Initial commit

vendor/github.com/cockroachdb/redact/internal/fmtforward/make_format.go

@@ -0,0 +1,88 @@
+// Copyright 2020 The Cockroach Authors.
+//
+// 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 fmtforward
+
+import (
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+)
+
+// ReproducePrintf calls fmt.Print/fmt.Printf on the argument
+// based on the details present in the fmt.State and
+// writes to the io.Writer.
+func ReproducePrintf(w io.Writer, s fmt.State, verb rune, arg interface{}) {
+	justV, revFmt := MakeFormat(s, verb)
+	if justV {
+		// Common case, avoids generating then parsing the format again.
+		fmt.Fprint(w, arg)
+	} else {
+		fmt.Fprintf(w, revFmt, arg)
+	}
+}
+
+// MakeFormat reproduces the format currently active
+// in fmt.State and verb. This is provided because Go's standard
+// fmt.State does not make the original format string available to us.
+//
+// If the return value justV is true, then the current state
+// was found to be %v exactly; in that case the caller
+// can avoid a full-blown Printf call and use just Print instead
+// to take a shortcut.
+func MakeFormat(s fmt.State, verb rune) (justV bool, format string) {
+	plus, minus, hash, sp, z := s.Flag('+'), s.Flag('-'), s.Flag('#'), s.Flag(' '), s.Flag('0')
+	w, wp := s.Width()
+	p, pp := s.Precision()
+
+	if !plus && !minus && !hash && !sp && !z && !wp && !pp {
+		switch verb {
+		case 'v':
+			return true, "%v"
+		case 's':
+			return false, "%s"
+		case 'd':
+			return false, "%d"
+		}
+		// Other cases handled in the slow path below.
+	}
+
+	var f strings.Builder
+	f.WriteByte('%')
+	if plus {
+		f.WriteByte('+')
+	}
+	if minus {
+		f.WriteByte('-')
+	}
+	if hash {
+		f.WriteByte('#')
+	}
+	if sp {
+		f.WriteByte(' ')
+	}
+	if z {
+		f.WriteByte('0')
+	}
+	if wp {
+		f.WriteString(strconv.Itoa(w))
+	}
+	if pp {
+		f.WriteByte('.')
+		f.WriteString(strconv.Itoa(p))
+	}
+	f.WriteRune(verb)
+	return false, f.String()
+}