Using DataView for reading from a buffer.

iwoplaza · Dec 17, 2024 · c3c6674 · c3c6674
1 parent adb99b7
commit c3c6674
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Showing 3 changed files with 28 additions and 32 deletions.
diff --git a/packages/typed-binary/src/io/bufferIOBase.ts b/packages/typed-binary/src/io/bufferIOBase.ts
@@ -14,13 +14,15 @@ export type BufferIOOptions = {
 };
 
 export class BufferIOBase {
+  protected readonly dataView: DataView;
   protected readonly uint8View: Uint8Array;
   protected readonly helperInt32View: Int32Array;
   protected readonly helperUint32View: Uint32Array;
   protected readonly helperUint16View: Uint16Array;
   protected readonly helperFloat32View: Float32Array;
   protected readonly helperByteView: Uint8Array;
   protected readonly switchEndianness: boolean;
+  protected readonly littleEndian: boolean;
 
   protected byteOffset = 0;
 
@@ -34,11 +36,13 @@ export class BufferIOBase {
     const systemEndianness = getSystemEndianness();
     this.endianness = endianness === 'system' ? systemEndianness : endianness;
     this.switchEndianness = this.endianness !== systemEndianness;
+    this.littleEndian = this.endianness === 'little';
 
     // Getting rid of the outer shell, which causes the Uint8Array line to create a copy, instead of a view.
     const unwrapped = unwrapBuffer(buffer);
     this.byteOffset += unwrapped.byteOffset;
 
+    this.dataView = new DataView(unwrapped.buffer);
     this.uint8View = new Uint8Array(unwrapped.buffer, 0);
 
     const helperBuffer = new ArrayBuffer(4);

diff --git a/packages/typed-binary/src/io/bufferReader.ts b/packages/typed-binary/src/io/bufferReader.ts
@@ -13,59 +13,52 @@ export class BufferReader extends BufferIOBase implements ISerialInput {
     return this._cachedTextDecoder;
   }
 
-  private copyInputToHelper(bytes: number) {
-    for (let i = 0; i < bytes; ++i) {
-      this.helperByteView[this.switchEndianness ? bytes - 1 - i : i] =
-        this.uint8View[this.byteOffset++];
-    }
-  }
-
   readBool() {
-    return this.uint8View[this.byteOffset++] !== 0;
+    return this.dataView.getUint8(this.byteOffset++) !== 0;
   }
 
   readByte() {
-    return this.uint8View[this.byteOffset++];
+    return this.dataView.getUint8(this.byteOffset++);
   }
 
   readFloat16() {
-    this.copyInputToHelper(2);
-
-    return float16ToNumber(this.helperUint16View);
+    const value = this.dataView.getUint16(this.byteOffset, this.littleEndian);
+    this.byteOffset += 2;
+    return float16ToNumber(value);
   }
 
   readFloat32() {
-    this.copyInputToHelper(4);
-
-    return this.helperFloat32View[0];
+    const value = this.dataView.getFloat32(this.byteOffset, this.littleEndian);
+    this.byteOffset += 4;
+    return value;
   }
 
   readInt32() {
-    this.copyInputToHelper(4);
-
-    return this.helperInt32View[0];
+    const value = this.dataView.getInt32(this.byteOffset, this.littleEndian);
+    this.byteOffset += 4;
+    return value;
   }
 
   readUint32() {
-    this.copyInputToHelper(4);
-
-    return this.helperUint32View[0];
+    const value = this.dataView.getUint32(this.byteOffset, this.littleEndian);
+    this.byteOffset += 4;
+    return value;
   }
 
   readString() {
     // Looking for the 'NULL' byte.
-    let end = this.byteOffset;
-    while (end < this.uint8View.byteLength) {
-      if (this.uint8View[end++] === 0) {
+    let strLength = 0;
+    while (this.byteOffset + strLength < this.dataView.byteLength) {
+      if (this.dataView.getUint8(this.byteOffset + strLength++) === 0) {
         break;
       }
     }
 
     const result = this._textDecoder.decode(
-      this.uint8View.subarray(this.byteOffset, end - 1),
+      new Uint8Array(this.dataView.buffer, this.byteOffset, strLength - 1),
     );
 
-    this.byteOffset = end;
+    this.byteOffset += strLength;
 
     return result;
   }
@@ -82,7 +75,7 @@ export class BufferReader extends BufferIOBase implements ISerialInput {
     );
 
     for (let i = 0; i < byteLength; ++i) {
-      destU8[i] = this.uint8View[this.byteOffset++];
+      destU8[i] = this.dataView.getUint8(this.byteOffset++);
     }
   }
 }
diff --git a/packages/typed-binary/src/io/float16converter.ts b/packages/typed-binary/src/io/float16converter.ts
@@ -17,11 +17,10 @@ export function numberToFloat16(value: number): Uint16Array {
   return uint16Array;
 }
 
-export function float16ToNumber(uint16Array: Uint16Array): number {
-  const float16 = uint16Array[0];
-  const sign = (float16 & 0x8000) >> 15;
-  const exponent = (float16 & 0x7c00) >> 10;
-  const mantissa = float16 & 0x3ff;
+export function float16ToNumber(uint16Encoding: number): number {
+  const sign = (uint16Encoding & 0x8000) >> 15;
+  const exponent = (uint16Encoding & 0x7c00) >> 10;
+  const mantissa = uint16Encoding & 0x3ff;
   if (exponent === 0) {
     return sign === 0 ? mantissa / 1024 : -mantissa / 1024;
   }