Description: use memory-based circular buffer "stream" for the non-infinite
 scrollback state. This delays stream initialization so that the true size
 of the desired scrollback state can be discovered. This also means that
 changing the scrollback size in the middle of using a stream means you
 won't change the backend stream type.
Author: Kees Cook <kees@ubuntu.com>
Ubuntu-Bug: https://bugs.launchpad.net/ubuntu/+source/vte/+bug/778872

Index: vte-0.28.2/src/vtestream-mem.h
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ vte-0.28.2/src/vtestream-mem.h	2012-03-07 14:47:42.822382527 -0800
@@ -0,0 +1,321 @@
+/*
+ * Copyright (C) 2009,2010 Red Hat, Inc.
+ * Copyright (C) 2012 Kees Cook
+ *
+ * This is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Library General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * Red Hat Author(s): Behdad Esfahbod
+ * Ubuntu Authors(s): Kees Cook <kees@ubuntu.com>
+ */
+
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include <gio/gunixinputstream.h>
+
+/*
+ * VteMemStream: A memory-based stream
+ */
+
+struct mem_region {
+	gchar * region;
+	gsize allocated; /* How much memory exists in the region. */
+	gsize length; /* Current length of valid written data in the region. */
+	gsize seekpos; /* Where in the region we are positioned from seeking. */
+};
+
+typedef struct _VteMemStream {
+	VteStream parent;
+
+	/* The first is for the write head, second is for last page */
+	struct mem_region page[2];
+	gsize offset[2]; /* Offset into... ? */
+} VteMemStream;
+
+typedef VteStreamClass VteMemStreamClass;
+
+static GType _vte_mem_stream_get_type (void);
+#define VTE_TYPE_MEM_STREAM _vte_mem_stream_get_type ()
+
+G_DEFINE_TYPE (VteMemStream, _vte_mem_stream, VTE_TYPE_STREAM)
+
+static void
+_vte_mem_stream_init (VteMemStream *stream G_GNUC_UNUSED)
+{
+}
+
+VteStream *
+_vte_mem_stream_new (void)
+{
+	return (VteStream *) g_object_new (VTE_TYPE_MEM_STREAM, NULL);
+}
+
+static void
+_vte_mem_stream_finalize (GObject *object)
+{
+	VteMemStream *stream = (VteMemStream *) object;
+	gint i;
+
+	for (i = 0; i < 2; i ++) {
+		if (stream->page[i].region) g_free (stream->page[i].region);
+		memset(&stream->page[i], 0, sizeof (stream->page[i]));
+		stream->offset[i] = 0;
+	}
+
+	G_OBJECT_CLASS (_vte_mem_stream_parent_class)->finalize(object);
+}
+
+static gsize
+_mem_xseek (VteMemStream *stream, gint id, gsize pos, int whence)
+{
+	g_assert (id == 0 || id == 1);
+
+	switch (whence) {
+	case SEEK_SET:
+		if (pos > stream->page[id].length)
+			pos = stream->page[id].length;
+		stream->page[id].seekpos = pos;
+		break;
+	case SEEK_END:
+		stream->page[id].seekpos = stream->page[id].length;
+		break;
+	}
+	return stream->page[id].seekpos;
+}
+
+static gsize
+_mem_xread (VteMemStream *stream, gint id, char *data, gsize len)
+{
+	g_assert (id == 0 || id == 1);
+
+	if (G_UNLIKELY (len && !stream->page[id].region))
+		return 0;
+
+	if (len > stream->page[id].length - stream->page[id].seekpos)
+		len = stream->page[id].length - stream->page[id].seekpos;
+
+	g_memmove (data, stream->page[id].region + stream->page[id].seekpos, len);
+	stream->page[id].seekpos += len;
+
+	return len;
+}
+
+static void
+_mem_xwrite (VteMemStream *stream, gint id, const char *data, gsize len)
+{
+	g_assert (id == 0 || id == 1);
+
+	if (G_UNLIKELY (!stream->page[id].region))
+		return;
+
+	while (stream->page[id].seekpos + len > stream->page[id].allocated) {
+		gsize want = stream->page[id].allocated * 2;
+		stream->page[id].region = g_realloc (stream->page[id].region, want);
+		/* TODO: handle alloc failure. */
+		stream->page[id].allocated = want;
+	}
+
+	g_memmove (stream->page[id].region + stream->page[id].seekpos, data, len);
+	stream->page[id].seekpos += len;
+	if (stream->page[id].seekpos > stream->page[id].length)
+		stream->page[id].length = stream->page[id].seekpos;
+}
+
+static void
+_mem_xtruncate (VteMemStream *stream, gint id, gsize size)
+{
+	g_assert (id == 0 || id == 1);
+
+	if (G_UNLIKELY (!stream->page[id].region))
+		return;
+
+	/* This only expects the region to be reduced in size. */
+	g_assert (size <= stream->page[id].length);
+
+	stream->page[id].region = g_realloc(stream->page[id].region, size);
+	/* TODO: handle alloc failure. */
+	stream->page[id].length = stream->page[id].allocated = size;
+	if (stream->page[id].seekpos > size)
+		stream->page[id].seekpos = size;
+}
+
+static gboolean
+_mem_xwrite_contents (VteMemStream *stream, gint id, GOutputStream *output,
+		  GCancellable *cancellable, GError **error)
+{
+	gboolean ret;
+	gsize written;
+
+	g_assert (id == 0 || id == 1);
+
+	if (G_UNLIKELY (!stream->page[id].region))
+		return TRUE;
+
+	ret = g_output_stream_write_all (output,
+					 stream->page[id].region + stream->page[id].seekpos,
+					 stream->page[id].length - stream->page[id].seekpos,
+					 &written, cancellable, error);
+	stream->page[id].seekpos = stream->page[id].length;
+
+	return ret;
+}
+
+static void
+_vte_mem_stream_reset (VteStream *astream, gsize offset)
+{
+	VteMemStream *stream = (VteMemStream *) astream;
+
+	if (stream->page[0].region) _mem_xtruncate (stream, 0, 0);
+	if (stream->page[1].region) _mem_xtruncate (stream, 1, 0);
+
+	stream->offset[0] = stream->offset[1] = offset;
+}
+
+static inline void
+_vte_mem_stream_ensure_region0 (VteMemStream *stream)
+{
+	if (G_LIKELY (stream->page[0].region))
+		return;
+
+	stream->page[0].allocated = 4096;	/* Arbitrary initial size. */
+	stream->page[0].region = g_malloc(stream->page[0].allocated);
+	/* TODO: how to handle malloc failure? */
+}
+
+static gsize
+_vte_mem_stream_append (VteStream *astream, const char *data, gsize len)
+{
+	VteMemStream *stream = (VteMemStream *) astream;
+	gsize ret;
+
+	_vte_mem_stream_ensure_region0 (stream);
+
+	ret = _mem_xseek (stream, 0, 0, SEEK_END);
+	_mem_xwrite (stream, 0, data, len);
+
+	return stream->offset[0] + ret;
+}
+
+static gboolean
+_vte_mem_stream_read (VteStream *astream, gsize offset, char *data, gsize len)
+{
+	VteMemStream *stream = (VteMemStream *) astream;
+	gsize l;
+
+	if (G_UNLIKELY (offset < stream->offset[1]))
+		return FALSE;
+
+	if (offset < stream->offset[0]) {
+		_mem_xseek (stream, 1, offset - stream->offset[1], SEEK_SET);
+		l = _mem_xread (stream, 1, data, len);
+		offset += l; data += l; len -= l; if (!len) return TRUE;
+	}
+
+	_mem_xseek (stream, 0, offset - stream->offset[0], SEEK_SET);
+	l = _mem_xread (stream, 0, data, len);
+	offset += l; data += l; len -= l; if (!len) return TRUE;
+
+	return FALSE;
+}
+
+static void
+_vte_mem_stream_swap_regions (VteMemStream *stream)
+{
+	struct mem_region temp;
+
+	temp = stream->page[0];
+	stream->page[0] = stream->page[1];
+	stream->page[1] = temp;
+}
+
+static void
+_vte_mem_stream_truncate (VteStream *astream, gsize offset)
+{
+	VteMemStream *stream = (VteMemStream *) astream;
+
+	if (G_UNLIKELY (offset < stream->offset[1])) {
+		_mem_xtruncate (stream, 1, 0);
+		stream->offset[1] = offset;
+	}
+
+	if (G_UNLIKELY (offset < stream->offset[0])) {
+		_mem_xtruncate (stream, 0, 0);
+		stream->offset[0] = stream->offset[1];
+		_vte_mem_stream_swap_regions (stream);
+	} else {
+		_mem_xtruncate (stream, 0, offset - stream->offset[0]);
+	}
+}
+
+static void
+_vte_mem_stream_new_page (VteStream *astream)
+{
+	VteMemStream *stream = (VteMemStream *) astream;
+
+	stream->offset[1] = stream->offset[0];
+	if (stream->page[0].region)
+		stream->offset[0] += _mem_xseek (stream, 0, 0, SEEK_END);
+	_vte_mem_stream_swap_regions (stream);
+	_mem_xtruncate (stream, 0, 0);
+}
+
+static gsize
+_vte_mem_stream_head (VteStream *astream)
+{
+	VteMemStream *stream = (VteMemStream *) astream;
+
+	if (stream->page[0].region)
+		return stream->offset[0] + _mem_xseek (stream, 0, 0, SEEK_END);
+	else
+		return stream->offset[0];
+}
+
+static gboolean
+_vte_mem_stream_write_contents (VteStream *astream, GOutputStream *output,
+				 gsize offset,
+				 GCancellable *cancellable, GError **error)
+{
+	VteMemStream *stream = (VteMemStream *) astream;
+
+	if (G_UNLIKELY (offset < stream->offset[1]))
+		return FALSE;
+
+	if (offset < stream->offset[0]) {
+		_mem_xseek (stream, 1, offset - stream->offset[1], SEEK_SET);
+		if (!_mem_xwrite_contents (stream, 1, output, cancellable, error))
+			return FALSE;
+		offset = stream->offset[0];
+	}
+
+	_mem_xseek (stream, 0, offset - stream->offset[0], SEEK_SET);
+	return _mem_xwrite_contents (stream, 0, output, cancellable, error);
+}
+
+static void
+_vte_mem_stream_class_init (VteMemStreamClass *klass)
+{
+	GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
+
+	gobject_class->finalize = _vte_mem_stream_finalize;
+
+	klass->reset = _vte_mem_stream_reset;
+	klass->append = _vte_mem_stream_append;
+	klass->read = _vte_mem_stream_read;
+	klass->truncate = _vte_mem_stream_truncate;
+	klass->new_page = _vte_mem_stream_new_page;
+	klass->head = _vte_mem_stream_head;
+	klass->write_contents = _vte_mem_stream_write_contents;
+}
Index: vte-0.28.2/src/vtestream.h
===================================================================
--- vte-0.28.2.orig/src/vtestream.h	2012-03-07 10:23:14.998517196 -0800
+++ vte-0.28.2/src/vtestream.h	2012-03-07 10:23:52.055018606 -0800
@@ -43,6 +43,8 @@
 
 VteStream *
 _vte_file_stream_new (void);
+VteStream *
+_vte_mem_stream_new (void);
 
 G_END_DECLS
 
Index: vte-0.28.2/src/ring.c
===================================================================
--- vte-0.28.2.orig/src/ring.c	2012-03-07 11:17:05.896949593 -0800
+++ vte-0.28.2/src/ring.c	2012-03-07 14:42:35.626333589 -0800
@@ -49,6 +49,25 @@
 #define _vte_ring_validate(ring) G_STMT_START {} G_STMT_END
 #endif
 
+static void
+_vte_ring_ensure_stream (VteRing *ring)
+{
+	if (G_LIKELY(ring->attr_stream))
+		return;
+
+	if (ring->max >= G_MAXLONG) {
+		/* "Infinite" scroll-back buffer limit, file-backed. */
+		ring->attr_stream = _vte_file_stream_new ();
+		ring->text_stream = _vte_file_stream_new ();
+		ring->row_stream = _vte_file_stream_new ();
+	} else {
+		/* Predefined scroll-back buffer limit, memory-backed. */
+		ring->attr_stream = _vte_mem_stream_new ();
+		ring->text_stream = _vte_mem_stream_new ();
+		ring->row_stream = _vte_mem_stream_new ();
+	}
+}
+
 
 void
 _vte_ring_init (VteRing *ring, gulong max_rows)
@@ -62,10 +81,6 @@
 	ring->mask = 31;
 	ring->array = g_malloc0 (sizeof (ring->array[0]) * (ring->mask + 1));
 
-	ring->attr_stream = _vte_file_stream_new ();
-	ring->text_stream = _vte_file_stream_new ();
-	ring->row_stream = _vte_file_stream_new ();
-
 	ring->last_attr.text_offset = 0;
 	ring->last_attr.attr.i = basic_cell.i.attr;
 	ring->utf8_buffer = g_string_sized_new (128);
@@ -81,6 +96,8 @@
 {
 	gulong i;
 
+	_vte_ring_ensure_stream (ring);
+
 	for (i = 0; i <= ring->mask; i++)
 		_vte_row_data_fini (&ring->array[i]);
 
@@ -103,12 +120,14 @@
 static gboolean
 _vte_ring_read_row_record (VteRing *ring, VteRowRecord *record, gulong position)
 {
+	_vte_ring_ensure_stream (ring);
 	return _vte_stream_read (ring->row_stream, position * sizeof (*record), (char *) record, sizeof (*record));
 }
 
 static void
 _vte_ring_append_row_record (VteRing *ring, const VteRowRecord *record, gulong position)
 {
+	_vte_ring_ensure_stream (ring);
 	_vte_stream_append (ring->row_stream, (const char *) record, sizeof (*record));
 }
 
@@ -121,6 +140,7 @@
 	int i;
 
 	_vte_debug_print (VTE_DEBUG_RING, "Freezing row %lu.\n", position);
+	_vte_ring_ensure_stream (ring);
 
 	record.text_offset = _vte_stream_head (ring->text_stream);
 	record.attr_offset = _vte_stream_head (ring->attr_stream);
@@ -183,6 +203,7 @@
 	GString *buffer = ring->utf8_buffer;
 
 	_vte_debug_print (VTE_DEBUG_RING, "Thawing row %lu.\n", position);
+	_vte_ring_ensure_stream (ring);
 
 	_vte_row_data_clear (row);
 
@@ -266,6 +287,7 @@
 _vte_ring_reset_streams (VteRing *ring, gulong position)
 {
 	_vte_debug_print (VTE_DEBUG_RING, "Reseting streams to %lu.\n", position);
+	_vte_ring_ensure_stream (ring);
 
 	_vte_stream_reset (ring->row_stream, position * sizeof (VteRowRecord));
 	_vte_stream_reset (ring->text_stream, 0);
@@ -281,6 +303,7 @@
 _vte_ring_new_page (VteRing *ring)
 {
 	_vte_debug_print (VTE_DEBUG_RING, "Starting new stream page at %lu.\n", ring->writable);
+	_vte_ring_ensure_stream (ring);
 
 	_vte_stream_new_page (ring->attr_stream);
 	_vte_stream_new_page (ring->text_stream);
@@ -608,6 +631,7 @@
 	gulong i;
 
 	_vte_debug_print(VTE_DEBUG_RING, "Writing contents to GOutputStream.\n");
+	_vte_ring_ensure_stream (ring);
 
 	if (ring->start < ring->writable) {
 		VteRowRecord record;
Index: vte-0.28.2/src/vtestream.c
===================================================================
--- vte-0.28.2.orig/src/vtestream.c	2012-03-07 11:41:24.427419860 -0800
+++ vte-0.28.2/src/vtestream.c	2012-03-07 12:55:14.227826250 -0800
@@ -31,3 +31,4 @@
 
 #include "vtestream-base.h"
 #include "vtestream-file.h"
+#include "vtestream-mem.h"
Index: vte-0.28.2/src/Makefile.am
===================================================================
--- vte-0.28.2.orig/src/Makefile.am	2012-03-07 12:55:40.912155853 -0800
+++ vte-0.28.2/src/Makefile.am	2012-03-07 12:55:49.460261440 -0800
@@ -80,6 +80,7 @@
 	vtestream.h \
 	vtestream-base.h \
 	vtestream-file.h \
+	vtestream-mem.h \
 	vtetc.c \
 	vtetc.h \
 	vtetree.c \