feat: Add configurable size limit to recycled Parsers in pool

parser_test.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"math"
 	"strings"
+	"sync"
 	"testing"
 	"time"
 )
@@ -188,6 +189,35 @@ func TestParserPool(t *testing.T) {
 	}
 }
 
+func TestParserPoolMaxSize(t *testing.T) {
+	var numNew, numNewLimit int
+	ppr := &ParserPool{
+		sync.Pool{New: func() interface{} { numNew++; return new(Parser) }},
+	}
+	pprLimit := &ParserPool{
+		sync.Pool{New: func() interface{} { numNewLimit++; return new(Parser) }},
+	}
+
+	parse := func(ppr *ParserPool, maxSize int, index int) {
+		var json = fmt.Sprintf(`{"%d":"test"}`, index)
+		pr := ppr.Get()
+		_, _ = pr.Parse(json)
+		ppr.PutIfSizeLessThan(pr, maxSize)
+	}
+	for i := 0; i < 10; i++ {
+		parse(ppr, 0, i)
+		parse(pprLimit, 1, i)
+	}
+
+	if numNew != 1 {
+		t.Fatalf("Expected exactly 1 calls to Pool New with no Max Size (not %d)", numNew)
+	}
+
+	if numNewLimit != 10 {
+		t.Fatalf("Expected exactly 10 calls to Pool with a Max Size (not %d)", numNewLimit)
+	}
+}
+
 func TestValueInvalidTypeConversion(t *testing.T) {
 	var p Parser
 

pool.go

@@ -28,6 +28,19 @@ func (pp *ParserPool) Put(p *Parser) {
 	pp.pool.Put(p)
 }
 
+// PutIfSizeLessThan PutIfLessThan Put returns p to pp only if the number of values in the cache is less than maxSize.
+// If set to <= 0, no size limit is applied.
+//
+// p and objects recursively returned from p cannot be used after p is put into pp or released
+func (pp *ParserPool) PutIfSizeLessThan(p *Parser, maxSize int) {
+	// Release the parser if the cache is too big
+	if maxSize > 0 && cap(p.c.vs) > maxSize {
+		return
+	}
+
+	pp.pool.Put(p)
+}
+
 // ArenaPool may be used for pooling Arenas for similarly typed JSONs.
 type ArenaPool struct {
 	pool sync.Pool