Swfdec - Apr 2007 - Branch 'as' - 17 commits - libswfdec/jpeg libswfdec/swfdec_bits.c libswfdec/swfdec_font.c libswfdec/swfdec_image.c libswfdec/swfdec_root_sprite.c libswfdec/swfdec_script.c libswfdec/swfdec_shape.c libswfdec/swfdec_sound.c libswfdec/swfdec_sprite.c

libswfdec/jpeg/jpeg.c          |    3 +++
 libswfdec/swfdec_bits.c        |   18 ++++++++++++++++--
 libswfdec/swfdec_font.c        |   30 ++++++++++++++++++++++++------
 libswfdec/swfdec_image.c       |   30 ++++++++++++++----------------
 libswfdec/swfdec_root_sprite.c |    2 +-
 libswfdec/swfdec_script.c      |   18 +++++++++---------
 libswfdec/swfdec_shape.c       |   11 ++++++-----
 libswfdec/swfdec_sound.c       |    1 +
 libswfdec/swfdec_sprite.c      |    6 ++++--
 9 files changed, 78 insertions(+), 41 deletions(-)

New commits:
diff-tree b78d0a0bd570f5151cdc08c30ace2d64ce4a3b57 (from parents)
Merge: 41ef9b2eaa4823a91cc4387606066d64d054ad61
ce83f3171f4400aa620464982ab266d567213be5
Author: Benjamin Otte <otte@gnome.org>
Date:   Tue Apr 17 13:42:13 2007 +0200

    Merge branch 'master' into as
    
    Conflicts:
    
    	libswfdec/swfdec_edittext.c
    	libswfdec/swfdec_script.c

diff-tree ce83f3171f4400aa620464982ab266d567213be5 (from
de1a29a1b62e30df5cb4a26fe192efd44db98bec)
Author: Benjamin Otte <otte@gnome.org>
Date:   Tue Apr 17 13:38:24 2007 +0200

    return if no data is available

diff --git a/libswfdec/swfdec_sound.c b/libswfdec/swfdec_sound.c
index 1087f5f..dadd400 100644
--- a/libswfdec/swfdec_sound.c
+++ b/libswfdec/swfdec_sound.c
@@ -98,6 +98,7 @@ tag_func_sound_stream_block (SwfdecSwfDe
     SWFDEC_DEBUG ("empty sound block n_samples=%d skip=%d",
n_samples,
         skip);
     chunk = NULL;
+    return SWFDEC_STATUS_OK;
   } else {
     chunk = swfdec_bits_get_buffer (&s->b, -1);
     if (chunk == NULL) {
diff-tree de1a29a1b62e30df5cb4a26fe192efd44db98bec (from
4ecf6f08ab585cbf8089373cb6535d5e3e3493fc)
Author: Benjamin Otte <otte@gnome.org>
Date:   Tue Apr 17 13:13:48 2007 +0200

    break the ExportAssets loop if no more bytes are available

diff --git a/libswfdec/swfdec_root_sprite.c b/libswfdec/swfdec_root_sprite.c
index 7159927..41e8b31 100644
--- a/libswfdec/swfdec_root_sprite.c
+++ b/libswfdec/swfdec_root_sprite.c
@@ -117,7 +117,7 @@ tag_func_export_assets (SwfdecSwfDecoder
 
   count = swfdec_bits_get_u16 (bits);
   SWFDEC_LOG ("exporting %u assets", count);
-  for (i = 0; i < count; i++) {
+  for (i = 0; i < count && swfdec_bits_left (bits); i++) {
     guint id;
     SwfdecCharacter *object;
     char *name;
diff-tree 4ecf6f08ab585cbf8089373cb6535d5e3e3493fc (from
09b659302736f9b00db64a1586703de7fe8f7344)
Author: Benjamin Otte <otte@gnome.org>
Date:   Tue Apr 17 12:40:39 2007 +0200

    break out of loop if no more bits are available
    
    this avoids long erroneous loops when the number of styles in
    the file has been corrupted

diff --git a/libswfdec/swfdec_shape.c b/libswfdec/swfdec_shape.c
index 3aa5053..ac2491e 100644
--- a/libswfdec/swfdec_shape.c
+++ b/libswfdec/swfdec_shape.c
@@ -329,7 +329,7 @@ swfdec_shape_add_styles (SwfdecSwfDecode
     n_fill_styles = swfdec_bits_get_u16 (bits);
   }
   SWFDEC_LOG ("   n_fill_styles %d", n_fill_styles);
-  for (i = 0; i < n_fill_styles; i++) {
+  for (i = 0; i < n_fill_styles && swfdec_bits_left (bits); i++) {
     SwfdecPattern *pattern;
 
     SWFDEC_LOG ("   fill style %d:", i);
@@ -344,7 +344,7 @@ swfdec_shape_add_styles (SwfdecSwfDecode
     n_line_styles = swfdec_bits_get_u16 (bits);
   }
   SWFDEC_LOG ("   n_line_styles %d", n_line_styles);
-  for (i = 0; i < n_line_styles; i++) {
+  for (i = 0; i < n_line_styles && swfdec_bits_left (bits); i++) {
     g_ptr_array_add (shape->lines, parse_stroke (s));
   }
 
diff-tree 09b659302736f9b00db64a1586703de7fe8f7344 (from
b498ba186ab9d587cc087ae9ab5952f1d5b2865a)
Author: Benjamin Otte <otte@gnome.org>
Date:   Tue Apr 17 12:36:33 2007 +0200

    it's not this code's job to syncbits

diff --git a/libswfdec/swfdec_shape.c b/libswfdec/swfdec_shape.c
index a81b389..3aa5053 100644
--- a/libswfdec/swfdec_shape.c
+++ b/libswfdec/swfdec_shape.c
@@ -338,7 +338,6 @@ swfdec_shape_add_styles (SwfdecSwfDecode
     g_ptr_array_add (shape->fills, pattern);
   }
 
-  swfdec_bits_syncbits (bits);
   shape->lines_offset = shape->lines->len;
   n_line_styles = swfdec_bits_get_u8 (bits);
   if (n_line_styles == 0xff) {
@@ -349,7 +348,6 @@ swfdec_shape_add_styles (SwfdecSwfDecode
     g_ptr_array_add (shape->lines, parse_stroke (s));
   }
 
-  swfdec_bits_syncbits (bits);
   shape->n_fill_bits = swfdec_bits_getbits (bits, 4);
   shape->n_line_bits = swfdec_bits_getbits (bits, 4);
 }
diff-tree b498ba186ab9d587cc087ae9ab5952f1d5b2865a (from
45c89c3d902be858a304539165d1160e822fba52)
Author: Benjamin Otte <otte@gnome.org>
Date:   Tue Apr 17 12:19:27 2007 +0200

    avoid overflow issues when bytes is near MAXUINT

diff --git a/libswfdec/swfdec_bits.c b/libswfdec/swfdec_bits.c
index 8eef225..0f7e4c9 100644
--- a/libswfdec/swfdec_bits.c
+++ b/libswfdec/swfdec_bits.c
@@ -95,7 +95,9 @@ swfdec_bits_init_bits (SwfdecBits *bits,
 
   bits->buffer = from->buffer;
   bits->ptr = from->ptr;
-  bits->end = MIN (bits->ptr + bytes, from->end);
+  if (bytes > (guint) (from->end - from->ptr))
+    bytes = from->end - from->ptr;
+  bits->end = bits->ptr + bytes;
   bits->idx = 0;
   from->ptr = bits->end;
 }
diff-tree 45c89c3d902be858a304539165d1160e822fba52 (from
36a3f8c38831112cb93caeb3fdf5ab3214fbb859)
Author: Benjamin Otte <otte@gnome.org>
Date:   Tue Apr 17 12:12:11 2007 +0200

    movies without a rate don't have sound

diff --git a/libswfdec/swfdec_sprite.c b/libswfdec/swfdec_sprite.c
index f3ad17d..19c1442 100644
--- a/libswfdec/swfdec_sprite.c
+++ b/libswfdec/swfdec_sprite.c
@@ -562,8 +562,10 @@ swfdec_sprite_set_n_frames (SwfdecSprite
   sprite->frames = g_new0 (SwfdecSpriteFrame, n_frames);
   sprite->n_frames = n_frames;
 
-  for (i = 0; i < n_frames; i++) {
-    sprite->frames[i].sound_samples = 44100 * 256 / rate;
+  if (rate > 0) {
+    for (i = 0; i < n_frames; i++) {
+      sprite->frames[i].sound_samples = 44100 * 256 / rate;
+    }
   }
 
   SWFDEC_LOG ("n_frames = %d", sprite->n_frames);
diff-tree 36a3f8c38831112cb93caeb3fdf5ab3214fbb859 (from
79da14950862c8c92669a9091edf0daf33792588)
Author: Benjamin Otte <otte@gnome.org>
Date:   Tue Apr 17 12:11:48 2007 +0200

    only convert variable names if they exist

diff --git a/libswfdec/swfdec_edittext.c b/libswfdec/swfdec_edittext.c
index 151feb2..e89c8f5 100644
--- a/libswfdec/swfdec_edittext.c
+++ b/libswfdec/swfdec_edittext.c
@@ -76,7 +76,8 @@ swfdec_edit_text_parse_variable (SwfdecE
     return;
   }
   /* FIXME: check the variable for valid identifiers */
-  if (strchr (text->variable, '/')) {
+  if (text->variable &&
+      strchr (text->variable, '/')) {
     char *ret = swfdec_js_slash_to_dot (text->variable);
     g_free (text->variable);
     text->variable = ret;
diff-tree 79da14950862c8c92669a9091edf0daf33792588 (from
3f4fa05395690c80c19ead02027ee4beb71f9f2d)
Author: Benjamin Otte <otte@gnome.org>
Date:   Tue Apr 17 12:07:49 2007 +0200

    Fix various failures to sanely read buffers

diff --git a/libswfdec/swfdec_image.c b/libswfdec/swfdec_image.c
index 612b52b..6d15e27 100644
--- a/libswfdec/swfdec_image.c
+++ b/libswfdec/swfdec_image.c
@@ -122,9 +122,7 @@ tag_func_define_bits_jpeg (SwfdecSwfDeco
   } else {
     image->jpegtables = swfdec_buffer_ref (s->jpegtables);
   }
-  image->raw_data = swfdec_buffer_ref (bits->buffer);
-
-  bits->ptr += bits->buffer->length - 2;
+  image->raw_data = swfdec_bits_get_buffer (bits, -1);
 
   return SWFDEC_STATUS_OK;
 }
@@ -146,14 +144,14 @@ swfdec_image_jpeg_load (SwfdecImage *ima
     jpeg_decoder_addbits (dec, image->jpegtables->data,
         image->jpegtables->length);
   }
-  if (image->raw_data->data[2] != 0xff || image->raw_data->data[3]
!= 0xd8) {
+  if (image->raw_data->data[0] != 0xff || image->raw_data->data[1]
!= 0xd8) {
     SWFDEC_ERROR("not jpeg %02x %02x",
-        image->raw_data->data[2], image->raw_data->data[3]);
+        image->raw_data->data[0], image->raw_data->data[1]);
     jpeg_decoder_free (dec);
     return;
   }
-  jpeg_decoder_addbits (dec, image->raw_data->data + 2,
-      image->raw_data->length - 2);
+  jpeg_decoder_addbits (dec, image->raw_data->data,
+      image->raw_data->length);
   jpeg_decoder_parse (dec);
   jpeg_decoder_get_image_size (dec, &image->width,
&image->height);
   if (image->width == 0 || image->height == 0) {
@@ -184,9 +182,7 @@ tag_func_define_bits_jpeg_2 (SwfdecSwfDe
     return SWFDEC_STATUS_OK;
 
   image->type = SWFDEC_IMAGE_TYPE_JPEG2;
-  image->raw_data = swfdec_buffer_ref (bits->buffer);
-
-  bits->ptr += bits->buffer->length - 2;
+  image->raw_data = swfdec_bits_get_buffer (bits, -1);
 
   return SWFDEC_STATUS_OK;
 }
@@ -198,14 +194,14 @@ swfdec_image_jpeg2_load (SwfdecImage *im
 
   dec = jpeg_decoder_new ();
 
-  if (image->raw_data->data[2] != 0xff || image->raw_data->data[3]
!= 0xd8) {
+  if (image->raw_data->data[0] != 0xff || image->raw_data->data[1]
!= 0xd8) {
     SWFDEC_ERROR("not jpeg %02x %02x",
-        image->raw_data->data[2], image->raw_data->data[3]);
+        image->raw_data->data[0], image->raw_data->data[1]);
     jpeg_decoder_free (dec);
     return;
   }
-  jpeg_decoder_addbits (dec, image->raw_data->data + 2,
-      image->raw_data->length - 2);
+  jpeg_decoder_addbits (dec, image->raw_data->data,
+      image->raw_data->length);
   jpeg_decoder_parse (dec);
   jpeg_decoder_get_image_size (dec, &image->width,
&image->height);
   if (image->width == 0 || image->height == 0) {
@@ -539,6 +535,9 @@ swfdec_image_colormap_decode (SwfdecImag
 static gboolean
 swfdec_image_ensure_loaded (SwfdecImage *image)
 {
+  if (image->raw_data == NULL)
+    return FALSE;
+
   if (image->data == NULL) {
     switch (image->type) {
       case SWFDEC_IMAGE_TYPE_JPEG:
diff-tree 3f4fa05395690c80c19ead02027ee4beb71f9f2d (from
d7461508e0d76b7eaa89cc67427f8415884d29f7)
Author: Benjamin Otte <otte@gnome.org>
Date:   Tue Apr 17 12:07:21 2007 +0200

    handle morph shape offset sanely

diff --git a/libswfdec/swfdec_shape.c b/libswfdec/swfdec_shape.c
index 3792582..a81b389 100644
--- a/libswfdec/swfdec_shape.c
+++ b/libswfdec/swfdec_shape.c
@@ -1038,7 +1038,10 @@ tag_define_morph_shape (SwfdecSwfDecoder
   swfdec_bits_get_rect (bits, &morph->end_extents);
   offset = swfdec_bits_get_u32 (bits);
   end_bits = *bits;
-  end_bits.ptr += offset;
+  if (swfdec_bits_skip_bytes (&end_bits, offset) != offset) {
+    SWFDEC_ERROR ("wrong offset in DefineMorphShape");
+    return SWFDEC_STATUS_OK;
+  }
   bits->end = end_bits.ptr;
 
   swfdec_shape_add_styles (s, SWFDEC_SHAPE (morph),
diff-tree d7461508e0d76b7eaa89cc67427f8415884d29f7 (from
42e6df0df9df1b028752c6afe2632008e3378bdc)
Author: Benjamin Otte <otte@gnome.org>
Date:   Tue Apr 17 11:46:17 2007 +0200

    sanely skip offsets in DefineFont2

diff --git a/libswfdec/swfdec_font.c b/libswfdec/swfdec_font.c
index c626104..c0562b1 100644
--- a/libswfdec/swfdec_font.c
+++ b/libswfdec/swfdec_font.c
@@ -289,6 +289,7 @@ tag_func_define_font_2 (SwfdecSwfDecoder
   int font_descent;
   int font_leading;
   int i;
+  guint skip;
 
   id = swfdec_bits_get_u16 (bits);
   font = swfdec_swf_decoder_create_character (s, id, SWFDEC_TYPE_FONT);
@@ -318,10 +319,18 @@ tag_func_define_font_2 (SwfdecSwfDecoder
 
   n_glyphs = swfdec_bits_get_u16 (bits);
   if (wide_offsets) {
-    bits->ptr += 4 * n_glyphs;
+    skip = 4 * n_glyphs;
+    if (swfdec_bits_skip_bytes (bits, skip) != skip) {
+      SWFDEC_ERROR ("could not skip %u bytes", skip);
+      return SWFDEC_STATUS_OK;
+    }
     code_table_offset = swfdec_bits_get_u32 (bits);
   } else {
-    bits->ptr += 2 * n_glyphs;
+    skip = 2 * n_glyphs;
+    if (swfdec_bits_skip_bytes (bits, skip) != skip) {
+      SWFDEC_ERROR ("could not skip %u bytes", skip);
+      return SWFDEC_STATUS_OK;
+    }
     code_table_offset = swfdec_bits_get_u16 (bits);
   }
 
diff-tree 42e6df0df9df1b028752c6afe2632008e3378bdc (from
f8d83577ae0fca8a750b0ff309faaf205cbe87cc)
Author: Benjamin Otte <otte@gnome.org>
Date:   Tue Apr 17 11:35:50 2007 +0200

    fix swfcdec_script_new to not touch the SwfdecBits struct directly

diff --git a/libswfdec/swfdec_script.c b/libswfdec/swfdec_script.c
index 5163ce7..d675207 100644
--- a/libswfdec/swfdec_script.c
+++ b/libswfdec/swfdec_script.c
@@ -2731,7 +2731,8 @@ SwfdecScript *
 swfdec_script_new (SwfdecBits *bits, const char *name, guint version)
 {
   SwfdecScript *script;
-  const guchar *start;
+  SwfdecBits org;
+  guint len;
   
   g_return_val_if_fail (bits != NULL, NULL);
 
@@ -2740,8 +2741,8 @@ swfdec_script_new (SwfdecBits *bits, con
     return NULL;
   }
 
-  swfdec_bits_syncbits (bits);
-  start = bits->ptr;
+  org = *bits;
+  len = swfdec_bits_left (bits) / 8;
   script = g_new0 (SwfdecScript, 1);
   script->refcount = 1;
   script->name = g_strdup (name ? name : "Unnamed script");
@@ -2750,15 +2751,12 @@ swfdec_script_new (SwfdecBits *bits, con
    * DefineFunction and friends override this */
   script->flags = SWFDEC_SCRIPT_SUPPRESS_ARGS;
 
-  if (!swfdec_script_foreach_internal (bits, validate_action, script)) {
-    /* assign a random buffer here so we have something to unref */
-    script->buffer = bits->buffer;
-    swfdec_buffer_ref (script->buffer);
+  if (!swfdec_script_foreach_internal (bits, validate_action, script) ||
+      (len -= swfdec_bits_left (bits) / 8) == 0) {
     swfdec_script_unref (script);
     return NULL;
   }
-  script->buffer = swfdec_buffer_new_subbuffer (bits->buffer, start -
bits->buffer->data,
-      bits->ptr - start);
+  script->buffer = swfdec_bits_get_buffer (&org, len);
   return script;
 }
 
@@ -2785,7 +2783,8 @@ swfdec_script_unref (SwfdecScript *scrip
   if (script->refcount > 0)
     return;
 
-  swfdec_buffer_unref (script->buffer);
+  if (script->buffer)
+    swfdec_buffer_unref (script->buffer);
   if (script->constant_pool)
     swfdec_buffer_unref (script->constant_pool);
   g_free (script->name);
diff-tree f8d83577ae0fca8a750b0ff309faaf205cbe87cc (from
0fecc667a7f73138a1e16b12a0c9c7f4081d369c)
Author: Benjamin Otte <otte@gnome.org>
Date:   Tue Apr 17 11:35:21 2007 +0200

    handle 0 bytes of input gracefully

diff --git a/libswfdec/jpeg/jpeg.c b/libswfdec/jpeg/jpeg.c
index 216d8a5..228a4d8 100644
--- a/libswfdec/jpeg/jpeg.c
+++ b/libswfdec/jpeg/jpeg.c
@@ -780,6 +780,9 @@ jpeg_decoder_addbits (JpegDecoder * dec,
 {
   unsigned int offset;
 
+  if (len == 0)
+    return 0;
+
 #if 0
   {
     static int index = 0;
diff-tree 0fecc667a7f73138a1e16b12a0c9c7f4081d369c (from
56fd58406827a35ff524eb9340d07602e819e6f2)
Author: Benjamin Otte <otte@gnome.org>
Date:   Tue Apr 17 11:34:56 2007 +0200

    clarify beahviour of swfdec_bits_get_buffer

diff --git a/libswfdec/swfdec_bits.c b/libswfdec/swfdec_bits.c
index 11df1ba..8eef225 100644
--- a/libswfdec/swfdec_bits.c
+++ b/libswfdec/swfdec_bits.c
@@ -646,7 +646,8 @@ swfdec_bits_get_rect (SwfdecBits * bits,
  * @len: length of buffer or -1 for maximum
  *
  * Gets the contents of the next @len bytes of @bits and buts them in a new
- * subbuffer.
+ * subbuffer. If @len is 0 (or @len is -1 and no more data is available), this
+ * is considered a reading error and %NULL is returned.
  *
  * Returns: the new #SwfdecBuffer or NULL if the requested amount of data 
  *          isn't available
diff-tree 56fd58406827a35ff524eb9340d07602e819e6f2 (from
a490ca007d4158f6989c3b9d858e8703a0c69fbf)
Author: Benjamin Otte <otte@gnome.org>
Date:   Tue Apr 17 11:12:46 2007 +0200

    read font names sanely

diff --git a/libswfdec/swfdec_font.c b/libswfdec/swfdec_font.c
index 0aca1d5..c626104 100644
--- a/libswfdec/swfdec_font.c
+++ b/libswfdec/swfdec_font.c
@@ -93,6 +93,7 @@ swfdec_font_get_glyph (SwfdecFont * font
   return g_array_index (font->glyphs, SwfdecFontEntry, glyph).shape;
 }
 
+#if 0
 static char *
 convert_from_language (const char *s, SwfdecLanguage language)
 {
@@ -120,6 +121,7 @@ convert_from_language (const char *s, Sw
     SWFDEC_ERROR ("given text is not in language %s", langcode);
   return ret;
 }
+#endif
 
 int
 tag_func_define_font_info (SwfdecSwfDecoder *s, guint version)
@@ -158,7 +160,6 @@ tag_func_define_font_info (SwfdecSwfDeco
   wide = swfdec_bits_getbit (&s->b);
   if (version > 1)
     language = swfdec_bits_get_u8 (&s->b);
-  font->name = convert_from_language (name, language);
   g_free (name);
   if (font->name) {
     SWFDEC_LOG ("Creating font description for font %d", id);
@@ -308,8 +309,12 @@ tag_func_define_font_2 (SwfdecSwfDecoder
   SWFDEC_DEBUG("langcode %d", langcode);
 
   font_name_len = swfdec_bits_get_u8 (bits);
-  //font_name = 
-  bits->ptr += font_name_len;
+  font->name = swfdec_bits_get_string_length (bits, font_name_len);
+  if (font->name == NULL) {
+    SWFDEC_ERROR ("error reading font name");
+  } else {
+    SWFDEC_LOG ("  font name = %s", font->name);
+  }
 
   n_glyphs = swfdec_bits_get_u16 (bits);
   if (wide_offsets) {
@@ -397,7 +402,11 @@ tag_func_define_font_3 (SwfdecSwfDecoder
   SWFDEC_LOG (" language = %u", (guint) language);
   len = swfdec_bits_get_u8 (&s->b);
   font->name = swfdec_bits_get_string_length (&s->b, len);
-  SWFDEC_LOG (" name = %s", font->name);
+  if (font->name == NULL) {
+    SWFDEC_ERROR ("error reading font name");
+  } else {
+    SWFDEC_LOG ("  font name = %s", font->name);
+  }
   n_glyphs = swfdec_bits_get_u16 (&s->b);
   SWFDEC_LOG (" n_glyphs = %u", n_glyphs);
   
diff-tree a490ca007d4158f6989c3b9d858e8703a0c69fbf (from
26c7b2f2b16edc2c7f9f044deee8fbc06743fee7)
Author: Benjamin Otte <otte@gnome.org>
Date:   Tue Apr 17 11:12:34 2007 +0200

    use swfdec_bits_get_buffer instead of manually fuzzing with the SwfdecBits
structure

diff --git a/libswfdec/swfdec_image.c b/libswfdec/swfdec_image.c
index 69a3f17..612b52b 100644
--- a/libswfdec/swfdec_image.c
+++ b/libswfdec/swfdec_image.c
@@ -96,8 +96,7 @@ swfdec_image_jpegtables (SwfdecSwfDecode
 
   SWFDEC_DEBUG ("swfdec_image_jpegtables");
 
-  s->jpegtables = swfdec_buffer_ref (bits->buffer);
-  bits->ptr += bits->buffer->length;
+  s->jpegtables = swfdec_bits_get_buffer (bits, -1);
 
   return SWFDEC_STATUS_OK;
 }
diff-tree 26c7b2f2b16edc2c7f9f044deee8fbc06743fee7 (from
04113e5a83386f59140f248a817f7bf8d6728ddb)
Author: Benjamin Otte <otte@gnome.org>
Date:   Tue Apr 17 11:00:41 2007 +0200

    make swfdec_bits_get_string_length read 0-byte strings

diff --git a/libswfdec/swfdec_bits.c b/libswfdec/swfdec_bits.c
index 6e25cf7..11df1ba 100644
--- a/libswfdec/swfdec_bits.c
+++ b/libswfdec/swfdec_bits.c
@@ -521,11 +521,22 @@ swfdec_bits_skip_bytes (SwfdecBits *bits
   return n_bytes;
 }
 
+/**
+ * swfdec_bits_get_string_length:
+ * @bits: a #SwfdecBits
+ * @len: number of bytes to read
+ *
+ * Reads the next @len bytes into a string and validates it as UTF-8.
+ *
+ * Returns: a new string or %NULL on error
+ **/
 char *
 swfdec_bits_get_string_length (SwfdecBits * bits, guint len)
 {
   char *ret;
 
+  if (len == 0)
+    return g_strdup ("");
   SWFDEC_BYTES_CHECK (bits, len);
 
   ret = g_strndup ((char *) bits->ptr, len);