factor out a struct HLREngine
This commit is contained in:
Sven M. Hallberg
parent
3e85648844
commit
7eff4b8d94
1 changed files with 141 additions and 100 deletions
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@ -61,6 +61,16 @@ typedef struct HLREnhGrammar_ {
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HArena *arena;
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} HLREnhGrammar;
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typedef struct HLREngine_ {
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const HLRTable *table;
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HSlist *left; // left stack; reductions happen here
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HSlist *right; // right stack; input appears here
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size_t state;
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bool running;
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HArena *arena; // will hold the results
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HArena *tarena; // tmp, deleted after parse
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} HLREngine;
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// XXX move to internal.h or something
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// XXX replace other hashtable iterations with this
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@ -733,6 +743,132 @@ h_lr_lookup(const HLRTable *table, size_t state, const HCFChoice *symbol)
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}
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}
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HLREngine *h_lrengine_new(HArena *arena, HArena *tarena, const HLRTable *table)
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{
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HLREngine *engine = h_arena_malloc(tarena, sizeof(HLREngine));
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engine->table = table;
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engine->left = h_slist_new(tarena);
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engine->right = h_slist_new(tarena);
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engine->state = 0;
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engine->running = 1;
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engine->arena = arena;
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engine->tarena = tarena;
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return engine;
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}
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void h_lrengine_step(HLREngine *engine, HInputStream *stream)
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{
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// short-hand names
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HSlist *left = engine->left;
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HSlist *right = engine->right;
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HArena *arena = engine->arena;
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HArena *tarena = engine->tarena;
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// stack layout:
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// on the left stack, we put pairs: (saved state, semantic value)
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// on the right stack, we put pairs: (symbol, semantic value)
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// make sure there is input on the right stack
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if(h_slist_empty(right)) {
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// XXX use statically-allocated terminal symbols
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HCFChoice *x = h_arena_malloc(tarena, sizeof(HCFChoice));
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HParsedToken *v;
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uint8_t c = h_read_bits(stream, 8, false);
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if(stream->overrun) { // end of input
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x->type = HCF_END;
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v = NULL;
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} else {
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x->type = HCF_CHAR;
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x->chr = c;
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v = h_arena_malloc(arena, sizeof(HParsedToken));
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v->token_type = TT_UINT;
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v->uint = c;
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}
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h_slist_push(right, v);
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h_slist_push(right, x);
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}
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// peek at input symbol on the right side
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HCFChoice *symbol = right->head->elem;
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// table lookup
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const HLRAction *action = h_lr_lookup(engine->table, engine->state, symbol);
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if(action == NULL) {
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// no handle recognizable in input, terminate
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engine->running = false;
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return;
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}
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if(action->type == HLR_SHIFT) {
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h_slist_push(left, (void *)(uintptr_t)engine->state);
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h_slist_pop(right); // symbol (discard)
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h_slist_push(left, h_slist_pop(right)); // semantic value
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engine->state = action->nextstate;
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} else {
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assert(action->type == HLR_REDUCE);
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size_t len = action->production.length;
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HCFChoice *symbol = action->production.lhs;
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// semantic value of the reduction result
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HParsedToken *value = h_arena_malloc(arena, sizeof(HParsedToken));
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value->token_type = TT_SEQUENCE;
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value->seq = h_carray_new_sized(arena, len);
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// pull values off the left stack, rewinding state accordingly
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HParsedToken *v = NULL;
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for(size_t i=0; i<len; i++) {
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v = h_slist_pop(left);
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engine->state = (uintptr_t)h_slist_pop(left);
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// collect values in result sequence
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value->seq->elements[len-1-i] = v;
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value->seq->used++;
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}
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if(v) {
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// result position equals position of left-most symbol
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value->index = v->index;
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value->bit_offset = v->bit_offset;
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} else {
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// XXX how to get the position in this case?
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}
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// perform token reshape if indicated
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if(symbol->reshape)
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value = (HParsedToken *)symbol->reshape(make_result(arena, value));
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// call validation and semantic action, if present
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if(symbol->pred && !symbol->pred(make_result(tarena, value))) {
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// validation failed -> no parse; terminate
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engine->running = false;
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return;
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}
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if(symbol->action)
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value = (HParsedToken *)symbol->action(make_result(arena, value));
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// push result (value, symbol) onto the right stack
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h_slist_push(right, value);
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h_slist_push(right, symbol);
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}
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}
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HParseResult *h_lrengine_result(HLREngine *engine)
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{
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// parsing was successful iff the start symbol is on top of the right stack
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if(h_slist_pop(engine->right) == engine->table->start) {
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// next on the right stack is the start symbol's semantic value
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assert(!h_slist_empty(engine->right));
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HParsedToken *tok = h_slist_pop(engine->right);
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return make_result(engine->arena, tok);
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} else {
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return NULL;
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}
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}
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HParseResult *h_lr_parse(HAllocator* mm__, const HParser* parser, HInputStream* stream)
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{
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HLRTable *table = parser->backend_data;
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@ -741,110 +877,15 @@ HParseResult *h_lr_parse(HAllocator* mm__, const HParser* parser, HInputStream*
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HArena *arena = h_new_arena(mm__, 0); // will hold the results
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HArena *tarena = h_new_arena(mm__, 0); // tmp, deleted after parse
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HSlist *left = h_slist_new(tarena); // left stack; reductions happen here
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HSlist *right = h_slist_new(tarena); // right stack; input appears here
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// stack layout:
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// on the left stack, we put pairs: (saved state, semantic value)
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// on the right stack, we put pairs: (symbol, semantic value)
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HLREngine *engine = h_lrengine_new(arena, tarena, table);
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// run while the recognizer finds handles in the input
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size_t state = 0;
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while(1) {
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// make sure there is input on the right stack
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if(h_slist_empty(right)) {
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// XXX use statically-allocated terminal symbols
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HCFChoice *x = h_arena_malloc(tarena, sizeof(HCFChoice));
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HParsedToken *v;
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while(engine->running)
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h_lrengine_step(engine, stream);
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uint8_t c = h_read_bits(stream, 8, false);
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if(stream->overrun) { // end of input
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x->type = HCF_END;
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v = NULL;
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} else {
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x->type = HCF_CHAR;
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x->chr = c;
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v = h_arena_malloc(arena, sizeof(HParsedToken));
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v->token_type = TT_UINT;
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v->uint = c;
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}
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h_slist_push(right, v);
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h_slist_push(right, x);
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}
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// peek at input symbol on the right side
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HCFChoice *symbol = right->head->elem;
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// table lookup
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const HLRAction *action = h_lr_lookup(table, state, symbol);
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if(action == NULL)
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break; // no handle recognizable in input, terminate parsing
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if(action->type == HLR_SHIFT) {
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h_slist_push(left, (void *)(uintptr_t)state);
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h_slist_pop(right); // symbol (discard)
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h_slist_push(left, h_slist_pop(right)); // semantic value
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state = action->nextstate;
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} else {
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assert(action->type == HLR_REDUCE);
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size_t len = action->production.length;
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HCFChoice *symbol = action->production.lhs;
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// semantic value of the reduction result
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HParsedToken *value = h_arena_malloc(arena, sizeof(HParsedToken));
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value->token_type = TT_SEQUENCE;
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value->seq = h_carray_new_sized(arena, len);
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// pull values off the left stack, rewinding state accordingly
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HParsedToken *v = NULL;
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for(size_t i=0; i<len; i++) {
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v = h_slist_pop(left);
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state = (uintptr_t)h_slist_pop(left);
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// collect values in result sequence
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value->seq->elements[len-1-i] = v;
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value->seq->used++;
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}
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if(v) {
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// result position equals position of left-most symbol
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value->index = v->index;
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value->bit_offset = v->bit_offset;
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} else {
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// XXX how to get the position in this case?
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}
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// perform token reshape if indicated
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if(symbol->reshape)
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value = (HParsedToken *)symbol->reshape(make_result(arena, value));
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// call validation and semantic action, if present
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if(symbol->pred && !symbol->pred(make_result(tarena, value)))
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break; // validation failed -> no parse
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if(symbol->action)
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value = (HParsedToken *)symbol->action(make_result(arena, value));
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// push result (value, symbol) onto the right stack
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h_slist_push(right, value);
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h_slist_push(right, symbol);
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}
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}
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// parsing was successful iff the start symbol is on top of the right stack
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HParseResult *result = NULL;
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if(h_slist_pop(right) == table->start) {
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// next on the right stack is the start symbol's semantic value
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assert(!h_slist_empty(right));
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HParsedToken *tok = h_slist_pop(right);
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result = make_result(arena, tok);
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} else {
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HParseResult *result = h_lrengine_result(engine);
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if(!result)
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h_delete_arena(arena);
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result = NULL;
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}
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h_delete_arena(tarena);
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return result;
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}
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