ARROW-5714: [JS] Inconsistent behavior in Int64Builder with/without BigNum

- Use stride in `DataBufferBuilder.set` to ensure that Int64Builder is consistent with and without BigNum.
- Use `WideBufferBuilder` for `Int64` and `Uint64` builders, even when `BigInt` is not available. Moves check for `BigInt` availability into `WideBufferBuilder`. (Thanks to Paul Taylor)

Author: Brian Hulette <hulettbh@gmail.com>
Author: ptaylor <paul.e.taylor@me.com>

Closes apache#4691 from TheNeuralBit/js-data-buffer-builder-stride and squashes the following commits:

7862612 <Brian Hulette> Add clarifying comment for int64 generation in builder tests
b08ac1b <Brian Hulette> Merge pull request #3 from trxcllnt/js/data-buffer-builder-64bit-stride
2e4ce7a <Brian Hulette> Use stride in DataBufferBuilder.set
4567d07 <ptaylor> use WideBufferBuilder for Int64 and Uint64 builders
dc9ed3a <ptaylor> update package-lock.json

Author: TheNeuralBit

js/package-lock.json

@@ -16,13 +16,12 @@
 // under the License.
 
 import { memcpy } from '../util/buffer';
-import { BigInt64Array, BigUint64Array } from '../util/compat';
+import { BigIntAvailable, BigInt64Array, BigUint64Array } from '../util/compat';
 import {
     TypedArray, TypedArrayConstructor,
     BigIntArray, BigIntArrayConstructor
 } from '../interfaces';
 
-/** @ignore */ type WideArray<T extends BigIntArray> = T extends BigIntArray ? Int32Array : Uint32Array;
 /** @ignore */ type DataValue<T> = T extends TypedArray ? number : T extends BigIntArray ? WideValue<T> : T;
 /** @ignore */ type WideValue<T extends BigIntArray> = T extends BigIntArray ? bigint | Int32Array | Uint32Array : never;
 /** @ignore */ type ArrayCtor<T extends TypedArray | BigIntArray> =
@@ -105,7 +104,7 @@ export class DataBufferBuilder<T extends TypedArray> extends BufferBuilder<T, nu
     public get(index: number) { return this.buffer[index]; }
     public set(index: number, value: number) {
         this.reserve(index - this.length + 1);
-        this.buffer[index] = value;
+        this.buffer[index * this.stride] = value;
         return this;
     }
 }
@@ -157,16 +156,13 @@ export class OffsetsBufferBuilder extends DataBufferBuilder<Int32Array> {
 }
 
 /** @ignore */
-export class WideBufferBuilder<T extends BigIntArray> extends BufferBuilder<WideArray<T>, DataValue<T>> {
+export class WideBufferBuilder<T extends TypedArray, R extends BigIntArray> extends BufferBuilder<T, DataValue<T>> {
     // @ts-ignore
-    public buffer64: T;
+    public buffer64: R;
     // @ts-ignore
-    constructor(buffer: T, stride: number) {
-        const ArrayType = buffer instanceof BigInt64Array ? Int32Array : Uint32Array;
-        super(new ArrayType(buffer.buffer, buffer.byteOffset, buffer.byteLength / 4) as WideArray<T>, stride);
-    }
-    public get ArrayType64(): BigIntArrayConstructor<T> {
-        return this.buffer instanceof Int32Array ? BigInt64Array : BigUint64Array as any;
+    protected _ArrayType64: BigIntArrayConstructor<R>;
+    public get ArrayType64() {
+        return this._ArrayType64 || (this._ArrayType64 = <BigIntArrayConstructor<R>> (this.buffer instanceof Int32Array ? BigInt64Array : BigUint64Array));
     }
     public set(index: number, value: DataValue<T>) {
         this.reserve(index - this.length + 1);
@@ -180,7 +176,9 @@ export class WideBufferBuilder<T extends BigIntArray> extends BufferBuilder<Wide
     protected _resize(newLength: number) {
         const data = super._resize(newLength);
         const length = data.byteLength / (this.BYTES_PER_ELEMENT * this.stride);
-        this.buffer64 = new this.ArrayType64(data.buffer, data.byteOffset, length);
+        if (BigIntAvailable) {
+            this.buffer64 = new this.ArrayType64(data.buffer, data.byteOffset, length);
+        }
         return data;
     }
 }

js/src/builder/buffer.ts

@@ -17,9 +17,8 @@
 
 import { bignumToBigInt } from '../util/bn';
 import { WideBufferBuilder } from './buffer';
+import { BigInt64Array } from '../util/compat';
 import { FixedWidthBuilder, BuilderOptions } from '../builder';
-import { BigInt64ArrayAvailable, BigInt64Array } from '../util/compat';
-import { BigUint64ArrayAvailable, BigUint64Array } from '../util/compat';
 import { Int, Int8, Int16, Int32, Int64, Uint8, Uint16, Uint32, Uint64 } from '../type';
 
 /** @ignore */
@@ -37,16 +36,15 @@ export class Int16Builder<TNull = any> extends IntBuilder<Int16, TNull> {}
 export class Int32Builder<TNull = any> extends IntBuilder<Int32, TNull> {}
 /** @ignore */
 export class Int64Builder<TNull = any> extends IntBuilder<Int64, TNull> {
+    protected _values: WideBufferBuilder<Int32Array, BigInt64Array>;
     constructor(options: BuilderOptions<Int64, TNull>) {
         if (options['nullValues']) {
             options['nullValues'] = (options['nullValues'] as TNull[]).map(toBigInt);
         }
         super(options);
-        if (BigInt64ArrayAvailable) {
-            this._values = <any> new WideBufferBuilder(new BigInt64Array(0), 2);
-        }
+        this._values = new WideBufferBuilder(new Int32Array(0), 2);
     }
-    public get values64() { return (this._values as any).buffer64 as BigInt64Array; }
+    public get values64() { return this._values.buffer64; }
     public isValid(value: Int32Array | bigint | TNull) { return super.isValid(toBigInt(value)); }
 }
 
@@ -58,16 +56,15 @@ export class Uint16Builder<TNull = any> extends IntBuilder<Uint16, TNull> {}
 export class Uint32Builder<TNull = any> extends IntBuilder<Uint32, TNull> {}
 /** @ignore */
 export class Uint64Builder<TNull = any> extends IntBuilder<Uint64, TNull> {
+    protected _values: WideBufferBuilder<Uint32Array, BigUint64Array>;
     constructor(options: BuilderOptions<Uint64, TNull>) {
         if (options['nullValues']) {
             options['nullValues'] = (options['nullValues'] as TNull[]).map(toBigInt);
         }
         super(options);
-        if (BigUint64ArrayAvailable) {
-            this._values = <any> new WideBufferBuilder(new BigUint64Array(0), 2);
-        }
+        this._values = new WideBufferBuilder(new Uint32Array(0), 2);
     }
-    public get values64() { return (this._values as any).buffer64 as BigUint64Array; }
+    public get values64() { return this._values.buffer64; }
     public isValid(value: Uint32Array | bigint | TNull) { return super.isValid(toBigInt(value)); }
 }
 

js/src/builder/int.ts

@@ -53,15 +53,35 @@ export const int16sNoNulls = (length = 20) => Array.from(new Int16Array(randomBy
 export const int32sNoNulls = (length = 20) => Array.from(new Int32Array(randomBytes(length * Int32Array.BYTES_PER_ELEMENT).buffer));
 export const int64sNoNulls = (length = 20) => Array.from({ length }, (_, i) => {
     const bn = util.BN.new(new Int32Array(randomBytes(2 * 4).buffer));
-    return i % 3 === 0 ? bn : i % 2 === 0 ? bn[Symbol.toPrimitive]() : bn[0];
+    // Evenly distribute the three types of arguments we support in the Int64
+    // builder
+    switch (i % 3) {
+        // Int32Array (util.BN is-a Int32Array)
+        case 0: return bn;
+        // BigInt
+        case 1: return bn[Symbol.toPrimitive]()
+        // number
+        case 2:
+        default: return bn[0];
+    }
 });
 
 export const uint8sNoNulls = (length = 20) => Array.from(new Uint8Array(randomBytes(length * Uint8Array.BYTES_PER_ELEMENT).buffer));
 export const uint16sNoNulls = (length = 20) => Array.from(new Uint16Array(randomBytes(length * Uint16Array.BYTES_PER_ELEMENT).buffer));
 export const uint32sNoNulls = (length = 20) => Array.from(new Uint32Array(randomBytes(length * Uint32Array.BYTES_PER_ELEMENT).buffer));
 export const uint64sNoNulls = (length = 20) => Array.from({ length }, (_, i) => {
     const bn = util.BN.new(new Uint32Array(randomBytes(2 * 4).buffer));
-    return i % 3 === 0 ? bn : i % 2 === 0 ? bn[Symbol.toPrimitive]() : bn[0];
+    // Evenly distribute the three types of arguments we support in the Uint64
+    // builder
+    switch (i % 3) {
+        // UInt32Array (util.BN is-a Uint32Array)
+        case 0: return bn;
+        // BigInt
+        case 1: return bn[Symbol.toPrimitive]()
+        // number
+        case 2:
+        default: return bn[0];
+    }
 });
 export const float16sNoNulls = (length = 20) => Array.from(new Uint16Array(randomBytes(length * Uint16Array.BYTES_PER_ELEMENT).buffer)).map((x) => (x - 32767) / 32767);
 export const float32sNoNulls = (length = 20) => Array.from(new Float32Array(randomBytes(length * Float32Array.BYTES_PER_ELEMENT).buffer));