From: Andre Noll <maan@systemlinux.org>
Date: Sun, 11 Dec 2011 20:12:13 +0000 (+0100)
Subject: fd: Let write_all() return an error on short writes.
X-Git-Tag: v0.4.10~11^2~8
X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=commitdiff_plain;h=864024c003d678dbb436cdfc1148b201e4e47018;ds=sidebyside

fd: Let write_all() return an error on short writes.

Short writes are often ignored because most callers of write_all()
do not check the return value. Rather than fixing all callers, this
patch teaches write_all() to detect short writes and return the new
E_SHORT_WRITE error code in this case.

Currently write_all() is a wrapper for write(), similar to
write_nonblock() but lacking the safety checks of the latter. To get
these safety checks, write_all() is changed to call write_nonblock().

Unfortunately, this involves some code movement.
---

diff --git a/error.h b/error.h
index 63d4d5db..f7216ea3 100644
--- a/error.h
+++ b/error.h
@@ -441,6 +441,7 @@ extern const char **para_errlist[];
 	PARA_ERROR(FGETS, "fgets error"), \
 	PARA_ERROR(EOF, "end of file"), \
 	PARA_ERROR(READ_PATTERN, "did not read expected pattern"), \
+	PARA_ERROR(SHORT_WRITE, "unexpected short write"), \
 
 
 #define ALSA_WRITE_ERRORS \
diff --git a/fd.c b/fd.c
index 830b15da..01c7ed8e 100644
--- a/fd.c
+++ b/fd.c
@@ -18,49 +18,6 @@
 #include "string.h"
 #include "fd.h"
 
-/**
- * Write a buffer to a file descriptor, re-write on short writes.
- *
- * \param fd The file descriptor.
- * \param buf The buffer to be sent.
- * \param len The length of \a buf.
- *
- * \return Standard.
- */
-int write_all(int fd, const char *buf, size_t len)
-{
-	size_t total = len;
-
-	assert(total);
-	len = 0;
-	while (len < total) {
-		int ret = write(fd, buf + len, total - len);
-		if (ret == -1)
-			return -ERRNO_TO_PARA_ERROR(errno);
-		len += ret;
-	}
-	return len;
-}
-
-/**
- * Send a buffer given by a format string.
- *
- * \param fd The file descriptor.
- * \param fmt A format string.
- *
- * \return Standard.
- */
-__printf_2_3 int write_va_buffer(int fd, const char *fmt, ...)
-{
-	char *msg;
-	int ret;
-
-	PARA_VSPRINTF(fmt, msg);
-	ret = write_buffer(fd, msg);
-	free(msg);
-	return ret;
-}
-
 /**
  * Write a buffer to a file descriptor, re-writing on short writes.
  *
@@ -109,6 +66,48 @@ int write_nonblock(int fd, const char *buf, size_t len)
 	return written;
 }
 
+/**
+ * Write all data to a file descriptor.
+ *
+ * \param fd The file descriptor.
+ * \param buf The buffer to be sent.
+ * \param len The length of \a buf.
+ *
+ * This is like \ref write_nonblock() but returns \p -E_SHORT_WRITE if not
+ * all data could be written.
+ *
+ * \return Number of bytes written on success, negative error code else.
+ */
+int write_all(int fd, const char *buf, size_t len)
+{
+	int ret = write_nonblock(fd, buf, len);
+
+	if (ret < 0)
+		return ret;
+	if (ret != len)
+		return -E_SHORT_WRITE;
+	return ret;
+}
+
+/**
+ * Write a buffer given by a format string.
+ *
+ * \param fd The file descriptor.
+ * \param fmt A format string.
+ *
+ * \return The return value of the underlying call to \ref write_all().
+ */
+__printf_2_3 int write_va_buffer(int fd, const char *fmt, ...)
+{
+	char *msg;
+	int ret;
+
+	PARA_VSPRINTF(fmt, msg);
+	ret = write_buffer(fd, msg);
+	free(msg);
+	return ret;
+}
+
 /**
  * Read from a non-blocking file descriptor into multiple buffers.
  *