# PerlIO::via

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Write a PerlIO layer in Perl: open with `:via(MyClass)` and I/O dispatches to your class. This is a PerlIO layer implementation that delegates I/O operations to a Perl class. When a handle is opened with `:via(MyClass)`, each PerlIO vtable method (read, write, fill, flush, etc.) calls the corresponding Perl method on the class object (MyClass->WRITE, MyClass->READ, etc.). `via.xs` struct PerlIOVia extends \_PerlIO (base) with: stash — HV\* for the class package obj — SV\* the blessed object (or class name) var — SV\* buffer for FILL results cnt — SSize_t byte count remaining in var io — IO\* for the filehandle to layer below fh — SV\* reference to the GV wrapping io PUSHED..UTF8 — CV\* cached method lookups (one per via method) The MYMethod(x) macro expands to `"METHODNAME", &s->x` — passing both the string name and a pointer to the cached CV\* slot. The BOOT section registers the ”via“ PerlIO layer via PerlIO_define_layer. ## Functions ### Other Functions #### `pop_result` Pop a single SV result off the Perl stack (equivalent of SPAGAIN; POPs). Returns a p5api SV\*.