1 files changed, 275 insertions, 48 deletions

diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 00d0e3564..d1b4fdbea 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -4,6 +4,7 @@
 #include <map>
 
 #include "nixexpr.hh"
+#include "symbol-table.hh"
 
 typedef union _ATermList * ATermList;
 
@@ -12,9 +13,157 @@ namespace nix {
 
 
 class Hash;
-    
+class EvalState;
+struct Env;
+struct Value;
+struct Attr;
+
+typedef std::map<Symbol, Attr> 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; // 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;
+        Value * val;
+        struct {
+            PrimOp fun;
+            char * name;
+            unsigned int arity;
+        } primOp;
+        struct {
+            Value * left, * right;
+            unsigned int argsLeft;
+        } primOpApp;
+    };
+};
+
+
+struct Env
+{
+    Env * up;
+    unsigned int prevWith; // nr of levels up to next `with' environment
+    Value values[0];
+};
+
+
+struct Attr
+{
+    Value value;
+    Pos * pos;
+    Attr() : pos(&noPos) { };
+};
+
+
+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;
+}
+
+
+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);
+
 
-typedef std::map<Path, PathSet> DrvRoots;
 typedef std::map<Path, Hash> DrvHashes;
 
 /* Cache for calls to addToStore(); maps source paths to the store
@@ -23,75 +172,153 @@ typedef std::map<Path, Path> SrcToStore;
 
 struct EvalState;
 
-/* Note: using a ATermVector is safe here, since when we call a primop
-   we also have an ATermList on the stack. */
-typedef Expr (* PrimOp) (EvalState &, const ATermVector & args);
+
+std::ostream & operator << (std::ostream & str, Value & v);
 
 
-struct EvalState 
+class EvalState 
 {
-    ATermMap normalForms;
-    ATermMap primOps;
-    DrvRoots drvRoots;
+public:
     DrvHashes drvHashes; /* normalised derivation hashes */
-    SrcToStore srcToStore; 
 
-    unsigned int nrEvaluated;
-    unsigned int nrCached;
+    SymbolTable symbols;
+
+    const Symbol sWith, sOutPath, sDrvPath, sType, sMeta, sName, sSystem;
+
+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);
+    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 addPrimOps();
     void addPrimOp(const string & name,
         unsigned int arity, PrimOp primOp);
-};
 
+    Value * lookupVar(Env * env, const VarRef & var);
+    
+    friend class ExprVar;
+    friend class ExprAttrs;
+    friend class ExprLet;
 
-/* Evaluate an expression to normal form. */
-Expr evalExpr(EvalState & state, Expr e);
+public:
+    
+    /* Do a deep equality test between two values.  That is, list
+       elements and attributes are compared recursively. */
+    bool eqValues(Value & v1, Value & v2);
 
-/* Evaluate an expression read from the given file to normal form. */
-Expr evalFile(EvalState & state, const Path & path);
+    void callFunction(Value & fun, Value & arg, Value & v);
 
-/* Evaluate an expression, and recursively evaluate list elements and
-   attributes.  If `canonicalise' is true, we remove things like
-   position information and make sure that attribute sets are in
-   sorded order. */
-Expr strictEvalExpr(EvalState & state, Expr e);
+    /* 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);
 
-/* Specific results. */
-string evalString(EvalState & state, Expr e, PathSet & context);
-string evalStringNoCtx(EvalState & state, Expr e);
-int evalInt(EvalState & state, Expr e);
-bool evalBool(EvalState & state, Expr e);
-ATermList evalList(EvalState & state, Expr e);
+    void mkList(Value & v, unsigned int length);
+    void mkAttrs(Value & v);
+    void mkThunk_(Value & v, Expr * expr);
+    
+    void cloneAttrs(Value & src, Value & dst);
 
-/* Flatten nested lists into a single list (or expand a singleton into
-   a list). */
-ATermList flattenList(EvalState & state, Expr e);
+    /* Print statistics. */
+    void printStats();
 
-/* String coercion.  Converts strings, paths and derivations to a
-   string.  If `coerceMore' is set, also converts nulls, integers,
-   booleans and lists to a string. */
-string coerceToString(EvalState & state, Expr e, PathSet & context,
-    bool coerceMore = false, bool copyToStore = true);
+private:
+    
+    unsigned long nrEnvs;
+    unsigned long nrValuesInEnvs;
+    unsigned long nrValues;
+    unsigned long nrListElems;
+    unsigned long nrEvaluated;
+    unsigned int recursionDepth;
+    unsigned int maxRecursionDepth;
+    char * deepestStack; /* for measuring stack usage */
+    
+    friend class RecursionCounter;
+};
 
-/* Path coercion.  Converts strings, paths and derivations to a path.
-   The result is guaranteed to be an canonicalised, absolute path.
-   Nothing is copied to the store. */
-Path coerceToPath(EvalState & state, Expr e, PathSet & context);
 
-/* Automatically call a function for which each argument has a default
-   value or has a binding in the `args' map.  Note: result is a call,
-   not a normal form; it should be evaluated by calling evalExpr(). */
-Expr autoCallFunction(Expr e, const ATermMap & args);
+/* Return a string representing the type of the value `v'. */
+string showType(const Value & v);
 
-/* Print statistics. */
-void printEvalStats(EvalState & state);
 
- 
 }