diff --git a/core/java/android/util/PackageUtils.java b/core/java/android/util/PackageUtils.java
index c5ab82dbf0c51..11481209284a5 100644
--- a/core/java/android/util/PackageUtils.java
+++ b/core/java/android/util/PackageUtils.java
@@ -171,39 +171,53 @@ public final class PackageUtils {
     }
 
     /**
-     * @see #computeSha256DigestForLargeFile(String, String)
+     * Creates a fixed size buffer based on whether the device is low ram or not. This is to be used
+     * with the {@link #computeSha256DigestForLargeFile(String, byte[])} and
+     * {@link #computeSha256DigestForLargeFile(String, byte[], String)} methods.
+     * @return a byte array of size {@link #LOW_RAM_BUFFER_SIZE_BYTES} if the device is a low RAM
+     *          device, otherwise a byte array of size {@link #HIGH_RAM_BUFFER_SIZE_BYTES}
      */
-    public static @Nullable String computeSha256DigestForLargeFile(@NonNull String filePath) {
-        return computeSha256DigestForLargeFile(filePath, null);
+    public static @NonNull byte[] createLargeFileBuffer() {
+        int bufferSize = ActivityManager.isLowRamDeviceStatic()
+                ? LOW_RAM_BUFFER_SIZE_BYTES : HIGH_RAM_BUFFER_SIZE_BYTES;
+        return new byte[bufferSize];
     }
 
     /**
-     * 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.
+     * @see #computeSha256DigestForLargeFile(String, byte[], String)
      */
     public static @Nullable String computeSha256DigestForLargeFile(@NonNull String filePath,
-            @Nullable String separator) {
+            @NonNull byte[] fileBuffer) {
+        return computeSha256DigestForLargeFile(filePath, fileBuffer, null);
+    }
+
+    /**
+     * Computes the SHA256 digest of large files. This is typically useful for large APEXs.
+     * @param filePath The path to which the file's content is to be hashed.
+     * @param fileBuffer A buffer to read file's content into memory. It is strongly recommended to
+     *                   make use of the {@link #createLargeFileBuffer()} method to create this
+     *                   buffer.
+     * @param separator Separator between each pair of characters, such as colon, or null to omit.
+     * @return The SHA256 digest or null if an error occurs.
+     */
+    public static @Nullable String computeSha256DigestForLargeFile(@NonNull String filePath,
+            @NonNull byte[] fileBuffer, @Nullable String separator) {
         MessageDigest messageDigest;
         try {
             messageDigest = MessageDigest.getInstance("SHA256");
             messageDigest.reset();
         } catch (NoSuchAlgorithmException e) {
-            // this shouldn't happen!
+            // this really 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),
+            DigestInputStream digestInputStream = new DigestInputStream(new FileInputStream(f),
                     messageDigest);
-            byte[] buffer = new byte[bufferSize];
-            while (digestStream.read(buffer) != -1);
+            while (digestInputStream.read(fileBuffer) != -1);
         } catch (IOException e) {
+            e.printStackTrace();
             return null;
         }
 
diff --git a/services/core/java/com/android/server/BinaryTransparencyService.java b/services/core/java/com/android/server/BinaryTransparencyService.java
index 877ee8218ea69..fa52ac905a433 100644
--- a/services/core/java/com/android/server/BinaryTransparencyService.java
+++ b/services/core/java/com/android/server/BinaryTransparencyService.java
@@ -500,6 +500,7 @@ public class BinaryTransparencyService extends SystemService {
         // ones appearing out of the blue. Thus, we're going to only go through our cache to check
         // for changes, rather than freshly invoking `getInstalledPackages()` and
         // `getInstalledModules()`
+        byte[] largeFileBuffer = PackageUtils.createLargeFileBuffer();
         for (Map.Entry<String, Long> entry : mBinaryLastUpdateTimes.entrySet()) {
             String packageName = entry.getKey();
             try {
@@ -513,7 +514,7 @@ public class BinaryTransparencyService extends SystemService {
 
                     // compute the digest for the updated package
                     String sha256digest = PackageUtils.computeSha256DigestForLargeFile(
-                            packageInfo.applicationInfo.sourceDir);
+                            packageInfo.applicationInfo.sourceDir, largeFileBuffer);
                     if (sha256digest == null) {
                         Slog.e(TAG, "Failed to compute SHA256sum for file at "
                                 + packageInfo.applicationInfo.sourceDir);
@@ -545,11 +546,13 @@ public class BinaryTransparencyService extends SystemService {
         // In general, we care about all APEXs, *and* all Modules, which may include some APKs.
 
         // First, we deal with all installed APEXs.
+        byte[] largeFileBuffer = PackageUtils.createLargeFileBuffer();
         for (PackageInfo packageInfo : getInstalledApexs()) {
             ApplicationInfo appInfo = packageInfo.applicationInfo;
 
             // compute SHA256 for these APEXs
-            String sha256digest = PackageUtils.computeSha256DigestForLargeFile(appInfo.sourceDir);
+            String sha256digest = PackageUtils.computeSha256DigestForLargeFile(appInfo.sourceDir,
+                    largeFileBuffer);
             if (sha256digest == null) {
                 Slog.e(TAG, String.format("Failed to compute SHA256 digest for %s",
                         packageInfo.packageName));
@@ -585,7 +588,7 @@ public class BinaryTransparencyService extends SystemService {
 
                 // compute SHA256 digest for these modules
                 String sha256digest = PackageUtils.computeSha256DigestForLargeFile(
-                        appInfo.sourceDir);
+                        appInfo.sourceDir, largeFileBuffer);
                 if (sha256digest == null) {
                     Slog.e(TAG, String.format("Failed to compute SHA256 digest for %s",
                             packageName));