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@@ -0,0 +1,136 @@
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+{$IFNDEF FPC_DOTTEDUNITS}
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+unit WasmSem;
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+{$ENDIF}
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+
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+{$mode objfpc}{$H+}
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+{$codepage utf8}
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+
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+interface
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+
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+uses
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+{$IFDEF FPC_DOTTEDUNITS}
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+ Wasm.Api;
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+{$ELSE}
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+ WebAssembly;
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+{$ENDIF}
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+
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+type
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+ PWasmSemaphore = ^TWasmSemaphore;
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+ TWasmSemaphore = packed record
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+ counter: longint; // Current counter value
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+ max_count: longint; // Maximum count allowed
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+ end;
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+
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+// Initialize a semaphore with initial count and maximum count
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+procedure semaphore_init(var sem: TWasmSemaphore; initial_count, max_count: longint);
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+
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+// Wait (acquire) operation with timeout - decrements counter, blocks if counter would go negative
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+// timeout_ms: timeout in milliseconds (-1 for infinite timeout)
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+// Returns true if acquired successfully, false if timeout occurred
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+function semaphore_wait(var sem: TWasmSemaphore; timeout_ms: int64): boolean;
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+
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+// Wait (acquire) operation without timeout - blocks indefinitely until semaphore is available
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+// Returns true when acquired successfully
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+function semaphore_wait_infinite(var sem: TWasmSemaphore): boolean;
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+
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+// Signal (release) operation - increments counter up to max and notifies waiters
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+// Returns true if signaled successfully, false if at max count
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+function semaphore_signal(var sem: TWasmSemaphore): boolean;
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+
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+// Get current semaphore count (read-only)
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+function semaphore_count(var sem: TWasmSemaphore): longint;
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+
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+// Get maximum semaphore count (read-only)
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+function semaphore_max_count(var sem: TWasmSemaphore): longint;
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+
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+implementation
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+
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+procedure semaphore_init(var sem: TWasmSemaphore; initial_count, max_count: longint);
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+begin
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+ AtomicStore(sem.counter, initial_count);
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+ AtomicStore(sem.max_count, max_count);
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+end;
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+
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+function semaphore_wait(var sem: TWasmSemaphore; timeout_ms: int64): boolean;
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+var
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+ current_count: longint;
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+ new_count: longint;
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+ expected: longint;
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+ wait_result: longint;
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+ timeout_ns: int64;
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+begin
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+ if timeout_ms = -1 then
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+ timeout_ns := awtInfiniteTimeout
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+ else
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+ timeout_ns := timeout_ms * 1000000;
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+
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+ repeat
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+ current_count := AtomicLoad(sem.counter);
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+
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+ if current_count > 0 then
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+ begin
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+ new_count := current_count - 1;
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+ expected := current_count;
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+
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+ if AtomicCompareExchange(sem.counter, expected, new_count) = expected then
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+ exit(true);
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+ // Failed CAS, retry immediately
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+ end
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+ else
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+ begin
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+ wait_result := AtomicWait(sem.counter, current_count, timeout_ns);
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+ if wait_result = awrTimedOut then
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+ exit(false);
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+ // Either woke up (awrOk) or not-equal (awrNotEqual), retry the acquisition
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+ end;
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+ until false;
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+ // Should never reach here
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+ result := false;
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+end;
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+
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+function semaphore_wait_infinite(var sem: TWasmSemaphore): boolean;
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+begin
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+ result := semaphore_wait(sem, -1);
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+end;
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+
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+function semaphore_signal(var sem: TWasmSemaphore): boolean;
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+var
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+ current_count: longint;
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+ max_count: longint;
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+ new_count: longint;
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+ expected: longint;
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+ woken_count: longword;
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+begin
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+ max_count := AtomicLoad(sem.max_count);
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+
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+ repeat
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+ current_count := AtomicLoad(sem.counter);
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+ if current_count >= max_count then
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+ exit(false);
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+
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+ new_count := current_count + 1;
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+ expected := current_count;
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+
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+ // Try atomic compare-and-swap
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+ if AtomicCompareExchange(sem.counter, expected, new_count) = expected then
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+ begin
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+ woken_count := AtomicNotify(sem.counter, 1);
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+ exit(true);
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+ end;
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+ // Failed CAS, retry
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+ until false;
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+ // Should never reach here
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+ result := false;
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+end;
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+
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+function semaphore_count(var sem: TWasmSemaphore): longint;
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+begin
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+ result := AtomicLoad(sem.counter);
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+end;
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+
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+function semaphore_max_count(var sem: TWasmSemaphore): longint;
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+begin
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+ result := AtomicLoad(sem.max_count);
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+end;
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+
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+end.
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Michaël Van Canneyt