Initial commit

app/src/main/java/com/aryan/reader/FileHasher.kt

@@ -0,0 +1,39 @@
+package com.aryan.reader
+
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+import java.io.InputStream
+import java.security.MessageDigest
+
+object FileHasher {
+    /**
+     * Calculates the SHA-256 hash of an input stream.
+     * @param inputStreamProvider A lambda that provides the InputStream. This is important to ensure
+     * the stream is opened on the correct thread.
+     * @return The SHA-256 hash as a hex string, or null if an error occurs.
+     */
+    suspend fun calculateSha256(inputStreamProvider: () -> InputStream?): String? = withContext(Dispatchers.IO) {
+        try {
+            val digest = MessageDigest.getInstance("SHA-256")
+            inputStreamProvider()?.use { inputStream ->
+                val buffer = ByteArray(8192)
+                var bytesRead: Int
+                while (inputStream.read(buffer).also { bytesRead = it } != -1) {
+                    digest.update(buffer, 0, bytesRead)
+                }
+            } ?: return@withContext null // Return null if stream provider returns null
+
+            // Convert byte array to hex string
+            val hashBytes = digest.digest()
+            val hexString = StringBuilder()
+            for (byte in hashBytes) {
+                hexString.append(String.format("%02x", byte))
+            }
+            hexString.toString()
+        } catch (e: Exception) {
+            // In a real app, you'd want to log this error
+            e.printStackTrace()
+            null
+        }
+    }
+}