#!/usr/bin/env zsh
# compat: -ash +bash -dash +zsh

sram() { ### @-
    ### convert between a couple saveram formats for N64 emulators.

    sram_crop() {
        tail -n +$((($1)/16+1))
    }

    sram_revend() {
        objcopy -I binary -O binary --reverse-bytes=4 "$@"
    }

    sram_dump() {
        xxd -ps -c 16 "$@"
    }

    sram_zeros() {
        # one row (16) of zeros
        yes "00000000000000000000000000000000" | head -n $1
    }

    game="$1"
    in="$2"
    out="$3"

    if [ "$game" = "mm" ]; then
        headsize=$((0x20800))
    elif [ "$game" = "oot" ]; then
        headsize=$((0x40800))
    else
        echo "Unknown game." >&2
        return 1
    fi

    [ -e "$2" ] || { echo -E "input save does not exist" >&2; return 1; }

    if [ "${in##*.}" = "SaveRAM" ]; then
        sram_dump "$in" | sram_crop $headsize | sram_dump -r > "$out"
    else
        cat <(sram_zeros $(($headsize/16))) <(sram_dump "$in") | sram_dump -r > "$out"
    fi

    sram_revend "$out"
}

[ -n "${preload+-}" ] || sram "$@"