Add decompression command

native/jni/magiskboot/ramdisk.cpp

@@ -29,6 +29,7 @@ public:
 	void restore();
 	void backup(const char *orig);
 	void compress();
+	void decompress();
 };
 
 void magisk_cpio::patch(bool keepverity, bool keepforceencrypt) {
@@ -206,6 +207,8 @@ void magisk_cpio::backup(const char *orig) {
 }
 
 void magisk_cpio::compress() {
+	if (exists(ramdisk_xz))
+		return;
 	fprintf(stderr, "Compressing cpio -> [%s]\n", ramdisk_xz);
 	auto init = entries.extract("init");
 	XZEncoder encoder;
@@ -219,6 +222,22 @@ void magisk_cpio::compress() {
 	insert(xz);
 }
 
+void magisk_cpio::decompress() {
+	auto it = entries.find(ramdisk_xz);
+	if (it == entries.end())
+		return;
+	fprintf(stderr, "Decompressing cpio [%s]\n", ramdisk_xz);
+	LZMADecoder decoder;
+	decoder.set_out(make_unique<BufOutStream>());
+	decoder.write(it->second->data, it->second->filesize);
+	decoder.finalize();
+	entries.erase(it);
+	char *buf;
+	size_t sz;
+	static_cast<BufOutStream *>(decoder.get_out())->getbuf(buf, sz);
+	load_cpio(buf, sz);
+}
+
 int cpio_commands(int argc, char *argv[]) {
 	char *incpio = argv[0];
 	++argv;
@@ -251,6 +270,8 @@ int cpio_commands(int argc, char *argv[]) {
 			return 0;
 		} else if (strcmp(cmdv[0], "compress") == 0){
 			cpio.compress();
+		} else if (strcmp(cmdv[0], "decompress") == 0){
+			cpio.decompress();
 		} else if (cmdc == 2 && strcmp(cmdv[0], "exists") == 0) {
 			exit(!cpio.exists(cmdv[1]));
 		} else if (cmdc == 2 && strcmp(cmdv[0], "backup") == 0) {

native/jni/utils/include/OutStream.h

@@ -64,14 +64,20 @@ public:
 		return true;
 	}
 
-	template <typename T>
-	void release(void *&b, T &len) {
+	template <typename bytes, typename length>
+	void release(bytes *&b, length &len) {
 		b = buf;
 		len = off;
 		buf = nullptr;
 		off = cap = 0;
 	}
 
+	template <typename bytes, typename length>
+	void getbuf(bytes *&b, length &len) const {
+		b = buf;
+		len = off;
+	}
+
 	~BufOutStream() override {
 		free(buf);
 	}