lix/src/libexpr/eval.hh
Eelco Dolstra c7101dac0b * Allow redirections in search path entries. E.g. if you have a
directory

    /home/eelco/src/stdenv-updates

  that you want to use as the directory for import such as

    with (import <nixpkgs> { });

  then you can say

    $ nix-build -I nixpkgs=/home/eelco/src/stdenv-updates
2011-08-06 17:48:57 +00:00

372 lines
9.1 KiB
C++

#ifndef __EVAL_H
#define __EVAL_H
#include "nixexpr.hh"
#include "symbol-table.hh"
#include "hash.hh"
#include <map>
#if HAVE_BOEHMGC
#include <gc/gc_allocator.h>
#endif
namespace nix {
class EvalState;
struct Env;
struct Value;
struct Attr;
/* Attribute sets are represented as a vector of attributes, sorted by
symbol (i.e. pointer to the attribute name in the symbol table). */
#if HAVE_BOEHMGC
typedef std::vector<Attr, gc_allocator<Attr> > BindingsBase;
#else
typedef std::vector<Attr> BindingsBase;
#endif
class Bindings : public BindingsBase
{
public:
iterator find(const Symbol & name);
void sort();
};
typedef enum {
tInt = 1,
tBool,
tString,
tPath,
tNull,
tAttrs,
tList,
tThunk,
tApp,
tLambda,
tBlackhole,
tPrimOp,
tPrimOpApp,
} ValueType;
typedef void (* PrimOpFun) (EvalState & state, Value * * args, Value & v);
struct PrimOp
{
PrimOpFun fun;
unsigned int arity;
Symbol name;
PrimOp(PrimOpFun fun, unsigned int arity, Symbol name)
: fun(fun), arity(arity), name(name) { }
};
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; // must be in sorted order
} 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;
PrimOp * primOp;
struct {
Value * left, * right;
} primOpApp;
};
};
struct Env
{
Env * up;
unsigned int prevWith; // nr of levels up to next `with' environment
Value * values[0];
};
struct Attr
{
Symbol name;
Value * value;
Pos * pos;
Attr(Symbol name, Value * value, Pos * pos = &noPos)
: name(name), value(value), pos(pos) { };
Attr() : pos(&noPos) { };
bool operator < (const Attr & a) const
{
return name < a.name;
}
};
/* After overwriting an app node, be sure to clear pointers in the
Value to ensure that the target isn't kept alive unnecessarily. */
static inline void clearValue(Value & v)
{
v.app.right = 0;
}
static inline void mkInt(Value & v, int n)
{
clearValue(v);
v.type = tInt;
v.integer = n;
}
static inline void mkBool(Value & v, bool b)
{
clearValue(v);
v.type = tBool;
v.boolean = b;
}
static inline void mkApp(Value & v, Value & left, Value & right)
{
v.type = tApp;
v.app.left = &left;
v.app.right = &right;
}
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);
void copyContext(const Value & v, PathSet & context);
/* 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, const Value & v);
class EvalState
{
public:
SymbolTable symbols;
const Symbol sWith, sOutPath, sDrvPath, sType, sMeta, sName,
sSystem, sOverrides;
private:
SrcToStore srcToStore;
bool allowUnsafeEquality;
std::map<Path, Expr *> parseTrees;
typedef list<std::pair<string, Path> > SearchPath;
SearchPath searchPath;
SearchPath::iterator searchPathInsertionPoint;
public:
EvalState();
~EvalState();
void addToSearchPath(const string & s);
/* Parse a Nix expression from the specified file. If `path'
refers to a directory, then "/default.nix" is appended. */
Expr * parseExprFromFile(Path path);
/* Parse a Nix expression from the specified string. */
Expr * parseExprFromString(const string & s, const Path & basePath);
/* Evaluate an expression read from the given file to normal
form. */
void evalFile(const Path & path, Value & v);
/* Look up a file in the search path. */
Path findFile(const string & path);
/* 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);
void evalAttrs(Env & env, Expr * e, Value & v);
/* 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;
unsigned int baseEnvDispl;
public:
/* The same, but used during parsing to resolve variables. */
StaticEnv staticBaseEnv; // !!! should be private
private:
void createBaseEnv();
void addConstant(const string & name, Value & v);
void addPrimOp(const string & name,
unsigned int arity, PrimOpFun primOp);
Value * lookupVar(Env * env, const VarRef & var);
friend class ExprVar;
friend class ExprAttrs;
friend class ExprLet;
Expr * parse(const char * text,
const Path & path, const Path & basePath);
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(Bindings & args, Value & fun, Value & res);
/* Allocation primitives. */
Value * allocValue();
Env & allocEnv(unsigned int size);
Value * allocAttr(Value & vAttrs, const Symbol & name);
void mkList(Value & v, unsigned int length);
void mkAttrs(Value & v, unsigned int expected);
void mkThunk_(Value & v, Expr * expr);
Value * maybeThunk(Env & env, Expr * expr);
/* Print statistics. */
void printStats();
private:
unsigned long nrEnvs;
unsigned long nrValuesInEnvs;
unsigned long nrValues;
unsigned long nrListElems;
unsigned long nrEvaluated;
unsigned long nrAttrsets;
unsigned long nrOpUpdates;
unsigned long nrOpUpdateValuesCopied;
unsigned int recursionDepth;
unsigned int maxRecursionDepth;
char * deepestStack; /* for measuring stack usage */
friend class RecursionCounter;
friend class ExprOpUpdate;
};
/* Return a string representing the type of the value `v'. */
string showType(const Value & v);
}
#endif /* !__EVAL_H */