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Copy pathbase.go
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362 lines (319 loc) · 9.93 KB
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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Code borrowed from https://github.com/golang/go/blob/master/src/cmd/gofmt/gofmt.go
// PLEASE DO NOT EDIT.
package main
import (
"context"
"fmt"
"go/scanner"
"io"
"io/fs"
"math/rand"
"os"
"path/filepath"
"strconv"
"golang.org/x/sync/semaphore"
)
// fdSem guards the number of concurrently-open file descriptors.
//
// For now, this is arbitrarily set to 200, based on the observation that many
// platforms default to a kernel limit of 256. Ideally, perhaps we should derive
// it from rlimit on platforms that support that system call.
//
// File descriptors opened from outside of this package are not tracked,
// so this limit may be approximate.
var fdSem = make(chan bool, 200)
// A sequencer performs concurrent tasks that may write output, but emits that
// output in a deterministic order.
type sequencer struct {
maxWeight int64
sem *semaphore.Weighted // weighted by input bytes (an approximate proxy for memory overhead)
prev <-chan *reporterState // 1-buffered
}
// newSequencer returns a sequencer that allows concurrent tasks up to maxWeight
// and writes tasks' output to out and err.
func newSequencer(maxWeight int64, out, err io.Writer) *sequencer {
sem := semaphore.NewWeighted(maxWeight)
prev := make(chan *reporterState, 1)
prev <- &reporterState{out: out, err: err}
return &sequencer{
maxWeight: maxWeight,
sem: sem,
prev: prev,
}
}
// exclusive is a weight that can be passed to a sequencer to cause
// a task to be executed without any other concurrent tasks.
const exclusive = -1
// Add blocks until the sequencer has enough weight to spare, then adds f as a
// task to be executed concurrently.
//
// If the weight is either negative or larger than the sequencer's maximum
// weight, Add blocks until all other tasks have completed, then the task
// executes exclusively (blocking all other calls to Add until it completes).
//
// f may run concurrently in a goroutine, but its output to the passed-in
// reporter will be sequential relative to the other tasks in the sequencer.
//
// If f invokes a method on the reporter, execution of that method may block
// until the previous task has finished. (To maximize concurrency, f should
// avoid invoking the reporter until it has finished any parallelizable work.)
//
// If f returns a non-nil error, that error will be reported after f's output
// (if any) and will cause a nonzero final exit code.
func (s *sequencer) Add(weight int64, f func(*reporter) error) {
if weight < 0 || weight > s.maxWeight {
weight = s.maxWeight
}
if err := s.sem.Acquire(context.TODO(), weight); err != nil {
// Change the task from "execute f" to "report err".
weight = 0
f = func(*reporter) error { return err }
}
r := &reporter{prev: s.prev}
next := make(chan *reporterState, 1)
s.prev = next
// Start f in parallel: it can run until it invokes a method on r, at which
// point it will block until the previous task releases the output state.
go func() {
if err := f(r); err != nil {
r.Report(err)
}
next <- r.getState() // Release the next task.
s.sem.Release(weight)
}()
}
// AddReport prints an error to s after the output of any previously-added
// tasks, causing the final exit code to be nonzero.
func (s *sequencer) AddReport(err error) {
s.Add(0, func(*reporter) error { return err })
}
// GetExitCode waits for all previously-added tasks to complete, then returns an
// exit code for the sequence suitable for passing to os.Exit.
func (s *sequencer) GetExitCode() int {
c := make(chan int, 1)
s.Add(0, func(r *reporter) error {
c <- r.ExitCode()
return nil
})
return <-c
}
// A reporter reports output, warnings, and errors.
type reporter struct {
prev <-chan *reporterState
state *reporterState
}
// reporterState carries the state of a reporter instance.
//
// Only one reporter at a time may have access to a reporterState.
type reporterState struct {
out, err io.Writer
exitCode int
}
// getState blocks until any prior reporters are finished with the reporter
// state, then returns the state for manipulation.
func (r *reporter) getState() *reporterState {
if r.state == nil {
r.state = <-r.prev
}
return r.state
}
// Warnf emits a warning message to the reporter's error stream,
// without changing its exit code.
func (r *reporter) Warnf(format string, args ...any) {
fmt.Fprintf(r.getState().err, format, args...)
}
// Write emits a slice to the reporter's output stream.
//
// Any error is returned to the caller, and does not otherwise affect the
// reporter's exit code.
func (r *reporter) Write(p []byte) (int, error) {
return r.getState().out.Write(p)
}
// Report emits a non-nil error to the reporter's error stream,
// changing its exit code to a nonzero value.
func (r *reporter) Report(err error) {
if err == nil {
panic("Report with nil error")
}
st := r.getState()
scanner.PrintError(st.err, err)
st.exitCode = 2
}
func (r *reporter) ExitCode() int {
return r.getState().exitCode
}
// readFile reads the contents of filename, described by info.
// If in is non-nil, readFile reads directly from it.
// Otherwise, readFile opens and reads the file itself,
// with the number of concurrently-open files limited by fdSem.
func readFile(filename string, info fs.FileInfo, in io.Reader) ([]byte, error) {
if in == nil {
fdSem <- true
var err error
f, err := os.Open(filename)
if err != nil {
return nil, err
}
in = f
defer func() {
f.Close()
<-fdSem
}()
}
// Compute the file's size and read its contents with minimal allocations.
//
// If we have the FileInfo from filepath.WalkDir, use it to make
// a buffer of the right size and avoid ReadAll's reallocations.
//
// If the size is unknown (or bogus, or overflows an int), fall back to
// a size-independent ReadAll.
size := -1
if info != nil && info.Mode().IsRegular() && int64(int(info.Size())) == info.Size() {
size = int(info.Size())
}
if size+1 <= 0 {
// The file is not known to be regular, so we don't have a reliable size for it.
var err error
src, err := io.ReadAll(in)
if err != nil {
return nil, err
}
return src, nil
}
// We try to read size+1 bytes so that we can detect modifications: if we
// read more than size bytes, then the file was modified concurrently.
// (If that happ
8000
ens, we could, say, append to src to finish the read, or
// proceed with a truncated buffer — but the fact that it changed at all
// indicates a possible race with someone editing the file, so we prefer to
// stop to avoid corrupting it.)
src := make([]byte, size+1)
n, err := io.ReadFull(in, src)
switch err {
case nil, io.EOF, io.ErrUnexpectedEOF:
// io.ReadFull returns io.EOF (for an empty file) or io.ErrUnexpectedEOF
// (for a non-empty file) if the file was changed unexpectedly. Continue
// with comparing file sizes in those cases.
default:
return nil, err
}
if n < size {
return nil, fmt.Errorf("error: size of %s changed during reading (from %d to %d bytes)", filename, size, n)
} else if n > size {
return nil, fmt.Errorf("error: size of %s changed during reading (from %d to >=%d bytes)", filename, size, len(src))
}
return src[:n], nil
}
func fileWeight(path string, info fs.FileInfo) int64 {
if info == nil {
return exclusive
}
if info.Mode().Type() == fs.ModeSymlink {
var err error
info, err = os.Stat(path)
if err != nil {
return exclusive
}
}
if !info.Mode().IsRegular() {
// For non-regular files, FileInfo.Size is system-dependent and thus not a
// reliable indicator of weight.
return exclusive
}
return info.Size()
}
// writeFile updates a file with the new formatted data.
func writeFile(filename string, orig, formatted []byte, perm fs.FileMode, size int64) error {
// Make a temporary backup file before rewriting the original file.
bakname, err := backupFile(filename, orig, perm)
if err != nil {
return err
}
fdSem <- true
defer func() { <-fdSem }()
fout, err := os.OpenFile(filename, os.O_WRONLY, perm)
if err != nil {
// We couldn't even open the file, so it should
// not have changed.
os.Remove(bakname)
return err
}
defer fout.Close() // for error paths
restoreFail := func(err error) {
fmt.Fprintf(os.Stderr, "gofmt: %s: error restoring file to original: %v; backup in %s\n", filename, err, bakname)
}
n, err := fout.Write(formatted)
if err == nil && int64(n) < size {
err = fout.Truncate(int64(n))
}
if err != nil {
// Rewriting the file failed.
if n == 0 {
// Original file unchanged.
os.Remove(bakname)
return err
}
// Try to restore the original contents.
no, erro := fout.WriteAt(orig, 0)
if erro != nil {
// That failed too.
restoreFail(erro)
return err
}
if no < n {
// Original file is shorter. Truncate.
if erro = fout.Truncate(int64(no)); erro != nil {
restoreFail(erro)
return err
}
}
if erro := fout.Close(); erro != nil {
restoreFail(erro)
return err
}
// Original contents restored.
os.Remove(bakname)
return err
}
if err := fout.Close(); err != nil {
restoreFail(err)
return err
}
// File updated.
os.Remove(bakname)
return nil
}
// backupFile writes data to a new file named filename<number> with permissions perm,
// with <number> randomly chosen such that the file name is unique. backupFile returns
// the chosen file name.
func backupFile(filename string, data []byte, perm fs.FileMode) (string, error) {
fdSem <- true
defer func() { <-fdSem }()
nextRandom := func() string {
return strconv.Itoa(rand.Int())
}
dir, base := filepath.Split(filename)
var (
bakname string
f *os.File
)
for {
bakname = filepath.Join(dir, base+"."+nextRandom())
var err error
f, err = os.OpenFile(bakname, os.O_RDWR|os.O_CREATE|os.O_EXCL, perm)
if err == nil {
break
}
if !os.IsExist(err) {
return "", err
}
}
// write data to backup file
_, err := f.Write(data)
if err1 := f.Close(); err == nil {
err = err1
}
return bakname, err
}