CrossGuid
CrossGuid is a minimal, cross platform, C++ GUID library. It uses the best native GUID/UUID generator on the given platform and has a generic class for parsing, stringifying, and comparing IDs. The guid generation technique is determined by spefifying one of the following preprocessor flags:
GUID_LIBUUID
- Useslibuuid
which is normally used on linux but possibly usable elsewhere as well.GUID_CFUUID
- UsesCFCreateUUID
from Apple'sCoreFoundation
framework. This works on both Mac OSX and iOS.GUID_WINDOWS
- Uses the built inCoCreateGuid
function in Windows.GUID_ANDROID
- Uses JNI to invoke Java functions from Android SDK.
Versions
This is version 0.2 of CrossGuid. If you all already using CrossGuid and your code
uses GuidGenerator
then you are using version 0.1. Differences in version 0.2:
- Put everything inside the namespace
xg
instead of using the global namespace. - Removed
GuidGenerator
class and replaced with the free functionxg::newGuid
. This is the way I originally wanted it to work but since Android is a special snowflake requiring state (JNIEnv *
) I introduced theGuidGenerator
class specifically so that there would be somewhere to store theJNIEnv *
when running on Android. However, this basically meant complicating the library for the sake of one platform. In version 0.2 the goal is to design for the normal platforms and let Android be weird. In Android you just need to runxg::initJni(JNIEnv *)
before you create any guids. TheJNIEnv *
is just stored as a global variable. - Added CMake build system. Instead of different scripts for each platform you can just run cmake and it should handle each platform (except Android which again is special).
- Actual guid bytes are stored in
std::array<unsigned char, 16>
instead ofstd::vector<unsigned char>
. - More error checking (like if you try to create a guid with invalid number of bytes).
If you're happily using version 0.1 then there's not really any reason to change.
Compiling
Just do the normal cmake thing:
mkdir build
cd build
cmake ..
make
Running tests
After compiling as described above you should get two files: libxg.a
(the
static library) and xgtest
(the test runner). So to run the tests just do:
./xgtest
Basic usage
Creating guids
Create a new random guid:
auto g = xg::newGuid();
NOTE: On Android you need to call xg::initJni(JNIEnv *)
first so that it
is possible for xg::newGuid()
to call back into java libraries. initJni
only needs to be called once when the process starts.
Create a new zero guid:
xg::Guid g;
Create from a string:
xg::Guid g("c405c66c-ccbb-4ffd-9b62-c286c0fd7a3b");
Checking validity
If you have some string value and you need to check whether it is a valid guid then you can simply attempt to construct the guid:
xg::Guid g("bad-guid-string");
if (!g.isValid())
{
// do stuff
}
If the guid string is not valid then all bytes are set to zero and isValid()
returns false
.
Converting guid to string
First of all, there is normally no reason to convert a guid to a string except
for in debugging or when serializing for API calls or whatever. You should
definitely avoid storing guids as strings or using strings for any
computations. If you do need to convert a guid to a string, then you can
utilize strings because the <<
operator is overloaded. To print a guid to
std::cout
:
void doGuidStuff(GuidGenerator generator)
{
auto myGuid = generator.newGuid();
std::cout << "Here is a guid: " << myGuid << std::endl;
}
Or to store a guid in a std::string
:
void doGuidStuff(GuidGenerator generator)
{
auto myGuid = generator.newGuid();
std::stringstream stream;
stream << myGuid;
auto guidString = stream.str();
}
There is also a str()
function that returns a std::string
:
std::string guidStr = xg::newGuid().str();
Creating a guid from raw bytes
It's unlikely that you will need this, but this is done within the library
internally to construct a Guid
object from the raw data given by the system's
built-in guid generation function. There are two key constructors for this:
Guid(std::array<unsigned char, 16> &bytes);
and
Guid(const unsigned char * bytes);
When possible prefer the std::array
constructor because it is safer. If you
pass in an incorrectly sized C array then bad things will happen.
Comparing guids
==
and !=
are implemented, so the following works as expected:
void doGuidStuff(GuidGenerator generator)
{
auto guid1 = generator.newGuid();
auto guid2 = generator.newGuid();
auto guidsAreEqual = guid1 == guid2;
auto guidsAreNotEqual = guid1 != guid2;
}
Linux
The Linux version uses the proprocessor flag GUID_LIBUUID
On linux you can use libuuid which is pretty standard. On distros like Ubuntu it is available by default but to use it you need the header files so you have to do:
sudo apt-get install uuid-dev
Mac/iOS
The Mac and iOS versions use the preprocessor flag GUID_CFUUID
On Mac or iOS you can use CFUUIDCreate
from CoreFoundation
. Since it's a
plain C function you don't even need to compile as Objective-C++.
Windows
The Windows version uses the preprocessor flag GUID_WINDOWS
On Windows we just use the the built-in function CoCreateGuid
. CMake can
generate a Visual Studio project if that's your thing.
Android
The Android version uses the preprocessor flag GUID_ANDROID
The Android version uses a handle to a JNIEnv
object to invoke the
randomUUID()
function on java.util.UUID
from C++. The Android specific code
is all in the android/
subdirectory. If you have an emulator already running,
then you can run the android.sh
script in the root directory. It has the
following requirements:
- Android emulator is already running (or you have physical device connected).
- You're using bash.
- adb is in your path.
- You have an Android sdk setup including
ANDROID_HOME
environment variable.
License
The MIT License (MIT)
Copyright (c) 2014 Graeme Hill (http://graemehill.ca)
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.