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 0 : bool ots_kern_parse(OpenTypeFile *file, const uint8_t *data, size_t length) {
16 0 : Buffer table(data, length);
17 :
18 0 : OpenTypeKERN *kern = new OpenTypeKERN;
19 0 : file->kern = kern;
20 :
21 0 : uint16_t num_tables = 0;
22 0 : if (!table.ReadU16(&kern->version) ||
23 0 : !table.ReadU16(&num_tables)) {
24 0 : return OTS_FAILURE();
25 : }
26 :
27 0 : if (kern->version > 0) {
28 0 : DROP_THIS_TABLE;
29 0 : return true;
30 : }
31 :
32 0 : if (num_tables == 0) {
33 : OTS_WARNING("num_tables is zero");
34 0 : DROP_THIS_TABLE;
35 0 : return true;
36 : }
37 :
38 0 : kern->subtables.reserve(num_tables);
39 0 : for (unsigned i = 0; i < num_tables; ++i) {
40 0 : OpenTypeKERNFormat0 subtable;
41 0 : uint16_t sub_length = 0;
42 :
43 0 : if (!table.ReadU16(&subtable.version) ||
44 0 : !table.ReadU16(&sub_length)) {
45 0 : return OTS_FAILURE();
46 : }
47 :
48 0 : if (subtable.version > 0) {
49 : OTS_WARNING("Bad subtable version: %d", subtable.version);
50 0 : continue;
51 : }
52 :
53 0 : const size_t current_offset = table.offset();
54 0 : if (current_offset - 4 + sub_length > length) {
55 0 : return OTS_FAILURE();
56 : }
57 :
58 0 : if (!table.ReadU16(&subtable.coverage)) {
59 0 : return OTS_FAILURE();
60 : }
61 :
62 0 : if (!(subtable.coverage & 0x1)) {
63 : OTS_WARNING(
64 : "We don't support vertical data as the renderer doesn't support it.");
65 0 : continue;
66 : }
67 0 : if (subtable.coverage & 0xF0) {
68 : OTS_WARNING("Reserved fields should zero-filled.");
69 0 : DROP_THIS_TABLE;
70 0 : return true;
71 : }
72 0 : const uint32_t format = (subtable.coverage & 0xFF00) >> 8;
73 0 : if (format != 0) {
74 : OTS_WARNING("Format %d is not supported.", format);
75 0 : continue;
76 : }
77 :
78 : // Parse the format 0 field.
79 0 : uint16_t num_pairs = 0;
80 0 : if (!table.ReadU16(&num_pairs) ||
81 0 : !table.ReadU16(&subtable.search_range) ||
82 0 : !table.ReadU16(&subtable.entry_selector) ||
83 0 : !table.ReadU16(&subtable.range_shift)) {
84 0 : return OTS_FAILURE();
85 : }
86 :
87 0 : if (!num_pairs) {
88 : OTS_WARNING("Zero length subtable is found.");
89 0 : DROP_THIS_TABLE;
90 0 : 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 0 : const size_t kFormat0PairSize = 6; // left, right, and value. 2 bytes each.
96 0 : 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 0 : DROP_THIS_TABLE;
100 0 : return true;
101 : }
102 0 : unsigned max_pow2 = 0;
103 0 : while (1u << (max_pow2 + 1) <= num_pairs) {
104 0 : ++max_pow2;
105 : }
106 0 : const uint16_t expected_search_range = (1u << max_pow2) * kFormat0PairSize;
107 0 : if (subtable.search_range != expected_search_range) {
108 : OTS_WARNING("bad search range");
109 0 : subtable.search_range = expected_search_range;
110 : }
111 0 : if (subtable.entry_selector != max_pow2) {
112 0 : return OTS_FAILURE();
113 : }
114 : const uint32_t expected_range_shift
115 0 : = kFormat0PairSize * num_pairs - subtable.search_range;
116 0 : if (subtable.range_shift != expected_range_shift) {
117 : OTS_WARNING("bad range shift");
118 0 : subtable.range_shift = expected_range_shift;
119 : }
120 :
121 : // Read kerning pairs.
122 0 : subtable.pairs.reserve(num_pairs);
123 0 : uint32_t last_pair = 0;
124 0 : for (unsigned j = 0; j < num_pairs; ++j) {
125 : OpenTypeKERNFormat0Pair kerning_pair;
126 0 : if (!table.ReadU16(&kerning_pair.left) ||
127 0 : !table.ReadU16(&kerning_pair.right) ||
128 0 : !table.ReadS16(&kerning_pair.value)) {
129 0 : return OTS_FAILURE();
130 : }
131 : const uint32_t current_pair
132 0 : = (kerning_pair.left << 16) + kerning_pair.right;
133 0 : 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 0 : DROP_THIS_TABLE;
138 0 : return true;
139 : }
140 0 : last_pair = current_pair;
141 0 : subtable.pairs.push_back(kerning_pair);
142 : }
143 :
144 0 : kern->subtables.push_back(subtable);
145 : }
146 :
147 0 : if (!kern->subtables.size()) {
148 : OTS_WARNING("All subtables are removed.");
149 0 : DROP_THIS_TABLE;
150 0 : return true;
151 : }
152 :
153 0 : return true;
154 : }
155 :
156 0 : bool ots_kern_should_serialise(OpenTypeFile *file) {
157 0 : if (!file->glyf) return false; // this table is not for CFF fonts.
158 0 : return file->kern != NULL;
159 : }
160 :
161 0 : bool ots_kern_serialise(OTSStream *out, OpenTypeFile *file) {
162 0 : const OpenTypeKERN *kern = file->kern;
163 :
164 0 : if (!out->WriteU16(kern->version) ||
165 0 : !out->WriteU16(kern->subtables.size())) {
166 0 : return OTS_FAILURE();
167 : }
168 :
169 0 : for (unsigned i = 0; i < kern->subtables.size(); ++i) {
170 0 : const uint16_t length = 14 + (6 * kern->subtables[i].pairs.size());
171 0 : if (!out->WriteU16(kern->subtables[i].version) ||
172 0 : !out->WriteU16(length) ||
173 0 : !out->WriteU16(kern->subtables[i].coverage) ||
174 0 : !out->WriteU16(kern->subtables[i].pairs.size()) ||
175 0 : !out->WriteU16(kern->subtables[i].search_range) ||
176 0 : !out->WriteU16(kern->subtables[i].entry_selector) ||
177 0 : !out->WriteU16(kern->subtables[i].range_shift)) {
178 0 : return OTS_FAILURE();
179 : }
180 0 : for (unsigned j = 0; j < kern->subtables[i].pairs.size(); ++j) {
181 0 : if (!out->WriteU16(kern->subtables[i].pairs[j].left) ||
182 0 : !out->WriteU16(kern->subtables[i].pairs[j].right) ||
183 0 : !out->WriteS16(kern->subtables[i].pairs[j].value)) {
184 0 : return OTS_FAILURE();
185 : }
186 : }
187 : }
188 :
189 0 : return true;
190 : }
191 :
192 0 : void ots_kern_free(OpenTypeFile *file) {
193 0 : delete file->kern;
194 0 : }
195 :
196 : } // namespace ots
|