1/29/2024 0 Comments Uuid generator linux![]() UUIDs are documented as part of ISO/ IEC 11578:1996 " Information technology – Open Systems Interconnection – Remote Procedure Call (RPC)" and more recently in ITU-T Rec. UUIDs are standardized by the Open Software Foundation (OSF) as part of the Distributed Computing Environment (DCE). When in July 20 was published as a proposed IETF standard, the ITU had also standardized UUIDs, based on the previous standards and early versions of RFC 4122. RFC 4122 registered a URN namespace for UUIDs and recapitulated the earlier specifications, with the same technical content. Later, the Microsoft Windows platforms adopted the DCE design as "globally unique identifiers" (GUIDs). The initial design of DCE UUIDs was based on the NCS UUIDs, whose design was in turn inspired by the ( 64-bit) unique identifiers defined and used pervasively in Domain/OS, an operating system designed by Apollo Computer. In the 1980s Apollo Computer originally used UUIDs in the Network Computing System (NCS) and later in the Open Software Foundation's (OSF) Distributed Computing Environment (DCE). Information labeled with UUIDs by independent parties can therefore be later combined into a single database or transmitted on the same channel, with a negligible probability of duplication.Īdoption of UUIDs is widespread, with many computing platforms providing support for generating them and for parsing their textual representation. Thus, anyone can create a UUID and use it to identify something with near certainty that the identifier does not duplicate one that has already been, or will be, created to identify something else. While the probability that a UUID will be duplicated is not zero, it is generally considered close enough to zero to be negligible. ![]() Their uniqueness does not depend on a central registration authority or coordination between the parties generating them, unlike most other numbering schemes. When generated according to the standard methods, UUIDs are, for practical purposes, unique. The term globally unique identifier ( GUID) is also used. Return ((rand() & 0x3) = 0 & n < len // Success only when snprintf result is a positive number and the provided buffer was large enough.A universally unique identifier ( UUID) is a 128-bit label used for information in computer systems. Here's a revised version of the code: #include The % should have been & (or 0x3fff should have been 0x4000 if using %, but division is always a more expensive operation than bitwise AND). Rand(), rand(), rand()) // Generates a 96-bit Hex numberįurthermore - the code produces 256 bit values, rather than 128 bit values compatible withĪnd final comment: rand() % 0x3fff + 0x8000, // Generates a 32-bit Hex number in the range ĭue to the modulo operator, the actual range produced is. Rand() % 0x3fff + 0x8000, // Generates a 32-bit Hex number in the range ((rand() & 0x0fff) | 0x4000), // Generates a 32-bit Hex number of the form 4xxx (4 indicates the UUID version) Rand(), rand(), // Generates a 64-bit Hex number The safest way to use rand() would be to rely on the fact that the lowest guaranteed RAND_MAX value anywhere is going to be 0x7fff - call it multiple times, shifting left by 15 bits and OR'ing with a new value, until the required amount of random bits is produced.Īlso, the format string in sprintf should have width specified, so leading zeros are taken into account (the widths are based on the mentioned bits in the respective argument comment): sprintf(strUuid, "%08x%08x-%08x-%08x-%08x-%08x%08x%08x", On Linux it's higher, but looks like it's 0x7fffffff, giving 31 bits of randomness, still missing 1 bit to full 32 bit length. I can't post comments on answers yet, but I'd just like to point out that the accepted answer's use of rand() won't work well at all on Windows, where RAND_MAX is defined as 0x7fff, giving just 15 bits of randomness.
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