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core.go
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core.go
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// Copyright © 2021-2023 The Gomon Project.
package gocore
import (
"bufio"
"bytes"
"context"
"encoding/binary"
"fmt"
"os"
"os/exec"
"path/filepath"
"strconv"
"unsafe"
)
type (
// ValidValue defines list of values that are valid for a type safe string.
ValidValue[T ~string] map[T]int
)
const (
// RFC3339Milli used for formatting timestamps.
RFC3339Milli = "2006-01-02T15:04:05.000Z07:00"
)
var (
// HostEndian enables byte order conversion between local and network integers.
HostEndian = func() binary.ByteOrder {
n := uint16(1)
a := (*[2]byte)(unsafe.Pointer(&n))[:]
b := []byte{0, 1}
if bytes.Equal(a, b) {
return binary.BigEndian
}
return binary.LittleEndian
}()
)
// Define initializes a ValidValue type with its valid values.
func (vv ValidValue[T]) Define(values ...T) ValidValue[T] {
vv = map[T]int{}
for i, v := range values {
vv[v] = i
}
return vv
}
// ValidValues returns an ordered list of valid values for the type.
func (vv ValidValue[T]) ValidValues() []string {
ss := make([]string, len(vv))
for v, i := range vv {
ss[i] = string(v)
}
return ss
}
// IsValid returns whether a value is valid.
func (vv ValidValue[T]) IsValid(v T) bool {
_, ok := vv[v]
return ok
}
// Index returns the position of a value in the valid value list.
func (vv ValidValue[T]) Index(v T) int {
return vv[v]
}
// ChDir is a convenience function for changing the current directory and reporting its canonical path.
// If changing the directory fails, ChDir returns the error and canonical path of the current directory.
func ChDir(dir string) (string, error) {
var err error
if dir, err = filepath.Abs(dir); err == nil {
if dir, err = filepath.EvalSymlinks(dir); err == nil {
if err = os.Chdir(dir); err == nil {
return dir, nil
}
}
}
dir, _ = os.Getwd()
dir, _ = filepath.EvalSymlinks(dir)
return dir, err
}
// Subdir acts like filepath.Rel() but returns an error if the target path is not on the base path.
func Subdir(base, targ string) (string, error) {
if rel, err := filepath.Rel(base, targ); err != nil {
return "", err
} else if len(rel) > 1 && rel[:2] == ".." {
return "", fmt.Errorf("target path %s is not on base path %s", targ, base)
} else {
return rel, nil
}
}
// IsTerminal reports if a file handle is connected to the terminal.
func IsTerminal(f *os.File) bool {
info, err := f.Stat()
if err != nil {
return false
}
terminal := os.ModeDevice | os.ModeCharDevice
return info.Mode()&terminal == terminal
}
// Spawn starts a command and returns a scanner for reading stdout.
func Spawn(ctx context.Context, cmdline []string) (*bufio.Scanner, error) {
cmd := exec.CommandContext(ctx, cmdline[0], cmdline[1:]...)
cmd.ExtraFiles = extraFiles()
stdout, err := cmd.StdoutPipe()
if err != nil {
return nil, Error("StdoutPipe", err, map[string]string{
"command": cmd.String(),
})
}
if err := cmd.Start(); err != nil {
return nil, Error("Start", err, map[string]string{
"command": cmd.String(),
})
}
Error("spawn", nil, map[string]string{
"command": cmd.String(),
"pid": strconv.Itoa(cmd.Process.Pid),
}).Info()
go wait(cmd)
return bufio.NewScanner(stdout), nil
}
// wait for a started command to complete and report its exit status.
func wait(cmd *exec.Cmd) {
err := cmd.Wait()
state := cmd.ProcessState
var stderr string
if err != nil {
if err, ok := err.(*exec.ExitError); ok {
stderr = string(err.Stderr)
}
}
Error("wait", err, map[string]string{
"command": cmd.Args[0],
"pid": strconv.Itoa(cmd.Process.Pid),
"rc": strconv.Itoa(state.ExitCode()),
"systime": state.SystemTime().String(),
"usertime": state.UserTime().String(),
"stderr": stderr,
}).Info()
}