forked from lix-project/lix
04c4bd3624
values. This improves sharing and gives another speed up. Evaluation of the NixOS system attribute is now almost 7 times faster than the old evaluator.
72 lines
2 KiB
C++
72 lines
2 KiB
C++
#include "attr-path.hh"
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#include "util.hh"
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namespace nix {
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void findAlongAttrPath(EvalState & state, const string & attrPath,
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const Bindings & autoArgs, Expr * e, Value & v)
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{
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Strings tokens = tokenizeString(attrPath, ".");
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Error attrError =
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Error(format("attribute selection path `%1%' does not match expression") % attrPath);
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string curPath;
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state.mkThunk_(v, e);
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foreach (Strings::iterator, i, tokens) {
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if (!curPath.empty()) curPath += ".";
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curPath += *i;
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/* Is *i an index (integer) or a normal attribute name? */
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enum { apAttr, apIndex } apType = apAttr;
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string attr = *i;
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int attrIndex = -1;
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if (string2Int(attr, attrIndex)) apType = apIndex;
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/* Evaluate the expression. */
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Value vTmp;
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state.autoCallFunction(autoArgs, v, vTmp);
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v = vTmp;
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state.forceValue(v);
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/* It should evaluate to either an attribute set or an
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expression, according to what is specified in the
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attrPath. */
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if (apType == apAttr) {
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if (v.type != tAttrs)
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throw TypeError(
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format("the expression selected by the selection path `%1%' should be an attribute set but is %2%")
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% curPath % showType(v));
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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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throw Error(format("attribute `%1%' in selection path `%2%' not found") % attr % curPath);
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v = a->second;
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}
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else if (apType == apIndex) {
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if (v.type != tList)
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throw TypeError(
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format("the expression selected by the selection path `%1%' should be a list but is %2%")
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% curPath % showType(v));
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if (attrIndex >= v.list.length)
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throw Error(format("list index %1% in selection path `%2%' is out of range") % attrIndex % curPath);
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v = *v.list.elems[attrIndex];
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}
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}
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}
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}
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