[PATCH/WIP 1/8] wrapper: implement xopen()

[Paul Tan <pyokagan@gmail.com>]

A common usage pattern of open() is to check if it was successful, and
die() if it was not:

	int fd = open(path, O_WRONLY | O_CREAT, 0777);
	if (fd < 0)
		die_errno(_("Could not open '%s' for writing."), path);

Implement a wrapper function xopen() that does the above so that we can
save a few lines of code, and make the die() messages consistent.

Signed-off-by: Paul Tan <pyokagan@gmail.com>
---
 git-compat-util.h |  1 +
 wrapper.c         | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/git-compat-util.h b/git-compat-util.h
index 17584ad..9745962 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -718,6 +718,7 @@ extern char *xstrndup(const char *str, size_t len);
 extern void *xrealloc(void *ptr, size_t size);
 extern void *xcalloc(size_t nmemb, size_t size);
 extern void *xmmap(void *start, size_t length, int prot, int flags, int fd, off_t offset);
+extern int xopen(const char *path, int flags, mode_t mode);
 extern ssize_t xread(int fd, void *buf, size_t len);
 extern ssize_t xwrite(int fd, const void *buf, size_t len);
 extern ssize_t xpread(int fd, void *buf, size_t len, off_t offset);
diff --git a/wrapper.c b/wrapper.c
index c1a663f..971665a 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -189,6 +189,24 @@ void *xcalloc(size_t nmemb, size_t size)
 # endif
 #endif
 
+/**
+ * xopen() is the same as open(), but it die()s if the open() fails.
+ */
+int xopen(const char *path, int flags, mode_t mode)
+{
+	int fd;
+
+	assert(path);
+	fd = open(path, flags, mode);
+	if (fd < 0) {
+		if ((flags & O_WRONLY) || (flags & O_RDWR))
+			die_errno(_("could not open '%s' for writing"), path);
+		else
+			die_errno(_("could not open '%s' for reading"), path);
+	}
+	return fd;
+}
+
 /*
  * xread() is the same a read(), but it automatically restarts read()
  * operations with a recoverable error (EAGAIN and EINTR). xread()
-- 
2.1.4