diff --git a/Makefile b/Makefile
index 5cd141d5af..cd7dd9723d 100644
--- a/Makefile
+++ b/Makefile
@@ -1854,6 +1854,7 @@ VCSSVN_OBJS += vcs-svn/line_buffer.o
 VCSSVN_OBJS += vcs-svn/sliding_window.o
 VCSSVN_OBJS += vcs-svn/repo_tree.o
 VCSSVN_OBJS += vcs-svn/fast_export.o
+VCSSVN_OBJS += vcs-svn/svndiff.o
 VCSSVN_OBJS += vcs-svn/svndump.o
 
 VCSSVN_TEST_OBJS += test-obj-pool.o
@@ -1997,6 +1998,7 @@ VCSSVN_H += vcs-svn/line_buffer.h
 VCSSVN_H += vcs-svn/sliding_window.h
 VCSSVN_H += vcs-svn/repo_tree.h
 VCSSVN_H += vcs-svn/fast_export.h
+VCSSVN_H += vcs-svn/svndiff.h
 VCSSVN_H += vcs-svn/svndump.h
 
 $(VCSSVN_OBJS) $(VCSSVN_TEST_OBJS): $(LIB_H) $(VCSSVN_H)
diff --git a/t/t9011-svn-da.sh b/t/t9011-svn-da.sh
new file mode 100755
index 0000000000..ee0c1e2087
--- /dev/null
+++ b/t/t9011-svn-da.sh
@@ -0,0 +1,35 @@
+#!/bin/sh
+
+test_description='test parsing of svndiff0 files
+
+Using the "test-svn-fe -d" helper, check that svn-fe correctly
+interprets deltas using various facilities (some from the spec,
+some only learned from practice).
+'
+. ./test-lib.sh
+
+>empty
+printf foo >preimage
+
+test_expect_success 'reject empty delta' '
+	test_must_fail test-svn-fe -d preimage empty 0
+'
+
+test_expect_success 'delta can empty file' '
+	printf "SVNQ" | q_to_nul >clear.delta &&
+	test-svn-fe -d preimage clear.delta 4 >actual &&
+	test_cmp empty actual
+'
+
+test_expect_success 'reject svndiff2' '
+	printf "SVN\002" >bad.filetype &&
+	test_must_fail test-svn-fe -d preimage bad.filetype 4
+'
+
+test_expect_failure 'one-window empty delta' '
+	printf "SVNQ%s" "QQQQQ" | q_to_nul >clear.onewindow &&
+	test-svn-fe -d preimage clear.onewindow 9 >actual &&
+	test_cmp empty actual
+'
+
+test_done
diff --git a/test-svn-fe.c b/test-svn-fe.c
index b42ba789b1..66bd04022d 100644
--- a/test-svn-fe.c
+++ b/test-svn-fe.c
@@ -4,15 +4,41 @@
 
 #include "git-compat-util.h"
 #include "vcs-svn/svndump.h"
+#include "vcs-svn/svndiff.h"
+#include "vcs-svn/sliding_window.h"
+#include "vcs-svn/line_buffer.h"
 
 int main(int argc, char *argv[])
 {
-	if (argc != 2)
-		usage("test-svn-fe <file>");
-	if (svndump_init(argv[1]))
-		return 1;
-	svndump_read(NULL);
-	svndump_deinit();
-	svndump_reset();
-	return 0;
+	static const char test_svnfe_usage[] =
+		"test-svn-fe (<dumpfile> | [-d] <preimage> <delta> <len>)";
+	if (argc == 2) {
+		if (svndump_init(argv[1]))
+			return 1;
+		svndump_read(NULL);
+		svndump_deinit();
+		svndump_reset();
+		return 0;
+	}
+	if (argc == 5 && !strcmp(argv[1], "-d")) {
+		struct line_buffer preimage = LINE_BUFFER_INIT;
+		struct line_buffer delta = LINE_BUFFER_INIT;
+		struct sliding_view preimage_view = SLIDING_VIEW_INIT(&preimage);
+		if (buffer_init(&preimage, argv[2]))
+			die_errno("cannot open preimage");
+		if (buffer_init(&delta, argv[3]))
+			die_errno("cannot open delta");
+		if (svndiff0_apply(&delta, (off_t) strtoull(argv[4], NULL, 0),
+					&preimage_view, stdout))
+			return 1;
+		if (buffer_deinit(&preimage))
+			die_errno("cannot close preimage");
+		if (buffer_deinit(&delta))
+			die_errno("cannot close delta");
+		buffer_reset(&preimage);
+		strbuf_release(&preimage_view.buf);
+		buffer_reset(&delta);
+		return 0;
+	}
+	usage(test_svnfe_usage);
 }
diff --git a/vcs-svn/svndiff.c b/vcs-svn/svndiff.c
new file mode 100644
index 0000000000..591603669c
--- /dev/null
+++ b/vcs-svn/svndiff.c
@@ -0,0 +1,52 @@
+/*
+ * Licensed under a two-clause BSD-style license.
+ * See LICENSE for details.
+ */
+
+#include "git-compat-util.h"
+#include "line_buffer.h"
+#include "svndiff.h"
+
+/*
+ * svndiff0 applier
+ *
+ * See http://svn.apache.org/repos/asf/subversion/trunk/notes/svndiff.
+ *
+ * svndiff0 ::= 'SVN\0' window*
+ */
+
+static int error_short_read(struct line_buffer *input)
+{
+	if (buffer_ferror(input))
+		return error("error reading delta: %s", strerror(errno));
+	return error("invalid delta: unexpected end of file");
+}
+
+static int read_magic(struct line_buffer *in, off_t *len)
+{
+	static const char magic[] = {'S', 'V', 'N', '\0'};
+	struct strbuf sb = STRBUF_INIT;
+
+	if (*len < sizeof(magic) ||
+	    buffer_read_binary(in, &sb, sizeof(magic)) != sizeof(magic))
+		return error_short_read(in);
+
+	if (memcmp(sb.buf, magic, sizeof(magic)))
+		return error("invalid delta: unrecognized file type");
+
+	*len -= sizeof(magic);
+	strbuf_release(&sb);
+	return 0;
+}
+
+int svndiff0_apply(struct line_buffer *delta, off_t delta_len,
+			struct sliding_view *preimage, FILE *postimage)
+{
+	assert(delta && preimage && postimage);
+
+	if (read_magic(delta, &delta_len))
+		return -1;
+	if (delta_len)
+		return error("What do you think I am?  A delta applier?");
+	return 0;
+}
diff --git a/vcs-svn/svndiff.h b/vcs-svn/svndiff.h
new file mode 100644
index 0000000000..74eb464bab
--- /dev/null
+++ b/vcs-svn/svndiff.h
@@ -0,0 +1,10 @@
+#ifndef SVNDIFF_H_
+#define SVNDIFF_H_
+
+struct line_buffer;
+struct sliding_view;
+
+extern int svndiff0_apply(struct line_buffer *delta, off_t delta_len,
+		struct sliding_view *preimage, FILE *postimage);
+
+#endif