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72 lines
2.3 KiB
C++
72 lines
2.3 KiB
C++
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_Viaduct_h
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#define mozilla_Viaduct_h
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#include "mozIViaduct.h"
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#include "mozilla/Atomics.h"
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/**
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* Viaduct is a way for Application Services Rust components
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* (https://github.com/mozilla/application-services) to make network requests
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* using a trusted stack (gecko).
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*
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* The way it works is roughly as follows:
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* - First we register a callback using `viaduct_initialize`
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* (Viaduct::Initialize). This callback is stored on the Rust side
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* in a static variable, therefore Initialize() must be called only once.
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*
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* - When the Rust code needs to make a network request, our callback
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* (Viaduct::ViaductCallback) will be called with a protocol buffer describing
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* the request to make on their behalf. Note 1: The callback MUST be called from
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* a background thread as it is blocking. Note 2: It is our side responsibility
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* to call `viaduct_destroy_bytebuffer` on the buffer.
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*
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* - We set a semaphore to make the background thread wait while we make the
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* request on the main thread using nsIChannel. (ViaductRequest::MakeRequest)
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*
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* - Once a response is received, we allocate a bytebuffer to store the
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* response using `viaduct_alloc_bytebuffer` and unlock the semaphore.
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* (ViaductRequest::OnStopRequest)
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*
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* - The background thread is unlocked, and the callback returns the response to
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* the Rust caller. (Viaduct::ViaductCallback)
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*
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* - The Rust caller will free the response buffer we allocated earlier.
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*
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* Reference:
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* https://github.com/mozilla/application-services/blob/master/components/viaduct/README.md
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*/
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namespace mozilla {
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namespace {
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// A mapping of the ByteBuffer repr(C) Rust struct.
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typedef struct ViaductByteBuffer {
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int64_t len;
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uint8_t* data;
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} ViaductByteBuffer;
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} // namespace
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class Viaduct final : public mozIViaduct {
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public:
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NS_DECL_THREADSAFE_ISUPPORTS
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NS_DECL_MOZIVIADUCT
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Viaduct() : mInitialized(false) {}
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static already_AddRefed<Viaduct> GetSingleton();
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private:
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static ViaductByteBuffer ViaductCallback(ViaductByteBuffer buffer);
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Atomic<bool> mInitialized;
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~Viaduct() = default;
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};
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}; // namespace mozilla
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#endif // mozilla_Viaduct_h
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