158. 用 Read4 读取 N 个字符 II

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，到了之后继续下一轮读取操作；

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
     */
    public $pointer = 0;
    public $len = 0;
    public $tmp = [];
    function read(&$buf, $n) {
        $index = 0;
        while ($index < $n) {
            if ($this->pointer == 0) {
                $this->len = $this->read4($this->tmp);
            }
            if ($this->len == 0) break;
            while ($index < $n && $this->pointer < $this->len) {
                $buf[$index++] = $this->tmp[$this->pointer++];
            }
            // 说明临时字符数组中的内容已经读完，pointer置零以便执行下一次read4操作
            if ($this->pointer >= $this->len) $this->pointer = 0;
        }
        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.
    tmp := make([]byte, 4)
    pointer, len := 0, 0
    return func(buf []byte, n int) int {
        index := 0
        for index < n {
            if pointer == 0 {
                len = read4(tmp)
            }
            if len == 0 {
                break
            }
            for index < n && pointer < len {
                buf[index] = tmp[pointer]
                index++
                pointer++
            }
            if pointer >= len {
                pointer = 0
            }
        }
        return index
    }
}