From a32fb3880e9d859a5430c0a0d50d63dd511f4a75 Mon Sep 17 00:00:00 2001 From: Daniel Date: Thu, 13 May 2021 17:38:13 +0200 Subject: [PATCH] Fork github.com/google/renameio --- utils/renameio/LICENSE | 202 ++++++++++++++++++++++++++ utils/renameio/README.md | 55 +++++++ utils/renameio/doc.go | 21 +++ utils/renameio/example_test.go | 67 +++++++++ utils/renameio/symlink_test.go | 52 +++++++ utils/renameio/tempfile.go | 181 +++++++++++++++++++++++ utils/renameio/tempfile_linux_test.go | 111 ++++++++++++++ utils/renameio/writefile.go | 38 +++++ utils/renameio/writefile_test.go | 57 ++++++++ 9 files changed, 784 insertions(+) create mode 100644 utils/renameio/LICENSE create mode 100644 utils/renameio/README.md create mode 100644 utils/renameio/doc.go create mode 100644 utils/renameio/example_test.go create mode 100644 utils/renameio/symlink_test.go create mode 100644 utils/renameio/tempfile.go create mode 100644 utils/renameio/tempfile_linux_test.go create mode 100644 utils/renameio/writefile.go create mode 100644 utils/renameio/writefile_test.go diff --git a/utils/renameio/LICENSE b/utils/renameio/LICENSE new file mode 100644 index 0000000..d645695 --- /dev/null +++ b/utils/renameio/LICENSE @@ -0,0 +1,202 @@ + + Apache License + Version 2.0, January 2004 + http://www.apache.org/licenses/ + + TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION + + 1. Definitions. + + "License" shall mean the terms and conditions for use, reproduction, + and distribution as defined by Sections 1 through 9 of this document. + + "Licensor" shall mean the copyright owner or entity authorized by + the copyright owner that is granting the License. + + "Legal Entity" shall mean the union of the acting entity and all + other entities that control, are controlled by, or are under common + control with that entity. For the purposes of this definition, + "control" means (i) the power, direct or indirect, to cause the + direction or management of such entity, whether by contract or + otherwise, or (ii) ownership of fifty percent (50%) or more of the + outstanding shares, or (iii) beneficial ownership of such entity. + + "You" (or "Your") shall mean an individual or Legal Entity + exercising permissions granted by this License. + + "Source" form shall mean the preferred form for making modifications, + including but not limited to software source code, documentation + source, and configuration files. + + "Object" form shall mean any form resulting from mechanical + transformation or translation of a Source form, including but + not limited to compiled object code, generated documentation, + and conversions to other media types. + + "Work" shall mean the work of authorship, whether in Source or + Object form, made available under the License, as indicated by a + copyright notice that is included in or attached to the work + (an example is provided in the Appendix below). + + "Derivative Works" shall mean any work, whether in Source or Object + form, that is based on (or derived from) the Work and for which the + editorial revisions, annotations, elaborations, or other modifications + represent, as a whole, an original work of authorship. For the purposes + of this License, Derivative Works shall not include works that remain + separable from, or merely link (or bind by name) to the interfaces of, + the Work and Derivative Works thereof. + + "Contribution" shall mean any work of authorship, including + the original version of the Work and any modifications or additions + to that Work or Derivative Works thereof, that is intentionally + submitted to Licensor for inclusion in the Work by the copyright owner + or by an individual or Legal Entity authorized to submit on behalf of + the copyright owner. For the purposes of this definition, "submitted" + means any form of electronic, verbal, or written communication sent + to the Licensor or its representatives, including but not limited to + communication on electronic mailing lists, source code control systems, + and issue tracking systems that are managed by, or on behalf of, the + Licensor for the purpose of discussing and improving the Work, but + excluding communication that is conspicuously marked or otherwise + designated in writing by the copyright owner as "Not a Contribution." + + "Contributor" shall mean Licensor and any individual or Legal Entity + on behalf of whom a Contribution has been received by Licensor and + subsequently incorporated within the Work. + + 2. Grant of Copyright License. Subject to the terms and conditions of + this License, each Contributor hereby grants to You a perpetual, + worldwide, non-exclusive, no-charge, royalty-free, irrevocable + copyright license to reproduce, prepare Derivative Works of, + publicly display, publicly perform, sublicense, and distribute the + Work and such Derivative Works in Source or Object form. + + 3. Grant of Patent License. Subject to the terms and conditions of + this License, each Contributor hereby grants to You a perpetual, + worldwide, non-exclusive, no-charge, royalty-free, irrevocable + (except as stated in this section) patent license to make, have made, + use, offer to sell, sell, import, and otherwise transfer the Work, + where such license applies only to those patent claims licensable + by such Contributor that are necessarily infringed by their + Contribution(s) alone or by combination of their Contribution(s) + with the Work to which such Contribution(s) was submitted. If You + institute patent litigation against any entity (including a + cross-claim or counterclaim in a lawsuit) alleging that the Work + or a Contribution incorporated within the Work constitutes direct + or contributory patent infringement, then any patent licenses + granted to You under this License for that Work shall terminate + as of the date such litigation is filed. + + 4. Redistribution. You may reproduce and distribute copies of the + Work or Derivative Works thereof in any medium, with or without + modifications, and in Source or Object form, provided that You + meet the following conditions: + + (a) You must give any other recipients of the Work or + Derivative Works a copy of this License; and + + (b) You must cause any modified files to carry prominent notices + stating that You changed the files; and + + (c) You must retain, in the Source form of any Derivative Works + that You distribute, all copyright, patent, trademark, and + attribution notices from the Source form of the Work, + excluding those notices that do not pertain to any part of + the Derivative Works; and + + (d) If the Work includes a "NOTICE" text file as part of its + distribution, then any Derivative Works that You distribute must + include a readable copy of the attribution notices contained + within such NOTICE file, excluding those notices that do not + pertain to any part of the Derivative Works, in at least one + of the following places: within a NOTICE text file distributed + as part of the Derivative Works; within the Source form or + documentation, if provided along with the Derivative Works; or, + within a display generated by the Derivative Works, if and + wherever such third-party notices normally appear. The contents + of the NOTICE file are for informational purposes only and + do not modify the License. You may add Your own attribution + notices within Derivative Works that You distribute, alongside + or as an addendum to the NOTICE text from the Work, provided + that such additional attribution notices cannot be construed + as modifying the License. + + You may add Your own copyright statement to Your modifications and + may provide additional or different license terms and conditions + for use, reproduction, or distribution of Your modifications, or + for any such Derivative Works as a whole, provided Your use, + reproduction, and distribution of the Work otherwise complies with + the conditions stated in this License. + + 5. Submission of Contributions. Unless You explicitly state otherwise, + any Contribution intentionally submitted for inclusion in the Work + by You to the Licensor shall be under the terms and conditions of + this License, without any additional terms or conditions. + Notwithstanding the above, nothing herein shall supersede or modify + the terms of any separate license agreement you may have executed + with Licensor regarding such Contributions. + + 6. Trademarks. This License does not grant permission to use the trade + names, trademarks, service marks, or product names of the Licensor, + except as required for reasonable and customary use in describing the + origin of the Work and reproducing the content of the NOTICE file. + + 7. Disclaimer of Warranty. Unless required by applicable law or + agreed to in writing, Licensor provides the Work (and each + Contributor provides its Contributions) on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or + implied, including, without limitation, any warranties or conditions + of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A + PARTICULAR PURPOSE. You are solely responsible for determining the + appropriateness of using or redistributing the Work and assume any + risks associated with Your exercise of permissions under this License. + + 8. Limitation of Liability. In no event and under no legal theory, + whether in tort (including negligence), contract, or otherwise, + unless required by applicable law (such as deliberate and grossly + negligent acts) or agreed to in writing, shall any Contributor be + liable to You for damages, including any direct, indirect, special, + incidental, or consequential damages of any character arising as a + result of this License or out of the use or inability to use the + Work (including but not limited to damages for loss of goodwill, + work stoppage, computer failure or malfunction, or any and all + other commercial damages or losses), even if such Contributor + has been advised of the possibility of such damages. + + 9. Accepting Warranty or Additional Liability. While redistributing + the Work or Derivative Works thereof, You may choose to offer, + and charge a fee for, acceptance of support, warranty, indemnity, + or other liability obligations and/or rights consistent with this + License. However, in accepting such obligations, You may act only + on Your own behalf and on Your sole responsibility, not on behalf + of any other Contributor, and only if You agree to indemnify, + defend, and hold each Contributor harmless for any liability + incurred by, or claims asserted against, such Contributor by reason + of your accepting any such warranty or additional liability. + + END OF TERMS AND CONDITIONS + + APPENDIX: How to apply the Apache License to your work. + + To apply the Apache License to your work, attach the following + boilerplate notice, with the fields enclosed by brackets "[]" + replaced with your own identifying information. (Don't include + the brackets!) The text should be enclosed in the appropriate + comment syntax for the file format. We also recommend that a + file or class name and description of purpose be included on the + same "printed page" as the copyright notice for easier + identification within third-party archives. + + Copyright [yyyy] [name of copyright owner] + + 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. diff --git a/utils/renameio/README.md b/utils/renameio/README.md new file mode 100644 index 0000000..91e0b29 --- /dev/null +++ b/utils/renameio/README.md @@ -0,0 +1,55 @@ +This is a fork of the github.com/google/renameio Go package at commit 353f8196982447d8b12c64f69530e657331e3dbc. + +The inital commit of this package will carry the original package contents. +The Original License is the Apache License in Version 2.0 and the copyright of the forked package is held by Google Inc. +Any changes are recorded in the git history, which is part of this project. + +--- + +The `renameio` Go package provides a way to atomically create or replace a file or +symbolic link. + +## Atomicity vs durability + +`renameio` concerns itself *only* with atomicity, i.e. making sure applications +never see unexpected file content (a half-written file, or a 0-byte file). + +As a practical example, consider https://manpages.debian.org/: if there is a +power outage while the site is updating, we are okay with losing the manpages +which were being rendered at the time of the power outage. They will be added in +a later run of the software. We are not okay with having a manpage replaced by a +0-byte file under any circumstances, though. + +## Advantages of this package + +There are other packages for atomically replacing files, and sometimes ad-hoc +implementations can be found in programs. + +A naive approach to the problem is to create a temporary file followed by a call +to `os.Rename()`. However, there are a number of subtleties which make the +correct sequence of operations hard to identify: + +* The temporary file should be removed when an error occurs, but a remove must + not be attempted if the rename succeeded, as a new file might have been + created with the same name. This renders a throwaway `defer + os.Remove(t.Name())` insufficient; state must be kept. + +* The temporary file must be created on the same file system (same mount point) + for the rename to work, but the TMPDIR environment variable should still be + respected, e.g. to direct temporary files into a separate directory outside of + the webserver’s document root but on the same file system. + +* On POSIX operating systems, the + [`fsync`](https://manpages.debian.org/stretch/manpages-dev/fsync.2) system + call must be used to ensure that the `os.Rename()` call will not result in a + 0-length file. + +This package attempts to get all of these details right, provides an intuitive, +yet flexible API and caters to use-cases where high performance is required. + +## Disclaimer + +This is not an official Google product (experimental or otherwise), it +is just code that happens to be owned by Google. + +This project is not affiliated with the Go project. diff --git a/utils/renameio/doc.go b/utils/renameio/doc.go new file mode 100644 index 0000000..67416df --- /dev/null +++ b/utils/renameio/doc.go @@ -0,0 +1,21 @@ +// Copyright 2018 Google Inc. +// +// 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 renameio provides a way to atomically create or replace a file or +// symbolic link. +// +// Caveat: this package requires the file system rename(2) implementation to be +// atomic. Notably, this is not the case when using NFS with multiple clients: +// https://stackoverflow.com/a/41396801 +package renameio diff --git a/utils/renameio/example_test.go b/utils/renameio/example_test.go new file mode 100644 index 0000000..1a0eaa8 --- /dev/null +++ b/utils/renameio/example_test.go @@ -0,0 +1,67 @@ +// Copyright 2018 Google Inc. +// +// 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 renameio_test + +import ( + "fmt" + "log" + + "github.com/safing/portbase/utils/renameio" +) + +func ExampleTempFile_justone() { + persist := func(temperature float64) error { + t, err := renameio.TempFile("", "/srv/www/metrics.txt") + if err != nil { + return err + } + defer t.Cleanup() + if _, err := fmt.Fprintf(t, "temperature_degc %f\n", temperature); err != nil { + return err + } + return t.CloseAtomicallyReplace() + } + // Thanks to the write package, a webserver exposing /srv/www never + // serves an incomplete or missing file. + if err := persist(31.2); err != nil { + log.Fatal(err) + } +} + +func ExampleTempFile_many() { + // Prepare for writing files to /srv/www, effectively caching calls to + // TempDir which TempFile would otherwise need to make. + dir := renameio.TempDir("/srv/www") + persist := func(temperature float64) error { + t, err := renameio.TempFile(dir, "/srv/www/metrics.txt") + if err != nil { + return err + } + defer t.Cleanup() + if _, err := fmt.Fprintf(t, "temperature_degc %f\n", temperature); err != nil { + return err + } + return t.CloseAtomicallyReplace() + } + + // Imagine this was an endless loop, reading temperature sensor values. + // Thanks to the write package, a webserver exposing /srv/www never + // serves an incomplete or missing file. + for { + if err := persist(31.2); err != nil { + log.Fatal(err) + } + } +} diff --git a/utils/renameio/symlink_test.go b/utils/renameio/symlink_test.go new file mode 100644 index 0000000..3046846 --- /dev/null +++ b/utils/renameio/symlink_test.go @@ -0,0 +1,52 @@ +// Copyright 2018 Google Inc. +// +// 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. + +// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris windows + +package renameio + +import ( + "bytes" + "io/ioutil" + "os" + "path/filepath" + "testing" +) + +func TestSymlink(t *testing.T) { + d, err := ioutil.TempDir("", "tempdirtest") + if err != nil { + t.Fatal(err) + } + defer os.RemoveAll(d) + + want := []byte("Hello World") + if err := ioutil.WriteFile(filepath.Join(d, "hello.txt"), want, 0644); err != nil { + t.Fatal(err) + } + + for i := 0; i < 2; i++ { + if err := Symlink("hello.txt", filepath.Join(d, "hi.txt")); err != nil { + t.Fatal(err) + } + + got, err := ioutil.ReadFile(filepath.Join(d, "hi.txt")) + if err != nil { + t.Fatal(err) + } + if !bytes.Equal(got, want) { + t.Fatalf("unexpected content: got %q, want %q", string(got), string(want)) + } + } +} diff --git a/utils/renameio/tempfile.go b/utils/renameio/tempfile.go new file mode 100644 index 0000000..9fe6f9b --- /dev/null +++ b/utils/renameio/tempfile.go @@ -0,0 +1,181 @@ +// Copyright 2018 Google Inc. +// +// 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 renameio + +import ( + "io/ioutil" + "os" + "path/filepath" +) + +// TempDir checks whether os.TempDir() can be used as a temporary directory for +// later atomically replacing files within dest. If no (os.TempDir() resides on +// a different mount point), dest is returned. +// +// Note that the returned value ceases to be valid once either os.TempDir() +// changes (e.g. on Linux, once the TMPDIR environment variable changes) or the +// file system is unmounted. +func TempDir(dest string) string { + return tempDir("", filepath.Join(dest, "renameio-TempDir")) +} + +func tempDir(dir, dest string) string { + if dir != "" { + return dir // caller-specified directory always wins + } + + // Chose the destination directory as temporary directory so that we + // definitely can rename the file, for which both temporary and destination + // file need to point to the same mount point. + fallback := filepath.Dir(dest) + + // The user might have overridden the os.TempDir() return value by setting + // the TMPDIR environment variable. + tmpdir := os.TempDir() + + testsrc, err := ioutil.TempFile(tmpdir, "."+filepath.Base(dest)) + if err != nil { + return fallback + } + cleanup := true + defer func() { + if cleanup { + os.Remove(testsrc.Name()) + } + }() + testsrc.Close() + + testdest, err := ioutil.TempFile(filepath.Dir(dest), "."+filepath.Base(dest)) + if err != nil { + return fallback + } + defer os.Remove(testdest.Name()) + testdest.Close() + + if err := os.Rename(testsrc.Name(), testdest.Name()); err != nil { + return fallback + } + cleanup = false // testsrc no longer exists + return tmpdir +} + +// PendingFile is a pending temporary file, waiting to replace the destination +// path in a call to CloseAtomicallyReplace. +type PendingFile struct { + *os.File + + path string + done bool + closed bool +} + +// Cleanup is a no-op if CloseAtomicallyReplace succeeded, and otherwise closes +// and removes the temporary file. +func (t *PendingFile) Cleanup() error { + if t.done { + return nil + } + // An error occurred. Close and remove the tempfile. Errors are returned for + // reporting, there is nothing the caller can recover here. + var closeErr error + if !t.closed { + closeErr = t.Close() + } + if err := os.Remove(t.Name()); err != nil { + return err + } + return closeErr +} + +// CloseAtomicallyReplace closes the temporary file and atomically replaces +// the destination file with it, i.e., a concurrent open(2) call will either +// open the file previously located at the destination path (if any), or the +// just written file, but the file will always be present. +func (t *PendingFile) CloseAtomicallyReplace() error { + // Even on an ordered file system (e.g. ext4 with data=ordered) or file + // systems with write barriers, we cannot skip the fsync(2) call as per + // Theodore Ts'o (ext2/3/4 lead developer): + // + // > data=ordered only guarantees the avoidance of stale data (e.g., the previous + // > contents of a data block showing up after a crash, where the previous data + // > could be someone's love letters, medical records, etc.). Without the fsync(2) + // > a zero-length file is a valid and possible outcome after the rename. + if err := t.Sync(); err != nil { + return err + } + t.closed = true + if err := t.Close(); err != nil { + return err + } + if err := os.Rename(t.Name(), t.path); err != nil { + return err + } + t.done = true + return nil +} + +// TempFile wraps ioutil.TempFile for the use case of atomically creating or +// replacing the destination file at path. +// +// If dir is the empty string, TempDir(filepath.Base(path)) is used. If you are +// going to write a large number of files to the same file system, store the +// result of TempDir(filepath.Base(path)) and pass it instead of the empty +// string. +// +// The file's permissions will be 0600 by default. You can change these by +// explicitly calling Chmod on the returned PendingFile. +func TempFile(dir, path string) (*PendingFile, error) { + f, err := ioutil.TempFile(tempDir(dir, path), "."+filepath.Base(path)) + if err != nil { + return nil, err + } + + return &PendingFile{File: f, path: path}, nil +} + +// Symlink wraps os.Symlink, replacing an existing symlink with the same name +// atomically (os.Symlink fails when newname already exists, at least on Linux). +func Symlink(oldname, newname string) error { + // Fast path: if newname does not exist yet, we can skip the whole dance + // below. + if err := os.Symlink(oldname, newname); err == nil || !os.IsExist(err) { + return err + } + + // We need to use ioutil.TempDir, as we cannot overwrite a ioutil.TempFile, + // and removing+symlinking creates a TOCTOU race. + d, err := ioutil.TempDir(filepath.Dir(newname), "."+filepath.Base(newname)) + if err != nil { + return err + } + cleanup := true + defer func() { + if cleanup { + os.RemoveAll(d) + } + }() + + symlink := filepath.Join(d, "tmp.symlink") + if err := os.Symlink(oldname, symlink); err != nil { + return err + } + + if err := os.Rename(symlink, newname); err != nil { + return err + } + + cleanup = false + return os.RemoveAll(d) +} diff --git a/utils/renameio/tempfile_linux_test.go b/utils/renameio/tempfile_linux_test.go new file mode 100644 index 0000000..3842fd8 --- /dev/null +++ b/utils/renameio/tempfile_linux_test.go @@ -0,0 +1,111 @@ +// Copyright 2018 Google Inc. +// +// 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. + +// +build linux + +package renameio + +import ( + "io/ioutil" + "os" + "path/filepath" + "syscall" + "testing" +) + +func TestTempDir(t *testing.T) { + if tmpdir, ok := os.LookupEnv("TMPDIR"); ok { + defer os.Setenv("TMPDIR", tmpdir) // restore + } else { + defer os.Unsetenv("TMPDIR") // restore + } + + mount1, err := ioutil.TempDir("", "tempdirtest") + if err != nil { + t.Fatal(err) + } + defer os.RemoveAll(mount1) + + mount2, err := ioutil.TempDir("", "tempdirtest") + if err != nil { + t.Fatal(err) + } + defer os.RemoveAll(mount2) + + if err := syscall.Mount("tmpfs", mount1, "tmpfs", 0, ""); err != nil { + t.Skipf("cannot mount tmpfs on %s: %v", mount1, err) + } + defer syscall.Unmount(mount1, 0) + + if err := syscall.Mount("tmpfs", mount2, "tmpfs", 0, ""); err != nil { + t.Skipf("cannot mount tmpfs on %s: %v", mount2, err) + } + defer syscall.Unmount(mount2, 0) + + tests := []struct { + name string + dir string + path string + TMPDIR string + want string + }{ + { + name: "implicit TMPDIR", + path: filepath.Join(os.TempDir(), "foo.txt"), + want: os.TempDir(), + }, + + { + name: "explicit TMPDIR", + path: filepath.Join(mount1, "foo.txt"), + TMPDIR: mount1, + want: mount1, + }, + + { + name: "explicit unsuitable TMPDIR", + path: filepath.Join(mount1, "foo.txt"), + TMPDIR: mount2, + want: mount1, + }, + + { + name: "nonexistant TMPDIR", + path: filepath.Join(mount1, "foo.txt"), + TMPDIR: "/nonexistant", + want: mount1, + }, + + { + name: "caller-specified", + dir: "/overridden", + path: filepath.Join(mount1, "foo.txt"), + TMPDIR: "/nonexistant", + want: "/overridden", + }, + } + + for _, tt := range tests { + t.Run(tt.name, func(t *testing.T) { + if tt.TMPDIR == "" { + os.Unsetenv("TMPDIR") + } else { + os.Setenv("TMPDIR", tt.TMPDIR) + } + if got := tempDir(tt.dir, tt.path); got != tt.want { + t.Fatalf("tempDir(%q, %q): got %q, want %q", tt.dir, tt.path, got, tt.want) + } + }) + } +} diff --git a/utils/renameio/writefile.go b/utils/renameio/writefile.go new file mode 100644 index 0000000..187d2d4 --- /dev/null +++ b/utils/renameio/writefile.go @@ -0,0 +1,38 @@ +// Copyright 2018 Google Inc. +// +// 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 renameio + +import "os" + +// WriteFile mirrors ioutil.WriteFile, replacing an existing file with the same +// name atomically. +func WriteFile(filename string, data []byte, perm os.FileMode) error { + t, err := TempFile("", filename) + if err != nil { + return err + } + defer t.Cleanup() + + // Set permissions before writing data, in case the data is sensitive. + if err := t.Chmod(perm); err != nil { + return err + } + + if _, err := t.Write(data); err != nil { + return err + } + + return t.CloseAtomicallyReplace() +} diff --git a/utils/renameio/writefile_test.go b/utils/renameio/writefile_test.go new file mode 100644 index 0000000..8cdafef --- /dev/null +++ b/utils/renameio/writefile_test.go @@ -0,0 +1,57 @@ +// Copyright 2018 Google Inc. +// +// 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. + +// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris windows + +package renameio + +import ( + "bytes" + "io/ioutil" + "os" + "path/filepath" + "testing" +) + +func TestWriteFile(t *testing.T) { + d, err := ioutil.TempDir("", "tempdirtest") + if err != nil { + t.Fatal(err) + } + defer os.RemoveAll(d) + + filename := filepath.Join(d, "hello.sh") + + wantData := []byte("#!/bin/sh\necho \"Hello World\"\n") + wantPerm := os.FileMode(0755) + if err := WriteFile(filename, wantData, wantPerm); err != nil { + t.Fatal(err) + } + + gotData, err := ioutil.ReadFile(filename) + if err != nil { + t.Fatal(err) + } + if !bytes.Equal(gotData, wantData) { + t.Errorf("got data %v, want data %v", gotData, wantData) + } + + fi, err := os.Stat(filename) + if err != nil { + t.Fatal(err) + } + if gotPerm := fi.Mode() & os.ModePerm; gotPerm != wantPerm { + t.Errorf("got permissions 0%o, want permissions 0%o", gotPerm, wantPerm) + } +}