Parsing types
Spicy parsers are build up from smaller parsers, at the lowest level from basic types present in the input.
Currently Spicy supports parsing for the following basic types:
Fields not extracting any data can be marked void. They can still have hooks attached.
Since they are pervasive we give a brief overview for vectors here.
Parsing vectors
A common requirement is to parse vector of the same type, possibly of dynamic length.
To parse a vector of three integers we would write:
type X = unit {
xs: uint16[3];
};
If the number of elements is not known we can parse until the end of the input data. This will trigger a parse error if the input does not contain enough data to parse all elements.
type X = unit {
xs: uint16[] &eod;
};
If the vector is followed by e.g., a literal we can dynamically detect with lookahead parsing where the vector ends. The literal does not need to be a field, but could also be in another parser following the vector.
type X = unit {
xs: uint16[];
: b"\x00"; # Vector is terminated with null byte.
};
If the terminator is in the domain of the vector elements we can also use the
&until attribute.
type X = unit {
# Vector terminate with a null value
xs: uint8[] &until=$$==0;
};
If the vector elements require attributes themselves, we can pass them by grouping them with the element type.
type X = unit {
# Parse a vector of 8-byte integers less than 1024 until we find a null.
xs: (uint64 &requires=$$<1024)[] &until=$$==0;
};