BitConverter.DoubleToInt64Bits() Method in C#

The BitConverter.DoubleToInt64Bits() method in C# converts a double-precision floating-point number to its 64-bit signed integer binary representation. This method is useful for examining the underlying binary structure of floating-point numbers or for low-level operations that require access to the raw bits.

Syntax

Following is the syntax for the DoubleToInt64Bits() method −

public static long DoubleToInt64Bits(double value);

Parameters

• value − The double-precision floating-point number to convert.

Return Value

Returns a 64-bit signed integer whose value is equivalent to the binary representation of the input double value.

Example 1: Converting Positive Double

using System;

public class Demo {
    public static void Main() {
        double d = 5.646587687;
        Console.WriteLine("Value = " + d);
        long res = BitConverter.DoubleToInt64Bits(d);
        Console.WriteLine("64-bit signed integer = " + res);
        
        // Convert back to verify
        double backToDouble = BitConverter.Int64BitsToDouble(res);
        Console.WriteLine("Converted back = " + backToDouble);
    }
}

The output of the above code is −

Value = 5.646587687
64-bit signed integer = 4618043510978159912
Converted back = 5.646587687

Example 2: Converting Small Double Values

using System;

public class Demo {
    public static void Main() {
        double d = 0.001;
        Console.WriteLine("Value = " + d);
        long res = BitConverter.DoubleToInt64Bits(d);
        Console.WriteLine("64-bit signed integer = " + res);
        
        // Display in hexadecimal for better understanding
        Console.WriteLine("Hexadecimal representation = 0x" + res.ToString("X"));
    }
}

The output of the above code is −

Value = 0.001
64-bit signed integer = 4562254508917369340
Hexadecimal representation = 0x3F50624DD2F1A9FC

Example 3: Special Double Values

using System;

public class Demo {
    public static void Main() {
        // Test special double values
        double[] values = { 0.0, -0.0, Double.PositiveInfinity, 
                           Double.NegativeInfinity, Double.NaN };
        
        foreach (double value in values) {
            long bits = BitConverter.DoubleToInt64Bits(value);
            Console.WriteLine($"Value: {value,20} | Bits: {bits,20}");
        }
    }
}

The output of the above code is −

Value:                    0 | Bits:                    0
Value:                    0 | Bits: -9223372036854775808
Value:             Infinity | Bits:  9218868437227405312
Value:            -Infinity | Bits: -4503599627370496
Value:                  NaN | Bits: -2251799813685248

Common Use Cases

• Binary analysis − Examining the IEEE 754 binary representation of floating-point numbers.

• Serialization − Converting doubles to integers for storage or transmission.

• Hash functions − Using the bit pattern of doubles in hash calculations.

• Low-level operations − Performing bitwise operations on floating-point data.

Conclusion

The BitConverter.DoubleToInt64Bits() method provides access to the raw binary representation of double-precision floating-point numbers as 64-bit signed integers. This method is essential for low-level programming tasks and understanding the underlying structure of IEEE 754 floating-point values.