nix-super/src/libexpr/value.hh
Eelco Dolstra f9d55b4d51
Merge pull request #11191 from DeterminateSystems/hash-symbol
Use std::unordered_map for ValueMap
2024-07-29 15:30:37 +02:00

513 lines
13 KiB
C++

#pragma once
///@file
#include <cassert>
#include <span>
#include "symbol-table.hh"
#include "value/context.hh"
#include "source-path.hh"
#include "print-options.hh"
#if HAVE_BOEHMGC
#include <gc/gc_allocator.h>
#endif
#include <nlohmann/json_fwd.hpp>
namespace nix {
struct Value;
class BindingsBuilder;
typedef enum {
tUninitialized = 0,
tInt = 1,
tBool,
tString,
tPath,
tNull,
tAttrs,
tList1,
tList2,
tListN,
tThunk,
tApp,
tLambda,
tPrimOp,
tPrimOpApp,
tExternal,
tFloat
} InternalType;
/**
* This type abstracts over all actual value types in the language,
* grouping together implementation details like tList*, different function
* types, and types in non-normal form (so thunks and co.)
*/
typedef enum {
nThunk,
nInt,
nFloat,
nBool,
nString,
nPath,
nNull,
nAttrs,
nList,
nFunction,
nExternal
} ValueType;
class Bindings;
struct Env;
struct Expr;
struct ExprLambda;
struct ExprBlackHole;
struct PrimOp;
class Symbol;
class PosIdx;
struct Pos;
class StorePath;
class EvalState;
class XMLWriter;
class Printer;
typedef int64_t NixInt;
typedef double NixFloat;
/**
* External values must descend from ExternalValueBase, so that
* type-agnostic nix functions (e.g. showType) can be implemented
*/
class ExternalValueBase
{
friend std::ostream & operator << (std::ostream & str, const ExternalValueBase & v);
friend class Printer;
protected:
/**
* Print out the value
*/
virtual std::ostream & print(std::ostream & str) const = 0;
public:
/**
* Return a simple string describing the type
*/
virtual std::string showType() const = 0;
/**
* Return a string to be used in builtins.typeOf
*/
virtual std::string typeOf() const = 0;
/**
* Coerce the value to a string. Defaults to uncoercable, i.e. throws an
* error.
*/
virtual std::string coerceToString(EvalState & state, const PosIdx & pos, NixStringContext & context, bool copyMore, bool copyToStore) const;
/**
* Compare to another value of the same type. Defaults to uncomparable,
* i.e. always false.
*/
virtual bool operator ==(const ExternalValueBase & b) const noexcept;
/**
* Print the value as JSON. Defaults to unconvertable, i.e. throws an error
*/
virtual nlohmann::json printValueAsJSON(EvalState & state, bool strict,
NixStringContext & context, bool copyToStore = true) const;
/**
* Print the value as XML. Defaults to unevaluated
*/
virtual void printValueAsXML(EvalState & state, bool strict, bool location,
XMLWriter & doc, NixStringContext & context, PathSet & drvsSeen,
const PosIdx pos) const;
virtual ~ExternalValueBase()
{
};
};
std::ostream & operator << (std::ostream & str, const ExternalValueBase & v);
class ListBuilder
{
const size_t size;
Value * inlineElems[2] = {nullptr, nullptr};
public:
Value * * elems;
ListBuilder(EvalState & state, size_t size);
ListBuilder(ListBuilder && x)
: size(x.size)
, inlineElems{x.inlineElems[0], x.inlineElems[1]}
, elems(size <= 2 ? inlineElems : x.elems)
{ }
Value * & operator [](size_t n)
{
return elems[n];
}
typedef Value * * iterator;
iterator begin() { return &elems[0]; }
iterator end() { return &elems[size]; }
friend struct Value;
};
struct Value
{
private:
InternalType internalType = tUninitialized;
friend std::string showType(const Value & v);
public:
void print(EvalState &state, std::ostream &str, PrintOptions options = PrintOptions {});
// Functions needed to distinguish the type
// These should be removed eventually, by putting the functionality that's
// needed by callers into methods of this type
// type() == nThunk
inline bool isThunk() const { return internalType == tThunk; };
inline bool isApp() const { return internalType == tApp; };
inline bool isBlackhole() const;
// type() == nFunction
inline bool isLambda() const { return internalType == tLambda; };
inline bool isPrimOp() const { return internalType == tPrimOp; };
inline bool isPrimOpApp() const { return internalType == tPrimOpApp; };
/**
* Strings in the evaluator carry a so-called `context` which
* is a list of strings representing store paths. This is to
* allow users to write things like
*
* "--with-freetype2-library=" + freetype + "/lib"
*
* where `freetype` is a derivation (or a source to be copied
* to the store). If we just concatenated the strings without
* keeping track of the referenced store paths, then if the
* string is used as a derivation attribute, the derivation
* will not have the correct dependencies in its inputDrvs and
* inputSrcs.
* The semantics of the context is as follows: when a string
* with context C is used as a derivation attribute, then the
* derivations in C will be added to the inputDrvs of the
* derivation, and the other store paths in C will be added to
* the inputSrcs of the derivations.
* For canonicity, the store paths should be in sorted order.
*/
struct StringWithContext {
const char * c_str;
const char * * context; // must be in sorted order
};
struct Path {
SourceAccessor * accessor;
const char * path;
};
struct ClosureThunk {
Env * env;
Expr * expr;
};
struct FunctionApplicationThunk {
Value * left, * right;
};
struct Lambda {
Env * env;
ExprLambda * fun;
};
using Payload = union
{
NixInt integer;
bool boolean;
StringWithContext string;
Path path;
Bindings * attrs;
struct {
size_t size;
Value * const * elems;
} bigList;
Value * smallList[2];
ClosureThunk thunk;
FunctionApplicationThunk app;
Lambda lambda;
PrimOp * primOp;
FunctionApplicationThunk primOpApp;
ExternalValueBase * external;
NixFloat fpoint;
};
Payload payload;
/**
* Returns the normal type of a Value. This only returns nThunk if
* the Value hasn't been forceValue'd
*
* @param invalidIsThunk Instead of aborting an an invalid (probably
* 0, so uninitialized) internal type, return `nThunk`.
*/
inline ValueType type(bool invalidIsThunk = false) const
{
switch (internalType) {
case tUninitialized: break;
case tInt: return nInt;
case tBool: return nBool;
case tString: return nString;
case tPath: return nPath;
case tNull: return nNull;
case tAttrs: return nAttrs;
case tList1: case tList2: case tListN: return nList;
case tLambda: case tPrimOp: case tPrimOpApp: return nFunction;
case tExternal: return nExternal;
case tFloat: return nFloat;
case tThunk: case tApp: return nThunk;
}
if (invalidIsThunk)
return nThunk;
else
unreachable();
}
inline void finishValue(InternalType newType, Payload newPayload)
{
payload = newPayload;
internalType = newType;
}
/**
* A value becomes valid when it is initialized. We don't use this
* in the evaluator; only in the bindings, where the slight extra
* cost is warranted because of inexperienced callers.
*/
inline bool isValid() const
{
return internalType != tUninitialized;
}
inline void mkInt(NixInt n)
{
finishValue(tInt, { .integer = n });
}
inline void mkBool(bool b)
{
finishValue(tBool, { .boolean = b });
}
inline void mkString(const char * s, const char * * context = 0)
{
finishValue(tString, { .string = { .c_str = s, .context = context } });
}
void mkString(std::string_view s);
void mkString(std::string_view s, const NixStringContext & context);
void mkStringMove(const char * s, const NixStringContext & context);
inline void mkString(const Symbol & s)
{
mkString(((const std::string &) s).c_str());
}
void mkPath(const SourcePath & path);
void mkPath(std::string_view path);
inline void mkPath(SourceAccessor * accessor, const char * path)
{
finishValue(tPath, { .path = { .accessor = accessor, .path = path } });
}
inline void mkNull()
{
finishValue(tNull, {});
}
inline void mkAttrs(Bindings * a)
{
finishValue(tAttrs, { .attrs = a });
}
Value & mkAttrs(BindingsBuilder & bindings);
void mkList(const ListBuilder & builder)
{
if (builder.size == 1)
finishValue(tList1, { .smallList = { builder.inlineElems[0] } });
else if (builder.size == 2)
finishValue(tList2, { .smallList = { builder.inlineElems[0], builder.inlineElems[1] } });
else
finishValue(tListN, { .bigList = { .size = builder.size, .elems = builder.elems } });
}
inline void mkThunk(Env * e, Expr * ex)
{
finishValue(tThunk, { .thunk = { .env = e, .expr = ex } });
}
inline void mkApp(Value * l, Value * r)
{
finishValue(tApp, { .app = { .left = l, .right = r } });
}
inline void mkLambda(Env * e, ExprLambda * f)
{
finishValue(tLambda, { .lambda = { .env = e, .fun = f } });
}
inline void mkBlackhole();
void mkPrimOp(PrimOp * p);
inline void mkPrimOpApp(Value * l, Value * r)
{
finishValue(tPrimOpApp, { .primOpApp = { .left = l, .right = r } });
}
/**
* For a `tPrimOpApp` value, get the original `PrimOp` value.
*/
const PrimOp * primOpAppPrimOp() const;
inline void mkExternal(ExternalValueBase * e)
{
finishValue(tExternal, { .external = e });
}
inline void mkFloat(NixFloat n)
{
finishValue(tFloat, { .fpoint = n });
}
bool isList() const
{
return internalType == tList1 || internalType == tList2 || internalType == tListN;
}
Value * const * listElems()
{
return internalType == tList1 || internalType == tList2 ? payload.smallList : payload.bigList.elems;
}
std::span<Value * const> listItems() const
{
assert(isList());
return std::span<Value * const>(listElems(), listSize());
}
Value * const * listElems() const
{
return internalType == tList1 || internalType == tList2 ? payload.smallList : payload.bigList.elems;
}
size_t listSize() const
{
return internalType == tList1 ? 1 : internalType == tList2 ? 2 : payload.bigList.size;
}
PosIdx determinePos(const PosIdx pos) const;
/**
* Check whether forcing this value requires a trivial amount of
* computation. In particular, function applications are
* non-trivial.
*/
bool isTrivial() const;
SourcePath path() const
{
assert(internalType == tPath);
return SourcePath(
ref(payload.path.accessor->shared_from_this()),
CanonPath(CanonPath::unchecked_t(), payload.path.path));
}
std::string_view string_view() const
{
assert(internalType == tString);
return std::string_view(payload.string.c_str);
}
const char * c_str() const
{
assert(internalType == tString);
return payload.string.c_str;
}
const char * * context() const
{
return payload.string.context;
}
ExternalValueBase * external() const
{ return payload.external; }
const Bindings * attrs() const
{ return payload.attrs; }
const PrimOp * primOp() const
{ return payload.primOp; }
bool boolean() const
{ return payload.boolean; }
NixInt integer() const
{ return payload.integer; }
NixFloat fpoint() const
{ return payload.fpoint; }
};
extern ExprBlackHole eBlackHole;
bool Value::isBlackhole() const
{
return internalType == tThunk && payload.thunk.expr == (Expr*) &eBlackHole;
}
void Value::mkBlackhole()
{
mkThunk(nullptr, (Expr *) &eBlackHole);
}
#if HAVE_BOEHMGC
typedef std::vector<Value *, traceable_allocator<Value *>> ValueVector;
typedef std::unordered_map<Symbol, Value *, std::hash<Symbol>, std::equal_to<Symbol>, traceable_allocator<std::pair<const Symbol, Value *>>> ValueMap;
typedef std::map<Symbol, ValueVector, std::less<Symbol>, traceable_allocator<std::pair<const Symbol, ValueVector>>> ValueVectorMap;
#else
typedef std::vector<Value *> ValueVector;
typedef std::unordered_map<Symbol, Value *> ValueMap;
typedef std::map<Symbol, ValueVector> ValueVectorMap;
#endif
/**
* A value allocated in traceable memory.
*/
typedef std::shared_ptr<Value *> RootValue;
RootValue allocRootValue(Value * v);
}