iOS开发之HTTP断点续传

发布时间：2023-04-04 11:29:17 所属栏目：教程来源：

导读：在下载文件的时候，需要先获取到文件的总大小，这里使用URL作为Key，对文件属性进行扩展的方式保存文件总大小

extension URL {
/// Get extended attribute.
func extendedAttribute(forName name: Str

在下载文件的时候，需要先获取到文件的总大小，这里使用URL作为Key，对文件属性进行扩展的方式保存文件总大小

extension URL {
/// Get extended attribute.
func extendedAttribute(forName name: String) throws -> Data {
let data = try withUnsafeFileSystemRepresentation { fileSystemPath -> Data in
// Determine attribute size:
let length = getxattr(fileSystemPath, name, nil, 0, 0, 0)
guard length >= 0 else { throw URL.posixError(errno) }
// Create buffer with required size:
var data = Data(count: length)
// Retrieve attribute:
let result = data.withUnsafeMutableBytes { [count = data.count] in
getxattr(fileSystemPath, name, $0.baseAddress, count, 0, 0)
}
guard result >= 0 else { throw URL.posixError(errno) }
return data
}
return data
}
/// Set extended attribute.
func setExtendedAttribute(data: Data, forName name: String) throws {
try withUnsafeFileSystemRepresentation { fileSystemPath in
let result = data.withUnsafeBytes {
setxattr(fileSystemPath, name, $0.baseAddress, data.count, 0, 0)
}
guard result >= 0 else { throw URL.posixError(errno) }
}
}
/// Remove extended attribute.
func removeExtendedAttribute(forName name: String) throws {
try withUnsafeFileSystemRepresentation { fileSystemPath in
let result = removexattr(fileSystemPath, name, 0)
guard result >= 0 else { throw URL.posixError(errno) }
}
}
/// Get list of all extended attributes.
func listExtendedAttributes() throws -> [String] {
let list = try withUnsafeFileSystemRepresentation { fileSystemPath -> [String] in
let length = listxattr(fileSystemPath, nil, 0, 0)
guard length >= 0 else { throw URL.posixError(errno) }
// Create buffer with required size:
var namebuf = Array<CChar>(repeating: 0, count: length)
// Retrieve attribute list:
let result = listxattr(fileSystemPath, &namebuf, namebuf.count, 0)
guard result >= 0 else { throw URL.posixError(errno) }
// Extract attribute names:
let list = namebuf.split(separator: 0).compactMap {
$0.withUnsafeBufferPointer {
$0.withMemoryRebound(to: UInt8.self) {
String(bytes: $0, encoding: .utf8)
}
}
}
return list
}
return list
}
/// Helper function to create an NSError from a Unix errno.
private static func posixError(_ err: Int32) -> NSError {
return NSError(domain: NSPOSIXErrorDomain, code: Int(err), userInfo: [NSLocalizedDescriptionKey: String(cString: strerror(err))])
}
}

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