Pull request 2020: AG-26236-ring-buffer

Squashed commit of the following:

commit 4b9cc9ddf52739fc5f918babedc99ac7ac0e2415
Merge: a6259ed57 39aeaf891
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Tue Oct 3 20:39:58 2023 +0300

    Merge branch 'master' into AG-26236-ring-buffer

commit a6259ed5758156e4110ee3ea6a49760d2880ade3
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Tue Oct 3 20:30:20 2023 +0300

    querylog: imp code

commit 40f9f7cd5a1cff22bcb858020f2cfa9be8399671
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Tue Oct 3 20:11:49 2023 +0300

    querylog: fix typo

commit 1aabbadcb5fcbe6a95945c5bd1455b956b85a8d0
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Tue Oct 3 20:05:22 2023 +0300

    querylog: imp err msg

commit 02913d35b43e190e42765823ccfcdd332839e984
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Tue Oct 3 19:37:47 2023 +0300

    aghalg: imp tests

commit 98a7909088d2a65b78afa9fa3113545c94429e65
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Tue Oct 3 19:23:10 2023 +0300

    all: imp tests

commit e147804eeafe89e5020cd917784eef3ff2b310d0
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Tue Oct 3 18:49:49 2023 +0300

    all: imp code

commit 5f21f2f63b7bce89f2bc79c97c7350cd693c956b
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Tue Oct 3 14:39:43 2023 +0300

    all: add tests

commit 35a45c7dc5d5961f6987da7c69249c56e54e97f5
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Mon Oct 2 17:43:09 2023 +0300

    all: imp code

commit 21e51fcbe411258eaf830825df9d05b7ddcc187a
Author: Stanislav Chzhen <s.chzhen@adguard.com>
Date:   Fri Sep 29 18:21:00 2023 +0300

    all: add ring buffer

internal/aghalg/ringbuffer.go

@@ -0,0 +1,102 @@
+package aghalg
+
+import (
+	"github.com/AdguardTeam/golibs/errors"
+)
+
+// RingBuffer is the implementation of ring buffer data structure.
+type RingBuffer[T any] struct {
+	buf  []T
+	cur  int
+	full bool
+}
+
+// NewRingBuffer initializes the new instance of ring buffer.  size must be
+// greater or equal to zero.
+func NewRingBuffer[T any](size int) (rb *RingBuffer[T]) {
+	if size < 0 {
+		panic(errors.Error("ring buffer: size must be greater or equal to zero"))
+	}
+
+	return &RingBuffer[T]{
+		buf: make([]T, size),
+	}
+}
+
+// Append appends an element to the buffer.
+func (rb *RingBuffer[T]) Append(e T) {
+	if len(rb.buf) == 0 {
+		return
+	}
+
+	rb.buf[rb.cur] = e
+	rb.cur = (rb.cur + 1) % cap(rb.buf)
+	if rb.cur == 0 {
+		rb.full = true
+	}
+}
+
+// Range calls cb for each element of the buffer.  If cb returns false it stops.
+func (rb *RingBuffer[T]) Range(cb func(T) (cont bool)) {
+	before, after := rb.splitCur()
+
+	for _, e := range before {
+		if !cb(e) {
+			return
+		}
+	}
+
+	for _, e := range after {
+		if !cb(e) {
+			return
+		}
+	}
+}
+
+// ReverseRange calls cb for each element of the buffer in reverse order.  If
+// cb returns false it stops.
+func (rb *RingBuffer[T]) ReverseRange(cb func(T) (cont bool)) {
+	before, after := rb.splitCur()
+
+	for i := len(after) - 1; i >= 0; i-- {
+		if !cb(after[i]) {
+			return
+		}
+	}
+
+	for i := len(before) - 1; i >= 0; i-- {
+		if !cb(before[i]) {
+			return
+		}
+	}
+}
+
+// splitCur splits the buffer in two, before and after current position in
+// chronological order.  If buffer is not full, after is nil.
+func (rb *RingBuffer[T]) splitCur() (before, after []T) {
+	if len(rb.buf) == 0 {
+		return nil, nil
+	}
+
+	cur := rb.cur
+	if !rb.full {
+		return rb.buf[:cur], nil
+	}
+
+	return rb.buf[cur:], rb.buf[:cur]
+}
+
+// Len returns a length of the buffer.
+func (rb *RingBuffer[T]) Len() (l int) {
+	if !rb.full {
+		return rb.cur
+	}
+
+	return cap(rb.buf)
+}
+
+// Clear clears the buffer.
+func (rb *RingBuffer[T]) Clear() {
+	rb.full = false
+	rb.cur = 0
+}