[PATCH] use strbuf_addbuf() for appending a strbuf to another

Use strbuf_addbuf() where possible; it's shorter and more efficient.

Signed-off-by: Rene Scharfe <redacted>
---
 dir.c       | 2 +-
 path.c      | 2 +-
 wt-status.c | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/dir.c b/dir.c
index 6172b34..0ea235f 100644
--- a/dir.c
+++ b/dir.c

@@ -2364,7 +2364,7 @@ void write_untracked_extension(struct strbuf *out, struct untracked_cache *untra
 
 	varint_len = encode_varint(untracked->ident.len, varbuf);
 	strbuf_add(out, varbuf, varint_len);
-	strbuf_add(out, untracked->ident.buf, untracked->ident.len);
+	strbuf_addbuf(out, &untracked->ident);
 
 	strbuf_add(out, ouc, ouc_size(len));
 	free(ouc);

diff --git a/path.c b/path.c
index 259aeed..17551c4 100644
--- a/path.c
+++ b/path.c

@@ -483,7 +483,7 @@ static void do_submodule_path(struct strbuf *buf, const char *path,
 		strbuf_addstr(buf, git_dir);
 	}
 	strbuf_addch(buf, '/');
-	strbuf_addstr(&git_submodule_dir, buf->buf);
+	strbuf_addbuf(&git_submodule_dir, buf);
 
 	strbuf_vaddf(buf, fmt, args);
 

diff --git a/wt-status.c b/wt-status.c
index c19b52c..dbdb543 100644
--- a/wt-status.c
+++ b/wt-status.c

@@ -1062,7 +1062,7 @@ static void abbrev_sha1_in_line(struct strbuf *line)
 			strbuf_addf(split[1], "%s ", abbrev);
 			strbuf_reset(line);
 			for (i = 0; split[i]; i++)
-				strbuf_addf(line, "%s", split[i]->buf);
+				strbuf_addbuf(line, split[i]);
 		}
 	}
 	strbuf_list_free(split);

-- 
2.9.2

On Tue, Jul 19, 2016 at 08:36:29PM +0200, René Scharfe wrote:

Use strbuf_addbuf() where possible; it's shorter and more efficient.

After seeing "efficient", I was momentarily surprised by the first hunk:

This is actually slightly _less_ efficient, because we already are using
the precomputed len, and the new code will call an extra strbuf_grow()
to cover the case where the two arguments are the same.  See 81d2cae
(strbuf_addbuf(): allow passing the same buf to dst and src,
2010-01-12).

But it almost certainly doesn't matter, and it definitely _is_ an
improvement for the other "addstr" cases, which are doing an unncessary
strlen().

And anyway the readability improvement trumps all of that in my mind. So
I think overall it is a nice cleanup; I'm mostly just commenting for the
sake of other reviewers.

-Peff

Am 20.07.2016 um 15:20 schrieb Jeff King:

On Tue, Jul 19, 2016 at 08:36:29PM +0200, René Scharfe wrote:

quoted

Use strbuf_addbuf() where possible; it's shorter and more efficient.

After seeing "efficient", I was momentarily surprised by the first hunk:

quoted

diff --git a/dir.c b/dir.c
index 6172b34..0ea235f 100644
--- a/dir.c
+++ b/dir.c

@@ -2364,7 +2364,7 @@ void write_untracked_extension(struct strbuf *out, struct untracked_cache *untra
  
  	varint_len = encode_varint(untracked->ident.len, varbuf);
  	strbuf_add(out, varbuf, varint_len);
-	strbuf_add(out, untracked->ident.buf, untracked->ident.len);
+	strbuf_addbuf(out, &untracked->ident);

This is actually slightly _less_ efficient, because we already are using
the precomputed len, and the new code will call an extra strbuf_grow()
to cover the case where the two arguments are the same.  See 81d2cae
(strbuf_addbuf(): allow passing the same buf to dst and src,
2010-01-12).

Ah, I wasn't aware of that.  Calling strbuf_grow() twice shouldn't be
thaaat bad.  However, I wonder where we duplicate strbufs, or why we
would ever want to do so.  Anyway, here's a patch for that:

-- >8 --
Subject: strbuf: avoid calling strbuf_grow() twice in strbuf_addbuf()

Implement strbuf_addbuf() as a normal function in order to avoid calling
strbuf_grow() twice, with the second callinside strbud_add() being a
no-op.  This is slightly faster and also reduces the text size a bit.

Signed-off-by: Rene Scharfe <redacted>
---
 strbuf.c | 7 +++++++
 strbuf.h | 6 +-----
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/strbuf.c b/strbuf.c
index 1ba600b..f3bd571 100644
--- a/strbuf.c
+++ b/strbuf.c

@@ -197,6 +197,13 @@ void strbuf_add(struct strbuf *sb, const void *data, size_t len)
 	strbuf_setlen(sb, sb->len + len);
 }
 
+void strbuf_addbuf(struct strbuf *sb, const struct strbuf *sb2)
+{
+	strbuf_grow(sb, sb2->len);
+	memcpy(sb->buf + sb->len, sb2->buf, sb2->len);
+	strbuf_setlen(sb, sb->len + sb2->len);
+}
+
 void strbuf_adddup(struct strbuf *sb, size_t pos, size_t len)
 {
 	strbuf_grow(sb, len);

diff --git a/strbuf.h b/strbuf.h
index 83c5c98..ba8d5f1 100644
--- a/strbuf.h
+++ b/strbuf.h

@@ -263,11 +263,7 @@ static inline void strbuf_addstr(struct strbuf *sb, const char *s)
 /**
  * Copy the contents of another buffer at the end of the current one.
  */
-static inline void strbuf_addbuf(struct strbuf *sb, const struct strbuf *sb2)
-{
-	strbuf_grow(sb, sb2->len);
-	strbuf_add(sb, sb2->buf, sb2->len);
-}
+extern void strbuf_addbuf(struct strbuf *sb, const struct strbuf *sb2);
 
 /**
  * Copy part of the buffer from a given position till a given length to the

-- 
2.9.2

On Thu, Jul 21, 2016 at 06:46:44PM +0200, René Scharfe wrote:

quoted

quoted

-	strbuf_add(out, untracked->ident.buf, untracked->ident.len);
+	strbuf_addbuf(out, &untracked->ident);

This is actually slightly _less_ efficient, because we already are using
the precomputed len, and the new code will call an extra strbuf_grow()
to cover the case where the two arguments are the same.  See 81d2cae
(strbuf_addbuf(): allow passing the same buf to dst and src,
2010-01-12).

Ah, I wasn't aware of that.  Calling strbuf_grow() twice shouldn't be
thaaat bad.  However, I wonder where we duplicate strbufs, or why we
would ever want to do so.  Anyway, here's a patch for that:

I don't think we do. Going back to the original discussion:

  http://thread.gmane.org/gmane.comp.version-control.git/136141/focus=136774

it was mostly just "hey, this would fail really confusingly if we ever
did, so let's make it safe".

The second strbuf_grow() is by definition a noop (which is why 81d2cae
works at all), but we do pay the size-computation cost.

-- >8 --
Subject: strbuf: avoid calling strbuf_grow() twice in strbuf_addbuf()

Implement strbuf_addbuf() as a normal function in order to avoid calling
strbuf_grow() twice, with the second callinside strbud_add() being a
no-op.  This is slightly faster and also reduces the text size a bit.

Seems reasonable.  IMHO the main advantage is that one does not have to
reason about the double strbuf_grow() (i.e., that the strbuf_add() is
safe because we know its grow is a noop).

-Peff