github.com/ovsinc/prototool@v1.3.0/internal/format/printer.go (about) 1 // Copyright (c) 2018 Uber Technologies, Inc. 2 // 3 // Permission is hereby granted, free of charge, to any person obtaining a copy 4 // of this software and associated documentation files (the "Software"), to deal 5 // in the Software without restriction, including without limitation the rights 6 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 7 // copies of the Software, and to permit persons to whom the Software is 8 // furnished to do so, subject to the following conditions: 9 // 10 // The above copyright notice and this permission notice shall be included in 11 // all copies or substantial portions of the Software. 12 // 13 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 14 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 15 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 16 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 17 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 18 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 19 // THE SOFTWARE. 20 21 package format 22 23 import ( 24 "bytes" 25 "fmt" 26 "strings" 27 ) 28 29 const indentString = " " 30 31 // printer is a convenience struct that helps when printing proto files. 32 // The concept was taken from the golang/protobuf plugin. 33 type printer struct { 34 buffer *bytes.Buffer 35 indentCount int 36 } 37 38 func newPrinter() *printer { 39 return &printer{bytes.NewBuffer(nil), 0} 40 } 41 42 // P prints the args concatenated on the same line after printing the current indent and then prints a newline. 43 // 44 // TODO: There is a lot of unnecessary memory allocation going on here, optimize 45 func (p *printer) P(args ...interface{}) { 46 lineBuffer := bytes.NewBuffer(nil) 47 if p.indentCount > 0 { 48 _, _ = fmt.Fprint(lineBuffer, strings.Repeat(indentString, p.indentCount)) 49 } 50 for _, arg := range args { 51 _, _ = fmt.Fprint(lineBuffer, arg) 52 } 53 line := lineBuffer.Bytes() 54 55 if len(bytes.TrimSpace(line)) != 0 { 56 _, _ = p.buffer.Write(line) 57 } 58 _, _ = p.buffer.WriteRune('\n') 59 } 60 61 // In adds one indent. 62 func (p *printer) In() { 63 p.indentCount++ 64 } 65 66 // Out deletes one indent. 67 func (p *printer) Out() { 68 // might want to error 69 if p.indentCount > 0 { 70 p.indentCount-- 71 } 72 } 73 74 // Bytes returns the printed bytes. 75 func (p *printer) Bytes() []byte { 76 return p.buffer.Bytes() 77 }