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!)
71 lines
1.6 KiB
C++
71 lines
1.6 KiB
C++
#include "attr-set.hh"
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#include "eval-inline.hh"
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#include <algorithm>
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namespace nix {
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/* Allocate a new array of attributes for an attribute set with a specific
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capacity. The space is implicitly reserved after the Bindings
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structure. */
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Bindings * EvalState::allocBindings(size_t capacity)
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{
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if (capacity == 0)
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return &emptyBindings;
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if (capacity > std::numeric_limits<Bindings::size_t>::max())
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throw Error("attribute set of size %d is too big", capacity);
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nrAttrsets++;
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nrAttrsInAttrsets += capacity;
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return new (allocBytes(sizeof(Bindings) + sizeof(Attr) * capacity)) Bindings((Bindings::size_t) capacity);
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}
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/* Create a new attribute named 'name' on an existing attribute set stored
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in 'vAttrs' and return the newly allocated Value which is associated with
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this attribute. */
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Value * EvalState::allocAttr(Value & vAttrs, const SymbolIdx & name)
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{
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Value * v = allocValue();
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vAttrs.attrs->push_back(Attr(name, v));
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return v;
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}
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Value * EvalState::allocAttr(Value & vAttrs, std::string_view name)
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{
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return allocAttr(vAttrs, symbols.create(name));
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}
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Value & BindingsBuilder::alloc(const SymbolIdx & name, PosIdx pos)
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{
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auto value = state.allocValue();
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bindings->push_back(Attr(name, value, pos));
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return *value;
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}
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Value & BindingsBuilder::alloc(std::string_view name, PosIdx pos)
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{
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return alloc(state.symbols.create(name), pos);
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}
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void Bindings::sort()
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{
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if (size_) std::sort(begin(), end());
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}
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Value & Value::mkAttrs(BindingsBuilder & bindings)
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{
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mkAttrs(bindings.finish());
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return *this;
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}
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}
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