5 files changed, 154 insertions, 27 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 "";
diff --git a/tests/unit/rangeset_test.cpp b/tests/unit/rangeset_test.cpp
index 5141bb67f..7ae193e18 100644
--- a/tests/unit/rangeset_test.cpp
+++ b/tests/unit/rangeset_test.cpp
@@ -123,6 +123,86 @@ TEST(RangeSetTest, Overlaps) {
   ASSERT_FALSE(RangeSet::Parse("2,5,7").Overlaps(RangeSet::Parse("2,3,5")));
 }
 
+TEST(RangeSetTest, Split) {
+  RangeSet rs1 = RangeSet::Parse("2,1,2");
+  ASSERT_TRUE(rs1);
+  ASSERT_EQ((std::vector<RangeSet>{ RangeSet::Parse("2,1,2") }), rs1.Split(1));
+
+  RangeSet rs2 = RangeSet::Parse("2,5,10");
+  ASSERT_TRUE(rs2);
+  ASSERT_EQ((std::vector<RangeSet>{ RangeSet::Parse("2,5,8"), RangeSet::Parse("2,8,10") }),
+            rs2.Split(2));
+
+  RangeSet rs3 = RangeSet::Parse("4,0,1,5,10");
+  ASSERT_TRUE(rs3);
+  ASSERT_EQ((std::vector<RangeSet>{ RangeSet::Parse("4,0,1,5,7"), RangeSet::Parse("2,7,10") }),
+            rs3.Split(2));
+
+  RangeSet rs4 = RangeSet::Parse("6,1,3,3,4,4,5");
+  ASSERT_TRUE(rs4);
+  ASSERT_EQ((std::vector<RangeSet>{ RangeSet::Parse("2,1,3"), RangeSet::Parse("2,3,4"),
+                                    RangeSet::Parse("2,4,5") }),
+            rs4.Split(3));
+
+  RangeSet rs5 = RangeSet::Parse("2,0,10");
+  ASSERT_TRUE(rs5);
+  ASSERT_EQ((std::vector<RangeSet>{ RangeSet::Parse("2,0,3"), RangeSet::Parse("2,3,6"),
+                                    RangeSet::Parse("2,6,8"), RangeSet::Parse("2,8,10") }),
+            rs5.Split(4));
+
+  RangeSet rs6 = RangeSet::Parse(
+      "20,0,268,269,271,286,447,8350,32770,33022,98306,98558,163842,164094,196609,204800,229378,"
+      "229630,294914,295166,457564");
+  ASSERT_TRUE(rs6);
+  size_t rs6_blocks = rs6.blocks();
+  auto splits = rs6.Split(4);
+  ASSERT_EQ(
+      (std::vector<RangeSet>{
+          RangeSet::Parse("12,0,268,269,271,286,447,8350,32770,33022,98306,98558,118472"),
+          RangeSet::Parse("8,118472,163842,164094,196609,204800,229378,229630,237216"),
+          RangeSet::Parse("4,237216,294914,295166,347516"), RangeSet::Parse("2,347516,457564") }),
+      splits);
+  size_t sum = 0;
+  for (const auto& element : splits) {
+    sum += element.blocks();
+  }
+  ASSERT_EQ(rs6_blocks, sum);
+}
+
+TEST(RangeSetTest, Split_EdgeCases) {
+  // Empty RangeSet.
+  RangeSet rs1;
+  ASSERT_FALSE(rs1);
+  ASSERT_EQ((std::vector<RangeSet>{}), rs1.Split(2));
+  ASSERT_FALSE(rs1);
+
+  // Zero group.
+  RangeSet rs2 = RangeSet::Parse("2,1,5");
+  ASSERT_TRUE(rs2);
+  ASSERT_EQ((std::vector<RangeSet>{}), rs2.Split(0));
+
+  // The number of blocks equals to the number of groups.
+  RangeSet rs3 = RangeSet::Parse("2,1,5");
+  ASSERT_TRUE(rs3);
+  ASSERT_EQ((std::vector<RangeSet>{ RangeSet::Parse("2,1,2"), RangeSet::Parse("2,2,3"),
+                                    RangeSet::Parse("2,3,4"), RangeSet::Parse("2,4,5") }),
+            rs3.Split(4));
+
+  // Less blocks than the number of groups.
+  RangeSet rs4 = RangeSet::Parse("2,1,5");
+  ASSERT_TRUE(rs4);
+  ASSERT_EQ((std::vector<RangeSet>{ RangeSet::Parse("2,1,2"), RangeSet::Parse("2,2,3"),
+                                    RangeSet::Parse("2,3,4"), RangeSet::Parse("2,4,5") }),
+            rs4.Split(8));
+
+  // Less blocks than the number of groups.
+  RangeSet rs5 = RangeSet::Parse("2,0,3");
+  ASSERT_TRUE(rs5);
+  ASSERT_EQ((std::vector<RangeSet>{ RangeSet::Parse("2,0,1"), RangeSet::Parse("2,1,2"),
+                                    RangeSet::Parse("2,2,3") }),
+            rs5.Split(4));
+}
+
 TEST(RangeSetTest, GetBlockNumber) {
   RangeSet rs = RangeSet::Parse("2,1,10");
   ASSERT_EQ(static_cast<size_t>(1), rs.GetBlockNumber(0));
diff --git a/update_verifier/Android.mk b/update_verifier/Android.mk
index 33c5fe9e7..0ff88546f 100644
--- a/update_verifier/Android.mk
+++ b/update_verifier/Android.mk
@@ -22,6 +22,10 @@ LOCAL_SRC_FILES := \
     update_verifier.cpp
 
 LOCAL_MODULE := libupdate_verifier
+
+LOCAL_STATIC_LIBRARIES := \
+    libotautil
+
 LOCAL_SHARED_LIBRARIES := \
     libbase \
     libcutils \
@@ -54,7 +58,9 @@ LOCAL_SRC_FILES := \
 
 LOCAL_MODULE := update_verifier
 LOCAL_STATIC_LIBRARIES := \
-    libupdate_verifier
+    libupdate_verifier \
+    libotautil
+
 LOCAL_SHARED_LIBRARIES := \
     libbase \
     libcutils \
diff --git a/update_verifier/update_verifier.cpp b/update_verifier/update_verifier.cpp
index ba7b7aec4..c5e154f03 100644
--- a/update_verifier/update_verifier.cpp
+++ b/update_verifier/update_verifier.cpp
@@ -58,6 +58,8 @@
 #include <android/hardware/boot/1.0/IBootControl.h>
 #include <cutils/android_reboot.h>
 
+#include "otautil/rangeset.h"
+
 using android::sp;
 using android::hardware::boot::V1_0::IBootControl;
 using android::hardware::boot::V1_0::BoolResult;
@@ -129,42 +131,33 @@ static bool read_blocks(const std::string& partition, const std::string& range_s
   // followed by 'count' number comma separated integers. Every two integers reprensent a
   // block range with the first number included in range but second number not included.
   // For example '4,64536,65343,74149,74150' represents: [64536,65343) and [74149,74150).
-  std::vector<std::string> ranges = android::base::Split(range_str, ",");
-  size_t range_count;
-  bool status = android::base::ParseUint(ranges[0], &range_count);
-  if (!status || (range_count == 0) || (range_count % 2 != 0) ||
-      (range_count != ranges.size() - 1)) {
-    LOG(ERROR) << "Error in parsing range string.";
+  RangeSet ranges = RangeSet::Parse(range_str);
+  if (!ranges) {
+    LOG(ERROR) << "Error parsing RangeSet string " << range_str;
     return false;
   }
-  range_count /= 2;
 
-  std::vector<std::future<bool>> threads;
+  // RangeSet::Split() splits the ranges into multiple groups with same number of blocks (except for
+  // the last group).
   size_t thread_num = std::thread::hardware_concurrency() ?: 4;
-  thread_num = std::min(thread_num, range_count);
-  size_t group_range_count = (range_count + thread_num - 1) / thread_num;
+  std::vector<RangeSet> groups = ranges.Split(thread_num);
 
-  for (size_t t = 0; t < thread_num; t++) {
-    auto thread_func = [t, group_range_count, &dm_block_device, &ranges, &partition]() {
-      size_t blk_count = 0;
-      static constexpr size_t kBlockSize = 4096;
-      std::vector<uint8_t> buf(1024 * kBlockSize);
+  std::vector<std::future<bool>> threads;
+  for (const auto& group : groups) {
+    auto thread_func = [&group, &dm_block_device, &partition]() {
       android::base::unique_fd fd(TEMP_FAILURE_RETRY(open(dm_block_device.c_str(), O_RDONLY)));
       if (fd.get() == -1) {
         PLOG(ERROR) << "Error reading " << dm_block_device << " for partition " << partition;
         return false;
       }
 
-      for (size_t i = group_range_count * 2 * t + 1;
-           i < std::min(group_range_count * 2 * (t + 1) + 1, ranges.size()); i += 2) {
-        unsigned int range_start, range_end;
-        bool parse_status = android::base::ParseUint(ranges[i], &range_start);
-        parse_status = parse_status && android::base::ParseUint(ranges[i + 1], &range_end);
-        if (!parse_status || range_start >= range_end) {
-          LOG(ERROR) << "Invalid range pair " << ranges[i] << ", " << ranges[i + 1];
-          return false;
-        }
+      static constexpr size_t kBlockSize = 4096;
+      std::vector<uint8_t> buf(1024 * kBlockSize);
 
+      size_t block_count = 0;
+      for (const auto& range : group) {
+        size_t range_start = range.first;
+        size_t range_end = range.second;
         if (lseek64(fd.get(), static_cast<off64_t>(range_start) * kBlockSize, SEEK_SET) == -1) {
           PLOG(ERROR) << "lseek to " << range_start << " failed";
           return false;
@@ -179,9 +172,9 @@ static bool read_blocks(const std::string& partition, const std::string& range_s
           }
           remain -= to_read;
         }
-        blk_count += (range_end - range_start);
+        block_count += (range_end - range_start);
       }
-      LOG(INFO) << "Finished reading " << blk_count << " blocks on " << dm_block_device;
+      LOG(INFO) << "Finished reading " << block_count << " blocks on " << dm_block_device;
       return true;
     };