157. 用 Read4 读取 N 个字符

题意：

解题思路：

思路：
1. 循环读，循环条件判断长度是否到了n；

PHP代码实现：

/* The read4 API is defined in the parent class Reader4.
      public function read4(&$buf){} */
class Solution extends Reader4 {
    /**
     * @param  Char[]   &$buf    Destination buffer
     * @param  Integer  $n        Number of characters to read
     * @return Integer             The number of actual characters read
     */
    //file-> read4 -> 4个一组，每组读完放到buf里面-> 读到n个结果，返回个数
    function read(&$buf, $n) {
        //临时存放read4结果的数组
        $tmp = [];
        //定义tmp指针
        $index = 0;
        //4个一组，每组读完放到buf里
        while ($index < $n) {//没有读够n个字符
            //当前读到的长度
            $len = $this->read4($tmp);
            //pointer是tmp里面的index
            $pointer = 0;
            //把tmp读到的临时数据放到buf里；
            //buf里的数量不足n，pointer的位置没有到len
            while ($index < $n && $pointer < $len) {
                $buf[$index] = $tmp[$pointer];
                $index++;
                $pointer++;
            }
            //已经读完file.ex filr "abcde", n = 6
            if ($len < 4) break;
        }
        return $index;
    }
}

GO代码实现：

/**
 * The read4 API is already defined for you.
 *
 *     read4 := func(buf []byte) int
 *
 * // Below is an example of how the read4 API can be called.
 * file := File("abcdefghijk") // File is "abcdefghijk", initially file pointer (fp) points to 'a'
 * buf := make([]byte, 4) // Create buffer with enough space to store characters
 * read4(buf) // read4 returns 4. Now buf = ['a','b','c','d'], fp points to 'e'
 * read4(buf) // read4 returns 4. Now buf = ['e','f','g','h'], fp points to 'i'
 * read4(buf) // read4 returns 3. Now buf = ['i','j','k',...], fp points to end of file
 */
var solution = func(read4 func([]byte) int) func([]byte, int) int {
    // implement read below.
    return func(buf []byte, n int) int {
        tmp := make([]byte, 4)
        index := 0
        for index < n {
            len := read4(tmp)
            pointer := 0
            for index < n && pointer < len {
                buf[index] = tmp[pointer]
                index++
                pointer++
            }
            if len < 4 {
                break
            }
        }
        return index
    }
}