Partially adapted from AFMultipartBodyStream · GitHub

// // SKSerialInputStream.h // inputstream // // Created by Soroush Khanlou on 11/4/18. // Copyright © 2018 Soroush Khanlou. All rights reserved. //

#import <Foundation/Foundation.h>

@interface SKSerialInputStream : NSInputStream

- (instancetype)initWithInputStreams:(NSArray<NSInputStream *> *)inputStreams;

@property (nonatomic, readonly) NSArray<NSInputStream *> *inputStreams;

@end

// // SKSerialInputStream.m // inputstream // // Created by Soroush Khanlou on 11/4/18. // Copyright © 2018 Soroush Khanlou. All rights reserved. //

#import "SKSerialInputStream.h"

@interface SKSerialInputStream ()

@property NSInteger currentIndex; @property (readwrite) NSStreamStatus streamStatus; @property (readwrite, copy) NSError *streamError;

@end

@implementation SKSerialInputStream

@synthesize streamError; @synthesize streamStatus; @synthesize delegate;

- (instancetype)initWithInputStreams:(NSArray<NSInputStream *> *)inputStreams { self = [super init]; if (!self) return nil; _inputStreams = inputStreams; _currentIndex = 0; return self; }

#pragma mark - NSInputStream

- (NSInteger)read:(uint8_t *)buffer maxLength:(NSUInteger)maxLength { if ([self streamStatus] == NSStreamStatusClosed) { return 0; } NSInteger totalNumberOfBytesRead = 0; while (totalNumberOfBytesRead < maxLength) { if (self.currentIndex == self.inputStreams.count) { [self close]; break; } NSInputStream *currentInputStream = self.inputStreams[self.currentIndex]; if (currentInputStream.streamStatus != NSStreamStatusOpen) { [currentInputStream open]; }

if (!currentInputStream.hasBytesAvailable) { self.currentIndex += 1; continue; } NSUInteger remainingLength = maxLength - totalNumberOfBytesRead; NSInteger numberOfBytesRead = [currentInputStream read:&buffer[totalNumberOfBytesRead] maxLength:remainingLength]; if (numberOfBytesRead == 0) { self.currentIndex += 1; continue; } if (numberOfBytesRead == -1) { self.streamError = currentInputStream.streamError; return -1; } totalNumberOfBytesRead += numberOfBytesRead;

} return totalNumberOfBytesRead; }

- (BOOL)getBuffer:(uint8_t * _Nullable *)buffer length:(NSUInteger *)length { if (self.currentIndex == self.inputStreams.count) { return NO; } return [self.inputStreams[self.currentIndex] getBuffer:buffer length:length]; }

- (BOOL)hasBytesAvailable { return YES; // ideally would be self.currentIndex != self.inputStreams.count; }

#pragma mark - NSStream

- (void)open { if (self.streamStatus == NSStreamStatusOpen) { return; } self.streamStatus = NSStreamStatusOpen; }

- (void)close { self.streamStatus = NSStreamStatusClosed; }

- (id)propertyForKey:(__unused NSString *)key { return nil; }

- (BOOL)setProperty:(__unused id)property forKey:(__unused NSString *)key { return NO; }

- (void)scheduleInRunLoop:(__unused NSRunLoop *)runLoop forMode:(__unused NSString *)mode { }

- (void)removeFromRunLoop:(__unused NSRunLoop *)runLoop forMode:(__unused NSString *)mode { }

@end