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-rw-r--r--otautil/rangeset.cpp267
1 files changed, 267 insertions, 0 deletions
diff --git a/otautil/rangeset.cpp b/otautil/rangeset.cpp
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+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "otautil/rangeset.h"
+
+#include <limits.h>
+#include <stddef.h>
+
+#include <algorithm>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include <android-base/logging.h>
+#include <android-base/parseint.h>
+#include <android-base/stringprintf.h>
+#include <android-base/strings.h>
+
+RangeSet::RangeSet(std::vector<Range>&& pairs) {
+ blocks_ = 0;
+ if (pairs.empty()) {
+ LOG(ERROR) << "Invalid number of tokens";
+ return;
+ }
+
+ for (const auto& range : pairs) {
+ if (!PushBack(range)) {
+ Clear();
+ return;
+ }
+ }
+}
+
+RangeSet RangeSet::Parse(const std::string& range_text) {
+ std::vector<std::string> pieces = android::base::Split(range_text, ",");
+ if (pieces.size() < 3) {
+ LOG(ERROR) << "Invalid range text: " << range_text;
+ return {};
+ }
+
+ size_t num;
+ if (!android::base::ParseUint(pieces[0], &num, static_cast<size_t>(INT_MAX))) {
+ LOG(ERROR) << "Failed to parse the number of tokens: " << range_text;
+ return {};
+ }
+ if (num == 0) {
+ LOG(ERROR) << "Invalid number of tokens: " << range_text;
+ return {};
+ }
+ if (num % 2 != 0) {
+ LOG(ERROR) << "Number of tokens must be even: " << range_text;
+ return {};
+ }
+ if (num != pieces.size() - 1) {
+ LOG(ERROR) << "Mismatching number of tokens: " << range_text;
+ return {};
+ }
+
+ std::vector<Range> pairs;
+ for (size_t i = 0; i < num; i += 2) {
+ size_t first;
+ size_t second;
+ if (!android::base::ParseUint(pieces[i + 1], &first, static_cast<size_t>(INT_MAX)) ||
+ !android::base::ParseUint(pieces[i + 2], &second, static_cast<size_t>(INT_MAX))) {
+ return {};
+ }
+ pairs.emplace_back(first, second);
+ }
+ return RangeSet(std::move(pairs));
+}
+
+bool RangeSet::PushBack(Range range) {
+ if (range.first >= range.second) {
+ LOG(ERROR) << "Empty or negative range: " << range.first << ", " << range.second;
+ return false;
+ }
+ size_t sz = range.second - range.first;
+ if (blocks_ >= SIZE_MAX - sz) {
+ LOG(ERROR) << "RangeSet size overflow";
+ return false;
+ }
+
+ ranges_.push_back(std::move(range));
+ blocks_ += sz;
+ return true;
+}
+
+void RangeSet::Clear() {
+ ranges_.clear();
+ blocks_ = 0;
+}
+
+std::vector<RangeSet> RangeSet::Split(size_t groups) const {
+ if (ranges_.empty() || groups == 0) return {};
+
+ if (blocks_ < groups) {
+ groups = blocks_;
+ }
+
+ // Evenly distribute blocks, with the first few groups possibly containing one more.
+ size_t mean = blocks_ / groups;
+ std::vector<size_t> blocks_per_group(groups, mean);
+ std::fill_n(blocks_per_group.begin(), blocks_ % groups, mean + 1);
+
+ std::vector<RangeSet> result;
+
+ // Forward iterate Ranges and fill up each group with the desired number of blocks.
+ auto it = ranges_.cbegin();
+ Range range = *it;
+ for (const auto& blocks : blocks_per_group) {
+ RangeSet buffer;
+ size_t needed = blocks;
+ while (needed > 0) {
+ size_t range_blocks = range.second - range.first;
+ if (range_blocks > needed) {
+ // Split the current range and don't advance the iterator.
+ buffer.PushBack({ range.first, range.first + needed });
+ range.first = range.first + needed;
+ break;
+ }
+ buffer.PushBack(range);
+ it++;
+ if (it != ranges_.cend()) {
+ range = *it;
+ }
+ needed -= range_blocks;
+ }
+ result.push_back(std::move(buffer));
+ }
+ return result;
+}
+
+std::string RangeSet::ToString() const {
+ if (ranges_.empty()) {
+ return "";
+ }
+ std::string result = std::to_string(ranges_.size() * 2);
+ for (const auto& r : ranges_) {
+ result += android::base::StringPrintf(",%zu,%zu", r.first, r.second);
+ }
+
+ return result;
+}
+
+// Get the block number for the i-th (starting from 0) block in the RangeSet.
+size_t RangeSet::GetBlockNumber(size_t idx) const {
+ CHECK_LT(idx, blocks_) << "Out of bound index " << idx << " (total blocks: " << blocks_ << ")";
+
+ for (const auto& range : ranges_) {
+ if (idx < range.second - range.first) {
+ return range.first + idx;
+ }
+ idx -= (range.second - range.first);
+ }
+
+ CHECK(false) << "Failed to find block number for index " << idx;
+ return 0; // Unreachable, but to make compiler happy.
+}
+
+// RangeSet has half-closed half-open bounds. For example, "3,5" contains blocks 3 and 4. So "3,5"
+// and "5,7" are not overlapped.
+bool RangeSet::Overlaps(const RangeSet& other) const {
+ for (const auto& range : ranges_) {
+ size_t start = range.first;
+ size_t end = range.second;
+ for (const auto& other_range : other.ranges_) {
+ size_t other_start = other_range.first;
+ size_t other_end = other_range.second;
+ // [start, end) vs [other_start, other_end)
+ if (!(other_start >= end || start >= other_end)) {
+ return true;
+ }
+ }
+ }
+ return false;
+}
+
+// Ranges in the the set should be mutually exclusive; and they're sorted by the start block.
+SortedRangeSet::SortedRangeSet(std::vector<Range>&& pairs) : RangeSet(std::move(pairs)) {
+ std::sort(ranges_.begin(), ranges_.end());
+}
+
+void SortedRangeSet::Insert(const Range& to_insert) {
+ SortedRangeSet rs({ to_insert });
+ Insert(rs);
+}
+
+// Insert the input SortedRangeSet; keep the ranges sorted and merge the overlap ranges.
+void SortedRangeSet::Insert(const SortedRangeSet& rs) {
+ if (rs.size() == 0) {
+ return;
+ }
+ // Merge and sort the two RangeSets.
+ std::vector<Range> temp = std::move(ranges_);
+ std::copy(rs.begin(), rs.end(), std::back_inserter(temp));
+ std::sort(temp.begin(), temp.end());
+
+ Clear();
+ // Trim overlaps and insert the result back to ranges_.
+ Range to_insert = temp.front();
+ for (auto it = temp.cbegin() + 1; it != temp.cend(); it++) {
+ if (it->first <= to_insert.second) {
+ to_insert.second = std::max(to_insert.second, it->second);
+ } else {
+ ranges_.push_back(to_insert);
+ blocks_ += (to_insert.second - to_insert.first);
+ to_insert = *it;
+ }
+ }
+ ranges_.push_back(to_insert);
+ blocks_ += (to_insert.second - to_insert.first);
+}
+
+// Compute the block range the file occupies, and insert that range.
+void SortedRangeSet::Insert(size_t start, size_t len) {
+ Range to_insert{ start / kBlockSize, (start + len - 1) / kBlockSize + 1 };
+ Insert(to_insert);
+}
+
+bool SortedRangeSet::Overlaps(size_t start, size_t len) const {
+ RangeSet rs({ { start / kBlockSize, (start + len - 1) / kBlockSize + 1 } });
+ return Overlaps(rs);
+}
+
+// Given an offset of the file, checks if the corresponding block (by considering the file as
+// 0-based continuous block ranges) is covered by the SortedRangeSet. If so, returns the offset
+// within this SortedRangeSet.
+//
+// For example, the 4106-th byte of a file is from block 1, assuming a block size of 4096-byte.
+// The mapped offset within a SortedRangeSet("1-9 15-19") is 10.
+//
+// An offset of 65546 falls into the 16-th block in a file. Block 16 is contained as the 10-th
+// item in SortedRangeSet("1-9 15-19"). So its data can be found at offset 40970 (i.e. 4096 * 10
+// + 10) in a range represented by this SortedRangeSet.
+size_t SortedRangeSet::GetOffsetInRangeSet(size_t old_offset) const {
+ size_t old_block_start = old_offset / kBlockSize;
+ size_t new_block_start = 0;
+ for (const auto& range : ranges_) {
+ // Find the index of old_block_start.
+ if (old_block_start >= range.second) {
+ new_block_start += (range.second - range.first);
+ } else if (old_block_start >= range.first) {
+ new_block_start += (old_block_start - range.first);
+ return (new_block_start * kBlockSize + old_offset % kBlockSize);
+ } else {
+ CHECK(false) << "block_start " << old_block_start
+ << " is missing between two ranges: " << this->ToString();
+ return 0;
+ }
+ }
+ CHECK(false) << "block_start " << old_block_start
+ << " exceeds the limit of current RangeSet: " << this->ToString();
+ return 0;
+}