more efficient zero out assurance after buffer creation

mredig · mredig · commit 871e9c779e7d · 2024-11-07T21:35:25.000-06:00
diff --git a/Sources/Data Conversion.swift b/Sources/Data Conversion.swift
@@ -53,7 +53,6 @@ extension BigUInt {
         let byteCount = (self.bitWidth + 7) / 8
 
         let buffer = UnsafeMutableBufferPointer<UInt8>.allocate(capacity: byteCount)
-        buffer.initialize(repeating: 0)
 
         guard byteCount > 0 else { return UnsafeRawBufferPointer(start: buffer.baseAddress, count: 0) }
 
@@ -69,6 +68,8 @@ extension BigUInt {
                 i -= 1
             }
         }
+        let zeroOut = UnsafeMutableBufferPointer<UInt8>(start: buffer.baseAddress, count: i)
+        zeroOut.initialize(repeating: 0)
         return UnsafeRawBufferPointer(start: buffer.baseAddress, count: byteCount)
     }
 
diff --git a/Tests/BigIntTests/BigUIntTests.swift b/Tests/BigIntTests/BigUIntTests.swift
@@ -688,6 +688,7 @@ class BigUIntTests: XCTestCase {
         test(BigUInt(), [])
         test(BigUInt(1), [0x01])
         test(BigUInt(2), [0x02])
+        test(BigUInt(0x010203), [0x1, 0x2, 0x3])
         test(BigUInt(0x0102030405060708), [0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08])
         test(BigUInt(0x01) << 64 + BigUInt(0x0203040506070809), [0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09])
     }

Original file line number	Diff line number	Diff line change
`@@ -53,7 +53,6 @@ extension BigUInt {`
`53`	`53`	`let byteCount = (self.bitWidth + 7) / 8`
`54`	`54`
`55`	`55`	`let buffer = UnsafeMutableBufferPointer<UInt8>.allocate(capacity: byteCount)`
`56`		`- buffer.initialize(repeating: 0)`
`57`	`56`
`58`	`57`	`guard byteCount > 0 else { return UnsafeRawBufferPointer(start: buffer.baseAddress, count: 0) }`
`59`	`58`
`@@ -69,6 +68,8 @@ extension BigUInt {`
`69`	`68`	`i -= 1`
`70`	`69`	`}`
`71`	`70`	`}`
	`71`	`+ let zeroOut = UnsafeMutableBufferPointer<UInt8>(start: buffer.baseAddress, count: i)`
	`72`	`+ zeroOut.initialize(repeating: 0)`
`72`	`73`	`return UnsafeRawBufferPointer(start: buffer.baseAddress, count: byteCount)`
`73`	`74`	`}`
`74`	`75`
Original file line number	Diff line number	Diff line change
`@@ -688,6 +688,7 @@ class BigUIntTests: XCTestCase {`
`688`	`688`	`test(BigUInt(), [])`
`689`	`689`	`test(BigUInt(1), [0x01])`
`690`	`690`	`test(BigUInt(2), [0x02])`
	`691`	`+ test(BigUInt(0x010203), [0x1, 0x2, 0x3])`
`691`	`692`	`test(BigUInt(0x0102030405060708), [0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08])`
`692`	`693`	`test(BigUInt(0x01) << 64 + BigUInt(0x0203040506070809), [0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09])`
`693`	`694`	`}`