diff --git a/install.cpp b/install.cpp
index d86f46c..689f4a0 100644
--- a/install.cpp
+++ b/install.cpp
@@ -569,7 +569,7 @@
   }
 
   MemMapping map;
-  if (sysMapFile(path.c_str(), &map) != 0) {
+  if (!map.MapFile(path)) {
     LOG(ERROR) << "failed to map file";
     return INSTALL_CORRUPT;
   }
@@ -577,7 +577,6 @@
   // Verify package.
   if (!verify_package(map.addr, map.length)) {
     log_buffer->push_back(android::base::StringPrintf("error: %d", kZipVerificationFailure));
-    sysReleaseMap(&map);
     return INSTALL_CORRUPT;
   }
 
@@ -588,7 +587,6 @@
     LOG(ERROR) << "Can't open " << path << " : " << ErrorCodeString(err);
     log_buffer->push_back(android::base::StringPrintf("error: %d", kZipOpenFailure));
 
-    sysReleaseMap(&map);
     CloseArchive(zip);
     return INSTALL_CORRUPT;
   }
@@ -596,7 +594,6 @@
   // Additionally verify the compatibility of the package.
   if (!verify_package_compatibility(zip)) {
     log_buffer->push_back(android::base::StringPrintf("error: %d", kPackageCompatibilityFailure));
-    sysReleaseMap(&map);
     CloseArchive(zip);
     return INSTALL_CORRUPT;
   }
@@ -611,7 +608,6 @@
   ui->SetEnableReboot(true);
   ui->Print("\n");
 
-  sysReleaseMap(&map);
   CloseArchive(zip);
   return result;
 }
diff --git a/otautil/SysUtil.cpp b/otautil/SysUtil.cpp
index a2133b9..dfa2150 100644
--- a/otautil/SysUtil.cpp
+++ b/otautil/SysUtil.cpp
@@ -16,14 +16,12 @@
 
 #include "SysUtil.h"
 
-#include <errno.h>
 #include <fcntl.h>
-#include <stdint.h>
+#include <stdint.h>  // SIZE_MAX
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 
-#include <algorithm>
 #include <string>
 #include <vector>
 
@@ -32,9 +30,7 @@
 #include <android-base/strings.h>
 #include <android-base/unique_fd.h>
 
-static bool sysMapFD(int fd, MemMapping* pMap) {
-  CHECK(pMap != nullptr);
-
+bool MemMapping::MapFD(int fd) {
   struct stat sb;
   if (fstat(fd, &sb) == -1) {
     PLOG(ERROR) << "fstat(" << fd << ") failed";
@@ -47,50 +43,49 @@
     return false;
   }
 
-  pMap->addr = static_cast<unsigned char*>(memPtr);
-  pMap->length = sb.st_size;
-  pMap->ranges.push_back({ memPtr, static_cast<size_t>(sb.st_size) });
+  addr = static_cast<unsigned char*>(memPtr);
+  length = sb.st_size;
+  ranges_.clear();
+  ranges_.emplace_back(MappedRange{ memPtr, static_cast<size_t>(sb.st_size) });
 
   return true;
 }
 
 // A "block map" which looks like this (from uncrypt/uncrypt.cpp):
 //
-//     /dev/block/platform/msm_sdcc.1/by-name/userdata     # block device
-//     49652 4096                        # file size in bytes, block size
-//     3                                 # count of block ranges
-//     1000 1008                         # block range 0
-//     2100 2102                         # ... block range 1
-//     30 33                             # ... block range 2
+//   /dev/block/platform/msm_sdcc.1/by-name/userdata     # block device
+//   49652 4096                                          # file size in bytes, block size
+//   3                                                   # count of block ranges
+//   1000 1008                                           # block range 0
+//   2100 2102                                           # ... block range 1
+//   30 33                                               # ... block range 2
 //
-// Each block range represents a half-open interval; the line "30 33"
-// reprents the blocks [30, 31, 32].
-static int sysMapBlockFile(const char* filename, MemMapping* pMap) {
-  CHECK(pMap != nullptr);
-
+// Each block range represents a half-open interval; the line "30 33" reprents the blocks
+// [30, 31, 32].
+bool MemMapping::MapBlockFile(const std::string& filename) {
   std::string content;
   if (!android::base::ReadFileToString(filename, &content)) {
     PLOG(ERROR) << "Failed to read " << filename;
-    return -1;
+    return false;
   }
 
   std::vector<std::string> lines = android::base::Split(android::base::Trim(content), "\n");
   if (lines.size() < 4) {
     LOG(ERROR) << "Block map file is too short: " << lines.size();
-    return -1;
+    return false;
   }
 
   size_t size;
-  unsigned int blksize;
-  if (sscanf(lines[1].c_str(), "%zu %u", &size, &blksize) != 2) {
+  size_t blksize;
+  if (sscanf(lines[1].c_str(), "%zu %zu", &size, &blksize) != 2) {
     LOG(ERROR) << "Failed to parse file size and block size: " << lines[1];
-    return -1;
+    return false;
   }
 
   size_t range_count;
   if (sscanf(lines[2].c_str(), "%zu", &range_count) != 1) {
     LOG(ERROR) << "Failed to parse block map header: " << lines[2];
-    return -1;
+    return false;
   }
 
   size_t blocks;
@@ -101,14 +96,14 @@
       lines.size() != 3 + range_count) {
     LOG(ERROR) << "Invalid data in block map file: size " << size << ", blksize " << blksize
                << ", range_count " << range_count << ", lines " << lines.size();
-    return -1;
+    return false;
   }
 
   // Reserve enough contiguous address space for the whole file.
   void* reserve = mmap64(nullptr, blocks * blksize, PROT_NONE, MAP_PRIVATE | MAP_ANON, -1, 0);
   if (reserve == MAP_FAILED) {
     PLOG(ERROR) << "failed to reserve address space";
-    return -1;
+    return false;
   }
 
   const std::string& block_dev = lines[0];
@@ -116,10 +111,10 @@
   if (fd == -1) {
     PLOG(ERROR) << "failed to open block device " << block_dev;
     munmap(reserve, blocks * blksize);
-    return -1;
+    return false;
   }
 
-  pMap->ranges.resize(range_count);
+  ranges_.clear();
 
   unsigned char* next = static_cast<unsigned char*>(reserve);
   size_t remaining_size = blocks * blksize;
@@ -129,84 +124,79 @@
 
     size_t start, end;
     if (sscanf(line.c_str(), "%zu %zu\n", &start, &end) != 2) {
-      LOG(ERROR) << "failed to parse range " << i << " in block map: " << line;
+      LOG(ERROR) << "failed to parse range " << i << ": " << line;
       success = false;
       break;
     }
-    size_t length = (end - start) * blksize;
-    if (end <= start || (end - start) > SIZE_MAX / blksize || length > remaining_size) {
-      LOG(ERROR) << "unexpected range in block map: " << start << " " << end;
+    size_t range_size = (end - start) * blksize;
+    if (end <= start || (end - start) > SIZE_MAX / blksize || range_size > remaining_size) {
+      LOG(ERROR) << "Invalid range: " << start << " " << end;
       success = false;
       break;
     }
 
-    void* addr = mmap64(next, length, PROT_READ, MAP_PRIVATE | MAP_FIXED, fd,
-                        static_cast<off64_t>(start) * blksize);
-    if (addr == MAP_FAILED) {
-      PLOG(ERROR) << "failed to map block " << i;
+    void* range_start = mmap64(next, range_size, PROT_READ, MAP_PRIVATE | MAP_FIXED, fd,
+                               static_cast<off64_t>(start) * blksize);
+    if (range_start == MAP_FAILED) {
+      PLOG(ERROR) << "failed to map range " << i << ": " << line;
       success = false;
       break;
     }
-    pMap->ranges[i].addr = addr;
-    pMap->ranges[i].length = length;
+    ranges_.emplace_back(MappedRange{ range_start, range_size });
 
-    next += length;
-    remaining_size -= length;
+    next += range_size;
+    remaining_size -= range_size;
   }
   if (success && remaining_size != 0) {
-    LOG(ERROR) << "ranges in block map are invalid: remaining_size = " << remaining_size;
+    LOG(ERROR) << "Invalid ranges: remaining_size " << remaining_size;
     success = false;
   }
   if (!success) {
     munmap(reserve, blocks * blksize);
-    return -1;
+    return false;
   }
 
-  pMap->addr = static_cast<unsigned char*>(reserve);
-  pMap->length = size;
+  addr = static_cast<unsigned char*>(reserve);
+  length = size;
 
   LOG(INFO) << "mmapped " << range_count << " ranges";
 
-  return 0;
+  return true;
 }
 
-int sysMapFile(const char* fn, MemMapping* pMap) {
-  if (fn == nullptr || pMap == nullptr) {
-    LOG(ERROR) << "Invalid argument(s)";
-    return -1;
+bool MemMapping::MapFile(const std::string& fn) {
+  if (fn.empty()) {
+    LOG(ERROR) << "Empty filename";
+    return false;
   }
 
-  *pMap = {};
-
   if (fn[0] == '@') {
-    if (sysMapBlockFile(fn + 1, pMap) != 0) {
+    // Block map file "@/cache/recovery/block.map".
+    if (!MapBlockFile(fn.substr(1))) {
       LOG(ERROR) << "Map of '" << fn << "' failed";
-      return -1;
+      return false;
     }
   } else {
     // This is a regular file.
-    android::base::unique_fd fd(TEMP_FAILURE_RETRY(open(fn, O_RDONLY)));
+    android::base::unique_fd fd(TEMP_FAILURE_RETRY(open(fn.c_str(), O_RDONLY)));
     if (fd == -1) {
       PLOG(ERROR) << "Unable to open '" << fn << "'";
-      return -1;
+      return false;
     }
 
-    if (!sysMapFD(fd, pMap)) {
+    if (!MapFD(fd)) {
       LOG(ERROR) << "Map of '" << fn << "' failed";
-      return -1;
+      return false;
     }
   }
-  return 0;
+  return true;
 }
 
-/*
- * Release a memory mapping.
- */
-void sysReleaseMap(MemMapping* pMap) {
-  std::for_each(pMap->ranges.cbegin(), pMap->ranges.cend(), [](const MappedRange& range) {
+MemMapping::~MemMapping() {
+  for (const auto& range : ranges_) {
     if (munmap(range.addr, range.length) == -1) {
-      PLOG(ERROR) << "munmap(" << range.addr << ", " << range.length << ") failed";
+      PLOG(ERROR) << "Failed to munmap(" << range.addr << ", " << range.length << ")";
     }
-  });
-  pMap->ranges.clear();
+  };
+  ranges_.clear();
 }
diff --git a/otautil/SysUtil.h b/otautil/SysUtil.h
index 6a79bf3..52f6d20 100644
--- a/otautil/SysUtil.h
+++ b/otautil/SysUtil.h
@@ -19,37 +19,35 @@
 
 #include <sys/types.h>
 
+#include <string>
 #include <vector>
 
-struct MappedRange {
-  void* addr;
-  size_t length;
-};
-
 /*
  * Use this to keep track of mapped segments.
  */
-struct MemMapping {
-  unsigned char* addr; /* start of data */
-  size_t length;       /* length of data */
+class MemMapping {
+ public:
+  ~MemMapping();
+  // Map a file into a private, read-only memory segment. If 'filename' begins with an '@'
+  // character, it is a map of blocks to be mapped, otherwise it is treated as an ordinary file.
+  bool MapFile(const std::string& filename);
+  size_t ranges() const {
+    return ranges_.size();
+  };
 
-  std::vector<MappedRange> ranges;
+  unsigned char* addr;  // start of data
+  size_t length;        // length of data
+
+ private:
+  struct MappedRange {
+    void* addr;
+    size_t length;
+  };
+
+  bool MapBlockFile(const std::string& filename);
+  bool MapFD(int fd);
+
+  std::vector<MappedRange> ranges_;
 };
 
-/*
- * Map a file into a private, read-only memory segment.  If 'fn'
- * begins with an '@' character, it is a map of blocks to be mapped,
- * otherwise it is treated as an ordinary file.
- *
- * On success, "pMap" is filled in, and zero is returned.
- */
-int sysMapFile(const char* fn, MemMapping* pMap);
-
-/*
- * Release the pages associated with a shared memory segment.
- *
- * This does not free "pMap"; it just releases the memory.
- */
-void sysReleaseMap(MemMapping* pMap);
-
 #endif  // _OTAUTIL_SYSUTIL
diff --git a/tests/component/updater_test.cpp b/tests/component/updater_test.cpp
index dc4b5d7..35e87fd 100644
--- a/tests/component/updater_test.cpp
+++ b/tests/component/updater_test.cpp
@@ -570,7 +570,7 @@
   ASSERT_EQ(0, fclose(zip_file_ptr));
 
   MemMapping map;
-  ASSERT_EQ(0, sysMapFile(zip_file.path, &map));
+  ASSERT_TRUE(map.MapFile(zip_file.path));
   ZipArchiveHandle handle;
   ASSERT_EQ(0, OpenArchiveFromMemory(map.addr, map.length, zip_file.path, &handle));
 
@@ -646,7 +646,7 @@
   ASSERT_EQ(0, fclose(zip_file_ptr));
 
   MemMapping map;
-  ASSERT_EQ(0, sysMapFile(zip_file.path, &map));
+  ASSERT_TRUE(map.MapFile(zip_file.path));
   ZipArchiveHandle handle;
   ASSERT_EQ(0, OpenArchiveFromMemory(map.addr, map.length, zip_file.path, &handle));
 
diff --git a/tests/component/verifier_test.cpp b/tests/component/verifier_test.cpp
index 2cfb6d3..5338f05 100644
--- a/tests/component/verifier_test.cpp
+++ b/tests/component/verifier_test.cpp
@@ -38,7 +38,7 @@
   void SetUp() override {
     std::vector<std::string> args = GetParam();
     std::string package = from_testdata_base(args[0]);
-    if (sysMapFile(package.c_str(), &memmap) != 0) {
+    if (!memmap.MapFile(package)) {
       FAIL() << "Failed to mmap " << package << ": " << strerror(errno) << "\n";
     }
 
diff --git a/tests/unit/sysutil_test.cpp b/tests/unit/sysutil_test.cpp
index f469966..434ee25 100644
--- a/tests/unit/sysutil_test.cpp
+++ b/tests/unit/sysutil_test.cpp
@@ -27,27 +27,23 @@
   MemMapping mapping;
 
   // Invalid argument.
-  ASSERT_EQ(-1, sysMapFile(nullptr, &mapping));
-  ASSERT_EQ(-1, sysMapFile("/somefile", nullptr));
+  ASSERT_FALSE(mapping.MapFile(""));
 }
 
-TEST(SysUtilTest, sysMapFileRegularFile) {
+TEST(SysUtilTest, MapFileRegularFile) {
   TemporaryFile temp_file1;
   std::string content = "abc";
   ASSERT_TRUE(android::base::WriteStringToFile(content, temp_file1.path));
 
-  // sysMapFile() should map the file to one range.
+  // MemMapping::MapFile() should map the file to one range.
   MemMapping mapping;
-  ASSERT_EQ(0, sysMapFile(temp_file1.path, &mapping));
+  ASSERT_TRUE(mapping.MapFile(temp_file1.path));
   ASSERT_NE(nullptr, mapping.addr);
   ASSERT_EQ(content.size(), mapping.length);
-  ASSERT_EQ(1U, mapping.ranges.size());
-
-  sysReleaseMap(&mapping);
-  ASSERT_EQ(0U, mapping.ranges.size());
+  ASSERT_EQ(1U, mapping.ranges());
 }
 
-TEST(SysUtilTest, sysMapFileBlockMap) {
+TEST(SysUtilTest, MapFileBlockMap) {
   // Create a file that has 10 blocks.
   TemporaryFile package;
   std::string content;
@@ -63,78 +59,72 @@
   std::string block_map_content = std::string(package.path) + "\n40960 4096\n1\n0 10\n";
   ASSERT_TRUE(android::base::WriteStringToFile(block_map_content, block_map_file.path));
 
-  ASSERT_EQ(0, sysMapFile(filename.c_str(), &mapping));
+  ASSERT_TRUE(mapping.MapFile(filename));
   ASSERT_EQ(file_size, mapping.length);
-  ASSERT_EQ(1U, mapping.ranges.size());
+  ASSERT_EQ(1U, mapping.ranges());
 
   // It's okay to not have the trailing '\n'.
   block_map_content = std::string(package.path) + "\n40960 4096\n1\n0 10";
   ASSERT_TRUE(android::base::WriteStringToFile(block_map_content, block_map_file.path));
 
-  ASSERT_EQ(0, sysMapFile(filename.c_str(), &mapping));
+  ASSERT_TRUE(mapping.MapFile(filename));
   ASSERT_EQ(file_size, mapping.length);
-  ASSERT_EQ(1U, mapping.ranges.size());
+  ASSERT_EQ(1U, mapping.ranges());
 
   // Or having multiple trailing '\n's.
   block_map_content = std::string(package.path) + "\n40960 4096\n1\n0 10\n\n\n";
   ASSERT_TRUE(android::base::WriteStringToFile(block_map_content, block_map_file.path));
 
-  ASSERT_EQ(0, sysMapFile(filename.c_str(), &mapping));
+  ASSERT_TRUE(mapping.MapFile(filename));
   ASSERT_EQ(file_size, mapping.length);
-  ASSERT_EQ(1U, mapping.ranges.size());
+  ASSERT_EQ(1U, mapping.ranges());
 
   // Multiple ranges.
   block_map_content = std::string(package.path) + "\n40960 4096\n3\n0 3\n3 5\n5 10\n";
   ASSERT_TRUE(android::base::WriteStringToFile(block_map_content, block_map_file.path));
 
-  ASSERT_EQ(0, sysMapFile(filename.c_str(), &mapping));
+  ASSERT_TRUE(mapping.MapFile(filename));
   ASSERT_EQ(file_size, mapping.length);
-  ASSERT_EQ(3U, mapping.ranges.size());
-
-  sysReleaseMap(&mapping);
-  ASSERT_EQ(0U, mapping.ranges.size());
+  ASSERT_EQ(3U, mapping.ranges());
 }
 
-TEST(SysUtilTest, sysMapFileBlockMapInvalidBlockMap) {
+TEST(SysUtilTest, MapFileBlockMapInvalidBlockMap) {
   MemMapping mapping;
   TemporaryFile temp_file;
   std::string filename = std::string("@") + temp_file.path;
 
   // Block map file is too short.
   ASSERT_TRUE(android::base::WriteStringToFile("/somefile\n", temp_file.path));
-  ASSERT_EQ(-1, sysMapFile(filename.c_str(), &mapping));
+  ASSERT_FALSE(mapping.MapFile(filename));
 
   ASSERT_TRUE(android::base::WriteStringToFile("/somefile\n4096 4096\n0\n", temp_file.path));
-  ASSERT_EQ(-1, sysMapFile(filename.c_str(), &mapping));
+  ASSERT_FALSE(mapping.MapFile(filename));
 
   // Block map file has unexpected number of lines.
   ASSERT_TRUE(android::base::WriteStringToFile("/somefile\n4096 4096\n1\n", temp_file.path));
-  ASSERT_EQ(-1, sysMapFile(filename.c_str(), &mapping));
+  ASSERT_FALSE(mapping.MapFile(filename));
 
   ASSERT_TRUE(android::base::WriteStringToFile("/somefile\n4096 4096\n2\n0 1\n", temp_file.path));
-  ASSERT_EQ(-1, sysMapFile(filename.c_str(), &mapping));
+  ASSERT_FALSE(mapping.MapFile(filename));
 
   // Invalid size/blksize/range_count.
   ASSERT_TRUE(android::base::WriteStringToFile("/somefile\nabc 4096\n1\n0 1\n", temp_file.path));
-  ASSERT_EQ(-1, sysMapFile(filename.c_str(), &mapping));
+  ASSERT_FALSE(mapping.MapFile(filename));
 
   ASSERT_TRUE(android::base::WriteStringToFile("/somefile\n4096 4096\n\n0 1\n", temp_file.path));
-  ASSERT_EQ(-1, sysMapFile(filename.c_str(), &mapping));
+  ASSERT_FALSE(mapping.MapFile(filename));
 
   // size/blksize/range_count don't match.
   ASSERT_TRUE(android::base::WriteStringToFile("/somefile\n0 4096\n1\n0 1\n", temp_file.path));
-  ASSERT_EQ(-1, sysMapFile(filename.c_str(), &mapping));
+  ASSERT_FALSE(mapping.MapFile(filename));
 
   ASSERT_TRUE(android::base::WriteStringToFile("/somefile\n4096 0\n1\n0 1\n", temp_file.path));
-  ASSERT_EQ(-1, sysMapFile(filename.c_str(), &mapping));
+  ASSERT_FALSE(mapping.MapFile(filename));
 
   ASSERT_TRUE(android::base::WriteStringToFile("/somefile\n4096 4096\n0\n0 1\n", temp_file.path));
-  ASSERT_EQ(-1, sysMapFile(filename.c_str(), &mapping));
+  ASSERT_FALSE(mapping.MapFile(filename));
 
   // Invalid block dev path.
   ASSERT_TRUE(android::base::WriteStringToFile("/doesntexist\n4096 4096\n1\n0 1\n", temp_file.path));
-  ASSERT_EQ(-1, sysMapFile(filename.c_str(), &mapping));
-
-  sysReleaseMap(&mapping);
-  ASSERT_EQ(0U, mapping.ranges.size());
+  ASSERT_FALSE(mapping.MapFile(filename));
 }
diff --git a/tests/unit/zip_test.cpp b/tests/unit/zip_test.cpp
index 4a1a49b..df4e38c 100644
--- a/tests/unit/zip_test.cpp
+++ b/tests/unit/zip_test.cpp
@@ -66,9 +66,9 @@
 }
 
 TEST(ZipTest, OpenFromMemory) {
-  MemMapping map;
   std::string zip_path = from_testdata_base("ziptest_dummy-update.zip");
-  ASSERT_EQ(0, sysMapFile(zip_path.c_str(), &map));
+  MemMapping map;
+  ASSERT_TRUE(map.MapFile(zip_path));
 
   // Map an update package into memory and open the archive from there.
   ZipArchiveHandle handle;
@@ -85,6 +85,5 @@
   ASSERT_EQ(0, ExtractEntryToFile(handle, &binary_entry, tmp_binary.fd));
 
   CloseArchive(handle);
-  sysReleaseMap(&map);
 }
 
diff --git a/updater/updater.cpp b/updater/updater.cpp
index c09e267..749c86a 100644
--- a/updater/updater.cpp
+++ b/updater/updater.cpp
@@ -89,7 +89,7 @@
 
   const char* package_filename = argv[3];
   MemMapping map;
-  if (sysMapFile(package_filename, &map) != 0) {
+  if (!map.MapFile(package_filename)) {
     LOG(ERROR) << "failed to map package " << argv[3];
     return 3;
   }
@@ -213,7 +213,6 @@
   if (updater_info.package_zip) {
     CloseArchive(updater_info.package_zip);
   }
-  sysReleaseMap(&map);
 
   return 0;
 }