52 lines
2 KiB
C
52 lines
2 KiB
C
|
/* Context-free grammar representation and analysis */
|
||
|
|
|
||
|
|
#include "internal.h"
|
||
|
|
|
||
|
|
|
||
|
|
typedef struct HCFGrammar_ {
|
||
|
|
HCFChoice *start; // start symbol (nonterminal)
|
||
|
|
HHashSet *nts; // HCFChoices, each representing the alternative
|
||
|
|
// productions for one nonterminal
|
||
|
|
HHashSet *geneps; // set of NTs that can generate the empty string
|
||
|
|
HHashTable *first; // memoized first sets of the grammar's symbols
|
||
|
|
HHashTable *follow; // memoized follow sets of the grammar's NTs
|
||
|
|
HArena *arena;
|
||
|
|
} HCFGrammar;
|
||
|
|
|
||
|
|
/* mapping input bytes or end to tokens
|
||
|
|
* we want to use these, cast to void *, as elements in hashsets
|
||
|
|
* therefore we must avoid 0 as a token value because NULL means "not in set".
|
||
|
|
*/
|
||
|
|
typedef uintptr_t HCFToken;
|
||
|
|
static inline HCFToken char_token(char c) { return (0x100 | c); }
|
||
|
|
static inline char token_char(HCFToken t) { return (0xFF & t); }
|
||
|
|
static const HCFToken end_token = 0x200;
|
||
|
|
|
||
|
|
|
||
|
|
/* Convert 'parser' into CFG representation by desugaring and compiling the set
|
||
|
|
* of nonterminals.
|
||
|
|
* A NULL return means we are unable to represent the parser as a CFG.
|
||
|
|
*/
|
||
|
|
HCFGrammar *h_cfgrammar(HAllocator* mm__, const HParser *parser);
|
||
|
|
|
||
|
|
/* Does the given symbol derive the empty string (under g)? */
|
||
|
|
bool h_symbol_derives_epsilon(HCFGrammar *g, const HCFChoice *symbol);
|
||
|
|
|
||
|
|
/* Does the sentential form s derive the empty string? s NULL-terminated. */
|
||
|
|
bool h_sequence_derives_epsilon(HCFGrammar *g, HCFChoice **s);
|
||
|
|
|
||
|
|
/* Compute first set of sentential form s. s NULL-terminated. */
|
||
|
|
HHashSet *h_first_sequence(HCFGrammar *g, HCFChoice **s);
|
||
|
|
|
||
|
|
/* Compute first set of symbol x. Memoized. */
|
||
|
|
HHashSet *h_first_symbol(HCFGrammar *g, const HCFChoice *x);
|
||
|
|
|
||
|
|
/* Compute follow set of symbol x. Memoized. */
|
||
|
|
HHashSet *h_follow(HCFGrammar *g, const HCFChoice *x);
|
||
|
|
|
||
|
|
|
||
|
|
/* Pretty-printers for grammars and associated data. */
|
||
|
|
void h_pprint_grammar(FILE *file, const HCFGrammar *g, int indent);
|
||
|
|
void h_pprint_symbolset(FILE *file, const HCFGrammar *g, const HHashSet *set, int indent);
|
||
|
|
void h_pprint_tokenset(FILE *file, const HCFGrammar *g, const HHashSet *set, int indent);
|