Your Brain Has Exploded

• That's a lot of fields
• Ignore xmg_* for now--that's deep magic (really)
• gsar: what the hell does xnv_nv do?
• shift is implemented with xof_off to avoid copying
• xav_array points to first element in Perl array
• xav_alloc points to start of real C array of SV *s
• xav_fill is highest index (like $#array)
• xav_max is maximum allocated size
• xav_arylen is $#array, created on demand