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import type { U8aLike } from '../types.ts';
import { BN } from '../bn/index.ts';import { u8aToBn, u8aToU8a } from '../u8a/index.ts';
/** * @name compactFromU8a * @description Retrives the offset and encoded length from a compact-prefixed value * @example * <BR> * * ```javascript * import { compactFromU8a } from 'https://deno.land/x/polkadot@0.2.40/util/mod.ts'; * * const [offset, length] = compactFromU8a(new Uint8Array([254, 255, 3, 0])); * * console.log('value offset=', offset, 'length=', length); // 4, 0xffff * ``` */export function compactFromU8a (input: U8aLike): [number, BN] {  const u8a = u8aToU8a(input);
  // The u8a is manually converted here for 1, 2 & 4 lengths, it is 2x faster  // than doing an additional call to u8aToBn (as with variable length)  switch (u8a[0] & 0b11) {    case 0b00:      return [1, new BN(u8a[0] >>> 2)];
    case 0b01:      return [2, new BN((u8a[0] + (u8a[1] << 8)) >>> 2)];
    case 0b10:      // 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 [4, new BN((u8a[0] + (u8a[1] << 8) + (u8a[2] << 16) + (u8a[3] * 0x1_00_00_00)) >>> 2)];
    // 0b11    default: {      // add 5 to shifted (4 for base length, 1 for this byte)      const offset = (u8a[0] >>> 2) + 5;
      // we unroll the loop      switch (offset) {        // there still could be 4 bytes data, similar to 0b10 above (with offsets)        case 5:          // 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 [5, new BN(u8a[1] + (u8a[2] << 8) + (u8a[3] << 16) + (u8a[4] * 0x1_00_00_00))];
        case 6:          return [6, new BN(u8a[1] + (u8a[2] << 8) + (u8a[3] << 16) + ((u8a[4] + (u8a[5] << 8)) * 0x1_00_00_00))];
        // 6 bytes data is the maximum, 48 bits (56 would overflow)        case 7:          return [7, new BN(u8a[1] + (u8a[2] << 8) + (u8a[3] << 16) + ((u8a[4] + (u8a[5] << 8) + (u8a[6] << 16)) * 0x1_00_00_00))];
        // for anything else, use the non-unrolled version        default:          return [offset, u8aToBn(u8a.subarray(1, offset))];      }    }  }}
/** * @name compactFromU8aLim * @description A limited version of [[compactFromU8a]], accepting only Uint8Array inputs for values <= 48 bits */export function compactFromU8aLim (u8a: Uint8Array): [number, number] {  // The u8a is manually converted here for 1, 2 & 4 lengths, it is 2x faster  // than doing an additional call to u8aToBn (as with variable length)  switch (u8a[0] & 0b11) {    case 0b00:      return [1, u8a[0] >>> 2];
    case 0b01:      return [2, (u8a[0] + (u8a[1] << 8)) >>> 2];
    case 0b10:      // 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 [4, (u8a[0] + (u8a[1] << 8) + (u8a[2] << 16) + (u8a[3] * 0x1_00_00_00)) >>> 2];
    // 0b11    default: {      // add 5 to shifted (4 for base length, 1 for this byte)      // we unroll the loop      switch ((u8a[0] >>> 2) + 5) {        // there still could be 4 bytes data, similar to 0b10 above (with offsets)        case 5:          return [5, u8a[1] + (u8a[2] << 8) + (u8a[3] << 16) + (u8a[4] * 0x1_00_00_00)];
        case 6:          return [6, u8a[1] + (u8a[2] << 8) + (u8a[3] << 16) + ((u8a[4] + (u8a[5] << 8)) * 0x1_00_00_00)];
        // 6 bytes data is the maximum, 48 bits (56 would overflow)        case 7:          return [7, u8a[1] + (u8a[2] << 8) + (u8a[3] << 16) + ((u8a[4] + (u8a[5] << 8) + (u8a[6] << 16)) * 0x1_00_00_00)];
        // for anything else, we are above the actual MAX_SAFE_INTEGER - bail out        default:          throw new Error('Compact input is > Number.MAX_SAFE_INTEGER');      }    }  }}