Improved buffer copy method and added a copyInto and getStringAscii method. Added clamp to Math.kt.

core/src/commonMain/kotlin/world/phantasmal/core/math/Math.kt

@@ -14,3 +14,10 @@ fun radToDeg(rad: Double): Double = rad * TO_DEG
  * Converts degrees to radians.
  */
 fun degToRad(deg: Double): Double = deg * TO_RAD
+
+fun clamp(value: Int, min: Int, max: Int): Int =
+    when {
+        value < min -> min
+        value > max -> max
+        else -> value
+    }

psolib/src/commonMain/kotlin/world/phantasmal/psolib/buffer/Buffer.kt

@@ -50,6 +50,11 @@ expect class Buffer {
      */
     fun getFloat(offset: Int): Float
 
+    /**
+     * Reads a ASCII-encoded string at the given offset.
+     */
+    fun getStringAscii(offset: Int, maxByteLength: Int, nullTerminated: Boolean): String
+
     /**
      * Reads a UTF-16-encoded string at the given offset.
      */
@@ -108,9 +113,17 @@ expect class Buffer {
     fun toBase64(): String
 
     /**
-     * Returns a copy of this buffer of the same size. The copy's capacity will equal its size.
+     * Returns a copy of this buffer. The copy's capacity will equal its size. If [size] is greater
+     * than this buffer's size, the remaining bytes will be zeroed out.
      */
-    fun copy(): Buffer
+    fun copy(offset: Int = 0, size: Int = this.size): Buffer
+
+    fun copyInto(
+        destination: Buffer,
+        destinationOffset: Int = 0,
+        offset: Int = 0,
+        size: Int = this.size,
+    )
 
     companion object {
         /**

psolib/src/commonTest/kotlin/world/phantasmal/psolib/buffer/BufferTests.kt

@@ -101,4 +101,16 @@ class BufferTests : LibTestSuite {
         assertEquals(-9, buf2.getByte(2))
         assertEquals(base2, buf2.toBase64())
     }
+
+    @Test
+    fun copy() {
+        val buf = Buffer.fromByteArray(byteArrayOf(0, 1, 2, 3, 4, 5, 6, 7, 8, 9))
+        val copy = buf.copy(offset = 3, size = 4)
+
+        assertEquals(4, copy.size)
+        assertEquals(3, copy.getByte(0))
+        assertEquals(4, copy.getByte(1))
+        assertEquals(5, copy.getByte(2))
+        assertEquals(6, copy.getByte(3))
+    }
 }

psolib/src/jsMain/kotlin/world/phantasmal/psolib/buffer/Buffer.kt

@@ -70,6 +70,23 @@ actual class Buffer private constructor(
         return dataView.getFloat32(offset, littleEndian)
     }
 
+    actual fun getStringAscii(
+        offset: Int,
+        maxByteLength: Int,
+        nullTerminated: Boolean,
+    ): String =
+        buildString {
+            for (i in 0 until maxByteLength) {
+                val codePoint = (getByte(offset + i).toInt() and 0xFF).toChar()
+
+                if (nullTerminated && codePoint == '\u0000') {
+                    break
+                }
+
+                append(codePoint)
+            }
+        }
+
     actual fun getStringUtf16(
         offset: Int,
         maxByteLength: Int,
@@ -157,8 +174,30 @@ actual class Buffer private constructor(
         return self.btoa(str)
     }
 
-    actual fun copy(): Buffer =
+    actual fun copy(offset: Int, size: Int): Buffer {
-        Buffer(arrayBuffer.slice(0, size), size, endianness)
+        val newBuffer = withSize(size, endianness)
+        copyInto(newBuffer, destinationOffset = 0, offset, size.coerceAtMost(this.size - offset))
+        return newBuffer
+    }
+
+    actual fun copyInto(destination: Buffer, destinationOffset: Int, offset: Int, size: Int) {
+        require(offset >= 0 && offset <= this.size) {
+            "Offset $offset is out of bounds."
+        }
+        require(destinationOffset >= 0 && destinationOffset <= this.size) {
+            "Destination offset $destinationOffset is out of bounds."
+        }
+        require(
+            size >= 0 &&
+                    destinationOffset + size <= destination.size &&
+                    offset + size <= this.size
+        ) {
+            "Size $size is out of bounds."
+        }
+
+        Uint8Array(destination.arrayBuffer, destinationOffset)
+            .set(Uint8Array(arrayBuffer, offset, size))
+    }
 
     /**
      * Checks whether we can read [size] bytes at [offset].

psolib/src/jvmMain/kotlin/world/phantasmal/psolib/buffer/Buffer.kt

@@ -27,6 +27,11 @@ actual class Buffer private constructor(
     actual val capacity: Int
         get() = buf.capacity()
 
+    /**
+     * The backing byte array. Changes to this array will be reflected by the buffer.
+     */
+    val byteArray: ByteArray get() = buf.array()
+
     init {
         this.endianness = endianness
     }
@@ -66,6 +71,23 @@ actual class Buffer private constructor(
         return buf.getFloat(offset)
     }
 
+    actual fun getStringAscii(
+        offset: Int,
+        maxByteLength: Int,
+        nullTerminated: Boolean,
+    ): String =
+        buildString {
+            for (i in 0 until maxByteLength) {
+                val codePoint = (buf.get(offset + i).toInt() and 0xFF).toChar()
+
+                if (nullTerminated && codePoint == '\u0000') {
+                    break
+                }
+
+                append(codePoint)
+            }
+        }
+
     actual fun getStringUtf16(
         offset: Int,
         maxByteLength: Int,
@@ -154,8 +176,34 @@ actual class Buffer private constructor(
         return str
     }
 
-    actual fun copy(): Buffer =
+    actual fun copy(offset: Int, size: Int): Buffer {
-        fromByteArray(buf.array().copyOf(), endianness)
+        val newBuffer = withSize(size, endianness)
+        copyInto(newBuffer, destinationOffset = 0, offset, size.coerceAtMost(this.size - offset))
+        return newBuffer
+    }
+
+    actual fun copyInto(destination: Buffer, destinationOffset: Int, offset: Int, size: Int) {
+        require(offset >= 0 && offset <= this.size) {
+            "Offset $offset is out of bounds."
+        }
+        require(destinationOffset >= 0 && destinationOffset <= destination.size) {
+            "Destination offset $destinationOffset is out of bounds."
+        }
+        require(
+            size >= 0 &&
+                    destinationOffset + size <= destination.size &&
+                    offset + size <= this.size
+        ) {
+            "Size $size is out of bounds."
+        }
+
+        byteArray.copyInto(
+            destination.byteArray,
+            destinationOffset,
+            startIndex = offset,
+            endIndex = offset + size,
+        )
+    }
 
     /**
      * Checks whether we can read [size] bytes at [offset].