+static tree234 *agent_connections;
+struct agent_connection {
+ int fd;
+ char *retbuf;
+ char sizebuf[4];
+ int retsize, retlen;
+ void (*callback)(void *, void *, int);
+ void *callback_ctx;
+};
+static int agent_conncmp(void *av, void *bv)
+{
+ struct agent_connection *a = (struct agent_connection *) av;
+ struct agent_connection *b = (struct agent_connection *) bv;
+ if (a->fd < b->fd)
+ return -1;
+ if (a->fd > b->fd)
+ return +1;
+ return 0;
+}
+static int agent_connfind(void *av, void *bv)
+{
+ int afd = *(int *) av;
+ struct agent_connection *b = (struct agent_connection *) bv;
+ if (afd < b->fd)
+ return -1;
+ if (afd > b->fd)
+ return +1;
+ return 0;
+}
+
+/*
+ * Attempt to read from an agent socket fd. Returns 0 if the expected
+ * response is as yet incomplete; returns 1 if it's either complete
+ * (conn->retbuf non-NULL and filled with something useful) or has
+ * failed totally (conn->retbuf is NULL).
+ */
+static int agent_try_read(struct agent_connection *conn)
+{
+ int ret;
+
+ ret = read(conn->fd, conn->retbuf+conn->retlen,
+ conn->retsize-conn->retlen);
+ if (ret <= 0) {
+ if (conn->retbuf != conn->sizebuf) sfree(conn->retbuf);
+ conn->retbuf = NULL;
+ conn->retlen = 0;
+ return 1;
+ }
+ conn->retlen += ret;
+ if (conn->retsize == 4 && conn->retlen == 4) {
+ conn->retsize = toint(GET_32BIT(conn->retbuf) + 4);
+ if (conn->retsize <= 0) {
+ conn->retbuf = NULL;
+ conn->retlen = 0;
+ return -1; /* way too large */
+ }
+ assert(conn->retbuf == conn->sizebuf);
+ conn->retbuf = snewn(conn->retsize, char);
+ memcpy(conn->retbuf, conn->sizebuf, 4);
+ }
+
+ if (conn->retlen < conn->retsize)
+ return 0; /* more data to come */
+
+ return 1;
+}
+
+static int agent_select_result(int fd, int event)
+{
+ struct agent_connection *conn;
+
+ assert(event == 1); /* not selecting for anything but R */
+
+ conn = find234(agent_connections, &fd, agent_connfind);
+ if (!conn) {
+ uxsel_del(fd);
+ return 1;
+ }
+
+ if (!agent_try_read(conn))
+ return 0; /* more data to come */
+
+ /*
+ * We have now completed the agent query. Do the callback, and
+ * clean up. (Of course we don't free retbuf, since ownership
+ * of that passes to the callback.)
+ */
+ conn->callback(conn->callback_ctx, conn->retbuf, conn->retlen);
+ uxsel_del(fd);
+ close(fd);
+ del234(agent_connections, conn);
+ sfree(conn);
+ return 0;
+}
+
+int agent_query(void *in, int inlen, void **out, int *outlen,
+ void (*callback)(void *, void *, int), void *callback_ctx)