DataReader and PassiveDataReader: Added single byte accessors

orchetect · Aug 18, 2022 · 40aeaa0 · 40aeaa0
1 parent 98b680f
commit 40aeaa0
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Showing 4 changed files with 101 additions and 2 deletions.
diff --git a/Sources/OTCore/Abstractions/DataReader.swift b/Sources/OTCore/Abstractions/DataReader.swift
@@ -35,10 +35,26 @@ public struct DataReader {
     }
 
     /// Manually advance by _n_ number of bytes from current read offset.
+    /// Note that this method is unchecked which may result in an offset beyond the end of the data stream.
     public mutating func advanceBy(_ count: Int) {
         readOffset += count
     }
 
+    /// Return the next byte and increment the read offset.
+    ///
+    /// If no bytes remain, `nil` will be returned.
+    public mutating func readByte() -> UInt8? {
+        guard let d = dataByte() else { return nil }
+        defer { readOffset += 1 }
+        return d
+    }
+
+    /// Read the next byte without advancing the read offset.
+    /// If no bytes remain, `nil` will be returned.
+    public func nonAdvancingReadByte() -> UInt8? {
+        dataByte()
+    }
+
     /// Return the next _n_ number of bytes and increment the read offset.
     ///
     /// If `bytes` parameter is nil, the remainder of the data will be returned.
@@ -59,6 +75,11 @@ public struct DataReader {
 
     // MARK: - Internal
 
+    func dataByte() -> UInt8? {
+        guard remainingByteCount > 0 else { return nil }
+        return base[readOffset]
+    }
+
     func data(bytes count: Int? = nil) -> (data: Data, advanceCount: Int)? {
         if count == 0 {
             return (data: Data(), advanceCount: 0)

diff --git a/Sources/OTCore/Abstractions/PassiveDataReader.swift b/Sources/OTCore/Abstractions/PassiveDataReader.swift
@@ -45,10 +45,26 @@ public struct PassiveDataReader<D: DataProtocol> {
     // MARK: - Methods
 
     /// Manually advance by _n_ number of bytes from current read offset.
+    /// Note that this method is unchecked which may result in an offset beyond the end of the data stream.
     public mutating func advanceBy(_ count: Int) {
         readOffset += count
     }
 
+    /// Return the next byte and increment the read offset.
+    ///
+    /// If no bytes remain, `nil` will be returned.
+    public mutating func readByte() -> D.Element? {
+        guard let d = dataByte() else { return nil }
+        defer { readOffset += 1 }
+        return d
+    }
+
+    /// Read the next byte without advancing the read offset.
+    /// If no bytes remain, `nil` will be returned.
+    public func nonAdvancingReadByte() -> D.Element? {
+        dataByte()
+    }
+
     /// Return the next _n_ number of bytes and increment the read offset.
     ///
     /// If `bytes` parameter is nil, the remainder of the data will be returned.
@@ -75,6 +91,12 @@ public struct PassiveDataReader<D: DataProtocol> {
         return out
     }
 
+    func dataByte() -> D.Element? {
+        guard remainingByteCount > 0 else { return nil }
+        let readPosIndex = withData { $0.index($0.startIndex, offsetBy: readOffset) }
+        return withData { $0[readPosIndex] }
+    }
+
     func data(bytes count: Int? = nil) -> (data: D.SubSequence, advanceCount: Int)? {
         if count == 0 {
             return (data: withData { $0[$0.startIndex ..< $0.startIndex] }, advanceCount: 0)

diff --git a/Tests/OTCoreTests/Abstractions/DataReader Tests.swift b/Tests/OTCoreTests/Abstractions/DataReader Tests.swift
@@ -15,7 +15,7 @@ class Abstractions_DataReader_Tests: XCTestCase {
     func testRead() {
         let data = Data([0x01, 0x02, 0x03, 0x04])
 
-        // .read - byte by byte
+        // .read(bytes:)
         do {
             var dr = DataReader(data)
 
@@ -33,6 +33,24 @@ class Abstractions_DataReader_Tests: XCTestCase {
             XCTAssertEqual(dr.remainingByteCount, 0)
         }
 
+        // .readByte()
+        do {
+            var dr = DataReader(data)
+
+            XCTAssertEqual(dr.readOffset, 0)
+            XCTAssertEqual(dr.remainingByteCount, 4)
+            XCTAssertEqual(dr.readByte(), 0x01)
+            XCTAssertEqual(dr.remainingByteCount, 3)
+            XCTAssertEqual(dr.readByte(), 0x02)
+            XCTAssertEqual(dr.remainingByteCount, 2)
+            XCTAssertEqual(dr.readByte(), 0x03)
+            XCTAssertEqual(dr.remainingByteCount, 1)
+            XCTAssertEqual(dr.readByte(), 0x04)
+            XCTAssertEqual(dr.remainingByteCount, 0)
+            XCTAssertEqual(dr.readByte(), nil)
+            XCTAssertEqual(dr.remainingByteCount, 0)
+        }
+
         // .read - nil read - return all remaining bytes
         do {
             var dr = DataReader(data)
@@ -67,6 +85,16 @@ class Abstractions_DataReader_Tests: XCTestCase {
             XCTAssertEqual(dr.read(bytes: 1), Data([0x01]))
         }
 
+        // single bytes
+        do {
+            var dr = DataReader(data)
+
+            XCTAssertEqual(dr.nonAdvancingReadByte(), data[0])
+            XCTAssertEqual(dr.nonAdvancingReadByte(), data[0])
+            XCTAssertEqual(dr.readByte(), data[0])
+            XCTAssertEqual(dr.readByte(), data[1])
+        }
+
         // .nonAdvancingRead - read byte counts
         do {
             let dr = DataReader(data)

diff --git a/Tests/OTCoreTests/Abstractions/PassiveDataReader Tests.swift b/Tests/OTCoreTests/Abstractions/PassiveDataReader Tests.swift
@@ -15,7 +15,7 @@ class Abstractions_PassiveDataReader_Tests: XCTestCase {
     func testRead() {
         var data = Data([0x01, 0x02, 0x03, 0x04])
 
-        // .read - byte by byte
+        // .read(bytes:)
         do {
             var dr = PassiveDataReader { $0(&data) }
 
@@ -33,6 +33,24 @@ class Abstractions_PassiveDataReader_Tests: XCTestCase {
             XCTAssertEqual(dr.remainingByteCount, 0)
         }
 
+        // .readByte()
+        do {
+            var dr = PassiveDataReader { $0(&data) }
+
+            XCTAssertEqual(dr.readOffset, 0)
+            XCTAssertEqual(dr.remainingByteCount, 4)
+            XCTAssertEqual(dr.readByte(), 0x01)
+            XCTAssertEqual(dr.remainingByteCount, 3)
+            XCTAssertEqual(dr.readByte(), 0x02)
+            XCTAssertEqual(dr.remainingByteCount, 2)
+            XCTAssertEqual(dr.readByte(), 0x03)
+            XCTAssertEqual(dr.remainingByteCount, 1)
+            XCTAssertEqual(dr.readByte(), 0x04)
+            XCTAssertEqual(dr.remainingByteCount, 0)
+            XCTAssertEqual(dr.readByte(), nil)
+            XCTAssertEqual(dr.remainingByteCount, 0)
+        }
+
         // .read - nil read - return all remaining bytes
         do {
             var dr = PassiveDataReader { $0(&data) }
@@ -67,6 +85,16 @@ class Abstractions_PassiveDataReader_Tests: XCTestCase {
             XCTAssertEqual(dr.read(bytes: 1), Data([0x01]))
         }
 
+        // single bytes
+        do {
+            var dr = PassiveDataReader { $0(&data) }
+
+            XCTAssertEqual(dr.nonAdvancingReadByte(), data[0])
+            XCTAssertEqual(dr.nonAdvancingReadByte(), data[0])
+            XCTAssertEqual(dr.readByte(), data[0])
+            XCTAssertEqual(dr.readByte(), data[1])
+        }
+
         // .nonAdvancingRead - read byte counts
         do {
             let dr = PassiveDataReader { $0(&data) }