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-rw-r--r--gfx/ots/src/kern.cc208
1 files changed, 208 insertions, 0 deletions
diff --git a/gfx/ots/src/kern.cc b/gfx/ots/src/kern.cc
new file mode 100644
index 000000000..d4ae8fcc4
--- /dev/null
+++ b/gfx/ots/src/kern.cc
@@ -0,0 +1,208 @@
+// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "kern.h"
+
+// kern - Kerning
+// http://www.microsoft.com/typography/otspec/kern.htm
+
+#define TABLE_NAME "kern"
+
+#define DROP_THIS_TABLE(msg_) \
+ do { \
+ OTS_FAILURE_MSG(msg_ ", table discarded"); \
+ delete font->kern; \
+ font->kern = 0; \
+ } while (0)
+
+namespace ots {
+
+bool ots_kern_parse(Font *font, const uint8_t *data, size_t length) {
+ Buffer table(data, length);
+
+ OpenTypeKERN *kern = new OpenTypeKERN;
+ font->kern = kern;
+
+ uint16_t num_tables = 0;
+ if (!table.ReadU16(&kern->version) ||
+ !table.ReadU16(&num_tables)) {
+ return OTS_FAILURE_MSG("Failed to read kern header");
+ }
+
+ if (kern->version > 0) {
+ DROP_THIS_TABLE("bad table version");
+ return true;
+ }
+
+ if (num_tables == 0) {
+ DROP_THIS_TABLE("num_tables is zero");
+ return true;
+ }
+
+ kern->subtables.reserve(num_tables);
+ for (unsigned i = 0; i < num_tables; ++i) {
+ OpenTypeKERNFormat0 subtable;
+ uint16_t sub_length = 0;
+
+ if (!table.ReadU16(&subtable.version) ||
+ !table.ReadU16(&sub_length)) {
+ return OTS_FAILURE_MSG("Failed to read kern subtable %d header", i);
+ }
+
+ if (subtable.version > 0) {
+ OTS_WARNING("Bad subtable version: %d", subtable.version);
+ continue;
+ }
+
+ const size_t current_offset = table.offset();
+ if (current_offset - 4 + sub_length > length) {
+ return OTS_FAILURE_MSG("Bad kern subtable %d offset %ld", i, current_offset);
+ }
+
+ if (!table.ReadU16(&subtable.coverage)) {
+ return OTS_FAILURE_MSG("Cailed to read kern subtable %d coverage", i);
+ }
+
+ if (!(subtable.coverage & 0x1)) {
+ OTS_WARNING(
+ "We don't support vertical data as the renderer doesn't support it.");
+ continue;
+ }
+ if (subtable.coverage & 0xF0) {
+ DROP_THIS_TABLE("Reserved fields should zero-filled");
+ return true;
+ }
+ const uint32_t format = (subtable.coverage & 0xFF00) >> 8;
+ if (format != 0) {
+ OTS_WARNING("Format %d is not supported.", format);
+ continue;
+ }
+
+ // Parse the format 0 field.
+ uint16_t num_pairs = 0;
+ if (!table.ReadU16(&num_pairs) ||
+ !table.ReadU16(&subtable.search_range) ||
+ !table.ReadU16(&subtable.entry_selector) ||
+ !table.ReadU16(&subtable.range_shift)) {
+ return OTS_FAILURE_MSG("Failed to read kern subtable %d format 0 fields", i);
+ }
+
+ if (!num_pairs) {
+ DROP_THIS_TABLE("Zero length subtable is found");
+ return true;
+ }
+
+ // Sanity checks for search_range, entry_selector, and range_shift. See the
+ // comment in ots.cc for details.
+ const size_t kFormat0PairSize = 6; // left, right, and value. 2 bytes each.
+ if (num_pairs > (65536 / kFormat0PairSize)) {
+ // Some fonts (e.g. calibri.ttf, pykes_peak_zero.ttf) have pairs >= 10923.
+ DROP_THIS_TABLE("Too large subtable");
+ return true;
+ }
+ unsigned max_pow2 = 0;
+ while (1u << (max_pow2 + 1) <= num_pairs) {
+ ++max_pow2;
+ }
+ const uint16_t expected_search_range = (1u << max_pow2) * kFormat0PairSize;
+ if (subtable.search_range != expected_search_range) {
+ OTS_WARNING("bad search range");
+ subtable.search_range = expected_search_range;
+ }
+ if (subtable.entry_selector != max_pow2) {
+ return OTS_FAILURE_MSG("Bad subtable %d entry selector %d", i, subtable.entry_selector);
+ }
+ const uint16_t expected_range_shift =
+ kFormat0PairSize * num_pairs - subtable.search_range;
+ if (subtable.range_shift != expected_range_shift) {
+ OTS_WARNING("bad range shift");
+ subtable.range_shift = expected_range_shift;
+ }
+
+ // Read kerning pairs.
+ subtable.pairs.reserve(num_pairs);
+ uint32_t last_pair = 0;
+ for (unsigned j = 0; j < num_pairs; ++j) {
+ OpenTypeKERNFormat0Pair kerning_pair;
+ if (!table.ReadU16(&kerning_pair.left) ||
+ !table.ReadU16(&kerning_pair.right) ||
+ !table.ReadS16(&kerning_pair.value)) {
+ return OTS_FAILURE_MSG("Failed to read subtable %d kerning pair %d", i, j);
+ }
+ const uint32_t current_pair
+ = (kerning_pair.left << 16) + kerning_pair.right;
+ if (j != 0 && current_pair <= last_pair) {
+ // Many free fonts don't follow this rule, so we don't call OTS_FAILURE
+ // in order to support these fonts.
+ DROP_THIS_TABLE("Kerning pairs are not sorted");
+ return true;
+ }
+ last_pair = current_pair;
+ subtable.pairs.push_back(kerning_pair);
+ }
+
+ kern->subtables.push_back(subtable);
+ }
+
+ if (!kern->subtables.size()) {
+ DROP_THIS_TABLE("All subtables are removed");
+ return true;
+ }
+
+ return true;
+}
+
+bool ots_kern_should_serialise(Font *font) {
+ if (!font->glyf) return false; // this table is not for CFF fonts.
+ return font->kern != NULL;
+}
+
+bool ots_kern_serialise(OTSStream *out, Font *font) {
+ const OpenTypeKERN *kern = font->kern;
+
+ const uint16_t num_subtables = static_cast<uint16_t>(kern->subtables.size());
+ if (num_subtables != kern->subtables.size() ||
+ !out->WriteU16(kern->version) ||
+ !out->WriteU16(num_subtables)) {
+ return OTS_FAILURE_MSG("Can't write kern table header");
+ }
+
+ for (uint16_t i = 0; i < num_subtables; ++i) {
+ const size_t length = 14 + (6 * kern->subtables[i].pairs.size());
+ if (length > std::numeric_limits<uint16_t>::max() ||
+ !out->WriteU16(kern->subtables[i].version) ||
+ !out->WriteU16(static_cast<uint16_t>(length)) ||
+ !out->WriteU16(kern->subtables[i].coverage) ||
+ !out->WriteU16(
+ static_cast<uint16_t>(kern->subtables[i].pairs.size())) ||
+ !out->WriteU16(kern->subtables[i].search_range) ||
+ !out->WriteU16(kern->subtables[i].entry_selector) ||
+ !out->WriteU16(kern->subtables[i].range_shift)) {
+ return OTS_FAILURE_MSG("Failed to write kern subtable %d", i);
+ }
+ for (unsigned j = 0; j < kern->subtables[i].pairs.size(); ++j) {
+ if (!out->WriteU16(kern->subtables[i].pairs[j].left) ||
+ !out->WriteU16(kern->subtables[i].pairs[j].right) ||
+ !out->WriteS16(kern->subtables[i].pairs[j].value)) {
+ return OTS_FAILURE_MSG("Failed to write kern pair %d for subtable %d", j, i);
+ }
+ }
+ }
+
+ return true;
+}
+
+void ots_kern_reuse(Font *font, Font *other) {
+ font->kern = other->kern;
+ font->kern_reused = true;
+}
+
+void ots_kern_free(Font *font) {
+ delete font->kern;
+}
+
+} // namespace ots
+
+#undef TABLE_NAME
+#undef DROP_THIS_TABLE