1 // Copyright (c) 2009 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "kern.h" 6 7 // kern - Kerning 8 // http://www.microsoft.com/opentype/otspec/kern.htm 9 10 #define DROP_THIS_TABLE \ 11 do { delete file->kern; file->kern = 0; } while (0) 12 13 namespace ots { 14 15 bool ots_kern_parse(OpenTypeFile *file, const uint8_t *data, size_t length) { 16 Buffer table(data, length); 17 18 OpenTypeKERN *kern = new OpenTypeKERN; 19 file->kern = kern; 20 21 uint16_t num_tables = 0; 22 if (!table.ReadU16(&kern->version) || 23 !table.ReadU16(&num_tables)) { 24 return OTS_FAILURE(); 25 } 26 27 if (kern->version > 0) { 28 DROP_THIS_TABLE; 29 return true; 30 } 31 32 if (num_tables == 0) { 33 OTS_WARNING("num_tables is zero"); 34 DROP_THIS_TABLE; 35 return true; 36 } 37 38 kern->subtables.reserve(num_tables); 39 for (unsigned i = 0; i < num_tables; ++i) { 40 OpenTypeKERNFormat0 subtable; 41 uint16_t sub_length = 0; 42 43 if (!table.ReadU16(&subtable.version) || 44 !table.ReadU16(&sub_length)) { 45 return OTS_FAILURE(); 46 } 47 48 if (subtable.version > 0) { 49 OTS_WARNING("Bad subtable version: %d", subtable.version); 50 continue; 51 } 52 53 const size_t current_offset = table.offset(); 54 if (current_offset - 4 + sub_length > length) { 55 return OTS_FAILURE(); 56 } 57 58 if (!table.ReadU16(&subtable.coverage)) { 59 return OTS_FAILURE(); 60 } 61 62 if (!(subtable.coverage & 0x1)) { 63 OTS_WARNING( 64 "We don't support vertical data as the renderer doesn't support it."); 65 continue; 66 } 67 if (subtable.coverage & 0xF0) { 68 OTS_WARNING("Reserved fields should zero-filled."); 69 DROP_THIS_TABLE; 70 return true; 71 } 72 const uint32_t format = (subtable.coverage & 0xFF00) >> 8; 73 if (format != 0) { 74 OTS_WARNING("Format %d is not supported.", format); 75 continue; 76 } 77 78 // Parse the format 0 field. 79 uint16_t num_pairs = 0; 80 if (!table.ReadU16(&num_pairs) || 81 !table.ReadU16(&subtable.search_range) || 82 !table.ReadU16(&subtable.entry_selector) || 83 !table.ReadU16(&subtable.range_shift)) { 84 return OTS_FAILURE(); 85 } 86 87 if (!num_pairs) { 88 OTS_WARNING("Zero length subtable is found."); 89 DROP_THIS_TABLE; 90 return true; 91 } 92 93 // Sanity checks for search_range, entry_selector, and range_shift. See the 94 // comment in ots.cc for details. 95 const size_t kFormat0PairSize = 6; // left, right, and value. 2 bytes each. 96 if (num_pairs > (65536 / kFormat0PairSize)) { 97 // Some fonts (e.g. calibri.ttf, pykes_peak_zero.ttf) have pairs >= 10923. 98 OTS_WARNING("Too large subtable."); 99 DROP_THIS_TABLE; 100 return true; 101 } 102 unsigned max_pow2 = 0; 103 while (1u << (max_pow2 + 1) <= num_pairs) { 104 ++max_pow2; 105 } 106 const uint16_t expected_search_range = (1u << max_pow2) * kFormat0PairSize; 107 if (subtable.search_range != expected_search_range) { 108 OTS_WARNING("bad search range"); 109 subtable.search_range = expected_search_range; 110 } 111 if (subtable.entry_selector != max_pow2) { 112 return OTS_FAILURE(); 113 } 114 const uint32_t expected_range_shift 115 = kFormat0PairSize * num_pairs - subtable.search_range; 116 if (subtable.range_shift != expected_range_shift) { 117 OTS_WARNING("bad range shift"); 118 subtable.range_shift = expected_range_shift; 119 } 120 121 // Read kerning pairs. 122 subtable.pairs.reserve(num_pairs); 123 uint32_t last_pair = 0; 124 for (unsigned j = 0; j < num_pairs; ++j) { 125 OpenTypeKERNFormat0Pair kerning_pair; 126 if (!table.ReadU16(&kerning_pair.left) || 127 !table.ReadU16(&kerning_pair.right) || 128 !table.ReadS16(&kerning_pair.value)) { 129 return OTS_FAILURE(); 130 } 131 const uint32_t current_pair 132 = (kerning_pair.left << 16) + kerning_pair.right; 133 if (j != 0 && current_pair <= last_pair) { 134 OTS_WARNING("Kerning pairs are not sorted."); 135 // Many free fonts don't follow this rule, so we don't call OTS_FAILURE 136 // in order to support these fonts. 137 DROP_THIS_TABLE; 138 return true; 139 } 140 last_pair = current_pair; 141 subtable.pairs.push_back(kerning_pair); 142 } 143 144 kern->subtables.push_back(subtable); 145 } 146 147 if (!kern->subtables.size()) { 148 OTS_WARNING("All subtables are removed."); 149 DROP_THIS_TABLE; 150 return true; 151 } 152 153 return true; 154 } 155 156 bool ots_kern_should_serialise(OpenTypeFile *file) { 157 if (!file->glyf) return false; // this table is not for CFF fonts. 158 return file->kern != NULL; 159 } 160 161 bool ots_kern_serialise(OTSStream *out, OpenTypeFile *file) { 162 const OpenTypeKERN *kern = file->kern; 163 164 if (!out->WriteU16(kern->version) || 165 !out->WriteU16(kern->subtables.size())) { 166 return OTS_FAILURE(); 167 } 168 169 for (unsigned i = 0; i < kern->subtables.size(); ++i) { 170 const uint16_t length = 14 + (6 * kern->subtables[i].pairs.size()); 171 if (!out->WriteU16(kern->subtables[i].version) || 172 !out->WriteU16(length) || 173 !out->WriteU16(kern->subtables[i].coverage) || 174 !out->WriteU16(kern->subtables[i].pairs.size()) || 175 !out->WriteU16(kern->subtables[i].search_range) || 176 !out->WriteU16(kern->subtables[i].entry_selector) || 177 !out->WriteU16(kern->subtables[i].range_shift)) { 178 return OTS_FAILURE(); 179 } 180 for (unsigned j = 0; j < kern->subtables[i].pairs.size(); ++j) { 181 if (!out->WriteU16(kern->subtables[i].pairs[j].left) || 182 !out->WriteU16(kern->subtables[i].pairs[j].right) || 183 !out->WriteS16(kern->subtables[i].pairs[j].value)) { 184 return OTS_FAILURE(); 185 } 186 } 187 } 188 189 return true; 190 } 191 192 void ots_kern_free(OpenTypeFile *file) { 193 delete file->kern; 194 } 195 196 } // namespace ots 197
