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* Don't use an ostringstream in unparseDerivation(), because it's

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slow.  A `nix-env -qa --drv-path \*' on Nixpkgs was spending 40% of
  its time in unparseDerivation() because of this (now 11%).
This commit is contained in:
Eelco Dolstra 2010-04-21 19:25:50 +00:00
parent 7148df7971
commit 6bbfe95e30
1 changed files with 39 additions and 38 deletions
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77
src/libstore/derivations.cc
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@ -92,75 +92,76 @@ Derivation parseDerivation(const string & s)
} }
void printString(std::ostream & str, const string & s) static void printString(string & res, const string & s)
{ {
str << "\""; res += '"';
for (const char * i = s.c_str(); *i; i++) for (const char * i = s.c_str(); *i; i++)
if (*i == '\"' || *i == '\\') str << "\\" << *i; if (*i == '\"' || *i == '\\') { res += "\\"; res += *i; }
else if (*i == '\n') str << "\\n"; else if (*i == '\n') res += "\\n";
else if (*i == '\r') str << "\\r"; else if (*i == '\r') res += "\\r";
else if (*i == '\t') str << "\\t"; else if (*i == '\t') res += "\\t";
else str << *i; else res += *i;
str << "\""; res += '"';
} }
template<class ForwardIterator> template<class ForwardIterator>
void printStrings(std::ostream & str, ForwardIterator i, ForwardIterator j) static void printStrings(string & res, ForwardIterator i, ForwardIterator j)
{ {
str << "["; res += '[';
bool first = true; bool first = true;
for ( ; i != j; ++i) { for ( ; i != j; ++i) {
if (first) first = false; else str << ","; if (first) first = false; else res += ',';
printString(str, *i); printString(res, *i);
} }
str << "]"; res += ']';
} }
string unparseDerivation(const Derivation & drv) string unparseDerivation(const Derivation & drv)
{ {
std::ostringstream str; string s;
str << "Derive(["; s.reserve(65536);
s += "Derive([";
bool first = true; bool first = true;
foreach (DerivationOutputs::const_iterator, i, drv.outputs) { foreach (DerivationOutputs::const_iterator, i, drv.outputs) {
if (first) first = false; else str << ","; if (first) first = false; else s += ',';
str << "("; printString(str, i->first); s += '('; printString(s, i->first);
str << ","; printString(str, i->second.path); s += ','; printString(s, i->second.path);
str << ","; printString(str, i->second.hashAlgo); s += ','; printString(s, i->second.hashAlgo);
str << ","; printString(str, i->second.hash); s += ','; printString(s, i->second.hash);
str << ")"; s += ')';
} }
str << "],["; s += "],[";
first = true; first = true;
foreach (DerivationInputs::const_iterator, i, drv.inputDrvs) { foreach (DerivationInputs::const_iterator, i, drv.inputDrvs) {
if (first) first = false; else str << ","; if (first) first = false; else s += ',';
str << "("; printString(str, i->first); s += '('; printString(s, i->first);
str << ","; printStrings(str, i->second.begin(), i->second.end()); s += ','; printStrings(s, i->second.begin(), i->second.end());
str << ")"; s += ')';
} }
str << "],"; s += "],";
printStrings(str, drv.inputSrcs.begin(), drv.inputSrcs.end()); printStrings(s, drv.inputSrcs.begin(), drv.inputSrcs.end());
str << ","; printString(str, drv.platform); s += ','; printString(s, drv.platform);
str << ","; printString(str, drv.builder); s += ','; printString(s, drv.builder);
str << ","; printStrings(str, drv.args.begin(), drv.args.end()); s += ','; printStrings(s, drv.args.begin(), drv.args.end());
str << ",["; s += ",[";
first = true; first = true;
foreach (StringPairs::const_iterator, i, drv.env) { foreach (StringPairs::const_iterator, i, drv.env) {
if (first) first = false; else str << ","; if (first) first = false; else s += ',';
str << "("; printString(str, i->first); s += '('; printString(s, i->first);
str << ","; printString(str, i->second); s += ','; printString(s, i->second);
str << ")"; s += ')';
} }
str << "])"; s += "])";
return str.str(); return s;
} }