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BLE: Enable getting an implicitly-created CCCD through GattCharacteristic::getDescriptor #13729

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Merged
merged 5 commits into from
Oct 13, 2020
Merged

BLE: Enable getting an implicitly-created CCCD through GattCharacteristic::getDescriptor #13729

merged 5 commits into from
Oct 13, 2020

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AGlass0fMilk
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@AGlass0fMilk AGlass0fMilk commented Oct 6, 2020 •
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Summary of changes

See #13581 for information on issue.

Resolves #13581 by allowing the GattServer to pass a pointer to an implicitly-created CCCD. This GattAttribute is dynamically allocated (using new) and ownership is transferred to the relevant GattCharacteristic, which takes care of deleteing the GattAttribute in its destructor.

I tried to make GattServer a friend class of GattCharacteristic so GattCharacteristic::_setImplicitCCCD could be private, but I wasn't able to get it to compile due to all the weird namespacing stuff going on with ble::GattServer and ble::impl::GattServer -- it boggled my mind so I just made this a public "internal" function.

Impact of changes

GattCharacteristic::getDescriptor and GattCharacteristic::getDescriptorCount now behave as expected when a GattCharacteristic has an implicitly-created CCCD (ie: the GattCharacteristic has indicate and/or notify as one of its properties).

Migration actions required

None

Documentation

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Pull request type 

[X] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[] Feature update (New feature / Functionality change / New API)
[] Major update (Breaking change E.g. Return code change / API behaviour change)

Test results 

[] No Tests required for this change (E.g docs only update)
[X] Covered by existing mbed-os tests (Greentea or Unittest)
[] Tests / results supplied as part of this PR

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@pan- @paul-szczepanek-arm

@AGlass0fMilk AGlass0fMilk changed the title Enabled getting an implicitly-created CCCD through GattCharacteristic::getDescriptor Enable getting an implicitly-created CCCD through GattCharacteristic::getDescriptor Oct 6, 2020
@ciarmcom ciarmcom added the release-type: patch Indentifies a PR as containing just a patch label Oct 6, 2020
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ciarmcom commented Oct 6, 2020

@AGlass0fMilk, thank you for your changes.
@pan- @paul-szczepanek-arm @ARMmbed/mbed-os-maintainers please review.

@ciarmcom ciarmcom requested review from pan-, paul-szczepanek-arm and a team October 6, 2020 23:30
@AGlass0fMilk AGlass0fMilk changed the title Enable getting an implicitly-created CCCD through GattCharacteristic::getDescriptor [BLE] Enable getting an implicitly-created CCCD through GattCharacteristic::getDescriptor Oct 6, 2020
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pan- reviewed Oct 7, 2020
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Good PR. Thanks @AGlass0fMilk .

I tried to make GattServer a friend class of GattCharacteristic so GattCharacteristic::_setImplicitCCCD could be private, but I wasn't able to get it to compile due to all the weird namespacing stuff going on with ble::GattServer and ble::impl::GattServer -- it boggled my mind so I just made this a public "internal" function.

In C++, friendship is not inherited. The solution is to:

  • Forward declare ble::GattServer in GattCharacteristic.h
  • Mark it friend in GattCharacteristic (friend ble::GattCharacteristic)
  • Add a protected function in ble::GattServer that can be used by child to add the CCCD. setCharacteristicImplicitCCCD(GattCharacteristic&, GattAttribute*)

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Good PR. Thanks @AGlass0fMilk .

I tried to make GattServer a friend class of GattCharacteristic so GattCharacteristic::_setImplicitCCCD could be private, but I wasn't able to get it to compile due to all the weird namespacing stuff going on with ble::GattServer and ble::impl::GattServer -- it boggled my mind so I just made this a public "internal" function.

In C++, friendship is not inherited. The solution is to:

* Forward declare `ble::GattServer` in `GattCharacteristic.h`

* Mark it friend in `GattCharacteristic` (`friend ble::GattCharacteristic`)

* Add a protected function in `ble::GattServer` that can be used by child to add the CCCD. `setCharacteristicImplicitCCCD(GattCharacteristic&, GattAttribute*)`

It turns out that ble::impl::GattServer is not actually a child class of ble::GattServer. So I simply had to forward declare ble::impl::GattServer and then declare it as a friend in the GattCharacteristic declaration.

My problems stemmed from me trying to forward declare only impl::GattServer... does not name a type 🙄

I moved the forward declaration outside of the GattCharacteristic class body, similar to what I saw in GattServer.h and it compiles fine now. A much cleaner implementation 👍

Let me know if anything else needs to be addressed.

pan-
pan- previously approved these changes Oct 9, 2020
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Looks good, I request a minor change in the allocation of the CCCD attribute. After that it is good to go.

@mergify mergify bot added needs: CI and removed needs: review labels Oct 9, 2020
@mergify mergify bot dismissed pan-’s stale review October 9, 2020 13:47

Pull request has been modified.

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pan- approved these changes Oct 9, 2020
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LGTM

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0xc0170 commented Oct 13, 2020

CI started

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mbed-ci commented Oct 13, 2020

Jenkins CI Test : ✔️ SUCCESS

Build Number: 1 | 🔒 Jenkins CI Job | 🌐 Logs & Artifacts

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jobs Status
jenkins-ci/mbed-os-ci_unittests ✔️
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jenkins-ci/mbed-os-ci_dynamic-memory-usage ✔️
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@0xc0170 0xc0170 changed the title [BLE] Enable getting an implicitly-created CCCD through GattCharacteristic::getDescriptor BLE: Enable getting an implicitly-created CCCD through GattCharacteristic::getDescriptor Oct 13, 2020
@0xc0170 0xc0170 merged commit 35f97f4 into ARMmbed:master Oct 13, 2020
@mbedmain mbedmain added release-version: 6.4.0 Release-pending and removed release-type: patch Indentifies a PR as containing just a patch Release-pending labels Oct 20, 2020
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@pan- pan- pan- approved these changes

@0xc0170 0xc0170 0xc0170 approved these changes

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BLE: Intrinsically created descriptors (ie: CCCD) not accessible thru GattCharacteristic::getDescriptor()
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