forked from lix-project/lix
2d663b502d
prevents files from being evaluated and stored as values multiple times. For instance, evaluation of the ‘system’ attribute in NixOS causes ‘nixpkgs/pkgs/lib/lists.nix’ to be evaluated 2019 times. Caching gives a modest speedup and a decent memory footprint reduction (e.g., from 1.44s to 1.28s, and from 81 MiB to 59 MiB with GC_INITIAL_HEAP_SIZE=100000 on my system).
381 lines
9.5 KiB
C++
381 lines
9.5 KiB
C++
#ifndef __EVAL_H
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#define __EVAL_H
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#include "nixexpr.hh"
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#include "symbol-table.hh"
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#include "hash.hh"
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#include <map>
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#if HAVE_BOEHMGC
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#include <gc/gc_allocator.h>
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#endif
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namespace nix {
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class EvalState;
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struct Env;
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struct Value;
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struct Attr;
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/* Attribute sets are represented as a vector of attributes, sorted by
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symbol (i.e. pointer to the attribute name in the symbol table). */
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#if HAVE_BOEHMGC
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typedef std::vector<Attr, gc_allocator<Attr> > BindingsBase;
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#else
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typedef std::vector<Attr> BindingsBase;
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#endif
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class Bindings : public BindingsBase
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{
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public:
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iterator find(const Symbol & name);
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void sort();
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};
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typedef enum {
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tInt = 1,
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tBool,
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tString,
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tPath,
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tNull,
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tAttrs,
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tList,
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tThunk,
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tApp,
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tLambda,
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tBlackhole,
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tPrimOp,
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tPrimOpApp,
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} ValueType;
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typedef void (* PrimOpFun) (EvalState & state, Value * * args, Value & v);
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struct PrimOp
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{
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PrimOpFun fun;
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unsigned int arity;
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Symbol name;
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PrimOp(PrimOpFun fun, unsigned int arity, Symbol name)
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: fun(fun), arity(arity), name(name) { }
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};
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struct Value
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{
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ValueType type;
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union
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{
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int integer;
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bool boolean;
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/* Strings in the evaluator carry a so-called `context' (the
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ATermList) which is a list of strings representing store
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paths. This is to allow users to write things like
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"--with-freetype2-library=" + freetype + "/lib"
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where `freetype' is a derivation (or a source to be copied
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to the store). If we just concatenated the strings without
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keeping track of the referenced store paths, then if the
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string is used as a derivation attribute, the derivation
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will not have the correct dependencies in its inputDrvs and
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inputSrcs.
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The semantics of the context is as follows: when a string
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with context C is used as a derivation attribute, then the
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derivations in C will be added to the inputDrvs of the
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derivation, and the other store paths in C will be added to
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the inputSrcs of the derivations.
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For canonicity, the store paths should be in sorted order. */
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struct {
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const char * s;
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const char * * context; // must be in sorted order
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} string;
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const char * path;
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Bindings * attrs;
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struct {
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unsigned int length;
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Value * * elems;
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} list;
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struct {
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Env * env;
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Expr * expr;
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} thunk;
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struct {
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Value * left, * right;
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} app;
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struct {
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Env * env;
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ExprLambda * fun;
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} lambda;
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PrimOp * primOp;
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struct {
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Value * left, * right;
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} primOpApp;
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};
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};
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struct Env
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{
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Env * up;
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unsigned int prevWith; // nr of levels up to next `with' environment
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Value * values[0];
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};
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struct Attr
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{
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Symbol name;
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Value * value;
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Pos * pos;
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Attr(Symbol name, Value * value, Pos * pos = &noPos)
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: name(name), value(value), pos(pos) { };
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Attr() : pos(&noPos) { };
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bool operator < (const Attr & a) const
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{
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return name < a.name;
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}
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};
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/* After overwriting an app node, be sure to clear pointers in the
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Value to ensure that the target isn't kept alive unnecessarily. */
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static inline void clearValue(Value & v)
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{
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v.app.right = 0;
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}
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static inline void mkInt(Value & v, int n)
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{
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clearValue(v);
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v.type = tInt;
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v.integer = n;
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}
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static inline void mkBool(Value & v, bool b)
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{
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clearValue(v);
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v.type = tBool;
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v.boolean = b;
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}
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static inline void mkApp(Value & v, Value & left, Value & right)
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{
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v.type = tApp;
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v.app.left = &left;
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v.app.right = &right;
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}
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void mkString(Value & v, const char * s);
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void mkString(Value & v, const string & s, const PathSet & context = PathSet());
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void mkPath(Value & v, const char * s);
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void copyContext(const Value & v, PathSet & context);
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/* Cache for calls to addToStore(); maps source paths to the store
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paths. */
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typedef std::map<Path, Path> SrcToStore;
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struct EvalState;
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std::ostream & operator << (std::ostream & str, const Value & v);
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class EvalState
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{
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public:
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SymbolTable symbols;
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const Symbol sWith, sOutPath, sDrvPath, sType, sMeta, sName,
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sSystem, sOverrides;
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private:
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SrcToStore srcToStore;
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bool allowUnsafeEquality;
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/* A cache from path names to parse trees. */
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std::map<Path, Expr *> parseTrees;
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/* A cache from path names to values. */
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#if HAVE_BOEHMGC
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typedef std::map<Path, Value, std::less<Path>, gc_allocator<std::pair<const Path, Value> > > FileEvalCache;
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#else
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typedef std::map<Path, Value> FileEvalCache;
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#endif
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FileEvalCache fileEvalCache;
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typedef list<std::pair<string, Path> > SearchPath;
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SearchPath searchPath;
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SearchPath::iterator searchPathInsertionPoint;
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public:
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EvalState();
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~EvalState();
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void addToSearchPath(const string & s);
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/* Parse a Nix expression from the specified file. If `path'
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refers to a directory, then "/default.nix" is appended. */
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Expr * parseExprFromFile(Path path);
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/* Parse a Nix expression from the specified string. */
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Expr * parseExprFromString(const string & s, const Path & basePath);
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/* Evaluate an expression read from the given file to normal
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form. */
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void evalFile(const Path & path, Value & v);
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/* Look up a file in the search path. */
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Path findFile(const string & path);
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/* Evaluate an expression to normal form, storing the result in
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value `v'. */
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void eval(Expr * e, Value & v);
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void eval(Env & env, Expr * e, Value & v);
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/* Evaluation the expression, then verify that it has the expected
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type. */
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bool evalBool(Env & env, Expr * e);
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void evalAttrs(Env & env, Expr * e, Value & v);
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/* If `v' is a thunk, enter it and overwrite `v' with the result
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of the evaluation of the thunk. If `v' is a delayed function
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application, call the function and overwrite `v' with the
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result. Otherwise, this is a no-op. */
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void forceValue(Value & v);
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/* Force a value, then recursively force list elements and
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attributes. */
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void strictForceValue(Value & v);
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/* Force `v', and then verify that it has the expected type. */
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int forceInt(Value & v);
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bool forceBool(Value & v);
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void forceAttrs(Value & v);
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void forceList(Value & v);
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void forceFunction(Value & v); // either lambda or primop
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string forceString(Value & v);
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string forceString(Value & v, PathSet & context);
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string forceStringNoCtx(Value & v);
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/* Return true iff the value `v' denotes a derivation (i.e. a
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set with attribute `type = "derivation"'). */
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bool isDerivation(Value & v);
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/* String coercion. Converts strings, paths and derivations to a
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string. If `coerceMore' is set, also converts nulls, integers,
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booleans and lists to a string. If `copyToStore' is set,
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referenced paths are copied to the Nix store as a side effect.q */
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string coerceToString(Value & v, PathSet & context,
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bool coerceMore = false, bool copyToStore = true);
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/* Path coercion. Converts strings, paths and derivations to a
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path. The result is guaranteed to be a canonicalised, absolute
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path. Nothing is copied to the store. */
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Path coerceToPath(Value & v, PathSet & context);
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private:
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/* The base environment, containing the builtin functions and
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values. */
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Env & baseEnv;
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unsigned int baseEnvDispl;
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public:
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/* The same, but used during parsing to resolve variables. */
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StaticEnv staticBaseEnv; // !!! should be private
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private:
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void createBaseEnv();
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void addConstant(const string & name, Value & v);
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void addPrimOp(const string & name,
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unsigned int arity, PrimOpFun primOp);
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Value * lookupVar(Env * env, const VarRef & var);
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friend class ExprVar;
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friend class ExprAttrs;
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friend class ExprLet;
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Expr * parse(const char * text,
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const Path & path, const Path & basePath);
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public:
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/* Do a deep equality test between two values. That is, list
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elements and attributes are compared recursively. */
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bool eqValues(Value & v1, Value & v2);
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void callFunction(Value & fun, Value & arg, Value & v);
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/* Automatically call a function for which each argument has a
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default value or has a binding in the `args' map. */
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void autoCallFunction(Bindings & args, Value & fun, Value & res);
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/* Allocation primitives. */
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Value * allocValue();
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Env & allocEnv(unsigned int size);
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Value * allocAttr(Value & vAttrs, const Symbol & name);
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void mkList(Value & v, unsigned int length);
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void mkAttrs(Value & v, unsigned int expected);
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void mkThunk_(Value & v, Expr * expr);
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Value * maybeThunk(Env & env, Expr * expr);
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/* Print statistics. */
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void printStats();
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private:
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unsigned long nrEnvs;
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unsigned long nrValuesInEnvs;
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unsigned long nrValues;
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unsigned long nrListElems;
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unsigned long nrEvaluated;
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unsigned long nrAttrsets;
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unsigned long nrOpUpdates;
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unsigned long nrOpUpdateValuesCopied;
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unsigned int recursionDepth;
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unsigned int maxRecursionDepth;
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char * deepestStack; /* for measuring stack usage */
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friend class RecursionCounter;
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friend class ExprOpUpdate;
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};
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/* Return a string representing the type of the value `v'. */
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string showType(const Value & v);
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}
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#endif /* !__EVAL_H */
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