From a0750526cc2b36248a9fc4c8710eb643ec97521e Mon Sep 17 00:00:00 2001
From: louzin <294098546@qq.com>
Date: Mon, 18 Mar 2024 08:52:08 +0800
Subject: [PATCH] Pipe & FileLock

---
 src/doc/FileLock.md                                | 47 ++++++++++++++++++++++
 src/doc/pipe.md                                    | 28 +++++++++++++
 .../com/louzin/niodemo/filelock/fileLockCRUD.java  |  5 +++
 .../java/com/louzin/niodemo/pipe/pipecrud.java     | 32 +++++++++++++++
 4 files changed, 112 insertions(+)
 create mode 100644 src/doc/FileLock.md
 create mode 100644 src/doc/pipe.md
 create mode 100644 src/main/java/com/louzin/niodemo/filelock/fileLockCRUD.java
 create mode 100644 src/main/java/com/louzin/niodemo/pipe/pipecrud.java

diff --git a/src/doc/FileLock.md b/src/doc/FileLock.md
new file mode 100644
index 0000000..8245767
--- /dev/null
+++ b/src/doc/FileLock.md
@@ -0,0 +1,47 @@
+# FileLock
+在OS中很常见，用来避免多个程序同时修改同一个文件造成的不同步问题
+
+给一个文件加锁，同一时间只有一个程序能修改此文件
+
+**文件锁是进程级别的，不是线程级别的**
+
+文件锁可以解决多个进程之间的不同步，但不能解决多线程的问题
+
+文件锁是JVM持有的，一但获取到文件锁，要调用
+- release()
+- 关闭FileChannel对象
+- JVM退出
+
+才会释放这个锁
+
+## 分类
+
+### 排他锁
+独占锁，仅该进程可操作，其他进程不能操作，直至释放锁
+### 共享锁
+其他进程仅可读，直到释放锁，是线程安全的
+
+```java
+import java.io.FileOutputStream;
+import java.nio.channels.FileChannel;
+
+FileChannel fileChannel = new FileOutputStream("./1.txt").getChannel;
+File lock = fileChannel.lock();
+lock.release();
+```
+## 获取文件锁的方法
+- lock():排他锁
+- lock(long position,long size,boolean shared):第一、二个参数表示加锁位置，第三个参数表示是否为共享锁
+- tryLock():排他锁
+- tryLock(long position,long size,boolean shared):自定义锁，若指定共享锁，则其他进程只读，若尝试写入会抛出异常
+
+### lock & trylock
+- lock：阻塞
+- trylock:非阻塞，获取成功返回当前对象，否则为null
+
+## 其他方法
+### boolean isShared()
+### boolean isValid()
+此文件锁是否还有效
+
+在某些os上对某个文件枷锁后，不能对该文件使用通道映射
\ No newline at end of file
diff --git a/src/doc/pipe.md b/src/doc/pipe.md
new file mode 100644
index 0000000..4073e86
--- /dev/null
+++ b/src/doc/pipe.md
@@ -0,0 +1,28 @@
+# Pipe
+Java NIO管道是线程之间的单向数据连接
+
+Pipe有一个source和一个sink通道，数据会写到sink，从source读取
+
+## Pipe CRUD
+```java
+ public void createPipe() throws IOException {
+        //Get Pipe
+        Pipe open = Pipe.open();
+        //Get sink Pipe
+        Pipe.SinkChannel sink = open.sink();
+        //Get Buffer
+        ByteBuffer allocate = ByteBuffer.allocate(1024);
+        //write into sink Pipe
+        allocate.put("louzin".getBytes(StandardCharsets.UTF_8));
+        allocate.flip();
+        sink.write(allocate);
+        //Get source Pipe   
+        Pipe.SourceChannel source = open.source();
+        //create Buffer and read source Pipe
+        ByteBuffer allocate1 = ByteBuffer.allocate(1024);
+        int length = source.read(allocate1);
+        allocate1.flip();
+        System.out.println(new String(allocate1.array(),0,length));
+        //close Pipe
+    }
+```
diff --git a/src/main/java/com/louzin/niodemo/filelock/fileLockCRUD.java b/src/main/java/com/louzin/niodemo/filelock/fileLockCRUD.java
new file mode 100644
index 0000000..d044aa8
--- /dev/null
+++ b/src/main/java/com/louzin/niodemo/filelock/fileLockCRUD.java
@@ -0,0 +1,5 @@
+package com.louzin.niodemo.filelock;
+
+public class fileLockCRUD {
+
+}
diff --git a/src/main/java/com/louzin/niodemo/pipe/pipecrud.java b/src/main/java/com/louzin/niodemo/pipe/pipecrud.java
new file mode 100644
index 0000000..2e0782e
--- /dev/null
+++ b/src/main/java/com/louzin/niodemo/pipe/pipecrud.java
@@ -0,0 +1,32 @@
+package com.louzin.niodemo.pipe;
+
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.channels.Pipe;
+import java.nio.charset.StandardCharsets;
+
+public class pipecrud {
+    @Test
+    public void createPipe() throws IOException {
+        //Get Pipe
+        Pipe open = Pipe.open();
+        //Get sink Pipe
+        Pipe.SinkChannel sink = open.sink();
+        //Get Buffer
+        ByteBuffer allocate = ByteBuffer.allocate(1024);
+        //write into sink Pipe
+        allocate.put("louzin".getBytes(StandardCharsets.UTF_8));
+        allocate.flip();
+        sink.write(allocate);
+        //Get source Pipe   
+        Pipe.SourceChannel source = open.source();
+        //create Buffer and read source Pipe
+        ByteBuffer allocate1 = ByteBuffer.allocate(1024);
+        int length = source.read(allocate1);
+        allocate1.flip();
+        System.out.println(new String(allocate1.array(),0,length));
+        //close Pipe
+    }
+}