add qemu_send_full and qemu_recv_full

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

osdep.c

@@ -166,3 +166,70 @@ int qemu_accept(int s, struct sockaddr *addr, socklen_t *addrlen)
 
     return ret;
 }
+
+/*
+ * A variant of send(2) which handles partial write.
+ *
+ * Return the number of bytes transferred, which is only
+ * smaller than `count' if there is an error.
+ *
+ * This function won't work with non-blocking fd's.
+ * Any of the possibilities with non-bloking fd's is bad:
+ *   - return a short write (then name is wrong)
+ *   - busy wait adding (errno == EAGAIN) to the loop
+ */
+ssize_t qemu_send_full(int fd, const void *buf, size_t count, int flags)
+{
+    ssize_t ret = 0;
+    ssize_t total = 0;
+
+    while (count) {
+        ret = send(fd, buf, count, flags);
+        if (ret < 0) {
+            if (errno == EINTR) {
+                continue;
+            }
+            break;
+        }
+
+        count -= ret;
+        buf += ret;
+        total += ret;
+    }
+
+    return total;
+}
+
+/*
+ * A variant of recv(2) which handles partial write.
+ *
+ * Return the number of bytes transferred, which is only
+ * smaller than `count' if there is an error.
+ *
+ * This function won't work with non-blocking fd's.
+ * Any of the possibilities with non-bloking fd's is bad:
+ *   - return a short write (then name is wrong)
+ *   - busy wait adding (errno == EAGAIN) to the loop
+ */
+ssize_t qemu_recv_full(int fd, void *buf, size_t count, int flags)
+{
+    ssize_t ret = 0;
+    ssize_t total = 0;
+
+    while (count) {
+        ret = qemu_recv(fd, buf, count, flags);
+        if (ret <= 0) {
+            if (ret < 0 && errno == EINTR) {
+                continue;
+            }
+            break;
+        }
+
+        count -= ret;
+        buf += ret;
+        total += ret;
+    }
+
+    return total;
+}
+

qemu-common.h

@@ -173,6 +173,10 @@ void *qemu_oom_check(void *ptr);
 int qemu_open(const char *name, int flags, ...);
 ssize_t qemu_write_full(int fd, const void *buf, size_t count)
     QEMU_WARN_UNUSED_RESULT;
+ssize_t qemu_send_full(int fd, const void *buf, size_t count, int flags)
+    QEMU_WARN_UNUSED_RESULT;
+ssize_t qemu_recv_full(int fd, const void *buf, size_t count, int flags)
+    QEMU_WARN_UNUSED_RESULT;
 void qemu_set_cloexec(int fd);
 
 #ifndef _WIN32