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Текущая директория: /usr/lib/node_modules/bitgo/node_modules/@polkadot/util/u8a
Просмотр файла: toBn.js
import { BN } from '../bn/bn.js';
/**
* @name u8aToBn
* @summary Creates a BN from a Uint8Array object.
* @description
* `UInt8Array` input values return the actual BN. `null` or `undefined` values returns an `0x0` value.
* @param value The value to convert
* @param options Options to pass while converting
* @param options.isLe Convert using Little Endian (default)
* @param options.isNegative Convert using two's complement
* @example
* <BR>
*
* ```javascript
* import { u8aToBn } from '@polkadot/util';
*
* u8aToHex(new Uint8Array([0x68, 0x65, 0x6c, 0x6c, 0xf])); // 0x68656c0f
* ```
*/
export function u8aToBn(value, { isLe = true, isNegative = false } = {}) {
// slice + reverse is expensive, however SCALE is LE by default so this is the path
// we are most interested in (the BE is added for the sake of being comprehensive)
if (!isLe) {
value = value.slice().reverse();
}
const count = value.length;
// shortcut for <= u48 values - in this case the manual conversion
// here seems to be more efficient than passing the full array
if (isNegative && count && (value[count - 1] & 0x80)) {
// Most common case i{8, 16, 32} default LE SCALE-encoded
// For <= 32, we also optimize the xor to a single op
switch (count) {
case 0:
return new BN(0);
case 1:
return new BN(((value[0] ^ 0x0000_00ff) * -1) - 1);
case 2:
return new BN((((value[0] + (value[1] << 8)) ^ 0x0000_ffff) * -1) - 1);
case 3:
return new BN((((value[0] + (value[1] << 8) + (value[2] << 16)) ^ 0x00ff_ffff) * -1) - 1);
case 4:
// for the 3rd byte, we don't << 24 - since JS converts all bitwise operators to
// 32-bit, in the case where the top-most bit is set this yields a negative value
return new BN((((value[0] + (value[1] << 8) + (value[2] << 16) + (value[3] * 0x1_00_00_00)) ^ 0xffff_ffff) * -1) - 1);
case 5:
return new BN(((((value[0] + (value[1] << 8) + (value[2] << 16) + (value[3] * 0x1_00_00_00)) ^ 0xffff_ffff) + ((value[4] ^ 0xff) * 0x1_00_00_00_00)) * -1) - 1);
case 6:
return new BN(((((value[0] + (value[1] << 8) + (value[2] << 16) + (value[3] * 0x1_00_00_00)) ^ 0xffff_ffff) + (((value[4] + (value[5] << 8)) ^ 0x0000_ffff) * 0x1_00_00_00_00)) * -1) - 1);
default:
return new BN(value, 'le').fromTwos(count * 8);
}
}
// Most common case - u{8, 16, 32} default LE SCALE-encoded
//
// There are some slight benefits in unrolling this specific loop,
// however it comes with diminishing returns since here the actual
// `new BN` does seem to take up the bulk of the time
switch (count) {
case 0:
return new BN(0);
case 1:
return new BN(value[0]);
case 2:
return new BN(value[0] + (value[1] << 8));
case 3:
return new BN(value[0] + (value[1] << 8) + (value[2] << 16));
case 4:
// for the 3rd byte, we don't << 24 - since JS converts all bitwise operators to
// 32-bit, in the case where the top-most bit is set this yields a negative value
return new BN(value[0] + (value[1] << 8) + (value[2] << 16) + (value[3] * 0x1_00_00_00));
case 5:
return new BN(value[0] + (value[1] << 8) + (value[2] << 16) + ((value[3] + (value[4] << 8)) * 0x1_00_00_00));
case 6:
return new BN(value[0] + (value[1] << 8) + (value[2] << 16) + ((value[3] + (value[4] << 8) + (value[5] << 16)) * 0x1_00_00_00));
default:
return new BN(value, 'le');
}
}
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