tools/src/utils/prefix_writer.go

// Copyright 2023 The Dawn & Tint Authors
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer.
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// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
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// 3. Neither the name of the copyright holder nor the names of its
//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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package utils

import (
	"io"
	"strings"
)

// PrefixWriter is an io.Writer that prefixes each write with a prefix string
type PrefixWriter struct {
	Prefix string
	Writer io.Writer
}

func (p *PrefixWriter) Write(data []byte) (int, error) {
	lines := strings.Split(string(data), "\n")
	buf := strings.Builder{}
	for i, line := range lines {
		if line == "" && i == len(lines)-1 {
			break
		}
		buf.WriteString(p.Prefix)
		buf.WriteString(line)
		buf.WriteString("\n")
	}
	if _, err := p.Writer.Write([]byte(buf.String())); err != nil {
		return 0, err
	}
	return len(data), nil
}