iOS开发 如何实现断点上传 求给思路

Question

断点上传 肯定意味着需要用到偏移量
NSFileHandle *readHandle = [NSFileHandle fileHandleForReadingAtPath:@"此处文件路径省略"];
[readHandle seekToFileOffset:100];//设置偏移量
NSInputStream *fileStream = [NSInputStream inputStreamWithData:[readHandle readDataToEndOfFile]];
AFHTTPRequestOperation *afOperation = [AFHTTPRequestOperation new];
afOperation.inputStream = fileStream;
AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager new];
formData appendPartWithInputStream:fileStream name:@"file" fileName:str length:此处怎么填写 mimeType:@"image/jpg"];

如上，那个length参数怎么填写呢？求大神指点迷津

Answer 1

尝试根据已上传文件大小来设置偏移量。