GO语言处理多个布尔选项的实现过程

// 文件操作配置类
type Config struct {
    IsReadOnly   bool
    IsWriteOnly  bool
    IsCreate     bool
    // ... 每个标志都需要一个字段
}

// 文件操作类型常量，按 2 的幂次赋值，每个类型占用一个二进制中的位
const (
    O_RDONLY = 1 << iota // 1 (0b0001)
    O_WRONLY             // 2 (0b0010)
    O_CREAT              // 4 (0b0100)
)

// 文件操作配置类
type Config struct {
    Flags int // 文件操作类型标识位
}

// 设置多个标志
config.Flags = O_CREAT | O_WRONLY

// 清除标识
config.Flags &^= O_CREAT  // 清除 O_CREAT 标志

func Process(flags int) {
    // 检查多个标志
    if flags & (O_CREAT | O_WRONLY) != 0 {
        // 处理逻辑...
    }

    // ...    
}

// 同时设置多个标志
config.Flags = O_CREAT | O_WRONLY

// 源码位置：src/os/file.go

// Flags to OpenFile wrapping those of the underlying system. Not all
// flags may be implemented on a given system.
const (
	// Exactly one of O_RDONLY, O_WRONLY, or O_RDWR must be specified.
	O_RDONLY int = syscall.O_RDONLY // open the file read-only.
	O_WRONLY int = syscall.O_WRONLY // open the file write-only.
	O_RDWR   int = syscall.O_RDWR   // open the file read-write.
	// The remaining values may be or'ed in to control behavior.
	O_APPEND int = syscall.O_APPEND // append data to the file when writing.
	O_CREATE int = syscall.O_CREAT  // create a new file if none exists.
	O_EXCL   int = syscall.O_EXCL   // used with O_CREATE, file must not exist.
	O_SYNC   int = syscall.O_SYNC   // open for synchronous I/O.
	O_TRUNC  int = syscall.O_TRUNC  // truncate regular writable file when opened.
)

const (
	// Invented values to support what package os expects.
	O_RDONLY       = 0x00000
	O_WRONLY       = 0x00001
	O_RDWR         = 0x00002
	O_CREAT        = 0x00040
	O_EXCL         = 0x00080
	O_NOCTTY       = 0x00100
	O_TRUNC        = 0x00200
	O_NONBLOCK     = 0x00800
	O_APPEND       = 0x00400
	O_SYNC         = 0x01000
	O_ASYNC        = 0x02000
	O_CLOEXEC      = 0x80000
	o_DIRECTORY    = 0x100000   // used by internal/syscall/windows
	o_NOFOLLOW_ANY = 0x20000000 // used by internal/syscall/windows
	o_OPEN_REPARSE = 0x40000000 // used by internal/syscall/windows
)

// 源码位置：src/syscall/syscall_windows.go
func Open(name string, flag int, perm uint32) (fd Handle, err error) {
	if len(name) == 0 {
		return InvalidHandle, ERROR_FILE_NOT_FOUND
	}
	namep, err := UTF16PtrFromString(name)
	if err != nil {
		return InvalidHandle, err
	}
	var access uint32
	switch flag & (O_RDONLY | O_WRONLY | O_RDWR) {
	case O_RDONLY:
		access = GENERIC_READ
	case O_WRONLY:
		access = GENERIC_WRITE
	case O_RDWR:
		access = GENERIC_READ | GENERIC_WRITE
	}
	if flag&O_CREAT != 0 {
		access |= GENERIC_WRITE
	}

    // ...

	return h, nil
}

// 源码位置：pkg/mod/github.com/gogf/gf@v1.16.9/os/glog/glog_logger.go

// 设置日志打印选项常量值
const (
	F_ASYNC      = 1 << iota // Print logging content asynchronously。
	F_FILE_LONG              // Print full file name and line number: /a/b/c/d.go:23.
	F_FILE_SHORT             // Print final file name element and line number: d.go:23. overrides F_FILE_LONG.
	F_TIME_DATE              // Print the date in the local time zone: 2009-01-23.
	F_TIME_TIME              // Print the time in the local time zone: 01:23:23.
	F_TIME_MILLI             // Print the time with milliseconds in the local time zone: 01:23:23.675.
	F_CALLER_FN              // Print Caller function name and package: main.main
	F_TIME_STD   = F_TIME_DATE | F_TIME_MILLI
)


// 源码位置：pkg/mod/github.com/gogf/gf@v1.16.9/os/glog/glog_logger_config.go
// Config is the configuration object for logger.
type Config struct {
	Handlers             []Handler      `json:"-"`                    // Logger handlers which implement feature similar as middleware.
	Writer               io.Writer      `json:"-"`                    // Customized io.Writer.
    // 日志打印选项标识位
	Flags                int            `json:"flags"`                // Extra flags for logging output features.
    // ...
}

func DefaultConfig() Config {
	c := Config{
		File:                defaultFileFormat,
		Flags:               F_TIME_STD,  // 打印内容默认设置为 标准时间格式
		Level:               LEVEL_ALL,
		CtxKeys:             []interface{}{gctx.CtxKey},
		// ...
	}
	
    // ...

	return c
}

// SetAsync enables/disables async logging output feature.
func (l *Logger) SetAsync(enabled bool) {
	if enabled {
		l.config.Flags = l.config.Flags | F_ASYNC   // 设置 F_ASYNC 标识位
	} else {
		l.config.Flags = l.config.Flags & ^F_ASYNC  // 清除 F_ASYNC 标识位
	}
}

// 源码位置：pkg/mod/github.com/gogf/gf@v1.16.9/os/glog/glog_logger.go
// print prints `s` to defined writer, logging file or passed `std`.
func (l *Logger) print(ctx context.Context, level int, values ...interface{}) {
	// ...
	if l.config.HeaderPrint {
		// Time.
		timeFormat := ""
		if l.config.Flags&F_TIME_DATE > 0 {  // 判断日志打印选项标识位中是否含有 F_TIME_DATE
			timeFormat += "2006-01-02"
		}
		if l.config.Flags&F_TIME_TIME > 0 {
			if timeFormat != "" {
				timeFormat += " "
			}
			timeFormat += "15:04:05"
		}
		if l.config.Flags&F_TIME_MILLI > 0 {
			if timeFormat != "" {
				timeFormat += " "
			}
			timeFormat += "15:04:05.000"
		}

		// ...
	}

	// ...
}

// 位于 src/sync/mutex.go
 
type Mutex struct {
	state int32     // 锁状态和一些标志位
	sema  uint32    // 信号量，用于阻塞和唤醒等待的 goroutine
}
 
const (
	mutexLocked = 1 << iota // 是否被锁定  
	mutexWoken              // 是否有协程被唤醒
	mutexStarving           // 是否处于饥饿模式
	mutexWaiterShift = iota // 表示等待锁的阻塞协程个数
	starvationThresholdNs = 1e6
)