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Subject[RFC v2 03/14] kunit: test: add string_stream a std::stream like string builder
From
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.

Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
---
include/kunit/string-stream.h | 44 ++++++++++
kunit/Makefile | 2 +-
kunit/string-stream.c | 149 ++++++++++++++++++++++++++++++++++
3 files changed, 194 insertions(+), 1 deletion(-)
create mode 100644 include/kunit/string-stream.h
create mode 100644 kunit/string-stream.c

diff --git a/include/kunit/string-stream.h b/include/kunit/string-stream.h
new file mode 100644
index 0000000000000..933ed5740cf07
--- /dev/null
+++ b/include/kunit/string-stream.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * C++ stream style string builder used in KUnit for building messages.
+ *
+ * Copyright (C) 2018, Google LLC.
+ * Author: Brendan Higgins <brendanhiggins@google.com>
+ */
+
+#ifndef _KUNIT_STRING_STREAM_H
+#define _KUNIT_STRING_STREAM_H
+
+#include <linux/types.h>
+#include <linux/spinlock.h>
+#include <linux/kref.h>
+#include <stdarg.h>
+
+struct string_stream_fragment {
+ 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 kref refcount;
+ int (*add)(struct string_stream *this, const char *fmt, ...);
+ int (*vadd)(struct string_stream *this, const char *fmt, va_list args);
+ char *(*get_string)(struct string_stream *this);
+ void (*clear)(struct string_stream *this);
+ bool (*is_empty)(struct string_stream *this);
+};
+
+struct string_stream *new_string_stream(void);
+
+void destroy_string_stream(struct string_stream *stream);
+
+void string_stream_get(struct string_stream *stream);
+
+int string_stream_put(struct string_stream *stream);
+
+#endif /* _KUNIT_STRING_STREAM_H */
diff --git a/kunit/Makefile b/kunit/Makefile
index dd7a0299514b7..7fc613a9b383b 100644
--- a/kunit/Makefile
+++ b/kunit/Makefile
@@ -1 +1 @@
-obj-$(CONFIG_KUNIT) += test.o
+obj-$(CONFIG_KUNIT) += test.o string-stream.o
diff --git a/kunit/string-stream.c b/kunit/string-stream.c
new file mode 100644
index 0000000000000..1e7efa630cc35
--- /dev/null
+++ b/kunit/string-stream.c
@@ -0,0 +1,149 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * C++ stream style string builder used in KUnit for building messages.
+ *
+ * Copyright (C) 2018, Google LLC.
+ * Author: Brendan Higgins <brendanhiggins@google.com>
+ */
+
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <kunit/string-stream.h>
+
+static int string_stream_vadd(struct string_stream *this,
+ const char *fmt,
+ va_list args)
+{
+ struct string_stream_fragment *fragment;
+ int len;
+ va_list args_for_counting;
+ unsigned long flags;
+
+ /* Make a copy because `vsnprintf` could change it */
+ va_copy(args_for_counting, args);
+
+ /* Need space for null byte. */
+ len = vsnprintf(NULL, 0, fmt, args_for_counting) + 1;
+
+ va_end(args_for_counting);
+
+ fragment = kmalloc(sizeof(*fragment), GFP_KERNEL);
+ if (!fragment)
+ return -ENOMEM;
+
+ fragment->fragment = kmalloc(len, GFP_KERNEL);
+ if (!fragment->fragment) {
+ kfree(fragment);
+ return -ENOMEM;
+ }
+
+ len = vsnprintf(fragment->fragment, len, fmt, args);
+ spin_lock_irqsave(&this->lock, flags);
+ this->length += len;
+ list_add_tail(&fragment->node, &this->fragments);
+ spin_unlock_irqrestore(&this->lock, flags);
+ return 0;
+}
+
+static int string_stream_add(struct string_stream *this, const char *fmt, ...)
+{
+ va_list args;
+ int result;
+
+ va_start(args, fmt);
+ result = string_stream_vadd(this, fmt, args);
+ va_end(args);
+ return result;
+}
+
+static void string_stream_clear(struct string_stream *this)
+{
+ struct string_stream_fragment *fragment, *fragment_safe;
+ unsigned long flags;
+
+ spin_lock_irqsave(&this->lock, flags);
+ list_for_each_entry_safe(fragment,
+ fragment_safe,
+ &this->fragments,
+ node) {
+ list_del(&fragment->node);
+ kfree(fragment->fragment);
+ kfree(fragment);
+ }
+ this->length = 0;
+ spin_unlock_irqrestore(&this->lock, flags);
+}
+
+static char *string_stream_get_string(struct string_stream *this)
+{
+ struct string_stream_fragment *fragment;
+ size_t buf_len = this->length + 1; /* +1 for null byte. */
+ char *buf;
+ unsigned long flags;
+
+ buf = kzalloc(buf_len, GFP_KERNEL);
+ if (!buf)
+ return NULL;
+
+ spin_lock_irqsave(&this->lock, flags);
+ list_for_each_entry(fragment, &this->fragments, node)
+ strlcat(buf, fragment->fragment, buf_len);
+ spin_unlock_irqrestore(&this->lock, flags);
+
+ return buf;
+}
+
+static bool string_stream_is_empty(struct string_stream *this)
+{
+ bool is_empty;
+ unsigned long flags;
+
+ spin_lock_irqsave(&this->lock, flags);
+ is_empty = list_empty(&this->fragments);
+ spin_unlock_irqrestore(&this->lock, flags);
+
+ return is_empty;
+}
+
+void destroy_string_stream(struct string_stream *stream)
+{
+ stream->clear(stream);
+ kfree(stream);
+}
+
+static void string_stream_destroy(struct kref *kref)
+{
+ struct string_stream *stream = container_of(kref,
+ struct string_stream,
+ refcount);
+ destroy_string_stream(stream);
+}
+
+struct string_stream *new_string_stream(void)
+{
+ struct string_stream *stream = kzalloc(sizeof(*stream), GFP_KERNEL);
+
+ if (!stream)
+ return NULL;
+
+ INIT_LIST_HEAD(&stream->fragments);
+ spin_lock_init(&stream->lock);
+ kref_init(&stream->refcount);
+ stream->add = string_stream_add;
+ stream->vadd = string_stream_vadd;
+ stream->get_string = string_stream_get_string;
+ stream->clear = string_stream_clear;
+ stream->is_empty = string_stream_is_empty;
+ return stream;
+}
+
+void string_stream_get(struct string_stream *stream)
+{
+ kref_get(&stream->refcount);
+}
+
+int string_stream_put(struct string_stream *stream)
+{
+ return kref_put(&stream->refcount, &string_stream_destroy);
+}
+
--
2.19.1.568.g152ad8e336-goog
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