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

[paraslash.git] / fd.c

diff --git a/fd.c b/fd.c
index a0969e3e651a92983682f29f1ca375b214a6447a..01c7ed8e83552734b1077d444fc055f89f7695c9 100644 (file)
--- a/fd.c
+++ b/fd.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2006-2011 Andre Noll <maan@systemlinux.org>
+ * Copyright (C) 2006-2012 Andre Noll <maan@systemlinux.org>
  *
  * Licensed under the GPL v2. For licencing details see COPYING.
  */
@@ -19,60 +19,93 @@
 #include "fd.h"
 
 /**
- * Write a buffer to a file descriptor, re-write on short writes.
+ * Write a buffer to a file descriptor, re-writing on short writes.
  *
  * \param fd The file descriptor.
- * \param buf The buffer to be sent.
- * \param len The length of \a buf.
- *
- * \return Standard. In any case, the number of bytes that have been written is
- * stored in \a len.
+ * \param buf The buffer to write.
+ * \param len The number of bytes to write.
+ *
+ * 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.
+ *
+ * \return Negative on fatal errors, number of bytes written else. For blocking
+ * file descriptors this function returns either \a len or the error code of
+ * the fatal error that caused the last write call to fail. For nonblocking
+ * file descriptors there is a third possibility: A positive return value < \a
+ * len indicates that some bytes have been written but the next write would
+ * block.
  */
-int write_all(int fd, const char *buf, size_t *len)
+int write_nonblock(int fd, const char *buf, size_t len)
 {
-       size_t total = *len;
+       size_t written = 0;
 
-       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;
+       while (written < len) {
+               ssize_t ret = write(fd, buf + written, len - written);
+               if (ret >= 0) {
+                       written += ret;
+                       continue;
+               }
+               if (errno == EINTR)
+                       /*
+                        * The write() call was interrupted by a signal before
+                        * any data was written. Try again.
+                        */
+                       continue;
+               if (errno == EAGAIN || errno == EWOULDBLOCK)
+                       /*
+                        * We don't consider this an error. Note that POSIX
+                        * allows either error to be returned, and does not
+                        * require these constants to have the same value.
+                        */
+                       return written;
+               /* fatal error */
+               return -ERRNO_TO_PARA_ERROR(errno);
        }
-       return 1;
+       return written;
 }
 
 /**
- * Write a buffer to a non-blocking file descriptor.
+ * Write all data to a file descriptor.
  *
  * \param fd The file descriptor.
- * \param buf the buffer to write.
- * \param len the number of bytes of \a buf.
+ * \param buf The buffer to be sent.
+ * \param len The length of \a buf.
  *
- * EAGAIN is not considered an error condition.  For example 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.
+ * This is like \ref write_nonblock() but returns \p -E_SHORT_WRITE if not
+ * all data could be written.
  *
- * \return Negative on errors, number of bytes written else.
+ * \return Number of bytes written on success, negative error code else.
  */
-int write_nonblock(int fd, const char *buf, size_t len)
+int write_all(int fd, const char *buf, size_t len)
 {
-       size_t written = 0;
-       int ret = 0;
+       int ret = write_nonblock(fd, buf, len);
 
-       while (written < len) {
-               size_t num = len - written;
+       if (ret < 0)
+               return ret;
+       if (ret != len)
+               return -E_SHORT_WRITE;
+       return ret;
+}
 
-               ret = write(fd, buf + written, num);
-               if (ret < 0 && errno == EAGAIN)
-                       return written;
-               if (ret < 0)
-                       return -ERRNO_TO_PARA_ERROR(errno);
-               written += ret;
-       }
-       return written;
+/**
+ * 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;
 }
 
 /**
@@ -446,7 +479,7 @@ int para_chdir(const char *path)
  * \sa getcwd(3).
  *
  */
-int para_opendir(const char *dirname, DIR **dir, int *cwd)
+static int para_opendir(const char *dirname, DIR **dir, int *cwd)
 {
        int ret;
 
@@ -480,7 +513,7 @@ close_cwd:
  *
  * \return Standard.
  */
-int para_fchdir(int fd)
+static int para_fchdir(int fd)
 {
        if (fchdir(fd) < 0)
                return -ERRNO_TO_PARA_ERROR(errno);
@@ -563,6 +596,9 @@ out:
 int para_munmap(void *start, size_t length)
 {
        int err;
+
+       if (!start)
+               return 0;
        if (munmap(start, length) >= 0)
                return 1;
        err = errno;