685 lines
18 KiB
V
685 lines
18 KiB
V
module sync
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import time
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import rand
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$if windows {
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#flag -I @VROOT/thirdparty/stdatomic/win
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} $else {
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#flag -I @VROOT/thirdparty/stdatomic/nix
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}
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$if linux {
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$if tinyc {
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// most Linux distributions have /usr/lib/libatomic.so, but Ubuntu uses gcc version specific dir
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#flag -L/usr/lib/gcc/x86_64-linux-gnu/6
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#flag -L/usr/lib/gcc/x86_64-linux-gnu/7
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#flag -L/usr/lib/gcc/x86_64-linux-gnu/8
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#flag -L/usr/lib/gcc/x86_64-linux-gnu/9
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#flag -L/usr/lib/gcc/x86_64-linux-gnu/10
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#flag -L/usr/lib/gcc/x86_64-linux-gnu/11
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#flag -L/usr/lib/gcc/x86_64-linux-gnu/12
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#flag -latomic
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}
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}
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#include <atomic.h>
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// The following functions are actually generic in C
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fn C.atomic_load_ptr(voidptr) voidptr
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fn C.atomic_store_ptr(voidptr, voidptr)
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fn C.atomic_compare_exchange_weak_ptr(voidptr, voidptr, voidptr) bool
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fn C.atomic_compare_exchange_strong_ptr(voidptr, voidptr, voidptr) bool
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fn C.atomic_exchange_ptr(voidptr, voidptr) voidptr
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fn C.atomic_fetch_add_ptr(voidptr, voidptr) voidptr
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fn C.atomic_fetch_sub_ptr(voidptr, voidptr) voidptr
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fn C.atomic_load_u16(voidptr) u16
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fn C.atomic_store_u16(voidptr, u16)
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fn C.atomic_compare_exchange_weak_u16(voidptr, voidptr, u16) bool
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fn C.atomic_compare_exchange_strong_u16(voidptr, voidptr, u16) bool
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fn C.atomic_exchange_u16(voidptr, u16) u16
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fn C.atomic_fetch_add_u16(voidptr, u16) u16
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fn C.atomic_fetch_sub_u16(voidptr, u16) u16
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fn C.atomic_load_u32(voidptr) u32
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fn C.atomic_store_u32(voidptr, u32)
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fn C.atomic_compare_exchange_weak_u32(voidptr, voidptr, u32) bool
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fn C.atomic_compare_exchange_strong_u32(voidptr, voidptr, u32) bool
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fn C.atomic_exchange_u32(voidptr, u32) u32
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fn C.atomic_fetch_add_u32(voidptr, u32) u32
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fn C.atomic_fetch_sub_u32(voidptr, u32) u32
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fn C.atomic_load_u64(voidptr) u64
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fn C.atomic_store_u64(voidptr, u64)
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fn C.atomic_compare_exchange_weak_u64(voidptr, voidptr, u64) bool
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fn C.atomic_compare_exchange_strong_u64(voidptr, voidptr, u64) bool
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fn C.atomic_exchange_u64(voidptr, u64) u64
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fn C.atomic_fetch_add_u64(voidptr, u64) u64
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fn C.atomic_fetch_sub_u64(voidptr, u64) u64
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const (
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// how often to try to get data without blocking before to wait for semaphore
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spinloops = 750
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spinloops_sem = 4000
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)
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enum BufferElemStat {
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unused = 0
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writing
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written
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reading
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}
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struct Subscription {
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mut:
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sem &Semaphore
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prev &&Subscription
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nxt &Subscription
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}
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enum Direction {
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pop
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push
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}
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struct Channel {
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ringbuf &byte // queue for buffered channels
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statusbuf &byte // flags to synchronize write/read in ringbuf
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objsize u32
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mut: // atomic
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writesem Semaphore // to wake thread that wanted to write, but buffer was full
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readsem Semaphore // to wake thread that wanted to read, but buffer was empty
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writesem_im Semaphore
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readsem_im Semaphore
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write_adr C.atomic_uintptr_t // if != NULL the next obj can be written here without wait
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read_adr C.atomic_uintptr_t // if != NULL an obj can be read from here without wait
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adr_read C.atomic_uintptr_t // used to identify origin of writesem
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adr_written C.atomic_uintptr_t // used to identify origin of readsem
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write_free u32 // for queue state
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read_avail u32
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buf_elem_write_idx u32
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buf_elem_read_idx u32
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// for select
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write_subscriber &Subscription
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read_subscriber &Subscription
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write_sub_mtx u16
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read_sub_mtx u16
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closed u16
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pub:
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cap u32 // queue length in #objects
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}
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pub fn new_channel<T>(n u32) &Channel {
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st := sizeof(T)
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return new_channel_st(n, st)
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}
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fn new_channel_st(n u32, st u32) &Channel {
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wsem := if n > 0 { n } else { 1 }
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rsem := if n > 0 { u32(0) } else { 1 }
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rbuf := if n > 0 { unsafe { malloc(int(n * st)) } } else { &byte(0) }
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sbuf := if n > 0 { vcalloc(int(n * 2)) } else { &byte(0) }
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mut ch := &Channel{
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objsize: st
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cap: n
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write_free: n
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read_avail: 0
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ringbuf: rbuf
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statusbuf: sbuf
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write_subscriber: 0
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read_subscriber: 0
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}
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ch.writesem.init(wsem)
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ch.readsem.init(rsem)
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ch.writesem_im.init(0)
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ch.readsem_im.init(0)
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return ch
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}
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pub fn (mut ch Channel) close() {
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open_val := u16(0)
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if !C.atomic_compare_exchange_strong_u16(&ch.closed, &open_val, 1) {
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return
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}
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mut nulladr := voidptr(0)
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for !C.atomic_compare_exchange_weak_ptr(unsafe { &voidptr(&ch.adr_written) }, &nulladr,
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voidptr(-1)) {
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nulladr = voidptr(0)
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}
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ch.readsem_im.post()
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ch.readsem.post()
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mut null16 := u16(0)
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for !C.atomic_compare_exchange_weak_u16(&ch.read_sub_mtx, &null16, u16(1)) {
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null16 = u16(0)
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}
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if ch.read_subscriber != voidptr(0) {
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ch.read_subscriber.sem.post()
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}
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C.atomic_store_u16(&ch.read_sub_mtx, u16(0))
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null16 = u16(0)
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for !C.atomic_compare_exchange_weak_u16(&ch.write_sub_mtx, &null16, u16(1)) {
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null16 = u16(0)
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}
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if ch.write_subscriber != voidptr(0) {
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ch.write_subscriber.sem.post()
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}
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C.atomic_store_u16(&ch.write_sub_mtx, u16(0))
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ch.writesem.post()
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if ch.cap == 0 {
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C.atomic_store_ptr(unsafe { &voidptr(&ch.read_adr) }, voidptr(0))
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}
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ch.writesem_im.post()
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}
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[inline]
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pub fn (mut ch Channel) len() int {
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return int(C.atomic_load_u32(&ch.read_avail))
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}
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[inline]
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pub fn (mut ch Channel) closed() bool {
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return C.atomic_load_u16(&ch.closed) != 0
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}
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[inline]
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pub fn (mut ch Channel) push(src voidptr) {
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if ch.try_push_priv(src, false) == .closed {
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panic('push on closed channel')
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}
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}
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[inline]
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pub fn (mut ch Channel) try_push(src voidptr) ChanState {
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return ch.try_push_priv(src, true)
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}
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fn (mut ch Channel) try_push_priv(src voidptr, no_block bool) ChanState {
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if C.atomic_load_u16(&ch.closed) != 0 {
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return .closed
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}
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spinloops_sem_, spinloops_ := if no_block { 1, 1 } else { sync.spinloops, sync.spinloops_sem }
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mut have_swapped := false
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for {
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mut got_sem := false
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mut wradr := C.atomic_load_ptr(unsafe { &voidptr(&ch.write_adr) })
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for wradr != C.NULL {
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if C.atomic_compare_exchange_strong_ptr(unsafe { &voidptr(&ch.write_adr) },
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&wradr, voidptr(0))
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{
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// there is a reader waiting for us
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unsafe { C.memcpy(wradr, src, ch.objsize) }
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mut nulladr := voidptr(0)
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for !C.atomic_compare_exchange_weak_ptr(unsafe { &voidptr(&ch.adr_written) },
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&nulladr, wradr) {
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nulladr = voidptr(0)
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}
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ch.readsem_im.post()
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return .success
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}
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}
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if no_block && ch.cap == 0 {
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return .not_ready
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}
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// get token to read
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for _ in 0 .. spinloops_sem_ {
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if got_sem {
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break
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}
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got_sem = ch.writesem.try_wait()
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}
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if !got_sem {
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if no_block {
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return .not_ready
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}
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ch.writesem.wait()
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}
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if C.atomic_load_u16(&ch.closed) != 0 {
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ch.writesem.post()
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return .closed
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}
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if ch.cap == 0 {
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// try to advertise current object as readable
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mut read_in_progress := false
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C.atomic_store_ptr(unsafe { &voidptr(&ch.read_adr) }, src)
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wradr = C.atomic_load_ptr(unsafe { &voidptr(&ch.write_adr) })
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if wradr != C.NULL {
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mut src2 := src
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if C.atomic_compare_exchange_strong_ptr(unsafe { &voidptr(&ch.read_adr) },
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&src2, voidptr(0))
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{
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ch.writesem.post()
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continue
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} else {
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read_in_progress = true
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}
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}
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if !read_in_progress {
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mut null16 := u16(0)
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for !C.atomic_compare_exchange_weak_u16(voidptr(&ch.read_sub_mtx), &null16,
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u16(1)) {
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null16 = u16(0)
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}
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if ch.read_subscriber != voidptr(0) {
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ch.read_subscriber.sem.post()
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}
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C.atomic_store_u16(&ch.read_sub_mtx, u16(0))
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}
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mut src2 := src
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for sp := u32(0); sp < spinloops_ || read_in_progress; sp++ {
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if C.atomic_compare_exchange_strong_ptr(unsafe { &voidptr(&ch.adr_read) },
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&src2, voidptr(0))
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{
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have_swapped = true
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read_in_progress = true
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break
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}
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src2 = src
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}
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mut got_im_sem := false
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for sp := u32(0); sp < spinloops_sem_ || read_in_progress; sp++ {
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got_im_sem = ch.writesem_im.try_wait()
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if got_im_sem {
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break
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}
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}
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for {
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if got_im_sem {
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got_im_sem = false
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} else {
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ch.writesem_im.wait()
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}
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if C.atomic_load_u16(&ch.closed) != 0 {
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if have_swapped
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|| C.atomic_compare_exchange_strong_ptr(unsafe { &voidptr(&ch.adr_read) }, &src2, voidptr(0)) {
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ch.writesem.post()
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return .success
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} else {
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return .closed
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}
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}
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if have_swapped
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|| C.atomic_compare_exchange_strong_ptr(unsafe { &voidptr(&ch.adr_read) }, &src2, voidptr(0)) {
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ch.writesem.post()
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break
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} else {
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// this semaphore was not for us - repost in
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ch.writesem_im.post()
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if src2 == voidptr(-1) {
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ch.readsem.post()
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return .closed
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}
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src2 = src
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}
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}
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return .success
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} else {
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// buffered channel
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mut space_in_queue := false
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mut wr_free := C.atomic_load_u32(&ch.write_free)
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for wr_free > 0 {
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space_in_queue = C.atomic_compare_exchange_weak_u32(&ch.write_free, &wr_free,
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wr_free - 1)
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if space_in_queue {
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break
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}
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}
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if space_in_queue {
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mut wr_idx := C.atomic_load_u32(&ch.buf_elem_write_idx)
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for {
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mut new_wr_idx := wr_idx + 1
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for new_wr_idx >= ch.cap {
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new_wr_idx -= ch.cap
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}
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if C.atomic_compare_exchange_strong_u32(&ch.buf_elem_write_idx, &wr_idx,
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new_wr_idx)
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{
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break
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}
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}
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mut wr_ptr := ch.ringbuf
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mut status_adr := ch.statusbuf
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unsafe {
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wr_ptr += wr_idx * ch.objsize
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status_adr += wr_idx * sizeof(u16)
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}
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mut expected_status := u16(BufferElemStat.unused)
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for !C.atomic_compare_exchange_weak_u16(unsafe { &u16(status_adr) },
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&expected_status, u16(BufferElemStat.writing)) {
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expected_status = u16(BufferElemStat.unused)
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}
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unsafe {
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C.memcpy(wr_ptr, src, ch.objsize)
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}
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C.atomic_store_u16(unsafe { &u16(status_adr) }, u16(BufferElemStat.written))
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C.atomic_fetch_add_u32(&ch.read_avail, 1)
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ch.readsem.post()
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mut null16 := u16(0)
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for !C.atomic_compare_exchange_weak_u16(&ch.read_sub_mtx, &null16, u16(1)) {
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null16 = u16(0)
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}
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if ch.read_subscriber != voidptr(0) {
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ch.read_subscriber.sem.post()
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}
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C.atomic_store_u16(&ch.read_sub_mtx, u16(0))
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return .success
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} else {
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if no_block {
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return .not_ready
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}
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ch.writesem.post()
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}
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}
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}
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// we should not get here but the V compiler want's to see a return statement
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assert false
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return .success
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}
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[inline]
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pub fn (mut ch Channel) pop(dest voidptr) bool {
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return ch.try_pop_priv(dest, false) == .success
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}
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[inline]
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pub fn (mut ch Channel) try_pop(dest voidptr) ChanState {
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return ch.try_pop_priv(dest, true)
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}
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fn (mut ch Channel) try_pop_priv(dest voidptr, no_block bool) ChanState {
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spinloops_sem_, spinloops_ := if no_block { 1, 1 } else { sync.spinloops, sync.spinloops_sem }
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mut have_swapped := false
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mut write_in_progress := false
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for {
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mut got_sem := false
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if ch.cap == 0 {
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// unbuffered channel - first see if a `push()` has adversized
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mut rdadr := C.atomic_load_ptr(unsafe { &voidptr(&ch.read_adr) })
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for rdadr != C.NULL {
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if C.atomic_compare_exchange_strong_ptr(unsafe { &voidptr(&ch.read_adr) },
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&rdadr, voidptr(0))
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{
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// there is a writer waiting for us
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unsafe { C.memcpy(dest, rdadr, ch.objsize) }
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mut nulladr := voidptr(0)
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for !C.atomic_compare_exchange_weak_ptr(unsafe { &voidptr(&ch.adr_read) },
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&nulladr, rdadr) {
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nulladr = voidptr(0)
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}
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ch.writesem_im.post()
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return .success
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}
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}
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if no_block {
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if C.atomic_load_u16(&ch.closed) == 0 {
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return .not_ready
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} else {
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return .closed
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}
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}
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}
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// get token to read
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for _ in 0 .. spinloops_sem_ {
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if got_sem {
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break
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}
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got_sem = ch.readsem.try_wait()
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}
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if !got_sem {
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if no_block {
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if C.atomic_load_u16(&ch.closed) == 0 {
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return .not_ready
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} else {
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return .closed
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}
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}
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ch.readsem.wait()
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}
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if ch.cap > 0 {
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// try to get buffer token
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mut obj_in_queue := false
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mut rd_avail := C.atomic_load_u32(&ch.read_avail)
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for rd_avail > 0 {
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obj_in_queue = C.atomic_compare_exchange_weak_u32(&ch.read_avail, &rd_avail,
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rd_avail - 1)
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if obj_in_queue {
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break
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}
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}
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if obj_in_queue {
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mut rd_idx := C.atomic_load_u32(&ch.buf_elem_read_idx)
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for {
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mut new_rd_idx := rd_idx + 1
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for new_rd_idx >= ch.cap {
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new_rd_idx -= ch.cap
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}
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if C.atomic_compare_exchange_weak_u32(&ch.buf_elem_read_idx, &rd_idx,
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new_rd_idx)
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{
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break
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}
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}
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mut rd_ptr := ch.ringbuf
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mut status_adr := ch.statusbuf
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unsafe {
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rd_ptr += rd_idx * ch.objsize
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status_adr += rd_idx * sizeof(u16)
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}
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mut expected_status := u16(BufferElemStat.written)
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for !C.atomic_compare_exchange_weak_u16(unsafe { &u16(status_adr) },
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&expected_status, u16(BufferElemStat.reading)) {
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expected_status = u16(BufferElemStat.written)
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}
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unsafe {
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C.memcpy(dest, rd_ptr, ch.objsize)
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}
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C.atomic_store_u16(unsafe { &u16(status_adr) }, u16(BufferElemStat.unused))
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C.atomic_fetch_add_u32(&ch.write_free, 1)
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ch.writesem.post()
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mut null16 := u16(0)
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for !C.atomic_compare_exchange_weak_u16(&ch.write_sub_mtx, &null16, u16(1)) {
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null16 = u16(0)
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}
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if ch.write_subscriber != voidptr(0) {
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ch.write_subscriber.sem.post()
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}
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C.atomic_store_u16(&ch.write_sub_mtx, u16(0))
|
|
return .success
|
|
}
|
|
}
|
|
// try to advertise `dest` as writable
|
|
C.atomic_store_ptr(unsafe { &voidptr(&ch.write_adr) }, dest)
|
|
if ch.cap == 0 {
|
|
mut rdadr := C.atomic_load_ptr(unsafe { &voidptr(&ch.read_adr) })
|
|
if rdadr != C.NULL {
|
|
mut dest2 := dest
|
|
if C.atomic_compare_exchange_strong_ptr(unsafe { &voidptr(&ch.write_adr) },
|
|
&dest2, voidptr(0))
|
|
{
|
|
ch.readsem.post()
|
|
continue
|
|
} else {
|
|
write_in_progress = true
|
|
}
|
|
}
|
|
}
|
|
if ch.cap == 0 && !write_in_progress {
|
|
mut null16 := u16(0)
|
|
for !C.atomic_compare_exchange_weak_u16(&ch.write_sub_mtx, &null16, u16(1)) {
|
|
null16 = u16(0)
|
|
}
|
|
if ch.write_subscriber != voidptr(0) {
|
|
ch.write_subscriber.sem.post()
|
|
}
|
|
C.atomic_store_u16(&ch.write_sub_mtx, u16(0))
|
|
}
|
|
mut dest2 := dest
|
|
for sp := u32(0); sp < spinloops_ || write_in_progress; sp++ {
|
|
if C.atomic_compare_exchange_strong_ptr(unsafe { &voidptr(&ch.adr_written) },
|
|
&dest2, voidptr(0))
|
|
{
|
|
have_swapped = true
|
|
break
|
|
} else if dest2 == voidptr(-1) {
|
|
ch.readsem.post()
|
|
return .closed
|
|
}
|
|
dest2 = dest
|
|
}
|
|
mut got_im_sem := false
|
|
for sp := u32(0); sp < spinloops_sem_ || write_in_progress; sp++ {
|
|
got_im_sem = ch.readsem_im.try_wait()
|
|
if got_im_sem {
|
|
break
|
|
}
|
|
}
|
|
for {
|
|
if got_im_sem {
|
|
got_im_sem = false
|
|
} else {
|
|
ch.readsem_im.wait()
|
|
}
|
|
if have_swapped
|
|
|| C.atomic_compare_exchange_strong_ptr(unsafe { &voidptr(&ch.adr_written) }, &dest2, voidptr(0)) {
|
|
ch.readsem.post()
|
|
break
|
|
} else {
|
|
// this semaphore was not for us - repost in
|
|
ch.readsem_im.post()
|
|
if dest2 == voidptr(-1) {
|
|
ch.readsem.post()
|
|
return .closed
|
|
}
|
|
dest2 = dest
|
|
}
|
|
}
|
|
break
|
|
}
|
|
return .success
|
|
}
|
|
|
|
// Wait `timeout` on any of `channels[i]` until one of them can push (`is_push[i] = true`) or pop (`is_push[i] = false`)
|
|
// object referenced by `objrefs[i]`. `timeout < 0` means wait unlimited time. `timeout == 0` means return immediately
|
|
// if no transaction can be performed without waiting.
|
|
// return value: the index of the channel on which a transaction has taken place
|
|
// -1 if waiting for a transaction has exceeded timeout
|
|
// -2 if all channels are closed
|
|
|
|
pub fn channel_select(mut channels []&Channel, dir []Direction, mut objrefs []voidptr, timeout time.Duration) int {
|
|
assert channels.len == dir.len
|
|
assert dir.len == objrefs.len
|
|
mut subscr := []Subscription{len: channels.len}
|
|
mut sem := unsafe { Semaphore{} }
|
|
sem.init(0)
|
|
for i, ch in channels {
|
|
subscr[i].sem = &sem
|
|
if dir[i] == .push {
|
|
mut null16 := u16(0)
|
|
for !C.atomic_compare_exchange_weak_u16(&ch.write_sub_mtx, &null16, u16(1)) {
|
|
null16 = u16(0)
|
|
}
|
|
subscr[i].prev = &ch.write_subscriber
|
|
unsafe {
|
|
subscr[i].nxt = &Subscription(C.atomic_exchange_ptr(&voidptr(&ch.write_subscriber),
|
|
&subscr[i]))
|
|
}
|
|
if voidptr(subscr[i].nxt) != voidptr(0) {
|
|
subscr[i].nxt.prev = &subscr[i].nxt
|
|
}
|
|
C.atomic_store_u16(&ch.write_sub_mtx, u16(0))
|
|
} else {
|
|
mut null16 := u16(0)
|
|
for !C.atomic_compare_exchange_weak_u16(&ch.read_sub_mtx, &null16, u16(1)) {
|
|
null16 = u16(0)
|
|
}
|
|
subscr[i].prev = &ch.read_subscriber
|
|
unsafe {
|
|
subscr[i].nxt = &Subscription(C.atomic_exchange_ptr(&voidptr(&ch.read_subscriber),
|
|
&subscr[i]))
|
|
}
|
|
if voidptr(subscr[i].nxt) != voidptr(0) {
|
|
subscr[i].nxt.prev = &subscr[i].nxt
|
|
}
|
|
C.atomic_store_u16(&ch.read_sub_mtx, u16(0))
|
|
}
|
|
}
|
|
stopwatch := if timeout <= 0 { time.StopWatch{} } else { time.new_stopwatch({}) }
|
|
mut event_idx := -1 // negative index means `timed out`
|
|
|
|
outer: for {
|
|
rnd := rand.u32_in_range(0, u32(channels.len))
|
|
mut num_closed := 0
|
|
for j, _ in channels {
|
|
mut i := j + int(rnd)
|
|
if i >= channels.len {
|
|
i -= channels.len
|
|
}
|
|
if dir[i] == .push {
|
|
stat := channels[i].try_push_priv(objrefs[i], true)
|
|
if stat == .success {
|
|
event_idx = i
|
|
break outer
|
|
} else if stat == .closed {
|
|
num_closed++
|
|
}
|
|
} else {
|
|
stat := channels[i].try_pop_priv(objrefs[i], true)
|
|
if stat == .success {
|
|
event_idx = i
|
|
break outer
|
|
} else if stat == .closed {
|
|
num_closed++
|
|
}
|
|
}
|
|
}
|
|
if num_closed == channels.len {
|
|
event_idx = -2
|
|
break outer
|
|
}
|
|
if timeout == 0 {
|
|
break outer
|
|
}
|
|
if timeout > 0 {
|
|
remaining := timeout - stopwatch.elapsed()
|
|
if !sem.timed_wait(remaining) {
|
|
break outer
|
|
}
|
|
} else {
|
|
sem.wait()
|
|
}
|
|
}
|
|
// reset subscribers
|
|
for i, ch in channels {
|
|
if dir[i] == .push {
|
|
mut null16 := u16(0)
|
|
for !C.atomic_compare_exchange_weak_u16(&ch.write_sub_mtx, &null16, u16(1)) {
|
|
null16 = u16(0)
|
|
}
|
|
unsafe {
|
|
*subscr[i].prev = subscr[i].nxt
|
|
}
|
|
if subscr[i].nxt != 0 {
|
|
subscr[i].nxt.prev = subscr[i].prev
|
|
// just in case we have missed a semaphore during restore
|
|
subscr[i].nxt.sem.post()
|
|
}
|
|
C.atomic_store_u16(&ch.write_sub_mtx, u16(0))
|
|
} else {
|
|
mut null16 := u16(0)
|
|
for !C.atomic_compare_exchange_weak_u16(&ch.read_sub_mtx, &null16, u16(1)) {
|
|
null16 = u16(0)
|
|
}
|
|
unsafe {
|
|
*subscr[i].prev = subscr[i].nxt
|
|
}
|
|
if subscr[i].nxt != 0 {
|
|
subscr[i].nxt.prev = subscr[i].prev
|
|
subscr[i].nxt.sem.post()
|
|
}
|
|
C.atomic_store_u16(&ch.read_sub_mtx, u16(0))
|
|
}
|
|
}
|
|
sem.destroy()
|
|
return event_idx
|
|
}
|