Semaphores

Semaphores are mainly used for communication between processes or with external systems.

The system has 256 built-in semaphores, indexed from 0 to 255. Each semaphore can store a 32-bit integer value, ranging from -2147483648 to 2147483647.

All semaphores are reset to 0 after system restart.

Set Semaphore auto_sync

• Function: set_signal from the lua module
• Parameters:
  1. index: [int] Semaphore index
  2. value: [int] Semaphore value to set
• Returns: [bool] Whether set successfully

Example

set_signal(1, 100)

Increment Semaphore auto_sync

• Function: add_signal from the lua module
• Parameters:
  1. index: [int] Semaphore index
  2. value: [int] Value to increment
• Returns: [int] Semaphore value after increment. May overflow

Example

add_signal(1, 2)
print(get_signal(1))

Set Multiple Semaphores auto_sync

• Function: set_signals from the lua module
• Parameters:
  1. index: [int] Semaphore starting index
  2. values: [list[int]] Semaphore values to set
• Returns: [bool] Whether set successfully

Example

set_signals(1, {1, 2, 3})

Get Semaphore

• Function: get_signal from the lua module
• Parameters:
  1. index: [int] Semaphore index
• Returns: [int] Corresponding semaphore value

Example

print(get_signal(1))

Get Multiple Semaphores

• Function: get_signals from the lua module
• Parameters:
  1. index: [int] Semaphore starting index
  2. len: [int] Number of semaphores to get
• Returns: [list[int]] Semaphore value array

Example

values = get_signals(1, 3)
print(values)

Wait Semaphore auto_sync

Blocks and waits until semaphore meets specified condition.

• Function: wait_signal from the lua module
• Parameters:
  1. index: [int] Semaphore index
  2. value: [int] Value to compare
  3. relation: [str] Relational Operator
• Returns: [bool] Whether condition is met

Example

wait_signal(1, 100, ">=")

Example

set_signal(1, 2147483647)
print(get_signal(1))
add_signal(1, 2)
print(get_signal(1))

Compatibility Note

signal_set, signal_get, signal_wait, signal_add are aliases for set_signal, get_signal, wait_signal, add_signal respectively.