files.go

/*
 Copyright 2019 Padduck, LLC
  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 apufferi

import (
	"errors"
	"io"
	"os"
	"path/filepath"
	"strings"
)

const MaxRecursivePath = 256

func JoinPath(paths ...string) string {
	result, _ := filepath.Abs(filepath.Join(paths...))
	return result
}

func EnsureAccess(source string, prefix string) bool {
	replacement, err := findFullPath(source)
	if err != nil && !os.IsNotExist(err) {
		return false
	} else if os.IsNotExist(err) {
		replacement, err = filepath.Abs(source)
		if err != nil {
			return false
		}
	}

	return strings.HasPrefix(replacement, prefix)
}

func RemoveInvalidSymlinks(files []os.FileInfo, sourceFolder, prefix string) []os.FileInfo {
	i := 0
	for _, v := range files {
		if v.Mode()&os.ModeSymlink != 0 {
			if !EnsureAccess(sourceFolder+string(os.PathSeparator)+v.Name(), prefix) {
				continue
			}
		}
		files[i] = v
		i++
	}

	return files[:i]
}

func CopyFile(src, dest string) error {
	source, err := os.Open(src)
	if err != nil {
		return err
	}
	defer Close(source)

	err = os.MkdirAll(filepath.Dir(dest), 0755)
	if err != nil {
		return err
	}
	destination, err := os.Create(dest)
	if err != nil {
		return err
	}
	defer Close(destination)
	_, err = io.Copy(destination, source)
	return err
}

func findFullPath(source string) (string, error) {
	fullPath, err := filepath.EvalSymlinks(source)

	if err == nil {
		return fullPath, err
	}

	//if file doesn't exist, then filepath doesn't resolve properly, so check backwards
	if os.IsNotExist(err) {
		var updatePath string
		dir, filename := filepath.Split(source)
		suffix := string(os.PathSeparator) + filename

		i := 0
		for i < MaxRecursivePath && dir != "" {
			dirFullPath, err := filepath.EvalSymlinks(dir)
			if err != nil && os.IsNotExist(err) {
				//update our mapping to look farther down
				suffix = filepath.Base(dir) + string(os.PathSeparator) + suffix
				dir = filepath.Dir(dir)
			} else if err != nil {
				return "", err
			} else {
				//we found a good path!
				updatePath = dirFullPath + string(os.PathSeparator) + suffix
				break
			}
			i++

			if i == MaxRecursivePath {
				return "", errors.New("path too recursive")
			}
		}

		updatePath, err := filepath.Abs(updatePath)
		return updatePath, err

	}

	return "", err
}