如何在 Kotlin Native FileSeek、getFileLength 和 readIntoBuffer 中实现？

问题描述

如何为 Kotlin Native/iOS 正确实现这些功能？我正在尝试为 DFU 实用程序实现文件读取，但它不起作用。

iOS 实现：

actual class PlatformFile actual constructor(val filePath: String) {

    private val platformFile = NSFileHandle.fileHandleForReadingAtPath(filePath)

    actual fun setPosition(start: Long) {
        platformFile!!.seekToFileOffset(start.toULong())
    }

    actual fun getLength(): Long {
        val fileSize = NSFileManager.defaultManager.attributesOfItemAtPath(filePath,null) as NSDictionary
        return fileSize.fileSize().toLong()
        }

    actual fun readIntoBuffer(buffer: ByteArray): Int {
        val read = platformFile!!.readDataOfLength(buffer.size.toULong())
        buffer = read.toByteArray()
        return read.length.toInt()
    }
}

常见实现：

expect class PlatformFile(filePath: String) {
    /**
     * Sets the file-pointer offset,measured from the beginning of this
     * file,at which the next read or write occurs.
     */
    fun setPosition(start: Long)
    fun getLength(): Long
    /**
     * Reads up to {@code buffer.length} bytes of data from this file
     * into an array of bytes.
     * @param      buffer   the buffer into which the data is read.
     * @return     the total number of bytes read into the buffer,or
     *             {@code -1} if there is no more data because the end of
     *             this file has been reached.
     */
    fun readIntoBuffer(buffer: ByteArray): Int
}

Android 实现（工作实现）：

import java.io.RandomAccessFile
actual class PlatformFile actual constructor(filePath: String) {
    private val platformFile = RandomAccessFile(filePath,"r")
    actual fun setPosition(start: Long) = platformFile.seek(start)
    actual fun getLength(): Long = platformFile.length()
    actual fun readIntoBuffer(buffer: ByteArray): Int = platformFile.read(buffer)
}

解决方法

它究竟是如何不起作用的？编译器错误、运行时错误，或者根本没有按照您的预期运行？错误消息/堆栈跟踪会有所帮助。

另外，您是否考虑过使用 Okio？它部分是多平台的，包括文件系统部分。

https://square.github.io/okio