wrapper: implement xopen()
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. Helped-by: Torsten Bögershausen <tboegi@web.de> Helped-by: Jeff King <peff@peff.net> Helped-by: Johannes Schindelin <johannes.schindelin@gmx.de> Helped-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Paul Tan <pyokagan@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Paul Tan committed
Aug 4, 2015 at 21:51 UTC
3ff53df7b4cbc331d302181d2d6644f4cb860a52
2 files changed
+36
git-compat-util.h
+1
@@ -717,6 +717,7 @@ extern void *xrealloc(void *ptr, size_t size);
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extern void *xcalloc(size_t nmemb, size_t size);
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extern void *xmmap(void *start, size_t length, int prot, int flags, int fd, off_t offset);
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extern void *xmmap_gently(void *start, size_t length, int prot, int flags, int fd, off_t offset);
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+extern int xopen(const char *path, int flags, ...);
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extern ssize_t xread(int fd, void *buf, size_t len);
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extern ssize_t xwrite(int fd, const void *buf, size_t len);
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extern ssize_t xpread(int fd, void *buf, size_t len, off_t offset);
wrapper.c
+35
@@ -189,6 +189,41 @@ void *xcalloc(size_t nmemb, size_t size)
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# endif
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#endif
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+/**
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+ * xopen() is the same as open(), but it die()s if the open() fails.
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+ */
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+int xopen(const char *path, int oflag, ...)
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+{
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+ mode_t mode = 0;
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+ va_list ap;
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+
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+ /*
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+ * va_arg() will have undefined behavior if the specified type is not
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+ * compatible with the argument type. Since integers are promoted to
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+ * ints, we fetch the next argument as an int, and then cast it to a
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+ * mode_t to avoid undefined behavior.
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+ */
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+ va_start(ap, oflag);
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+ if (oflag & O_CREAT)
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+ mode = va_arg(ap, int);
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+ va_end(ap);
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+
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+ for (;;) {
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+ int fd = open(path, oflag, mode);
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+ if (fd >= 0)
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+ return fd;
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+ if (errno == EINTR)
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+ continue;
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+
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+ if ((oflag & O_RDWR) == O_RDWR)
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+ die_errno(_("could not open '%s' for reading and writing"), path);
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+ else if ((oflag & O_WRONLY) == O_WRONLY)
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+ die_errno(_("could not open '%s' for writing"), path);
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+ else
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+ die_errno(_("could not open '%s' for reading"), path);
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+ }
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+}
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+
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/*
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* xread() is the same a read(), but it automatically restarts read()
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* operations with a recoverable error (EAGAIN and EINTR). xread()