Struct BankNumber 

pub struct BankNumber(/* private fields */);

Available on crate feature bank only.

A ROM bank number, held as a u8 or, under gb_wide_bank="mbc5", a u16.

It is a type rather than a plain integer so that the storage width stays out of every signature: how wide a bank number is, and how selecting one reaches the cartridge, is a property of the build. cargo-gb derives it from wide_banks in header.toml and passes --cfg gb_wide_bank; MAX is all that changes between modes.

gb_wide_bank	MAX	Bank register writes
unset	255	0x2000
"mbc1"	127	0x2000 (5 bits), 0x4000 (2 bits)
"mbc5"	511	0x3000 (bit 8), 0x2000 (low byte)

This is the widest number the build can carry. The cartridge’s own limit is tighter and gb-bank-pack enforces it at link time.

Wide banking and GBDK

GBDK reaches the bank register through its own one-byte shadow, exported here as _current_bank, and writes only 0x2000. "mbc1" keeps both, so linking gbdk-sys still works; the parts of GBDK that read the shadow (its far pointers, banked-call trampoline, and crash handler) would misread a bank above 31, and none of them are reachable from Rust. "mbc5" has no one-byte shadow to export, so a program linking gbdk-sys fails to link, and no interrupt handler may switch banks (see switch_bank).

Implementations

impl BankNumber

pub const MAX: u16 = 255

Available on neither gb_wide_bank=mbc1 nor gb_wide_bank=mbc5.

The highest bank number this build can represent.

pub const fn new(n: u16) -> BankNumber

Name a bank, rejecting one this build cannot represent.

In a const context an out-of-range number is a compile error.

pub const fn get(self) -> u16

The bank number, for a Mapper writing it to the cartridge.

Trait Implementations

impl Clone for BankNumber

fn clone(&self) -> BankNumber

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for BankNumber

impl Debug for BankNumber

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Eq for BankNumber

impl PartialEq for BankNumber

fn eq(&self, other: &BankNumber) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for BankNumber