| // 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/opentype/otspec/kern.htm |
| |
| #define DROP_THIS_TABLE \ |
| do { delete file->kern; file->kern = 0; } while (0) |
| |
| namespace ots { |
| |
| bool ots_kern_parse(OpenTypeFile *file, const uint8_t *data, size_t length) { |
| Buffer table(data, length); |
| |
| OpenTypeKERN *kern = new OpenTypeKERN; |
| file->kern = kern; |
| |
| uint16_t num_tables = 0; |
| if (!table.ReadU16(&kern->version) || |
| !table.ReadU16(&num_tables)) { |
| return OTS_FAILURE(); |
| } |
| |
| if (kern->version > 0) { |
| DROP_THIS_TABLE; |
| return true; |
| } |
| |
| if (num_tables == 0) { |
| OTS_WARNING("num_tables is zero"); |
| DROP_THIS_TABLE; |
| 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(); |
| } |
| |
| 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(); |
| } |
| |
| if (!table.ReadU16(&subtable.coverage)) { |
| return OTS_FAILURE(); |
| } |
| |
| if (!(subtable.coverage & 0x1)) { |
| OTS_WARNING( |
| "We don't support vertical data as the renderer doesn't support it."); |
| continue; |
| } |
| if (subtable.coverage & 0xF0) { |
| OTS_WARNING("Reserved fields should zero-filled."); |
| DROP_THIS_TABLE; |
| 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(); |
| } |
| |
| if (!num_pairs) { |
| OTS_WARNING("Zero length subtable is found."); |
| DROP_THIS_TABLE; |
| 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. |
| OTS_WARNING("Too large subtable."); |
| DROP_THIS_TABLE; |
| 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(); |
| } |
| const uint32_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(); |
| } |
| const uint32_t current_pair |
| = (kerning_pair.left << 16) + kerning_pair.right; |
| if (j != 0 && current_pair <= last_pair) { |
| OTS_WARNING("Kerning pairs are not sorted."); |
| // Many free fonts don't follow this rule, so we don't call OTS_FAILURE |
| // in order to support these fonts. |
| DROP_THIS_TABLE; |
| return true; |
| } |
| last_pair = current_pair; |
| subtable.pairs.push_back(kerning_pair); |
| } |
| |
| kern->subtables.push_back(subtable); |
| } |
| |
| if (!kern->subtables.size()) { |
| OTS_WARNING("All subtables are removed."); |
| DROP_THIS_TABLE; |
| return true; |
| } |
| |
| return true; |
| } |
| |
| bool ots_kern_should_serialise(OpenTypeFile *file) { |
| if (!file->glyf) return false; // this table is not for CFF fonts. |
| return file->kern != NULL; |
| } |
| |
| bool ots_kern_serialise(OTSStream *out, OpenTypeFile *file) { |
| const OpenTypeKERN *kern = file->kern; |
| |
| if (!out->WriteU16(kern->version) || |
| !out->WriteU16(kern->subtables.size())) { |
| return OTS_FAILURE(); |
| } |
| |
| for (unsigned i = 0; i < kern->subtables.size(); ++i) { |
| const uint16_t length = 14 + (6 * kern->subtables[i].pairs.size()); |
| if (!out->WriteU16(kern->subtables[i].version) || |
| !out->WriteU16(length) || |
| !out->WriteU16(kern->subtables[i].coverage) || |
| !out->WriteU16(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(); |
| } |
| 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(); |
| } |
| } |
| } |
| |
| return true; |
| } |
| |
| void ots_kern_free(OpenTypeFile *file) { |
| delete file->kern; |
| } |
| |
| } // namespace ots |