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