diff --git a/core/java/android/util/PackageUtils.java b/core/java/android/util/PackageUtils.java
index ff04825f788f4..c5ab82dbf0c51 100644
--- a/core/java/android/util/PackageUtils.java
+++ b/core/java/android/util/PackageUtils.java
@@ -18,13 +18,17 @@ package android.util;
 
 import android.annotation.NonNull;
 import android.annotation.Nullable;
+import android.app.ActivityManager;
 import android.content.pm.Signature;
 import android.text.TextUtils;
 
 import libcore.util.HexEncoding;
 
 import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.FileInputStream;
 import java.io.IOException;
+import java.security.DigestInputStream;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.util.Arrays;
@@ -35,6 +39,9 @@ import java.util.Arrays;
  */
 public final class PackageUtils {
 
+    private static final int LOW_RAM_BUFFER_SIZE_BYTES = 1 * 1000;            // 1 kB
+    private static final int HIGH_RAM_BUFFER_SIZE_BYTES = 1 * 1000 * 1000;    // 1 MB
+
     private PackageUtils() {
         /* hide constructor */
     }
@@ -162,4 +169,55 @@ public final class PackageUtils {
 
         return TextUtils.join(separator, pieces);
     }
+
+    /**
+     * @see #computeSha256DigestForLargeFile(String, String)
+     */
+    public static @Nullable String computeSha256DigestForLargeFile(@NonNull String filePath) {
+        return computeSha256DigestForLargeFile(filePath, null);
+    }
+
+    /**
+     * Computes the SHA256 digest of large files.
+     * @param filePath The path to which the file's content is to be hashed.
+     * @param separator Separator between each pair of characters, such as colon, or null to omit.
+     * @return The digest or null if an error occurs.
+     */
+    public static @Nullable String computeSha256DigestForLargeFile(@NonNull String filePath,
+            @Nullable String separator) {
+        MessageDigest messageDigest;
+        try {
+            messageDigest = MessageDigest.getInstance("SHA256");
+            messageDigest.reset();
+        } catch (NoSuchAlgorithmException e) {
+            // this shouldn't happen!
+            return null;
+        }
+
+        boolean isLowRamDevice = ActivityManager.isLowRamDeviceStatic();
+        int bufferSize = isLowRamDevice ? LOW_RAM_BUFFER_SIZE_BYTES : HIGH_RAM_BUFFER_SIZE_BYTES;
+
+        File f = new File(filePath);
+        try {
+            DigestInputStream digestStream = new DigestInputStream(new FileInputStream(f),
+                    messageDigest);
+            byte[] buffer = new byte[bufferSize];
+            while (digestStream.read(buffer) != -1);
+        } catch (IOException e) {
+            return null;
+        }
+
+        byte[] resultBytes = messageDigest.digest();
+
+        if (separator == null) {
+            return HexEncoding.encodeToString(resultBytes, true);
+        }
+
+        int length = resultBytes.length;
+        String[] pieces = new String[length];
+        for (int index = 0; index < length; index++) {
+            pieces[index] = HexEncoding.encodeToString(resultBytes[index], true);
+        }
+        return TextUtils.join(separator, pieces);
+    }
 }
diff --git a/services/core/java/com/android/server/BinaryTransparencyService.java b/services/core/java/com/android/server/BinaryTransparencyService.java
index d218af39405dc..6986d3bbe5852 100644
--- a/services/core/java/com/android/server/BinaryTransparencyService.java
+++ b/services/core/java/com/android/server/BinaryTransparencyService.java
@@ -36,11 +36,8 @@ import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.os.IBinaryTransparencyService;
 import com.android.internal.util.FrameworkStatsLog;
 
-import java.io.File;
 import java.io.FileDescriptor;
-import java.io.IOException;
 import java.io.PrintWriter;
-import java.nio.file.Files;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
@@ -434,7 +431,7 @@ public class BinaryTransparencyService extends SystemService {
                     entry.setValue(packageInfo.lastUpdateTime);
 
                     // compute the digest for the updated package
-                    String sha256digest = computeSha256DigestOfFile(
+                    String sha256digest = PackageUtils.computeSha256DigestForLargeFile(
                             packageInfo.applicationInfo.sourceDir);
                     if (sha256digest == null) {
                         Slog.e(TAG, "Failed to compute SHA256sum for file at "
@@ -471,7 +468,7 @@ public class BinaryTransparencyService extends SystemService {
             ApplicationInfo appInfo = packageInfo.applicationInfo;
 
             // compute SHA256 for these APEXs
-            String sha256digest = computeSha256DigestOfFile(appInfo.sourceDir);
+            String sha256digest = PackageUtils.computeSha256DigestForLargeFile(appInfo.sourceDir);
             if (sha256digest == null) {
                 Slog.e(TAG, String.format("Failed to compute SHA256 digest for %s",
                         packageInfo.packageName));
@@ -506,7 +503,8 @@ public class BinaryTransparencyService extends SystemService {
                 ApplicationInfo appInfo = packageInfo.applicationInfo;
 
                 // compute SHA256 digest for these modules
-                String sha256digest = computeSha256DigestOfFile(appInfo.sourceDir);
+                String sha256digest = PackageUtils.computeSha256DigestForLargeFile(
+                        appInfo.sourceDir);
                 if (sha256digest == null) {
                     Slog.e(TAG, String.format("Failed to compute SHA256 digest for %s",
                             packageName));
@@ -525,16 +523,4 @@ public class BinaryTransparencyService extends SystemService {
         }
     }
 
-    @Nullable
-    private String computeSha256DigestOfFile(@NonNull String pathToFile) {
-        File apexFile = new File(pathToFile);
-
-        try {
-            byte[] apexFileBytes = Files.readAllBytes(apexFile.toPath());
-            return PackageUtils.computeSha256Digest(apexFileBytes);
-        } catch (IOException e) {
-            Slog.e(TAG, String.format("I/O error occurs when reading from %s", pathToFile));
-            return null;
-        }
-    }
 }