pkg/jsonlog: add JSONLogBytes for low allocations

Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com>

jsonlog/jsonlogbytes.go

@@ -0,0 +1,115 @@
+package jsonlog
+
+import (
+	"bytes"
+	"unicode/utf8"
+)
+
+// JSONLogBytes is based on JSONLog.
+// It allows marshalling JSONLog from Log as []byte
+// and an already marshalled Created timestamp.
+type JSONLogBytes struct {
+	Log     []byte `json:"log,omitempty"`
+	Stream  string `json:"stream,omitempty"`
+	Created string `json:"time"`
+}
+
+// MarshalJSONBuf is based on the same method from JSONLog
+// It has been modified to take into account the necessary changes.
+func (mj *JSONLogBytes) MarshalJSONBuf(buf *bytes.Buffer) error {
+	var first = true
+
+	buf.WriteString(`{`)
+	if len(mj.Log) != 0 {
+		if first == true {
+			first = false
+		} else {
+			buf.WriteString(`,`)
+		}
+		buf.WriteString(`"log":`)
+		ffjson_WriteJsonBytesAsString(buf, mj.Log)
+	}
+	if len(mj.Stream) != 0 {
+		if first == true {
+			first = false
+		} else {
+			buf.WriteString(`,`)
+		}
+		buf.WriteString(`"stream":`)
+		ffjson_WriteJsonString(buf, mj.Stream)
+	}
+	if first == true {
+		first = false
+	} else {
+		buf.WriteString(`,`)
+	}
+	buf.WriteString(`"time":`)
+	buf.WriteString(mj.Created)
+	buf.WriteString(`}`)
+	return nil
+}
+
+// This is based on ffjson_WriteJsonString. It has been changed
+// to accept a string passed as a slice of bytes.
+func ffjson_WriteJsonBytesAsString(buf *bytes.Buffer, s []byte) {
+	const hex = "0123456789abcdef"
+
+	buf.WriteByte('"')
+	start := 0
+	for i := 0; i < len(s); {
+		if b := s[i]; b < utf8.RuneSelf {
+			if 0x20 <= b && b != '\\' && b != '"' && b != '<' && b != '>' && b != '&' {
+				i++
+				continue
+			}
+			if start < i {
+				buf.Write(s[start:i])
+			}
+			switch b {
+			case '\\', '"':
+				buf.WriteByte('\\')
+				buf.WriteByte(b)
+			case '\n':
+				buf.WriteByte('\\')
+				buf.WriteByte('n')
+			case '\r':
+				buf.WriteByte('\\')
+				buf.WriteByte('r')
+			default:
+
+				buf.WriteString(`\u00`)
+				buf.WriteByte(hex[b>>4])
+				buf.WriteByte(hex[b&0xF])
+			}
+			i++
+			start = i
+			continue
+		}
+		c, size := utf8.DecodeRune(s[i:])
+		if c == utf8.RuneError && size == 1 {
+			if start < i {
+				buf.Write(s[start:i])
+			}
+			buf.WriteString(`\ufffd`)
+			i += size
+			start = i
+			continue
+		}
+
+		if c == '\u2028' || c == '\u2029' {
+			if start < i {
+				buf.Write(s[start:i])
+			}
+			buf.WriteString(`\u202`)
+			buf.WriteByte(hex[c&0xF])
+			i += size
+			start = i
+			continue
+		}
+		i += size
+	}
+	if start < len(s) {
+		buf.Write(s[start:])
+	}
+	buf.WriteByte('"')
+}