lix/src/libexpr/eval.hh
Eelco Dolstra 9985230c00 * After parsing, compute level/displacement pairs for each variable
use site, allowing environments to be stores as vectors of values
  rather than maps.  This should speed up evaluation and reduce the
  number of allocations.
2010-04-14 14:42:32 +00:00

293 lines
7 KiB
C++

#ifndef __EVAL_H
#define __EVAL_H
#include <map>
#include "nixexpr.hh"
#include "symbol-table.hh"
namespace nix {
class Hash;
class EvalState;
struct Env;
struct Value;
typedef std::map<Symbol, Value> Bindings;
typedef enum {
tInt = 1,
tBool,
tString,
tPath,
tNull,
tAttrs,
tList,
tThunk,
tApp,
tLambda,
tCopy,
tBlackhole,
tPrimOp,
tPrimOpApp,
} ValueType;
typedef void (* PrimOp) (EvalState & state, Value * * args, Value & v);
struct Value
{
ValueType type;
union
{
int integer;
bool boolean;
/* Strings in the evaluator carry a so-called `context' (the
ATermList) 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 {
const char * s;
const char * * context;
} string;
const char * path;
Bindings * attrs;
struct {
unsigned int length;
Value * elems;
} list;
struct {
Env * env;
Expr * expr;
} thunk;
struct {
Value * left, * right;
} app;
struct {
Env * env;
ExprLambda * fun;
} lambda;
Value * val;
struct {
PrimOp fun;
unsigned int arity;
} primOp;
struct {
Value * left, * right;
unsigned int argsLeft;
} primOpApp;
};
};
struct Env
{
Env * up;
Value values[0];
};
static inline void mkInt(Value & v, int n)
{
v.type = tInt;
v.integer = n;
}
static inline void mkBool(Value & v, bool b)
{
v.type = tBool;
v.boolean = b;
}
static inline void mkThunk(Value & v, Env & env, Expr * expr)
{
v.type = tThunk;
v.thunk.env = &env;
v.thunk.expr = expr;
}
static inline void mkCopy(Value & v, Value & src)
{
v.type = tCopy;
v.val = &src;
}
void mkString(Value & v, const char * s);
void mkString(Value & v, const string & s, const PathSet & context = PathSet());
void mkPath(Value & v, const char * s);
typedef std::map<Path, Hash> DrvHashes;
/* Cache for calls to addToStore(); maps source paths to the store
paths. */
typedef std::map<Path, Path> SrcToStore;
struct EvalState;
std::ostream & operator << (std::ostream & str, Value & v);
class EvalState
{
public:
DrvHashes drvHashes; /* normalised derivation hashes */
SymbolTable symbols;
const Symbol sWith, sOutPath, sDrvPath, sType, sMeta, sName;
private:
SrcToStore srcToStore;
bool allowUnsafeEquality;
std::map<Path, Expr *> parseTrees;
public:
EvalState();
~EvalState();
/* Evaluate an expression read from the given file to normal
form. */
void evalFile(const Path & path, Value & v);
/* Evaluate an expression to normal form, storing the result in
value `v'. */
void eval(Expr * e, Value & v);
void eval(Env & env, Expr * e, Value & v);
/* Evaluation the expression, then verify that it has the expected
type. */
bool evalBool(Env & env, Expr * e);
/* If `v' is a thunk, enter it and overwrite `v' with the result
of the evaluation of the thunk. If `v' is a delayed function
application, call the function and overwrite `v' with the
result. Otherwise, this is a no-op. */
void forceValue(Value & v);
/* Force a value, then recursively force list elements and
attributes. */
void strictForceValue(Value & v);
/* Force `v', and then verify that it has the expected type. */
int forceInt(Value & v);
bool forceBool(Value & v);
void forceAttrs(Value & v);
void forceList(Value & v);
void forceFunction(Value & v); // either lambda or primop
string forceString(Value & v);
string forceString(Value & v, PathSet & context);
string forceStringNoCtx(Value & v);
/* Return true iff the value `v' denotes a derivation (i.e. a
set with attribute `type = "derivation"'). */
bool isDerivation(Value & v);
/* String coercion. Converts strings, paths and derivations to a
string. If `coerceMore' is set, also converts nulls, integers,
booleans and lists to a string. If `copyToStore' is set,
referenced paths are copied to the Nix store as a side effect.q */
string coerceToString(Value & v, PathSet & context,
bool coerceMore = false, bool copyToStore = true);
/* Path coercion. Converts strings, paths and derivations to a
path. The result is guaranteed to be a canonicalised, absolute
path. Nothing is copied to the store. */
Path coerceToPath(Value & v, PathSet & context);
private:
/* The base environment, containing the builtin functions and
values. */
Env & baseEnv;
void createBaseEnv();
void addConstant(const string & name, Value & v);
void addPrimOp(const string & name,
unsigned int arity, PrimOp primOp);
Value * lookupVar(Env * env, const Symbol & name);
friend class ExprVar;
friend class ExprAttrs;
friend class ExprLet;
public:
/* Do a deep equality test between two values. That is, list
elements and attributes are compared recursively. */
bool eqValues(Value & v1, Value & v2);
void callFunction(Value & fun, Value & arg, Value & v);
/* Automatically call a function for which each argument has a
default value or has a binding in the `args' map. */
void autoCallFunction(const Bindings & args, Value & fun, Value & res);
/* Allocation primitives. */
Value * allocValues(unsigned int count);
Env & allocEnv(unsigned int size);
void mkList(Value & v, unsigned int length);
void mkAttrs(Value & v);
void mkThunk_(Value & v, Expr * expr);
void cloneAttrs(Value & src, Value & dst);
/* Print statistics. */
void printStats();
private:
unsigned long nrValues;
unsigned long nrEnvs;
unsigned long nrEvaluated;
unsigned int recursionDepth;
unsigned int maxRecursionDepth;
char * deepestStack; /* for measuring stack usage */
friend class RecursionCounter;
};
/* Return a string representing the type of the value `v'. */
string showType(Value & v);
}
#endif /* !__EVAL_H */