diff --git a/payload_consumer/bzip_extent_writer.cc b/payload_consumer/bzip_extent_writer.cc
index 0fcc8ba..39d9d67 100644
--- a/payload_consumer/bzip_extent_writer.cc
+++ b/payload_consumer/bzip_extent_writer.cc
@@ -16,7 +16,7 @@
 
 #include "update_engine/payload_consumer/bzip_extent_writer.h"
 
-using std::vector;
+using google::protobuf::RepeatedPtrField;
 
 namespace chromeos_update_engine {
 
@@ -25,7 +25,7 @@
 }
 
 bool BzipExtentWriter::Init(FileDescriptorPtr fd,
-                            const vector<Extent>& extents,
+                            const RepeatedPtrField<Extent>& extents,
                             uint32_t block_size) {
   // Init bzip2 stream
   int rc = BZ2_bzDecompressInit(&stream_,
diff --git a/payload_consumer/bzip_extent_writer.h b/payload_consumer/bzip_extent_writer.h
index 0ad542e..86b346a 100644
--- a/payload_consumer/bzip_extent_writer.h
+++ b/payload_consumer/bzip_extent_writer.h
@@ -19,7 +19,7 @@
 
 #include <bzlib.h>
 #include <memory>
-#include <vector>
+#include <utility>
 
 #include <brillo/secure_blob.h>
 
@@ -41,7 +41,7 @@
   ~BzipExtentWriter() override = default;
 
   bool Init(FileDescriptorPtr fd,
-            const std::vector<Extent>& extents,
+            const google::protobuf::RepeatedPtrField<Extent>& extents,
             uint32_t block_size) override;
   bool Write(const void* bytes, size_t count) override;
   bool EndImpl() override;
diff --git a/payload_consumer/bzip_extent_writer_unittest.cc b/payload_consumer/bzip_extent_writer_unittest.cc
index 6b5e1c0..c0efd63 100644
--- a/payload_consumer/bzip_extent_writer_unittest.cc
+++ b/payload_consumer/bzip_extent_writer_unittest.cc
@@ -27,7 +27,9 @@
 
 #include "update_engine/common/test_utils.h"
 #include "update_engine/common/utils.h"
+#include "update_engine/payload_generator/extent_ranges.h"
 
+using google::protobuf::RepeatedPtrField;
 using std::min;
 using std::string;
 using std::vector;
@@ -55,11 +57,7 @@
 };
 
 TEST_F(BzipExtentWriterTest, SimpleTest) {
-  vector<Extent> extents;
-  Extent extent;
-  extent.set_start_block(0);
-  extent.set_num_blocks(1);
-  extents.push_back(extent);
+  vector<Extent> extents = {ExtentForRange(0, 1)};
 
   // 'echo test | bzip2 | hexdump' yields:
   static const char test_uncompressed[] = "test\n";
@@ -71,7 +69,8 @@
   };
 
   BzipExtentWriter bzip_writer(base::MakeUnique<DirectExtentWriter>());
-  EXPECT_TRUE(bzip_writer.Init(fd_, extents, kBlockSize));
+  EXPECT_TRUE(
+      bzip_writer.Init(fd_, {extents.begin(), extents.end()}, kBlockSize));
   EXPECT_TRUE(bzip_writer.Write(test, sizeof(test)));
   EXPECT_TRUE(bzip_writer.End());
 
@@ -101,14 +100,12 @@
   for (size_t i = 0; i < decompressed_data.size(); ++i)
     decompressed_data[i] = static_cast<uint8_t>("ABC\n"[i % 4]);
 
-  vector<Extent> extents;
-  Extent extent;
-  extent.set_start_block(0);
-  extent.set_num_blocks((kDecompressedLength + kBlockSize - 1) / kBlockSize);
-  extents.push_back(extent);
+  vector<Extent> extents = {
+      ExtentForRange(0, (kDecompressedLength + kBlockSize - 1) / kBlockSize)};
 
   BzipExtentWriter bzip_writer(base::MakeUnique<DirectExtentWriter>());
-  EXPECT_TRUE(bzip_writer.Init(fd_, extents, kBlockSize));
+  EXPECT_TRUE(
+      bzip_writer.Init(fd_, {extents.begin(), extents.end()}, kBlockSize));
 
   brillo::Blob original_compressed_data = compressed_data;
   for (brillo::Blob::size_type i = 0; i < compressed_data.size();
diff --git a/payload_consumer/delta_performer.cc b/payload_consumer/delta_performer.cc
index 9643df3..9299dcd 100644
--- a/payload_consumer/delta_performer.cc
+++ b/payload_consumer/delta_performer.cc
@@ -946,13 +946,8 @@
     writer.reset(new XzExtentWriter(std::move(writer)));
   }
 
-  // Create a vector of extents to pass to the ExtentWriter.
-  vector<Extent> extents;
-  for (int i = 0; i < operation.dst_extents_size(); i++) {
-    extents.push_back(operation.dst_extents(i));
-  }
-
-  TEST_AND_RETURN_FALSE(writer->Init(target_fd_, extents, block_size_));
+  TEST_AND_RETURN_FALSE(
+      writer->Init(target_fd_, operation.dst_extents(), block_size_));
   TEST_AND_RETURN_FALSE(writer->Write(buffer_.data(), operation.data_length()));
   TEST_AND_RETURN_FALSE(writer->End());
 
diff --git a/payload_consumer/download_action.cc b/payload_consumer/download_action.cc
index 43812d7..cf550f5 100644
--- a/payload_consumer/download_action.cc
+++ b/payload_consumer/download_action.cc
@@ -20,7 +20,6 @@
 
 #include <algorithm>
 #include <string>
-#include <vector>
 
 #include <base/files/file_path.h>
 #include <base/metrics/statistics_recorder.h>
@@ -36,7 +35,6 @@
 
 using base::FilePath;
 using std::string;
-using std::vector;
 
 namespace chromeos_update_engine {
 
diff --git a/payload_consumer/download_action_unittest.cc b/payload_consumer/download_action_unittest.cc
index ae85cb5..9d74116 100644
--- a/payload_consumer/download_action_unittest.cc
+++ b/payload_consumer/download_action_unittest.cc
@@ -22,7 +22,6 @@
 #include <memory>
 #include <string>
 #include <utility>
-#include <vector>
 
 #include <base/bind.h>
 #include <base/files/file_path.h>
@@ -51,7 +50,6 @@
 using base::WriteFile;
 using std::string;
 using std::unique_ptr;
-using std::vector;
 using test_utils::ScopedTempFile;
 using testing::AtLeast;
 using testing::InSequence;
diff --git a/payload_consumer/extent_writer.cc b/payload_consumer/extent_writer.cc
index 5501e22..c5776ec 100644
--- a/payload_consumer/extent_writer.cc
+++ b/payload_consumer/extent_writer.cc
@@ -34,21 +34,19 @@
     return true;
   const char* c_bytes = reinterpret_cast<const char*>(bytes);
   size_t bytes_written = 0;
-  while (count - bytes_written > 0) {
-    TEST_AND_RETURN_FALSE(next_extent_index_ < extents_.size());
-    uint64_t bytes_remaining_next_extent =
-        extents_[next_extent_index_].num_blocks() * block_size_ -
-        extent_bytes_written_;
-    CHECK_NE(bytes_remaining_next_extent, static_cast<uint64_t>(0));
+  while (bytes_written < count) {
+    TEST_AND_RETURN_FALSE(cur_extent_ != extents_.end());
+    uint64_t bytes_remaining_cur_extent =
+        cur_extent_->num_blocks() * block_size_ - extent_bytes_written_;
+    CHECK_NE(bytes_remaining_cur_extent, static_cast<uint64_t>(0));
     size_t bytes_to_write =
         static_cast<size_t>(min(static_cast<uint64_t>(count - bytes_written),
-                                bytes_remaining_next_extent));
+                                bytes_remaining_cur_extent));
     TEST_AND_RETURN_FALSE(bytes_to_write > 0);
 
-    if (extents_[next_extent_index_].start_block() != kSparseHole) {
+    if (cur_extent_->start_block() != kSparseHole) {
       const off64_t offset =
-          extents_[next_extent_index_].start_block() * block_size_ +
-          extent_bytes_written_;
+          cur_extent_->start_block() * block_size_ + extent_bytes_written_;
       TEST_AND_RETURN_FALSE_ERRNO(fd_->Seek(offset, SEEK_SET) !=
                                   static_cast<off64_t>(-1));
       TEST_AND_RETURN_FALSE(
@@ -56,13 +54,12 @@
     }
     bytes_written += bytes_to_write;
     extent_bytes_written_ += bytes_to_write;
-    if (bytes_remaining_next_extent == bytes_to_write) {
+    if (bytes_remaining_cur_extent == bytes_to_write) {
       // We filled this extent
-      CHECK_EQ(extent_bytes_written_,
-               extents_[next_extent_index_].num_blocks() * block_size_);
+      CHECK_EQ(extent_bytes_written_, cur_extent_->num_blocks() * block_size_);
       // move to next extent
       extent_bytes_written_ = 0;
-      next_extent_index_++;
+      cur_extent_++;
     }
   }
   return true;
diff --git a/payload_consumer/extent_writer.h b/payload_consumer/extent_writer.h
index 6484ebf..2c15861 100644
--- a/payload_consumer/extent_writer.h
+++ b/payload_consumer/extent_writer.h
@@ -17,7 +17,8 @@
 #ifndef UPDATE_ENGINE_PAYLOAD_CONSUMER_EXTENT_WRITER_H_
 #define UPDATE_ENGINE_PAYLOAD_CONSUMER_EXTENT_WRITER_H_
 
-#include <vector>
+#include <memory>
+#include <utility>
 
 #include <base/logging.h>
 #include <brillo/secure_blob.h>
@@ -40,7 +41,7 @@
 
   // Returns true on success.
   virtual bool Init(FileDescriptorPtr fd,
-                    const std::vector<Extent>& extents,
+                    const google::protobuf::RepeatedPtrField<Extent>& extents,
                     uint32_t block_size) = 0;
 
   // Returns true on success.
@@ -66,11 +67,12 @@
   ~DirectExtentWriter() override = default;
 
   bool Init(FileDescriptorPtr fd,
-            const std::vector<Extent>& extents,
+            const google::protobuf::RepeatedPtrField<Extent>& extents,
             uint32_t block_size) override {
     fd_ = fd;
     block_size_ = block_size;
     extents_ = extents;
+    cur_extent_ = extents_.begin();
     return true;
   }
   bool Write(const void* bytes, size_t count) override;
@@ -80,11 +82,11 @@
   FileDescriptorPtr fd_{nullptr};
 
   size_t block_size_{0};
-  // Bytes written into next_extent_index_ thus far
+  // Bytes written into |cur_extent_| thus far.
   uint64_t extent_bytes_written_{0};
-  std::vector<Extent> extents_;
-  // The next call to write should correspond to extents_[next_extent_index_]
-  std::vector<Extent>::size_type next_extent_index_{0};
+  google::protobuf::RepeatedPtrField<Extent> extents_;
+  // The next call to write should correspond to |cur_extents_|.
+  google::protobuf::RepeatedPtrField<Extent>::iterator cur_extent_;
 };
 
 // Takes an underlying ExtentWriter to which all operations are delegated.
@@ -100,7 +102,7 @@
   ~ZeroPadExtentWriter() override = default;
 
   bool Init(FileDescriptorPtr fd,
-            const std::vector<Extent>& extents,
+            const google::protobuf::RepeatedPtrField<Extent>& extents,
             uint32_t block_size) override {
     block_size_ = block_size;
     return underlying_extent_writer_->Init(fd, extents, block_size);
diff --git a/payload_consumer/extent_writer_unittest.cc b/payload_consumer/extent_writer_unittest.cc
index f9304a3..1f5fbaa 100644
--- a/payload_consumer/extent_writer_unittest.cc
+++ b/payload_consumer/extent_writer_unittest.cc
@@ -29,6 +29,7 @@
 #include "update_engine/common/test_utils.h"
 #include "update_engine/common/utils.h"
 #include "update_engine/payload_consumer/payload_constants.h"
+#include "update_engine/payload_generator/extent_ranges.h"
 
 using chromeos_update_engine::test_utils::ExpectVectorsEq;
 using std::min;
@@ -65,16 +66,11 @@
 };
 
 TEST_F(ExtentWriterTest, SimpleTest) {
-  vector<Extent> extents;
-  Extent extent;
-  extent.set_start_block(1);
-  extent.set_num_blocks(1);
-  extents.push_back(extent);
-
+  vector<Extent> extents = {ExtentForRange(1, 1)};
   const string bytes = "1234";
-
   DirectExtentWriter direct_writer;
-  EXPECT_TRUE(direct_writer.Init(fd_, extents, kBlockSize));
+  EXPECT_TRUE(
+      direct_writer.Init(fd_, {extents.begin(), extents.end()}, kBlockSize));
   EXPECT_TRUE(direct_writer.Write(bytes.data(), bytes.size()));
   EXPECT_TRUE(direct_writer.End());
 
@@ -91,14 +87,10 @@
 }
 
 TEST_F(ExtentWriterTest, ZeroLengthTest) {
-  vector<Extent> extents;
-  Extent extent;
-  extent.set_start_block(1);
-  extent.set_num_blocks(1);
-  extents.push_back(extent);
-
+  vector<Extent> extents = {ExtentForRange(1, 1)};
   DirectExtentWriter direct_writer;
-  EXPECT_TRUE(direct_writer.Init(fd_, extents, kBlockSize));
+  EXPECT_TRUE(
+      direct_writer.Init(fd_, {extents.begin(), extents.end()}, kBlockSize));
   EXPECT_TRUE(direct_writer.Write(nullptr, 0));
   EXPECT_TRUE(direct_writer.End());
 }
@@ -117,23 +109,14 @@
 
 void ExtentWriterTest::WriteAlignedExtents(size_t chunk_size,
                                            size_t first_chunk_size) {
-  vector<Extent> extents;
-  Extent extent;
-  extent.set_start_block(1);
-  extent.set_num_blocks(1);
-  extents.push_back(extent);
-  extent.set_start_block(0);
-  extent.set_num_blocks(1);
-  extents.push_back(extent);
-  extent.set_start_block(2);
-  extent.set_num_blocks(1);
-  extents.push_back(extent);
-
+  vector<Extent> extents = {
+      ExtentForRange(1, 1), ExtentForRange(0, 1), ExtentForRange(2, 1)};
   brillo::Blob data(kBlockSize * 3);
   test_utils::FillWithData(&data);
 
   DirectExtentWriter direct_writer;
-  EXPECT_TRUE(direct_writer.Init(fd_, extents, kBlockSize));
+  EXPECT_TRUE(
+      direct_writer.Init(fd_, {extents.begin(), extents.end()}, kBlockSize));
 
   size_t bytes_written = 0;
   while (bytes_written < data.size()) {
@@ -172,21 +155,14 @@
 }
 
 void ExtentWriterTest::TestZeroPad(bool aligned_size) {
-  vector<Extent> extents;
-  Extent extent;
-  extent.set_start_block(1);
-  extent.set_num_blocks(1);
-  extents.push_back(extent);
-  extent.set_start_block(0);
-  extent.set_num_blocks(1);
-  extents.push_back(extent);
-
+  vector<Extent> extents = {ExtentForRange(1, 1), ExtentForRange(0, 1)};
   brillo::Blob data(kBlockSize * 2);
   test_utils::FillWithData(&data);
 
   ZeroPadExtentWriter zero_pad_writer(base::MakeUnique<DirectExtentWriter>());
 
-  EXPECT_TRUE(zero_pad_writer.Init(fd_, extents, kBlockSize));
+  EXPECT_TRUE(
+      zero_pad_writer.Init(fd_, {extents.begin(), extents.end()}, kBlockSize));
   size_t bytes_to_write = data.size();
   const size_t missing_bytes = (aligned_size ? 0 : 9);
   bytes_to_write -= missing_bytes;
@@ -215,17 +191,9 @@
 }
 
 TEST_F(ExtentWriterTest, SparseFileTest) {
-  vector<Extent> extents;
-  Extent extent;
-  extent.set_start_block(1);
-  extent.set_num_blocks(1);
-  extents.push_back(extent);
-  extent.set_start_block(kSparseHole);
-  extent.set_num_blocks(2);
-  extents.push_back(extent);
-  extent.set_start_block(0);
-  extent.set_num_blocks(1);
-  extents.push_back(extent);
+  vector<Extent> extents = {ExtentForRange(1, 1),
+                            ExtentForRange(kSparseHole, 2),
+                            ExtentForRange(0, 1)};
   const int block_count = 4;
   const int on_disk_count = 2;
 
@@ -233,7 +201,8 @@
   test_utils::FillWithData(&data);
 
   DirectExtentWriter direct_writer;
-  EXPECT_TRUE(direct_writer.Init(fd_, extents, kBlockSize));
+  EXPECT_TRUE(
+      direct_writer.Init(fd_, {extents.begin(), extents.end()}, kBlockSize));
 
   size_t bytes_written = 0;
   while (bytes_written < (block_count * kBlockSize)) {
diff --git a/payload_consumer/fake_extent_writer.h b/payload_consumer/fake_extent_writer.h
index 762c6d5..4418a9e 100644
--- a/payload_consumer/fake_extent_writer.h
+++ b/payload_consumer/fake_extent_writer.h
@@ -18,7 +18,6 @@
 #define UPDATE_ENGINE_PAYLOAD_CONSUMER_FAKE_EXTENT_WRITER_H_
 
 #include <memory>
-#include <vector>
 
 #include <brillo/secure_blob.h>
 
@@ -35,7 +34,7 @@
 
   // ExtentWriter overrides.
   bool Init(FileDescriptorPtr /* fd */,
-            const std::vector<Extent>& /* extents */,
+            const google::protobuf::RepeatedPtrField<Extent>& /* extents */,
             uint32_t /* block_size */) override {
     init_called_ = true;
     return true;
diff --git a/payload_consumer/file_descriptor_utils.cc b/payload_consumer/file_descriptor_utils.cc
index f7f61a5..b092149 100644
--- a/payload_consumer/file_descriptor_utils.cc
+++ b/payload_consumer/file_descriptor_utils.cc
@@ -66,12 +66,7 @@
   brillo::Blob buf(buffer_blocks * block_size);
 
   DirectExtentWriter writer;
-  std::vector<Extent> vec_tgt_extents;
-  vec_tgt_extents.reserve(tgt_extents.size());
-  for (const auto& ext : tgt_extents) {
-    vec_tgt_extents.push_back(ext);
-  }
-  TEST_AND_RETURN_FALSE(writer.Init(target, vec_tgt_extents, block_size));
+  TEST_AND_RETURN_FALSE(writer.Init(target, tgt_extents, block_size));
 
   for (const Extent& src_ext : src_extents) {
     for (uint64_t src_ext_block = 0; src_ext_block < src_ext.num_blocks();
diff --git a/payload_consumer/file_descriptor_utils.h b/payload_consumer/file_descriptor_utils.h
index 6b2fd39..d1289d6 100644
--- a/payload_consumer/file_descriptor_utils.h
+++ b/payload_consumer/file_descriptor_utils.h
@@ -17,8 +17,6 @@
 #ifndef UPDATE_ENGINE_PAYLOAD_CONSUMER_FILE_DESCRIPTOR_UTILS_H_
 #define UPDATE_ENGINE_PAYLOAD_CONSUMER_FILE_DESCRIPTOR_UTILS_H_
 
-#include <vector>
-
 #include <brillo/secure_blob.h>
 
 #include "update_engine/payload_consumer/file_descriptor.h"
diff --git a/payload_consumer/file_writer_unittest.cc b/payload_consumer/file_writer_unittest.cc
index debb4c3..92837c8 100644
--- a/payload_consumer/file_writer_unittest.cc
+++ b/payload_consumer/file_writer_unittest.cc
@@ -21,7 +21,6 @@
 #include <unistd.h>
 
 #include <string>
-#include <vector>
 
 #include <brillo/secure_blob.h>
 #include <gtest/gtest.h>
@@ -30,7 +29,6 @@
 #include "update_engine/common/utils.h"
 
 using std::string;
-using std::vector;
 
 namespace chromeos_update_engine {
 
diff --git a/payload_consumer/mtd_file_descriptor.cc b/payload_consumer/mtd_file_descriptor.cc
index 3f0a33f..5d7758a 100644
--- a/payload_consumer/mtd_file_descriptor.cc
+++ b/payload_consumer/mtd_file_descriptor.cc
@@ -18,11 +18,12 @@
 
 #include <fcntl.h>
 #include <mtd/ubi-user.h>
-#include <string>
 #include <sys/ioctl.h>
 #include <sys/stat.h>
 #include <sys/types.h>
-#include <vector>
+
+#include <memory>
+#include <string>
 
 #include <base/files/file_path.h>
 #include <base/strings/string_number_conversions.h>
@@ -33,7 +34,6 @@
 #include "update_engine/common/utils.h"
 
 using std::string;
-using std::vector;
 
 namespace {
 
diff --git a/payload_consumer/payload_verifier.h b/payload_consumer/payload_verifier.h
index 22ced40..8caef35 100644
--- a/payload_consumer/payload_verifier.h
+++ b/payload_consumer/payload_verifier.h
@@ -18,7 +18,6 @@
 #define UPDATE_ENGINE_PAYLOAD_CONSUMER_PAYLOAD_VERIFIER_H_
 
 #include <string>
-#include <vector>
 
 #include <base/macros.h>
 #include <brillo/secure_blob.h>
diff --git a/payload_consumer/postinstall_runner_action_unittest.cc b/payload_consumer/postinstall_runner_action_unittest.cc
index e82a866..a319299 100644
--- a/payload_consumer/postinstall_runner_action_unittest.cc
+++ b/payload_consumer/postinstall_runner_action_unittest.cc
@@ -22,7 +22,6 @@
 
 #include <memory>
 #include <string>
-#include <vector>
 
 #include <base/bind.h>
 #include <base/files/file_util.h>
@@ -44,7 +43,6 @@
 using brillo::MessageLoop;
 using chromeos_update_engine::test_utils::ScopedLoopbackDeviceBinder;
 using std::string;
-using std::vector;
 
 namespace chromeos_update_engine {
 
diff --git a/payload_consumer/xz_extent_writer.cc b/payload_consumer/xz_extent_writer.cc
index 4bd893d..343ed80 100644
--- a/payload_consumer/xz_extent_writer.cc
+++ b/payload_consumer/xz_extent_writer.cc
@@ -16,7 +16,7 @@
 
 #include "update_engine/payload_consumer/xz_extent_writer.h"
 
-using std::vector;
+using google::protobuf::RepeatedPtrField;
 
 namespace chromeos_update_engine {
 
@@ -47,7 +47,7 @@
       return "<unknown xz error>";
   }
   #undef __XZ_ERROR_STRING_CASE
-};
+}
 }  // namespace
 
 XzExtentWriter::~XzExtentWriter() {
@@ -55,7 +55,7 @@
 }
 
 bool XzExtentWriter::Init(FileDescriptorPtr fd,
-                          const vector<Extent>& extents,
+                          const RepeatedPtrField<Extent>& extents,
                           uint32_t block_size) {
   stream_ = xz_dec_init(XZ_DYNALLOC, kXzMaxDictSize);
   TEST_AND_RETURN_FALSE(stream_ != nullptr);
diff --git a/payload_consumer/xz_extent_writer.h b/payload_consumer/xz_extent_writer.h
index a6b3257..5e50256 100644
--- a/payload_consumer/xz_extent_writer.h
+++ b/payload_consumer/xz_extent_writer.h
@@ -20,7 +20,7 @@
 #include <xz.h>
 
 #include <memory>
-#include <vector>
+#include <utility>
 
 #include <brillo/secure_blob.h>
 
@@ -40,7 +40,7 @@
   ~XzExtentWriter() override;
 
   bool Init(FileDescriptorPtr fd,
-            const std::vector<Extent>& extents,
+            const google::protobuf::RepeatedPtrField<Extent>& extents,
             uint32_t block_size) override;
   bool Write(const void* bytes, size_t count) override;
   bool EndImpl() override;
diff --git a/payload_consumer/xz_extent_writer_unittest.cc b/payload_consumer/xz_extent_writer_unittest.cc
index 47c0a58..c8bcdf9 100644
--- a/payload_consumer/xz_extent_writer_unittest.cc
+++ b/payload_consumer/xz_extent_writer_unittest.cc
@@ -22,8 +22,6 @@
 #include <unistd.h>
 
 #include <algorithm>
-#include <string>
-#include <vector>
 
 #include <base/memory/ptr_util.h>
 #include <gtest/gtest.h>
@@ -32,9 +30,6 @@
 #include "update_engine/common/utils.h"
 #include "update_engine/payload_consumer/fake_extent_writer.h"
 
-using std::string;
-using std::vector;
-
 namespace chromeos_update_engine {
 
 namespace {