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info.c
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info.c
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/* libguestfs
* Copyright (C) 2012 Red Hat Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <inttypes.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <assert.h>
#include <string.h>
#include <libintl.h>
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#ifdef HAVE_SYS_RESOURCE_H
#include <sys/resource.h>
#endif
#include <jansson.h>
#include "guestfs.h"
#include "guestfs-internal.h"
#include "guestfs-internal-actions.h"
#ifdef HAVE_ATTRIBUTE_CLEANUP
#define CLEANUP_JSON_T_DECREF __attribute__((cleanup(cleanup_json_t_decref)))
static void
cleanup_json_t_decref (void *ptr)
{
json_decref (* (json_t **) ptr);
}
#else
#define CLEANUP_JSON_T_DECREF
#endif
static json_t *get_json_output (guestfs_h *g, const char *filename);
static void set_child_rlimits (struct command *);
char *
guestfs_impl_disk_format (guestfs_h *g, const char *filename)
{
CLEANUP_JSON_T_DECREF json_t *tree = get_json_output (g, filename);
json_t *node;
if (tree == NULL)
return NULL;
if (!json_is_object (tree))
goto bad_type;
node = json_object_get (tree, "format");
if (!json_is_string (node))
goto bad_type;
return safe_strndup (g, json_string_value (node),
json_string_length (node)); /* caller frees */
bad_type:
error (g, _("qemu-img info: JSON output did not contain ‘format’ key"));
return NULL;
}
int64_t
guestfs_impl_disk_virtual_size (guestfs_h *g, const char *filename)
{
CLEANUP_JSON_T_DECREF json_t *tree = get_json_output (g, filename);
json_t *node;
if (tree == NULL)
return -1;
if (!json_is_object (tree))
goto bad_type;
node = json_object_get (tree, "virtual-size");
if (!json_is_integer (node))
goto bad_type;
return json_integer_value (node);
bad_type:
error (g, _("qemu-img info: JSON output did not contain ‘virtual-size’ key"));
return -1;
}
int
guestfs_impl_disk_has_backing_file (guestfs_h *g, const char *filename)
{
CLEANUP_JSON_T_DECREF json_t *tree = get_json_output (g, filename);
json_t *node;
if (tree == NULL)
return -1;
if (!json_is_object (tree))
goto bad_type;
node = json_object_get (tree, "backing-filename");
if (node == NULL)
return 0; /* no backing-filename key means no backing file */
/* Work on the assumption that if this field is null, it means
* no backing file, rather than being an error.
*/
if (json_is_null (node))
return 0;
return 1;
bad_type:
error (g, _("qemu-img info: JSON output was not an object"));
return -1;
}
/* Run 'qemu-img info --output json filename', and parse the output
* as JSON, returning a JSON tree and handling errors.
*/
static void parse_json (guestfs_h *g, void *treevp, const char *input, size_t len);
#define PARSE_JSON_NO_OUTPUT ((void *) -1)
static json_t *
get_json_output (guestfs_h *g, const char *filename)
{
CLEANUP_CMD_CLOSE struct command *cmd = guestfs_int_new_command (g);
int r;
json_t *tree = NULL;
guestfs_int_cmd_add_arg (cmd, "qemu-img");
guestfs_int_cmd_add_arg (cmd, "info");
guestfs_int_cmd_add_arg (cmd, "--output");
guestfs_int_cmd_add_arg (cmd, "json");
if (filename[0] == '/')
guestfs_int_cmd_add_arg (cmd, filename);
else
guestfs_int_cmd_add_arg_format (cmd, "./%s", filename);
guestfs_int_cmd_set_stdout_callback (cmd, parse_json, &tree,
CMD_STDOUT_FLAG_WHOLE_BUFFER);
set_child_rlimits (cmd);
r = guestfs_int_cmd_run (cmd);
if (r == -1)
return NULL;
if (!WIFEXITED (r) || WEXITSTATUS (r) != 0) {
guestfs_int_external_command_failed (g, r, "qemu-img info", filename);
return NULL;
}
if (tree == NULL)
return NULL; /* parse_json callback already set an error */
if (tree == PARSE_JSON_NO_OUTPUT) {
/* If this ever happened, it would indicate a bug in 'qemu-img info'. */
error (g, _("qemu-img info command produced no output, but didn't return an error status code"));
return NULL;
}
return tree; /* caller must call json_decref (tree) */
}
/* Parse the JSON document printed by qemu-img info --output json. */
static void
parse_json (guestfs_h *g, void *treevp, const char *input, size_t len)
{
json_t **tree_ret = treevp;
json_error_t err;
assert (*tree_ret == NULL);
/* If the input is completely empty, return a magic value to the
* caller. 'qemu-img info' will return an error, but this will let
* us catch the case where it does not.
*/
if (len == 0) {
*tree_ret = PARSE_JSON_NO_OUTPUT;
return;
}
debug (g, "%s: qemu-img info JSON output:\n%.*s\n", __func__, (int) len, input);
*tree_ret = json_loadb (input, len, 0, &err);
if (*tree_ret == NULL) {
if (strlen (err.text) > 0)
error (g, _("qemu-img info: JSON parse error: %s"), err.text);
else
error (g, _("qemu-img info: unknown JSON parse error"));
}
}
static void
set_child_rlimits (struct command *cmd)
{
#ifdef RLIMIT_AS
const long one_gb = 1024L * 1024 * 1024;
guestfs_int_cmd_set_child_rlimit (cmd, RLIMIT_AS, one_gb);
#endif
#ifdef RLIMIT_CPU
guestfs_int_cmd_set_child_rlimit (cmd, RLIMIT_CPU, 10 /* seconds */);
#endif
}