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Backport https://github.com/NixOS/nix/pull/11152

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This commit is contained in:
Eelco Dolstra 2024-08-23 13:15:30 +02:00
parent 79a43160ca
commit 30a57328d2
5 changed files with 15 additions and 231 deletions
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71
src/libutil/serialise.cc
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@ -171,55 +171,6 @@ size_t StringSource::read(char * data, size_t len)
#error Coroutines are broken in this version of Boost!
#endif
/* A concrete datatype allow virtual dispatch of stack allocation methods. */
struct VirtualStackAllocator {
StackAllocator *allocator = StackAllocator::defaultAllocator;
boost::context::stack_context allocate() {
return allocator->allocate();
}
void deallocate(boost::context::stack_context sctx) {
allocator->deallocate(sctx);
}
};
/* This class reifies the default boost coroutine stack allocation strategy with
a virtual interface. */
class DefaultStackAllocator : public StackAllocator {
boost::coroutines2::default_stack stack;
boost::context::stack_context allocate() override {
return stack.allocate();
}
void deallocate(boost::context::stack_context sctx) override {
stack.deallocate(sctx);
}
};
static DefaultStackAllocator defaultAllocatorSingleton;
StackAllocator *StackAllocator::defaultAllocator = &defaultAllocatorSingleton;
std::shared_ptr<void> (*create_coro_gc_hook)() = []() -> std::shared_ptr<void> {
return {};
};
/* This class is used for entry and exit hooks on coroutines */
class CoroutineContext {
/* Disable GC when entering the coroutine without the boehm patch,
* since it doesn't find the main thread stack in this case.
* std::shared_ptr<void> performs type-erasure, so it will call the right
* deleter. */
const std::shared_ptr<void> coro_gc_hook = create_coro_gc_hook();
public:
CoroutineContext() {};
~CoroutineContext() {};
};
std::unique_ptr<FinishSink> sourceToSink(std::function<void(Source &)> fun)
{
struct SourceToSink : FinishSink
@ -241,14 +192,12 @@ std::unique_ptr<FinishSink> sourceToSink(std::function<void(Source &)> fun)
cur = in;
if (!coro) {
CoroutineContext ctx;
coro = coro_t::push_type(VirtualStackAllocator{}, [&](coro_t::pull_type & yield) {
LambdaSource source([&](char *out, size_t out_len) {
coro = coro_t::push_type([&](coro_t::pull_type & yield) {
LambdaSource source([&](char * out, size_t out_len) {
if (cur.empty()) {
yield();
if (yield.get()) {
return (size_t)0;
}
if (yield.get())
throw EndOfFile("coroutine has finished");
}
size_t n = std::min(cur.size(), out_len);
@ -263,20 +212,14 @@ std::unique_ptr<FinishSink> sourceToSink(std::function<void(Source &)> fun)
if (!*coro) { unreachable(); }
if (!cur.empty()) {
CoroutineContext ctx;
(*coro)(false);
}
}
void finish() override
{
if (!coro) return;
if (!*coro) unreachable();
{
CoroutineContext ctx;
if (coro && *coro)
(*coro)(true);
}
if (*coro) unreachable();
}
};
@ -307,8 +250,7 @@ std::unique_ptr<Source> sinkToSource(
size_t read(char * data, size_t len) override
{
if (!coro) {
CoroutineContext ctx;
coro = coro_t::pull_type(VirtualStackAllocator{}, [&](coro_t::push_type & yield) {
coro = coro_t::pull_type([&](coro_t::push_type & yield) {
LambdaSink sink([&](std::string_view data) {
if (!data.empty()) yield(std::string(data));
});
@ -320,7 +262,6 @@ std::unique_ptr<Source> sinkToSource(
if (pos == cur.size()) {
if (!cur.empty()) {
CoroutineContext ctx;
(*coro)();
}
cur = coro->get();