Clean up io_input() for the "no input available" case

Return zero when no input is available, regardless of parameter
waitforinput.  Before, it returned -1 with errno set to EAGAIN or
EWOULDBLOCK when not waiting for input.  Current callers all wait.

Drop errno from the function's contract, for consistency with
io_output().

diff --git a/src/lib/empthread/io.c b/src/lib/empthread/io.c
index 47a2b1093e4de2a9cdb188131270077a7e4e276a..0e65c86ed972da2c0d49d72fcbd58bcc54818eb4 100644 (file)
--- a/src/lib/empthread/io.c
+++ b/src/lib/empthread/io.c
@@ -128,9 +128,8 @@ io_close(struct iop *iop)
 
 /*
  * Return number of bytes read on success, zero on timeout, early
- * wakeup or EOF, -1 on error, with errno set appropriately.  In
- * particular, return -1 with errno set to EAGAIN or EWOULDBLOCK when
- * no data is available for non-blocking input (WAITFORINPUT false).
+ * wakeup or EOF, -1 on error.  In particular, return 0 when no data
+ * is available for non-blocking input (WAITFORINPUT false).
  * Use io_eof() to distinguish timeout and early wakeup from EOF.
  */
 int
@@ -140,14 +139,10 @@ io_input(struct iop *iop, int waitforinput)
     int cc;
     int res;
 
-    if ((iop->flags & IO_READ) == 0) {
-       errno = EBADF;
+    if ((iop->flags & IO_READ) == 0)
        return -1;
-    }
-    if (iop->flags & IO_ERROR) {
-       errno = EBADF;
+    if (iop->flags & IO_ERROR)
        return -1;
-    }
     if (iop->flags & IO_EOF)
        return 0;
 
@@ -164,9 +159,9 @@ io_input(struct iop *iop, int waitforinput)
     /* Do the actual read. */
     cc = read(iop->fd, buf, sizeof(buf));
     if (cc < 0) {
-       if (errno != EAGAIN && errno != EWOULDBLOCK)
-           /* Some form of file error occurred... */
-           iop->flags |= IO_ERROR;
+       if (errno == EAGAIN || errno == EWOULDBLOCK)
+           return 0;
+       iop->flags |= IO_ERROR;
        return -1;
     }