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split LR code into lr.c, lr0.c, and lalr.c

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This commit is contained in:
Sven M. Hallberg 2013-06-17 20:08:25 +02:00
parent 7eff4b8d94
commit 129d50c0ef
5 changed files with 806 additions and 750 deletions
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2
src/Makefile
View file

@ -43,6 +43,8 @@ HAMMER_PARTS := \
benchmark.o \ benchmark.o \
cfgrammar.o \ cfgrammar.o \
glue.o \ glue.o \
backends/lr.o \
backends/lr0.o \
$(PARSERS:%=parsers/%.o) \ $(PARSERS:%=parsers/%.o) \
$(BACKENDS:%=backends/%.o) $(BACKENDS:%=backends/%.o)

758
src/backends/lalr.c
View file

@ -1,437 +1,6 @@
#include <assert.h> #include <assert.h>
#include "../internal.h"
#include "../cfgrammar.h"
#include "../parsers/parser_internal.h"
#include "contextfree.h" #include "contextfree.h"
#include "lr.h"
/* Data structures */
typedef HHashSet HLRState; // states are sets of LRItems
typedef struct HLRDFA_ {
size_t nstates;
const HLRState **states; // array of size nstates
HSlist *transitions;
} HLRDFA;
typedef struct HLRTransition_ {
size_t from; // index into 'states' array
const HCFChoice *symbol;
size_t to; // index into 'states' array
} HLRTransition;
typedef struct HLRItem_ {
HCFChoice *lhs;
HCFChoice **rhs; // NULL-terminated
size_t len; // number of elements in rhs
size_t mark;
} HLRItem;
typedef struct HLRAction_ {
enum {HLR_SHIFT, HLR_REDUCE} type;
union {
size_t nextstate; // used with SHIFT
struct {
HCFChoice *lhs; // symbol carrying semantic actions etc.
size_t length; // # of symbols in rhs
#ifndef NDEBUG
HCFChoice **rhs; // NB: the rhs symbols are not needed for the parse
#endif
} production; // used with REDUCE
};
} HLRAction;
typedef struct HLRTable_ {
size_t nrows;
HHashTable **rows; // map symbols to HLRActions
HLRAction **forall; // shortcut to set an action for an entire row
HCFChoice *start; // start symbol
HSlist *inadeq; // indices of any inadequate states
HArena *arena;
HAllocator *mm__;
} HLRTable;
typedef struct HLREnhGrammar_ {
HCFGrammar *grammar; // enhanced grammar
HHashTable *tmap; // maps transitions to enhanced-grammar symbols
HHashTable *smap; // maps enhanced-grammar symbols to transitions
HHashTable *corr; // maps symbols to sets of corresponding e. symbols
HArena *arena;
} HLREnhGrammar;
typedef struct HLREngine_ {
const HLRTable *table;
HSlist *left; // left stack; reductions happen here
HSlist *right; // right stack; input appears here
size_t state;
bool running;
HArena *arena; // will hold the results
HArena *tarena; // tmp, deleted after parse
} HLREngine;
// XXX move to internal.h or something
// XXX replace other hashtable iterations with this
#define H_FOREACH_(HT) { \
const HHashTable *ht__ = HT; \
for(size_t i__=0; i__ < ht__->capacity; i__++) { \
for(HHashTableEntry *hte__ = &ht__->contents[i__]; \
hte__; \
hte__ = hte__->next) { \
if(hte__->key == NULL) continue;
#define H_FOREACH_KEY(HT, KEYVAR) H_FOREACH_(HT) \
const KEYVAR = hte__->key;
#define H_FOREACH(HT, KEYVAR, VALVAR) H_FOREACH_KEY(HT, KEYVAR) \
VALVAR = hte__->value;
#define H_END_FOREACH \
} \
} \
}
// compare symbols - terminals by value, others by pointer
static bool eq_symbol(const void *p, const void *q)
{
const HCFChoice *x=p, *y=q;
return (x==y
|| (x->type==HCF_END && y->type==HCF_END)
|| (x->type==HCF_CHAR && y->type==HCF_CHAR && x->chr==y->chr));
}
// hash symbols - terminals by value, others by pointer
static HHashValue hash_symbol(const void *p)
{
const HCFChoice *x=p;
if(x->type == HCF_END)
return 0;
else if(x->type == HCF_CHAR)
return x->chr * 33;
else
return h_hash_ptr(p);
}
// compare LALR items by value
static bool eq_lalr_item(const void *p, const void *q)
{
const HLRItem *a=p, *b=q;
if(!eq_symbol(a->lhs, b->lhs)) return false;
if(a->mark != b->mark) return false;
if(a->len != b->len) return false;
for(size_t i=0; i<a->len; i++)
if(!eq_symbol(a->rhs[i], b->rhs[i])) return false;
return true;
}
// compare LALR item sets (DFA states)
static inline bool eq_lalr_itemset(const void *p, const void *q)
{
return h_hashset_equal(p, q);
}
// hash LALR items
static inline HHashValue hash_lalr_item(const void *p)
{
const HLRItem *x = p;
HHashValue hash = 0;
hash += hash_symbol(x->lhs);
for(HCFChoice **p=x->rhs; *p; p++)
hash += hash_symbol(*p);
hash += x->mark;
return hash;
}
// hash LALR item sets (DFA states) - hash the elements and sum
static HHashValue hash_lalr_itemset(const void *p)
{
HHashValue hash = 0;
H_FOREACH_KEY((const HHashSet *)p, HLRItem *item)
hash += hash_lalr_item(item);
H_END_FOREACH
return hash;
}
HLRItem *h_lritem_new(HArena *a, HCFChoice *lhs, HCFChoice **rhs, size_t mark)
{
HLRItem *ret = h_arena_malloc(a, sizeof(HLRItem));
size_t len = 0;
for(HCFChoice **p=rhs; *p; p++) len++;
assert(mark <= len);
ret->lhs = lhs;
ret->rhs = rhs;
ret->len = len;
ret->mark = mark;
return ret;
}
static inline HLRState *h_lrstate_new(HArena *arena)
{
return h_hashset_new(arena, eq_lalr_item, hash_lalr_item);
}
HLRTable *h_lrtable_new(HAllocator *mm__, size_t nrows)
{
HArena *arena = h_new_arena(mm__, 0); // default blocksize
assert(arena != NULL);
HLRTable *ret = h_new(HLRTable, 1);
ret->nrows = nrows;
ret->rows = h_arena_malloc(arena, nrows * sizeof(HHashTable *));
ret->forall = h_arena_malloc(arena, nrows * sizeof(HLRAction *));
ret->inadeq = h_slist_new(arena);
ret->arena = arena;
ret->mm__ = mm__;
for(size_t i=0; i<nrows; i++) {
ret->rows[i] = h_hashtable_new(arena, eq_symbol, hash_symbol);
ret->forall[i] = NULL;
}
return ret;
}
void h_lrtable_free(HLRTable *table)
{
HAllocator *mm__ = table->mm__;
h_delete_arena(table->arena);
h_free(table);
}
/* Constructing the characteristic automaton (handle recognizer) */
static HLRItem *advance_mark(HArena *arena, const HLRItem *item)
{
assert(item->rhs[item->mark] != NULL);
HLRItem *ret = h_arena_malloc(arena, sizeof(HLRItem));
*ret = *item;
ret->mark++;
return ret;
}
static void expand_to_closure(HCFGrammar *g, HHashSet *items)
{
HAllocator *mm__ = g->mm__;
HArena *arena = g->arena;
HSlist *work = h_slist_new(arena);
// initialize work list with items
H_FOREACH_KEY(items, HLRItem *item)
h_slist_push(work, (void *)item);
H_END_FOREACH
while(!h_slist_empty(work)) {
const HLRItem *item = h_slist_pop(work);
HCFChoice *sym = item->rhs[item->mark]; // symbol after mark
// if there is a non-terminal after the mark, follow it
// NB: unlike LLk, we do consider HCF_CHARSET a non-terminal here
if(sym != NULL && (sym->type==HCF_CHOICE || sym->type==HCF_CHARSET)) {
// add items corresponding to the productions of sym
if(sym->type == HCF_CHOICE) {
for(HCFSequence **p=sym->seq; *p; p++) {
HLRItem *it = h_lritem_new(arena, sym, (*p)->items, 0);
if(!h_hashset_present(items, it)) {
h_hashset_put(items, it);
h_slist_push(work, it);
}
}
} else { // HCF_CHARSET
for(unsigned int i=0; i<256; i++) {
if(charset_isset(sym->charset, i)) {
// XXX allocate these single-character symbols statically somewhere
HCFChoice **rhs = h_new(HCFChoice *, 2);
rhs[0] = h_new(HCFChoice, 1);
rhs[0]->type = HCF_CHAR;
rhs[0]->chr = i;
rhs[1] = NULL;
HLRItem *it = h_lritem_new(arena, sym, rhs, 0);
h_hashset_put(items, it);
// single-character item needs no further work
}
}
// if sym is a non-terminal, we need a reshape on it
// this seems as good a place as any to set it
sym->reshape = h_act_first;
}
}
}
}
HLRDFA *h_lr0_dfa(HCFGrammar *g)
{
HArena *arena = g->arena;
HHashSet *states = h_hashset_new(arena, eq_lalr_itemset, hash_lalr_itemset);
// maps itemsets to assigned array indices
HSlist *transitions = h_slist_new(arena);
// list of states that need to be processed
// to save lookups, we push two elements per state, the itemset and its
// assigned index.
HSlist *work = h_slist_new(arena);
// make initial state (kernel)
HLRState *start = h_lrstate_new(arena);
assert(g->start->type == HCF_CHOICE);
for(HCFSequence **p=g->start->seq; *p; p++)
h_hashset_put(start, h_lritem_new(arena, g->start, (*p)->items, 0));
expand_to_closure(g, start);
h_hashtable_put(states, start, 0);
h_slist_push(work, start);
h_slist_push(work, 0);
// while work to do (on some state)
// determine edge symbols
// for each edge symbol:
// advance respective items -> destination state (kernel)
// compute closure
// if destination is a new state:
// add it to state set
// add transition to it
// add it to the work list
while(!h_slist_empty(work)) {
size_t state_idx = (uintptr_t)h_slist_pop(work);
HLRState *state = h_slist_pop(work);
// maps edge symbols to neighbor states (item sets) of s
HHashTable *neighbors = h_hashtable_new(arena, eq_symbol, hash_symbol);
// iterate over state (closure) and generate neighboring sets
H_FOREACH_KEY(state, HLRItem *item)
HCFChoice *sym = item->rhs[item->mark]; // symbol after mark
if(sym != NULL) { // mark was not at the end
// find or create prospective neighbor set
HLRState *neighbor = h_hashtable_get(neighbors, sym);
if(neighbor == NULL) {
neighbor = h_lrstate_new(arena);
h_hashtable_put(neighbors, sym, neighbor);
}
// ...and add the advanced item to it
h_hashset_put(neighbor, advance_mark(arena, item));
}
H_END_FOREACH
// merge expanded neighbor sets into the set of existing states
H_FOREACH(neighbors, HCFChoice *symbol, HLRState *neighbor)
expand_to_closure(g, neighbor);
// look up existing state, allocate new if not found
size_t neighbor_idx;
if(!h_hashset_present(states, neighbor)) {
neighbor_idx = states->used;
h_hashtable_put(states, neighbor, (void *)(uintptr_t)neighbor_idx);
h_slist_push(work, neighbor);
h_slist_push(work, (void *)(uintptr_t)neighbor_idx);
} else {
neighbor_idx = (uintptr_t)h_hashtable_get(states, neighbor);
}
// add transition "state --symbol--> neighbor"
HLRTransition *t = h_arena_malloc(arena, sizeof(HLRTransition));
t->from = state_idx;
t->to = neighbor_idx;
t->symbol = symbol;
h_slist_push(transitions, t);
H_END_FOREACH
} // end while(work)
// fill DFA struct
HLRDFA *dfa = h_arena_malloc(arena, sizeof(HLRDFA));
dfa->nstates = states->used;
dfa->states = h_arena_malloc(arena, dfa->nstates*sizeof(HLRState *));
H_FOREACH(states, HLRState *state, void *v)
size_t idx = (uintptr_t)v;
dfa->states[idx] = state;
H_END_FOREACH
dfa->transitions = transitions;
return dfa;
}
/* LR(0) table generation */
static HLRAction *shift_action(HArena *arena, size_t nextstate)
{
HLRAction *action = h_arena_malloc(arena, sizeof(HLRAction));
action->type = HLR_SHIFT;
action->nextstate = nextstate;
return action;
}
static HLRAction *reduce_action(HArena *arena, const HLRItem *item)
{
HLRAction *action = h_arena_malloc(arena, sizeof(HLRAction));
action->type = HLR_REDUCE;
action->production.lhs = item->lhs;
action->production.length = item->len;
#ifndef NDEBUG
action->production.rhs = item->rhs;
#endif
return action;
}
HLRTable *h_lr0_table(HCFGrammar *g, const HLRDFA *dfa)
{
HAllocator *mm__ = g->mm__;
HLRTable *table = h_lrtable_new(mm__, dfa->nstates);
HArena *arena = table->arena;
// remember start symbol
table->start = g->start;
// add shift entries
for(HSlistNode *x = dfa->transitions->head; x; x = x->next) {
// for each transition x-A->y, add "shift, goto y" to table entry (x,A)
HLRTransition *t = x->elem;
HLRAction *action = shift_action(arena, t->to);
h_hashtable_put(table->rows[t->from], t->symbol, action);
}
// add reduce entries, record inadequate states
for(size_t i=0; i<dfa->nstates; i++) {
// find reducible items in state
H_FOREACH_KEY(dfa->states[i], HLRItem *item)
if(item->mark == item->len) { // mark at the end
// check for conflicts
// XXX store more informative stuff in the inadeq records?
if(table->forall[i]) {
// reduce/reduce conflict with a previous item
h_slist_push(table->inadeq, (void *)(uintptr_t)i);
} else if(!h_hashtable_empty(table->rows[i])) {
// shift/reduce conflict with one of the row's entries
h_slist_push(table->inadeq, (void *)(uintptr_t)i);
}
// set reduce action for the entire row
table->forall[i] = reduce_action(arena, item);
}
H_END_FOREACH
}
return table;
}
@ -499,19 +68,7 @@ static void transform_productions(const HLRTable *table, HLREnhGrammar *eg,
xAy->seq = seq; xAy->seq = seq;
} }
static bool eq_transition(const void *p, const void *q) static HCFChoice *new_enhanced_symbol(HLREnhGrammar *eg, const HCFChoice *sym)
{
const HLRTransition *a=p, *b=q;
return (a->from == b->from && a->to == b->to && eq_symbol(a->symbol, b->symbol));
}
static HHashValue hash_transition(const void *p)
{
const HLRTransition *t = p;
return (hash_symbol(t->symbol) + t->from + t->to); // XXX ?
}
HCFChoice *new_enhanced_symbol(HLREnhGrammar *eg, const HCFChoice *sym)
{ {
HArena *arena = eg->arena; HArena *arena = eg->arena;
HCFChoice *esym = h_arena_malloc(arena, sizeof(HCFChoice)); HCFChoice *esym = h_arena_malloc(arena, sizeof(HCFChoice));
@ -519,13 +76,14 @@ HCFChoice *new_enhanced_symbol(HLREnhGrammar *eg, const HCFChoice *sym)
HHashSet *cs = h_hashtable_get(eg->corr, sym); HHashSet *cs = h_hashtable_get(eg->corr, sym);
if(!cs) { if(!cs) {
cs = h_hashset_new(arena, eq_symbol, hash_symbol); cs = h_hashset_new(arena, h_eq_symbol, h_hash_symbol);
h_hashtable_put(eg->corr, sym, cs); h_hashtable_put(eg->corr, sym, cs);
} }
h_hashset_put(cs, esym); h_hashset_put(cs, esym);
return esym; return esym;
} }
static HLREnhGrammar *enhance_grammar(const HCFGrammar *g, const HLRDFA *dfa, static HLREnhGrammar *enhance_grammar(const HCFGrammar *g, const HLRDFA *dfa,
const HLRTable *table) const HLRTable *table)
{ {
@ -533,9 +91,9 @@ static HLREnhGrammar *enhance_grammar(const HCFGrammar *g, const HLRDFA *dfa,
HArena *arena = g->arena; HArena *arena = g->arena;
HLREnhGrammar *eg = h_arena_malloc(arena, sizeof(HLREnhGrammar)); HLREnhGrammar *eg = h_arena_malloc(arena, sizeof(HLREnhGrammar));
eg->tmap = h_hashtable_new(arena, eq_transition, hash_transition); eg->tmap = h_hashtable_new(arena, h_eq_transition, h_hash_transition);
eg->smap = h_hashtable_new(arena, h_eq_ptr, h_hash_ptr); eg->smap = h_hashtable_new(arena, h_eq_ptr, h_hash_ptr);
eg->corr = h_hashtable_new(arena, eq_symbol, hash_symbol); eg->corr = h_hashtable_new(arena, h_eq_symbol, h_hash_symbol);
// XXX must use h_eq/hash_ptr for symbols! so enhanced CHARs are different // XXX must use h_eq/hash_ptr for symbols! so enhanced CHARs are different
eg->arena = arena; eg->arena = arena;
@ -590,14 +148,14 @@ int h_lrtable_put(HLRTable *tbl, size_t state, HCFChoice *x, HLRAction *action)
// check whether a sequence of enhanced-grammar symbols (p) matches the given // check whether a sequence of enhanced-grammar symbols (p) matches the given
// (original-grammar) production rhs and terminates in the given end state. // (original-grammar) production rhs and terminates in the given end state.
bool match_production(HLREnhGrammar *eg, HCFChoice **p, static bool match_production(HLREnhGrammar *eg, HCFChoice **p,
HCFChoice **rhs, size_t endstate) HCFChoice **rhs, size_t endstate)
{ {
size_t state = endstate; // initialized to end in case of empty rhs size_t state = endstate; // initialized to end in case of empty rhs
for(; *p && *rhs; p++, rhs++) { for(; *p && *rhs; p++, rhs++) {
HLRTransition *t = h_hashtable_get(eg->smap, *p); HLRTransition *t = h_hashtable_get(eg->smap, *p);
assert(t != NULL); assert(t != NULL);
if(!eq_symbol(t->symbol, *rhs)) if(!h_eq_symbol(t->symbol, *rhs))
return false; return false;
state = t->to; state = t->to;
} }
@ -673,7 +231,7 @@ int h_lalr_compile(HAllocator* mm__, HParser* parser, const void* params)
continue; continue;
// action to place in the table cells indicated by lookahead // action to place in the table cells indicated by lookahead
HLRAction *action = reduce_action(arena, item); HLRAction *action = h_reduce_action(arena, item);
// find all LR(0)-enhanced productions matching item // find all LR(0)-enhanced productions matching item
HHashSet *lhss = h_hashtable_get(eg->corr, item->lhs); HHashSet *lhss = h_hashtable_get(eg->corr, item->lhs);
@ -729,304 +287,6 @@ void h_lalr_free(HParser *parser)
/* LR driver */
const HLRAction *
h_lr_lookup(const HLRTable *table, size_t state, const HCFChoice *symbol)
{
assert(state < table->nrows);
if(table->forall[state]) {
assert(h_hashtable_empty(table->rows[state])); // that would be a conflict
return table->forall[state];
} else {
return h_hashtable_get(table->rows[state], symbol);
}
}
HLREngine *h_lrengine_new(HArena *arena, HArena *tarena, const HLRTable *table)
{
HLREngine *engine = h_arena_malloc(tarena, sizeof(HLREngine));
engine->table = table;
engine->left = h_slist_new(tarena);
engine->right = h_slist_new(tarena);
engine->state = 0;
engine->running = 1;
engine->arena = arena;
engine->tarena = tarena;
return engine;
}
void h_lrengine_step(HLREngine *engine, HInputStream *stream)
{
// short-hand names
HSlist *left = engine->left;
HSlist *right = engine->right;
HArena *arena = engine->arena;
HArena *tarena = engine->tarena;
// stack layout:
// on the left stack, we put pairs: (saved state, semantic value)
// on the right stack, we put pairs: (symbol, semantic value)
// make sure there is input on the right stack
if(h_slist_empty(right)) {
// XXX use statically-allocated terminal symbols
HCFChoice *x = h_arena_malloc(tarena, sizeof(HCFChoice));
HParsedToken *v;
uint8_t c = h_read_bits(stream, 8, false);
if(stream->overrun) { // end of input
x->type = HCF_END;
v = NULL;
} else {
x->type = HCF_CHAR;
x->chr = c;
v = h_arena_malloc(arena, sizeof(HParsedToken));
v->token_type = TT_UINT;
v->uint = c;
}
h_slist_push(right, v);
h_slist_push(right, x);
}
// peek at input symbol on the right side
HCFChoice *symbol = right->head->elem;
// table lookup
const HLRAction *action = h_lr_lookup(engine->table, engine->state, symbol);
if(action == NULL) {
// no handle recognizable in input, terminate
engine->running = false;
return;
}
if(action->type == HLR_SHIFT) {
h_slist_push(left, (void *)(uintptr_t)engine->state);
h_slist_pop(right); // symbol (discard)
h_slist_push(left, h_slist_pop(right)); // semantic value
engine->state = action->nextstate;
} else {
assert(action->type == HLR_REDUCE);
size_t len = action->production.length;
HCFChoice *symbol = action->production.lhs;
// semantic value of the reduction result
HParsedToken *value = h_arena_malloc(arena, sizeof(HParsedToken));
value->token_type = TT_SEQUENCE;
value->seq = h_carray_new_sized(arena, len);
// pull values off the left stack, rewinding state accordingly
HParsedToken *v = NULL;
for(size_t i=0; i<len; i++) {
v = h_slist_pop(left);
engine->state = (uintptr_t)h_slist_pop(left);
// collect values in result sequence
value->seq->elements[len-1-i] = v;
value->seq->used++;
}
if(v) {
// result position equals position of left-most symbol
value->index = v->index;
value->bit_offset = v->bit_offset;
} else {
// XXX how to get the position in this case?
}
// perform token reshape if indicated
if(symbol->reshape)
value = (HParsedToken *)symbol->reshape(make_result(arena, value));
// call validation and semantic action, if present
if(symbol->pred && !symbol->pred(make_result(tarena, value))) {
// validation failed -> no parse; terminate
engine->running = false;
return;
}
if(symbol->action)
value = (HParsedToken *)symbol->action(make_result(arena, value));
// push result (value, symbol) onto the right stack
h_slist_push(right, value);
h_slist_push(right, symbol);
}
}
HParseResult *h_lrengine_result(HLREngine *engine)
{
// parsing was successful iff the start symbol is on top of the right stack
if(h_slist_pop(engine->right) == engine->table->start) {
// next on the right stack is the start symbol's semantic value
assert(!h_slist_empty(engine->right));
HParsedToken *tok = h_slist_pop(engine->right);
return make_result(engine->arena, tok);
} else {
return NULL;
}
}
HParseResult *h_lr_parse(HAllocator* mm__, const HParser* parser, HInputStream* stream)
{
HLRTable *table = parser->backend_data;
if(!table)
return NULL;
HArena *arena = h_new_arena(mm__, 0); // will hold the results
HArena *tarena = h_new_arena(mm__, 0); // tmp, deleted after parse
HLREngine *engine = h_lrengine_new(arena, tarena, table);
// run while the recognizer finds handles in the input
while(engine->running)
h_lrengine_step(engine, stream);
HParseResult *result = h_lrengine_result(engine);
if(!result)
h_delete_arena(arena);
h_delete_arena(tarena);
return result;
}
/* Pretty-printers */
void h_pprint_lritem(FILE *f, const HCFGrammar *g, const HLRItem *item)
{
h_pprint_symbol(f, g, item->lhs);
fputs(" ->", f);
HCFChoice **x = item->rhs;
HCFChoice **mark = item->rhs + item->mark;
if(*x == NULL) {
fputc('.', f);
} else {
while(*x) {
if(x == mark)
fputc('.', f);
else
fputc(' ', f);
if((*x)->type == HCF_CHAR) {
// condense character strings
fputc('"', f);
h_pprint_char(f, (*x)->chr);
for(x++; *x; x++) {
if(x == mark)
break;
if((*x)->type != HCF_CHAR)
break;
h_pprint_char(f, (*x)->chr);
}
fputc('"', f);
} else {
h_pprint_symbol(f, g, *x);
x++;
}
}
if(x == mark)
fputs(".", f);
}
}
void h_pprint_lrstate(FILE *f, const HCFGrammar *g,
const HLRState *state, unsigned int indent)
{
bool first = true;
H_FOREACH_KEY(state, HLRItem *item)
if(!first)
for(unsigned int i=0; i<indent; i++) fputc(' ', f);
first = false;
h_pprint_lritem(f, g, item);
fputc('\n', f);
H_END_FOREACH
}
static void pprint_transition(FILE *f, const HCFGrammar *g, const HLRTransition *t)
{
fputs("-", f);
h_pprint_symbol(f, g, t->symbol);
fprintf(f, "->%lu", t->to);
}
void h_pprint_lrdfa(FILE *f, const HCFGrammar *g,
const HLRDFA *dfa, unsigned int indent)
{
for(size_t i=0; i<dfa->nstates; i++) {
unsigned int indent2 = indent + fprintf(f, "%4lu: ", i);
h_pprint_lrstate(f, g, dfa->states[i], indent2);
for(HSlistNode *x = dfa->transitions->head; x; x = x->next) {
const HLRTransition *t = x->elem;
if(t->from == i) {
for(unsigned int i=0; i<indent2-2; i++) fputc(' ', f);
pprint_transition(f, g, t);
fputc('\n', f);
}
}
}
}
void pprint_lraction(FILE *f, const HCFGrammar *g, const HLRAction *action)
{
if(action->type == HLR_SHIFT) {
fprintf(f, "s%lu", action->nextstate);
} else {
fputs("r(", f);
h_pprint_symbol(f, g, action->production.lhs);
fputs(" -> ", f);
#ifdef NDEBUG
// if we can't print the production, at least print its length
fprintf(f, "[%lu]", action->production.length);
#else
HCFSequence seq = {action->production.rhs};
h_pprint_sequence(f, g, &seq);
#endif
fputc(')', f);
}
}
void h_pprint_lrtable(FILE *f, const HCFGrammar *g, const HLRTable *table,
unsigned int indent)
{
for(size_t i=0; i<table->nrows; i++) {
for(unsigned int j=0; j<indent; j++) fputc(' ', f);
fprintf(f, "%4lu:", i);
if(table->forall[i]) {
fputs(" - ", f);
pprint_lraction(f, g, table->forall[i]);
fputs(" -", f);
if(!h_hashtable_empty(table->rows[i]))
fputs(" !!", f);
}
H_FOREACH(table->rows[i], HCFChoice *symbol, HLRAction *action)
fputc(' ', f); // separator
h_pprint_symbol(f, g, symbol);
fputc(':', f);
if(table->forall[i]) {
fputc(action->type == HLR_SHIFT? 's' : 'r', f);
fputc('/', f);
fputc(table->forall[i]->type == HLR_SHIFT? 's' : 'r', f);
} else {
pprint_lraction(f, g, action);
}
H_END_FOREACH
fputc('\n', f);
}
#if 0
fputs("inadeq=", f);
for(HSlistNode *x=table->inadeq->head; x; x=x->next) {
fprintf(f, "%lu ", (uintptr_t)x->elem);
}
fputc('\n', f);
#endif
}
HParserBackendVTable h__lalr_backend_vtable = { HParserBackendVTable h__lalr_backend_vtable = {
.compile = h_lalr_compile, .compile = h_lalr_compile,
.parse = h_lr_parse, .parse = h_lr_parse,

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#include <assert.h>
#include "../parsers/parser_internal.h"
#include "lr.h"
/* Comparison and hashing functions */
// compare symbols - terminals by value, others by pointer
bool h_eq_symbol(const void *p, const void *q)
{
const HCFChoice *x=p, *y=q;
return (x==y
|| (x->type==HCF_END && y->type==HCF_END)
|| (x->type==HCF_CHAR && y->type==HCF_CHAR && x->chr==y->chr));
}
// hash symbols - terminals by value, others by pointer
HHashValue h_hash_symbol(const void *p)
{
const HCFChoice *x=p;
if(x->type == HCF_END)
return 0;
else if(x->type == HCF_CHAR)
return x->chr * 33;
else
return h_hash_ptr(p);
}
// compare LR items by value
static bool eq_lr_item(const void *p, const void *q)
{
const HLRItem *a=p, *b=q;
if(!h_eq_symbol(a->lhs, b->lhs)) return false;
if(a->mark != b->mark) return false;
if(a->len != b->len) return false;
for(size_t i=0; i<a->len; i++)
if(!h_eq_symbol(a->rhs[i], b->rhs[i])) return false;
return true;
}
// hash LALR items
static inline HHashValue hash_lr_item(const void *p)
{
const HLRItem *x = p;
HHashValue hash = 0;
hash += h_hash_symbol(x->lhs);
for(HCFChoice **p=x->rhs; *p; p++)
hash += h_hash_symbol(*p);
hash += x->mark;
return hash;
}
// compare item sets (DFA states)
bool h_eq_lr_itemset(const void *p, const void *q)
{
return h_hashset_equal(p, q);
}
// hash LR item sets (DFA states) - hash the elements and sum
HHashValue h_hash_lr_itemset(const void *p)
{
HHashValue hash = 0;
H_FOREACH_KEY((const HHashSet *)p, HLRItem *item)
hash += hash_lr_item(item);
H_END_FOREACH
return hash;
}
bool h_eq_transition(const void *p, const void *q)
{
const HLRTransition *a=p, *b=q;
return (a->from == b->from && a->to == b->to && h_eq_symbol(a->symbol, b->symbol));
}
HHashValue h_hash_transition(const void *p)
{
const HLRTransition *t = p;
return (h_hash_symbol(t->symbol) + t->from + t->to); // XXX ?
}
/* Constructors */
HLRItem *h_lritem_new(HArena *a, HCFChoice *lhs, HCFChoice **rhs, size_t mark)
{
HLRItem *ret = h_arena_malloc(a, sizeof(HLRItem));
size_t len = 0;
for(HCFChoice **p=rhs; *p; p++) len++;
assert(mark <= len);
ret->lhs = lhs;
ret->rhs = rhs;
ret->len = len;
ret->mark = mark;
return ret;
}
HLRState *h_lrstate_new(HArena *arena)
{
return h_hashset_new(arena, eq_lr_item, hash_lr_item);
}
HLRTable *h_lrtable_new(HAllocator *mm__, size_t nrows)
{
HArena *arena = h_new_arena(mm__, 0); // default blocksize
assert(arena != NULL);
HLRTable *ret = h_new(HLRTable, 1);
ret->nrows = nrows;
ret->rows = h_arena_malloc(arena, nrows * sizeof(HHashTable *));
ret->forall = h_arena_malloc(arena, nrows * sizeof(HLRAction *));
ret->inadeq = h_slist_new(arena);
ret->arena = arena;
ret->mm__ = mm__;
for(size_t i=0; i<nrows; i++) {
ret->rows[i] = h_hashtable_new(arena, h_eq_symbol, h_hash_symbol);
ret->forall[i] = NULL;
}
return ret;
}
void h_lrtable_free(HLRTable *table)
{
HAllocator *mm__ = table->mm__;
h_delete_arena(table->arena);
h_free(table);
}
HLRAction *h_shift_action(HArena *arena, size_t nextstate)
{
HLRAction *action = h_arena_malloc(arena, sizeof(HLRAction));
action->type = HLR_SHIFT;
action->nextstate = nextstate;
return action;
}
HLRAction *h_reduce_action(HArena *arena, const HLRItem *item)
{
HLRAction *action = h_arena_malloc(arena, sizeof(HLRAction));
action->type = HLR_REDUCE;
action->production.lhs = item->lhs;
action->production.length = item->len;
#ifndef NDEBUG
action->production.rhs = item->rhs;
#endif
return action;
}
/* LR driver */
const HLRAction *
h_lr_lookup(const HLRTable *table, size_t state, const HCFChoice *symbol)
{
assert(state < table->nrows);
if(table->forall[state]) {
assert(h_hashtable_empty(table->rows[state])); // that would be a conflict
return table->forall[state];
} else {
return h_hashtable_get(table->rows[state], symbol);
}
}
HLREngine *h_lrengine_new(HArena *arena, HArena *tarena, const HLRTable *table)
{
HLREngine *engine = h_arena_malloc(tarena, sizeof(HLREngine));
engine->table = table;
engine->left = h_slist_new(tarena);
engine->right = h_slist_new(tarena);
engine->state = 0;
engine->running = 1;
engine->arena = arena;
engine->tarena = tarena;
return engine;
}
void h_lrengine_step(HLREngine *engine, HInputStream *stream)
{
// short-hand names
HSlist *left = engine->left;
HSlist *right = engine->right;
HArena *arena = engine->arena;
HArena *tarena = engine->tarena;
// stack layout:
// on the left stack, we put pairs: (saved state, semantic value)
// on the right stack, we put pairs: (symbol, semantic value)
// make sure there is input on the right stack
if(h_slist_empty(right)) {
// XXX use statically-allocated terminal symbols
HCFChoice *x = h_arena_malloc(tarena, sizeof(HCFChoice));
HParsedToken *v;
uint8_t c = h_read_bits(stream, 8, false);
if(stream->overrun) { // end of input
x->type = HCF_END;
v = NULL;
} else {
x->type = HCF_CHAR;
x->chr = c;
v = h_arena_malloc(arena, sizeof(HParsedToken));
v->token_type = TT_UINT;
v->uint = c;
}
h_slist_push(right, v);
h_slist_push(right, x);
}
// peek at input symbol on the right side
HCFChoice *symbol = right->head->elem;
// table lookup
const HLRAction *action = h_lr_lookup(engine->table, engine->state, symbol);
if(action == NULL) {
// no handle recognizable in input, terminate
engine->running = false;
return;
}
if(action->type == HLR_SHIFT) {
h_slist_push(left, (void *)(uintptr_t)engine->state);
h_slist_pop(right); // symbol (discard)
h_slist_push(left, h_slist_pop(right)); // semantic value
engine->state = action->nextstate;
} else {
assert(action->type == HLR_REDUCE);
size_t len = action->production.length;
HCFChoice *symbol = action->production.lhs;
// semantic value of the reduction result
HParsedToken *value = h_arena_malloc(arena, sizeof(HParsedToken));
value->token_type = TT_SEQUENCE;
value->seq = h_carray_new_sized(arena, len);
// pull values off the left stack, rewinding state accordingly
HParsedToken *v = NULL;
for(size_t i=0; i<len; i++) {
v = h_slist_pop(left);
engine->state = (uintptr_t)h_slist_pop(left);
// collect values in result sequence
value->seq->elements[len-1-i] = v;
value->seq->used++;
}
if(v) {
// result position equals position of left-most symbol
value->index = v->index;
value->bit_offset = v->bit_offset;
} else {
// XXX how to get the position in this case?
}
// perform token reshape if indicated
if(symbol->reshape)
value = (HParsedToken *)symbol->reshape(make_result(arena, value));
// call validation and semantic action, if present
if(symbol->pred && !symbol->pred(make_result(tarena, value))) {
// validation failed -> no parse; terminate
engine->running = false;
return;
}
if(symbol->action)
value = (HParsedToken *)symbol->action(make_result(arena, value));
// push result (value, symbol) onto the right stack
h_slist_push(right, value);
h_slist_push(right, symbol);
}
}
HParseResult *h_lrengine_result(HLREngine *engine)
{
// parsing was successful iff the start symbol is on top of the right stack
if(h_slist_pop(engine->right) == engine->table->start) {
// next on the right stack is the start symbol's semantic value
assert(!h_slist_empty(engine->right));
HParsedToken *tok = h_slist_pop(engine->right);
return make_result(engine->arena, tok);
} else {
return NULL;
}
}
HParseResult *h_lr_parse(HAllocator* mm__, const HParser* parser, HInputStream* stream)
{
HLRTable *table = parser->backend_data;
if(!table)
return NULL;
HArena *arena = h_new_arena(mm__, 0); // will hold the results
HArena *tarena = h_new_arena(mm__, 0); // tmp, deleted after parse
HLREngine *engine = h_lrengine_new(arena, tarena, table);
// run while the recognizer finds handles in the input
while(engine->running)
h_lrengine_step(engine, stream);
HParseResult *result = h_lrengine_result(engine);
if(!result)
h_delete_arena(arena);
h_delete_arena(tarena);
return result;
}
/* Pretty-printers */
void h_pprint_lritem(FILE *f, const HCFGrammar *g, const HLRItem *item)
{
h_pprint_symbol(f, g, item->lhs);
fputs(" ->", f);
HCFChoice **x = item->rhs;
HCFChoice **mark = item->rhs + item->mark;
if(*x == NULL) {
fputc('.', f);
} else {
while(*x) {
if(x == mark)
fputc('.', f);
else
fputc(' ', f);
if((*x)->type == HCF_CHAR) {
// condense character strings
fputc('"', f);
h_pprint_char(f, (*x)->chr);
for(x++; *x; x++) {
if(x == mark)
break;
if((*x)->type != HCF_CHAR)
break;
h_pprint_char(f, (*x)->chr);
}
fputc('"', f);
} else {
h_pprint_symbol(f, g, *x);
x++;
}
}
if(x == mark)
fputs(".", f);
}
}
void h_pprint_lrstate(FILE *f, const HCFGrammar *g,
const HLRState *state, unsigned int indent)
{
bool first = true;
H_FOREACH_KEY(state, HLRItem *item)
if(!first)
for(unsigned int i=0; i<indent; i++) fputc(' ', f);
first = false;
h_pprint_lritem(f, g, item);
fputc('\n', f);
H_END_FOREACH
}
static void pprint_transition(FILE *f, const HCFGrammar *g, const HLRTransition *t)
{
fputs("-", f);
h_pprint_symbol(f, g, t->symbol);
fprintf(f, "->%lu", t->to);
}
void h_pprint_lrdfa(FILE *f, const HCFGrammar *g,
const HLRDFA *dfa, unsigned int indent)
{
for(size_t i=0; i<dfa->nstates; i++) {
unsigned int indent2 = indent + fprintf(f, "%4lu: ", i);
h_pprint_lrstate(f, g, dfa->states[i], indent2);
for(HSlistNode *x = dfa->transitions->head; x; x = x->next) {
const HLRTransition *t = x->elem;
if(t->from == i) {
for(unsigned int i=0; i<indent2-2; i++) fputc(' ', f);
pprint_transition(f, g, t);
fputc('\n', f);
}
}
}
}
void pprint_lraction(FILE *f, const HCFGrammar *g, const HLRAction *action)
{
if(action->type == HLR_SHIFT) {
fprintf(f, "s%lu", action->nextstate);
} else {
fputs("r(", f);
h_pprint_symbol(f, g, action->production.lhs);
fputs(" -> ", f);
#ifdef NDEBUG
// if we can't print the production, at least print its length
fprintf(f, "[%lu]", action->production.length);
#else
HCFSequence seq = {action->production.rhs};
h_pprint_sequence(f, g, &seq);
#endif
fputc(')', f);
}
}
void h_pprint_lrtable(FILE *f, const HCFGrammar *g, const HLRTable *table,
unsigned int indent)
{
for(size_t i=0; i<table->nrows; i++) {
for(unsigned int j=0; j<indent; j++) fputc(' ', f);
fprintf(f, "%4lu:", i);
if(table->forall[i]) {
fputs(" - ", f);
pprint_lraction(f, g, table->forall[i]);
fputs(" -", f);
if(!h_hashtable_empty(table->rows[i]))
fputs(" !!", f);
}
H_FOREACH(table->rows[i], HCFChoice *symbol, HLRAction *action)
fputc(' ', f); // separator
h_pprint_symbol(f, g, symbol);
fputc(':', f);
if(table->forall[i]) {
fputc(action->type == HLR_SHIFT? 's' : 'r', f);
fputc('/', f);
fputc(table->forall[i]->type == HLR_SHIFT? 's' : 'r', f);
} else {
pprint_lraction(f, g, action);
}
H_END_FOREACH
fputc('\n', f);
}
#if 0
fputs("inadeq=", f);
for(HSlistNode *x=table->inadeq->head; x; x=x->next) {
fprintf(f, "%lu ", (uintptr_t)x->elem);
}
fputc('\n', f);
#endif
}

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#ifndef HAMMER_BACKENDS_LR__H
#define HAMMER_BACKENDS_LR__H
#include "../hammer.h"
#include "../cfgrammar.h"
#include "../internal.h"
typedef HHashSet HLRState; // states are sets of LRItems
typedef struct HLRDFA_ {
size_t nstates;
const HLRState **states; // array of size nstates
HSlist *transitions;
} HLRDFA;
typedef struct HLRTransition_ {
size_t from; // index into 'states' array
const HCFChoice *symbol;
size_t to; // index into 'states' array
} HLRTransition;
typedef struct HLRItem_ {
HCFChoice *lhs;
HCFChoice **rhs; // NULL-terminated
size_t len; // number of elements in rhs
size_t mark;
} HLRItem;
typedef struct HLRAction_ {
enum {HLR_SHIFT, HLR_REDUCE} type;
union {
size_t nextstate; // used with SHIFT
struct {
HCFChoice *lhs; // symbol carrying semantic actions etc.
size_t length; // # of symbols in rhs
#ifndef NDEBUG
HCFChoice **rhs; // NB: the rhs symbols are not needed for the parse
#endif
} production; // used with REDUCE
};
} HLRAction;
typedef struct HLRTable_ {
size_t nrows;
HHashTable **rows; // map symbols to HLRActions
HLRAction **forall; // shortcut to set an action for an entire row
HCFChoice *start; // start symbol
HSlist *inadeq; // indices of any inadequate states
HArena *arena;
HAllocator *mm__;
} HLRTable;
typedef struct HLREnhGrammar_ {
HCFGrammar *grammar; // enhanced grammar
HHashTable *tmap; // maps transitions to enhanced-grammar symbols
HHashTable *smap; // maps enhanced-grammar symbols to transitions
HHashTable *corr; // maps symbols to sets of corresponding e. symbols
HArena *arena;
} HLREnhGrammar;
typedef struct HLREngine_ {
const HLRTable *table;
HSlist *left; // left stack; reductions happen here
HSlist *right; // right stack; input appears here
size_t state;
bool running;
HArena *arena; // will hold the results
HArena *tarena; // tmp, deleted after parse
} HLREngine;
// XXX move to internal.h or something
// XXX replace other hashtable iterations with this
#define H_FOREACH_(HT) { \
const HHashTable *ht__ = HT; \
for(size_t i__=0; i__ < ht__->capacity; i__++) { \
for(HHashTableEntry *hte__ = &ht__->contents[i__]; \
hte__; \
hte__ = hte__->next) { \
if(hte__->key == NULL) continue;
#define H_FOREACH_KEY(HT, KEYVAR) H_FOREACH_(HT) \
const KEYVAR = hte__->key;
#define H_FOREACH(HT, KEYVAR, VALVAR) H_FOREACH_KEY(HT, KEYVAR) \
VALVAR = hte__->value;
#define H_END_FOREACH \
} \
} \
}
HLRItem *h_lritem_new(HArena *a, HCFChoice *lhs, HCFChoice **rhs, size_t mark);
HLRState *h_lrstate_new(HArena *arena);
HLRTable *h_lrtable_new(HAllocator *mm__, size_t nrows);
void h_lrtable_free(HLRTable *table);
HLREngine *h_lrengine_new(HArena *arena, HArena *tarena, const HLRTable *table);
HLRAction *h_reduce_action(HArena *arena, const HLRItem *item);
HLRAction *h_shift_action(HArena *arena, size_t nextstate);
bool h_eq_symbol(const void *p, const void *q);
bool h_eq_lr_itemset(const void *p, const void *q);
bool h_eq_transition(const void *p, const void *q);
HHashValue h_hash_symbol(const void *p);
HHashValue h_hash_lr_itemset(const void *p);
HHashValue h_hash_transition(const void *p);
HLRDFA *h_lr0_dfa(HCFGrammar *g);
HLRTable *h_lr0_table(HCFGrammar *g, const HLRDFA *dfa);
int h_lrtable_put(HLRTable *tbl, size_t state, HCFChoice *x, HLRAction *action);
int h_lalr_compile(HAllocator* mm__, HParser* parser, const void* params);
void h_lalr_free(HParser *parser);
const HLRAction *h_lr_lookup(const HLRTable *table, size_t state, const HCFChoice *symbol);
void h_lrengine_step(HLREngine *engine, HInputStream *stream);
HParseResult *h_lrengine_result(HLREngine *engine);
HParseResult *h_lr_parse(HAllocator* mm__, const HParser* parser, HInputStream* stream);
void h_pprint_lritem(FILE *f, const HCFGrammar *g, const HLRItem *item);
void h_pprint_lrstate(FILE *f, const HCFGrammar *g,
const HLRState *state, unsigned int indent);
void h_pprint_lrdfa(FILE *f, const HCFGrammar *g,
const HLRDFA *dfa, unsigned int indent);
void h_pprint_lrtable(FILE *f, const HCFGrammar *g, const HLRTable *table,
unsigned int indent);
#endif

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#include <assert.h>
#include "lr.h"
/* Constructing the characteristic automaton (handle recognizer) */
static HLRItem *advance_mark(HArena *arena, const HLRItem *item)
{
assert(item->rhs[item->mark] != NULL);
HLRItem *ret = h_arena_malloc(arena, sizeof(HLRItem));
*ret = *item;
ret->mark++;
return ret;
}
static void expand_to_closure(HCFGrammar *g, HHashSet *items)
{
HAllocator *mm__ = g->mm__;
HArena *arena = g->arena;
HSlist *work = h_slist_new(arena);
// initialize work list with items
H_FOREACH_KEY(items, HLRItem *item)
h_slist_push(work, (void *)item);
H_END_FOREACH
while(!h_slist_empty(work)) {
const HLRItem *item = h_slist_pop(work);
HCFChoice *sym = item->rhs[item->mark]; // symbol after mark
// if there is a non-terminal after the mark, follow it
// NB: unlike LLk, we do consider HCF_CHARSET a non-terminal here
if(sym != NULL && (sym->type==HCF_CHOICE || sym->type==HCF_CHARSET)) {
// add items corresponding to the productions of sym
if(sym->type == HCF_CHOICE) {
for(HCFSequence **p=sym->seq; *p; p++) {
HLRItem *it = h_lritem_new(arena, sym, (*p)->items, 0);
if(!h_hashset_present(items, it)) {
h_hashset_put(items, it);
h_slist_push(work, it);
}
}
} else { // HCF_CHARSET
for(unsigned int i=0; i<256; i++) {
if(charset_isset(sym->charset, i)) {
// XXX allocate these single-character symbols statically somewhere
HCFChoice **rhs = h_new(HCFChoice *, 2);
rhs[0] = h_new(HCFChoice, 1);
rhs[0]->type = HCF_CHAR;
rhs[0]->chr = i;
rhs[1] = NULL;
HLRItem *it = h_lritem_new(arena, sym, rhs, 0);
h_hashset_put(items, it);
// single-character item needs no further work
}
}
// if sym is a non-terminal, we need a reshape on it
// this seems as good a place as any to set it
sym->reshape = h_act_first;
}
}
}
}
HLRDFA *h_lr0_dfa(HCFGrammar *g)
{
HArena *arena = g->arena;
HHashSet *states = h_hashset_new(arena, h_eq_lr_itemset, h_hash_lr_itemset);
// maps itemsets to assigned array indices
HSlist *transitions = h_slist_new(arena);
// list of states that need to be processed
// to save lookups, we push two elements per state, the itemset and its
// assigned index.
HSlist *work = h_slist_new(arena);
// make initial state (kernel)
HLRState *start = h_lrstate_new(arena);
assert(g->start->type == HCF_CHOICE);
for(HCFSequence **p=g->start->seq; *p; p++)
h_hashset_put(start, h_lritem_new(arena, g->start, (*p)->items, 0));
expand_to_closure(g, start);
h_hashtable_put(states, start, 0);
h_slist_push(work, start);
h_slist_push(work, 0);
// while work to do (on some state)
// determine edge symbols
// for each edge symbol:
// advance respective items -> destination state (kernel)
// compute closure
// if destination is a new state:
// add it to state set
// add transition to it
// add it to the work list
while(!h_slist_empty(work)) {
size_t state_idx = (uintptr_t)h_slist_pop(work);
HLRState *state = h_slist_pop(work);
// maps edge symbols to neighbor states (item sets) of s
HHashTable *neighbors = h_hashtable_new(arena, h_eq_symbol, h_hash_symbol);
// iterate over state (closure) and generate neighboring sets
H_FOREACH_KEY(state, HLRItem *item)
HCFChoice *sym = item->rhs[item->mark]; // symbol after mark
if(sym != NULL) { // mark was not at the end
// find or create prospective neighbor set
HLRState *neighbor = h_hashtable_get(neighbors, sym);
if(neighbor == NULL) {
neighbor = h_lrstate_new(arena);
h_hashtable_put(neighbors, sym, neighbor);
}
// ...and add the advanced item to it
h_hashset_put(neighbor, advance_mark(arena, item));
}
H_END_FOREACH
// merge expanded neighbor sets into the set of existing states
H_FOREACH(neighbors, HCFChoice *symbol, HLRState *neighbor)
expand_to_closure(g, neighbor);
// look up existing state, allocate new if not found
size_t neighbor_idx;
if(!h_hashset_present(states, neighbor)) {
neighbor_idx = states->used;
h_hashtable_put(states, neighbor, (void *)(uintptr_t)neighbor_idx);
h_slist_push(work, neighbor);
h_slist_push(work, (void *)(uintptr_t)neighbor_idx);
} else {
neighbor_idx = (uintptr_t)h_hashtable_get(states, neighbor);
}
// add transition "state --symbol--> neighbor"
HLRTransition *t = h_arena_malloc(arena, sizeof(HLRTransition));
t->from = state_idx;
t->to = neighbor_idx;
t->symbol = symbol;
h_slist_push(transitions, t);
H_END_FOREACH
} // end while(work)
// fill DFA struct
HLRDFA *dfa = h_arena_malloc(arena, sizeof(HLRDFA));
dfa->nstates = states->used;
dfa->states = h_arena_malloc(arena, dfa->nstates*sizeof(HLRState *));
H_FOREACH(states, HLRState *state, void *v)
size_t idx = (uintptr_t)v;
dfa->states[idx] = state;
H_END_FOREACH
dfa->transitions = transitions;
return dfa;
}
/* LR(0) table generation */
HLRTable *h_lr0_table(HCFGrammar *g, const HLRDFA *dfa)
{
HAllocator *mm__ = g->mm__;
HLRTable *table = h_lrtable_new(mm__, dfa->nstates);
HArena *arena = table->arena;
// remember start symbol
table->start = g->start;
// add shift entries
for(HSlistNode *x = dfa->transitions->head; x; x = x->next) {
// for each transition x-A->y, add "shift, goto y" to table entry (x,A)
HLRTransition *t = x->elem;
HLRAction *action = h_shift_action(arena, t->to);
h_hashtable_put(table->rows[t->from], t->symbol, action);
}
// add reduce entries, record inadequate states
for(size_t i=0; i<dfa->nstates; i++) {
// find reducible items in state
H_FOREACH_KEY(dfa->states[i], HLRItem *item)
if(item->mark == item->len) { // mark at the end
// check for conflicts
// XXX store more informative stuff in the inadeq records?
if(table->forall[i]) {
// reduce/reduce conflict with a previous item
h_slist_push(table->inadeq, (void *)(uintptr_t)i);
} else if(!h_hashtable_empty(table->rows[i])) {
// shift/reduce conflict with one of the row's entries
h_slist_push(table->inadeq, (void *)(uintptr_t)i);
}
// set reduce action for the entire row
table->forall[i] = h_reduce_action(arena, item);
}
H_END_FOREACH
}
return table;
}