[PATCH/WIP v2 02/19] wrapper: implement xfopen()

[Paul Tan <pyokagan@gmail.com>]

A common usage pattern of fopen() is to check if it succeeded, and die()
if it failed:

	FILE *fp = fopen(path, "w");
	if (!fp)
		die_errno(_("could not open '%s' for writing"), path);

Implement a wrapper function xfopen() for 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>
---

Notes:
    v2
    
    * Removed the error message distinction between reading and writing.
    
    * Handle EINTR.

 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 95cc278..03ea3a2 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -723,6 +723,7 @@ 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);
 extern int xdup(int fd);
+extern FILE *xfopen(const char *path, const char *mode);
 extern FILE *xfdopen(int fd, const char *mode);
 extern int xmkstemp(char *template);
 extern int xmkstemp_mode(char *template, int mode);
diff --git a/wrapper.c b/wrapper.c
index 82658b3..9692460 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -336,6 +336,24 @@ int xdup(int fd)
 	return ret;
 }
 
+/**
+ * xfopen() is the same as fopen(), but it die()s if the fopen() fails.
+ */
+FILE *xfopen(const char *path, const char *mode)
+{
+	assert(path);
+	assert(mode);
+
+	for (;;) {
+		FILE *fp = fopen(path, mode);
+		if (fp)
+			return fp;
+		if (errno == EINTR)
+			continue;
+		die_errno(_("could not open '%s'"), path);
+	}
+}
+
 FILE *xfdopen(int fd, const char *mode)
 {
 	FILE *stream = fdopen(fd, mode);
-- 
2.1.4