2 files changed, 48 insertions, 0 deletions

diff --git a/otautil/include/otautil/rangeset.h b/otautil/include/otautil/rangeset.h
index af8ae2dee..e91d02ca6 100644
--- a/otautil/include/otautil/rangeset.h
+++ b/otautil/include/otautil/rangeset.h
@@ -49,6 +49,14 @@ class RangeSet {
   // bounds. For example, "3,5" contains blocks 3 and 4. So "3,5" and "5,7" are not overlapped.
   bool Overlaps(const RangeSet& other) const;
 
+  // Returns a vector of RangeSets that contain the same set of blocks represented by the current
+  // RangeSet. The RangeSets in the vector contain similar number of blocks, with a maximum delta
+  // of 1-block between any two of them. For example, 14 blocks would be split into 4 + 4 + 3 + 3,
+  // as opposed to 4 + 4 + 4 + 2. If the total number of blocks (T) is less than groups, it
+  // returns a vector of T 1-block RangeSets. Otherwise the number of the returned RangeSets must
+  // equal to groups. The current RangeSet remains intact after the split.
+  std::vector<RangeSet> Split(size_t groups) const;
+
   // Returns the number of Range's in this RangeSet.
   size_t size() const {
     return ranges_.size();
diff --git a/otautil/rangeset.cpp b/otautil/rangeset.cpp
index 532cba4a8..96955b9d0 100644
--- a/otautil/rangeset.cpp
+++ b/otautil/rangeset.cpp
@@ -103,6 +103,46 @@ void RangeSet::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 "";