# All files / lib/serialize F64.ts

68.18% Statements 60/88
52.63% Branches 20/38
80% Functions 28/35
68.6% Lines 59/86

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     import Decimal from 'decimal.js';

    /**
     * IEEE 754 double-precision floating-point number implementation
     *
     * Format: 1 bit sign + 11 bits exponent + 52 bits mantissa
     *
     * This class works directly with the binary representation to avoid
     * precision loss when serializing/deserializing f64 values to/from buffers.
     */
    export class F64 {
      private _buffer: Buffer; // 8 bytes storing the IEEE 754 representation

      /**
       * Create an F64 from raw bytes (IEEE 754 format)
       */
      constructor(buffer?: Buffer) {
        Eif (buffer) {
          if (buffer.length !== 8) {
            throw new Error('F64 buffer must be exactly 8 bytes');
          }
          this._buffer = Buffer.from(buffer);
        } else {
          this._buffer = Buffer.alloc(8);
        }
      }

      /**
       * Create F64 from JavaScript number
       */
      static fromNumber(num: number): F64 {
        const buffer = Buffer.alloc(8);
        buffer.writeDoubleBE(num, 0);
        return new F64(buffer);
      }

      /**
       * Create F64 from Decimal.js value
       * Uses the most precise conversion possible
       */
      static fromDecimal(decimal: Decimal): F64 {
        // Convert to number and let IEEE 754 handle the precision
        const num = decimal.toNumber();
        return F64.fromNumber(num);
      }

      /**
       * Create F64 from string representation
       * Uses Decimal.js to parse the string without precision loss from JavaScript Number
       */
      static fromString(str: string): F64 {
        // Parse string using Decimal.js to avoid JavaScript Number precision loss
        const decimal = new Decimal(str);
        return F64.fromDecimal(decimal);
      }

      /**
       * Create F64 from bigint (treating as integer value)
       */
      static fromBigInt(bigint: bigint): F64 {
        const num = Number(bigint);
        return F64.fromNumber(num);
      }

      /**
       * Create F64 representing zero (static method for API compatibility)
       */
      static zero(): F64 {
        return F64.fromNumber(0);
      }

      /**
       * Create F64 with specific IEEE 754 components
       */
      static fromComponents(
        sign: boolean,
        exponent: number,
        mantissa: bigint,
      ): F64 {
        if (exponent < 0 || exponent > 2047) {
          throw new Error('Exponent must be between 0 and 2047');
        }
        if (mantissa < BigInt(0) || mantissa >= BigInt(1) << BigInt(52)) {
          throw new Error('Mantissa must be between 0 and 2^52-1');
        }

        const buffer = Buffer.alloc(8);

        // Pack into 64-bit big-endian format
        // Bit layout: SEEEEEEE EEEEMMMM MMMMMMMM MMMMMMMM MMMMMMMM MMMMMMMM MMMMMMMM MMMMMMMM
        const signBit = sign ? BigInt(1) : BigInt(0);
        const expBits = BigInt(exponent);
        const mantissaBits = mantissa;

        const ieee754Bits =
          (signBit << BigInt(63)) | (expBits << BigInt(52)) | mantissaBits;

        // Write as big-endian bytes
        for (let i = 0; i < 8; i++) {
          const byteValue = Number(
            (ieee754Bits >> BigInt(56 - i * 8)) & BigInt(0xff),
          );
          buffer.writeUInt8(byteValue, i);
        }

        return new F64(buffer);
      }

      /**
       * Get the raw buffer containing IEEE 754 representation
       */
      getBuffer(): Buffer {
        return Buffer.from(this._buffer);
      }

      /**
       * Serialize to buffer (big-endian)
       */
      serialize(): Buffer {
        return this.getBuffer();
      }

      /**
       * Deserialize from buffer (big-endian)
       */
      static deserialize(buffer: Buffer): F64 {
        return new F64(buffer);
      }

      /**
       * Convert to JavaScript number
       * This may lose precision for very large or very precise values
       */
      toNumber(): number {
        return this._buffer.readDoubleBE(0);
      }

      /**
       * Convert to Decimal.js for arbitrary precision
       */
      toDecimal(): Decimal {
        return new Decimal(this.toNumber());
      }

      /**
       * Extract IEEE 754 components
       */
      getComponents(): { sign: boolean; exponent: number; mantissa: bigint } {
        // Read as big-endian 64-bit integer
        let ieee754Bits = BigInt(0);
        for (let i = 0; i < 8; i++) {
          ieee754Bits =
            (ieee754Bits << BigInt(8)) | BigInt(this._buffer.readUInt8(i));
        }

        const sign = (ieee754Bits & (BigInt(1) << BigInt(63))) !== BigInt(0);
        const exponent = Number((ieee754Bits >> BigInt(52)) & BigInt(0x7ff));
        const mantissa = ieee754Bits & ((BigInt(1) << BigInt(52)) - BigInt(1));

        return { sign, exponent, mantissa };
      }

      /**
       * Check if the value is finite
       */
      isFinite(): boolean {
        const { exponent } = this.getComponents();
        return exponent !== 2047; // NaN and Infinity have exponent = 2047
      }

      /**
       * Check if the value is NaN
       */
      isNaN(): boolean {
        const { exponent, mantissa } = this.getComponents();
        return exponent === 2047 && mantissa !== BigInt(0);
      }

      /**
       * Check if the value is infinite
       */
      isInfinite(): boolean {
        const { exponent, mantissa } = this.getComponents();
        return exponent === 2047 && mantissa === BigInt(0);
      }

      /**
       * Check if the value is zero
       */
      isZero(): boolean {
        const { exponent, mantissa } = this.getComponents();
        return exponent === 0 && mantissa === BigInt(0);
      }

      /**
       * Get string representation
       */
      toString(): string {
        return this.toNumber().toString();
      }

      /**
       * Convert to JSON-safe value: number if within safe range, string if too large
       * This preserves precision for very large numbers that exceed JavaScript's MAX_SAFE_INTEGER
       */
      toJSONValue(): number | string {
        const num = this.toNumber();

        // Check if the number is within JavaScript's safe integer range
        if (num <= Number.MAX_SAFE_INTEGER && num >= Number.MIN_SAFE_INTEGER) {
          return num;
        }

        // For very large numbers, return as string to preserve precision
        return num.toString();
      }

      /**
       * Create F64 from JSON value (handles both number and string inputs)
       */
      static fromJSONValue(value: number | string): F64 {
        if (typeof value === 'string') {
          return F64.fromString(value);
        } else {
          return F64.fromNumber(value);
        }
      }

      /**
       * Get hex representation of the raw bytes
       */
      toHex(): string {
        return this._buffer.toString('hex');
      }

      /**
       * Create F64 from hex string
       */
      static fromHex(hex: string): F64 {
        const buffer = Buffer.from(hex, 'hex');
        if (buffer.length !== 8) {
          throw new Error('Hex string must represent exactly 8 bytes');
        }
        return new F64(buffer);
      }

      /**
       * Compare with another F64
       */
      equals(other: F64): boolean {
        return this._buffer.equals(other._buffer);
      }

      /**
       * Equality comparison (alias for equals, for API compatibility)
       */
      eq(other: F64 | number): boolean {
        Eif (typeof other === 'number') {
          return this.toNumber() === other;
        }
        return this.equals(other);
      }

      /**
       * Greater than comparison
       */
      gt(other: F64 | number): boolean {
        if (typeof other === 'number') {
          return this.toNumber() > other;
        }
        return this.toNumber() > other.toNumber();
      }

      /**
       * Less than comparison
       */
      lt(other: F64 | number): boolean {
        if (typeof other === 'number') {
          return this.toNumber() < other;
        }
        return this.toNumber() < other.toNumber();
      }

      /**
       * Greater than or equal comparison
       */
      gte(other: F64 | number): boolean {
        if (typeof other === 'number') {
          return this.toNumber() >= other;
        }
        return this.toNumber() >= other.toNumber();
      }

      /**
       * Less than or equal comparison
       */
      lte(other: F64 | number): boolean {
        if (typeof other === 'number') {
          return this.toNumber() <= other;
        }
        return this.toNumber() <= other.toNumber();
      }

      /**
       * Create a copy
       */
      clone(): F64 {
        return new F64(this._buffer);
      }

      /**
       * Constants
       */
      static get ZERO(): F64 {
        return F64.fromNumber(0);
      }

      static get ONE(): F64 {
        return F64.fromNumber(1);
      }

      static get NEGATIVE_ONE(): F64 {
        return F64.fromNumber(-1);
      }

      static get INFINITY(): F64 {
        return F64.fromNumber(Number.POSITIVE_INFINITY);
      }

      static get NEGATIVE_INFINITY(): F64 {
        return F64.fromNumber(Number.NEGATIVE_INFINITY);
      }

      static get NaN(): F64 {
        return F64.fromNumber(Number.NaN);
      }
    }