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* Optimise string constants by putting them in the symbol table.

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This commit is contained in:
Eelco Dolstra 2010-10-23 21:11:59 +00:00
parent 8ac06726b9
commit b2ba62170c
4 changed files with 55 additions and 39 deletions
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72
src/libexpr/parser.y
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@ -7,19 +7,44 @@
%parse-param { yyscan_t scanner }
%parse-param { ParseData * data }
%lex-param { yyscan_t scanner }
%lex-param { ParseData * data }
%{
/* Newer versions of Bison copy the declarations below to
parser-tab.hh, which sucks bigtime since lexer.l doesn't want that
stuff. So allow it to be excluded. */
#ifndef BISON_HEADER_HACK
#define BISON_HEADER_HACK
%code requires {
#ifndef BISON_HEADER
#define BISON_HEADER
#include "util.hh"
#include "nixexpr.hh"
namespace nix {
struct ParseData
{
SymbolTable & symbols;
Expr * result;
Path basePath;
Path path;
string error;
Symbol sLetBody;
ParseData(SymbolTable & symbols)
: symbols(symbols)
, sLetBody(symbols.create("<let-body>"))
{ };
};
}
#define YY_DECL int yylex \
(YYSTYPE * yylval_param, YYLTYPE * yylloc_param, yyscan_t yyscanner, nix::ParseData * data)
#endif
}
%{
#include "parser-tab.hh"
#include "lexer-tab.hh"
#define YYSTYPE YYSTYPE // workaround a bug in Bison 2.4
@ -28,27 +53,13 @@
#include <stdlib.h>
#include <string.h>
YY_DECL;
using namespace nix;
namespace nix {
struct ParseData
{
SymbolTable & symbols;
Expr * result;
Path basePath;
Path path;
string error;
Symbol sLetBody;
ParseData(SymbolTable & symbols)
: symbols(symbols)
, sLetBody(symbols.create("<let-body>"))
{ };
};
static string showAttrPath(const vector<Symbol> & attrPath)
{
@ -113,9 +124,9 @@ static void addFormal(const Pos & pos, Formals * formals, const Formal & formal)
}
static Expr * stripIndentation(vector<Expr *> & es)
static Expr * stripIndentation(SymbolTable & symbols, vector<Expr *> & es)
{
if (es.empty()) return new ExprString("");
if (es.empty()) return new ExprString(symbols.create(""));
/* Figure out the minimum indentation. Note that by design
whitespace-only final lines are not taken into account. (So
@ -195,7 +206,7 @@ static Expr * stripIndentation(vector<Expr *> & es)
s2 = string(s2, 0, p + 1);
}
es2->push_back(new ExprString(s2));
es2->push_back(new ExprString(symbols.create(s2)));
}
return new ExprConcatStrings(es2);
@ -224,9 +235,6 @@ void yyerror(YYLTYPE * loc, yyscan_t scanner, ParseData * data, const char * err
}
#endif
%}
%union {
@ -337,15 +345,15 @@ expr_simple
| INT { $$ = new ExprInt($1); }
| '"' string_parts '"' {
/* For efficiency, and to simplify parse trees a bit. */
if ($2->empty()) $$ = new ExprString("");
if ($2->empty()) $$ = new ExprString(data->symbols.create(""));
else if ($2->size() == 1) $$ = $2->front();
else $$ = new ExprConcatStrings($2);
}
| IND_STRING_OPEN ind_string_parts IND_STRING_CLOSE {
$$ = stripIndentation(*$2);
$$ = stripIndentation(data->symbols, *$2);
}
| PATH { $$ = new ExprPath(absPath($1, data->basePath)); }
| URI { $$ = new ExprString($1); }
| URI { $$ = new ExprString(data->symbols.create($1)); }
| '(' expr ')' { $$ = $2; }
/* Let expressions `let {..., body = ...}' are just desugared
into `(rec {..., body = ...}).body'. */