Method _apply_patch

utility/file_access_patched_gdre.cpp:40–84

#include "file_access_gdre.h"

Error FileAccessPatchedGDRE::_apply_patch() const {
	ERR_FAIL_COND_V(!is_open(), FAILED);

	String path = old_file->get_path();
	Vector<PackedData::PackedFile> delta_patches = GDREPackedData::get_singleton()->get_delta_patches(path);
	Vector<uint8_t> old_file_data = old_file->get_buffer(old_file->get_length());

	for (int i = 0; i < delta_patches.size(); ++i) {
		const PackedData::PackedFile &delta_patch = delta_patches[i];
		ERR_FAIL_COND_V(delta_patch.bundle, FAILED);

		Error err = OK;

		uint64_t total_usec_start = OS::get_singleton()->get_ticks_usec();
		uint64_t io_usec_start = OS::get_singleton()->get_ticks_usec();

		Ref<FileAccess> patch_file = FileAccess::open(delta_patch.pack, FileAccess::READ, &err);
		ERR_FAIL_COND_V(err != OK, err);

		patch_file->seek(delta_patch.offset);
		ERR_FAIL_COND_V(patch_file->get_error() != OK, patch_file->get_error());

		Vector<uint8_t> patch_data = patch_file->get_buffer(delta_patch.size);
		ERR_FAIL_COND_V(patch_data.is_empty(), ERR_FILE_CANT_READ);

		uint64_t io_usec_end = OS::get_singleton()->get_ticks_usec();
		uint64_t decode_usec_start = OS::get_singleton()->get_ticks_usec();

		Vector<uint8_t> new_file_data;
		err = DeltaEncoding::decode_delta(old_file_data, patch_data, new_file_data);
		ERR_FAIL_COND_V_MSG(err != OK, err, vformat("Failed to apply delta patch (%d of %d) to \"%s\".", i + 1, delta_patches.size(), path));

		uint64_t decode_usec_end = OS::get_singleton()->get_ticks_usec();

		old_file_data = new_file_data;

		uint64_t total_usec_end = OS::get_singleton()->get_ticks_usec();

		print_verbose(vformat(U"Applied delta patch to \"%s\" from \"%s\" in %d μs (%d μs I/O, %d μs decoding).", path, delta_patch.pack.get_file(), total_usec_end - total_usec_start, io_usec_end - io_usec_start, decode_usec_end - decode_usec_start));
	}

	patched_file_data = old_file_data;
	patched_file.instantiate();
	return patched_file->open_custom(patched_file_data.ptr(), patched_file_data.size());
}

bool FileAccessPatchedGDRE::_try_apply_patch() const {
	if (last_error != OK) {