[v4,03/18] kunit: test: add string_stream a std::stream likestring builder
diff mbox series

Message ID 20190514221711.248228-4-brendanhiggins@google.com
State Not Applicable
Headers show
Series
  • kunit: introduce KUnit, the Linux kernel unittesting framework
Related show

Commit Message

Brendan Higgins May 14, 2019, 10:16 p.m. UTC
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>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
---
 include/kunit/string-stream.h |  51 ++++++++++++
 kunit/Makefile                |   3 +-
 kunit/string-stream.c         | 143 ++++++++++++++++++++++++++++++++++
 3 files changed, 196 insertions(+), 1 deletion(-)
 create mode 100644 include/kunit/string-stream.h
 create mode 100644 kunit/string-stream.c

Comments

Stephen Boyd May 17, 2019, 5:42 p.m. UTC | #1
Quoting Brendan Higgins (2019-05-14 15:16:56)
> 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>
> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Reviewed-by: Logan Gunthorpe <logang@deltatee.com>

Is there any reason why we can't use the seqfile API for this? These
both share a similar goal, formatting strings into a buffer to be read
later. Maybe some new APIs would be needed to extract the buffer
differently, but I hope we could share the code.

If it can't be used, can you please add the reasoning to the commit text
here?
Brendan Higgins June 5, 2019, 12:19 a.m. UTC | #2
On Fri, May 17, 2019 at 10:43 AM Stephen Boyd <sboyd@kernel.org> wrote:
>
> Quoting Brendan Higgins (2019-05-14 15:16:56)
> > 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>
> > Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
>
> Is there any reason why we can't use the seqfile API for this? These
> both share a similar goal, formatting strings into a buffer to be read
> later. Maybe some new APIs would be needed to extract the buffer
> differently, but I hope we could share the code.

I can see why you are asking. It seems as though they are trying to do
*similar* things, and it seems possible that we might be able to
extract some common functionality out of seq_file that could replace
this; however, it looks like it would be require a significant
refactoring of seq_file to separate out the file system specific bits
from the more general stringbuilder functionality.

In my opinion, a refactoring like this makes no sense in this
patchset; it probably belongs in its own patchset (preferably as a
follow on). I also am not sure if the FS people would appreciate
indirection that serves them no benefit, but I can ask if you like.

> If it can't be used, can you please add the reasoning to the commit text
> here?

Will do.

Thanks!

Patch
diff mbox series

diff --git a/include/kunit/string-stream.h b/include/kunit/string-stream.h
new file mode 100644
index 0000000000000..567a4629406da
--- /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/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;
+};
+
+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);
+
+int string_stream_add(struct string_stream *this, const char *fmt, ...);
+
+int string_stream_vadd(struct string_stream *this,
+		       const char *fmt,
+		       va_list args);
+
+char *string_stream_get_string(struct string_stream *this);
+
+void string_stream_clear(struct string_stream *this);
+
+bool string_stream_is_empty(struct string_stream *this);
+
+#endif /* _KUNIT_STRING_STREAM_H */
diff --git a/kunit/Makefile b/kunit/Makefile
index 5efdc4dea2c08..275b565a0e81f 100644
--- a/kunit/Makefile
+++ b/kunit/Makefile
@@ -1 +1,2 @@ 
-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..d4e4252dc10b8
--- /dev/null
+++ b/kunit/string-stream.c
@@ -0,0 +1,143 @@ 
+// 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>
+ */
+
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <kunit/string-stream.h>
+
+int string_stream_vadd(struct string_stream *this,
+		       const char *fmt,
+		       va_list args)
+{
+	struct string_stream_fragment *frag_container;
+	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);
+
+	frag_container = kmalloc(sizeof(*frag_container), GFP_KERNEL);
+	if (!frag_container)
+		return -ENOMEM;
+
+	frag_container->fragment = kmalloc(len, GFP_KERNEL);
+	if (!frag_container->fragment) {
+		kfree(frag_container);
+		return -ENOMEM;
+	}
+
+	len = vsnprintf(frag_container->fragment, len, fmt, args);
+	spin_lock_irqsave(&this->lock, flags);
+	this->length += len;
+	list_add_tail(&frag_container->node, &this->fragments);
+	spin_unlock_irqrestore(&this->lock, flags);
+	return 0;
+}
+
+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;
+}
+
+void string_stream_clear(struct string_stream *this)
+{
+	struct string_stream_fragment *frag_container, *frag_container_safe;
+	unsigned long flags;
+
+	spin_lock_irqsave(&this->lock, flags);
+	list_for_each_entry_safe(frag_container,
+				 frag_container_safe,
+				 &this->fragments,
+				 node) {
+		list_del(&frag_container->node);
+		kfree(frag_container->fragment);
+		kfree(frag_container);
+	}
+	this->length = 0;
+	spin_unlock_irqrestore(&this->lock, flags);
+}
+
+char *string_stream_get_string(struct string_stream *this)
+{
+	struct string_stream_fragment *frag_container;
+	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(frag_container, &this->fragments, node)
+		strlcat(buf, frag_container->fragment, buf_len);
+	spin_unlock_irqrestore(&this->lock, flags);
+
+	return buf;
+}
+
+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)
+{
+	string_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);
+	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);
+}