BF interpreter in bash

bf.bash

#!/bin/bash

tape=(0)
tape_index=0

tape_get() {
    echo ${tape[$tape_index]}
}

tape_inc() {
    local -i amount=$1
    local -i value=tape[$tape_index]
    ((value+=amount))
    tape[$tape_index]=$value
}

tape_move() {
    local -i amount=$1
    ((tape_index+=amount))
    while [ $tape_index -ge ${#tape[@]} ]; do
        tape+=(0)
        ((tape_length++))
    done
}

OP_INC=0
OP_MOVE=1
OP_LOOP=2
OP_PRINT=3

declare -i loop_var_count=0
declare -i string_index=0

filename=$1
contents=$(cat "$filename")

parse() {
    local ops_name=$1
    local op_values_name=$1_values
    declare -ga $ops_name
    declare -ga $op_values_name
    local -n __ops=$ops_name
    local -n __op_values=$op_values_name

    for ((; string_index < ${#contents}; string_index++)); do
        local char=${contents:string_index:1}

        case $char in
            +)
                __ops+=($OP_INC)
                __op_values+=(1)
                ;;
            -)
                __ops+=($OP_INC)
                __op_values+=(-1)
                ;;
            \>)
                __ops+=($OP_MOVE)
                __op_values+=(1)
                ;;
            \<)
                __ops+=($OP_MOVE)
                __op_values+=(-1)
                ;;
            .)
                __ops+=($OP_PRINT)
                __op_values+=(0)
                ;;
            \[)
                __ops+=($OP_LOOP)
                loop_var_name="__loop_ops_$((loop_var_count++))"
                __op_values+=($loop_var_name)
                ((string_index++))
                parse $loop_var_name
                ;;
            \])
                break
                ;;
        esac
    done
}


run() {
    local -n __ops=$1
    local -n __op_values=$1_values
    local ops=("${__ops[@]}")
    local op_values=("${__op_values[@]}")
    local value=

    for op in ${ops[@]}; do
        value="${op_values[0]}"
        op_values=("${op_values[@]:1}")

        case $op in
            $OP_INC)
                tape_inc $value
                ;;
            $OP_MOVE)
                tape_move $value
                ;;
            $OP_PRINT)
                printf "\x$(printf %x $(tape_get))"
                ;;
            $OP_LOOP)
                while [ $(tape_get) -ne 0 ]; do
                    run $value
                done
                ;;
        esac
    done
}

parse ops
run ops