增加一个文件切割工具 FileSplitUtils

utilcode/src/main/java/com/blankj/utilcode/util/FileSplitUtils.java

@@ -0,0 +1,116 @@
+package com.blankj.utilcode.util;
+
+import android.os.Build;
+import android.support.annotation.RequiresApi;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.RandomAccessFile;
+import java.nio.channels.FileChannel;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.UUID;
+
+/**
+ * <pre>
+ *     author: UFreedom
+ *     blog  : http://ufreedom.me
+ *     time  : 2018/09/29
+ *     desc  : Util for file split
+ * </pre>
+ */
+@RequiresApi(api = Build.VERSION_CODES.KITKAT)
+public class FileSplitUtil {
+
+
+    /**
+     * Split a file into multiples files
+     *
+     * @param destCacheDir     The dir to be cached for split files
+     * @param srcFile          The file need to be split
+     * @param expireSplitCount How many files are expected to be cut.The value should at least 2.
+     *                         Sometimes a file may not be cut into a specific number.For example, Expire cut into 3,
+     *                         but the current file can not be completely cut after cutting 3, there may be a little left,
+     *                         and it will eventually be cut into 4
+     * @return 切片后的结果
+     */
+    public static List<File> splitFile(File destCacheDir, final int expireSplitCount, final File srcFile) throws IOException {
+        checkDestDir(destCacheDir);
+        checkSourceFile(srcFile);
+        if (expireSplitCount < 2) {
+            throw new IllegalArgumentException("The split count must at least 2");
+        }
+
+        final long sourceSize = srcFile.length();
+        long bytesPerSplit = sourceSize / expireSplitCount;
+        return splitFileInner(destCacheDir, srcFile, sourceSize, bytesPerSplit, expireSplitCount);
+    }
+
+
+    /**
+     * Split a file into multiples files
+     *
+     * @param destCacheDir The dir to be cached for split files
+     * @param srcFile      The file need to be split
+     * @param sliceSize    How big is each slice are expected to be cut. Unit（MB）
+     */
+    public static List<File> splitFile(File destCacheDir, final File srcFile, final int sliceSize) throws IOException {
+
+        checkDestDir(destCacheDir);
+        checkSourceFile(srcFile);
+
+        if (sliceSize <= 0) {
+            throw new IllegalArgumentException("The slice size must be more than zero");
+        }
+
+        final long sourceSize = srcFile.length();
+        final long bytesPerSplit = 1024L * 1024L * sliceSize;
+        final long numSplits = sourceSize / bytesPerSplit;
+
+        return splitFileInner(destCacheDir, srcFile, sourceSize, bytesPerSplit, numSplits);
+    }
+
+    private static List<File> splitFileInner(File destDir, File srcFile, long sourceSize, long bytesPerSplit, long numSplits) throws IOException {
+        List<File> partFiles = new ArrayList<>();
+        final long remainingBytes = sourceSize % bytesPerSplit;
+        int position = 0;
+        RandomAccessFile sourceFile = new RandomAccessFile(srcFile, "r");
+        FileChannel sourceChannel = sourceFile.getChannel();
+        for (; position < numSplits; position++) {
+            writePartToFile(destDir, bytesPerSplit, position * bytesPerSplit, sourceChannel, partFiles);
+        }
+
+        if (remainingBytes > 0) {
+            writePartToFile(destDir, remainingBytes, position * bytesPerSplit, sourceChannel, partFiles);
+        }
+        return partFiles;
+    }
+
+    private static void writePartToFile(File destDirFile, long byteSize, long position, FileChannel sourceChannel, List<File> partFiles) throws IOException {
+        String tempDir = destDirFile.getAbsolutePath().concat("/");
+        File file = new File(tempDir + UUID.randomUUID() + "_" + position + "" + ".splitPart");
+        RandomAccessFile toFile = new RandomAccessFile(file, "rw");
+        FileChannel toChannel = toFile.getChannel();
+        sourceChannel.position(position);
+        toChannel.transferFrom(sourceChannel, 0, byteSize);
+        partFiles.add(file);
+    }
+
+    private static void checkSourceFile(File srcFileName) {
+        if (srcFileName == null || !srcFileName.exists()) {
+            throw new NullPointerException("The source file should be non-empty or exist");
+        }
+    }
+
+    private static void checkDestDir(File cacheDir) {
+        if (cacheDir == null || !cacheDir.exists()) {
+            throw new NullPointerException("The cache directory should exist");
+        }
+
+        if (!cacheDir.isDirectory()) {
+            throw new IllegalArgumentException("The cache directory should not be a file");
+        }
+    }
+
+
+}