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path: root/logger/sys.go
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package logger

import (
    "sync"
)

var (
    logMessageC = make(chan message)
    addSystemC  = make(chan LogSystem)
    flushC      = make(chan chan struct{})
    resetC      = make(chan chan struct{})
)

func init() {
    go dispatchLoop()
}

// each system can buffer this many messages before
// blocking incoming log messages.
const sysBufferSize = 500

func dispatchLoop() {
    var (
        systems  []LogSystem
        systemIn []chan message
        systemWG sync.WaitGroup
    )
    bootSystem := func(sys LogSystem) {
        in := make(chan message, sysBufferSize)
        systemIn = append(systemIn, in)
        systemWG.Add(1)
        go sysLoop(sys, in, &systemWG)
    }

    for {
        select {
        case msg := <-logMessageC:
            for _, c := range systemIn {
                c <- msg
            }

        case sys := <-addSystemC:
            systems = append(systems, sys)
            bootSystem(sys)

        case waiter := <-resetC:
            // reset means terminate all systems
            for _, c := range systemIn {
                close(c)
            }
            systems = nil
            systemIn = nil
            systemWG.Wait()
            close(waiter)

        case waiter := <-flushC:
            // flush means reboot all systems
            for _, c := range systemIn {
                close(c)
            }
            systemIn = nil
            systemWG.Wait()
            for _, sys := range systems {
                bootSystem(sys)
            }
            close(waiter)
        }
    }
}

func sysLoop(sys LogSystem, in <-chan message, wg *sync.WaitGroup) {
    for msg := range in {
        if sys.GetLogLevel() >= msg.level {
            sys.LogPrint(msg.level, msg.msg)
        }
    }
    wg.Done()
}

// Reset removes all active log systems.
// It blocks until all current messages have been delivered.
func Reset() {
    waiter := make(chan struct{})
    resetC <- waiter
    <-waiter
}

// Flush waits until all current log messages have been dispatched to
// the active log systems.
func Flush() {
    waiter := make(chan struct{})
    flushC <- waiter
    <-waiter
}

// AddLogSystem starts printing messages to the given LogSystem.
func AddLogSystem(sys LogSystem) {
    addSystemC <- sys
}