LegacyBinary =>
    00 byte[version] int16[n-sources] int32[member-size]
    Metadata*[n-sources][metadata]
    #Data*[n-sources][data]
    #Strings?

Metadata =>
    int32[n-values] int32[n-variables] int32[data-offset]
    byte*28[source-name]
    vB0(byte*36[ext-source-name] int32[x])

#Data => Variable*[n-variables]
#Variable => byte*288[variable-name] double*[n-values]

Strings => SourceMaps[maps] Labels

SourceMaps => int32[n-maps] SourceMap*[n-maps]
SourceMap => string[source-name] int32[n-variables] VariableMap*[n-variables]
VariableMap => string[variable-name] int32[n-data] DatumMap*[n-data]
DatumMap => int32[value-idx] int32[label-idx]

Labels => int32[n-labels] Label*[n-labels]
Label => int32[frequency] string[label]