From 2c3a53fcc12e2435cb8950c146c1f7fe63949b72 Mon Sep 17 00:00:00 2001
From: Adrian Thurston <thurston@colm.net>
Date: Mon, 25 Jun 2018 10:34:35 +0700
Subject: limit the undoing of consumed data

When undoing the consume of make sure we don't send back more than we took out.
Once we hit the limit then move backwards to the previous stream, which we now
stash.
---
 src/input.c | 53 ++++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 38 insertions(+), 15 deletions(-)

(limited to 'src/input.c')

diff --git a/src/input.c b/src/input.c
index 6cdb7738..cd80d550 100644
--- a/src/input.c
+++ b/src/input.c
@@ -480,14 +480,21 @@ static int data_consume_data( struct stream_impl_data *ss, int length, location_
 	return consumed;
 }
 
-static int data_undo_consume_data( struct stream_impl_data *ss, const char *data, int length )
+static int data_undo_consume_data( struct stream_impl_data *si, const char *data, int length )
 {
-	struct run_buf *new_buf = new_run_buf( 0 );
-	new_buf->length = length;
-	memcpy( new_buf->data, data, length );
-	source_stream_data_prepend( ss, new_buf );
-	undo_position_data( ss, data, length );
-	ss->consumed -= length;
+	//printf( "data-undo-consume-data %p, undoing consume of %d bytes, consumed: %d\n", si, length, si->consumed );
+
+	if ( length > si->consumed )
+		length = si->consumed;
+
+	if ( length > 0 ) {
+		struct run_buf *new_buf = new_run_buf( 0 );
+		new_buf->length = length;
+		memcpy( new_buf->data, data, length );
+		source_stream_data_prepend( si, new_buf );
+		undo_position_data( si, data, length );
+		si->consumed -= length;
+	}
 
 	return length;
 }
@@ -547,6 +554,19 @@ void init_stream_impl_data( struct stream_impl_data *is, char *name )
 	is->level = COLM_INDENT_OFF;
 }
 
+static void input_stream_stash_head( struct stream_impl_seq *si, struct seq_buf *seq_buf )
+{
+	seq_buf->next = si->stash;
+	si->stash = seq_buf;
+}
+
+static struct seq_buf *input_stream_pop_stash( struct stream_impl_seq *si )
+{
+	struct seq_buf *seq_buf = si->stash;
+	si->stash = si->stash->next;
+	return seq_buf;
+}
+
 static struct seq_buf *input_stream_seq_pop_head( struct stream_impl_seq *is )
 {
 	struct seq_buf *ret = is->queue;
@@ -880,11 +900,7 @@ static int stream_consume_data( struct stream_impl_seq *is, int length, location
 		}
 
 		struct seq_buf *seq_buf = input_stream_seq_pop_head( is );
-		//if ( run_Buf->type == RUN_BUF_SOURCE_TYPE ) {
-		//	stream_t *stream = runBuf->stream;
-		//	colm_tree_downref( prg, sp, (tree_t*) stream );
-		//}
-		free( seq_buf );
+		input_stream_stash_head( is, seq_buf );
 	}
 
 	return consumed;
@@ -892,12 +908,19 @@ static int stream_consume_data( struct stream_impl_seq *is, int length, location
 
 static int stream_undo_consume_data( struct stream_impl_seq *is, const char *data, int length )
 {
-	//debug( REALM_INPUT, "undoing consume of %ld bytes\n", length );
+	//debug( REALM_INPUT, "stream %p, undoing consume of %ld bytes\n", is, length );
 
 	if ( is->consumed == 0 && is_source_stream( is ) ) {
 		struct stream_impl *si = is->queue->si;
-		int len = si->funcs->undo_consume_data( si, data, length );
-		return len;
+		int pushed_back = si->funcs->undo_consume_data( si, data, length );
+
+		if ( pushed_back < length ) {
+			struct seq_buf *b = input_stream_pop_stash( is );
+			input_stream_seq_prepend( is, b );
+			pushed_back += stream_undo_consume_data( is, data + pushed_back, length - pushed_back );
+		}
+
+		return pushed_back;
 	}
 	else {
 		struct seq_buf *new_buf = new_seq_buf( 0 );
-- 
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