4 files changed, 21 insertions, 9 deletions
diff --git a/core/io/file_access_pack.cpp b/core/io/file_access_pack.cpp
index 37240f234a..024ec3b2b5 100644
--- a/core/io/file_access_pack.cpp
+++ b/core/io/file_access_pack.cpp
@@ -34,9 +34,9 @@
 
 #include <stdio.h>
 
-Error PackedData::add_pack(const String &p_path, bool p_replace_files) {
+Error PackedData::add_pack(const String &p_path, bool p_replace_files, size_t p_offset) {
 	for (int i = 0; i < sources.size(); i++) {
-		if (sources[i]->try_open_pack(p_path, p_replace_files)) {
+		if (sources[i]->try_open_pack(p_path, p_replace_files, p_offset)) {
 			return OK;
 		}
 	}
@@ -123,15 +123,24 @@ PackedData::~PackedData() {
 
 //////////////////////////////////////////////////////////////////
 
-bool PackedSourcePCK::try_open_pack(const String &p_path, bool p_replace_files) {
+bool PackedSourcePCK::try_open_pack(const String &p_path, bool p_replace_files, size_t p_offset) {
 	FileAccess *f = FileAccess::open(p_path, FileAccess::READ);
 	if (!f) {
 		return false;
 	}
 
+	f->seek(p_offset);
+
 	uint32_t magic = f->get_32();
 
 	if (magic != PACK_HEADER_MAGIC) {
+		// loading with offset feature not supported for self contained exe files
+		if (p_offset != 0) {
+			f->close();
+			memdelete(f);
+			ERR_FAIL_V_MSG(false, "Loading self-contained executable with offset not supported.");
+		}
+
 		//maybe at the end.... self contained exe
 		f->seek_end();
 		f->seek(f->get_position() - 4);
@@ -191,7 +200,7 @@ bool PackedSourcePCK::try_open_pack(const String &p_path, bool p_replace_files)
 		uint64_t size = f->get_64();
 		uint8_t md5[16];
 		f->get_buffer(md5, 16);
-		PackedData::get_singleton()->add_path(p_path, path, ofs, size, md5, this, p_replace_files);
+		PackedData::get_singleton()->add_path(p_path, path, ofs + p_offset, size, md5, this, p_replace_files);
 	}
 
 	f->close();
diff --git a/core/io/file_access_pack.h b/core/io/file_access_pack.h
index 348bc0c450..6e316119cb 100644
--- a/core/io/file_access_pack.h
+++ b/core/io/file_access_pack.h
@@ -108,7 +108,7 @@ public:
 	_FORCE_INLINE_ bool is_disabled() const { return disabled; }
 
 	static PackedData *get_singleton() { return singleton; }
-	Error add_pack(const String &p_path, bool p_replace_files);
+	Error add_pack(const String &p_path, bool p_replace_files, size_t p_offset);
 
 	_FORCE_INLINE_ FileAccess *try_open_path(const String &p_path);
 	_FORCE_INLINE_ bool has_path(const String &p_path);
@@ -119,14 +119,14 @@ public:
 
 class PackSource {
 public:
-	virtual bool try_open_pack(const String &p_path, bool p_replace_files) = 0;
+	virtual bool try_open_pack(const String &p_path, bool p_replace_files, size_t p_offset) = 0;
 	virtual FileAccess *get_file(const String &p_path, PackedData::PackedFile *p_file) = 0;
 	virtual ~PackSource() {}
 };
 
 class PackedSourcePCK : public PackSource {
 public:
-	virtual bool try_open_pack(const String &p_path, bool p_replace_files);
+	virtual bool try_open_pack(const String &p_path, bool p_replace_files, size_t p_offset);
 	virtual FileAccess *get_file(const String &p_path, PackedData::PackedFile *p_file);
 };
 
diff --git a/core/io/file_access_zip.cpp b/core/io/file_access_zip.cpp
index c3a62706c7..974bb65a18 100644
--- a/core/io/file_access_zip.cpp
+++ b/core/io/file_access_zip.cpp
@@ -147,8 +147,11 @@ unzFile ZipArchive::get_file_handle(String p_file) const {
 	return pkg;
 }
 
-bool ZipArchive::try_open_pack(const String &p_path, bool p_replace_files) {
+bool ZipArchive::try_open_pack(const String &p_path, bool p_replace_files, size_t p_offset = 0) {
 	//printf("opening zip pack %ls, %i, %i\n", p_name.c_str(), p_name.extension().nocasecmp_to("zip"), p_name.extension().nocasecmp_to("pcz"));
+	// load with offset feature only supported for PCK files
+	ERR_FAIL_COND_V_MSG(p_offset != 0, false, "Invalid PCK data. Note that loading files with a non-zero offset isn't supported with ZIP archives.");
+
 	if (p_path.get_extension().nocasecmp_to("zip") != 0 && p_path.get_extension().nocasecmp_to("pcz") != 0) {
 		return false;
 	}
diff --git a/core/io/file_access_zip.h b/core/io/file_access_zip.h
index 776e830f36..ec51a9e4fb 100644
--- a/core/io/file_access_zip.h
+++ b/core/io/file_access_zip.h
@@ -69,7 +69,7 @@ public:
 
 	bool file_exists(String p_name) const;
 
-	virtual bool try_open_pack(const String &p_path, bool p_replace_files);
+	virtual bool try_open_pack(const String &p_path, bool p_replace_files, size_t p_offset);
 	FileAccess *get_file(const String &p_path, PackedData::PackedFile *p_file);
 
 	static ZipArchive *get_singleton();