[Xen-changelog] [xen-unstable] libxl: datacopier: provide "prefix data" facility

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
# Date 1340905403 -3600
# Node ID 59127c03d75c7d7e6556ec545c957660770bddfa
# Parent  1883e5c71a87797fbb841a3ee59f166b7a6af09d
libxl: datacopier: provide "prefix data" facility

This will be used to write the qemu data banner to the save/migration
stream.

Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---


diff -r 1883e5c71a87 -r 59127c03d75c tools/libxl/libxl_aoutils.c
--- a/tools/libxl/libxl_aoutils.c       Thu Jun 28 18:43:23 2012 +0100
+++ b/tools/libxl/libxl_aoutils.c       Thu Jun 28 18:43:23 2012 +0100
@@ -74,6 +74,28 @@ static void datacopier_check_state(libxl
     }
 }
 
+void libxl__datacopier_prefixdata(libxl__egc *egc, libxl__datacopier_state *dc,
+                                  const void *data, size_t len)
+{
+    libxl__datacopier_buf *buf;
+    /*
+     * It is safe for this to be called immediately after _start, as
+     * is documented in the public comment.  _start's caller must have
+     * the ctx locked, so other threads don't get to mess with the
+     * contents, and the fd events cannot happen reentrantly.  So we
+     * are guaranteed to beat the first data from the read fd.
+     */
+
+    assert(len < dc->maxsz - dc->used);
+
+    buf = libxl__zalloc(0, sizeof(*buf) - sizeof(buf->buf) + len);
+    buf->used = len;
+    memcpy(buf->buf, data, len);
+
+    dc->used += len;
+    LIBXL_TAILQ_INSERT_TAIL(&dc->bufs, buf, entry);
+}
+
 static void datacopier_readable(libxl__egc *egc, libxl__ev_fd *ev,
                                 int fd, short events, short revents) {
     libxl__datacopier_state *dc = CONTAINER_OF(ev, *dc, toread);
diff -r 1883e5c71a87 -r 59127c03d75c tools/libxl/libxl_internal.h
--- a/tools/libxl/libxl_internal.h      Thu Jun 28 18:43:23 2012 +0100
+++ b/tools/libxl/libxl_internal.h      Thu Jun 28 18:43:23 2012 +0100
@@ -1811,6 +1811,12 @@ _hidden void libxl__datacopier_init(libx
 _hidden void libxl__datacopier_kill(libxl__datacopier_state *dc);
 _hidden int libxl__datacopier_start(libxl__datacopier_state *dc);
 
+/* Inserts literal data into the output stream.  The data is copied.
+ * May safely be used only immediately after libxl__datacopier_start
+ * (before the ctx is unlocked).  But may be called multiple times.
+ * NB exceeding maxsz will fail an assertion! */
+_hidden void libxl__datacopier_prefixdata(libxl__egc*, 
libxl__datacopier_state*,
+                                          const void *data, size_t len);
 
 /*----- Save/restore helper (used by creation and suspend) -----*/
 

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