112 lines
2.8 KiB
C++
112 lines
2.8 KiB
C++
/* xdelta3 - delta compression tools and library -*- Mode: C++ -*-
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Copyright 2016 Joshua MacDonald
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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class Segment {
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public:
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Segment(size_t size, MTRandom *rand)
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: size_(size),
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seed_(rand->Rand32()),
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seed_offset_(0),
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data_(NULL) {
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CHECK_GT(size_, 0);
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}
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Segment(size_t size, uint32_t seed)
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: size_(size),
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seed_(seed),
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seed_offset_(0),
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data_(NULL) {
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CHECK_GT(size_, 0);
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}
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Segment(size_t size, uint8_t *data)
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: size_(size),
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seed_(0),
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seed_offset_(0),
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data_(data) {
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CHECK_GT(size_, 0);
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}
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size_t Size() const {
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return size_;
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}
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Segment Subseg(size_t start, size_t size) const {
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CHECK_LE(start + size, size_);
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if (data_) {
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return Segment(size, data_ + start);
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} else {
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return Segment(size, seed_, seed_offset_ + start);
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}
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}
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void Fill(size_t seg_offset, size_t size, uint8_t *data) const {
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CHECK_LE(seg_offset + size, size_);
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if (data_) {
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memcpy(data, data_ + seg_offset, size);
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} else {
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size_t skip = seg_offset + seed_offset_;
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MTRandom gen(seed_);
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MTRandom8 gen8(&gen);
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while (skip--) {
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gen8.Rand8();
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}
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for (size_t i = 0; i < size; i++) {
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data[i] = gen8.Rand8();
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}
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}
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}
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string ToString() const {
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string r;
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if (data_) {
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for (size_t i = 0; i < size_; i++) {
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char buf[10];
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sprintf(buf, "%02x ", data_[i]);
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r.append(buf);
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}
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} else {
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char buf[256];
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sprintf(buf, "size=%ld,seed=%ud,skip=%ld", size_, seed_, seed_offset_);
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r.append(buf);
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}
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return r;
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}
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private:
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// Used by Subseg()
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Segment(size_t size, uint32_t seed, size_t seed_offset)
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: size_(size),
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seed_(seed),
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seed_offset_(seed_offset),
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data_(NULL) {
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CHECK_GT(size_, 0);
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}
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size_t size_; // Size of this segment
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// For random segments
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uint32_t seed_; // Seed used for generating byte sequence
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size_t seed_offset_; // Seed positions the sequence this many bytes
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// before its beginning.
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// For literal segments (data is not owned)
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uint8_t *data_;
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};
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typedef map<xoff_t, Segment> SegmentMap;
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typedef typename SegmentMap::const_iterator ConstSegmentMapIterator;
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typedef typename SegmentMap::iterator SegmentMapIterator;
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