[PATCH/WIP 2/8] 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>
---
 git-compat-util.h |  1 +
 wrapper.c         | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/git-compat-util.h b/git-compat-util.h
index 9745962..914d450 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 971665a..d5ed780 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -329,6 +329,25 @@ 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)
+{
+	FILE *fp;
+
+	assert(path);
+	assert(mode);
+	fp = fopen(path, mode);
+	if (!fp) {
+		if (*mode == 'w' || *mode == 'a')
+			die_errno(_("could not open '%s' for writing"), path);
+		else
+			die_errno(_("could not open '%s' for reading"), path);
+	}
+	return fp;
+}
+
 FILE *xfdopen(int fd, const char *mode)
 {
 	FILE *stream = fdopen(fd, mode);
-- 
2.1.4