diff --git a/dub.selections.json b/dub.selections.json
new file mode 100644
index 0000000..c2bab4e
--- /dev/null
+++ b/dub.selections.json
@@ -0,0 +1,6 @@
+{
+	"fileVersion": 1,
+	"versions": {
+		"libxdiff": {"version":"e2396bc172eba813cdcd1a96c494e35d687f576a","repository":"git+https://git.zhirov.kz/dlang/xdiff.git"}
+	}
+}
diff --git a/source/app.d b/source/app.d
index 7b3a7ed..b1e9a4b 100644
--- a/source/app.d
+++ b/source/app.d
@@ -1,322 +1,20 @@
-import std.stdio : writeln, stderr, File;
-import std.getopt;
-import std.file : read, exists;
-import std.exception : enforce, collectException;
-import core.stdc.stdlib : malloc, free, realloc;
-import core.stdc.string : memcpy;
-import core.sys.posix.unistd : posix_write = write;
+import libxdiff;
 
-import xdiff;
+import std.conv : to;
+import std.stdio : writefln, writeln;
+import std.file : read;
 
-// ------------------------------
-// RAII для mmfile_t
-// ------------------------------
-struct MmFile
+void main()
 {
-	mmfile_t mf;
+	auto file1 = new MMFile(cast(const(ubyte)[]) read("/tmp/diff1.d"));
+	auto file2 = new MMFile(cast(const(ubyte)[]) read("/tmp/diff2.d"));
 
-	// фабрика вместо конструктора по умолчанию
-	static MmFile create(long bsize = 8 * 1024, ulong flags = XDL_MMF_ATOMIC)
-	{
-		MmFile m;
-		enforce(xdl_init_mmfile(&m.mf, bsize, flags) == 0, "xdl_init_mmfile failed");
-		return m;
-	}
+	auto patch = file1.computePatch(file2);
 
-	void deinit()
-	{
-		xdl_free_mmfile(&mf);
-	}
-}
-
-// ------------------------------
-// Коллбэки вывода
-// ------------------------------
-extern (C) int mmfileOut(void* priv, mmbuffer_t* mb, int nbuf)
-{
-	auto mmfOut = cast(mmfile_t*) priv;
-	return xdl_writem_mmfile(mmfOut, mb, nbuf) < 0 ? -1 : 0;
-}
-
-extern (C) int fdOut(void* priv, mmbuffer_t* mb, int nbuf)
-{
-	const fd = cast(int) cast(size_t) priv; // 1=stdout, 2=stderr
-	foreach (i; 0 .. nbuf)
-	{
-		auto ptr = mb[i].ptr;
-		auto left = cast(size_t) mb[i].size;
-		while (left)
-		{
-			auto n = posix_write(fd, ptr, left);
-			if (n < 0)
-				return -1;
-			ptr += n;
-			left -= cast(size_t) n;
-		}
-	}
-	return 0;
-}
-
-// ------------------------------
-// Загрузка/выгрузка
-// ------------------------------
-void loadMmFile(ref MmFile m, string path)
-{
-	try
-	{
-		enforce(exists(path), "no such file: " ~ path);
-		auto data = cast(const(char)[]) read(path); // читает весь файл
-		auto dst = cast(char*) xdl_mmfile_writeallocate(&m.mf, data.length);
-		enforce(dst !is null, "xdl_mmfile_writeallocate failed (null)");
-		if (data.length)
-			memcpy(dst, data.ptr, data.length);
-	}
-	catch (Exception e)
-	{
-		// пробрасываем с контекстом пути
-		throw new Exception("loadMmFile(" ~ path ~ "): " ~ e.msg);
-	}
-}
-
-void dumpMmFile(const ref MmFile m, string path)
-{
-	File f = File(path, "wb");
-	scope (exit)
-		f.close();
-	long sz = 0;
-	auto blk = cast(char*) xdl_mmfile_first(cast(mmfile_t*)&m.mf, &sz);
-	while (blk !is null)
-	{
-		f.rawWrite(blk[0 .. cast(size_t) sz]);
-		blk = cast(char*) xdl_mmfile_next(cast(mmfile_t*)&m.mf, &sz);
-	}
-}
-
-// ------------------------------
-// Аллокатор
-// ------------------------------
-extern (C) void* wrap_malloc(void*, uint size)
-{
-	return malloc(size);
-}
-
-extern (C) void wrap_free(void*, void* ptr)
-{
-	free(ptr);
-}
-
-extern (C) void* wrap_realloc(void*, void* ptr, uint size)
-{
-	return realloc(ptr, size);
-}
-
-void installAllocator()
-{
-	memallocator_t malt;
-	malt.priv = null;
-	malt.malloc = &wrap_malloc;
-	malt.free = &wrap_free;
-	malt.realloc = &wrap_realloc;
-	enforce(xdl_set_allocator(&malt) == 0, "xdl_set_allocator failed");
-}
-
-// ------------------------------
-// Команды
-// ------------------------------
-int doDiff(ref MmFile a, ref MmFile b, long ctxlen)
-{
-	xpparam_t xpp;
-	xpp.flags = 0;
-	xdemitconf_t xecfg;
-	xecfg.ctxlen = ctxlen;
-	xdemitcb_t ecb;
-	ecb.priv = cast(void*) cast(size_t) 1;
-	ecb.outf = &fdOut;
-	return xdl_diff(&a.mf, &b.mf, &xpp, &xecfg, &ecb);
-}
-
-int doPatch(ref MmFile orig, ref MmFile patch, int mode)
-{
-	xdemitcb_t outcb;
-	outcb.priv = cast(void*) cast(size_t) 1;
-	outcb.outf = &fdOut;
-	xdemitcb_t rejcb;
-	rejcb.priv = cast(void*) cast(size_t) 2;
-	rejcb.outf = &fdOut;
-	return xdl_patch(&orig.mf, &patch.mf, mode, &outcb, &rejcb);
-}
-
-int doBDiff(ref MmFile a, ref MmFile b, long bsize)
-{
-	bdiffparam_t bdp;
-	bdp.bsize = bsize;
-	xdemitcb_t ecb;
-	ecb.priv = cast(void*) cast(size_t) 1;
-	ecb.outf = &fdOut;
-	return xdl_bdiff(&a.mf, &b.mf, &bdp, &ecb);
-}
-
-int doRaBDiff(ref MmFile a, ref MmFile b)
-{
-	xdemitcb_t ecb;
-	ecb.priv = cast(void*) cast(size_t) 1;
-	ecb.outf = &fdOut;
-	return xdl_rabdiff(&a.mf, &b.mf, &ecb);
-}
-
-int doBPatch(ref MmFile base, ref MmFile binPatch)
-{
-	xdemitcb_t ecb;
-	ecb.priv = cast(void*) cast(size_t) 1;
-	ecb.outf = &fdOut;
-	return xdl_bpatch(&base.mf, &binPatch.mf, &ecb);
-}
-
-// ------------------------------
-// CLI
-// ------------------------------
-enum Cmd
-{
-	diff,
-	patch,
-	bdiff,
-	rabdiff,
-	bpatch
-}
-
-private Cmd parseCmd(string s)
-{
-	final switch (s)
-	{
-	case "diff":
-		return Cmd.diff;
-	case "patch":
-		return Cmd.patch;
-	case "bdiff":
-		return Cmd.bdiff;
-	case "rabdiff":
-		return Cmd.rabdiff;
-	case "bpatch":
-		return Cmd.bpatch;
-	}
-}
-
-/// Короткая справка
-void printUsage(string prg)
-{
-	stderr.writefln(
-		"use: %1$s diff   [-C N]  FROM TO\n" ~
-			"     %1$s patch           ORIG PATCH\n" ~
-			"     %1$s bdiff  [-B N]   FROM TO\n" ~
-			"     %1$s rabdiff         FROM TO\n" ~
-			"     %1$s bpatch          ORIG PATCH\n",
-			prg);
-}
-
-/// Парсинг подкоманды + её опций. Возвращаем уже «очищенный» список позиционных.
-struct Parsed
-{
-	Cmd cmd;
-	long ctxlen = 3; // для diff
-	long bsize = 16; // для bdiff
-	string[] positional; // оставшиеся позиционные (пути)
-}
-
-Parsed parseArgs(string[] args)
-{
-	enforce(args.length >= 2, "no subcommand");
-	auto sub = args[1];
-	auto cmd = parseCmd(sub);
-
-	long ctxlen = 3;
-	long bsize = 16;
-	bool helpWanted = false;
-
-	// Опции и позиционные ТОЛЬКО после подкоманды
-	string[] optArgs = args.length > 2 ? args[2 .. $].dup : [];
-
-	// getopt выкинет опции из optArgs и оставит только позиционные
-	auto r = getopt(optArgs,
-		"h|help", &helpWanted,
-		"C", &ctxlen, // актуально для `diff`
-		"B", &bsize // актуально для `bdiff`
-
-		
+	writeln(patch);
 
+	writefln(
+		"file1: %s\nfile2: %s",
+		file1.size, file2.size
 	);
-	enforce(!helpWanted, "help");
-
-	Parsed p;
-	p.cmd = cmd;
-	p.ctxlen = ctxlen;
-	p.bsize = bsize;
-	p.positional = optArgs; // здесь уже только пути
-	return p;
-}
-
-int main(string[] args)
-{
-	// 1) Парсим
-	Parsed p;
-	try
-	{
-		p = parseArgs(args);
-	}
-	catch (Exception)
-	{
-		printUsage(args[0]);
-		return 1;
-	}
-	if (p.positional.length != 2)
-	{
-		// каждая подкоманда требует ровно 2 пути
-		printUsage(args[0]);
-		return 1;
-	}
-	auto p1 = p.positional[0];
-	auto p2 = p.positional[1];
-
-	// 2) Аллокатор libxdiff
-	installAllocator();
-
-	// 3) Готовим входы
-	auto mf1 = MmFile.create();
-	scope (exit)
-		mf1.deinit();
-	auto mf2 = MmFile.create();
-	scope (exit)
-		mf2.deinit();
-
-	try
-	{
-		loadMmFile(mf1, p1);
-		loadMmFile(mf2, p2);
-	}
-	catch (Exception e)
-	{
-		stderr.writeln(e.msg);
-		return 1;
-	}
-
-	// 4) Запускаем действие
-	int rc = 0;
-	final switch (p.cmd)
-	{
-	case Cmd.diff:
-		rc = doDiff(mf1, mf2, p.ctxlen);
-		break;
-	case Cmd.patch:
-		rc = doPatch(mf1, mf2, XDL_PATCH_NORMAL);
-		break;
-	case Cmd.bdiff:
-		rc = doBDiff(mf1, mf2, p.bsize);
-		break;
-	case Cmd.rabdiff:
-		rc = doRaBDiff(mf1, mf2);
-		break;
-	case Cmd.bpatch:
-		rc = doBPatch(mf1, mf2);
-		break;
-	}
-	return rc < 0 ? 2 : 0;
 }
diff --git a/source/libxdiff/init.d b/source/libxdiff/init.d
new file mode 100644
index 0000000..546679c
--- /dev/null
+++ b/source/libxdiff/init.d
@@ -0,0 +1,70 @@
+module libxdiff.init;
+
+import xdiff;
+
+import core.stdc.stdlib : malloc, free, realloc;
+import std.exception : enforce;
+import core.stdc.errno : errno;
+import core.stdc.string : strerror;
+import std.string : fromStringz;
+import std.conv : to;
+
+private __gshared bool _allocatorReady = false;
+package(libxdiff) alias ByteArray = const(ubyte)[];
+
+extern (C)
+{
+	private void* wrap_malloc(void*, uint size)
+	{
+		return malloc(size);
+	}
+
+	private void wrap_free(void*, void* p)
+	{
+		free(p);
+	}
+
+	private void* wrap_realloc(void*, void* p, uint size)
+	{
+		return realloc(p, size);
+	}
+}
+
+private void setAllocator()
+{
+	if (_allocatorReady)
+		return;
+
+	memallocator_t m = {null, &wrap_malloc, &wrap_free, &wrap_realloc};
+
+	enforce(xdl_set_allocator(&m) == 0,
+		"xdl_set_allocator failed: " ~ strerror(errno).fromStringz);
+	_allocatorReady = true;
+}
+
+mmfile_t initMmfile(size_t len)
+{
+	setAllocator();
+	mmfile_t mf;
+	enforce(xdl_init_mmfile(&mf, len.to!long, XDL_MMF_ATOMIC) == 0,
+		"xdl_init_mmfile failed: " ~ strerror(errno).fromStringz);
+	return mf;
+}
+
+abstract class MM
+{
+protected:
+	mmfile_t _inner;
+public:
+	final @property size_t size()
+	{
+		return xdl_mmfile_size(&_inner).to!size_t;
+	}
+
+	// Проверка «компактности» — содержимое лежит в одном блоке
+	// (важно для бинарных функций, которым нужно сплошное непрерывное представление).
+	final bool isCompact() const
+	{
+		return xdl_mmfile_iscompact(cast(mmfile_t*)&_inner) != 0;
+	}
+}
diff --git a/source/libxdiff/mmblocks.d b/source/libxdiff/mmblocks.d
new file mode 100644
index 0000000..8ec975a
--- /dev/null
+++ b/source/libxdiff/mmblocks.d
@@ -0,0 +1,41 @@
+module libxdiff.mmblocks;
+
+import xdiff;
+
+import libxdiff.init;
+
+import std.exception : enforce;
+import core.stdc.errno : errno;
+import core.stdc.string : strerror;
+import std.string : fromStringz;
+import std.conv : to;
+
+private enum DEFAULT_BSIZE = 8 * 1024;
+
+final class MMBlocks : MM
+{
+public:
+	this()
+	{
+		_inner = initMmfile(DEFAULT_BSIZE);
+	}
+
+	package(libxdiff) mmfile_t* ptr() @trusted
+	{
+		return &_inner;
+	}
+
+	const(ubyte)[] asSlice() @trusted
+	{
+		enforce(isCompact(), "MMFile must be compact for asSliceConst");
+		auto h = _inner.head;
+		return h is null || h.size <= 0 ? [] : (cast(const(ubyte)*) h.ptr)[0 .. h.size.to!size_t];
+	}
+
+	override string toString() const @trusted
+	{
+		enforce(isCompact(), "MMFile must be compact for asSliceConst");
+		auto h = _inner.head;
+		return h is null || h.size <= 0 ? [] : fromStringz(cast(const char*) h.ptr).idup;
+	}
+}
diff --git a/source/libxdiff/mmfile.d b/source/libxdiff/mmfile.d
new file mode 100644
index 0000000..1bcbca4
--- /dev/null
+++ b/source/libxdiff/mmfile.d
@@ -0,0 +1,79 @@
+module libxdiff.mmfile;
+
+import xdiff;
+
+import libxdiff.init;
+import libxdiff.mmblocks;
+
+import std.exception : enforce;
+import core.stdc.errno : errno;
+import core.stdc.string : strerror;
+import std.string : fromStringz;
+import std.conv : to;
+import std.string : join, representation;
+
+final class MMFile : MM
+{
+private:
+	void _write(ByteArray data)
+	{
+		_inner = initMmfile(0);
+
+		if (data.length > 0)
+		{
+			auto length = data.length.to!long;
+			auto wrote = xdl_write_mmfile(&_inner, data.ptr, length);
+			enforce(wrote == length,
+				"xdl_write_mmfile wrote less than requested: " ~ strerror(errno).fromStringz);
+		}
+	}
+
+public:
+	this(ByteArray data)
+	{
+		_write(data);
+	}
+
+	this(string data)
+	{
+		_write(data.representation);
+	}
+
+	this(string[] data)
+	{
+		_write(data.join('\n').representation);
+	}
+
+	~this()
+	{
+		if (_inner.head !is null)
+			xdl_free_mmfile(&_inner);
+	}
+
+	MMBlocks computePatch(ref MMFile other, long ctxlen = 3)
+	{
+		auto patch = new MMBlocks();
+
+		extern (C) int emitToPatch(void* priv, mmbuffer_t* bufs, int num)
+		{
+			auto target = cast(MMBlocks) priv;
+			foreach (i; 0 .. num)
+			{
+				mmbuffer_t* buf = &bufs[i];
+				long written = xdl_writem_mmfile(target.ptr(), buf, 1);
+				if (written < 0 || written != buf.size)
+					return -1;
+			}
+			return 0;
+		}
+
+		xpparam_t xpp = {0};
+		xdemitconf_t xec = {ctxlen};
+		xdemitcb_t ecb = {cast(void*) patch, &emitToPatch};
+
+		enforce(xdl_diff(&_inner, &other._inner, &xpp, &xec, &ecb) == 0,
+			"xdl_diff failed: " ~ strerror(errno).fromStringz);
+
+		return patch;
+	}
+}
diff --git a/source/libxdiff/package.d b/source/libxdiff/package.d
new file mode 100644
index 0000000..3e27fe2
--- /dev/null
+++ b/source/libxdiff/package.d
@@ -0,0 +1,4 @@
+module libxdiff;
+
+public import libxdiff.mmfile;
+public import libxdiff.mmblocks;