Method push

fdbserver/DiskQueue.actor.cpp:894–913

	    nextReadLocation(-1), readBufPage(nullptr), readBufPos(0) {}

	location push(StringRef contents) override {
		ASSERT(recovered);
		uint8_t const* begin = contents.begin();
		uint8_t const* end = contents.end();
		CODE_PROBE(contents.size() && pushedPageCount(), "More than one push between commits");

		bool pushAtEndOfPage = contents.size() >= 4 && pushedPageCount() && backPage().remainingCapacity() < 4;
		CODE_PROBE(pushAtEndOfPage, "Push right at the end of a page, possibly splitting size");
		while (begin != end) {
			if (!pushedPageCount() || !backPage().remainingCapacity())
				addEmptyPage();

			auto& p = backPage();
			int s = std::min<int>(p.remainingCapacity(), end - begin);
			memcpy(p.payload + p.payloadSize, begin, s);
			p.payloadSize += s;
			begin += s;
		}
		return endLocation();
	}

	void pop(location upTo) override {
		ASSERT(!upTo.hi);