yusukes@chromium.org | f12575f | 2010-02-02 21:26:17 +0000 | [diff] [blame] | 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. |
agl@chromium.org | 2beaf1d | 2011-01-21 17:19:34 +0000 | [diff] [blame] | 158 | return file->kern != NULL; |
yusukes@chromium.org | f12575f | 2010-02-02 21:26:17 +0000 | [diff] [blame] | 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 |