522 lines
13 KiB
Go
522 lines
13 KiB
Go
module bf
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/*
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bf (BitField) is a module (shared library for V programming language) for
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manipulating arrays of bits, i.e. series of zeroes and ones spread across an
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array of storage units (unsigned 32-bit integers).
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BitField structure
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------------------
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Bit arrays are stored in data structures called 'BitField'. The structure is
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'opaque', i.e. its internals are not available to the end user. This module
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provides API (functions and methods) for accessing and modifying bit arrays.
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*/
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struct BitField {
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mut:
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size int
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//field *u32
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field []u32
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}
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// helper functions
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const (
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SLOT_SIZE = 32
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)
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fn bitmask(bitnr int) u32 {
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return u32(u32(1) << u32(bitnr % SLOT_SIZE))
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}
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fn bitslot(size int) int {
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return size / SLOT_SIZE
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}
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fn bitget(instance BitField, bitnr int) int {
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return (instance.field[bitslot(bitnr)] >> u32(bitnr % SLOT_SIZE)) & 1
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}
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fn bitset(instance mut BitField, bitnr int) {
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instance.field[bitslot(bitnr)] = instance.field[bitslot(bitnr)] | bitmask(bitnr)
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}
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fn bitclear(instance mut BitField, bitnr int) {
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instance.field[bitslot(bitnr)] = instance.field[bitslot(bitnr)] & ~bitmask(bitnr)
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}
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fn bittoggle(instance mut BitField, bitnr int) {
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instance.field[bitslot(bitnr)] = instance.field[bitslot(bitnr)] ^ bitmask(bitnr)
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}
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/*
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#define BITTEST(a, b) ((a)->field[BITSLOT(b)] & BITMASK(b))
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*/
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fn min(input1 int, input2 int) int {
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if input1 < input2 {
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return input1
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}
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else {
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return input2
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}
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}
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fn bitnslots(length int) int {
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return (length - 1) / SLOT_SIZE + 1
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}
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fn cleartail(instance mut BitField) {
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tail := instance.size % SLOT_SIZE
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if tail != 0 {
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// create a mask for the tail
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mask := u32((1 << tail) - 1)
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// clear the extra bits
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instance.field[bitnslots(instance.size) - 1] = instance.field[bitnslots(instance.size) - 1] & mask
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}
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}
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// public functions
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// str2bf() converts a string of characters ('0' and '1') to a bit
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// array. Any character different from '0' is treated as '1'.
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pub fn str2bf(input string) BitField {
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mut output := new(input.len)
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for i := 0; i < input.len; i++ {
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if input[i] != 48 {
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output.setbit(i)
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}
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}
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return output
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}
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// string() converts the bit array to a string of characters ('0' and '1') and
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// return the string
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pub fn (input BitField) string() string {
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mut output := ''
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for i := 0; i < input.size; i++ {
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if input.getbit(i) == 1 {
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output = output + '1'
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}
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else {
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output = output + '0'
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}
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}
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return output
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}
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//new() creates an empty bit array of capable of storing 'size' bits.
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pub fn new(size int) BitField {
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output := BitField{
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size: size
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//field: *u32(calloc(bitnslots(size) * SLOT_SIZE / 8))
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field: [u32(0); bitnslots(size)]
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}
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return output
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}
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/*
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pub fn del(instance *BitField) {
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free(instance.field)
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free(instance)
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}
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*/
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// getbit() returns the value (0 or 1) of bit number 'bit_nr' (count from
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// 0)
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pub fn (instance BitField) getbit(bitnr int) int {
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if bitnr >= instance.size {return 0}
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return bitget(instance, bitnr)
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}
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// setbit() set bit number 'bit_nr' to 1 (count from 0)
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pub fn (instance mut BitField) setbit(bitnr int) {
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if bitnr >= instance.size {return}
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bitset(mut instance, bitnr)
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}
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// clearbit() clears (sets to zero) bit number 'bit_nr' (count from 0)
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pub fn (instance mut BitField) clearbit(bitnr int) {
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if bitnr >= instance.size {return}
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bitclear(mut instance, bitnr)
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}
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// setall() sets all bits in the array to 1
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pub fn (instance mut BitField) setall() {
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for i := 0; i < bitnslots(instance.size); i++ {
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instance.field[i] = u32(-1)
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}
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cleartail(mut instance)
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}
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// clearall() clears (sets to zero) all bits in the array
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pub fn (instance mut BitField) clearall() {
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for i := 0; i < bitnslots(instance.size); i++ {
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instance.field[i] = u32(0)
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}
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}
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// togglebit() change the value (from 0 to 1 or from 1 to 0) of bit
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// number 'bit_nr'
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pub fn (instance mut BitField) togglebit(bitnr int) {
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if bitnr >= instance.size {return}
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bittoggle(mut instance, bitnr)
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}
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// bfand() perform logical AND operation on every pair of bits from 'input1'
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// and 'input2' and return the result as a new array. If inputs differ in size,
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// the tail of the longer one is ignored.
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pub fn bfand(input1 BitField, input2 BitField) BitField {
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size := min(input1.size, input2.size)
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bitnslots := bitnslots(size)
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mut output := new(size)
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mut i := 0
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for i < bitnslots {
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output.field[i] = input1.field[i] & input2.field[i]
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i++
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}
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cleartail(mut output)
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return output
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}
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// bfnot() toggle all bits in a bit array and return the result as a new array
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pub fn bfnot(input BitField) BitField {
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size := input.size
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bitnslots := bitnslots(size)
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mut output := new(size)
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mut i := 0
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for i < bitnslots {
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output.field[i] = ~input.field[i]
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i++
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}
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cleartail(mut output)
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return output
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}
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// bfor() perform logical OR operation on every pair of bits from 'input1' and
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// 'input2' and return the result as a new array. If inputs differ in size, the
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// tail of the longer one is ignored.
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pub fn bfor(input1 BitField, input2 BitField) BitField {
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size := min(input1.size, input2.size)
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bitnslots := bitnslots(size)
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mut output := new(size)
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mut i := 0
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for i < bitnslots {
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output.field[i] = input1.field[i] | input2.field[i]
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i++
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}
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cleartail(mut output)
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return output
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}
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// bfxor(input1 BitField, input2 BitField) perform logical XOR operation on
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// every pair of bits from 'input1' and 'input2' and return the result as a new
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// array. If inputs differ in size, the tail of the longer one is ignored.
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pub fn bfxor(input1 BitField, input2 BitField) BitField {
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size := min(input1.size, input2.size)
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bitnslots := bitnslots(size)
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mut output := new(size)
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mut i := 0
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for i < bitnslots {
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output.field[i] = input1.field[i] ^ input2.field[i]
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i++
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}
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cleartail(mut output)
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return output
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}
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// join() concatenates two bit arrays and return the result as a new array.
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pub fn join(input1 BitField, input2 BitField) BitField {
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output_size := input1.size + input2.size
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mut output := new(output_size)
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// copy the first input to output as is
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for i := 0; i < bitnslots(input1.size); i++ {
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output.field[i] = input1.field[i]
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}
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// find offset bit and offset slot
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offset_bit := input1.size % SLOT_SIZE
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offset_slot := input1.size / SLOT_SIZE
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for i := 0; i < bitnslots(input2.size); i++ {
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output.field[i + offset_slot] =
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output.field[i + offset_slot] |
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u32(input2.field[i] << u32(offset_bit))
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}
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/*
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* If offset_bit is not zero, additional operations are needed.
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* Number of iterations depends on the nr of slots in output. Two
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* options:
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* (a) nr of slots in output is the sum of inputs' slots. In this
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* case, the nr of bits in the last slot of output is less than the
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* nr of bits in second input (i.e. ), OR
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* (b) nr of slots of output is the sum of inputs' slots less one
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* (i.e. less iterations needed). In this case, the nr of bits in
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* the last slot of output is greater than the nr of bits in second
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* input.
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* If offset_bit is zero, no additional copies needed.
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*/
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if (output_size - 1) % SLOT_SIZE < (input2.size - 1) % SLOT_SIZE {
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for i := 0; i < bitnslots(input2.size); i++ {
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output.field[i + offset_slot + 1] =
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output.field[i + offset_slot + 1] |
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u32(input2.field[i] >> u32(SLOT_SIZE - offset_bit))
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}
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} else if (output_size - 1) % SLOT_SIZE > (input2.size - 1) % SLOT_SIZE {
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for i := 0; i < bitnslots(input2.size) - 1; i++ {
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output.field[i + offset_slot + 1] =
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output.field[i + offset_slot + 1] |
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u32(input2.field[i] >> u32(SLOT_SIZE - offset_bit))
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}
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}
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return output
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}
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// print(instance BitField) send the content of a bit array to stdout as a
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// string of characters ('0' and '1').
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pub fn print(instance BitField) {
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mut i := 0
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for i < instance.size {
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if instance.getbit(i) == 1 {
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print('1')
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}
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else {
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print('0')
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}
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i++
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}
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}
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// getsize() returns the number of bits the array can hold
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pub fn (instance BitField) getsize() int {
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return instance.size
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}
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// clone() create a copy of a bit array
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pub fn clone(input BitField) BitField {
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bitnslots := bitnslots(input.size)
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mut output := new(input.size)
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mut i := 0
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for i < bitnslots {
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output.field[i] = input.field[i]
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i++
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}
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return output
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}
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// cmp() compare two bit arrays bit by bit and return 'true' if they are
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// identical by length and contents and 'false' otherwise.
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pub fn cmp(input1 BitField, input2 BitField) bool {
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if input1.size != input2.size {return false}
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for i := 0; i < bitnslots(input1.size); i++ {
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if input1.field[i] != input2.field[i] {return false}
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}
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return true
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}
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// popcount() returns the number of set bits (ones) in the array
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pub fn (instance BitField) popcount() int {
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size := instance.size
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bitnslots := bitnslots(size)
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tail := size % SLOT_SIZE
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mut count := 0
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for i := 0; i < bitnslots - 1; i++ {
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for j := 0; j < SLOT_SIZE; j++ {
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if u32(instance.field[i] >> u32(j)) & u32(1) == u32(1) {
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count++
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}
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}
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}
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for j := 0; j < tail; j++ {
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if u32(instance.field[bitnslots - 1] >> u32(j)) & u32(1) == u32(1) {
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count++
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}
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}
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return count
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}
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// hamming () compute the Hamming distance between two bit arrays.
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pub fn hamming (input1 BitField, input2 BitField) int {
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input_xored := bfxor(input1, input2)
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return input_xored.popcount()
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}
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// pos() checks if the array contains a sub-array 'needle' and returns its
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// position if it does, -1 if it does not, and -2 on error.
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pub fn (haystack BitField) pos(needle BitField) int {
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heystack_size := haystack.size
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needle_size := needle.size
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diff := heystack_size - needle_size
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// needle longer than haystack; return error code -2
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if diff < 0 {
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return -2
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}
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for i := 0; i <= diff; i++ {
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needle_candidate := haystack.slice(i, needle_size + i)
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if cmp(needle_candidate, needle) {
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// needle matches a sub-array of haystack; return starting position of the sub-array
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return i
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}
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}
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// nothing matched; return -1
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return -1
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}
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// slice() return a sub-array of bits between 'start_bit_nr' (included) and
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// 'end_bit_nr' (excluded)
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pub fn (input BitField) slice(_start int, _end int) BitField {
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// boundary checks
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mut start := _start
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mut end := _end
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if end > input.size {
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end = input.size // or panic?
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}
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if start > end {
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start = end // or panic?
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}
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mut output := new(end - start)
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start_offset := start % SLOT_SIZE
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end_offset := (end - 1) % SLOT_SIZE
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start_slot := start / SLOT_SIZE
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end_slot := (end - 1) / SLOT_SIZE
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output_slots := bitnslots(end - start)
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if output_slots > 1 {
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if start_offset != 0 {
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for i := 0; i < output_slots - 1; i++ {
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output.field[i] =
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u32(input.field[start_slot + i] >> u32(start_offset))
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output.field[i] = output.field[i] |
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u32(input.field[start_slot + i + 1] <<
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u32(SLOT_SIZE - start_offset))
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}
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}
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else {
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for i := 0; i < output_slots - 1; i++ {
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output.field[i] =
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u32(input.field[start_slot + i])
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}
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}
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}
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if start_offset > end_offset {
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output.field[(end - start - 1) / SLOT_SIZE] =
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u32(input.field[end_slot - 1] >> u32(start_offset))
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mut mask := u32((1 << (end_offset + 1)) - 1)
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mask = input.field[end_slot] & mask
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mask = u32(mask << u32(SLOT_SIZE - start_offset))
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output.field[(end - start - 1) / SLOT_SIZE] =
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output.field[(end - start - 1) / SLOT_SIZE] | mask
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}
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else if start_offset == 0 {
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mut mask := u32(0)
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if end_offset == SLOT_SIZE - 1 {
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mask = u32(-1)
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}
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else {
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mask = u32(u32(1) << u32(end_offset + 1))
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mask = mask - u32(1)
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}
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output.field[(end - start - 1) / SLOT_SIZE] =
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(input.field[end_slot] & mask)
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}
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else {
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mut mask := u32(((1 << (end_offset - start_offset + 1)) - 1) << start_offset)
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mask = input.field[end_slot] & mask
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mask = u32(mask >> u32(start_offset))
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output.field[(end - start - 1) / SLOT_SIZE] =
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output.field[(end - start - 1) / SLOT_SIZE] | mask
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}
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return output
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}
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// reverse() reverses the order of bits in the array (swap the first with the
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// last, the second with the last but one and so on)
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pub fn (instance mut BitField) reverse() BitField {
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size := instance.size
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bitnslots := bitnslots(size)
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mut output := new(size)
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for i:= 0; i < (bitnslots - 1); i++ {
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for j := 0; j < SLOT_SIZE; j++ {
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if u32(instance.field[i] >> u32(j)) & u32(1) == u32(1) {
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bitset(mut output, size - i * SLOT_SIZE - j - 1)
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}
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}
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}
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bits_in_last_input_slot := (size - 1) % SLOT_SIZE + 1
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for j := 0; j < bits_in_last_input_slot; j++ {
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if u32(instance.field[bitnslots - 1] >> u32(j)) & u32(1) == u32(1) {
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bitset(mut output, bits_in_last_input_slot - j - 1)
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}
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}
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return output
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}
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// resize() changes the size of the bit array to 'new_size'
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pub fn (instance mut BitField) resize(size int) {
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new_bitnslots := bitnslots(size)
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old_size := instance.size
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old_bitnslots := bitnslots(old_size)
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mut field := [u32(0); new_bitnslots]
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for i := 0; i < old_bitnslots && i < new_bitnslots; i++ {
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field[i] = instance.field[i]
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}
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instance.field = field
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instance.size = size
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if size < old_size && size % SLOT_SIZE != 0 {
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cleartail(mut instance)
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}
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}
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// rotate(offset int) circular-shift the bits by 'offset' positions (move
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// 'offset' bit to 0, 'offset+1' bit to 1, and so on)
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pub fn (instance BitField) rotate(offset int) BitField {
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/**
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* This function "cuts" the bitfield into two and swaps them.
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* If the offset is positive, the cutting point is counted from the
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* beginning of the bit array, otherwise from the end.
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**/
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size := instance.size
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// removing extra rotations
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mut offset_internal := offset % size
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if (offset_internal == 0) {
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// nothing to shift
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return instance
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}
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if offset_internal < 0 {
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offset_internal = offset_internal + size
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}
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first_chunk := instance.slice(0, offset_internal)
|
|
second_chunk := instance.slice(offset_internal, size)
|
|
output := join(second_chunk, first_chunk)
|
|
return output
|
|
}
|