extract: Allow p11_save_write() to automatically calculate length

Also if automatically calculating length, then ignore input
that is NULL, as something that shouldn't be written out.

This allows easier chaining of optional output, such as comments.

https://bugs.freedesktop.org/show_bug.cgi?id=62029

5 files changed, 62 insertions, 4 deletions

diff --git a/tools/save.c b/tools/save.c
index 34caca1..1f886ad 100644
--- a/tools/save.c
+++ b/tools/save.c
@@ -66,7 +66,7 @@ struct _p11_save_dir {
 bool
 p11_save_write_and_finish (p11_save_file *file,
                            const void *data,
-                           size_t length)
+                           ssize_t length)
 {
 	bool ret;
 
@@ -128,7 +128,7 @@ p11_save_open_file (const char *path,
 bool
 p11_save_write (p11_save_file *file,
                 const void *data,
-                size_t length)
+                ssize_t length)
 {
 	const unsigned char *buf = data;
 	ssize_t written = 0;
@@ -137,6 +137,13 @@ p11_save_write (p11_save_file *file,
 	if (!file)
 		return false;
 
+	/* Automatically calculate length */
+	if (length < 0) {
+		if (!data)
+			return true;
+		length = strlen (data);
+	}
+
 	while (written < length) {
 		res = write (file->fd, buf + written, length - written);
 		if (res <= 0) {
diff --git a/tools/save.h b/tools/save.h
index bfa0990..f68d054 100644
--- a/tools/save.h
+++ b/tools/save.h
@@ -49,11 +49,11 @@ p11_save_file *  p11_save_open_file         (const char *path,
 
 bool             p11_save_write             (p11_save_file *file,
                                              const void *data,
-                                             size_t length);
+                                             ssize_t length);
 
 bool             p11_save_write_and_finish  (p11_save_file *file,
                                              const void *data,
-                                             size_t length);
+                                             ssize_t length);
 
 bool             p11_save_finish_file       (p11_save_file *file,
                                              bool commit);
diff --git a/tools/tests/files/empty-file b/tools/tests/files/empty-file
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/tools/tests/files/empty-file
diff --git a/tools/tests/files/simple-string b/tools/tests/files/simple-string
new file mode 100644
index 0000000..be13474
--- /dev/null
+++ b/tools/tests/files/simple-string
@@ -0,0 +1 @@
+The simple string is hairy
\ No newline at end of file
diff --git a/tools/tests/test-save.c b/tools/tests/test-save.c
index 41f4e08..88d1ecd 100644
--- a/tools/tests/test-save.c
+++ b/tools/tests/test-save.c
@@ -191,6 +191,54 @@ test_file_overwrite (CuTest *tc)
 }
 
 static void
+test_file_auto_empty (CuTest *tc)
+{
+	p11_save_file *file;
+	char *filename;
+	bool ret;
+
+	setup (tc);
+
+	if (asprintf (&filename, "%s/%s", test.directory, "extract-file") < 0)
+		CuFail (tc, "asprintf() failed");
+
+	file = p11_save_open_file (filename, 0);
+	CuAssertPtrNotNull (tc, file);
+
+	ret = p11_save_write_and_finish (file, NULL, -1);
+	CuAssertIntEquals (tc, true, ret);
+	free (filename);
+
+	test_check_file (tc, test.directory, "extract-file", SRCDIR "/files/empty-file");
+
+	teardown (tc);
+}
+
+static void
+test_file_auto_length (CuTest *tc)
+{
+	p11_save_file *file;
+	char *filename;
+	bool ret;
+
+	setup (tc);
+
+	if (asprintf (&filename, "%s/%s", test.directory, "extract-file") < 0)
+		CuFail (tc, "asprintf() failed");
+
+	file = p11_save_open_file (filename, 0);
+	CuAssertPtrNotNull (tc, file);
+
+	ret = p11_save_write_and_finish (file, "The simple string is hairy", -1);
+	CuAssertIntEquals (tc, true, ret);
+	free (filename);
+
+	test_check_file (tc, test.directory, "extract-file", SRCDIR "/files/simple-string");
+
+	teardown (tc);
+}
+
+static void
 test_write_with_null (CuTest *tc)
 {
 	bool ret;
@@ -496,6 +544,8 @@ main (void)
 	SUITE_ADD_TEST (suite, test_file_exists);
 	SUITE_ADD_TEST (suite, test_file_bad_directory);
 	SUITE_ADD_TEST (suite, test_file_overwrite);
+	SUITE_ADD_TEST (suite, test_file_auto_empty);
+	SUITE_ADD_TEST (suite, test_file_auto_length);
 	SUITE_ADD_TEST (suite, test_write_with_null);
 	SUITE_ADD_TEST (suite, test_write_and_finish_with_null);
 	SUITE_ADD_TEST (suite, test_file_abort);