FileSystemManager.read

Introduction

This function is used to read a file.

Usage Restrictions

This function is supported in basic library version 3.0.0 or higher.

Parameters

Object object

Property	Type	Default	Required	Description
fd	string		Yes	File descriptor obtained through the FileSystemManager.open interface.
arrayBuffer	ArrayBuffer		Yes	Buffer for data to be written, must be an instance of ArrayBuffer.
offset	number	0	No	Offset of the write operation within the buffer, default is 0.
length	number	0	No	Number of bytes to read from the file, default is 0.
position	number	0	No	Starting position for reading the file. If not specified or set to null, reading will start from the current file pointer. If the position is a positive integer, the file pointer will remain unchanged and the file will be read from the specified position.
success	function		No	Callback function for a successful API call.
fail	function		No	Callback function for a failed API call.
complete	function		No	Callback function for the end of the API call (executed regardless of success or failure).

object.success

Callback Function

Parameters

Object res

Property	Type	Description
bytesRead	number	Number of bytes actually read.
arrayBuffer	ArrayBuffer	Buffer object that was written to, i.e., the arrayBuffer parameter passed to the interface.

object.fail Callback Function

Parameters

Object res

Property	Type	Description
errMsg	string	Error message

errMsg Explanation

Error message	Explanation
parameter error: F10001	Invalid parameter
bad file descriptor: F10003	Invalid file descriptor
fail permission denied: F10005	No read permission for the specified fd path
native buffer exceeds size limit: F10008	File size exceeds the limit (100M)

Sample Code

// pages/index/index.js
Page({
  read() {
    const fs = dlt.getFileSystemManager();
    const ab = new ArrayBuffer(1024);
    // Open the file
    fs.open({
      filePath: `${dlt.env.USER_DATA_PATH}/hello.txt`,
      flag: 'a+',
      success(res) {
        // Read the file into the ArrayBuffer
        fs.read({
          fd: res.fd,
          arrayBuffer: ab,
          length: 10,
          success(res) {
            console.log(res);
          },
        });
      },
    });
  },
});