104 lines
4.4 KiB
C
104 lines
4.4 KiB
C
/* Context-free grammar representation and analysis */
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#include "internal.h"
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typedef struct HCFGrammar_ {
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HCFChoice *start; // start symbol (nonterminal)
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HHashSet *nts; // HCFChoices, each representing the alternative
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// productions for one nonterminal
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HHashSet *geneps; // set of NTs that can generate the empty string
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HHashTable **first; // memoized first sets of the grammar's symbols
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HHashTable **follow; // memoized follow sets of the grammar's NTs
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size_t kmax; // maximum lookahead depth allocated
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HArena *arena;
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HAllocator *mm__;
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// constant set containing only the empty string.
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// this is only a member of HCFGrammar because it needs a pointer to arena.
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const struct HStringMap_ *singleton_epsilon;
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} HCFGrammar;
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/* Representing input characters (bytes) in HHashTables.
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* To use these as keys, we must avoid 0 as because NULL means "not set".
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*/
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typedef uintptr_t HCharKey;
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static inline HCharKey char_key(uint8_t c) { return (0x100 | c); }
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static inline uint8_t key_char(HCharKey k) { return (0xFF & k); }
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/* Mapping strings of input tokens to arbitrary values (or serving as a set).
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* Common prefixes are folded into a tree of HHashTables, branches labeled with
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* input tokens.
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* Each path through the tree represents the string along its branches.
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*/
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typedef struct HStringMap_ {
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void *epsilon_branch; // points to leaf value
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void *end_branch; // points to leaf value
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HHashTable *char_branches; // maps to inner nodes (HStringMaps)
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HArena *arena;
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} HStringMap;
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HStringMap *h_stringmap_new(HArena *a);
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void h_stringmap_put_end(HStringMap *m, void *v);
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void h_stringmap_put_epsilon(HStringMap *m, void *v);
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void h_stringmap_put_after(HStringMap *m, uint8_t c, HStringMap *ends);
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void h_stringmap_put_char(HStringMap *m, uint8_t c, void *v);
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void h_stringmap_update(HStringMap *m, const HStringMap *n);
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void h_stringmap_replace(HStringMap *m, void *old, void *new);
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void *h_stringmap_get(const HStringMap *m, const uint8_t *str, size_t n, bool end);
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void *h_stringmap_get_lookahead(const HStringMap *m, HInputStream lookahead);
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bool h_stringmap_present(const HStringMap *m, const uint8_t *str, size_t n, bool end);
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bool h_stringmap_present_epsilon(const HStringMap *m);
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bool h_stringmap_empty(const HStringMap *m);
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static inline HStringMap *h_stringmap_get_char(const HStringMap *m, const uint8_t c)
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{ return h_hashtable_get(m->char_branches, (void *)char_key(c)); }
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/* Convert 'parser' into CFG representation by desugaring and compiling the set
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* of nonterminals.
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* A NULL return means we are unable to represent the parser as a CFG.
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*/
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HCFGrammar *h_cfgrammar(HAllocator* mm__, const HParser *parser);
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HCFGrammar *h_cfgrammar_(HAllocator* mm__, HCFChoice *start);
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HCFGrammar *h_cfgrammar_new(HAllocator *mm__);
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/* Frees the given grammar and associated data.
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* Does *not* free parsers' CFG forms as created by h_desugar.
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*/
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void h_cfgrammar_free(HCFGrammar *g);
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/* Does the given symbol derive the empty string (under g)? */
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bool h_derives_epsilon(HCFGrammar *g, const HCFChoice *symbol);
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/* Does the sentential form s derive the empty string? s NULL-terminated. */
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bool h_derives_epsilon_seq(HCFGrammar *g, HCFChoice **s);
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/* Compute first_k set of symbol x. Memoized. */
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const HStringMap *h_first(size_t k, HCFGrammar *g, const HCFChoice *x);
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/* Compute first_k set of sentential form s. s NULL-terminated. */
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const HStringMap *h_first_seq(size_t k, HCFGrammar *g, HCFChoice **s);
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/* Compute follow_k set of symbol x. Memoized. */
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const HStringMap *h_follow(size_t k, HCFGrammar *g, const HCFChoice *x);
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/* Compute the predict_k set of production "A -> rhs".
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* Always returns a newly-allocated HStringMap.
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*/
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HStringMap *h_predict(size_t k, HCFGrammar *g,
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const HCFChoice *A, const HCFSequence *rhs);
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/* Pretty-printers for grammars and associated data. */
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void h_pprint_grammar(FILE *file, const HCFGrammar *g, int indent);
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void h_pprint_sequence(FILE *f, const HCFGrammar *g, const HCFSequence *seq);
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void h_pprint_symbol(FILE *f, const HCFGrammar *g, const HCFChoice *x);
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void h_pprint_symbolset(FILE *file, const HCFGrammar *g, const HHashSet *set, int indent);
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void h_pprint_stringset(FILE *file, const HStringMap *set, int indent);
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void h_pprint_stringmap(FILE *file, char sep,
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void (*valprint)(FILE *f, void *env, void *val), void *env,
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const HStringMap *map);
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void h_pprint_char(FILE *file, char c);
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