#requires -version 2

function Get-NetShare {
    <#
        .SYNOPSIS
        Gets share information for a specified server.

        Author: @harmj0y
        License: BSD 3-Clause
    
        .DESCRIPTION
        This function will execute the NetShareEnum Win32API call to query
        a given host for open shares. This is a replacement for
        "net share \\hostname"

        .PARAMETER HostName
        The hostname to query for shares.

        .OUTPUTS
        SHARE_INFO_1 structure. A representation of the SHARE_INFO_1
        result structure which includes the name and note for each share.

        .EXAMPLE
        > Get-NetShare
        Returns active shares on the local host.

        .EXAMPLE
        > Get-NetShare -HostName sqlserver
        Returns active shares on the 'sqlserver' host
    #>
    
    [CmdletBinding()]
    param(
        [string]
        $HostName = 'localhost'
    )
    
    If ($PSBoundParameters['Debug']) {
        $DebugPreference = 'Continue'
    }
    
    # arguments for NetShareEnum
    $QueryLevel = 1
    $ptrInfo = [IntPtr]::Zero
    $EntriesRead = 0
    $TotalRead = 0
    $ResumeHandle = 0

    # get the share information
    $Result = $Netapi32::NetShareEnum($HostName, $QueryLevel,[ref]$ptrInfo,-1,[ref]$EntriesRead,[ref]$TotalRead,[ref]$ResumeHandle)

    # Locate the offset of the initial intPtr
    $offset = $ptrInfo.ToInt64()
    
    Write-Debug "Get-NetShare result: $Result"
    
    # 0 = success
    if (($Result -eq 0) -and ($offset -gt 0)) {
        
        # Work out how mutch to increment the pointer by finding out the size of the structure
        $Increment = $SHARE_INFO_1::GetSize()
        
        # parse all the result structures
        for ($i = 0; ($i -lt $EntriesRead); $i++){
            # create a new int ptr at the given offset and cast 
            # the pointer as our result structure
            $newintptr = New-Object system.Intptr -ArgumentList $offset
            $Info = $newintptr -as $SHARE_INFO_1
            # return all the sections of the structure
            $Info | Select-Object *
            $offset = $newintptr.ToInt64()
            $offset += $increment
        }
        # free up the result buffer
        $Netapi32::NetApiBufferFree($ptrInfo) | Out-Null
    }
    else 
    {
        switch ($Result) {
            (5)           {Write-Debug 'The user does not have access to the requested information.'}
            (124)         {Write-Debug 'The value specified for the level parameter is not valid.'}
            (87)          {Write-Debug 'The specified parameter is not valid.'}
            (234)         {Write-Debug 'More entries are available. Specify a large enough buffer to receive all entries.'}
            (8)           {Write-Debug 'Insufficient memory is available.'}
            (2312)        {Write-Debug 'A session does not exist with the computer name.'}
            (2351)        {Write-Debug 'The computer name is not valid.'}
            (2221)        {Write-Debug 'Username not found.'}
            (53)          {Write-Debug 'Hostname could not be found'}
        }
    }
}

$Mod = New-InMemoryModule -ModuleName Win32

# all of the Win32 API functions we need
$FunctionDefinitions = @(
    (func netapi32 NetShareEnum ([Int]) @([string], [Int], [IntPtr].MakeByRefType(), [Int], [Int32].MakeByRefType(), [Int32].MakeByRefType(), [Int32].MakeByRefType())),
    (func netapi32 NetApiBufferFree ([Int]) @([IntPtr]))
)

# the NetShareEnum result structure
$SHARE_INFO_1 = struct $Mod SHARE_INFO_1 @{
    shi1_netname = field 0 String -MarshalAs @('LPWStr')
    shi1_type = field 1 UInt32
    shi1_remark = field 2 String -MarshalAs @('LPWStr')
}

$Types = $FunctionDefinitions | Add-Win32Type -Module $Mod -Namespace 'Win32'
$Netapi32 = $Types['netapi32']