191 lines
3.6 KiB
NASM
191 lines
3.6 KiB
NASM
// vim: filetype=kickass
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* = * "Day 01"
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//
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// day01
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//
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// Destroys:
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// a, x, y, $02..$04, $10..$1c, $20..$25, $fd..$fe, everything you've ever loved
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//
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.const input_pointer = $03
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.const buffer_pointer = $20
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.const atoi_result = $22
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.const outer_pointer = $20
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.const inner_pointer = $22
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.const remainder = $24
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// Need to be $03 and $fd due to multiply_16bit_unsigned
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.const outer_value = $26
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.const inner_value = $fd
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day01:
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move_16_imm($03, str_title)
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jsr write_string
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//
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// Parse the input at day01_input into an array of integers.
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//
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move_16_imm(input_pointer, day01_input)
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move_16_imm(buffer_pointer, buffer)
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ldy #0
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!line:
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// Create a temporary 16-bit integer to store the result in
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// in between digits.
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move_16_imm(atoi_result, 0)
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!digit:
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// Check for the newline character at the end of the line.
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lda (input_pointer), y
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cmp #'\n'
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beq !newline+
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// Multiply the stored number by 10.
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i16_mul10(atoi_result)
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// Subtract '0' from the current digit to convert it to "binary".
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lda (input_pointer), y
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sec
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sbc #'0'
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// Add the binary digit to the stored number
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i16_i8_add_a(atoi_result)
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// Increment y.
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iny
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bne !digit-
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// If y overflows, increment the MSB of the input pointer as well,
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// for a 16-bit increment.
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inc input_pointer + 1
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jmp !digit-
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!newline:
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sty zp_temp
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// Append the result of the conversion to the array.
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ldy #0
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lda atoi_result + 0
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sta (buffer_pointer), y
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iny
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lda atoi_result + 1
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sta (buffer_pointer), y
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// Increment the buffer pointer by 2.
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lda #2
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i16_i8_add_a(buffer_pointer)
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ldy zp_temp
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iny
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bne !+
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inc input_pointer + 1
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!:
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// Check for the null terminator.
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lda (input_pointer), y
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bne !line-
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move_16_imm($03, str_parse_done)
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jsr write_string
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move_16_imm(outer_pointer, buffer)
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// Add every number to every other number
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!outer:
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move_16_imm(inner_pointer, buffer)
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// $03..$04 = buffer[i]
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ldy #0
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lda (outer_pointer), y
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sta outer_value
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iny
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lda (outer_pointer), y
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sta outer_value + 1
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dey
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lda (outer_pointer), y
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bne !not_zero+
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iny
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lda (outer_pointer), y
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bne !not_zero+
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jmp !error+
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!not_zero:
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// Subtract from 2020 to see what number we need
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i16_imm_i16_sub(remainder, 2020, outer_value)
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!inner:
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// $fd..$fe = buffer[j]
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ldy #0
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lda (inner_pointer), y
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sta inner_value
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iny
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lda (inner_pointer), y
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sta inner_value + 1
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dey
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lda (inner_pointer), y
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bne !not_zero+
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iny
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lda (inner_pointer), y
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bne !not_zero+
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i16_inc(outer_pointer)
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jmp !outer-
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!not_zero:
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// j++
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lda #2
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i16_i8_add_a(inner_pointer)
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// Continue the loop if the number didn't match the needed number.
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i16_i16_cmp_bne(remainder, inner_value, !inner-)
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!done:
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// Multiply the results together
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sec
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jsr multiply_16bit_unsigned
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move_16_imm($03, str_calc_done)
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jsr write_string
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// Print the 32-bit result as decimal.
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lda $25
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sta udivmod32_dividend + 3
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lda $24
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sta udivmod32_dividend + 2
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lda $23
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sta udivmod32_dividend + 1
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lda $22
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sta udivmod32_dividend + 0
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jsr print_decimal_u32
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rts
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!error:
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move_16_imm($03, str_no_result)
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jsr write_string
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rts
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str_title:
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.text "# Day 01, part 1:"
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.byte '\n', 0
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str_parse_done:
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.text "* Finished parsing"
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.byte '\n', 0
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str_calc_done:
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.text "* Finished calculating"
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.byte '\n', 0
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str_no_result:
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.byte '\n'
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.text "! Could not find a result"
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.byte '\n', 0
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