Make a powershell version of asmdiff.sh

This version can be used with VSCode's built-in diff, and has better
error detection for new contributors.

asmdiff.ps1

@@ -0,0 +1,114 @@
+Param
+(
+    [Parameter(Position = 0)]
+    [string]$Start,
+
+    [Parameter(Position = 1)]
+    [string]$Offset,
+
+    [Parameter()]
+    [string[]]$DiffTool
+)
+
+$ErrorActionPreference = "Stop"
+
+$offset_default_value = "0x100"
+$diff_tool_default_value = "diff"
+
+$help = "
+$($args[0]) [OPTIONS] Start [Offset]
+
+Performs a diff on the assembly of a function in a rom. 'Start' is the start
+location of the function, and 'Offset' is the number of bytes to disassemble.
+The assembly is saved to *.dump files.
+
+'Offset' is optional, and defaults to $offset_default_value. If this value is
+very large (0x10000+), objdump may hang / freeze.
+
+Requirements:
+    - A clean copy of the rom named 'baserom.gba'.
+    - $$ENV:DEVKITARM to point to the installation of devkitpro. By default, it is
+      installed to 'C:\devkitpro\devkitARM'.
+
+Options:
+    -DiffTool <tool>   The tool to use for diffing. Defaults to '$diff_tool_default_value'. For VSCode,
+                       you can use -DiffTool 'code --diff'. (Quotes are necessary around 'code --diff')
+"
+
+if ((-not (Test-Path variable:Start)) -or [string]::IsNullOrWhiteSpace($Start))
+{
+    Write-Host $help
+    exit
+}
+
+if (-not (Test-Path variable:DiffTool) -or [string]::IsNullOrWhiteSpace($DiffTool))
+{
+    $DiffTool = $diff_tool_default_value
+}
+
+if (-not (Test-Path variable:Offset) -or [string]::IsNullOrWhiteSpace($Offset))
+{
+    $Offset = $offset_default_value
+}
+
+if (-Not (Test-Path env:DEVKITARM))
+{
+    Write-Host "ENV:DEVKITARM variable not set."
+    Write-Host $help
+    exit
+}
+
+if (-Not (Test-Path $env:DEVKITARM))
+{
+    Write-Host "DEVKITARM path '$env:DEVKITARM' does not exist."
+    Write-Host $help
+    exit
+}
+
+if (-Not (Test-Path ".\pokeemerald.gba"))
+{
+    Write-Host "File 'pokeemerald.gba' not found."
+    Write-Host $help
+    exit
+}
+
+if (-Not (Test-Path ".\baserom.gba"))
+{
+    Write-Host "File 'baserom.gba' not found."
+}
+
+try
+{
+    $start_num = [System.Convert]::ToUInt64($Start, 16)
+}
+catch
+{
+    Write-Host "Error parsing '$start_num' as a hex number."
+    Write-Host $help
+    exit
+}
+
+try
+{
+    $offset_num = [System.Convert]::ToUInt64($Offset, 16)
+}
+catch
+{
+    Write-Host "Error parsing '$offset_num' as a hex number."
+    Write-Host $help
+    exit
+}
+
+if ($start_num -gt 0x1000000)
+{
+    Write-Host "Warning: Start address is larger than the ROM file. Hint: ignore the leading number in the address."
+}
+
+$end_str = [System.Convert]::ToString($start_num + $offset_num, 16)
+$end_str = "0x$end_str"
+
+Write-Host "$Start - $end_str"
+$objdump = Join-Path -Path $env:DEVKITARM -ChildPath "arm-none-eabi\bin\objdump.exe"
+&$objdump -D -bbinary -marmv4t -Mforce-thumb --start-address="$Start" --stop-address="$end_str" .\baserom.gba > .\baserom.dump
+&$objdump -D -bbinary -marmv4t -Mforce-thumb --start-address="$Start" --stop-address="$end_str" .\pokeemerald.gba > .\pokeemerald.dump
+Invoke-Expression "$DiffTool .\baserom.dump .\pokeemerald.dump"