From bf9c9b5f7a7ffa5f81028c3c685afb7ba958a2b9 Mon Sep 17 00:00:00 2001
From: "Sven M. Hallberg" <pesco@khjk.org>
Date: Sat, 22 Jun 2013 12:51:25 +0200
Subject: [PATCH] refactoring in preparation for engine merging
---
src/backends/glr.c | 77 +++++++++++++++++++++++++++++++---------------
src/backends/lr.c | 1 +
src/backends/lr.h | 6 ++--
3 files changed, 57 insertions(+), 27 deletions(-)
diff --git a/src/backends/glr.c b/src/backends/glr.c
index 82ad5c06..2978e62d 100644
--- a/src/backends/glr.c
+++ b/src/backends/glr.c
@@ -43,6 +43,44 @@ HLREngine *fork_engine(const HLREngine *engine)
return eng2;
}
+static void stow_engine(HSlist *engines, HLREngine *engine)
+{
+ // XXX switch to one engine per state, and do the merge here
+ h_slist_push(engines, engine);
+}
+
+static const HLRAction *handle_conflict(HSlist *engines, const HLREngine *engine,
+ const HSlist *branches)
+{
+ // there should be at least two conflicting actions
+ assert(branches->head);
+ assert(branches->head->next); // this is just a consistency check
+
+ // fork a new engine for all but the first action
+ for(HSlistNode *x=branches->head->next; x; x=x->next) {
+ HLRAction *act = x->elem;
+ HLREngine *eng = fork_engine(engine);
+
+ // perform one step and add to list
+ h_lrengine_step(eng, act);
+ stow_engine(engines, eng);
+ }
+
+ // return first action for use with original engine
+ return branches->head->elem;
+}
+
+static HLREngine *handle_demerge(HSlist *engines, HLREngine *engine,
+ const HLRAction *reduce)
+{
+ return engine; // XXX
+
+ for(size_t i=0; i<reduce->production.length; i++) {
+ // XXX if stack hits bottom, demerge
+ }
+ // XXX call step and stow on the newly-created engines
+}
+
HParseResult *h_glr_parse(HAllocator* mm__, const HParser* parser, HInputStream* stream)
{
HLRTable *table = parser->backend_data;
@@ -60,12 +98,11 @@ HParseResult *h_glr_parse(HAllocator* mm__, const HParser* parser, HInputStream*
for(HSlistNode **x = &engines->head; *x; ) {
HLREngine *engine = (*x)->elem;
- // check for terminated engines
- if(engine->run) {
- x = &(*x)->next; // advance x with no change
- } else {
- *x = (*x)->next; // advance x, removing the current element
+ // remove engine from list; it may come back in below
+ *x = (*x)->next; // advance x, removing the current element
+ // drop those engines that have terminated
+ if(!engine->run) {
// check for parse success
HParseResult *res = h_lrengine_result(engine);
if(res)
@@ -76,29 +113,19 @@ HParseResult *h_glr_parse(HAllocator* mm__, const HParser* parser, HInputStream*
const HLRAction *action = h_lrengine_action(engine);
- // fork engine on conflicts
- if(action && action->type == HLR_CONFLICT) {
- const HSlist *branches = action->branches;
-
- // there should be at least two conflicting actions
- assert(branches->head);
- assert(branches->head->next);
-
- // save first action for use with old engine below
- action = branches->head->elem;
-
- // fork a new engine for all the other actions
- for(HSlistNode *x=branches->head->next; x; x=x->next) {
- HLRAction *act = x->elem;
- HLREngine *eng = fork_engine(engine);
-
- // perform one step and add to list
- h_lrengine_step(eng, act);
- h_slist_push(engines, eng);
- }
+ // handle forks and demerges (~> spawn engines)
+ if(action) {
+ if(action->type == HLR_CONFLICT) {
+ // fork engine on conflicts
+ action = handle_conflict(engines, engine, action->branches);
+ } else if(action->type == HLR_REDUCE) {
+ // demerge as needed to ensure that stacks are deep enough
+ engine = handle_demerge(engines, engine, action);
+ }
}
h_lrengine_step(engine, action);
+ stow_engine(engines, engine);
}
}
diff --git a/src/backends/lr.c b/src/backends/lr.c
index ca45582d..bb20f714 100644
--- a/src/backends/lr.c
+++ b/src/backends/lr.c
@@ -209,6 +209,7 @@ HLREngine *h_lrengine_new(HArena *arena, HArena *tarena, const HLRTable *table,
engine->run = true;
engine->stack = h_slist_new(tarena);
engine->input = *stream;
+ engine->merged = NULL;
engine->arena = arena;
engine->tarena = tarena;
diff --git a/src/backends/lr.h b/src/backends/lr.h
index 1158542b..5febc247 100644
--- a/src/backends/lr.h
+++ b/src/backends/lr.h
@@ -74,8 +74,10 @@ typedef struct HLREngine_ {
HSlist *stack; // holds pairs: (saved state, semantic value)
HInputStream input;
- HArena *arena; // will hold the results
- HArena *tarena; // tmp, deleted after parse
+ HSlist *merged; // saved ancestor engines that merged to form this one
+
+ HArena *arena; // will hold the results
+ HArena *tarena; // tmp, deleted after parse
} HLREngine;
--
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