file digesters

src/main/java/com/mirkocaserta/bruce/Bruce.java

@@ -7,6 +7,7 @@
 import com.mirkocaserta.bruce.cipher.symmetric.EncodingCipherByKey;
 import com.mirkocaserta.bruce.digest.Digester;
 import com.mirkocaserta.bruce.digest.EncodingDigester;
+import com.mirkocaserta.bruce.digest.FileDigester;
 import com.mirkocaserta.bruce.mac.EncodingMac;
 import com.mirkocaserta.bruce.mac.Mac;
 import com.mirkocaserta.bruce.signature.Signer;
@@ -19,6 +20,8 @@
 import javax.crypto.NoSuchPaddingException;
 import javax.crypto.spec.IvParameterSpec;
 import javax.crypto.spec.SecretKeySpec;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.URL;
@@ -427,6 +430,70 @@ public static EncodingDigester digester(String algorithm, String provider, Encod
         return message -> encode(encoding, rawDigester.digest(message.getBytes(charset)));
     }
 
+    /**
+     * Returns an encoding file digester for the given algorithm.
+     *
+     * @param algorithm the algorithm (ex: <code>SHA1</code>, <code>MD5</code>, etc)
+     * @param encoding  the encoding
+     * @return an encoding file digester
+     * @throws BruceException on no such algorithm or provider exceptions
+     */
+    public static FileDigester fileDigester(String algorithm, Encoding encoding) {
+        return fileDigester(algorithm, BLANK, encoding);
+    }
+
+    /**
+     * Returns an encoding file digester for the given algorithm and provider.
+     *
+     * @param algorithm the algorithm (ex: <code>SHA1</code>, <code>MD5</code>, etc)
+     * @param provider  the provider (hint: Bouncy Castle is <code>BC</code>)
+     * @param encoding  the encoding
+     * @return an encoding file digester
+     * @throws BruceException on no such algorithm or provider exceptions
+     */
+    public static FileDigester fileDigester(String algorithm, String provider, Encoding encoding) {
+        if (encoding == null) {
+            throw new BruceException(INVALID_ENCODING_NULL);
+        }
+
+        try { // fail fast
+            if (provider == null || provider.isBlank()) {
+                MessageDigest.getInstance(algorithm);
+            } else {
+                MessageDigest.getInstance(algorithm, provider);
+            }
+        } catch (NoSuchAlgorithmException e) {
+            throw new BruceException(String.format("No such algorithm: %s", algorithm), e);
+        } catch (NoSuchProviderException e) {
+            throw new BruceException(String.format("No such provider: %s", provider), e);
+        }
+
+        return file -> {
+            try {
+                var digest = provider == null || provider.isBlank()
+                        ? MessageDigest.getInstance(algorithm)
+                        : MessageDigest.getInstance(algorithm, provider);
+                var inputStream = new FileInputStream(file);
+                var buffer = new byte[8192];
+                int read;
+
+                while ((read = inputStream.read(buffer)) > 0) {
+                    digest.update(buffer, 0, read);
+                }
+
+                return encode(encoding, digest.digest());
+            } catch (NoSuchAlgorithmException e) {
+                throw new BruceException(String.format("No such algorithm: %s", algorithm), e);
+            } catch (NoSuchProviderException e) {
+                throw new BruceException(String.format("No such provider: %s", provider), e);
+            } catch (FileNotFoundException e) {
+                throw new BruceException(String.format("No such file: %s", file), e);
+            } catch (IOException e) {
+                throw new BruceException(String.format("I/O error reading file: %s", file), e);
+            }
+        };
+    }
+
     /**
      * Returns a raw byte array message digester for the given algorithm and provider.
      *

src/main/java/com/mirkocaserta/bruce/digest/FileDigester.java

@@ -0,0 +1,24 @@
+package com.mirkocaserta.bruce.digest;
+
+import com.mirkocaserta.bruce.BruceException;
+
+import java.io.File;
+
+/**
+ * Generic interface for getting file digests
+ * in an encoded format such as hexadecimal or base64.
+ *
+ * @author Mirko Caserta ([email protected])
+ */
+public interface FileDigester {
+
+    /**
+     * Returns the file digest in encoded format.
+     *
+     * @param file the file to digest
+     * @return the file digest in encoded format
+     * @throws BruceException on digesting errors
+     */
+    String digest(File file);
+
+}

src/test/java/com/mirkocaserta/bruce/digest/FileDigesterTest.java

@@ -0,0 +1,44 @@
+package com.mirkocaserta.bruce.digest;
+
+import com.mirkocaserta.bruce.Bruce;
+import com.mirkocaserta.bruce.BruceException;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import java.io.File;
+
+import static com.mirkocaserta.bruce.Bruce.digester;
+import static com.mirkocaserta.bruce.Bruce.fileDigester;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+@DisplayName("File digester tests")
+class FileDigesterTest {
+
+    @Test
+    @DisplayName("Hexadecimal file digester for the SHA1 algorithm")
+    void sha1Hex() {
+        var digester = fileDigester("SHA1", Bruce.Encoding.HEX);
+        assertEquals("4e1243bd22c66e76c2ba9eddc1f91394e57f9f83", digester.digest(new File("src/test/resources/test-file-1")), "1st sha1");
+        assertEquals("9054fbe0b622c638224d50d20824d2ff6782e308", digester.digest(new File("src/test/resources/test-file-2")), "2nd sha1");
+    }
+
+    @Test
+    @DisplayName("Base64 file digester for the SHA1 algorithm")
+    void sha1Base64() {
+        var digester = fileDigester("SHA1", Bruce.Encoding.BASE64);
+        assertEquals("ThJDvSLGbnbCup7dwfkTlOV/n4M=", digester.digest(new File("src/test/resources/test-file-1")), "1st sha1");
+        assertEquals("kFT74LYixjgiTVDSCCTS/2eC4wg=", digester.digest(new File("src/test/resources/test-file-2")), "2nd sha1");
+    }
+
+    @Test
+    @DisplayName("Digester for an invalid algorithm should throw a DigesterException")
+    void invalidAlgorithm1() {
+        Assertions.assertThrows(
+                BruceException.class,
+                () -> fileDigester("foo", Bruce.Encoding.HEX),
+                "No such algorithm: foo"
+        );
+    }
+
+}

src/test/resources/test-file-1

@@ -0,0 +1 @@
+test

src/test/resources/test-file-2

@@ -0,0 +1 @@
+test2