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[glyf] Move GlyphHeader size checking to a static method

This commit is contained in:
Ebrahim Byagowi 2019-08-25 00:36:58 +04:30
parent 139d14dc89
commit 07e467a30e
1 changed files with 36 additions and 33 deletions
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69
src/hb-ot-glyf-table.hh
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@ -230,7 +230,7 @@ struct glyf
static void static void
_zero_instruction_length (hb_bytes_t glyph) _zero_instruction_length (hb_bytes_t glyph)
{ {
const GlyphHeader &glyph_header = StructAtOffset<GlyphHeader> (&glyph, 0); auto &glyph_header = GlyphHeader::from_bytes (glyph);
if (!glyph_header.is_simple_glyph ()) return; // only for simple glyphs if (!glyph_header.is_simple_glyph ()) return; // only for simple glyphs
unsigned int instruction_len_offset = glyph_header.simple_instruction_len_offset (); unsigned int instruction_len_offset = glyph_header.simple_instruction_len_offset ();
@ -241,7 +241,7 @@ struct glyf
static bool _remove_composite_instruction_flag (hb_bytes_t glyph) static bool _remove_composite_instruction_flag (hb_bytes_t glyph)
{ {
const GlyphHeader &glyph_header = StructAtOffset<GlyphHeader> (&glyph, 0); auto &glyph_header = GlyphHeader::from_bytes (glyph);
if (!glyph_header.is_composite_glyph ()) return true; // only for composites if (!glyph_header.is_composite_glyph ()) return true; // only for composites
/* remove WE_HAVE_INSTRUCTIONS from flags in dest */ /* remove WE_HAVE_INSTRUCTIONS from flags in dest */
@ -279,6 +279,13 @@ struct glyf
struct GlyphHeader struct GlyphHeader
{ {
static const GlyphHeader &from_bytes (hb_bytes_t glyph_bytes)
{
return glyph_bytes.length < GlyphHeader::static_size
? Null (GlyphHeader)
: StructAtOffset<GlyphHeader> (&glyph_bytes, 0);
}
unsigned int simple_instruction_len_offset () const unsigned int simple_instruction_len_offset () const
{ return static_size + 2 * numberOfContours; } { return static_size + 2 * numberOfContours; }
@ -296,15 +303,17 @@ struct glyf
extents->height = hb_min (yMin, yMax) - extents->y_bearing; extents->height = hb_min (yMin, yMax) - extents->y_bearing;
} }
bool has_data () const { return numberOfContours; }
protected: protected:
HBINT16 numberOfContours; /* If the number of contours is HBINT16 numberOfContours;/* If the number of contours is
* greater than or equal to zero, * greater than or equal to zero,
* this is a simple glyph; if negative, * this is a simple glyph; if negative,
* this is a composite glyph. */ * this is a composite glyph. */
FWORD xMin; /* Minimum x for coordinate data. */ FWORD xMin; /* Minimum x for coordinate data. */
FWORD yMin; /* Minimum y for coordinate data. */ FWORD yMin; /* Minimum y for coordinate data. */
FWORD xMax; /* Maximum x for coordinate data. */ FWORD xMax; /* Maximum x for coordinate data. */
FWORD yMax; /* Maximum y for coordinate data. */ FWORD yMax; /* Maximum y for coordinate data. */
public: public:
DEFINE_SIZE_STATIC (10); DEFINE_SIZE_STATIC (10);
}; };
@ -381,10 +390,9 @@ struct glyf
unsigned int length, unsigned int length,
CompositeGlyphHeader::Iterator *iterator /* OUT */) CompositeGlyphHeader::Iterator *iterator /* OUT */)
{ {
if (length < GlyphHeader::static_size) auto &glyph_header = GlyphHeader::from_bytes (hb_bytes_t (glyph_data, length));
return false; /* Empty glyph; zero extents. */ if (!glyph_header.has_data ()) return false; /* Empty glyph; zero extents. */
const GlyphHeader &glyph_header = StructAtOffset<GlyphHeader> (glyph_data, 0);
if (glyph_header.is_composite_glyph ()) if (glyph_header.is_composite_glyph ())
{ {
const CompositeGlyphHeader *possible = const CompositeGlyphHeader *possible =
@ -464,17 +472,17 @@ struct glyf
bool remove_padding (unsigned int start_offset, bool remove_padding (unsigned int start_offset,
unsigned int *end_offset) const unsigned int *end_offset) const
{ {
if (*end_offset - start_offset < GlyphHeader::static_size) return true;
const char *glyph = ((const char *) glyf_table) + start_offset; const char *glyph = ((const char *) glyf_table) + start_offset;
const char * const glyph_end = glyph + (*end_offset - start_offset); unsigned int glyph_length = *end_offset - start_offset;
const GlyphHeader &glyph_header = StructAtOffset<GlyphHeader> (glyph, 0); auto &glyph_header = GlyphHeader::from_bytes (hb_bytes_t (glyph, glyph_length));
if (!glyph_header.has_data ()) return true;
const char *glyph_end = glyph + glyph_length;
if (glyph_header.is_composite_glyph ()) if (glyph_header.is_composite_glyph ())
/* Trimming for composites not implemented. /* Trimming for composites not implemented.
* If removing hints it falls out of that. */ * If removing hints it falls out of that. */
return true; return true;
else if (glyph_header.is_simple_glyph ()) else
{ {
/* simple glyph w/contours, possibly trimmable */ /* simple glyph w/contours, possibly trimmable */
glyph += glyph_header.simple_instruction_len_offset (); glyph += glyph_header.simple_instruction_len_offset ();
@ -563,14 +571,14 @@ struct glyf
bool get_instruction_length (hb_bytes_t glyph, bool get_instruction_length (hb_bytes_t glyph,
unsigned int * length /* OUT */) const unsigned int * length /* OUT */) const
{ {
auto &glyph_header = GlyphHeader::from_bytes (glyph);
/* Empty glyph; no instructions. */ /* Empty glyph; no instructions. */
if (glyph.length < GlyphHeader::static_size) if (!glyph_header.has_data ())
{ {
*length = 0; *length = 0;
// only 0 byte glyphs are healthy when missing GlyphHeader // only 0 byte glyphs are healthy when missing GlyphHeader
return glyph.length == 0; return glyph.length == 0;
} }
const GlyphHeader &glyph_header = StructAtOffset<GlyphHeader> (&glyph, 0);
if (glyph_header.is_composite_glyph ()) if (glyph_header.is_composite_glyph ())
{ {
unsigned int start = glyph.length; unsigned int start = glyph.length;
@ -627,16 +635,12 @@ struct glyf
if (!get_offsets (glyph, &start_offset, &end_offset)) if (!get_offsets (glyph, &start_offset, &end_offset))
return false; return false;
if (end_offset - start_offset < GlyphHeader::static_size) GlyphHeader::from_bytes (hb_bytes_t ((const char *) glyf_table + start_offset,
return true; /* Empty glyph; zero extents. */ end_offset - start_offset)).get_extents (extents);
const GlyphHeader &glyph_header = StructAtOffset<GlyphHeader> (glyf_table,
start_offset);
glyph_header.get_extents (extents);
return true; return true;
} }
hb_bytes_t bytes_for_glyph (const char * glyf, hb_codepoint_t gid) hb_bytes_t bytes_for_glyph (const char *glyf, hb_codepoint_t gid)
{ {
unsigned int start_offset, end_offset; unsigned int start_offset, end_offset;
if (unlikely (!(get_offsets (gid, &start_offset, &end_offset) && if (unlikely (!(get_offsets (gid, &start_offset, &end_offset) &&
@ -645,14 +649,13 @@ struct glyf
DEBUG_MSG (SUBSET, nullptr, "Unable to get offset or remove padding for %d", gid); DEBUG_MSG (SUBSET, nullptr, "Unable to get offset or remove padding for %d", gid);
return hb_bytes_t (); return hb_bytes_t ();
} }
hb_bytes_t glyph = hb_bytes_t (glyf + start_offset, end_offset - start_offset); hb_bytes_t glyph_bytes = hb_bytes_t (glyf + start_offset, end_offset - start_offset);
if (glyph.length == 0) return glyph; if (!GlyphHeader::from_bytes (glyph_bytes).has_data ())
if (unlikely (glyph.length < GlyphHeader::static_size))
{ {
DEBUG_MSG (SUBSET, nullptr, "Glyph size smaller than minimum header %d", gid); DEBUG_MSG (SUBSET, nullptr, "Empty or invalid glyph size, %d", gid);
return hb_bytes_t (); return hb_bytes_t ();
} }
return glyph; return glyph_bytes;
} }
private: private:
@ -714,7 +717,7 @@ struct glyf
return ; return ;
} }
const GlyphHeader& header = StructAtOffset<GlyphHeader> (&source_glyph, 0); const GlyphHeader& header = GlyphHeader::from_bytes (source_glyph);
DEBUG_MSG (SUBSET, nullptr, "new_gid %d drop %d instruction bytes " DEBUG_MSG (SUBSET, nullptr, "new_gid %d drop %d instruction bytes "
"from %d byte source glyph", "from %d byte source glyph",
new_gid, instruction_len, source_glyph.length); new_gid, instruction_len, source_glyph.length);