fd: Improve documentation of xwritev().

[paraslash.git] / fd.c

diff --git a/fd.c b/fd.c
index 800106e132b2bc21085f65803d70b6bad492f854..d0de66f41be6008c2d3be5afe6dae002fb06ceb5 100644 (file)
--- a/fd.c
+++ b/fd.c
@@ -37,26 +37,27 @@ int xrename(const char *oldpath, const char *newpath)
 }
 
 /**
- * Write an array of buffers to a file descriptor.
+ * Write an array of buffers, handling non-fatal errors.
  *
- * \param fd The file descriptor.
+ * \param fd The file descriptor to write to.
  * \param iov Pointer to one or more buffers.
  * \param iovcnt The number of buffers.
  *
- * EAGAIN/EWOULDBLOCK is not considered a fatal error condition. For example
- * DCCP CCID3 has a sending wait queue which fills up and is emptied
- * asynchronously. The EAGAIN case means that there is currently no space in
- * the wait queue, but this can change at any moment.
+ * EAGAIN, EWOULDBLOCK and EINTR are not considered error conditions. If a
+ * write operation fails with EAGAIN or EWOULDBLOCK, the number of bytes that
+ * have been written so far is returned. In the EINTR case the operation is
+ * retried. Short writes are handled by issuing a subsequent write operation
+ * for the remaining part.
  *
  * \return Negative on fatal errors, number of bytes written else.
  *
  * For blocking file descriptors, this function returns either the sum of all
- * buffer sizes, or the error code of the fatal error that caused the last
- * write call to fail.
+ * buffer sizes or a negative error code which indicates the fatal error that
+ * caused a write call to fail.
  *
- * For nonblocking file descriptors there is a third possibility: Any positive
- * return value less than the sum of the buffer sizes indicates that some bytes
- * have been written but the next write would block.
+ * For nonblocking file descriptors there is a third possibility: Any
+ * non-negative return value less than the sum of the buffer sizes indicates
+ * that a write operation returned EAGAIN/EWOULDBLOCK.
  *
  * \sa writev(2), \ref xwrite().
  */
@@ -126,14 +127,15 @@ int xwrite(int fd, const char *buf, size_t len)
 }
 
 /**
- * Write all data to a file descriptor.
+ * Write to a file descriptor, fail on short writes.
  *
  * \param fd The file descriptor.
- * \param buf The buffer to be sent.
- * \param len The length of \a buf.
+ * \param buf The buffer to be written.
+ * \param len The length of the buffer.
  *
- * This is like \ref xwrite() but returns \p -E_SHORT_WRITE if not
- * all data could be written.
+ * For blocking file descriptors this function behaves identical to \ref
+ * xwrite(). For non-blocking file descriptors it returns -E_SHORT_WRITE
+ * (rather than a value less than len) if not all data could be written.
  *
  * \return Number of bytes written on success, negative error code else.
  */
@@ -149,12 +151,20 @@ int write_all(int fd, const char *buf, size_t len)
 }
 
 /**
- * Write a buffer given by a format string.
+ * A fprintf-like function for raw file descriptors.
+ *
+ * This function creates a string buffer according to the given format and
+ * writes this buffer to a file descriptor.
  *
  * \param fd The file descriptor.
  * \param fmt A format string.
  *
+ * The difference to fprintf(3) is that the first argument is a file
+ * descriptor, not a FILE pointer. This function does not rely on stdio.
+ *
  * \return The return value of the underlying call to \ref write_all().
+ *
+ * \sa fprintf(3), \ref xvasprintf().
  */
 __printf_2_3 int write_va_buffer(int fd, const char *fmt, ...)
 {
@@ -269,7 +279,7 @@ int read_nonblock(int fd, void *buf, size_t sz, size_t *num_bytes)
 int read_pattern(int fd, const char *pattern, size_t bufsize)
 {
        size_t n, len;
-       char *buf = para_malloc(bufsize + 1);
+       char *buf = alloc(bufsize + 1);
        int ret = read_nonblock(fd, buf, bufsize, &n);
 
        buf[n] = '\0';