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file | guid.h |
| globally unique ID User API
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Globally Unique ID's provide a way to uniquely identify some thing. A GUID is a unique, cryptographically random 128-bit value. The identifier is so random that it is safe to assume that there is no other such item on the planet Earth, and indeed, not even in the Galaxy or beyond.
QOF GUID's can be used independently of any other subsystem in QOF. In particular, they do not require the use of other parts of the object subsystem. New GUID's are usually created by initialising a new entity using qof_instance_init, rather than calling GUID functions directly.
#define GUID_DATA_SIZE 16 |
The type used to store guids
Definition at line 52 of file guid.h.
#define GUID_ENCODING_LENGTH 32 |
number of characters needed to encode a guid as a string not including the null terminator.
Definition at line 64 of file guid.h.
gboolean guid_equal |
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const GUID * |
guid_1, |
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const GUID * |
guid_2 |
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) |
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Given two GUIDs, return TRUE if they are non-NULL and equal. Return FALSE, otherwise.
Definition at line 652 of file guid.c.
654 if (guid_1 && guid_2)
guint guid_hash_to_guint |
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gconstpointer |
ptr | ) |
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Given a GUID *, hash it to a guint
Definition at line 677 of file guid.c.
679 const GUID *guid = ptr;
683 PERR (
"received NULL guid pointer.");
687 if (
sizeof (guint) <=
sizeof (guid->data))
689 return (*((guint *) guid->data));
696 for (i = 0, j = 0; i <
sizeof (guint); i++, j++)
702 hash |= guid->data[j];
Initialize the id generator with a variety of random sources.
- Note
- Only one of guid_init(), guid_init_with_salt() and guid_init_only_salt() should be called. Calling any initialization function a second time will reset the generator and erase the effect of the first call.
Definition at line 325 of file guid.c.
332 md5_init_ctx (&guid_context);
335 bytes += init_from_file (
"/dev/urandom", 512);
339 const char *files[] = {
"/etc/passwd",
344 "/proc/self/environ",
352 for (i = 0; files[i] != NULL; i++)
353 bytes += init_from_file (files[i], BLOCKSIZE);
359 const char *dirs[] = {
371 for (i = 0; dirs[i] != NULL; i++)
372 bytes += init_from_dir (dirs[i], 32);
374 dirname = g_get_home_dir ();
376 bytes += init_from_dir (dirname, 32);
384 md5_process_bytes (&pid,
sizeof (pid), &guid_context);
385 bytes +=
sizeof (pid);
389 md5_process_bytes (&pid,
sizeof (pid), &guid_context);
390 bytes +=
sizeof (pid);
404 md5_process_bytes (s, strlen (s), &guid_context);
409 md5_process_bytes (&uid,
sizeof (uid), &guid_context);
410 bytes +=
sizeof (uid);
413 md5_process_bytes (&gid,
sizeof (gid), &guid_context);
414 bytes +=
sizeof (gid);
420 #ifdef HAVE_GETHOSTNAME
423 memset (
string, 0,
sizeof (
string));
424 gethostname (
string,
sizeof (
string));
425 md5_process_bytes (
string,
sizeof (
string), &guid_context);
426 bytes +=
sizeof (string);
434 srand ((
unsigned int) time (NULL));
436 for (i = 0; i < 32; i++)
440 md5_process_bytes (&n,
sizeof (n), &guid_context);
446 bytes += init_from_time ();
448 PINFO (
"got %llu bytes", (
unsigned long long int) bytes);
450 if (bytes < THRESHOLD)
451 PWARN (
"only got %llu bytes.\n"
452 "The identifiers might not be very random.\n",
453 (
unsigned long long int) bytes);
455 guid_initialized = TRUE;
void guid_init_only_salt |
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const void * |
salt, |
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size_t |
salt_len |
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Initialize the id generator with the data given in the salt argument, but not with any other source. Calling this function with a specific argument will reliably produce a specific sequence of ids.
- Parameters
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salt | The additional random values to add to the generator. |
salt_len | The length of the additional random values. |
- Note
- Only one of guid_init(), guid_init_with_salt() and guid_init_only_salt() should be called. Calling any initialization function a second time will reset the generator and erase the effect of the first call.
Definition at line 467 of file guid.c.
469 md5_init_ctx (&guid_context);
471 md5_process_bytes (salt, salt_len, &guid_context);
473 guid_initialized = TRUE;
void guid_init_with_salt |
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const void * |
salt, |
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size_t |
salt_len |
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) |
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Initialize the id generator with a variety of random sources. and with the data given in the salt argument. This argument can be used to add additional randomness to the generated ids.
- Parameters
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salt | The additional random values to add to the generator. |
salt_len | The length of the additional random values. |
- Note
- Only one of guid_init(), guid_init_with_salt() and guid_init_only_salt() should be called. Calling any initialization function a second time will reset the generator and erase the effect of the first call.
Definition at line 459 of file guid.c.
463 md5_process_bytes (salt, salt_len, &guid_context);
GUID* guid_malloc |
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void |
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Efficiently allocate & free memory for GUIDs
Definition at line 100 of file guid.c.
103 guid_memchunk_init ();
104 return g_chunk_new (
GUID, guid_memchunk);
void guid_new |
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GUID * |
guid | ) |
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Generate a new id. If no initialization function has been called, guid_init() will be called before the id is created.
- Parameters
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guid | A pointer to an existing guid data structure. The existing value will be replaced with a new value. |
This routine uses the md5 algorithm to build strong random guids. Note that while guid's are generated randomly, the odds of this routine returning a non-unique id are astronomically small. (Literally astronomically: If you had Cray's on every solar system in the universe running for the entire age of the universe, you'd still have less than a one-in-a-million chance of coming up with a duplicate id. 2^128 == 10^38 is a really really big number.)
Definition at line 487 of file guid.c.
489 static int counter = 0;
495 if (!guid_initialized)
500 md5_finish_ctx (&ctx, guid->data);
516 init_from_int (433781 * counter);
523 fp = fopen (
"/dev/urandom",
"r");
527 init_from_stream (fp, 32);
531 counter = GUID_PERIOD;
GUID guid_new_return |
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void |
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Generate a new id. If no initialization function has been called, guid_init() will be called before the id is created.
- Returns
- guid A data structure containing a newly allocated GUID. Caller is responsible for calling guid_free().
Definition at line 538 of file guid.c.
const GUID* guid_null |
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void |
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Returns a GUID which is guaranteed
to never reference any entity.
Definition at line 119 of file guid.c.
121 static int null_inited = 0;
122 static GUID null_guid;
127 char *tmp =
"NULLGUID.EMPTY.";
131 null_guid.data[i] = tmp[i];
void guid_shutdown |
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void |
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Release the memory chunk associated with gui storage. Use this only when shutting down the program, as it invalidates all GUIDs at once.
Definition at line 477 of file guid.c.
480 guid_memchunk_shutdown ();
const gchar* guid_to_string |
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const GUID * |
guid | ) |
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The guid_to_string() routine returns a null-terminated string encoding of the id. String encodings of identifiers are hex numbers printed only with the characters '0' through '9' and 'a' through 'f'. The encoding will always be GUID_ENCODING_LENGTH characters long.
XXX This routine is not thread safe and is deprecated. Please use the routine guid_to_string_buff() instead.
- Parameters
-
- Returns
- A pointer to the starting character of the string. The returned memory is owned by this routine and may not be freed by the caller.
Definition at line 611 of file guid.c.
613 #ifdef G_THREADS_ENABLED
614 static GStaticPrivate guid_buffer_key = G_STATIC_PRIVATE_INIT;
617 string = g_static_private_get (&guid_buffer_key);
621 g_static_private_set (&guid_buffer_key,
string, g_free);
624 static char string[64];
627 encode_md5_data (guid->data,
string);
gchar* guid_to_string_buff |
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const GUID * |
guid, |
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gchar * |
buff |
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) |
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The guid_to_string_buff() routine puts a null-terminated string encoding of the id into the memory pointed at by buff. The buffer must be at least GUID_ENCODING_LENGTH+1 characters long. This routine is handy for avoiding a malloc/free cycle. It returns a pointer to the >>end<< of what was written. (i.e. it can be used like 'stpcpy' during string concatenation)
- Parameters
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guid | The guid to print. |
buff | The buffer to print it into. |
- Returns
- A pointer to the terminating null character of the string.
gboolean string_to_guid |
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const gchar * |
string, |
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GUID * |
guid |
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) |
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Given a string, decode the id into the guid if guid is non-NULL. The function returns TRUE if the string was a valid 32 character hexadecimal number. This function accepts both upper and lower case hex digits. If the return value is FALSE, the effect on guid is undefined.