move grammar analysis stuff to its own files

src/cfgrammar.h

@@ -0,0 +1,51 @@
+/* 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);