Custom NSInputStream implementation

MRCDataStreamDataSource.m

#import "MRCDataStreamDataSource.h"

@interface MRCDataStreamDataSource ()
@property (nonatomic, readonly) NSData *data;
@property (nonatomic) NSUInteger readOffset;
@property (nonatomic, getter = isOpenCompleted) BOOL openCompleted;
@property (nonatomic) NSError *error;
@end

@implementation MRCDataStreamDataSource
@dynamic hasBytesAvailable, atEnd;

#pragma mark Lifecycle

- (instancetype)initWithData:(NSData *)data {
    NSParameterAssert(data);
    if (self = [super init]) {
        _data = data;
    }
    return self;
}

#pragma mark POSBlobInputStreamDataSource

- (void)open {
    self.openCompleted = YES;
}

- (BOOL)hasBytesAvailable {
    return _data.length - _readOffset > 0;
}

- (BOOL)isAtEnd {
    return _data.length <= _readOffset;
}

- (id)propertyForKey:(NSString *)key {
    if (![key isEqualToString:NSStreamFileCurrentOffsetKey]) {
        return nil;
    }
    return @(_readOffset);
}

- (BOOL)setProperty:(id)property forKey:(NSString *)key {
    if (![key isEqualToString:NSStreamFileCurrentOffsetKey]) {
        return NO;
    }
    if (![property isKindOfClass:[NSNumber class]]) {
        return NO;
    }
    NSUInteger requestedOffest = [property unsignedIntegerValue];
    self.readOffset = requestedOffest;
    return YES;
}

- (BOOL)getBuffer:(uint8_t **)buffer length:(NSUInteger *)bufferLength {
    return NO;
}

- (NSInteger)read:(uint8_t *)buffer maxLength:(NSUInteger)maxLength {
    const NSUInteger readResult = MIN(maxLength, MAX(_data.length - _readOffset, 0));
    NSRange dataRange = (NSRange){
        .location = _readOffset,
        .length = readResult
    };
    [_data getBytes:buffer range:dataRange];
    self.readOffset = (_readOffset + readResult);
    return (NSInteger)readResult;
}

#pragma mark Private

- (void)setReadOffset:(NSUInteger)readOffset {
    const BOOL atEnd = readOffset >= _data.length;
    if (atEnd) {
        [self willChangeValueForKey:POSBlobInputStreamDataSourceAtEndKeyPath];
    }
    _readOffset = readOffset;
    if (atEnd) {
        [self didChangeValueForKey:POSBlobInputStreamDataSourceAtEndKeyPath];
    }
}

@end

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