Using BNF syntax, you define one or more parse trees in your script.
Each parse tree has the form:
<root key>{<registry expression>}+
where:
<root key> ::= HKEY_CLASSES_ROOT | HKEY_CURRENT_USER |
HKEY_LOCAL_MACHINE | HKEY_USERS |
HKEY_PERFORMANCE_DATA | HKEY_DYN_DATA |
HKEY_CURRENT_CONFIG | HKCR | HKCU |
HKLM | HKU | HKPD | HKDD | HKCC
<registry expression> ::= <Add Key> | <Delete Key>
<Add Key> ::= [ForceRemove | NoRemove | val]<Key Name>
[<Key Value>][{< Add Key>}]
<Delete Key> ::= Delete<Key Name>
<Key Name> ::= '<AlphaNumeric>+'
<AlphaNumeric> ::= any character not NULL, i.e. ASCII 0
<Key Value> ::== <Key Type><Key Name>
<Key Type> ::= s | d
<Key Value> ::= '<AlphaNumeric>'
Note HKEY_CLASSES_ROOT and HKCR are equivalent; HKEY_CURRENT_USER and HKCU are equivalent; and so on.
A parse tree can add multiple keys and subkeys to the <root key>. In doing so, it keeps a subkey's handle open until the parser has completed parsing all its subkeys. This approach is more efficient than operating on a single key at a time, as seen in the following parse tree example:
HKEY_CLASSES_ROOT
{
'MyVeryOwnKey'
{
'HasASubKey'
{
'PrettyCool?'
}
}
}
Here, the Registrar initially opens (creates) HKEY_CLASSES_ROOT\MyVeryOwnKey. It then sees that MyVeryOwnKey has a subkey. Rather than close the key to MyVeryOwnKey, the Registrar retains the handle and opens (creates) HasASubKey using this parent handle. (The system registry can be slower when no parent handle is open.) Thus, opening HKEY_CLASSES_ROOT\MyVeryOwnKey and then opening HasASubKey with MyVeryOwnKey as the parent is faster than opening MyVeryOwnKey, closing MyVeryOwnKey, and then opening MyVeryOwnKey\HasASubKey.