// Copyright 2019 The Prometheus 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 util

import (
	"io"
	"io/ioutil"
	"os"
)

// ReadFileNoStat uses ioutil.ReadAll to read contents of entire file.
// This is similar to ioutil.ReadFile but without the call to os.Stat, because
// many files in /proc and /sys report incorrect file sizes (either 0 or 4096).
// Reads a max file size of 512kB.  For files larger than this, a scanner
// should be used.
func ReadFileNoStat(filename string) ([]byte, error) {
	const maxBufferSize = 1024 * 512

	f, err := os.Open(filename)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	reader := io.LimitReader(f, maxBufferSize)
	return ioutil.ReadAll(reader)
}
