hashing of files

core/src/main/groovy/com/muwire/core/FileHasher.groovy

@@ -1,5 +1,11 @@
 package com.muwire.core
 
+import java.nio.MappedByteBuffer
+import java.nio.channels.FileChannel
+import java.nio.channels.FileChannel.MapMode
+import java.security.MessageDigest
+import java.security.NoSuchAlgorithmException
+
 class FileHasher {
 
 	/** max size of shared file is 128 GB */
@@ -21,4 +27,43 @@ class FileHasher {
 		
 		throw new IllegalArgumentException("File too large $size")
 	}
+	
+	final MessageDigest digest
+	
+	FileHasher() {
+		try {
+			digest = MessageDigest.getInstance("SHA-256")
+		} catch (NoSuchAlgorithmException impossible) {
+			digest = null
+			System.exit(1)
+		}
+	}
+	
+	InfoHash hashFile(File file) {
+		final long length = file.length()
+		final int size = 0x1 << getPieceSize(length)
+		int numPieces = (int) (length / size)
+		if (numPieces * size < length)
+			numPieces++
+			
+		def output = new ByteArrayOutputStream()
+		RandomAccessFile raf = new RandomAccessFile(file, "r")
+		try {
+			MappedByteBuffer buf
+			for (int i = 0; i < numPieces - 1; i++) {
+				buf = raf.getChannel().map(MapMode.READ_ONLY, size * i, size)
+				digest.update buf
+				output.write(digest.digest(), 0, 32)
+			}
+			def lastPieceLength = length - (numPieces - 1) * size
+			buf = raf.getChannel().map(MapMode.READ_ONLY, length - lastPieceLength, lastPieceLength)
+			digest.update buf
+			output.write(digest.digest(), 0, 32)
+		} finally {
+			raf.close()
+		}
+		
+		byte [] hashList = output.toByteArray()
+		InfoHash.fromHashList(hashList)
+	}
 }

core/src/test/groovy/com/muwire/core/FileHasherTest.groovy

@@ -2,10 +2,26 @@ package com.muwire.core
 
 import static org.junit.jupiter.api.Assertions.assertEquals
 
+import org.junit.After
+import org.junit.Before
 import org.junit.Test
 
 class FileHasherTest extends GroovyTestCase {
 
+	def hasher = new FileHasher()
+	File tmp
+	
+	@Before
+	void setUp() {
+		tmp = File.createTempFile("testFile", "test")
+		tmp.deleteOnExit()
+	}
+	
+	@After
+	void tearDown() {
+		tmp?.delete()
+	}
+	
 	@Test
 	void testPieceSize() {
 		assert 18 == FileHasher.getPieceSize(1000000)
@@ -14,6 +30,54 @@ class FileHasherTest extends GroovyTestCase {
 		shouldFail IllegalArgumentException, {
 			FileHasher.getPieceSize(Long.MAX_VALUE)
 		}
+	}
 	
+	@Test
+	void testHash1Byte() {
+		def fos = new FileOutputStream(tmp)
+		fos.write(0)
+		fos.close()
+		def ih = hasher.hashFile(tmp)
+		assert ih.getHashList().length == 32
+	}
+	
+	@Test
+	void testHash1PieceExact() {
+		def fos = new FileOutputStream(tmp)
+		byte [] b = new byte[ 0x1 << 18]
+		fos.write b
+		fos.close()
+		def ih = hasher.hashFile tmp
+		assert ih.getHashList().length == 32
+	}
+	
+	@Test
+	void testHash1Piece1Byte() {
+		def fos = new FileOutputStream(tmp)
+		byte [] b = new byte[ (0x1 << 18) + 1]
+		fos.write b
+		fos.close()
+		def ih = hasher.hashFile tmp
+		assert ih.getHashList().length == 64
+	}
+	
+	@Test
+	void testHash2Pieces() {
+		def fos = new FileOutputStream(tmp)
+		byte [] b = new byte[ (0x1 << 19)]
+		fos.write b
+		fos.close()
+		def ih = hasher.hashFile tmp
+		assert ih.getHashList().length == 64
+	}
+	
+	@Test
+	void testHash2Pieces2Bytes() {
+		def fos = new FileOutputStream(tmp)
+		byte [] b = new byte[ (0x1 << 19) + 2]
+		fos.write b
+		fos.close()
+		def ih = hasher.hashFile tmp
+		assert ih.getHashList().length == 32 * 3
 	}
 }