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  }