kunit: test: add string_stream a std::stream like string builder

A number of test features need to do pretty complicated string printing
where it may not be possible to rely on a single preallocated string
with parameters.

So provide a library for constructing the string as you go similar to
C++'s std::string. string_stream is really just a string builder,
nothing more.

Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

1 files changed, 51 insertions, 0 deletions

diff --git a/include/kunit/string-stream.h b/include/kunit/string-stream.h
new file mode 100644
index 000000000000..fe98a00b75a9
--- /dev/null
+++ b/include/kunit/string-stream.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * C++ stream style string builder used in KUnit for building messages.
+ *
+ * Copyright (C) 2019, Google LLC.
+ * Author: Brendan Higgins <brendanhiggins@google.com>
+ */
+
+#ifndef _KUNIT_STRING_STREAM_H
+#define _KUNIT_STRING_STREAM_H
+
+#include <linux/spinlock.h>
+#include <linux/types.h>
+#include <stdarg.h>
+
+struct string_stream_fragment {
+	struct kunit *test;
+	struct list_head node;
+	char *fragment;
+};
+
+struct string_stream {
+	size_t length;
+	struct list_head fragments;
+	/* length and fragments are protected by this lock */
+	spinlock_t lock;
+	struct kunit *test;
+	gfp_t gfp;
+};
+
+struct kunit;
+
+struct string_stream *alloc_string_stream(struct kunit *test, gfp_t gfp);
+
+int __printf(2, 3) string_stream_add(struct string_stream *stream,
+				     const char *fmt, ...);
+
+int string_stream_vadd(struct string_stream *stream,
+		       const char *fmt,
+		       va_list args);
+
+char *string_stream_get_string(struct string_stream *stream);
+
+int string_stream_append(struct string_stream *stream,
+			 struct string_stream *other);
+
+bool string_stream_is_empty(struct string_stream *stream);
+
+int string_stream_destroy(struct string_stream *stream);
+
+#endif /* _KUNIT_STRING_STREAM_H */