• David Howells's avatar
    X.509: Add simple ASN.1 grammar compiler · 4520c6a4
    David Howells authored
    Add a simple ASN.1 grammar compiler.  This produces a bytecode output that can
    be fed to a decoder to inform the decoder how to interpret the ASN.1 stream it
    is trying to parse.
    
    Action functions can be specified in the grammar by interpolating:
    
    	({ foo })
    
    after a type, for example:
    
    	SubjectPublicKeyInfo ::= SEQUENCE {
    		algorithm		AlgorithmIdentifier,
    		subjectPublicKey	BIT STRING ({ do_key_data })
    		}
    
    The decoder is expected to call these after matching this type and parsing the
    contents if it is a constructed type.
    
    The grammar compiler does not currently support the SET type (though it does
    support SET OF) as I can't see a good way of tracking which members have been
    encountered yet without using up extra stack space.
    
    Currently, the grammar compiler will fail if more than 256 bytes of bytecode
    would be produced or more than 256 actions have been specified as it uses
    8-bit jump values and action indices to keep space usage down.
    Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
    Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
    4520c6a4
asn1.h 1.96 KB