feat: Waku v2 bridge

Issue #12610

vendor/github.com/russolsen/transit/rolling_cache.go

@@ -0,0 +1,128 @@
+// Copyright 2016 Russ Olsen. All Rights Reserved.
+//
+// This code is a Go port of the Java version created and maintained by Cognitect, therefore:
+//
+// Copyright 2014 Cognitect. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS-IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package transit
+
+import (
+	"fmt"
+)
+
+const cacheCodeDigits = 44
+const baseCharIndex = 48
+const firstOrd = 48
+const cacheSize = (cacheCodeDigits * cacheCodeDigits)
+const minSizeCacheable = 4
+
+type StringMap map[string]string
+
+type RollingCache struct {
+	keyToValue StringMap
+	valueToKey StringMap
+}
+
+func NewRollingCache() *RollingCache {
+	return &RollingCache{keyToValue: make(StringMap), valueToKey: make(StringMap)}
+}
+
+func (rc *RollingCache) String() string {
+	return fmt.Sprintf("Cache: %v", rc.keyToValue)
+}
+
+func (rc *RollingCache) HasKey(name string) bool {
+	_, present := rc.keyToValue[name]
+	return present
+}
+
+func (rc *RollingCache) Read(name string) string {
+	return rc.keyToValue[name]
+}
+
+// Enter the name into the cache if it passes the cacheable critieria.
+// Returns either the name or the value that was previously cached for
+// the name.
+func (rc *RollingCache) Write(name string) string {
+	existing_key, present := rc.valueToKey[name]
+
+	if present {
+		return existing_key
+	}
+
+	if rc.isCacheFull() {
+		rc.Clear()
+	}
+
+	var key = rc.encodeKey(len(rc.keyToValue))
+	rc.keyToValue[key] = name
+	rc.valueToKey[name] = key
+
+	return name
+}
+
+// IsCacheable returns true if the string is long enough to be cached
+// and either asKey is true or the string represents a symbol, keyword
+// or tag.
+func (rc *RollingCache) IsCacheable(s string, asKey bool) bool {
+	if len(s) < minSizeCacheable {
+		return false
+	} else if asKey {
+		return true
+	} else {
+		var firstTwo = s[0:2]
+		//return firstTwo == "~#" || firstTwo == "~$" || firstTwo == "~:"
+		return firstTwo == startTag || firstTwo == startKW || firstTwo == startSym
+	}
+}
+
+// IsCacheKey returns true if the string looks like a cache key.
+func (rc *RollingCache) IsCacheKey(name string) bool {
+	if len(name) == 0 {
+		return false
+	} else if (name[0:1] == sub) && (name != mapAsArray) {
+		return true
+	} else {
+		return false
+	}
+}
+
+func (rc *RollingCache) encodeKey(index int) string {
+	var hi = index / cacheCodeDigits
+	var lo = index % cacheCodeDigits
+	if hi == 0 {
+		return sub + string(lo+baseCharIndex)
+	} else {
+		return sub + string(hi+baseCharIndex) + string(lo+baseCharIndex)
+	}
+}
+
+func (rc *RollingCache) codeToIndex(s string) int {
+	var sz = len(s)
+	if sz == 2 {
+		return int(s[1]) - baseCharIndex
+	} else {
+		return ((int(s[1]) - baseCharIndex) * cacheCodeDigits) + (int(s[2]) - baseCharIndex)
+	}
+}
+
+func (rc *RollingCache) isCacheFull() bool {
+	return len(rc.keyToValue) >= cacheSize
+}
+
+func (rc *RollingCache) Clear() {
+	rc.valueToKey = make(StringMap)
+	rc.keyToValue = make(StringMap)
+}