reader->volume_file), reader->volume);
+        bytes_to_read, unshield_ftell(reader->unshield, reader->volume_file), reader->volume);
 #endif
     if (bytes_to_read == 0)
     {
@@ -540,12 +539,12 @@ static bool unshield_reader_read(UnshieldReader* reader, void* buffer, size_t si
       goto exit;
     }
 
-    if (bytes_to_read != fread(p, 1, bytes_to_read, reader->volume_file))
+    if (bytes_to_read != unshield_fread(reader->unshield, p, 1, bytes_to_read, reader->volume_file))
     {
       unshield_error("Failed to read 0x%08x bytes of file %i (%s) from volume %i. Current offset = 0x%08x",
           bytes_to_read, reader->index, 
           unshield_file_name(reader->unshield, reader->index), reader->volume,
-          ftell(reader->volume_file));
+          unshield_ftell(reader->unshield, reader->volume_file));
       goto exit;
     }
 
@@ -583,14 +582,14 @@ static bool unshield_reader_read(UnshieldReader* reader, void* buffer, size_t si
   return success;
 }/*}}}*/
 
-int copy_file(FILE* infile, FILE* outfile) {
+int copy_file(Unshield* unshield, FILE* infile, FILE* outfile) {
 #define SIZE (1024*1024)
 
     char buffer[SIZE];
     size_t bytes;
 
-    while (0 < (bytes = fread(buffer, 1, sizeof(buffer), infile)))
-        fwrite(buffer, 1, bytes, outfile);
+    while (0 < (bytes = unshield_fread(unshield, buffer, 1, sizeof(buffer), infile)))
+        unshield_fwrite(unshield, buffer, 1, bytes, outfile);
 
     return 0;
 }
@@ -626,7 +625,7 @@ static UnshieldReader* unshield_reader_create_external(/*{{{*/
     }
 
     if (file_descriptor->flags & FILE_COMPRESSED) {
-        long file_size = FSIZE(reader->volume_file);
+        long file_size = FSIZE(unshield, reader->volume_file);
         FILE *temporary_file = NULL;
 
         /*
@@ -639,7 +638,7 @@ static UnshieldReader* unshield_reader_create_external(/*{{{*/
         if (diff > 0) {
             diff = MIN(sizeof(END_OF_CHUNK), diff);
             temporary_file = tmpfile();
-            copy_file(reader->volume_file, temporary_file);
+            copy_file(reader->unshield, reader->volume_file, temporary_file);
             fwrite(END_OF_CHUNK + sizeof(END_OF_CHUNK) - diff, 1, diff, temporary_file);
             fseek(temporary_file, 0, SEEK_SET);
 
@@ -719,7 +718,7 @@ static void unshield_reader_destroy(UnshieldReader* reader)/*{{{*/
 {
   if (reader)
   {
-    FCLOSE(reader->volume_file);
+    FCLOSE(reader->unshield, reader->volume_file);
     free(reader);
   }
 }/*}}}*/
@@ -777,7 +776,7 @@ bool unshield_file_save (Unshield* unshield, int index, const char* filename)/*{
     goto exit;
   }
 
-  if (unshield_fsize(reader->volume_file) == (long)file_descriptor->data_offset)
+  if (unshield_fsize(unshield, reader->volume_file) == (long)file_descriptor->data_offset)
   {
     unshield_error("File %i is not inside the cabinet.", index);
     goto exit;
@@ -785,7 +784,7 @@ bool unshield_file_save (Unshield* unshield, int index, const char* filename)/*{
 
   if (filename) 
   {
-    output = fopen(filename, "wb");
+    output = unshield_fopen(unshield, filename, "wb");
     if (!output)
     {
       unshield_error("Failed to open output file '%s'", filename);
@@ -883,7 +882,7 @@ bool unshield_file_save (Unshield* unshield, int index, const char* filename)/*{
 
     if (output)
     {
-      if (bytes_to_write != fwrite(output_buffer, 1, bytes_to_write, output))
+      if (bytes_to_write != unshield_fwrite(unshield, output_buffer, 1, bytes_to_write, output))
       {
         unshield_error("Failed to write %i bytes to file '%s'", bytes_to_write, filename);
         goto exit;
@@ -925,7 +924,7 @@ bool unshield_file_save (Unshield* unshield, int index, const char* filename)/*{
   md5 = NULL;
 #endif
   unshield_reader_destroy(reader);
-  FCLOSE(output);
+  FCLOSE(unshield, output);
   FREE(input_buffer);
   FREE(output_buffer);
   return success;
@@ -992,7 +991,7 @@ bool unshield_file_save_raw(Unshield* unshield, int index, const char* filename)
     goto exit;
   }
 
-  if (unshield_fsize(reader->volume_file) == (long)file_descriptor->data_offset)
+  if (unshield_fsize(unshield, reader->volume_file) == (long)file_descriptor->data_offset)
   {
     unshield_error("File %i is not inside the cabinet.", index);
     goto exit;
@@ -1000,7 +999,7 @@ bool unshield_file_save_raw(Unshield* unshield, int index, const char* filename)
 
   if (filename) 
   {
-    output = fopen(filename, "wb");
+    output = unshield_fopen(unshield, filename, "wb");
     if (!output)
     {
       unshield_error("Failed to open output file '%s'", filename);
@@ -1031,7 +1030,7 @@ bool unshield_file_save_raw(Unshield* unshield, int index, const char* filename)
     bytes_left -= bytes_to_write;
 
       if (output) {
-          if (bytes_to_write != fwrite(output_buffer, 1, bytes_to_write, output)) {
+          if (bytes_to_write != unshield_fwrite(unshield, output_buffer, 1, bytes_to_write, output)) {
               unshield_error("Failed to write %i bytes to file '%s'", bytes_to_write, filename);
               goto exit;
           }
@@ -1042,7 +1041,7 @@ bool unshield_file_save_raw(Unshield* unshield, int index, const char* filename)
   
 exit:
   unshield_reader_destroy(reader);
-  FCLOSE(output);
+  FCLOSE(unshield, output);
   FREE(input_buffer);
   FREE(output_buffer);
   return success;
@@ -1110,7 +1109,7 @@ bool unshield_file_save_old(Unshield* unshield, int index, const char* filename)
     goto exit;
   }
 
-  if (unshield_fsize(reader->volume_file) == (long)file_descriptor->data_offset)
+  if (unshield_fsize(unshield, reader->volume_file) == (long)file_descriptor->data_offset)
   {
       unshield_error("File %i is not inside the cabinet. Trying external file!", index);
       unshield_reader_destroy(reader);
@@ -1124,7 +1123,7 @@ bool unshield_file_save_old(Unshield* unshield, int index, const char* filename)
 
   if (filename) 
   {
-    output = fopen(filename, "wb");
+    output = unshield_fopen(unshield, filename, "wb");
     if (!output)
     {
       unshield_error("Failed to open output file '%s'", filename);
@@ -1247,7 +1246,7 @@ bool unshield_file_save_old(Unshield* unshield, int index, const char* filename)
           bytes_left -= bytes_to_write;
 
           if (output) {
-              if (bytes_to_write != fwrite(output_buffer, 1, bytes_to_write, output)) {
+              if (bytes_to_write != unshield_fwrite(unshield, output_buffer, 1, bytes_to_write, output)) {
                   unshield_error("Failed to write %i bytes to file '%s'", bytes_to_write, filename);
                   goto exit;
               }
@@ -1272,7 +1271,7 @@ bool unshield_file_save_old(Unshield* unshield, int index, const char* filename)
       bytes_left -= bytes_to_write;
 
       if (output) {
-        if (bytes_to_write != fwrite(output_buffer, 1, bytes_to_write, output))
+        if (bytes_to_write != unshield_fwrite(unshield, output_buffer, 1, bytes_to_write, output))
         {
           unshield_error("Failed to write %i bytes to file '%s'", bytes_to_write, filename);
           goto exit;
@@ -1295,7 +1294,7 @@ bool unshield_file_save_old(Unshield* unshield, int index, const char* filename)
   
 exit:
   unshield_reader_destroy(reader);
-  FCLOSE(output);
+  FCLOSE(unshield, output);
   FREE(input_buffer);
   FREE(output_buffer);
   return success;
diff --git a/lib/helper.c b/lib/helper.c
index 3d5d86f..25ed46a 100644
--- a/lib/helper.c
+++ b/lib/helper.c
@@ -11,8 +11,6 @@
 #include <unistd.h>
 
 #ifdef _WIN32
-  #define fseek _fseeki64
-  #define ftell _ftelli64
   #define realpath(N,R) _fullpath((R),(N),_MAX_PATH)
   #include <direct.h>
   #ifndef PATH_MAX
@@ -103,11 +101,12 @@ FILE* unshield_fopen_for_reading(Unshield* unshield, int index, const char* suff
     else
       q=filename;
 
-    sourcedir = opendir(dirname);
+    sourcedir = unshield_opendir(unshield, dirname);
     /* Search for the File case independent */
     if (sourcedir)
     {
-      for (dent=readdir(sourcedir);dent;dent=readdir(sourcedir))
+      for (dent=unshield_readdir(unshield, sourcedir);dent;
+           dent=unshield_readdir(unshield, sourcedir))
       {
         if (!(strcasecmp(q, dent->d_name)))
         {
@@ -134,11 +133,11 @@ FILE* unshield_fopen_for_reading(Unshield* unshield, int index, const char* suff
 #if VERBOSE
     unshield_trace("Opening file '%s'", filename);
 #endif
-    result = fopen(filename, "rb");
+    result = unshield_fopen(unshield, filename, "rb");
 
 exit:
     if (sourcedir)
-      closedir(sourcedir);
+      unshield_closedir(unshield, sourcedir);
     free(filename);
     free(dirname);
     return result;
@@ -147,13 +146,13 @@ FILE* unshield_fopen_for_reading(Unshield* unshield, int index, const char* suff
   return NULL;
 }
 
-long long unshield_fsize(FILE* file)
+long long unshield_fsize(Unshield* unshield, FILE* file)
 {
   long long result;
-  long long previous = ftell(file);
-  fseek(file, 0L, SEEK_END);
-  result = ftell(file);
-  fseek(file, previous, SEEK_SET);
+  long long previous = unshield_ftell(unshield, file);
+  unshield_fseek(unshield, file, 0L, SEEK_END);
+  result = unshield_ftell(unshield, file);
+  unshield_fseek(unshield, file, previous, SEEK_SET);
   return result;
 }
 
diff --git a/lib/internal.h b/lib/internal.h
index 7f01d59..9faf414 100644
--- a/lib/internal.h
+++ b/lib/internal.h
@@ -52,6 +52,8 @@ struct _Unshield
 {
   Header* header_list;
   char* filename_pattern;
+  const UnshieldIoCallbacks* io_callbacks;
+  void* io_userdata;
 };
 
 /*
@@ -77,13 +79,57 @@ void unshield_file_group_destroy(UnshieldFileGroup* self);
 char *unshield_get_base_directory_name(Unshield *unshield);
 long int unshield_get_path_max(Unshield* unshield);
 FILE* unshield_fopen_for_reading(Unshield* unshield, int index, const char* suffix);
-long long unshield_fsize(FILE* file);
+long long unshield_fsize(Unshield* unshield, FILE* file);
 bool unshield_read_common_header(uint8_t** buffer, CommonHeader* common);
 
 const char* unshield_get_utf8_string(Header* header, const void* buffer);
 const char* unshield_header_get_string(Header* header, uint32_t offset);
 uint8_t* unshield_header_get_buffer(Header* header, uint32_t offset);
 
+static inline void* unshield_fopen(Unshield* unshield, const char *filename, const char *modes)
+{
+    return unshield->io_callbacks->fopen(filename, modes, unshield->io_userdata);
+}
+
+static inline int unshield_fseek(Unshield* unshield, void *file, long int offset, int whence)
+{
+    return unshield->io_callbacks->fseek(file, offset, whence, unshield->io_userdata);
+}
+
+static inline long int unshield_ftell(Unshield* unshield, void *file)
+{
+    return unshield->io_callbacks->ftell(file, unshield->io_userdata);
+}
+
+static inline size_t unshield_fread(Unshield* unshield, void *ptr, size_t size, size_t n, void *file)
+{
+    return unshield->io_callbacks->fread(ptr, size, n, file, unshield->io_userdata);
+}
+
+static inline size_t unshield_fwrite(Unshield* unshield, const void *ptr, size_t size, size_t n, void *file)
+{
+    return unshield->io_callbacks->fwrite(ptr, size, n, file, unshield->io_userdata);
+}
+
+static inline int unshield_fclose(Unshield* unshield, void *ptr)
+{
+    return unshield->io_callbacks->fclose(ptr, unshield->io_userdata);
+}
+
+static inline void * unshield_opendir(Unshield* unshield, const char *name)
+{
+    return unshield->io_callbacks->opendir(name, unshield->io_userdata);
+}
+
+static inline int unshield_closedir(Unshield* unshield, void *dir)
+{
+    return unshield->io_callbacks->closedir(dir, unshield->io_userdata);
+}
+
+static inline struct dirent* unshield_readdir(Unshield* unshield, void *dir)
+{
+    return unshield->io_callbacks->readdir(dir, unshield->io_userdata);
+}
 
 /*
    Constants
@@ -100,8 +146,8 @@ uint8_t* unshield_header_get_buffer(Header* header, uint32_t offset);
 #define STRDUP(str)     ((str) ? strdup(str) : NULL)
 #define NEW(type, count)      ((type*)calloc(count, sizeof(type)))
 #define NEW1(type)      ((type*)calloc(1, sizeof(type)))
-#define FCLOSE(file)    if (file) { fclose(file); (file) = NULL; }
-#define FSIZE(file)     ((file) ? unshield_fsize(file) : 0)
+#define FCLOSE(unshield, file) if (file) { unshield_fclose(unshield, file); (file) = NULL; }
+#define FSIZE(unshield, file)     ((file) ? unshield_fsize(unshield, file) : 0)
 #define STREQ(s1,s2)    (0 == strcmp(s1,s2))
 
 static inline uint16_t get_unaligned_le16(const uint8_t *p)
diff --git a/lib/libunshield.c b/lib/libunshield.c
index e562933..e3dd06a 100644
--- a/lib/libunshield.c
+++ b/lib/libunshield.c
@@ -6,6 +6,82 @@
 #include <ctype.h>
 #include <stdlib.h>
 #include <string.h>
+#include <dirent.h>
+
+#ifdef _WIN32
+  #define unshield_native_fseek _fseeki64
+  #define unshield_native_ftell _ftelli64
+#else
+  #define unshield_native_fseek fseek
+  #define unshield_native_ftell ftell
+#endif
+
+
+void *unshield_default_fopen(const char *filename, const char *modes, void *userdata)
+{
+  (void)userdata;
+  return fopen(filename, modes);
+}
+
+int unshield_default_fseek(void *file, long int offset, int whence, void *userdata)
+{
+  (void)userdata;
+  return unshield_native_fseek(file, offset, whence);
+}
+
+long int unshield_default_ftell(void *file, void *userdata)
+{
+  (void)userdata;
+  return unshield_native_ftell(file);
+}
+
+size_t unshield_default_fread(void *ptr, size_t size, size_t n, void *file, void *userdata)
+{
+  (void)userdata;
+  return fread(ptr, size, n, file);
+}
+
+size_t unshield_default_fwrite(const void *ptr, size_t size, size_t n, void *file, void *userdata)
+{
+  (void)userdata;
+  return fwrite(ptr, size, n, file);
+}
+
+int unshield_default_fclose(void *file, void *userdata)
+{
+  (void)userdata;
+  return fclose(file);
+}
+
+void *unshield_default_opendir(const char *name, void *userdata)
+{
+  (void)userdata;
+  return opendir(name);
+}
+
+int unshield_default_closedir(void *dir, void *userdata)
+{
+  (void)userdata;
+  return closedir(dir);
+}
+
+struct dirent* unshield_default_readdir(void *dir, void *userdata)
+{
+  (void)userdata;
+  return readdir(dir);
+}
+
+static UnshieldIoCallbacks unshield_default_io_callbacks = {
+  .fopen = unshield_default_fopen,
+  .fseek = unshield_default_fseek,
+  .ftell = unshield_default_ftell,
+  .fread = unshield_default_fread,
+  .fwrite = unshield_default_fwrite,
+  .fclose = unshield_default_fclose,
+  .opendir = unshield_default_opendir,
+  .closedir = unshield_default_closedir,
+  .readdir = unshield_default_readdir,
+};
 
 /**
   Create filename pattern used by unshield_fopen_for_reading()
@@ -239,11 +315,11 @@ static bool unshield_read_headers(Unshield* unshield, int version)/*{{{*/
       Header* header = NEW1(Header);
       header->index = i;
 
-      header->size = FSIZE(file);
+      header->size = FSIZE(unshield, file);
       if (header->size < 4)
       {
         unshield_error("Header file %i too small", i);
-        FCLOSE(file);
+        FCLOSE(unshield, file);
         goto error;
       }
 
@@ -251,12 +327,12 @@ static bool unshield_read_headers(Unshield* unshield, int version)/*{{{*/
       if (!header->data)
       {
         unshield_error("Failed to allocate memory for header file %i", i);
-        FCLOSE(file);
+        FCLOSE(unshield, file);
         goto error;
       }
 
-      bytes_read = fread(header->data, 1, header->size, file);
-      FCLOSE(file);
+      bytes_read = unshield_fread(unshield, header->data, 1, header->size, file);
+      FCLOSE(unshield, file);
 
       if (bytes_read != header->size)
       {
@@ -346,6 +422,16 @@ Unshield* unshield_open(const char* filename)/*{{{*/
 }/*}}}*/
 
 Unshield* unshield_open_force_version(const char* filename, int version)/*{{{*/
+{
+  return unshield_open2_force_version(filename, version, NULL, NULL);
+}/*}}}*/
+
+Unshield* unshield_open2(const char* filename, const UnshieldIoCallbacks* callbacks, void* userdata)/*{{{*/
+{
+  return unshield_open2_force_version(filename, -1, callbacks, userdata);
+}/*}}}*/
+
+Unshield* unshield_open2_force_version(const char* filename, int version, const UnshieldIoCallbacks* callbacks, void* userdata)/*{{{*/
 {
   Unshield* unshield = NEW1(Unshield);
   if (!unshield)
@@ -354,6 +440,9 @@ Unshield* unshield_open_force_version(const char* filename, int version)/*{{{*/
     goto error;
   }
 
+  unshield->io_callbacks = callbacks == NULL ? &unshield_default_io_callbacks : callbacks;
+  unshield->io_userdata = userdata;
+
   if (!unshield_create_filename_pattern(unshield, filename))
   {
     unshield_error("Failed to create filename pattern");
diff --git a/lib/libunshield.h b/lib/libunshield.h
index f5940a4..8edaea7 100644
--- a/lib/libunshield.h
+++ b/lib/libunshield.h
@@ -35,6 +35,22 @@ Unshield* unshield_open(const char* filename);
 Unshield* unshield_open_force_version(const char* filename, int version);
 void unshield_close(Unshield* unshield);
 
+typedef struct
+{
+    void *(*fopen)(const char *filename, const char *modes, void *userdata);
+    int (*fseek)(void *file, long int offset, int whence, void *userdata);
+    long int (*ftell)(void *file, void *userdata);
+    size_t (*fread)(void *ptr, size_t size, size_t n, void *file, void *userdata);
+    size_t (*fwrite)(const void *ptr, size_t size, size_t n, void *file, void *userdata);
+    int (*fclose)(void *file, void *userdata);
+    void *(*opendir)(const char *name, void *userdata);
+    int (*closedir)(void *dir, void *userdata);
+    struct dirent* (*readdir)(void *dir, void *userdata);
+} UnshieldIoCallbacks;
+
+Unshield* unshield_open2(const char* filename, const UnshieldIoCallbacks* callbacks, void* userdata);
+Unshield* unshield_open2_force_version(const char* filename, int version, const UnshieldIoCallbacks* callbacks, void* userdata);
+
 /*
    Component functions
  */
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 3e7c543..2b18c2c 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -11,3 +11,4 @@ if(APPLE)
 else()
     add_subdirectory(v5/CVE-2015-1386)
 endif()
+add_subdirectory(v5/stack_memory_file)
diff --git a/test/v5/stack_memory_file/CMakeLists.txt b/test/v5/stack_memory_file/CMakeLists.txt
new file mode 100644
index 0000000..80b45d2
--- /dev/null
+++ b/test/v5/stack_memory_file/CMakeLists.txt
@@ -0,0 +1,7 @@
+add_executable(test_stack_memory_file test_stack_memory_file.c)
+target_link_libraries(test_stack_memory_file PUBLIC libunshield)
+
+add_test(
+    NAME test_stack_memory_file
+    COMMAND $<TARGET_FILE:test_stack_memory_file>
+)
diff --git a/test/v5/stack_memory_file/test_stack_memory_file.c b/test/v5/stack_memory_file/test_stack_memory_file.c
new file mode 100644
index 0000000..58f2356
--- /dev/null
+++ b/test/v5/stack_memory_file/test_stack_memory_file.c
@@ -0,0 +1,425 @@
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <dirent.h>
+#include <libunshield.h>
+
+typedef struct
+{
+  bool opened;
+  const char* name;
+  uint32_t index;
+  struct dirent dirent[2];
+} StackMemoryDirectory_t;
+
+typedef struct
+{
+  bool opened;
+  const char* name;
+  uint8_t *buf;
+  uint32_t size;
+  uint32_t current_pointer;
+} StackMemoryFile_t;
+
+typedef struct
+{
+  bool opened;
+  const char* filename;
+  StackMemoryDirectory_t directory;
+  StackMemoryFile_t files[3];
+} StackMemoryIoCallbacksUserData_t;
+
+void *stack_memory_fopen(const char *filename, const char *modes, void *userdata)
+{
+  (void)modes;
+  StackMemoryIoCallbacksUserData_t *userdata_stack_memory = (StackMemoryIoCallbacksUserData_t *) userdata;
+  for (size_t i = 0; i < sizeof(userdata_stack_memory->files) / sizeof(userdata_stack_memory->files[0]); ++i)
+  {
+    StackMemoryFile_t* file = &userdata_stack_memory->files[i];
+    if (file->name != NULL && strcmp(file->name, filename) == 0)
+    {
+      if (file->opened)
+        return NULL;
+      userdata_stack_memory->opened = true;
+      return file;
+    }
+  }
+  return NULL;
+}
+
+int stack_memory_fseek(void *file, long int offset, int whence, void *userdata)
+{
+  (void)userdata;
+  StackMemoryFile_t *stack_file = (StackMemoryFile_t *) file;
+  long int new_offset = (long int)stack_file->current_pointer;
+  switch (whence)
+  {
+    case SEEK_SET:
+      new_offset = offset;
+      break;
+    case SEEK_CUR:
+      new_offset += offset;
+      break;
+    case SEEK_END:
+      new_offset = (long int)stack_file->size + offset;
+      break;
+    default:
+      return 1;
+  }
+  if (new_offset < 0 && new_offset > stack_file->size)
+    return 1;
+  stack_file->current_pointer = new_offset;
+  return 0;
+}
+
+long int stack_memory_ftell(void *file, void *userdata)
+{
+  (void)userdata;
+  StackMemoryFile_t *stack_file = (StackMemoryFile_t *) file;
+  return (long int)stack_file->current_pointer;
+}
+
+size_t stack_memory_fread(void *ptr, size_t size, size_t n, void *file, void *userdata)
+{
+  (void)userdata;
+  if (size == 0 || n == 0)
+    return 0;
+  uint32_t total_size = size * n;
+  StackMemoryFile_t *stack_file = (StackMemoryFile_t *) file;
+  if (total_size > stack_file->current_pointer + stack_file->size)
+    total_size = stack_file->size - stack_file->current_pointer;
+  memcpy(ptr, stack_file->buf + stack_file->current_pointer, total_size);
+  stack_file->current_pointer += total_size;
+  if (stack_file->current_pointer == stack_file->size)
+    stack_file->current_pointer = EOF;
+  return total_size;
+}
+
+size_t stack_memory_fwrite(const void *ptr, size_t size, size_t n, void *file, void *userdata)
+{
+  (void)userdata;
+  if (size == 0 || n == 0)
+    return 0;
+  StackMemoryFile_t *stack_file = (StackMemoryFile_t *) file;
+  memcpy(stack_file->buf + stack_file->current_pointer, ptr, size * n);
+  stack_file->current_pointer += size * n;
+  return size * n;
+}
+
+int stack_memory_fclose(void *file, void *userdata)
+{
+  (void)userdata;
+  StackMemoryFile_t *stack_file = (StackMemoryFile_t *) file;
+  if (!stack_file->opened)
+    return EOF;
+  stack_file->opened = false;
+  return 0;
+}
+
+void *stack_memory_opendir(const char *name, void *userdata)
+{
+  StackMemoryIoCallbacksUserData_t *userdata_stack_memory = (StackMemoryIoCallbacksUserData_t *) userdata;
+  if (strcmp(userdata_stack_memory->directory.name, name) != 0)
+    return NULL;
+  if (userdata_stack_memory->directory.opened)
+    return NULL;
+  userdata_stack_memory->directory.opened = true;
+  userdata_stack_memory->directory.index = 0;
+  return &userdata_stack_memory->directory;
+}
+
+int stack_memory_closedir(void *dir, void *userdata)
+{
+  StackMemoryIoCallbacksUserData_t *userdata_stack_memory = (StackMemoryIoCallbacksUserData_t *) userdata;
+  if (dir != &userdata_stack_memory->directory)
+    return -1;
+  if (!userdata_stack_memory->directory.opened)
+    return -1;
+  userdata_stack_memory->directory.opened = false;
+  return 0;
+}
+
+struct dirent* stack_memory_readdir(void *dir, void *userdata)
+{
+  StackMemoryIoCallbacksUserData_t *userdata_stack_memory = (StackMemoryIoCallbacksUserData_t *) userdata;
+  if (dir != &userdata_stack_memory->directory)
+    return NULL;
+  if (userdata_stack_memory->directory.index >= sizeof(userdata_stack_memory->directory.dirent) / sizeof(userdata_stack_memory->directory.dirent[0]))
+    return NULL;
+  return &userdata_stack_memory->directory.dirent[userdata_stack_memory->directory.index++];
+}
+
+static UnshieldIoCallbacks stackMemoryFileIoCallbacks = {
+  .fopen = stack_memory_fopen,
+  .fseek = stack_memory_fseek,
+  .ftell = stack_memory_ftell,
+  .fread = stack_memory_fread,
+  .fwrite = stack_memory_fwrite,
+  .fclose = stack_memory_fclose,
+  .opendir = stack_memory_opendir,
+  .closedir = stack_memory_closedir,
+  .readdir = stack_memory_readdir,
+};
+
+int test_open_and_save()
+{
+  uint8_t test1_hdr_data[] = {
+    0x49, 0x53, 0x63, 0x28, // signature
+    0x00, 0x50, 0x00, 0x01, // version
+    0x00, 0x00, 0x00, 0x00, // volume_info
+    0x10, 0x00, 0x00, 0x00, // cab_descriptor_offset
+    0x01, 0x00, 0x00, 0x00, // cab_descriptor_size
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // 0x8
+    0x76, 0x02, 0x00, 0x00, // header->cab.file_table_offset
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, // header->cab.file_table_size
+    0x00, 0x00, 0x00, 0x00, // header->cab.file_table_size2
+    0x00, 0x00, 0x00, 0x00, // header->cab.directory_count
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // 0x8
+    0x01, 0x00, 0x00, 0x00, // header->cab.file_count
+    0x00, 0x00, 0x00, 0x00, // header->cab.cab.file_table_offset2
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // 0xe
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00,
+    0x04, 0x00, 0x00, 0x00, // header->file_table[1]
+    0x2a, 0x00, 0x00, 0x00, // fd->name_offset
+    0x00, 0x00, 0x00, 0x00, // fd->directory_index
+    0x00, 0x00, // fd->flags
+    0x05, 0x00, 0x00, 0x00, // fd->expanded_size
+    0x05, 0x00, 0x00, 0x00, // fd->compressed_size
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // 0x14
+    0x40, 0x00, 0x00, 0x00, // fd->data_offset
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // md5
+    'T', 'E', 'S', 'T', 0x00, // name
+  };
+  uint8_t test1_cab_data[] = {
+    0x49, 0x53, 0x63, 0x28, // signature
+    0x00, 0x50, 0x00, 0x01, // version
+    0x00, 0x00, 0x00, 0x00, // volume_info
+    0x10, 0x00, 0x00, 0x00, // cab_descriptor_offset
+    0x01, 0x00, 0x00, 0x00, // cab_descriptor_size
+    0x00, 0x00, 0x00, 0x00, // volume_header.data_offset;
+    0x00, 0x00, 0x00, 0x00, // volume_header.unknown;
+    0x00, 0x00, 0x00, 0x00, // volume_header.first_file_index;
+    0x00, 0x00, 0x00, 0x00, // volume_header.last_file_index;
+    0x40, 0x00, 0x00, 0x00, // volume_header.first_file_offset;
+    0x05, 0x00, 0x00, 0x00, // volume_header.first_file_size_expanded;
+    0x05, 0x00, 0x00, 0x00, // volume_header.first_file_size_compressed;
+    0x40, 0x00, 0x00, 0x00, // volume_header.last_file_offset;
+    0x05, 0x00, 0x00, 0x00, // volume_header.last_file_size_expanded;
+    0x05, 0x00, 0x00, 0x00, // volume_header.last_file_size_compressed;
+    0x00, 0x00, 0x00, 0x00,
+    'T', 'E', 'S', 'T', 0x00, // name
+  };
+  uint8_t test_output_txt_data[0x10] = { 0, };
+  StackMemoryIoCallbacksUserData_t stack_file = {
+    .opened = false,
+    .filename = "test.cab",
+    .directory = {
+      .opened = false,
+      .name = ".",
+      .dirent = {
+        [0] = { .d_name = "test1.hdr" },
+        [1] = { .d_name = "test1.cab" },
+      },
+    },
+    .files = {
+      [0] = {
+        .name = "./test1.hdr",
+        .buf = test1_hdr_data,
+        .size = sizeof (test1_hdr_data),
+      },
+      [1] = {
+        .name = "./test1.cab",
+        .buf = test1_cab_data,
+        .size = sizeof (test1_cab_data),
+      },
+      [2] = {
+        .name = "test_output.txt",
+        .buf = test_output_txt_data,
+        .size = sizeof (test_output_txt_data),
+      },
+    }
+  };
+
+  Unshield *unshield = unshield_open2(stack_file.filename, &stackMemoryFileIoCallbacks, &stack_file);
+  if (unshield == NULL)
+    return EXIT_FAILURE;
+
+  if (!stack_file.opened)
+    return EXIT_FAILURE;
+
+  if (unshield_file_count(unshield) != 1)
+  {
+    unshield_close(unshield);
+    return EXIT_FAILURE;
+  }
+
+  if (!unshield_file_save(unshield, 0, "test_output.txt"))
+  {
+    unshield_close(unshield);
+    return EXIT_FAILURE;
+  }
+
+  if (strcmp((char*)test_output_txt_data, "TEST") != 0)
+  {
+      unshield_close(unshield);
+      return EXIT_FAILURE;
+  }
+
+  unshield_close(unshield);
+
+  return EXIT_SUCCESS;
+}
+
+
+int main()
+{
+  if (test_open_and_save() != EXIT_SUCCESS)
+    return EXIT_FAILURE;
+
+  return EXIT_SUCCESS;
+}