diff --git a/otautil/Android.bp b/otautil/Android.bp
index 659fefa..5efb12d 100644
--- a/otautil/Android.bp
+++ b/otautil/Android.bp
@@ -21,6 +21,7 @@
         "SysUtil.cpp",
         "DirUtil.cpp",
         "ThermalUtil.cpp",
+        "rangeset.cpp",
     ],
 
     static_libs: [
diff --git a/otautil/include/otautil/rangeset.h b/otautil/include/otautil/rangeset.h
index f224a08..c4234d1 100644
--- a/otautil/include/otautil/rangeset.h
+++ b/otautil/include/otautil/rangeset.h
@@ -22,103 +22,24 @@
 #include <utility>
 #include <vector>
 
-#include <android-base/logging.h>
-#include <android-base/parseint.h>
-#include <android-base/stringprintf.h>
-#include <android-base/strings.h>
-
 using Range = std::pair<size_t, size_t>;
 
 class RangeSet {
  public:
   RangeSet() : blocks_(0) {}
 
-  explicit RangeSet(std::vector<Range>&& pairs) {
-    CHECK_NE(pairs.size(), static_cast<size_t>(0)) << "Invalid number of tokens";
+  explicit RangeSet(std::vector<Range>&& pairs);
 
-    // Sanity check the input.
-    size_t result = 0;
-    for (const auto& range : pairs) {
-      CHECK_LT(range.first, range.second)
-          << "Empty or negative range: " << range.first << ", " << range.second;
-      size_t sz = range.second - range.first;
-      CHECK_LE(result, SIZE_MAX - sz) << "RangeSet size overflow";
-      result += sz;
-    }
+  static RangeSet Parse(const std::string& range_text);
 
-    ranges_ = pairs;
-    blocks_ = result;
-  }
-
-  static RangeSet Parse(const std::string& range_text) {
-    std::vector<std::string> pieces = android::base::Split(range_text, ",");
-    CHECK_GE(pieces.size(), static_cast<size_t>(3)) << "Invalid range text: " << range_text;
-
-    size_t num;
-    CHECK(android::base::ParseUint(pieces[0], &num, static_cast<size_t>(INT_MAX)))
-        << "Failed to parse the number of tokens: " << range_text;
-
-    CHECK_NE(num, static_cast<size_t>(0)) << "Invalid number of tokens: " << range_text;
-    CHECK_EQ(num % 2, static_cast<size_t>(0)) << "Number of tokens must be even: " << range_text;
-    CHECK_EQ(num, pieces.size() - 1) << "Mismatching number of tokens: " << range_text;
-
-    std::vector<Range> pairs;
-    for (size_t i = 0; i < num; i += 2) {
-      size_t first;
-      CHECK(android::base::ParseUint(pieces[i + 1], &first, static_cast<size_t>(INT_MAX)));
-      size_t second;
-      CHECK(android::base::ParseUint(pieces[i + 2], &second, static_cast<size_t>(INT_MAX)));
-
-      pairs.emplace_back(first, second);
-    }
-
-    return RangeSet(std::move(pairs));
-  }
-
-  std::string 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;
-  }
+  std::string ToString() const;
 
   // Get the block number for the i-th (starting from 0) block in the RangeSet.
-  size_t 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.
-  }
+  size_t GetBlockNumber(size_t idx) const;
 
   // 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 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;
-  }
+  bool Overlaps(const RangeSet& other) const;
 
   // size() gives the number of Range's in this RangeSet.
   size_t size() const {
@@ -176,8 +97,6 @@
   size_t blocks_;
 };
 
-static constexpr size_t kBlockSize = 4096;
-
 // The class is a sorted version of a RangeSet; and it's useful in imgdiff to split the input
 // files when we're handling large zip files. Specifically, we can treat the input file as a
 // continuous RangeSet (i.e. RangeSet("0-99") for a 100 blocks file); and break it down into
@@ -193,57 +112,21 @@
   SortedRangeSet() {}
 
   // Ranges in the the set should be mutually exclusive; and they're sorted by the start block.
-  explicit SortedRangeSet(std::vector<Range>&& pairs) : RangeSet(std::move(pairs)) {
-    std::sort(ranges_.begin(), ranges_.end());
-  }
+  explicit SortedRangeSet(std::vector<Range>&& pairs);
 
-  void Insert(const Range& to_insert) {
-    SortedRangeSet rs({ to_insert });
-    Insert(rs);
-  }
+  void Insert(const Range& to_insert);
 
   // Insert the input SortedRangeSet; keep the ranges sorted and merge the overlap ranges.
-  void 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);
-  }
-
-  void Clear() {
-    blocks_ = 0;
-    ranges_.clear();
-  }
-
-  using RangeSet::Overlaps;
-  bool Overlaps(size_t start, size_t len) const {
-    RangeSet rs({ { start / kBlockSize, (start + len - 1) / kBlockSize + 1 } });
-    return Overlaps(rs);
-  }
+  void Insert(const SortedRangeSet& rs);
 
   // Compute the block range the file occupies, and insert that range.
-  void Insert(size_t start, size_t len) {
-    Range to_insert{ start / kBlockSize, (start + len - 1) / kBlockSize + 1 };
-    Insert(to_insert);
-  }
+  void Insert(size_t start, size_t len);
+
+  void Clear();
+
+  using RangeSet::Overlaps;
+
+  bool Overlaps(size_t start, size_t len) const;
 
   // 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
@@ -255,24 +138,5 @@
   // 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 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;
-  }
-};
\ No newline at end of file
+  size_t GetOffsetInRangeSet(size_t old_offset) const;
+};
diff --git a/otautil/rangeset.cpp b/otautil/rangeset.cpp
new file mode 100644
index 0000000..a121a4e
--- /dev/null
+++ b/otautil/rangeset.cpp
@@ -0,0 +1,200 @@
+/*
+ * 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 <stddef.h>
+
+#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) {
+  CHECK_NE(pairs.size(), static_cast<size_t>(0)) << "Invalid number of tokens";
+
+  // Sanity check the input.
+  size_t result = 0;
+  for (const auto& range : pairs) {
+    CHECK_LT(range.first, range.second) << "Empty or negative range: " << range.first << ", "
+                                        << range.second;
+    size_t sz = range.second - range.first;
+    CHECK_LE(result, SIZE_MAX - sz) << "RangeSet size overflow";
+    result += sz;
+  }
+
+  ranges_ = pairs;
+  blocks_ = result;
+}
+
+RangeSet RangeSet::Parse(const std::string& range_text) {
+  std::vector<std::string> pieces = android::base::Split(range_text, ",");
+  CHECK_GE(pieces.size(), static_cast<size_t>(3)) << "Invalid range text: " << range_text;
+
+  size_t num;
+  CHECK(android::base::ParseUint(pieces[0], &num, static_cast<size_t>(INT_MAX)))
+      << "Failed to parse the number of tokens: " << range_text;
+
+  CHECK_NE(num, static_cast<size_t>(0)) << "Invalid number of tokens: " << range_text;
+  CHECK_EQ(num % 2, static_cast<size_t>(0)) << "Number of tokens must be even: " << range_text;
+  CHECK_EQ(num, pieces.size() - 1) << "Mismatching number of tokens: " << range_text;
+
+  std::vector<Range> pairs;
+  for (size_t i = 0; i < num; i += 2) {
+    size_t first;
+    CHECK(android::base::ParseUint(pieces[i + 1], &first, static_cast<size_t>(INT_MAX)));
+    size_t second;
+    CHECK(android::base::ParseUint(pieces[i + 2], &second, static_cast<size_t>(INT_MAX)));
+
+    pairs.emplace_back(first, second);
+  }
+
+  return RangeSet(std::move(pairs));
+}
+
+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;
+}
+
+static constexpr size_t kBlockSize = 4096;
+
+// 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);
+}
+
+void SortedRangeSet::Clear() {
+  blocks_ = 0;
+  ranges_.clear();
+}
+
+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;
+}