example of using M0's get/set_byte ops

byte_ops.m0

.version 0
.chunk "byte_ops_test"
.constants
0 "string thing?"
1 "\n"
.metadata
.bytecode

    # print byte value of first byte of string 0
    set_imm S0, 0, 0
    deref S0, CONSTS, S0

    # print first (non-header) byte of S0
    set_imm I0, 0, 1
    set_imm I1, 0, 8
    get_byte I1, S0, I1
    print_i I0, I1, x

    # print newline
    set_imm S1, 0, 1
    deref S1, CONSTS, S1
    print_s I0, S1, x


    # print the length of the string and its encoding

    # print character count
    set_imm I1, 0, 0
    get_word I1, S0, I1
    print_i I0, I1, x
    print_s I0, S1, x

    # print encoding
    set_imm I1, 0, 1
    get_word I1, S0, I1
    print_i I0, I1, x
    print_s I0, S1, x


    # calculate the sum of the byte value of string 0

    # I1 = number of bytes in string
    # I2 = index (skipping header)
    # I3 = value of current byte
    # I4 = sum of bytes
    # I5 = 8 
    set_imm I1, 0, 0
    get_word I1, S0, I1
    set_imm I2, 0, 8
    set_imm I3, 0, 0
    set_imm I4, 0, 0
    set_imm I5, 0, 8

loop_start:

    # get value of current byte
    set I3, I2, x
    get_byte I3, S0, I3

    # add to total
    add_i I4, I4, I3

    # increment index
    add_i I2, I2, I0

    # goto loop_start unless index < I1+8
    add_i I6, I1, I5
    sub_i I6, I6, I2
    goto_if loop_start, I6

    # print the sum and a newline
    print_i I0, I4, x
    print_s I0, S1, x


    # create a copy of string 0, change "thing" to "thingy", free string


# This code isn't really PASM, but the highlighting works well.
# vim: expandtab shiftwidth=4 ft=pasm: