diff options
Diffstat (limited to 'third_party')
| -rw-r--r-- | third_party/nix/src/libexpr/symbol-table.hh | 26 |
1 files changed, 19 insertions, 7 deletions
diff --git a/third_party/nix/src/libexpr/symbol-table.hh b/third_party/nix/src/libexpr/symbol-table.hh index 62c0b48a173b..5005bb416bb7 100644 --- a/third_party/nix/src/libexpr/symbol-table.hh +++ b/third_party/nix/src/libexpr/symbol-table.hh @@ -7,12 +7,7 @@ namespace nix { // TODO(tazjin): ::expr -/* Symbol table used by the parser and evaluator to represent and look - up identifiers and attributes efficiently. SymbolTable::create() - converts a string into a symbol. Symbols have the property that - they can be compared efficiently (using a pointer equality test), - because the symbol table stores only one copy of each string. */ - + // TODO(tazjin): Replace with a simpler struct, or get rid of. class Symbol { private: const std::string* s; // pointer into SymbolTable @@ -37,11 +32,28 @@ class Symbol { friend std::ostream& operator<<(std::ostream& str, const Symbol& sym); }; +// SymbolTable is a hash-set based symbol-interning mechanism. +// +// TODO(tazjin): Figure out which things use this. AttrSets, ...? +// Is it possible this only exists because AttrSet wasn't a map? +// +// Original comment: +// +// Symbol table used by the parser and evaluator to represent and look +// up identifiers and attributes efficiently. SymbolTable::create() +// converts a string into a symbol. Symbols have the property that +// they can be compared efficiently (using a pointer equality test), +// because the symbol table stores only one copy of each string. class SymbolTable { public: + // Create a new symbol in this table by emplacing the provided + // string into it. + // + // The symbol will reference an existing symbol if the symbol is + // already interned. Symbol Create(absl::string_view sym); - // TODO(tazjin): two of these? + // Return the number of symbols interned. size_t Size() const; // Return the total size (in bytes) |