tests: add file-write-read test

This test exhibits a POSIX behaviour regarding switching between write
and read. It's undefined result if the application doesn't ensure a
flush between the two operations (with glibc, the flush can be implicit
when the buffer size is relatively small). The previous commit fixes
this test.

Related to:
https://bugzilla.redhat.com/show_bug.cgi?id=1210246

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

tests/test-qga.c

@@ -352,10 +352,10 @@ static void test_qga_network_get_interfaces(gconstpointer fix)
 static void test_qga_file_ops(gconstpointer fix)
 {
     const TestFixture *fixture = fix;
-    const guchar helloworld[] = "Hello World!\n";
+    const unsigned char helloworld[] = "Hello World!\n";
     const char *b64;
     gchar *cmd, *path, *enc;
-    guchar *dec;
+    unsigned char *dec;
     QDict *ret, *val;
     int64_t id, eof;
     gsize count;
@@ -496,6 +496,96 @@ static void test_qga_file_ops(gconstpointer fix)
     g_free(cmd);
 }
 
+static void test_qga_file_write_read(gconstpointer fix)
+{
+    const TestFixture *fixture = fix;
+    const unsigned char helloworld[] = "Hello World!\n";
+    const char *b64;
+    gchar *cmd, *enc;
+    QDict *ret, *val;
+    int64_t id, eof;
+    gsize count;
+
+    /* open */
+    ret = qmp_fd(fixture->fd, "{'execute': 'guest-file-open',"
+                 " 'arguments': { 'path': 'foo', 'mode': 'w+' } }");
+    g_assert_nonnull(ret);
+    qmp_assert_no_error(ret);
+    id = qdict_get_int(ret, "return");
+    QDECREF(ret);
+
+    enc = g_base64_encode(helloworld, sizeof(helloworld));
+    /* write */
+    cmd = g_strdup_printf("{'execute': 'guest-file-write',"
+                          " 'arguments': { 'handle': %" PRId64 ","
+                          " 'buf-b64': '%s' } }", id, enc);
+    ret = qmp_fd(fixture->fd, cmd);
+    g_assert_nonnull(ret);
+    qmp_assert_no_error(ret);
+
+    val = qdict_get_qdict(ret, "return");
+    count = qdict_get_int(val, "count");
+    eof = qdict_get_bool(val, "eof");
+    g_assert_cmpint(count, ==, sizeof(helloworld));
+    g_assert_cmpint(eof, ==, 0);
+    QDECREF(ret);
+    g_free(cmd);
+
+    /* read (check implicit flush) */
+    cmd = g_strdup_printf("{'execute': 'guest-file-read',"
+                          " 'arguments': { 'handle': %" PRId64 "} }",
+                          id);
+    ret = qmp_fd(fixture->fd, cmd);
+    val = qdict_get_qdict(ret, "return");
+    count = qdict_get_int(val, "count");
+    eof = qdict_get_bool(val, "eof");
+    b64 = qdict_get_str(val, "buf-b64");
+    g_assert_cmpint(count, ==, 0);
+    g_assert(eof);
+    g_assert_cmpstr(b64, ==, "");
+    QDECREF(ret);
+    g_free(cmd);
+
+    /* seek to 0 */
+    cmd = g_strdup_printf("{'execute': 'guest-file-seek',"
+                          " 'arguments': { 'handle': %" PRId64 ", "
+                          " 'offset': %d, 'whence': %d } }",
+                          id, 0, SEEK_SET);
+    ret = qmp_fd(fixture->fd, cmd);
+    qmp_assert_no_error(ret);
+    val = qdict_get_qdict(ret, "return");
+    count = qdict_get_int(val, "position");
+    eof = qdict_get_bool(val, "eof");
+    g_assert_cmpint(count, ==, 0);
+    g_assert(!eof);
+    QDECREF(ret);
+    g_free(cmd);
+
+    /* read */
+    cmd = g_strdup_printf("{'execute': 'guest-file-read',"
+                          " 'arguments': { 'handle': %" PRId64 "} }",
+                          id);
+    ret = qmp_fd(fixture->fd, cmd);
+    val = qdict_get_qdict(ret, "return");
+    count = qdict_get_int(val, "count");
+    eof = qdict_get_bool(val, "eof");
+    b64 = qdict_get_str(val, "buf-b64");
+    g_assert_cmpint(count, ==, sizeof(helloworld));
+    g_assert(eof);
+    g_assert_cmpstr(b64, ==, enc);
+    QDECREF(ret);
+    g_free(cmd);
+    g_free(enc);
+
+    /* close */
+    cmd = g_strdup_printf("{'execute': 'guest-file-close',"
+                          " 'arguments': {'handle': %" PRId64 "} }",
+                          id);
+    ret = qmp_fd(fixture->fd, cmd);
+    QDECREF(ret);
+    g_free(cmd);
+}
+
 static void test_qga_get_time(gconstpointer fix)
 {
     const TestFixture *fixture = fix;
@@ -762,6 +852,7 @@ int main(int argc, char **argv)
     g_test_add_data_func("/qga/get-memory-blocks", &fix,
                          test_qga_get_memory_blocks);
     g_test_add_data_func("/qga/file-ops", &fix, test_qga_file_ops);
+    g_test_add_data_func("/qga/file-write-read", &fix, test_qga_file_write_read);
     g_test_add_data_func("/qga/get-time", &fix, test_qga_get_time);
     g_test_add_data_func("/qga/invalid-cmd", &fix, test_qga_invalid_cmd);
     g_test_add_data_func("/qga/fsfreeze-status", &fix,