DeltaCodec

Cocoa VCDiff decoder.

Uses Xdelta version 3, a C library for delta compression using VCDIFF/RFC 3284 streams.

Objective-C example

@import DeltaCodec;

NSError *error;
ARTDeltaCodec *codec = [[ARTDeltaCodec alloc] init];
[codec setBase:baseData withId:@"m1"];
NSData *outputData = [codec applyDelta:deltaData deltaId:@"m2" baseId:@"m1" error:&error];

// Output data is an utf-8 string:
NSString *output = [[NSString alloc] initWithData:outputData encoding:NSUTF8StringEncoding];

Swift example

import DeltaCodec

let codec = ARTDeltaCodec()
codec.setBase(baseData, withId: "m1")

do {
    let outputData = try codec.applyDelta(deltaData, deltaId: "m2", baseId: "m1")
    // Output data is an utf-8 string:
    let output = String(data: outputData, encoding: .utf8)
}
catch {
    print(error)
}

API Reference

• class isDelta
• class applyDelta
• setBase
• applyDelta

Stateless

class isDelta

DECLARATION

Objective-C

+(BOOL)isDelta:delta;

Swift

class func isDelta(_ delta: Data) -> Bool

Arguments:

• delta: NSData/Data (is a binary encoded as vcdiff, as specified in RFC 3284.)

Return Value:

Returns a BOOL/Boolean telling if it's a valid delta or not.

class applyDelta

DECLARATION

Objective-C

+(NSData *)applyDelta:current previous:previous error:error;

Swift

class func applyDelta(_ current: Data, previous: Data) -> Data (throws)

Arguments:

• current: NSData/Data (is the binary encoding of the information needed to transform the source to the target. It is encoded as vcdiff, as specified in RFC 3284.)
• previous: NSData/Data (is the group of bytes to transform into the target.)
• error: NSError (Objective-C only) (is the error object when something goes wrong. It's nullable so it's optional.)

Return Value:

Returns a NSData/Data object of the target. It can return nil.

Stateful

setBase

DECLARATION

Objective-C

-(void)setBase:base withId:baseId;

Swift

func setBase(_ base: Data, withId baseId: Data)

Arguments:

• base: NSData/Data (is the group of bytes to transform into the target. This is probably an old, cached version.)
• baseId: NSString/String (is an identifier of the base.)

Return Value:

Returns nothing.

applyDelta

DECLARATION

Objective-C

-(NSData *)applyDelta:delta deltaId:deltaId baseId:baseId error:error;

Swift

func applyDelta(_ delta: Data, deltaId deltaId: String, baseId baseId: String) -> Data (throws)

Arguments:

• delta: NSData/Data (is the binary encoding of the information needed to transform the source to the target. It is encoded as vcdiff, as specified in RFC 3284.)
• deltaId: NSString/String (is an identifier of the delta.)
• baseId : NSString/String (is an identifier of the base used to verify if it matches with the current assigned base.)
• error: NSError (Objective-C only) (is the error object when something goes wrong. It's nullable so it's optional.)

Return Value:

Returns a NSData object of the target. It can return nil.

Acknowledgments:

The delta will be the new base.