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[Qemu-devel] [PULL 23/29] util - add automated ID generation utility
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PULL 23/29] util - add automated ID generation utility |
Date: |
Fri, 16 Oct 2015 17:06:08 +0200 |
From: Jeff Cody <address@hidden>
Multiple sub-systems in QEMU may find it useful to generate IDs
for objects that a user may reference via QMP or HMP. This patch
presents a standardized way to do it, so that automatic ID generation
follows the same rules.
This patch enforces the following rules when generating an ID:
1.) Guarantee no collisions with a user-specified ID
2.) Identify the sub-system the ID belongs to
3.) Guarantee of uniqueness
4.) Spoiling predictability, to avoid creating an assumption
of object ordering and parsing (i.e., we don't want users to think
they can guess the next ID based on prior behavior).
The scheme for this is as follows (no spaces):
# subsys D RR
Reserved char --| | | |
Subsystem String ----| | |
Unique number (64-bit) --| |
Two-digit random number ---|
For example, a generated node-name for the block sub-system may look
like this:
#block076
The caller of id_generate() is responsible for freeing the generated
node name string with g_free().
Reviewed-by: John Snow <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Reviewed-by: Alberto Garcia <address@hidden>
Signed-off-by: Jeff Cody <address@hidden>
Signed-off-by: Kevin Wolf <address@hidden>
---
include/qemu-common.h | 8 ++++++++
util/id.c | 37 +++++++++++++++++++++++++++++++++++++
2 files changed, 45 insertions(+)
diff --git a/include/qemu-common.h b/include/qemu-common.h
index 0bd212b..2f74540 100644
--- a/include/qemu-common.h
+++ b/include/qemu-common.h
@@ -246,6 +246,14 @@ int64_t qemu_strtosz_suffix_unit(const char *nptr, char
**end,
#define STR_OR_NULL(str) ((str) ? (str) : "null")
/* id.c */
+
+typedef enum IdSubSystems {
+ ID_QDEV,
+ ID_BLOCK,
+ ID_MAX /* last element, used as array size */
+} IdSubSystems;
+
+char *id_generate(IdSubSystems id);
bool id_wellformed(const char *id);
/* path.c */
diff --git a/util/id.c b/util/id.c
index 09b22fb..bcc64d8 100644
--- a/util/id.c
+++ b/util/id.c
@@ -26,3 +26,40 @@ bool id_wellformed(const char *id)
}
return true;
}
+
+#define ID_SPECIAL_CHAR '#'
+
+static const char *const id_subsys_str[] = {
+ [ID_QDEV] = "qdev",
+ [ID_BLOCK] = "block",
+};
+
+/*
+ * Generates an ID of the form PREFIX SUBSYSTEM NUMBER
+ * where:
+ *
+ * - PREFIX is the reserved character '#'
+ * - SUBSYSTEM identifies the subsystem creating the ID
+ * - NUMBER is a decimal number unique within SUBSYSTEM.
+ *
+ * Example: "#block146"
+ *
+ * Note that these IDs do not satisfy id_wellformed().
+ *
+ * The caller is responsible for freeing the returned string with g_free()
+ */
+char *id_generate(IdSubSystems id)
+{
+ static uint64_t id_counters[ID_MAX];
+ uint32_t rnd;
+
+ assert(id < ID_MAX);
+ assert(id_subsys_str[id]);
+
+ rnd = g_random_int_range(0, 100);
+
+ return g_strdup_printf("%c%s%" PRIu64 "%02" PRId32, ID_SPECIAL_CHAR,
+ id_subsys_str[id],
+ id_counters[id]++,
+ rnd);
+}
--
1.8.3.1
- [Qemu-devel] [PULL 16/29] block: Introduce parents list, (continued)
- [Qemu-devel] [PULL 16/29] block: Introduce parents list, Kevin Wolf, 2015/10/16
- [Qemu-devel] [PULL 18/29] blockjob: Store device name at job creation, Kevin Wolf, 2015/10/16
- [Qemu-devel] [PULL 11/29] block: Convert bs->backing_hd to BdrvChild, Kevin Wolf, 2015/10/16
- [Qemu-devel] [PULL 15/29] block-backend: Add blk_set_bs(), Kevin Wolf, 2015/10/16
- [Qemu-devel] [PULL 17/29] block: Implement bdrv_append() without bdrv_swap(), Kevin Wolf, 2015/10/16
- [Qemu-devel] [PULL 12/29] block: Manage backing file references in bdrv_set_backing_hd(), Kevin Wolf, 2015/10/16
- [Qemu-devel] [PULL 21/29] block: Allow bdrv_unref_child(bs, NULL), Kevin Wolf, 2015/10/16
- [Qemu-devel] [PULL 20/29] block: Remove bdrv_swap(), Kevin Wolf, 2015/10/16
- [Qemu-devel] [PULL 22/29] blkverify: Fix BDS leak in .bdrv_open error path, Kevin Wolf, 2015/10/16
- [Qemu-devel] [PULL 19/29] block: Add and use bdrv_replace_in_backing_chain(), Kevin Wolf, 2015/10/16
- [Qemu-devel] [PULL 23/29] util - add automated ID generation utility,
Kevin Wolf <=
- [Qemu-devel] [PULL 25/29] raw-posix: warn about BDRV_O_NATIVE_AIO if libaio is unavailable, Kevin Wolf, 2015/10/16
- [Qemu-devel] [PULL 26/29] blockdev: always compile in -drive aio= parsing, Kevin Wolf, 2015/10/16
- [Qemu-devel] [PULL 09/29] block: Convert bs->file to BdrvChild, Kevin Wolf, 2015/10/16
- [Qemu-devel] [PULL 24/29] block: auto-generated node-names, Kevin Wolf, 2015/10/16
- [Qemu-devel] [PULL 27/29] qemu-nbd: always compile in --aio=MODE option, Kevin Wolf, 2015/10/16
- [Qemu-devel] [PULL 28/29] qcow2: Remove forward declaration of QCowAIOCB, Kevin Wolf, 2015/10/16
- [Qemu-devel] [PULL 29/29] blkdebug: Don't confuse image as backing file, Kevin Wolf, 2015/10/16
- Re: [Qemu-devel] [PULL 00/29] Block layer patches, Peter Maydell, 2015/10/18