canal admin

common/src/main/java/com/alibaba/otter/canal/common/utils/FileUtils.java

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+package com.alibaba.otter.canal.common.utils;
+
+import java.io.IOException;
+import java.io.RandomAccessFile;
+import java.nio.charset.StandardCharsets;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class FileUtils {
+
+    private static final Logger logger = LoggerFactory.getLogger(FileUtils.class);
+
+    public static String readFileFromOffset(String filename, int l, String charset) {
+        RandomAccessFile rf = null;
+        StringBuilder res = new StringBuilder();
+        try {
+            rf = new RandomAccessFile(filename, "r");
+
+            long fileLength = rf.length();
+
+            long start = rf.getFilePointer();
+
+            long readIndex = start + fileLength - 1;
+
+            String line;
+            rf.seek(readIndex);
+
+            int k = 0;
+            int c = -1;
+            while (readIndex > start) {
+                if (k == l) {
+                    break;
+                }
+                c = rf.read();
+                String readText = null;
+                if (c == '\n' || c == '\r') {
+                    line = rf.readLine();
+                    if (line != null) {
+                        readText = new String(line.getBytes(StandardCharsets.ISO_8859_1), charset);
+                    } else {
+                        if (k != 0) {
+                            res.insert(0, "\n");
+                        }
+                        res.insert(0, "");
+                        k++;
+                    }
+                    readIndex--;
+                }
+                readIndex--;
+                rf.seek(readIndex);
+                if (readIndex == 0) {
+                    readText = rf.readLine();
+                }
+                if (readText != null) {
+                    if (k != 0) {
+                        res.insert(0, "\n");
+                    }
+                    res.insert(0, readText);
+                    k++;
+                }
+            }
+        } catch (IOException e) {
+            logger.error(e.getMessage(), e);
+        } finally {
+            if (rf != null) {
+                try {
+                    rf.close();
+                } catch (IOException e) {
+                    // ignore
+                }
+                rf = null;
+            }
+        }
+
+        return res.toString();
+    }
+
+    public static void main(String[] args) {
+        String res = readFileFromOffset("test2.txt", 2, "UTF-8");
+        System.out.println(res);
+    }
+}