Converting a large hexadecimal string to decimal

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The following hexadecimal value:

0x82e83f52d81253e79c4

is the following in base 10:

38636990646568762636740

If I try to convert it to a decimal:

[decimal] '0x82e83f52d81253e79c4'

I get the following:

Cannot convert value "0x82e83f52d81253e79c4" to type "System.Decimal". Error: "Input string was not in a correct format."

What's a good way to convert that large hexadecimal value in a string to a decimal?

powershell
1 Answers

Use [bigint]::Parse to parse the hexadecimal string as a BigInteger, then cast to [decimal]:

# define hex string
$string = '0x82e83f52d81253e79c4'

# remove 0x prefix
$string = $string -replace '^0x'

# prepend `0` to avoid having [bigint]::Parse interpret number as signed
$string = "0${string}"

# now parse it as a [bigint]
$bigint = [bigint]::Parse($string, [System.Globalization.NumberStyles]::AllowHexSpecifier)

# finally cast to `[decimal]`
[decimal]$bigint

This can easily be turned into a small utility function:

function ConvertFrom-Hexadecimal
{
  param(
    [Parameter(Mandatory)]
    [string]$Hexadecimal
  )

  $string = '0{0}' -f ($Hexadecimal -replace '^0x')

  return [decimal][bigint]::Parse($string, [System.Globalization.NumberStyles]::AllowHexSpecifier)
}

PS ~> $decimal = ConvertFrom-Hexadecimal '0x82e83f52d81253e79c4'
PS ~> $decimal -is [decimal]
True
PS ~> $decimal
38636990646568762636740
user_7126490
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