qga: Support enum names in guest-file-seek

Magic constants are a pain to use, especially when we run the
risk that our choice of '1' for QGA_SEEK_CUR might differ from
the host or guest's choice of SEEK_CUR.  Better is to use an
enum value, via a qapi alternate type for back-compatibility.

With this,
 {"command":"guest-file-seek", "arguments":{"handle":1,
  "offset":0, "whence":"cur"}}
becomes a synonym for the older
 {"command":"guest-file-seek", "arguments":{"handle":1,
  "offset":0, "whence":1}}

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/qga/commands.c b/qga/commands.c
index 5b56786ef6..e091ee1af1 100644
--- a/qga/commands.c
+++ b/qga/commands.c
@@ -473,3 +473,24 @@ done:
 
     return ge;
 }
+
+/* Convert GuestFileWhence (either a raw integer or an enum value) into
+ * the guest's SEEK_ constants.  */
+int ga_parse_whence(GuestFileWhence *whence, Error **errp)
+{
+    /* Exploit the fact that we picked values to match QGA_SEEK_*. */
+    if (whence->type == QTYPE_QSTRING) {
+        whence->type = QTYPE_QINT;
+        whence->u.value = whence->u.name;
+    }
+    switch (whence->u.value) {
+    case QGA_SEEK_SET:
+        return SEEK_SET;
+    case QGA_SEEK_CUR:
+        return SEEK_CUR;
+    case QGA_SEEK_END:
+        return SEEK_END;
+    }
+    error_setg(errp, "invalid whence code %"PRId64, whence->u.value);
+    return -1;
+}