Allows the caller to directly manipulate the allocated disk space for a file

# eio_fallocate

(PECL eio >= 0.0.1dev)

eio_fallocate — Allows the caller to directly manipulate the allocated disk space for a file

### 说明

function eio_fallocate(
mixed `$fd`,
int `$mode`,
int `$offset`,
int `$length`,
int `$pri` = EIO_PRI_DEFAULT,
callable `$callback` = NULL,
mixed `$data` = NULL
): resource

eio_fallocate() allows the caller to directly manipulate the allocated disk space for the file specified by `fd` file descriptor for the byte range starting at `offset` and continuing for `length` bytes.

> 注意: File should be opened for writing
> `EIO_O_CREAT` should be logically OR'd with `EIO_O_WRONLY`, or `EIO_O_RDWR`

### 参数

`fd`
  Stream, Socket resource, or numeric file descriptor, e.g. returned by eio_open().
`mode`
  Currently only one flag is supported for mode: `EIO_FALLOC_FL_KEEP_SIZE` (the same as POSIX constant `FALLOC_FL_KEEP_SIZE`).
`offset`
  Specifies start of the byte range.
`length`
  Specifies length of the byte range.
`pri`
  请求的优先级：`EIO_PRI_DEFAULT`，`EIO_PRI_MIN`，`EIO_PRI_MAX` 或 `null`。如果是 `null`，`pri` 将设为 `EIO_PRI_DEFAULT`。
`callback`

  `callback` 函数在请求完成时被调用。其应匹配一下原型：

      void callback(mixed $data, int $result[, resource $req]);

  `data`
    传递给请求的用户数据。
  `result`
    针对请求的结果的值。通常是相应的系统调用返回的值。
  `req`
    可选的请求资源，可被 eio_get_last_error() 之类的函数使用。
`data`
  Arbitrary variable passed to `callback`.

### 返回值

eio_fallocate() returns request resource on success, 或者在失败时返回 `false`.

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