forked from lix-project/lix
8775be3393
this slightly increases the amount of memory used for any given symbol, but this increase is more than made up for if the symbol is referenced more than once in the EvalState that holds it. on average every symbol should be referenced at least twice (once to introduce a binding, once to use it), so we expect no increase in memory on average. symbol tables are limited to 2³² entries like position tables, and similar arguments apply to why overflow is not likely: 2³² symbols would require as many string instances (at 24 bytes each) and map entries (at 24 bytes or more each, assuming that the map holds on average at most one item per bucket as the docs say). a full symbol table would require at least 192GB of memory just for symbols, which is well out of reach. (an ofborg eval of nixpks today creates less than a million symbols!)
139 lines
4 KiB
C++
139 lines
4 KiB
C++
#include "attr-path.hh"
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#include "eval-inline.hh"
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#include "util.hh"
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namespace nix {
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static Strings parseAttrPath(std::string_view s)
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{
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Strings res;
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std::string cur;
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auto i = s.begin();
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while (i != s.end()) {
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if (*i == '.') {
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res.push_back(cur);
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cur.clear();
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} else if (*i == '"') {
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++i;
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while (1) {
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if (i == s.end())
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throw ParseError("missing closing quote in selection path '%1%'", s);
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if (*i == '"') break;
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cur.push_back(*i++);
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}
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} else
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cur.push_back(*i);
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++i;
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}
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if (!cur.empty()) res.push_back(cur);
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return res;
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}
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std::vector<Symbol> parseAttrPath(EvalState & state, std::string_view s)
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{
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std::vector<Symbol> res;
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for (auto & a : parseAttrPath(s))
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res.emplace_back(a);
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return res;
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}
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std::pair<Value *, PosIdx> findAlongAttrPath(EvalState & state, const std::string & attrPath,
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Bindings & autoArgs, Value & vIn)
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{
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Strings tokens = parseAttrPath(attrPath);
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Value * v = &vIn;
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PosIdx pos = noPos;
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for (auto & attr : tokens) {
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/* Is i an index (integer) or a normal attribute name? */
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auto attrIndex = string2Int<unsigned int>(attr);
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/* Evaluate the expression. */
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Value * vNew = state.allocValue();
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state.autoCallFunction(autoArgs, *v, *vNew);
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v = vNew;
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state.forceValue(*v, noPos);
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/* It should evaluate to either a set or an expression,
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according to what is specified in the attrPath. */
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if (!attrIndex) {
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if (v->type() != nAttrs)
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throw TypeError(
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"the expression selected by the selection path '%1%' should be a set but is %2%",
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attrPath,
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showType(*v));
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if (attr.empty())
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throw Error("empty attribute name in selection path '%1%'", attrPath);
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Bindings::iterator a = v->attrs->find(state.symbols.create(attr));
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if (a == v->attrs->end()) {
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std::set<std::string> attrNames;
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for (auto & attr : *v->attrs)
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attrNames.insert(state.symbols[attr.name]);
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auto suggestions = Suggestions::bestMatches(attrNames, attr);
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throw AttrPathNotFound(suggestions, "attribute '%1%' in selection path '%2%' not found", attr, attrPath);
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}
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v = &*a->value;
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pos = a->pos;
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}
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else {
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if (!v->isList())
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throw TypeError(
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"the expression selected by the selection path '%1%' should be a list but is %2%",
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attrPath,
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showType(*v));
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if (*attrIndex >= v->listSize())
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throw AttrPathNotFound("list index %1% in selection path '%2%' is out of range", *attrIndex, attrPath);
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v = v->listElems()[*attrIndex];
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pos = noPos;
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}
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}
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return {v, pos};
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}
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std::pair<std::string, uint32_t> findPackageFilename(EvalState & state, Value & v, std::string what)
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{
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Value * v2;
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try {
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auto dummyArgs = state.allocBindings(0);
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v2 = findAlongAttrPath(state, "meta.position", *dummyArgs, v).first;
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} catch (Error &) {
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throw NoPositionInfo("package '%s' has no source location information", what);
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}
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// FIXME: is it possible to extract the Pos object instead of doing this
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// toString + parsing?
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auto pos = state.forceString(*v2);
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auto colon = pos.rfind(':');
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if (colon == std::string::npos)
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throw ParseError("cannot parse meta.position attribute '%s'", pos);
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std::string filename(pos, 0, colon);
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unsigned int lineno;
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try {
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lineno = std::stoi(std::string(pos, colon + 1, std::string::npos));
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} catch (std::invalid_argument & e) {
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throw ParseError("cannot parse line number '%s'", pos);
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}
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return { std::move(filename), lineno };
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}
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}
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