eldritch horrors
7c650ea241
eval caches are not used by actual eval at all, only by the flake-shaped wrappers around evaluation. moving caches into a subclass both clarifies that eval caches and eval states are coupled and separates concerns that should not have been intermixed as they were here. in the future we will want to split up and decouple things even further. that'll have to wait. Change-Id: I7b69510c0f8b212f05fae62e7b992d9475b4841f
161 lines
3.5 KiB
C++
161 lines
3.5 KiB
C++
#pragma once
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///@file
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#include "lix/libutil/sync.hh"
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#include "lix/libutil/hash.hh"
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#include "lix/libexpr/eval.hh"
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#include <functional>
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#include <variant>
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namespace nix::eval_cache {
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struct AttrDb;
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class AttrCursor;
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typedef std::function<Value *()> RootLoader;
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/**
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* EvalState with caching support. Historically this was part of EvalState,
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* but it was split out to make maintenance easier. This could've been just
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* a pair of EvalState and the cache map, but doing so would currently hide
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* the rather strong connection between EvalState and these caches. At some
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* future time the cache interface should be changed to hide its EvalState.
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*/
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class CachingEvalState : public EvalState
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{
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/**
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* A cache for evaluation caches, so as to reuse the same root value if possible
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*/
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std::map<Hash, ref<EvalCache>> caches;
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public:
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using EvalState::EvalState;
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ref<EvalCache> getCacheFor(Hash hash, RootLoader rootLoader);
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};
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class EvalCache : public std::enable_shared_from_this<EvalCache>
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{
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friend class AttrCursor;
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std::shared_ptr<AttrDb> db;
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EvalState & state;
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RootLoader rootLoader;
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RootValue value;
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Value * getRootValue();
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public:
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EvalCache(
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std::optional<std::reference_wrapper<const Hash>> useCache,
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EvalState & state,
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RootLoader rootLoader);
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ref<AttrCursor> getRoot();
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};
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enum AttrType {
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Placeholder = 0,
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FullAttrs = 1,
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String = 2,
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Missing = 3,
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Misc = 4,
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Failed = 5,
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Bool = 6,
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ListOfStrings = 7,
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Int = 8,
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};
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struct placeholder_t {};
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struct missing_t {};
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struct misc_t {};
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struct failed_t {};
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struct int_t { NixInt x; };
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typedef uint64_t AttrId;
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typedef std::pair<AttrId, Symbol> AttrKey;
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typedef std::pair<std::string, NixStringContext> string_t;
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typedef std::variant<
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std::vector<Symbol>,
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string_t,
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placeholder_t,
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missing_t,
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misc_t,
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failed_t,
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bool,
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int_t,
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std::vector<std::string>
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> AttrValue;
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class AttrCursor : public std::enable_shared_from_this<AttrCursor>
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{
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friend class EvalCache;
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ref<EvalCache> root;
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typedef std::optional<std::pair<std::shared_ptr<AttrCursor>, Symbol>> Parent;
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Parent parent;
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RootValue _value;
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std::optional<std::pair<AttrId, AttrValue>> cachedValue;
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AttrKey getKey();
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Value & getValue();
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public:
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AttrCursor(
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ref<EvalCache> root,
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Parent parent,
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Value * value = nullptr,
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std::optional<std::pair<AttrId, AttrValue>> && cachedValue = {});
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std::vector<Symbol> getAttrPath() const;
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std::vector<Symbol> getAttrPath(Symbol name) const;
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std::string getAttrPathStr() const;
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std::string getAttrPathStr(Symbol name) const;
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Suggestions getSuggestionsForAttr(Symbol name);
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std::shared_ptr<AttrCursor> maybeGetAttr(Symbol name);
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std::shared_ptr<AttrCursor> maybeGetAttr(std::string_view name);
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ref<AttrCursor> getAttr(Symbol name);
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ref<AttrCursor> getAttr(std::string_view name);
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/**
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* Get an attribute along a chain of attrsets. Note that this does
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* not auto-call functors or functions.
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*/
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OrSuggestions<ref<AttrCursor>> findAlongAttrPath(const std::vector<Symbol> & attrPath);
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std::string getString();
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string_t getStringWithContext();
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bool getBool();
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NixInt getInt();
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std::vector<std::string> getListOfStrings();
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std::vector<Symbol> getAttrs();
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bool isDerivation();
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Value & forceValue();
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/**
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* Force creation of the .drv file in the Nix store.
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*/
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StorePath forceDerivation();
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};
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}
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