Data only calculates hashValue on first 80 bytes

Originator:peter
Number:rdar://30830682 Date Originated:March 3 2017, 2:39 PM
Status:open Resolved:
Product:iOS + SDK Product Version:
Classification: Reproducible:yes
 
Area:
Foundation

Summary:
import Foundation

let eightyBytes: [UInt8] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
let data1 = Data(bytes: eightyBytes + [0])
let data2 = Data(bytes: eightyBytes + [1])

assert(data1.hashValue != data2.hashValue)

Steps to Reproduce:
Run the above code.

Expected Results:
Hash value should be different.

Actual Results:
Hash value is identical.

Version:
Xcode 8.2 (8C38) Simulator 

Notes:
We read SVG files as Data and set as properties in structs we need to implement Hashable on. Too often they are identical in the first 80+ bytes.

Configuration:
Simulator running iOS

Comments


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