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class npyjs {
constructor(opts) {
if (opts && !('convertFloat16' in opts)) {
console.warn([
"npyjs constructor now accepts {convertFloat16?: boolean}.",
"For usage, go to https://github.com/jhuapl-boss/npyjs."
].join(" "));
}
this.convertFloat16 = opts?.convertFloat16 ?? true;
this.dtypes = {
"<u1": {
name: "uint8",
size: 8,
arrayConstructor: Uint8Array,
},
"|u1": {
name: "uint8",
size: 8,
arrayConstructor: Uint8Array,
},
"<u2": {
name: "uint16",
size: 16,
arrayConstructor: Uint16Array,
},
"|i1": {
name: "int8",
size: 8,
arrayConstructor: Int8Array,
},
"<i2": {
name: "int16",
size: 16,
arrayConstructor: Int16Array,
},
"<u4": {
name: "uint32",
size: 32,
arrayConstructor: Uint32Array,
},
"<i4": {
name: "int32",
size: 32,
arrayConstructor: Int32Array,
},
"<u8": {
name: "uint64",
size: 64,
arrayConstructor: BigUint64Array,
},
"<i8": {
name: "int64",
size: 64,
arrayConstructor: BigInt64Array,
},
"<f4": {
name: "float32",
size: 32,
arrayConstructor: Float32Array
},
"<f8": {
name: "float64",
size: 64,
arrayConstructor: Float64Array
},
"<f2": {
name: "float16",
size: 16,
arrayConstructor: Uint16Array,
converter: this.convertFloat16 ? this.float16ToFloat32Array : undefined
},
};
}
float16ToFloat32Array(float16Array) {
const length = float16Array.length;
const float32Array = new Float32Array(length);
for (let i = 0; i < length; i++) {
float32Array[i] = npyjs.float16ToFloat32(float16Array[i]);
}
return float32Array;
}
static float16ToFloat32(float16) {
// Extract the parts of the float16
const sign = (float16 >> 15) & 0x1;
const exponent = (float16 >> 10) & 0x1f;
const fraction = float16 & 0x3ff;
// Handle special cases
if (exponent === 0) {
if (fraction === 0) {
// Zero
return sign ? -0 : 0;
}
// Denormalized number
return (sign ? -1 : 1) * Math.pow(2, -14) * (fraction / 0x400);
} else if (exponent === 0x1f) {
if (fraction === 0) {
// Infinity
return sign ? -Infinity : Infinity;
}
// NaN
return NaN;
}
// Normalized number
return (sign ? -1 : 1) * Math.pow(2, exponent - 15) * (1 + fraction / 0x400);
}
parse(arrayBufferContents) {
// const version = arrayBufferContents.slice(6, 8); // Uint8-encoded
const headerLength = new DataView(arrayBufferContents.slice(8, 10)).getUint8(0);
const offsetBytes = 10 + headerLength;
const hcontents = new TextDecoder("utf-8").decode(
new Uint8Array(arrayBufferContents.slice(10, 10 + headerLength))
);
const header = JSON.parse(
hcontents
.toLowerCase() // True -> true
.replace(/'/g, '"')
.replace("(", "[")
.replace(/,*\),*/g, "]")
);
const shape = header.shape;
const dtype = this.dtypes[header.descr];
if (!dtype) {
console.error(`Unsupported dtype: ${header.descr}`);
return null;
}
const nums = new dtype.arrayConstructor(
arrayBufferContents,
offsetBytes
);
// Convert float16 to float32 if converter exists
const data = dtype.converter ? dtype.converter.call(this, nums) : nums;
return {
dtype: dtype.name,
data: data,
shape,
fortranOrder: header.fortran_order
};
}
async load(filename, callback, fetchArgs) {
/*
Loads an array from a stream of bytes.
*/
fetchArgs = fetchArgs || {};
let arrayBuf;
// If filename is ArrayBuffer
if (filename instanceof ArrayBuffer) {
arrayBuf = filename;
}
// If filename is a file path
else {
const resp = await fetch(filename, { ...fetchArgs });
arrayBuf = await resp.arrayBuffer();
}
const result = this.parse(arrayBuf);
if (callback) {
return callback(result);
}
return result;
}
}
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