diff --git a/payload_generator/extent_ranges.cc b/payload_generator/extent_ranges.cc
index 2098639..4cc2d6f 100644
--- a/payload_generator/extent_ranges.cc
+++ b/payload_generator/extent_ranges.cc
@@ -45,7 +45,7 @@
 
 bool ExtentRanges::ExtentsOverlap(const Extent& a, const Extent& b) {
   if (a.start_block() == b.start_block())
-    return true;
+    return a.num_blocks() != 0;
   if (a.start_block() == kSparseHole || b.start_block() == kSparseHole)
     return false;
   if (a.start_block() < b.start_block()) {
@@ -281,6 +281,31 @@
   return out;
 }
 
+Range<ExtentRanges::ExtentSet::const_iterator> ExtentRanges::GetCandidateRange(
+    const Extent& extent) const {
+  auto lower_it = extent_set_.lower_bound(extent);
+  if (lower_it != extent_set_.begin()) {
+    --lower_it;
+  }
+
+  const auto upper_it = extent_set_.upper_bound(
+      ExtentForRange(extent.start_block() + extent.num_blocks(), 1));
+  return {lower_it, upper_it};
+}
+
+std::vector<Extent> ExtentRanges::GetIntersectingExtents(
+    const Extent& extent) const {
+  const auto candidates = GetCandidateRange(extent);
+  std::vector<Extent> result;
+  for (const auto& ext : candidates) {
+    if (auto intersection = GetOverlapExtent(ext, extent);
+        intersection.num_blocks() != 0) {
+      result.emplace_back(std::move(intersection));
+    }
+  }
+  return result;
+}
+
 vector<Extent> FilterExtentRanges(const vector<Extent>& extents,
                                   const ExtentRanges& ranges) {
   vector<Extent> result;
@@ -331,4 +356,15 @@
   return result;
 }
 
+Extent GetOverlapExtent(const Extent& extent1, const Extent& extent2) {
+  if (!ExtentRanges::ExtentsOverlap(extent1, extent2)) {
+    return {};
+  }
+  const auto start_block =
+      std::max(extent1.start_block(), extent2.start_block());
+  const auto end_block = std::min(extent1.start_block() + extent1.num_blocks(),
+                                  extent2.start_block() + extent2.num_blocks());
+  return ExtentForRange(start_block, end_block - start_block);
+}
+
 }  // namespace chromeos_update_engine
diff --git a/payload_generator/extent_ranges.h b/payload_generator/extent_ranges.h
index 68aa27f..4894831 100644
--- a/payload_generator/extent_ranges.h
+++ b/payload_generator/extent_ranges.h
@@ -23,6 +23,7 @@
 
 #include <base/macros.h>
 
+#include "update_engine/common/utils.h"
 #include "update_engine/update_metadata.pb.h"
 
 // An ExtentRanges object represents an unordered collection of extents (and
@@ -84,6 +85,18 @@
   // the number of blocks in this extent set.
   std::vector<Extent> GetExtentsForBlockCount(uint64_t count) const;
 
+  // Compute the intersection between this ExtentRange and the |extent|
+  // parameter. Return results in a vector. If there's no intersection, an empty
+  // vector is returned.
+  std::vector<Extent> GetIntersectingExtents(const Extent& extent) const;
+
+  // Get a range of extents that possibly intersect with |extent|. (Returned
+  // extents do not necessarily intersect!). It is perfectly acceptable to just
+  // return all extents in this set, though more efficient solution using binary
+  // search is preferred.
+  Range<ExtentSet::const_iterator> GetCandidateRange(
+      const Extent& extent) const;
+
  private:
   ExtentSet extent_set_;
   uint64_t blocks_;
@@ -95,6 +108,8 @@
 std::vector<Extent> FilterExtentRanges(const std::vector<Extent>& extents,
                                        const ExtentRanges& ranges);
 
+Extent GetOverlapExtent(const Extent& extent1, const Extent& extent2);
+
 }  // namespace chromeos_update_engine
 
 #endif  // UPDATE_ENGINE_PAYLOAD_GENERATOR_EXTENT_RANGES_H_
diff --git a/payload_generator/extent_ranges_unittest.cc b/payload_generator/extent_ranges_unittest.cc
index f55bb73..314ec54 100644
--- a/payload_generator/extent_ranges_unittest.cc
+++ b/payload_generator/extent_ranges_unittest.cc
@@ -315,4 +315,20 @@
                 ranges));
 }
 
+TEST(ExtentRangesTest, GetOverlapExtent) {
+  const auto ret1 =
+      GetOverlapExtent(ExtentForRange(5, 5), ExtentForRange(10, 10));
+  ASSERT_EQ(ret1.num_blocks(), 0UL) << ret1;
+  const auto ret2 =
+      GetOverlapExtent(ExtentForRange(5, 5), ExtentForRange(9, 10));
+  ASSERT_EQ(ret2, ExtentForRange(9, 1));
+
+  const auto ret3 =
+      GetOverlapExtent(ExtentForRange(7, 5), ExtentForRange(3, 10));
+  ASSERT_EQ(ret3, ExtentForRange(7, 5));
+  const auto ret4 =
+      GetOverlapExtent(ExtentForRange(7, 5), ExtentForRange(3, 3));
+  ASSERT_EQ(ret4.num_blocks(), 0UL);
+}
+
 }  // namespace chromeos_update_engine