[PATCH 1/3] strbuf: add strbuf_add_cwd()

["René Scharfe" <l.s.r@web.de>]

Add strbuf_add_cwd(), which adds the current working directory to a
strbuf.  Because it doesn't use a fixed-size buffer it supports
arbitrarily long paths, as long as the platform's getcwd() does as
well.  At least on Linux and FreeBSD it handles paths longer than
PATH_MAX just fine.

Suggested-by: Karsten Blees <karsten.blees@gmail.com>
Signed-off-by: Rene Scharfe <l.s.r@web.de>
---
 Documentation/technical/api-strbuf.txt |  4 ++++
 strbuf.c                               | 22 ++++++++++++++++++++++
 strbuf.h                               |  1 +
 3 files changed, 27 insertions(+)

diff --git a/Documentation/technical/api-strbuf.txt b/Documentation/technical/api-strbuf.txt
index f9c06a7..b96b78c 100644
--- a/Documentation/technical/api-strbuf.txt
+++ b/Documentation/technical/api-strbuf.txt
@@ -257,6 +257,10 @@ which can be used by the programmer of the callback as she sees fit.
 
 	Add a formatted string to the buffer.
 
+`strbuf_add_cwd`::
+
+	Add the current working directory to the buffer.
+
 `strbuf_commented_addf`::
 
 	Add a formatted string prepended by a comment character and a
diff --git a/strbuf.c b/strbuf.c
index 33018d8..4e44773 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -406,6 +406,28 @@ int strbuf_readlink(struct strbuf *sb, const char *path, size_t hint)
 	return -1;
 }
 
+int strbuf_add_cwd(struct strbuf *sb)
+{
+	size_t oldalloc = sb->alloc;
+	size_t guessed_len = 32;
+
+	for (;; guessed_len *= 2) {
+		char *cwd;
+
+		strbuf_grow(sb, guessed_len);
+		cwd = getcwd(sb->buf + sb->len, sb->alloc - sb->len);
+		if (cwd) {
+			strbuf_setlen(sb, sb->len + strlen(cwd));
+			return 0;
+		}
+		if (errno != ERANGE)
+			break;
+	}
+	if (oldalloc == 0)
+		strbuf_release(sb);
+	return -1;
+}
+
 int strbuf_getwholeline(struct strbuf *sb, FILE *fp, int term)
 {
 	int ch;
diff --git a/strbuf.h b/strbuf.h
index a7c0192..ba95cd6 100644
--- a/strbuf.h
+++ b/strbuf.h
@@ -174,6 +174,7 @@ extern size_t strbuf_fread(struct strbuf *, size_t, FILE *);
 extern ssize_t strbuf_read(struct strbuf *, int fd, size_t hint);
 extern int strbuf_read_file(struct strbuf *sb, const char *path, size_t hint);
 extern int strbuf_readlink(struct strbuf *sb, const char *path, size_t hint);
+extern int strbuf_add_cwd(struct strbuf *sb);
 
 extern int strbuf_getwholeline(struct strbuf *, FILE *, int);
 extern int strbuf_getline(struct strbuf *, FILE *, int);
-- 
2.0.2