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// Copyright The Notary Project 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 io provides a LimitWriter that writes to an underlying writer up to
// a limit.
package io
import (
"errors"
"io"
)
// ErrLimitExceeded is returned when the write limit is exceeded.
var ErrLimitExceeded = errors.New("write limit exceeded")
// LimitedWriter is a writer that writes to an underlying writer up to a limit.
type LimitedWriter struct {
W io.Writer // underlying writer
N int64 // remaining bytes
}
// LimitWriter returns a new LimitWriter that writes to w.
//
// parameters:
// w: the writer to write to
// limit: the maximum number of bytes to write
func LimitWriter(w io.Writer, limit int64) *LimitedWriter {
return &LimitedWriter{W: w, N: limit}
}
// Write writes p to the underlying writer up to the limit.
func (l *LimitedWriter) Write(p []byte) (int, error) {
if l.N <= 0 {
return 0, ErrLimitExceeded
}
if int64(len(p)) > l.N {
p = p[:l.N]
}
n, err := l.W.Write(p)
l.N -= int64(n)
return n, err
}
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