[Spice-devel] [PATCH 2/2] replay: allows to specify a filter for record output

[Frediano Ziglio]

This allows compressions using external programs or any type
of filters.

To use it set SPICE_WORKER_RECORD_FILTER environment to the
filter command you want to use. The command is executed with
g_spawn_async_with_pipes (which uses execve) so is not a shell
command although the command is parsed using g_shell_parse_argv
which split arguments as shell does.

One easy way to use it is to just use a compressor like gzip with

  export SPICE_WORKER_RECORD_FILENAME=/tmp/qemu_record.gz
  export SPICE_WORKER_RECORD_FILTER=gzip
  qemu ...

The filter will receive the recording on standard input and is
supposed to write in output filename (which is the standard output).
Nothing forbid to close and delete the file and do something else
use additional argument in SPICE_WORKER_RECORD_FILTER to specify
for instance compression level. Note however that even if you don't
use the output file is always opened and SPICE_WORKER_RECORD_FILENAME
have to be defined to enable recording.

Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
---
 server/red-record-qxl.c | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/server/red-record-qxl.c b/server/red-record-qxl.c
index 4821222..2709b47 100644
--- a/server/red-record-qxl.c
+++ b/server/red-record-qxl.c
@@ -21,6 +21,8 @@
 
 #include <stdbool.h>
 #include <inttypes.h>
+#include <fcntl.h>
+#include <glib.h>
 #include "red-worker.h"
 #include "red-common.h"
 #include "memslot.h"
@@ -834,11 +836,22 @@ void red_record_qxl_command(RedRecord *record, RedMemSlotInfo *slots,
     }
 }
 
+static void out_setup(gpointer user_data)
+{
+    int fd = GPOINTER_TO_INT(user_data);
+
+    while (dup2(fd, 1) < 0 && errno == EINTR)
+        continue;
+    close(fd);
+    fcntl(1, F_SETFD, 0);
+}
+
 RedRecord *red_record_new(void)
 {
     static const char header[] = "SPICE_REPLAY 1\n";
 
     const char *filename;
+    const char *filter;
     FILE *f;
     RedRecord *record;
 
@@ -852,6 +865,33 @@ RedRecord *red_record_new(void)
         return NULL;
     }
 
+    filter = getenv("SPICE_WORKER_RECORD_FILTER");
+    if (filter) {
+        gint argc;
+        gchar **argv = NULL;
+        GError *error = NULL;
+        GPid child_pid;
+        gboolean ret;
+        gint fd_in;
+
+        ret = g_shell_parse_argv(filter, &argc, &argv, &error);
+
+        if (ret)
+            ret = g_spawn_async_with_pipes(NULL, argv, NULL, G_SPAWN_SEARCH_PATH,
+                               out_setup, GINT_TO_POINTER(fileno(f)), &child_pid,
+                               &fd_in, NULL, NULL, &error);
+
+        g_strfreev(argv);
+        if (!ret) {
+            g_error_free(error);
+            fclose(f);
+            spice_error("failed to setup filter for replay");
+        }
+        while (dup2(fd_in, fileno(f)) < 0 && errno == EINTR)
+            continue;
+        close(fd_in);
+    }
+
     if (fwrite(header, sizeof(header)-1, 1, f) != 1) {
         spice_error("failed to write replay header");
     }
-- 
2.7.4