uuid: A C repository from mackron

UUID Generator

This supports all UUID versions defined in RFC 4122 except version 2. For version 3 and 5 you will need to provide your own MD5 and SHA-1 hashing implementation by defining the some macros before the implementation of this library. Below is an example:

#define UUID_MD5_CTX_TYPE               md5_context
#define UUID_MD5_INIT(ctx)              md5_init(ctx)
#define UUID_MD5_FINAL(ctx, digest)     md5_finalize(ctx, (unsigned char*)(digest))
#define UUID_MD5_UPDATE(ctx, src, sz)   md5_update(ctx, src, (size_t)(sz))

#define UUID_SHA1_CTX_TYPE              sha1_context
#define UUID_SHA1_INIT(ctx)             sha1_init(ctx)
#define UUID_SHA1_FINAL(ctx, digest)    sha1_finalize(ctx, (unsigned char*)(digest))
#define UUID_SHA1_UPDATE(ctx, src, sz)  sha1_update(ctx, src, (size_t)(sz));

A public domain MD5 and SHA-1 hashing implmentation can be found here:

These are included as submodules in this repository for your convenience but need not be used if you would rather use a different implementation. If you want to use these libraries, instead of defining the above macros you can just include them before the implementation like so and they'll automatically be detected:

#include "external/md5/md5.c"    // <-- Enables version 3.
#include "external/sha1/sha1.c"  // <-- Enables version 5.

#define UUID_IMPLEMENTATION
#include "uuid.h"

There is no need to link to anything with this library. You can use UUID_IMPLEMENTATION to define the implementation section, or you can use uuid.c if you prefer a traditional header/source pair.

Use the following APIs to generate a UUID:

uuid1(unsigned char* pUUID, uuid_rand* pRNG);
uuid3(unsigned char* pUUID, const unsigned char* pNamespaceUUID, const char* pName);
uuid4(unsigned char* pUUID, uuid_rand* pRNG);
uuid5(unsigned char* pUUID, const unsigned char* pNamespaceUUID, const char* pName);
uuid_ordered(unsigned char* pUUID, uuid_rand* pRNG);

If you want to use a time-based ordered UUID you can use uuid_ordered(). Note that this is not officially allowed by RFC 4122. This does not encode a version as it would break ordering.

Use the following APIs to format the UUID as a string:

uuid_format(char* pDst, size_t dstCap, const unsigned char* pUUID);

The size of the UUID buffer must be at least UUID_SIZE (16 bytes). For formatted strings the destination buffer should be at least UUID_SIZE_FORMATTED.

Example:

unsigned char uuid[UUID_SIZE];
uuid4(uuid, NULL);

char str[UUID_SIZE_FORMATTED];
uuid_format(str, sizeof(str), uuid);

With the code above the default random number generator will be used (second parameter). If you want to use your own random number generator, you can pass in a random number generator:

uuid4(uuid, &myRNG);

The default random number generator is cryptorand: https://github.com/mackron/cryptorand. If you have access to the implementation section, you can make use of this easily:

uuid_cryptorand rng;
uuid_cryprorand_init(&rng);

for (i = 0; i < count; i += 1) {
    uuid4(uuid, &rng);

    // ... do something with the UUID ...
}

uuiid_cryptorand_uninit(&rng);

Alternatively you can implement your own random number generator by inheritting from uuid_rand_callbacks like so:

typedef struct
{
    uuid_rand_callbacks cb;
} my_rng;

static uuid_result my_rng_generate(uuid_rand* pRNG, void* pBufferOut, size_t byteCount)
{
    my_rng* pMyRNG = (my_rng*)pRNG;

    // ... do random number generation here. Output byteCount bytes to pBufferOut.

    return UUID_SUCCESS;
}

...

// Initialize your random number generator.
my_rng myRNG;
rng.cb.onGenerator = my_rng_generate;

// Generate your GUID.
uuid4(uuid, &myRNG);

You can disable cryptorand and compile time with UUID_NO_CRYPTORAND, but by doing so you will be required to specify your own random number generator. This is useful if you already have a good quality random number generator in your code base and want to save a little bit of space.

mackron/uuid

UUID Generator