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1 : // Copyright 2015 Google Inc. All Rights Reserved.
2 : //
3 : // Licensed under the Apache License, Version 2.0 (the "License");
4 : // you may not use this file except in compliance with the License.
5 : // You may obtain a copy of the License at
6 : //
7 : // http://www.apache.org/licenses/LICENSE-2.0
8 : //
9 : // Unless required by applicable law or agreed to in writing, software
10 : // distributed under the License is distributed on an "AS IS" BASIS,
11 : // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 : // See the License for the specific language governing permissions and
13 : // limitations under the License.
14 : //
15 : // Helper functions for woff2 variable length types: 255UInt16 and UIntBase128
16 :
17 : #include "./variable_length.h"
18 :
19 : namespace woff2 {
20 :
21 0 : size_t Size255UShort(uint16_t value) {
22 0 : size_t result = 3;
23 0 : if (value < 253) {
24 0 : result = 1;
25 0 : } else if (value < 762) {
26 0 : result = 2;
27 : } else {
28 0 : result = 3;
29 : }
30 0 : return result;
31 : }
32 :
33 0 : void Write255UShort(std::vector<uint8_t>* out, int value) {
34 0 : if (value < 253) {
35 0 : out->push_back(value);
36 0 : } else if (value < 506) {
37 0 : out->push_back(255);
38 0 : out->push_back(value - 253);
39 0 : } else if (value < 762) {
40 0 : out->push_back(254);
41 0 : out->push_back(value - 506);
42 : } else {
43 0 : out->push_back(253);
44 0 : out->push_back(value >> 8);
45 0 : out->push_back(value & 0xff);
46 : }
47 0 : }
48 :
49 0 : void Store255UShort(int val, size_t* offset, uint8_t* dst) {
50 0 : std::vector<uint8_t> packed;
51 0 : Write255UShort(&packed, val);
52 0 : for (uint8_t val : packed) {
53 0 : dst[(*offset)++] = val;
54 : }
55 0 : }
56 :
57 : // Based on section 6.1.1 of MicroType Express draft spec
58 0 : bool Read255UShort(Buffer* buf, unsigned int* value) {
59 : static const int kWordCode = 253;
60 : static const int kOneMoreByteCode2 = 254;
61 : static const int kOneMoreByteCode1 = 255;
62 : static const int kLowestUCode = 253;
63 0 : uint8_t code = 0;
64 0 : if (!buf->ReadU8(&code)) {
65 0 : return FONT_COMPRESSION_FAILURE();
66 : }
67 0 : if (code == kWordCode) {
68 0 : uint16_t result = 0;
69 0 : if (!buf->ReadU16(&result)) {
70 0 : return FONT_COMPRESSION_FAILURE();
71 : }
72 0 : *value = result;
73 0 : return true;
74 0 : } else if (code == kOneMoreByteCode1) {
75 0 : uint8_t result = 0;
76 0 : if (!buf->ReadU8(&result)) {
77 0 : return FONT_COMPRESSION_FAILURE();
78 : }
79 0 : *value = result + kLowestUCode;
80 0 : return true;
81 0 : } else if (code == kOneMoreByteCode2) {
82 0 : uint8_t result = 0;
83 0 : if (!buf->ReadU8(&result)) {
84 0 : return FONT_COMPRESSION_FAILURE();
85 : }
86 0 : *value = result + kLowestUCode * 2;
87 0 : return true;
88 : } else {
89 0 : *value = code;
90 0 : return true;
91 : }
92 : }
93 :
94 0 : bool ReadBase128(Buffer* buf, uint32_t* value) {
95 0 : uint32_t result = 0;
96 0 : for (size_t i = 0; i < 5; ++i) {
97 0 : uint8_t code = 0;
98 0 : if (!buf->ReadU8(&code)) {
99 0 : return FONT_COMPRESSION_FAILURE();
100 : }
101 : // Leading zeros are invalid.
102 0 : if (i == 0 && code == 0x80) {
103 0 : return FONT_COMPRESSION_FAILURE();
104 : }
105 : // If any of the top seven bits are set then we're about to overflow.
106 0 : if (result & 0xfe000000) {
107 0 : return FONT_COMPRESSION_FAILURE();
108 : }
109 0 : result = (result << 7) | (code & 0x7f);
110 0 : if ((code & 0x80) == 0) {
111 0 : *value = result;
112 0 : return true;
113 : }
114 : }
115 : // Make sure not to exceed the size bound
116 0 : return FONT_COMPRESSION_FAILURE();
117 : }
118 :
119 0 : size_t Base128Size(size_t n) {
120 0 : size_t size = 1;
121 0 : for (; n >= 128; n >>= 7) ++size;
122 0 : return size;
123 : }
124 :
125 0 : void StoreBase128(size_t len, size_t* offset, uint8_t* dst) {
126 0 : size_t size = Base128Size(len);
127 0 : for (size_t i = 0; i < size; ++i) {
128 0 : int b = static_cast<int>((len >> (7 * (size - i - 1))) & 0x7f);
129 0 : if (i < size - 1) {
130 0 : b |= 0x80;
131 : }
132 0 : dst[(*offset)++] = b;
133 : }
134 0 : }
135 :
136 : } // namespace woff2
137 :
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