CmapCoverage.cpp revision 6b1c227da6492a435f0341d7fe95d9992669920e 
1/*
2 * Copyright (C) 2013 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17// Determine coverage of font given its raw "cmap" OpenType table
18
19#define LOG_TAG "Minikin"
20#include <cutils/log.h>
21
22#include <vector>
23using std::vector;
24
25#include <minikin/SparseBitSet.h>
26#include <minikin/CmapCoverage.h>
27
28namespace android {
29
30// These could perhaps be optimized to use __builtin_bswap16 and friends.
31static uint32_t readU16(const uint8_t* data, size_t offset) {
32    return ((uint32_t)data[offset]) << 8 | ((uint32_t)data[offset + 1]);
33}
34
35static uint32_t readU32(const uint8_t* data, size_t offset) {
36    return ((uint32_t)data[offset]) << 24 | ((uint32_t)data[offset + 1]) << 16 |
37        ((uint32_t)data[offset + 2]) << 8 | ((uint32_t)data[offset + 3]);
38}
39
40static void addRange(vector<uint32_t> &coverage, uint32_t start, uint32_t end) {
41#ifdef VERBOSE_DEBUG
42    ALOGD("adding range %d-%d\n", start, end);
43#endif
44    if (coverage.empty() || coverage.back() < start) {
45        coverage.push_back(start);
46        coverage.push_back(end);
47    } else {
48        coverage.back() = end;
49    }
50}
51
52// Get the coverage information out of a Format 4 subtable, storing it in the coverage vector
53static bool getCoverageFormat4(vector<uint32_t>& coverage, const uint8_t* data, size_t size) {
54    const size_t kSegCountOffset = 6;
55    const size_t kEndCountOffset = 14;
56    const size_t kHeaderSize = 16;
57    const size_t kSegmentSize = 8;  // total size of array elements for one segment
58    if (kEndCountOffset > size) {
59        return false;
60    }
61    size_t segCount = readU16(data, kSegCountOffset) >> 1;
62    if (kHeaderSize + segCount * kSegmentSize > size) {
63        return false;
64    }
65    for (size_t i = 0; i < segCount; i++) {
66        uint32_t end = readU16(data, kEndCountOffset + 2 * i);
67        uint32_t start = readU16(data, kHeaderSize + 2 * (segCount + i));
68        if (end < start) {
69            // invalid segment range: size must be positive
70            return false;
71        }
72        uint32_t rangeOffset = readU16(data, kHeaderSize + 2 * (3 * segCount + i));
73        if (rangeOffset == 0) {
74            uint32_t delta = readU16(data, kHeaderSize + 2 * (2 * segCount + i));
75            if (((end + delta) & 0xffff) > end - start) {
76                addRange(coverage, start, end + 1);
77            } else {
78                for (uint32_t j = start; j < end + 1; j++) {
79                    if (((j + delta) & 0xffff) != 0) {
80                        addRange(coverage, j, j + 1);
81                    }
82                }
83            }
84        } else {
85            for (uint32_t j = start; j < end + 1; j++) {
86                uint32_t actualRangeOffset = kHeaderSize + 6 * segCount + rangeOffset +
87                    (i + j - start) * 2;
88                if (actualRangeOffset + 2 > size) {
89                    // invalid rangeOffset is considered a "warning" by OpenType Sanitizer
90                    continue;
91                }
92                uint32_t glyphId = readU16(data, actualRangeOffset);
93                if (glyphId != 0) {
94                    addRange(coverage, j, j + 1);
95                }
96            }
97        }
98    }
99    return true;
100}
101
102// Get the coverage information out of a Format 12 subtable, storing it in the coverage vector
103static bool getCoverageFormat12(vector<uint32_t>& coverage, const uint8_t* data, size_t size) {
104    const size_t kNGroupsOffset = 12;
105    const size_t kFirstGroupOffset = 16;
106    const size_t kGroupSize = 12;
107    const size_t kStartCharCodeOffset = 0;
108    const size_t kEndCharCodeOffset = 4;
109    const size_t kMaxNGroups = 0xfffffff0 / kGroupSize;  // protection against overflow
110    // For all values < kMaxNGroups, kFirstGroupOffset + nGroups * kGroupSize fits in 32 bits.
111    if (kFirstGroupOffset > size) {
112        return false;
113    }
114    uint32_t nGroups = readU32(data, kNGroupsOffset);
115    if (nGroups >= kMaxNGroups || kFirstGroupOffset + nGroups * kGroupSize > size) {
116        return false;
117    }
118    for (uint32_t i = 0; i < nGroups; i++) {
119        uint32_t groupOffset = kFirstGroupOffset + i * kGroupSize;
120        uint32_t start = readU32(data, groupOffset + kStartCharCodeOffset);
121        uint32_t end = readU32(data, groupOffset + kEndCharCodeOffset);
122        if (end < start) {
123            // invalid group range: size must be positive
124            return false;
125        }
126        addRange(coverage, start, end + 1);  // file is inclusive, vector is exclusive
127    }
128    return true;
129}
130
131bool CmapCoverage::getCoverage(SparseBitSet& coverage, const uint8_t* cmap_data, size_t cmap_size,
132        bool* has_cmap_format14_subtable) {
133    vector<uint32_t> coverageVec;
134    const size_t kHeaderSize = 4;
135    const size_t kNumTablesOffset = 2;
136    const size_t kTableSize = 8;
137    const size_t kPlatformIdOffset = 0;
138    const size_t kEncodingIdOffset = 2;
139    const size_t kOffsetOffset = 4;
140    const uint16_t kUnicodePlatformId = 0;
141    const uint16_t kMicrosoftPlatformId = 3;
142    const uint16_t kUnicodeBmpEncodingId = 1;
143    const uint16_t kVariationSequencesEncodingId = 5;
144    const uint16_t kUnicodeUcs4EncodingId = 10;
145    const uint32_t kNoTable = UINT32_MAX;
146    if (kHeaderSize > cmap_size) {
147        return false;
148    }
149    uint32_t numTables = readU16(cmap_data, kNumTablesOffset);
150    if (kHeaderSize + numTables * kTableSize > cmap_size) {
151        return false;
152    }
153    uint32_t bestTable = kNoTable;
154    bool hasCmapFormat14Subtable = false;
155    for (uint32_t i = 0; i < numTables; i++) {
156        uint16_t platformId = readU16(cmap_data, kHeaderSize + i * kTableSize + kPlatformIdOffset);
157        uint16_t encodingId = readU16(cmap_data, kHeaderSize + i * kTableSize + kEncodingIdOffset);
158        if (platformId == kMicrosoftPlatformId && encodingId == kUnicodeUcs4EncodingId) {
159            bestTable = i;
160            break;
161        } else if (platformId == kMicrosoftPlatformId && encodingId == kUnicodeBmpEncodingId) {
162            bestTable = i;
163        } else if (platformId == kUnicodePlatformId &&
164                encodingId == kVariationSequencesEncodingId) {
165            uint32_t offset = readU32(cmap_data, kHeaderSize + i * kTableSize + kOffsetOffset);
166            if (offset <= cmap_size - 2 && readU16(cmap_data, offset) == 14) {
167                hasCmapFormat14Subtable = true;
168            }
169        }
170    }
171    *has_cmap_format14_subtable = hasCmapFormat14Subtable;
172#ifdef VERBOSE_DEBUG
173    ALOGD("best table = %d\n", bestTable);
174#endif
175    if (bestTable == kNoTable) {
176        return false;
177    }
178    uint32_t offset = readU32(cmap_data, kHeaderSize + bestTable * kTableSize + kOffsetOffset);
179    if (offset > cmap_size - 2) {
180        return false;
181    }
182    uint16_t format = readU16(cmap_data, offset);
183    bool success = false;
184    const uint8_t* tableData = cmap_data + offset;
185    const size_t tableSize = cmap_size - offset;
186    if (format == 4) {
187        success = getCoverageFormat4(coverageVec, tableData, tableSize);
188    } else if (format == 12) {
189        success = getCoverageFormat12(coverageVec, tableData, tableSize);
190    }
191    if (success) {
192        coverage.initFromRanges(&coverageVec.front(), coverageVec.size() >> 1);
193    }
194#ifdef VERBOSE_DEBUG
195    for (size_t i = 0; i < coverageVec.size(); i += 2) {
196        ALOGD("%x:%x\n", coverageVec[i], coverageVec[i + 1]);
197    }
198    ALOGD("success = %d", success);
199#endif
200    return success;
201}
202
203}  // namespace android
204