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v/vlib/bf/bf.v

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module bf
struct BitField {
mut:
size int
//field *u32
field []u32
}
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// helper functions
const (
SLOT_SIZE = 32
)
fn bitmask(bitnr int) u32 {
return u32(u32(1) << u32(bitnr % SLOT_SIZE))
}
fn bitslot(size int) int {
return size / SLOT_SIZE
}
fn bitget(instance BitField, bitnr int) int {
return (instance.field[bitslot(bitnr)] >> u32(bitnr % SLOT_SIZE)) & 1
}
fn bitset(instance BitField, bitnr int) {
instance.field[bitslot(bitnr)] = instance.field[bitslot(bitnr)] | bitmask(bitnr)
}
fn bitclear(instance BitField, bitnr int) {
instance.field[bitslot(bitnr)] = instance.field[bitslot(bitnr)] & ~bitmask(bitnr)
}
fn bittoggle(instance BitField, bitnr int) {
instance.field[bitslot(bitnr)] = instance.field[bitslot(bitnr)] ^ bitmask(bitnr)
}
/*
#define BITTEST(a, b) ((a)->field[BITSLOT(b)] & BITMASK(b))
*/
fn min(input1 int, input2 int) int {
if input1 < input2 {
return input1
}
else {
return input2
}
}
fn bitnslots(length int) int {
return (length - 1) / SLOT_SIZE + 1
}
fn cleartail(instance BitField) {
tail := instance.size % SLOT_SIZE
if tail != 0 {
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// create a mask for the tail
mask := u32((1 << tail) - 1)
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// clear the extra bits
instance.field[bitnslots(instance.size) - 1] = instance.field[bitnslots(instance.size) - 1] & mask
}
}
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// public functions
pub fn new(size int) BitField {
output := BitField{
size: size
//field: *u32(calloc(bitnslots(size) * SLOT_SIZE / 8))
field: [u32(0); bitnslots(size)]
}
return output
}
/*
pub fn del(instance *BitField) {
free(instance.field)
free(instance)
}
*/
pub fn (instance BitField) getbit(bitnr int) int {
if bitnr >= instance.size {return 0}
return bitget(instance, bitnr)
}
pub fn (instance mut BitField) setbit(bitnr int) {
if bitnr >= instance.size {return}
bitset(instance, bitnr)
}
pub fn (instance mut BitField) clearbit(bitnr int) {
if bitnr >= instance.size {return}
bitclear(instance, bitnr)
}
pub fn (instance mut BitField) togglebit(bitnr int) {
if bitnr >= instance.size {return}
bittoggle(instance, bitnr)
}
pub fn bfand(input1 BitField, input2 BitField) BitField {
size := min(input1.size, input2.size)
bitnslots := bitnslots(size)
mut output := new(size)
mut i := 0
for i < bitnslots {
output.field[i] = input1.field[i] & input2.field[i]
i++
}
cleartail(output)
return output
}
pub fn bfnot(input BitField) BitField {
size := input.size
bitnslots := bitnslots(size)
mut output := new(size)
mut i := 0
for i < bitnslots {
output.field[i] = ~input.field[i]
i++
}
cleartail(output)
return output
}
pub fn bfor(input1 BitField, input2 BitField) BitField {
size := min(input1.size, input2.size)
bitnslots := bitnslots(size)
mut output := new(size)
mut i := 0
for i < bitnslots {
output.field[i] = input1.field[i] | input2.field[i]
i++
}
cleartail(output)
return output
}
pub fn bfxor(input1 BitField, input2 BitField) BitField {
size := min(input1.size, input2.size)
bitnslots := bitnslots(size)
mut output := new(size)
mut i := 0
for i < bitnslots {
output.field[i] = input1.field[i] ^ input2.field[i]
i++
}
cleartail(output)
return output
}
pub fn join(input1 BitField, input2 BitField) BitField {
output_size := input1.size + input2.size
mut output := new(output_size)
// copy the first input to output as is
for i := 0; i < bitnslots(input1.size); i++ {
output.field[i] = input1.field[i]
}
// find offset bit and offset slot
offset_bit := input1.size % SLOT_SIZE
offset_slot := input1.size / SLOT_SIZE
for i := 0; i < bitnslots(input2.size); i++ {
output.field[i + offset_slot] =
output.field[i + offset_slot] |
u32(input2.field[i] << u32(offset_bit))
}
/*
* If offset_bit is not zero, additional operations are needed.
* Number of iterations depends on the nr of slots in output. Two
* options:
* (a) nr of slots in output is the sum of inputs' slots. In this
* case, the nr of bits in the last slot of output is less than the
* nr of bits in second input (i.e. ), OR
* (b) nr of slots of output is the sum of inputs' slots less one
* (i.e. less iterations needed). In this case, the nr of bits in
* the last slot of output is greater than the nr of bits in second
* input.
* If offset_bit is zero, no additional copies needed.
*/
if (output_size - 1) % SLOT_SIZE < (input2.size - 1) % SLOT_SIZE {
for i := 0; i < bitnslots(input2.size); i++ {
output.field[i + offset_slot + 1] =
output.field[i + offset_slot + 1] |
u32(input2.field[i] >> u32(SLOT_SIZE - offset_bit))
}
} else if (output_size - 1) % SLOT_SIZE > (input2.size - 1) % SLOT_SIZE {
for i := 0; i < bitnslots(input2.size) - 1; i++ {
output.field[i + offset_slot + 1] =
output.field[i + offset_slot + 1] |
u32(input2.field[i] >> u32(SLOT_SIZE - offset_bit))
}
}
return output
}
pub fn print(instance BitField) {
mut i := 0
for i < instance.size {
if instance.getbit(i) == 1 {
print('1')
}
else {
print('0')
}
i++
}
}
pub fn (instance BitField) getsize() int {
return instance.size
}
pub fn clone(input BitField) BitField {
bitnslots := bitnslots(input.size)
mut output := new(input.size)
mut i := 0
for i < bitnslots {
output.field[i] = input.field[i]
i++
}
return output
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}
pub fn cmp(input1 BitField, input2 BitField) bool {
if input1.size != input2.size {return false}
for i := 0; i < bitnslots(input1.size); i++ {
if input1.field[i] != input2.field[i] {return false}
}
return true
}
pub fn (instance BitField) popcount() int {
size := instance.size
bitnslots := bitnslots(size)
tail := size % SLOT_SIZE
mut count := 0
for i := 0; i < bitnslots - 1; i++ {
for j := 0; j < SLOT_SIZE; j++ {
if u32(instance.field[i] >> u32(j)) & u32(1) == u32(1) {
count++
}
}
}
for j := 0; j < tail; j++ {
if u32(instance.field[bitnslots - 1] >> u32(j)) & u32(1) == u32(1) {
count++
}
}
return count
}
pub fn hamming (input1 BitField, input2 BitField) int {
input_xored := bfxor(input1, input2)
return input_xored.popcount()
}
pub fn (input BitField) slice(_start int, _end int) BitField {
// boundary checks
mut start := _start
mut end := _end
if end > input.size {
end = input.size // or panic?
}
if start > end {
start = end // or panic?
}
mut output := new(end - start)
start_offset := start % SLOT_SIZE
end_offset := (end - 1) % SLOT_SIZE
start_slot := start / SLOT_SIZE
end_slot := (end - 1) / SLOT_SIZE
output_slots := bitnslots(end - start)
if output_slots > 1 {
if start_offset != 0 {
for i := 0; i < output_slots - 1; i++ {
output.field[i] =
u32(input.field[start_slot + i] >> u32(start_offset))
output.field[i] = output.field[i] |
u32(input.field[start_slot + i + 1] <<
u32(SLOT_SIZE - start_offset))
}
}
else {
for i := 0; i < output_slots - 1; i++ {
output.field[i] =
u32(input.field[start_slot + i])
}
}
}
if start_offset > end_offset {
output.field[(end - start - 1) / SLOT_SIZE] =
u32(input.field[end_slot - 1] >> u32(start_offset))
mut mask := u32((1 << (end_offset + 1)) - 1)
mask = input.field[end_slot] & mask
mask = u32(mask << u32(SLOT_SIZE - start_offset))
output.field[(end - start - 1) / SLOT_SIZE] =
output.field[(end - start - 1) / SLOT_SIZE] | mask
}
else if start_offset == 0 {
mut mask := u32(0)
if end_offset == SLOT_SIZE - 1 {
mask = u32(-1)
}
else {
mask = u32(u32(1) << u32(end_offset + 1))
mask = mask - u32(1)
}
output.field[(end - start - 1) / SLOT_SIZE] =
(input.field[end_slot] & mask)
}
else {
mut mask := u32(((1 << (end_offset - start_offset + 1)) - 1) << start_offset)
mask = input.field[end_slot] & mask
mask = u32(mask >> u32(start_offset))
output.field[(end - start - 1) / SLOT_SIZE] =
output.field[(end - start - 1) / SLOT_SIZE] | mask
}
return output
}