* Realisation of File(...) expressions.
This commit is contained in:
Eelco Dolstra
parent
bb03c45ca0
commit
3da9687854
11 changed files with 137 additions and 368 deletions
274
src/eval.cc
274
src/eval.cc
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@ -30,6 +30,7 @@ bool pathExists(string path)
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}
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#if 0
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/* Compute a derived value by running a program. */
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static Hash computeDerived(Hash sourceHash, string targetName,
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string platform, Hash prog, Environment env)
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@ -175,6 +176,7 @@ static Hash computeDerived(Hash sourceHash, string targetName,
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return targetHash;
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}
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#endif
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/* Throw an exception if the given platform string is not supported by
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@ -182,54 +184,32 @@ static Hash computeDerived(Hash sourceHash, string targetName,
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static void checkPlatform(string platform)
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{
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if (platform != thisSystem)
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throw Error("a `" + platform +
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"' is required, but I am a `" + thisSystem + "'");
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throw Error(format("a `%1%' is required, but I am a `%2%'")
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% platform % thisSystem);
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}
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string printExpr(Expr e)
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string printTerm(ATerm t)
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{
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char * s = ATwriteToString(e);
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char * s = ATwriteToString(t);
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return s;
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}
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/* Throw an exception with an error message containing the given
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aterm. */
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static Error badTerm(const string & msg, Expr e)
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static Error badTerm(const format & f, ATerm t)
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{
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return Error(msg + ", in `" + printExpr(e) + "'");
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return Error(format("%1%, in `%2%'") % f.str() % printTerm(t));
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}
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Hash hashExpr(Expr e)
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Hash hashTerm(ATerm t)
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{
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return hashString(printExpr(e));
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return hashString(printTerm(t));
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}
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/* Evaluate an expression; the result must be a string. */
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static string evalString(Expr e)
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{
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e = whNormalise(e);
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char * s;
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if (ATmatch(e, "Str(<str>)", &s)) return s;
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else throw badTerm("string value expected", e);
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}
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#if 0
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/* Evaluate an expression; the result must be a value reference. */
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static Hash evalHash(Expr e)
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{
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e = evalValue(e);
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char * s;
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if (ATmatch(e, "Hash(<str>)", &s)) return parseHash(s);
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else throw badTerm("value reference expected", e);
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}
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#endif
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#if 0
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/* Evaluate a list of arguments into normal form. */
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void evalArgs(ATermList args, ATermList & argsNF, Environment & env)
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@ -262,225 +242,63 @@ void evalArgs(ATermList args, ATermList & argsNF, Environment & env)
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#endif
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Expr substExpr(string x, Expr rep, Expr e)
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{
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char * s;
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Expr e2;
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if (ATmatch(e, "Var(<str>)", &s))
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if (x == s)
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return rep;
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else
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return e;
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if (ATmatch(e, "Lam(<str>, <term>)", &s, &e2))
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if (x == s)
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return e;
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/* !!! unfair substitutions */
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/* Generically substitute in subterms. */
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if (ATgetType(e) == AT_APPL) {
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AFun fun = ATgetAFun(e);
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int arity = ATgetArity(fun);
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ATermList args = ATempty;
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for (int i = arity - 1; i >= 0; i--)
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args = ATinsert(args, substExpr(x, rep, ATgetArgument(e, i)));
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return (ATerm) ATmakeApplList(fun, args);
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}
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if (ATgetType(e) == AT_LIST) {
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ATermList in = (ATermList) e;
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ATermList out = ATempty;
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while (!ATisEmpty(in)) {
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out = ATinsert(out, substExpr(x, rep, ATgetFirst(in)));
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in = ATgetNext(in);
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}
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return (ATerm) ATreverse(out);
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}
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throw badTerm("do not know how to substitute", e);
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}
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#if 0
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Expr evalValue(Expr e)
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{
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char * s;
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Expr eBuildPlatform, eProg, e2, e3, e4;
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ATermList args;
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/* Value references. */
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if (ATmatch(e, "Hash(<str>)", &s)) {
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parseHash(s); /* i.e., throw exception if not valid */
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return e;
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}
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/* External expression. */
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if (ATmatch(e, "Deref(<term>)", &e2)) {
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string fn = queryValuePath(evalHash(e2));
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ATerm e3 = ATreadFromNamedFile(fn.c_str());
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if (!e3) throw Error("reading aterm from " + fn);
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return evalValue(e3);
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}
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/* Execution primitive. */
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if (ATmatch(e, "Exec(<term>, <term>, [<list>])",
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&eBuildPlatform, &eProg, &args))
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{
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string buildPlatform = evalString(eBuildPlatform);
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checkPlatform(buildPlatform);
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Hash prog = evalHash(eProg);
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Environment env;
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ATermList argsNF;
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evalArgs(args, argsNF, env);
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Hash sourceHash = hashExpr(
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ATmake("Exec(Str(<str>), Hash(<str>), <term>)",
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buildPlatform.c_str(), ((string) prog).c_str(), argsNF));
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/* Do we know a normal form for sourceHash? */
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Hash targetHash;
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string targetHashS;
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if (queryDB(nixDB, dbNFs, sourceHash, targetHashS)) {
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/* Yes. */
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targetHash = parseHash(targetHashS);
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debug("already built: " + (string) sourceHash
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+ " -> " + (string) targetHash);
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} else {
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/* No, so we compute one. */
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targetHash = computeDerived(sourceHash,
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(string) sourceHash + "-nf", buildPlatform, prog, env);
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}
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return ATmake("Hash(<str>)", ((string) targetHash).c_str());
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}
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/* Barf. */
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throw badTerm("invalid expression", e);
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}
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#endif
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Expr whNormalise(Expr e)
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{
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char * s;
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Expr e2, e3, e4, e5;
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/* Normal forms. */
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if (ATmatch(e, "Str(<str>)", &s) ||
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ATmatch(e, "Bool(True)") ||
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ATmatch(e, "Bool(False)") ||
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ATmatch(e, "Lam(<str>, <term>)", &s, &e2) ||
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ATmatch(e, "File(<str>, <term>, <term>)", &s, &e2, &e3) ||
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ATmatch(e, "Derive(<term>, <term>, <term>, <term>)", &e2, &e3, &e4, &e5))
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return e;
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/* Application. */
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if (ATmatch(e, "App(<term>, <term>)", &e2, &e3)) {
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e2 = whNormalise(e2);
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if (!ATmatch(e2, "Lam(<str>, <term>)", &s, &e4))
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throw badTerm("expecting lambda", e2);
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return whNormalise(substExpr(s, e3, e4));
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}
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throw badTerm("invalid expression", e);
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}
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Expr dNormalise(Expr e)
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{
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e = whNormalise(e);
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/* !!! todo */
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return e;
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}
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Expr fNormalise(Expr e)
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{
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e = dNormalise(e);
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char * s;
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Expr e2, e3;
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if (ATmatch(e, "File(<str>, <term>, [<list>])", &s, &e2, &e3)) {
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ATermList refs = (ATermList) e3, refs2 = ATempty;
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while (!ATisEmpty(refs)) {
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ATerm ref = ATgetFirst(refs);
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refs2 = ATinsert(refs2, fNormalise(ref));
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refs = ATgetNext(refs);
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}
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refs2 = ATreverse(refs2);
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return ATmake("File(<str>, <term>, <term>)", s, e2, refs2);
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}
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else return e;
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}
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void writeContent(string path, Content content)
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{
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char * s;
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if (ATmatch(content, "Regular(<str>)", &s)) {
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int fd; /* !!! close on exception */
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fd = open(path.c_str(), O_CREAT | O_EXCL | O_WRONLY, 0666);
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if (fd == -1)
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throw SysError("creating file " + path);
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int len = strlen(s);
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if (write(fd, s, len) != len)
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throw SysError("writing file " + path);
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close(fd);
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}
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else throw badTerm("ill-formed content", content);
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}
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struct RStatus
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{
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/* !!! the comparator of this hash should match the semantics of
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the file system */
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map<string, Hash> paths;
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// map<string, Hash> paths;
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};
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static void realise2(RStatus & status, Expr e)
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static void realise(RStatus & status, FState fs)
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{
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char * s;
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Content content;
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ATermList refs;
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if (!ATmatch(e, "File(<str>, <term>, [<list>])", &s, &content, &refs))
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throw badTerm("not f-normalised", e);
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if (ATmatch(fs, "File(<str>, <term>, [<list>])", &s, &content, &refs)) {
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string path(s);
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if (path[0] != '/') throw Error("absolute path expected: " + path);
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/* Realise referenced paths. */
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while (!ATisEmpty(refs)) {
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realise2(status, ATgetFirst(refs));
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realise(status, ATgetFirst(refs));
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refs = ATgetNext(refs);
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}
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writeContent(path, content);
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if (!ATmatch(content, "Hash(<str>)", &s))
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throw badTerm("hash expected", content);
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Hash hash = parseHash(s);
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/* Perhaps the path already exists and has the right hash? */
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if (pathExists(path)) {
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if (hash == hashPath(path)) {
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debug(format("path %1% already has hash %2%")
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% path % (string) hash);
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return;
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}
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throw Error(format("path %1% exists, but does not have hash %2%")
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% path % (string) hash);
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}
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/* Do we know a path with that hash? If so, copy it. */
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string path2 = queryFromStore(hash);
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copyFile(path2, path);
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}
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else if (ATmatch(fs, "Derive()")) {
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}
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else throw badTerm("bad file system state expression", fs);
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}
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void realise(Expr e)
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void realiseFState(FState fs)
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{
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RStatus status;
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realise2(status, e);
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realise(status, fs);
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}
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79
src/eval.hh
79
src/eval.hh
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@ -10,14 +10,12 @@ extern "C" {
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using namespace std;
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/* \section{Abstract syntax of Nix expressions}
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/* \section{Abstract syntax of Nix file system state expressions}
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An expression describes a (partial) state of the file system in a
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referentially transparent way. The operational effect of
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evaluating an expression is that the state described by the
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expression is realised.
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A Nix file system state expression, or FState, describes a
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(partial) state of the file system.
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File : Path * Content * [Expr] -> Expr
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File : Path * Content * [FState] -> FState
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File(path, content, refs) specifies a file object (its full path
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and contents), along with all file objects referenced by it (that
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@ -25,7 +23,7 @@ using namespace std;
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self-referential. This prevents us from having to deal with
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cycles.
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Derive : String * Path * [Expr] * [Expr] * [Expr] -> Expr
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Derive : String * Path * [FState] * [Path] * [(String, String)] -> [FState]
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Derive(platform, builder, ins, outs, env) specifies the creation of
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new file objects (in paths declared by `outs') by the execution of
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@ -33,14 +31,6 @@ using namespace std;
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place in a file system state given by `ins'. `env' specifies a
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mapping of strings to strings.
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Str : String -> Expr
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A string constant.
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Tup : Expr * Expr -> Expr
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Tuples of expressions.
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[ !!! NOT IMPLEMENTED
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Regular : String -> Content
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Directory : [(String, Content)] -> Content
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@ -49,7 +39,11 @@ using namespace std;
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CHash : Hash -> Content
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File content, given either in situ, or through an external reference
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to the file system or url-space decorated with a hash to preserve purity.
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to the file system or url-space decorated with a hash to preserve
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purity.
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A FState expression is in {\em $f$-normal form} if all Derive nodes
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have been reduced to File nodes.
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DISCUSSION: the idea is that a Regular/Directory is interchangeable
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with its CHash. This would appear to break referential
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@ -60,63 +54,20 @@ using namespace std;
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CHash, we should also export the file object referenced by that
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CHash.
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\section{Reduction rules}
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...
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\section{Normals forms}
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An expression is in {\em weak head normal form} if it is a lambda,
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a string or boolean value, or a File or Derive value.
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An expression is in {\em $d$-normal form} if it matches the
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signature FExpr:
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File : String * Content * [DExpr] -> DExpr
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Derive : String * Path * [Tup] * [Tup2] -> DExpr
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Tup : Str * DExpr -> Tup
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Tup : Str * Str -> Tup
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Tup : Str * Str -> Tup2
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Str : String -> Str
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These are Nix expressions in which the file system result of Derive
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expressions has not yet been computed. This is useful for, e.g.,
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querying dependencies.
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An expression is in {\em $f$-normal form} if it matches the
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signature FExpr:
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File : String * Content * [FExpr] -> FExpr
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These are completely evaluated Nix expressions.
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*/
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typedef ATerm Expr;
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typedef ATerm FState;
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typedef ATerm Content;
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/* Expression normalisation. */
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Expr whNormalise(Expr e);
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Expr dNormalise(Expr e);
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Expr fNormalise(Expr e);
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/* Realise a $f$-normalised expression in the file system. */
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void realise(Expr e);
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void realiseFState(FState fs);
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/* Return a canonical textual representation of an expression. */
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string printExpr(Expr e);
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string printTerm(ATerm t);
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/* Perform variable substitution. */
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Expr substExpr(string x, Expr rep, Expr e);
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/* Hash an expression. */
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Hash hashExpr(Expr e);
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/* Hash an aterm. */
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Hash hashTerm(ATerm t);
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#endif /* !__EVAL_H */
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@ -6,7 +6,7 @@ string dbRefs = "refs";
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string dbNFs = "nfs";
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string dbNetSources = "netsources";
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string nixValues = "/UNINIT";
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string nixStore = "/UNINIT";
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string nixLogDir = "/UNINIT";
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string nixDB = "/UNINIT";
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@ -8,15 +8,10 @@ using namespace std;
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/* Database names. */
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/* dbRefs :: Hash -> FileName
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/* dbRefs :: Hash -> Path
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Maintains a mapping from hashes to filenames within the NixValues
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directory. This mapping is for performance only; it can be
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reconstructed unambiguously. The reason is that names in this
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directory are not printed hashes but also might carry some
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descriptive element (e.g., "aterm-2.0-ae749a..."). Without this
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mapping, looking up a value would take O(n) time because we would
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need to read the entire directory. */
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Maintains a mapping from hashes to paths. This is what we use to
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resolve CHash(hash) content descriptors. */
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extern string dbRefs;
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/* dbNFs :: Hash -> Hash
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@ -45,11 +40,11 @@ extern string dbNetSources;
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/* Path names. */
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/* nixValues is the directory where all Nix values (both files and
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directories, and both normal and non-normal forms) live. */
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extern string nixValues;
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/* nixStore is the directory where we generally store atomic and
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derived files. */
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extern string nixStore;
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/* nixLogDir is the directory where we log evaluations. */
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/* nixLogDir is the directory where we log various operations. */
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extern string nixLogDir;
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/* nixDB is the file name of the Berkeley DB database where we
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@ -14,7 +14,7 @@ Hash::Hash()
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}
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||||
|
||||
|
||||
bool Hash::operator == (Hash & h2)
|
||||
bool Hash::operator == (Hash h2)
|
||||
{
|
||||
for (unsigned int i = 0; i < hashSize; i++)
|
||||
if (hash[i] != h2.hash[i]) return false;
|
||||
|
|
@ -22,7 +22,7 @@ bool Hash::operator == (Hash & h2)
|
|||
}
|
||||
|
||||
|
||||
bool Hash::operator != (Hash & h2)
|
||||
bool Hash::operator != (Hash h2)
|
||||
{
|
||||
return !(*this == h2);
|
||||
}
|
||||
|
|
|
|||
|
|
@ -17,10 +17,10 @@ struct Hash
|
|||
Hash();
|
||||
|
||||
/* Check whether two hash are equal. */
|
||||
bool operator == (Hash & h2);
|
||||
bool operator == (Hash h2);
|
||||
|
||||
/* Check whether two hash are not equal. */
|
||||
bool operator != (Hash & h2);
|
||||
bool operator != (Hash h2);
|
||||
|
||||
/* Convert a hash code into a hexadecimal representation. */
|
||||
operator string() const;
|
||||
|
|
|
|||
36
src/test.cc
36
src/test.cc
|
|
@ -11,20 +11,16 @@
|
|||
#include "globals.hh"
|
||||
|
||||
|
||||
typedef Expr (* Normaliser) (Expr);
|
||||
|
||||
|
||||
void eval(Normaliser n, Expr e)
|
||||
void realise(FState fs)
|
||||
{
|
||||
e = n(e);
|
||||
cout << (string) hashExpr(e) << ": " << printExpr(e) << endl;
|
||||
realiseFState(fs);
|
||||
}
|
||||
|
||||
|
||||
void evalFail(Normaliser n, Expr e)
|
||||
void realiseFail(FState fs)
|
||||
{
|
||||
try {
|
||||
e = n(e);
|
||||
realiseFState(fs);
|
||||
abort();
|
||||
} catch (Error e) {
|
||||
cout << "error (expected): " << e.what() << endl;
|
||||
|
|
@ -96,7 +92,7 @@ void runTests()
|
|||
string testDir = absPath("scratch");
|
||||
cout << testDir << endl;
|
||||
|
||||
nixValues = testDir;
|
||||
nixStore = testDir;
|
||||
nixLogDir = testDir;
|
||||
nixDB = testDir + "/db";
|
||||
|
||||
|
|
@ -104,6 +100,7 @@ void runTests()
|
|||
|
||||
/* Expression evaluation. */
|
||||
|
||||
#if 0
|
||||
eval(whNormalise,
|
||||
ATmake("Str(\"Hello World\")"));
|
||||
eval(whNormalise,
|
||||
|
|
@ -138,10 +135,27 @@ void runTests()
|
|||
eval(fNormalise, e2);
|
||||
|
||||
realise(e2);
|
||||
#endif
|
||||
|
||||
Hash builder1h;
|
||||
string builder1fn;
|
||||
addToStore("./test-builder-1.sh", builder1fn, builder1h);
|
||||
|
||||
FState fs1 = ATmake(
|
||||
"File(<str>, Hash(<str>), [])",
|
||||
builder1fn.c_str(),
|
||||
((string) builder1h).c_str());
|
||||
realiseFState(fs1);
|
||||
realiseFState(fs1);
|
||||
|
||||
FState fs2 = ATmake(
|
||||
"File(<str>, Hash(<str>), [])",
|
||||
(builder1fn + "_bla").c_str(),
|
||||
((string) builder1h).c_str());
|
||||
realiseFState(fs2);
|
||||
realiseFState(fs2);
|
||||
|
||||
#if 0
|
||||
Hash builder1 = addValue("./test-builder-1.sh");
|
||||
|
||||
Expr e1 = ATmake("Exec(Str(<str>), Hash(<str>), [])",
|
||||
thisSystem.c_str(), ((string) builder1).c_str());
|
||||
|
||||
|
|
|
|||
|
|
@ -78,7 +78,7 @@ void deletePath(string path)
|
|||
}
|
||||
|
||||
|
||||
void debug(string s)
|
||||
void debug(const format & f)
|
||||
{
|
||||
cerr << "debug: " << s << endl;
|
||||
cerr << format("debug: %1%\n") % f.str();
|
||||
}
|
||||
|
|
|
|||
|
|
@ -7,7 +7,10 @@
|
|||
|
||||
#include <unistd.h>
|
||||
|
||||
#include <boost/format.hpp>
|
||||
|
||||
using namespace std;
|
||||
using namespace boost;
|
||||
|
||||
|
||||
class Error : public exception
|
||||
|
|
@ -16,7 +19,7 @@ protected:
|
|||
string err;
|
||||
public:
|
||||
Error() { }
|
||||
Error(string _err) { err = _err; }
|
||||
Error(format f) { err = f.str(); }
|
||||
~Error() throw () { }
|
||||
const char * what() const throw () { return err.c_str(); }
|
||||
};
|
||||
|
|
@ -59,7 +62,7 @@ string baseNameOf(string path);
|
|||
void deletePath(string path);
|
||||
|
||||
|
||||
void debug(string s);
|
||||
void debug(const format & f);
|
||||
|
||||
|
||||
#endif /* !__UTIL_H */
|
||||
|
|
|
|||
|
|
@ -34,7 +34,7 @@ struct CopySource : RestoreSource
|
|||
};
|
||||
|
||||
|
||||
static void copyFile(string src, string dst)
|
||||
void copyFile(string src, string dst)
|
||||
{
|
||||
/* Unfortunately C++ doesn't support coprocedures, so we have no
|
||||
nice way to chain CopySink and CopySource together. Instead we
|
||||
|
|
@ -83,33 +83,25 @@ static void copyFile(string src, string dst)
|
|||
}
|
||||
|
||||
|
||||
static string absValuePath(string s)
|
||||
void addToStore(string srcPath, string & dstPath, Hash & hash)
|
||||
{
|
||||
return nixValues + "/" + s;
|
||||
}
|
||||
srcPath = absPath(srcPath);
|
||||
|
||||
hash = hashPath(srcPath);
|
||||
|
||||
Hash addValue(string path)
|
||||
{
|
||||
path = absPath(path);
|
||||
|
||||
Hash hash = hashPath(path);
|
||||
|
||||
string name;
|
||||
if (queryDB(nixDB, dbRefs, hash, name)) {
|
||||
string path;
|
||||
if (queryDB(nixDB, dbRefs, hash, path)) {
|
||||
debug((string) hash + " already known");
|
||||
return hash;
|
||||
dstPath = path;
|
||||
return;
|
||||
}
|
||||
|
||||
string baseName = baseNameOf(path);
|
||||
string baseName = baseNameOf(srcPath);
|
||||
dstPath = nixStore + "/" + (string) hash + "-" + baseName;
|
||||
|
||||
string targetName = (string) hash + "-" + baseName;
|
||||
copyFile(srcPath, dstPath);
|
||||
|
||||
copyFile(path, absValuePath(targetName));
|
||||
|
||||
setDB(nixDB, dbRefs, hash, targetName);
|
||||
|
||||
return hash;
|
||||
setDB(nixDB, dbRefs, hash, dstPath);
|
||||
}
|
||||
|
||||
|
||||
|
|
@ -135,28 +127,28 @@ string fetchURL(string url)
|
|||
#endif
|
||||
|
||||
|
||||
void deleteValue(Hash hash)
|
||||
void deleteFromStore(Hash hash)
|
||||
{
|
||||
string name;
|
||||
if (queryDB(nixDB, dbRefs, hash, name)) {
|
||||
string fn = absValuePath(name);
|
||||
string fn;
|
||||
if (queryDB(nixDB, dbRefs, hash, fn)) {
|
||||
string prefix = nixStore + "/";
|
||||
if (string(fn, prefix.size()) != prefix)
|
||||
throw Error("path " + fn + " is not in the store");
|
||||
deletePath(fn);
|
||||
delDB(nixDB, dbRefs, hash);
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
/* !!! bad name, "query" implies no side effect => getValuePath() */
|
||||
string queryValuePath(Hash hash)
|
||||
string queryFromStore(Hash hash)
|
||||
{
|
||||
bool checkedNet = false;
|
||||
|
||||
while (1) {
|
||||
|
||||
string name, url;
|
||||
string fn, url;
|
||||
|
||||
if (queryDB(nixDB, dbRefs, hash, name)) {
|
||||
string fn = absValuePath(name);
|
||||
if (queryDB(nixDB, dbRefs, hash, fn)) {
|
||||
|
||||
/* Verify that the file hasn't changed. !!! race !!! slow */
|
||||
if (hashPath(fn) != hash)
|
||||
|
|
|
|||
|
|
@ -8,21 +8,17 @@
|
|||
using namespace std;
|
||||
|
||||
|
||||
/* Copy a value to the nixValues directory and register it in dbRefs.
|
||||
void copyFile(string src, string dst);
|
||||
|
||||
/* Copy a file to the nixStore directory and register it in dbRefs.
|
||||
Return the hash code of the value. */
|
||||
Hash addValue(string pathName);
|
||||
void addToStore(string srcPath, string & dstPath, Hash & hash);
|
||||
|
||||
/* Delete a value from the nixStore directory. */
|
||||
void deleteFromStore(Hash hash);
|
||||
|
||||
/* Delete a value from the nixValues directory. */
|
||||
void deleteValue(Hash hash);
|
||||
|
||||
|
||||
/* Obtain the path of a value with the given hash. If a file with
|
||||
that hash is known to exist in the local file system (as indicated
|
||||
by the dbRefs database), we use that. Otherwise, we attempt to
|
||||
fetch it from the network (using dbNetSources). We verify that the
|
||||
file has the right hash. */
|
||||
string queryValuePath(Hash hash);
|
||||
/* !!! */
|
||||
string queryFromStore(Hash hash);
|
||||
|
||||
|
||||
#endif /* !__VALUES_H */
|
||||
|
|
|
|||
Loading…
Reference in a new issue