Fix tests for 32-bit platforms, tested for Android armv7 (#1877)

Motivation:

Get the tests passing on 32-bit platforms again.

Modifications:

- Change the way _UInt56.max is initialized.
- Set the proper max capacity for AdaptiveRecvByteBufferAllocator
  and change the test to match it.
- Add a cmsghdrExample for Android armv7.

Result:

All the same tests pass on Android armv7 as Android AArch64.

Sources/NIO/IntegerTypes.swift

@@ -75,7 +75,8 @@ struct _UInt56 {
 
     static let bitWidth: Int = 56
 
-    static let max: _UInt56 = .init((1 << 56) - 1)
+    private static let initializeUInt64 : UInt64 = (1 << 56) - 1
+    static let max: _UInt56 = .init(initializeUInt64)
     static let min: _UInt56 = .init(0)
 }
 

Sources/NIO/RecvByteBufferAllocator.swift

@@ -55,7 +55,7 @@ public struct AdaptiveRecvByteBufferAllocator: RecvByteBufferAllocator {
     private var nextReceiveBufferSize: Int
     private var decreaseNow: Bool
 
-    private static let maximumAllocationSize = 1 << 31
+    private static let maximumAllocationSize = 1 << 30
 
     public init() {
         self.init(minimum: 64, initial: 2048, maximum: 65536)
@@ -93,7 +93,7 @@ public struct AdaptiveRecvByteBufferAllocator: RecvByteBufferAllocator {
         // Here we need to be careful with 32-bit systems: if maximum is too large then any shift or multiply will overflow, which
         // we don't want. Instead we check, and clamp to this current value if we overflow.
         let upperBoundCandidate = Int(truncatingIfNeeded: Int64(self.nextReceiveBufferSize) &<< 1)
-        let upperBound = upperBoundCandidate == 0 ? self.nextReceiveBufferSize : upperBoundCandidate
+        let upperBound = upperBoundCandidate <= 0 ? self.nextReceiveBufferSize : upperBoundCandidate
 
         if actualReadBytes <= lowerBound && lowerBound >= self.minimum {
             if self.decreaseNow {
@@ -102,7 +102,8 @@ public struct AdaptiveRecvByteBufferAllocator: RecvByteBufferAllocator {
             } else {
                 self.decreaseNow = true
             }
-        } else if actualReadBytes >= self.nextReceiveBufferSize && upperBound <= self.maximum {
+        } else if actualReadBytes >= self.nextReceiveBufferSize && upperBound <= self.maximum &&
+                  self.nextReceiveBufferSize != upperBound {
             self.nextReceiveBufferSize = upperBound
             self.decreaseNow = false
             mayGrow = true

Tests/NIOTests/RecvByteBufAllocatorTest.swift

@@ -117,8 +117,8 @@ final class AdaptiveRecvByteBufferAllocatorTest: XCTestCase {
         }
 
         let buffer = self.adaptive.buffer(allocator: self.allocator)
-        XCTAssertEqual(buffer.capacity, 1 << 31)
-        XCTAssertEqual(self.adaptive.maximum, 1 << 31)
+        XCTAssertEqual(buffer.capacity, 1 << 30)
+        XCTAssertEqual(self.adaptive.maximum, 1 << 30)
         XCTAssertEqual(self.adaptive.minimum, 0)
     }
 
@@ -136,8 +136,8 @@ final class AdaptiveRecvByteBufferAllocatorTest: XCTestCase {
         }
 
         let adaptive = AdaptiveRecvByteBufferAllocator(minimum: targetValue, initial: targetValue + 1, maximum: targetValue + 2)
-        XCTAssertEqual(adaptive.minimum, 1 << 31)
-        XCTAssertEqual(adaptive.maximum, 1 << 31)
-        XCTAssertEqual(adaptive.initial, 1 << 31)
+        XCTAssertEqual(adaptive.minimum, 1 << 30)
+        XCTAssertEqual(adaptive.maximum, 1 << 30)
+        XCTAssertEqual(adaptive.initial, 1 << 30)
     }
 }

Tests/NIOTests/SystemTest.swift

@@ -62,6 +62,21 @@ class SystemTest: XCTestCase {
     private static let cmsghdr_secondDataCount = 1
     private static let cmsghdr_firstType = IP_RECVDSTADDR
     private static let cmsghdr_secondType = IP_RECVTOS
+    #elseif os(Android) && arch(arm)
+    private static let cmsghdrExample: [UInt8] = [0x10, 0x00, 0x00, 0x00, // Length 16 including header
+                                                  0x00, 0x00, 0x00, 0x00, // IPPROTO_IP
+                                                  0x08, 0x00, 0x00, 0x00, // IP_PKTINFO
+                                                  0x7F, 0x00, 0x00, 0x01, // 127.0.0.1
+                                                  0x0D, 0x00, 0x00, 0x00, // Length 13 including header
+                                                  0x00, 0x00, 0x00, 0x00, // IPPROTO_IP
+                                                  0x01, 0x00, 0x00, 0x00, // IP_TOS
+                                                  0x01, 0x00, 0x00, 0x00] // ECT-1 (1 byte)
+    private static let cmsghdr_secondStartPosition = 16
+    private static let cmsghdr_firstDataStart = 12
+    private static let cmsghdr_firstDataCount = 4
+    private static let cmsghdr_secondDataCount = 1
+    private static let cmsghdr_firstType = IP_PKTINFO
+    private static let cmsghdr_secondType = IP_TOS
     #elseif os(Linux) || os(Android)
     // Example twin data options captured on Linux
     private static let cmsghdrExample: [UInt8] = [