Fixing broken processing of horizontal matching across

long lines produced by @(freeform). Once the matching
passes about 4000 characters, the "consume_prefix"
function kicks in to save memory. Then any code which is
not properly written to handle this displaced situation
will break.

* match.c (h_text, h_var, h_coll, h_parallel, h_fun): Bugfix.
The recursive calls to match_line return an absolute position.
From this value we must subtract c->base if we are to
compare it with c->pos, or update c->pos.  If we use the
absolute value, we are abruptly jumping ahead in the data.

2 files changed, 24 insertions, 2 deletions

diff --git a/ChangeLog b/ChangeLog
index 55b06f15..65dcd162 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,18 @@
+2014-03-09  Kaz Kylheku  <kaz@kylheku.com>
+
+	Fixing broken processing of horizontal matching across
+	long lines produced by @(freeform). Once the matching
+	passes about 4000 characters, the "consume_prefix"
+	function kicks in to save memory. Then any code which is
+	not properly written to handle this displaced situation
+	will break.
+
+	* match.c (h_text, h_var, h_coll, h_parallel, h_fun): Bugfix.
+	The recursive calls to match_line return an absolute position.
+	From this value we must subtract c->base if we are to 
+	compare it with c->pos, or update c->pos.  If we use the
+	absolute value, we are abruptly jumping ahead in the data.
+
 2014-03-08  Kaz Kylheku  <kaz@kylheku.com>
 
 	Issue: match_regex and search_regex were continuing to feed characters
diff --git a/match.c b/match.c
index 9f11019c..0800ebc1 100644
--- a/match.c
+++ b/match.c
@@ -428,7 +428,7 @@ static val h_text(match_line_ctx *c)
   val new_pos = cdr(match_line(ml_specline(*c, texts)));
 
   if (new_pos) {
-    c->pos = new_pos;
+    c->pos = minus(new_pos, c->base);
     return next_spec_k;
   }
 
@@ -539,6 +539,8 @@ static val h_var(match_line_ctx *c)
       return nil;
     }
 
+    new_pos = minus(new_pos, c->base);
+
     LOG_MATCH("var spanning form", new_pos);
     if (sym)
       c->bindings = acons(sym, sub_str(c->dataline, c->pos, new_pos), new_bindings);
@@ -785,6 +787,8 @@ static val h_coll(match_line_ctx *c)
                    match_line(ml_bindings_specline(*c, new_bindings, spec)));
 
         if (until_pos) {
+          until_pos = minus(until_pos, c->base);
+
           LOG_MATCH("until/last", until_pos);
           if (sym == last_s) {
             last_bindings = set_diff(until_last_bindings,
@@ -802,6 +806,8 @@ static val h_coll(match_line_ctx *c)
         val strictly_new_bindings = set_diff(new_bindings,
                                              c->bindings, eq_f, nil);
         val have_new = strictly_new_bindings;
+
+        new_pos = minus(new_pos, c->base);
         LOG_MATCH("coll", new_pos);
 
         for (iter = vars; iter; iter = cdr(iter)) {
@@ -935,6 +941,7 @@ static val h_parallel(match_line_ctx *c)
 
     if (new_pos) {
       some_match = t;
+      new_pos = minus(new_pos, c->base);
 
       if (resolve_ub_vars) {
         val uiter;
@@ -1101,7 +1108,7 @@ static val h_fun(match_line_ctx *c)
           }
         }
 
-        c->pos = success;
+        c->pos = minus(success, c->base);
       }
     }