2 Commits

Author SHA1 Message Date
brent saner
688abd0874 v1.9.5
FIXED:
* HasFlag would inappropriately report true for m = A, flag = A | B.
  This has been rectified, and this behavior is now explicitly
  exposed via IsOneOf.
2025-08-26 20:39:29 -04:00
brent saner
a1f87d6b51 stubbing encoding/bit 2025-08-23 19:32:48 -04:00
4 changed files with 104 additions and 1 deletions

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@@ -0,0 +1,19 @@
/*
Package bit aims to provide feature parity with stdlib's [encoding/hex].
It's a ludicrous tragedy that hex/base16, base32, base64 all have libraries for converting
to/from string representations... but there's nothing for binary ('01010001' etc.) whatsoever.
This package also provides some extra convenience functions and types in an attempt to provide
an abstracted bit-level fidelity in Go. A [Bit] is a bool type, in which that underlying bool
being false represents a 0 and that underlying bool being true represents a 1.
Note that a [Bit] or arbitrary-length or non-octal-aligned [][Bit] may take up more bytes in memory
than expected; a [Bit] will actually always occupy a single byte -- thus representing
`00000000 00000000` as a [][Bit] or [16][Bit] will actually occupy *sixteen bytes* in memory,
NOT 2 bytes (nor, obviously, [2][Byte])!
It is recommended instead to use a [Bits] instead of a [Bit] slice or array, as it will try to properly align to the
smallest memory allocation possible (at the cost of a few extra CPU cycles on adding/removing one or more [Bit]).
It will properly retain any appended, prepended, leading, or trailing bits that do not currently align to a byte.
*/
package bit

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@@ -0,0 +1,14 @@
package bit
// TODO: Provide analogues of encoding/hex, encoding/base64, etc. functions etc.
/*
TODO: Also provide interfaces for the following:
* https://pkg.go.dev/encoding#BinaryAppender
* https://pkg.go.dev/encoding#BinaryMarshaler
* https://pkg.go.dev/encoding#BinaryUnmarshaler
* https://pkg.go.dev/encoding#TextAppender
* https://pkg.go.dev/encoding#TextMarshaler
* https://pkg.go.dev/encoding#TextUnmarshaler
*/

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@@ -0,0 +1,34 @@
package bit
type (
// Bit aims to provide a native-like type for a single bit (Golang operates on the smallest fidelity level of *byte*/uint8).
Bit bool
// Bits is an arbitrary length of bits.
Bits struct {
/*
leading is a series of Bit that do not cleanly align to the beginning of Bits.b.
They will always be the bits at the *beginning* of the sequence.
len(Bits.leading) will *never* be more than 7;
it's converted into a byte, prepended to Bits.b, and cleared if it reaches that point.
*/
leading []Bit
// b is the condensed/memory-aligned alternative to an [][8]Bit (or []Bit, or [][]Bit, etc.).
b []byte
/*
remaining is a series of Bit that do not cleanly align to the end of Bits.b.
They will always be the bits at the *end* of the sequence.
len(Bits.remaining) will *never* be more than 7;
it's converted into a byte, appended to Bits.b, and cleared if it reaches that point.
*/
remaining []Bit
// fixedLen, if 0, represents a "slice". If >= 1, it represents an "array".
fixedLen uint
}
// Byte is this package's representation of a byte. It's primarily for convenience.
Byte byte
// Bytes is defined as a type for convenience single-call functions.
Bytes []Byte
)

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@@ -34,11 +34,47 @@ func NewMaskBitExplicit(value uint) (m *MaskBit) {
return
}
// HasFlag is true if m has MaskBit flag set/enabled.
/*
HasFlag is true if m has MaskBit flag set/enabled.
THIS WILL RETURN FALSE FOR OR'd FLAGS.
For example:
flagA MaskBit = 0x01
flagB MaskBit = 0x02
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.)
*/
func (m *MaskBit) HasFlag(flag MaskBit) (r bool) {
var b MaskBit = *m
if b&flag == flag {
r = true
}
return
}
/*
IsOneOf is like a "looser" form of [MaskBit.HasFlag]
in that it allows for testing composite membership.
See [MaskBit.HasFlag] for more information.
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.
*/
func (m *MaskBit) IsOneOf(composite MaskBit) (r bool) {
var b MaskBit = *m
if b&flag != 0 {
r = true
}