From 127600425054788c121fa4be3831cf09d2c636d5 Mon Sep 17 00:00:00 2001
From: "Sven M. Hallberg" <pesco@khjk.org>
Date: Fri, 4 Sep 2015 21:05:56 +0200
Subject: [PATCH] handle suspend on lookahead at the very end of the chunk
---
src/backends/llk.c | 27 ++++++++++++++++-----------
src/cfgrammar.c | 11 ++++++++---
src/cfgrammar.h | 3 +++
3 files changed, 27 insertions(+), 14 deletions(-)
diff --git a/src/backends/llk.c b/src/backends/llk.c
index 9acf67ec..95289975 100644
--- a/src/backends/llk.c
+++ b/src/backends/llk.c
@@ -296,7 +296,7 @@ static HLLkState *llk_parse_start_(HAllocator* mm__, const HParser* parser)
return s;
}
-// returns partial result or NULL
+// returns partial result or NULL (no parse)
static HCountedArray *llk_parse_chunk_(HLLkState *s, const HParser* parser,
HInputStream* stream)
{
@@ -316,6 +316,8 @@ static HCountedArray *llk_parse_chunk_(HLLkState *s, const HParser* parser,
// when we empty the stack, the parse is complete.
while(!h_slist_empty(stack)) {
+ tok = NULL;
+
// pop top of stack for inspection
x = h_slist_pop(stack);
assert(x != NULL);
@@ -323,22 +325,24 @@ static HCountedArray *llk_parse_chunk_(HLLkState *s, const HParser* parser,
if(x != MARK && x->type == HCF_CHOICE) {
// x is a nonterminal; apply the appropriate production and continue
- // push stack frame
- h_slist_push(stack, seq); // save current partial value
- h_slist_push(stack, x); // save the nonterminal
- h_slist_push(stack, MARK); // frame delimiter
-
- // open a fresh result sequence
- seq = h_carray_new(arena);
-
// look up applicable production in parse table
const HCFSequence *p = h_llk_lookup(table, x, stream);
if(p == NULL)
goto no_parse;
+ if(p == H_NEED_INPUT)
+ goto need_input;
// an infinite loop case that shouldn't happen
assert(!p->items[0] || p->items[0] != x);
+ // push stack frame
+ h_slist_push(stack, seq); // save current partial value
+ h_slist_push(stack, x); // save the nonterminal
+ h_slist_push(stack, MARK); // frame delimiter
+
+ // open a fresh result sequence
+ seq = h_carray_new(arena);
+
// push production's rhs onto the stack (in reverse order)
HCFChoice **s;
for(s = p->items; *s; s++);
@@ -433,8 +437,9 @@ static HCountedArray *llk_parse_chunk_(HLLkState *s, const HParser* parser,
need_input:
if(stream->last_chunk)
goto no_parse;
- h_arena_free(arena, tok); // no result, yet
- h_slist_push(stack, x); // try this symbol again next time
+ if(tok)
+ h_arena_free(arena, tok); // no result, yet
+ h_slist_push(stack, x); // try this symbol again next time
return seq;
}
diff --git a/src/cfgrammar.c b/src/cfgrammar.c
index a8761b8d..117009a5 100644
--- a/src/cfgrammar.c
+++ b/src/cfgrammar.c
@@ -349,6 +349,7 @@ void *h_stringmap_get(const HStringMap *m, const uint8_t *str, size_t n, bool en
return m->epsilon_branch;
}
+// A NULL result means no parse. H_NEED_INPUT means lookahead is too short.
void *h_stringmap_get_lookahead(const HStringMap *m, HInputStream lookahead)
{
while(m) {
@@ -362,9 +363,13 @@ void *h_stringmap_get_lookahead(const HStringMap *m, HInputStream lookahead)
// reading bits from it does not consume them from the real input.
uint8_t c = h_read_bits(&lookahead, 8, false);
- if (lookahead.overrun) { // end of input
- // XXX assumption of byte-wise grammar and input
- return m->end_branch;
+ if (lookahead.overrun) { // end of chunk
+ if (lookahead.last_chunk) { // end of input
+ // XXX assumption of byte-wise grammar and input
+ return m->end_branch;
+ } else {
+ return H_NEED_INPUT;
+ }
}
// no match yet, descend
diff --git a/src/cfgrammar.h b/src/cfgrammar.h
index 9cefc62e..2294d445 100644
--- a/src/cfgrammar.h
+++ b/src/cfgrammar.h
@@ -56,6 +56,9 @@ bool h_stringmap_empty(const HStringMap *m);
static inline HStringMap *h_stringmap_get_char(const HStringMap *m, const uint8_t c)
{ return h_hashtable_get(m->char_branches, (void *)char_key(c)); }
+// dummy return value used by h_stringmap_get_lookahead when out of input
+#define H_NEED_INPUT ((void *)&h_stringmap_get_lookahead)
+
/* Convert 'parser' into CFG representation by desugaring and compiling the set
* of nonterminals.
--
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