v1.9.6

FIXED:
* More clear docs for bitmask
* Resolved potential issue for using PriorityAll in
  logging.logPrio.HasFlag.

bitmask/bitmask.go

@@ -36,7 +36,9 @@ func NewMaskBitExplicit(value uint) (m *MaskBit) {
 
 /*
 	HasFlag is true if m has MaskBit flag set/enabled.
+
 	THIS WILL RETURN FALSE FOR OR'd FLAGS.
+
 	For example:
 
 		flagA MaskBit = 0x01
@@ -44,12 +46,15 @@ func NewMaskBitExplicit(value uint) (m *MaskBit) {
 		flagComposite = flagA | flagB
 
 		m *MaskBit = NewMaskBitExplicit(uint(flagA))
-	
+
 	m.HasFlag(flagComposite) will return false even though flagComposite is an OR
 	that contains flagA.
 	Use [MaskBit.IsOneOf] instead if you do not desire this behavior,
 	and instead want to test composite flag *membership*.
 	(MaskBit.IsOneOf will also return true for non-composite equality.)
+
+	To be more clear, if MaskBit flag is a composite MaskBit (e.g. flagComposite above),
+	HasFlag will only return true of ALL bits in flag are also set in MaskBit m.
 */
 func (m *MaskBit) HasFlag(flag MaskBit) (r bool) {
 
@@ -70,12 +75,15 @@ func (m *MaskBit) HasFlag(flag MaskBit) (r bool) {
 	If composite is *not* an OR'd MaskBit (i.e.
 	it falls directly on a boundary -- 0, 1, 2, 4, 8, 16, etc.),
 	then IsOneOf will behave exactly like HasFlag.
+
+	If m is a composite MaskBit (it usually is) and composite is ALSO a composite MaskBit,
+	IsOneOf will return true if ANY of the flags set in m is set in composite.
 */
 func (m *MaskBit) IsOneOf(composite MaskBit) (r bool) {
 
 	var b MaskBit = *m
 
-	if b&flag != 0 {
+	if b&composite != 0 {
 		r = true
 	}
 	return

bitmask/doc.go

@@ -1,9 +1,35 @@
 /*
 Package bitmask handles a flag-like opt/bitmask system.
 
-See https://yourbasic.org/golang/bitmask-flag-set-clear/ for more information.
+See https://yourbasic.org/golang/bitmask-flag-set-clear/ for basic information on what bitmasks are and why they're useful.
 
-To use this, set constants like thus:
+Specifically, in the case of Go, they allow you to essentially manage many, many, many "booleans" as part of a single value.
+
+A single bool value in Go takes up 8 bits/1 byte, unavoidably.
+
+However, a [bitmask.MaskBit] is backed by a uint which (depending on your platform) is either 32 bits/4 bytes or 64 bits/8 bytes.
+
+"But wait, that takes up more memory though!"
+
+Yep, but bitmasking lets you store a "boolean" AT EACH BIT - it operates on
+whether a bit in a byte/set of bytes at a given position is 0 or 1.
+
+Which means on 32-bit platforms, a [MaskBit] can have up to 4294967295 "booleans" in a single value (0 to (2^32)-1).
+
+On 64-bit platforms, a [MaskBit] can have up to 18446744073709551615 "booleans" in a single value (0 to (2^64)-1).
+
+If you tried to do that with Go bool values, that'd take up 4294967295 bytes (4 GiB)
+or 18446744073709551615 bytes (16 EiB - yes, that's [exbibytes]) of RAM for 32-bit/64-bit platforms respectively.
+
+"But that has to be so slow to unpack that!"
+
+Nope. It's not using compression or anything, the CPU is just comparing bit "A" vs. bit "B" 32/64 times. That's super easy work for a CPU.
+
+There's a reason Doom used bitmasking for the "dmflags" value in its server configs.
+
+# Usage
+
+To use this library, set constants like thus:
 
 	package main
 
@@ -42,12 +68,95 @@ But this would return false:
 
 	MyMask.HasFlag(OPT2)
 
+# Technical Caveats
+
+TARGETING
+
+When implementing, you should always set MyMask (from Usage section above) as the actual value.
+For example, if you are checking a permissions set for a user that has the value, say, 6
+
+	var userPerms uint = 6 // 0x0000000000000006
+
+and your library has the following permission bits defined:
+
+	const PermsNone bitmask.MaskBit = 0
+	const (
+		PermsList bitmask.MaskBit = 1 << iota // 1
+		PermsRead                             // 2
+		PermsWrite                            // 4
+		PermsExec                             // 8
+		PermsAdmin                            // 16
+	)
+
+And you want to see if the user has the PermsRead flag set, you would do:
+
+	userPermMask = bitmask.NewMaskBitExplicit(userPerms)
+	if userPermMask.HasFlag(PermsRead) {
+		// ...
+	}
+
+NOT:
+
+	userPermMask = bitmask.NewMaskBitExplicit(PermsRead)
+	// Nor:
+	// userPermMask = PermsRead
+	if userPermMask.HasFlag(userPerms) {
+		// ...
+	}
+
+This will be terribly, horribly wrong, cause incredibly unexpected results,
+and quite possibly cause massive security issues. Don't do it.
+
+COMPOSITES
+
+If you want to define a set of flags that are a combination of other flags,
+your inclination would be to bitwise-OR them together:
+
+	const (
+		flagA bitmask.MaskBit = 1 << iota // 1
+		flagB                             // 2
+	)
+
+	const (
+		flagAB bitmask.MaskBit = flagA | flagB // 3
+	)
+
+Which is fine and dandy. But if you then have:
+
+	var myMask *bitmask.MaskBit = bitmask.NewMaskBit()
+
+	myMask.AddFlag(flagA)
+
+You may expect this call to [MaskBit.HasFlag]:
+
+	myMask.HasFlag(flagAB)
+
+to be true, since flagA is "in" flagAB.
+It will return false - HasFlag does strict comparisons.
+It will only return true if you then ALSO do:
+
+	// This would require setting flagA first.
+	// The order of setting flagA/flagB doesn't matter,
+	// but you must have both set for HasFlag(flagAB) to return true.
+	myMask.AddFlag(flagB)
+
+or if you do:
+
+	// This can be done with or without additionally setting flagA.
+	myMask.AddFlag(flagAB)
+
+Instead, if you want to see if a mask has membership within a composite flag,
+you can use [MaskBit.IsOneOf].
+
+# Other Options
+
 If you need something with more flexibility (as always, at the cost of complexity),
 you may be interested in one of the following libraries:
 
-. github.com/alvaroloes/enumer
-. github.com/abice/go-enum
-. github.com/jeffreyrichter/enum/enum
+	* [github.com/alvaroloes/enumer]
+	* [github.com/abice/go-enum]
+	* [github.com/jeffreyrichter/enum/enum]
 
+[exbibytes]: https://simple.wikipedia.org/wiki/Exbibyte
 */
 package bitmask

logging/TODO

@@ -4,6 +4,8 @@
 -- no native Go support (yet)?
 --- https://developer.apple.com/forums/thread/773369
 
+- The log destinations for e.g. consts_nix.go et. al. probably should be unexported types.
+
 - add a `log/slog` logging.Logger?
 
 - Implement code line/func/etc. (only for debug?):

logging/consts_nix.go

@@ -23,8 +23,8 @@ const (
 // LogUndefined indicates an undefined Logger type.
 const LogUndefined bitmask.MaskBit = iota
 const (
-	// LogJournald flags a SystemDLogger Logger type.
-	LogJournald = 1 << iota
+	// LogJournald flags a SystemDLogger Logger type. This will, for hopefully obvious reasons, only work on Linux systemd systems.
+	LogJournald bitmask.MaskBit = 1 << iota
 	// LogSyslog flags a SyslogLogger Logger type.
 	LogSyslog
 	// LogFile flags a FileLogger Logger type.

logging/consts_windows.go

@@ -3,16 +3,14 @@ package logging
 import (
 	`os`
 	`path/filepath`
-
-	`r00t2.io/goutils/bitmask`
 )
 
 // Flags for logger configuration. These are used internally.
+// LogUndefined indicates an undefined Logger type.
+LogUndefined bitmask.MaskBit = 0
 const (
-	// LogUndefined indicates an undefined Logger type.
-	LogUndefined bitmask.MaskBit = 1 << iota
 	// LogWinLogger indicates a WinLogger Logger type (Event Log).
-	LogWinLogger
+	LogWinLogger bitmask.MaskBit= 1 << iota
 	// LogFile flags a FileLogger Logger type.
 	LogFile
 	// LogStdout flags a StdLogger Logger type.

logging/funcs_logprio.go

@@ -17,7 +17,9 @@ func (l *logPrio) HasFlag(prio logPrio) (hasFlag bool) {
 	m = bitmask.NewMaskBitExplicit(uint(*l))
 	p = bitmask.NewMaskBitExplicit(uint(prio))
 
-	hasFlag = m.HasFlag(*p)
+	// Use IsOneOf instead in case PriorityAll is passed for prio.
+	// hasFlag = m.HasFlag(*p)
+	hasFlag = m.IsOneOf(*p)
 
 	return
 }

logging/funcs_logwriter.go

@@ -40,6 +40,8 @@ func (l *logWriter) Write(b []byte) (n int, err error) {
 
 	s = string(b)
 
+	// Since this explicitly checks each priority level, there's no need for IsOneOf in case of PriorityAll.
+
 	if l.prio.HasFlag(PriorityEmergency) {
 		if err = l.backend.Emerg(s); err != nil {
 			mErr.AddError(err)