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57 lines
2.0 KiB
Go
57 lines
2.0 KiB
Go
// Copyright (c) 2015-2023 MinIO, Inc.
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//
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// This file is part of MinIO Object Storage stack
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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// Package ioutil implements some I/O utility functions which are not covered
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// by the standard library.
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package ioutil
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import (
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"errors"
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"io"
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)
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// ErrOverread is returned to the reader when the hard limit of HardLimitReader is exceeded.
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var ErrOverread = errors.New("input provided more bytes than specified")
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// HardLimitReader returns a Reader that reads from r
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// but returns an error if the source provides more data than allowed.
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// This means the source *will* be overread unless EOF is returned prior.
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// The underlying implementation is a *HardLimitedReader.
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// This will ensure that at most n bytes are returned and EOF is reached.
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func HardLimitReader(r io.Reader, n int64) io.Reader { return &HardLimitedReader{r, n} }
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// A HardLimitedReader reads from R but limits the amount of
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// data returned to just N bytes. Each call to Read
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// updates N to reflect the new amount remaining.
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// Read returns EOF when N <= 0 or when the underlying R returns EOF.
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type HardLimitedReader struct {
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R io.Reader // underlying reader
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N int64 // max bytes remaining
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}
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func (l *HardLimitedReader) Read(p []byte) (n int, err error) {
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if l.N < 0 {
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return 0, ErrOverread
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}
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n, err = l.R.Read(p)
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l.N -= int64(n)
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if l.N < 0 {
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return 0, ErrOverread
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}
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return
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}
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