Added read n multiple read 4

Author: FreeTymeKiyan

Other/ReadNMultipleRead4.java

@@ -0,0 +1,50 @@
+/**
+ * Similar to Read N Characters Given Read4, but the read 
+ * function may be called multiple times
+ * 
+ * Tags: 
+ */
+class ReadNMultipleRead4 {
+    
+    public static void main(String[] args) {
+        
+    }
+    
+    /**
+     * Store state of previous call
+     * Including a buffer, an offset index of the buffer, 
+     */
+    private char[] buffer = new char[4];
+    int offset = 0, bufsize = 0;
+    
+    /**
+     * Call multiple times, storing states
+     * The difference between single time multiple times is:
+     * There can be some characters return by read4 in the buffer
+     * We need to get them for the next call
+     * For example, supppose n is 5, read4 will be call twice, 3 chars remain
+     * Next read5 call needs to get those 3 characters
+     * 
+     * So we make buffer as a field variable, along with offset and bufsize
+     * If bufsize > 0, means something in buffer
+     * 
+     * @param buf Destination buffer
+     * @param n Maximum number of characters to read
+     * @return The number of characters read
+     */
+    public int read(char[] buf, int n) {
+        int readBytes = 0;
+        boolean eof = false; // flag
+        while (!eof && readBytes < n) {
+            int sz = (bufsize > 0) ? bufsize : read4(buffer);
+            if (bufsize == 0 && sz < 4) eof = true; // empty buffer, no more
+            int bytes = Math.min(n - readBytes, sz);
+            // from offset in buffer, to readBytes in output buffer
+            System.arraycopy(buffer, offset, buf, readBytes, bytes);
+            offset = (offset + bytes) % 4; // update offset
+            bufsize = sz - bytes; // size read - size copied
+            readBytes += bytes; // update readBytes
+        }
+        return readBytes;
+    }
+}