spice-qemu-char: Remove intermediate buffer

virtio-serial's buffer is valid when it calls us, and we don't
access it otherwise: vmc_read is only called in response to wakeup,
or else we set datalen=0 and throttle. Then vmc_read is called back,
we return 0 (not accessing the buffer) and set the timer to unthrottle.

Also make datalen int and not ssize_t (to fit spice_chr_write signature).

HdG: Update to apply to spice-qemu-char with new gio-channel based
flowcontrol support.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

spice-qemu-char.c

@@ -14,9 +14,8 @@ typedef struct SpiceCharDriver {
     char                  *subtype;
     bool                  active;
     bool                  blocked;
-    uint8_t               *buffer;
-    uint8_t               *datapos;
-    ssize_t               bufsize, datalen;
+    const uint8_t         *datapos;
+    int                   datalen;
     QLIST_ENTRY(SpiceCharDriver) next;
 } SpiceCharDriver;
 
@@ -186,12 +185,7 @@ static int spice_chr_write(CharDriverState *chr, const uint8_t *buf, int len)
     int read_bytes;
 
     assert(s->datalen == 0);
-    if (s->bufsize < len) {
-        s->bufsize = len;
-        s->buffer = g_realloc(s->buffer, s->bufsize);
-    }
-    memcpy(s->buffer, buf, len);
-    s->datapos = s->buffer;
+    s->datapos = buf;
     s->datalen = len;
     spice_server_char_device_wakeup(&s->sin);
     read_bytes = len - s->datalen;