forked from lix-project/lix
add an ExprPrinter class, like ValuePrinter
To be used Shortly
Change-Id: I9def7975aa55f251eb8486391677771f7352d7ce
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59bf6825ef
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@ -574,4 +574,10 @@ fmt_internal::HintFmt & fmt_internal::HintFmt::operator%(const ValuePrinter & va
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return *this;
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}
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std::ostream & operator<<(std::ostream & output, ExprPrinter const & printer)
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{
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printer.expr.show(printer.state.symbols, output);
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return output;
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}
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}
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@ -15,6 +15,8 @@
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namespace nix {
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struct Expr;
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class EvalState;
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struct Value;
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@ -50,6 +52,12 @@ void printValue(EvalState & state, std::ostream & str, Value & v, PrintOptions o
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/**
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* A partially-applied form of `printValue` which can be formatted using `<<`
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* without allocating an intermediate string.
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* This class should not outlive the eval state or it will UAF.
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* FIXME: This should take `nix::ref`s, to avoid that, but our eval methods all have
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* EvalState &, not ref<EvalState>, and constructing a new shared_ptr to data that
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* already has a shared_ptr is a much bigger footgun. In the current architecture of
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* libexpr, using a ValuePrinter after an EvalState has been destroyed would be
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* pretty hard.
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*/
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class ValuePrinter {
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friend std::ostream & operator << (std::ostream & output, const ValuePrinter & printer);
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@ -73,4 +81,26 @@ std::ostream & operator<<(std::ostream & output, const ValuePrinter & printer);
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template<>
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fmt_internal::HintFmt & fmt_internal::HintFmt::operator%(const ValuePrinter & value);
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/**
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* A partially-applied form of Expr::show(), which can be formatted using `<<`
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* without allocating an intermediate string.
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* This class should not outlive the eval state or it will UAF.
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* FIXME: This should take `nix::ref`s, to avoid that, but our eval methods all have
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* EvalState &, not ref<EvalState>, and constructing a new shared_ptr to data that
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* already has a shared_ptr is a much bigger footgun. In the current architecture of
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* libexpr, using an ExprPrinter after an EvalState has been destroyed would be
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* pretty hard.
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*/
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class ExprPrinter
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{
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/** The eval state used to get symbols. */
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EvalState const & state;
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/** The expression to print. */
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Expr const & expr;
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public:
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ExprPrinter(EvalState const & state, Expr const & expr) : state(state), expr(expr) { }
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friend std::ostream & operator << (std::ostream & output, ExprPrinter const & printer);
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};
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}
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