forked from lix-project/lix
0b305c534f
tree). This saves a lot of memory. The vector should be sorted so
that names can be looked up using binary search, but this is not the
case yet. (Surprisingly, looking up attributes using linear search
doesn't have a big impact on performance.)
Memory consumption for
$ nix-instantiate /etc/nixos/nixos/tests -A bittorrent.test --readonly-mode
on x86_64-linux with GC enabled is now 185 MiB (compared to 946
MiB on the trunk).
73 lines
2.1 KiB
C++
73 lines
2.1 KiB
C++
#include "attr-path.hh"
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#include "util.hh"
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namespace nix {
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// !!! Shouldn't we return a pointer to a Value?
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void findAlongAttrPath(EvalState & state, const string & attrPath,
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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->value;
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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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