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Store contexts as symbols

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This provides some deduplication since most contexts are used multiple
times.

Also, store singleton contexts directly in the Value object. This
saves a 16-byte Context object. This is useful because the vast
majority of contexts are singletons, e.g. 23723 out of 26138 in a
NixOS 19.03 system configuration.
This commit is contained in:
Eelco Dolstra 2019-04-23 11:07:47 +02:00
parent e392ff53e9
commit 2160258cc4
8 changed files with 78 additions and 37 deletions
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33
src/libexpr/eval.cc
View file

@ -21,6 +21,8 @@
namespace nix {
SymbolTable symbols;
// FIXME
static char * dupString(const char * s)
@ -500,15 +502,7 @@ void mkString(Value & v, const char * s)
Value & mkString(Value & v, const string & s, const PathSet & context)
{
mkString(v, s.c_str());
if (!context.empty()) {
size_t n = 0;
// FIXME: store as Symbols?
v.string.context = (const char * *)
malloc((context.size() + 1) * sizeof(char *));
for (auto & i : context)
v.string.context[n++] = dupString(i.c_str());
v.string.context[n] = 0;
}
v.setContext(context);
return v;
}
@ -1464,18 +1458,10 @@ string EvalState::forceString(Value & v, const Pos & pos)
}
void copyContext(const Value & v, PathSet & context)
{
if (v.string.context)
for (const char * * p = v.string.context; *p; ++p)
context.insert(*p);
}
string EvalState::forceString(Value & v, PathSet & context, const Pos & pos)
{
string s = forceString(v, pos);
copyContext(v, context);
v.getContext(context);
return s;
}
@ -1484,12 +1470,14 @@ string EvalState::forceStringNoCtx(Value & v, const Pos & pos)
{
string s = forceString(v, pos);
if (v.string.context) {
PathSet context;
v.getContext(context);
if (pos)
throwEvalError("the string '%1%' is not allowed to refer to a store path (such as '%2%'), at %3%",
v.string.s, v.string.context[0], pos);
v.string.s, *context.begin(), pos);
else
throwEvalError("the string '%1%' is not allowed to refer to a store path (such as '%2%')",
v.string.s, v.string.context[0]);
v.string.s, *context.begin());
}
return s;
}
@ -1514,7 +1502,7 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
string s;
if (v.type == tString) {
copyContext(v, context);
v.getContext(context);
return v.string.s;
}
@ -1813,9 +1801,6 @@ size_t valueSize(Value & v)
switch (v.type) {
case tString:
sz += doString(v.string.s);
if (v.string.context)
for (const char * * p = v.string.context; *p; ++p)
sz += doString(*p);
break;
case tPath:
sz += doString(v.path);