The highest tagged major version is
README
¶
X
A collection of functions to write concise code.
sha2 := sha256.New()
src := tar.NewReader(
CloseAfterRead(C2(gzip.NewReader(
io.TeeReader(
CloseAfterRead(C2(http.Get("https://go.dev/dl/go1.20.2.linux-amd64.tar.gz")).Body),
sha2,
),
))),
)
for th, err := src.Next(); err != io.EOF; th, err = src.Next() {
C(err)
switch th.Typeflag {
case tar.TypeDir:
C(os.Mkdir(th.Name, 0o755))
case tar.TypeReg:
dst := C2(os.OpenFile(th.Name, os.O_CREATE|os.O_WRONLY, th.FileInfo().Mode()))
C2(io.Copy(dst, src))
C(dst.Close())
}
}
Assert(hex.EncodeToString(sha2.Sum(nil)) == "4eaea32f59cde4dc635fbc42161031d13e1c780b87097f4b4234cfce671f1768")
This snippet downloads an archive, unpacks it and verifies its checksum, all in one go. Any error causes a panic, cascading errors are stacked and each reader is closed as expected.
If you get a warning from gopls/staticcheck about dot-import, create a file named staticcheck.conf in your project directory (or parents) with:
dot_import_whitelist = [ "github.com/xpetit/x/v3" ]
Documentation
¶
Index ¶
- func AppendByte[T Number](dst []byte, i T) []byte
- func AppendUnicodeBar(b []byte, width int) []byte
- func Assert(cond bool, a ...any)
- func BarChart[M ~map[K]V, K cmp.Ordered, V Integer](w io.Writer, m M, maxItems int)
- func C(err error)
- func C2[T any](a T, err error) T
- func C3[T1, T2 any](a T1, b T2, err error) (T1, T2)
- func Clamp[T Number](val, min, max T) T
- func CloseAfterRead(r io.ReadCloser) io.Reader
- func Closing(v io.Closer)
- func FormatByte[T Number](i T) string
- func Goroutines(nb int, fn func()) (wait func())
- func HasKey[M ~map[K]V, K comparable, V any](m M, k K) bool
- func InitUnicodeCategory()
- func Intn[T Integer](n T) T
- func Keys[M ~map[K]V, K comparable, V any](m M) []K
- func MultiLines(s string) string
- func Output(c *exec.Cmd) ([]byte, error)
- func Ptr[T any](v T) *T
- func Run(c *exec.Cmd) error
- func Shuffle[S ~[]E, E any](s S)
- func StdinIsPipe() bool
- func StdoutIsTerminal() bool
- func UnicodeBar(width int) string
- func UnicodeCategory(r rune) (name string)
- type Float
- type Integer
- type Number
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func AppendByte ¶
AppendByte appends the string form of the byte count i, as generated by FormatByte, to dst and returns the extended buffer.
func AppendUnicodeBar ¶
func BarChart ¶
BarChart prints a bar chart with unicode block elements to help visualize m in a compact way. If maxItems > -1, it limits the amount of lines to display. Example with the number of online players for 8 games (data from steamcharts):
100% 2405676 Total (8 entries) 50% 1195540 Counter-Strike: Global Offensive [██████ ] 20% 473708 Dota 2 [██▍ ] 11% 275232 Apex Legends [█▍ ] 10% 246234 PUBG: BATTLEGROUNDS [█▎ ] 5% 123765 Grand Theft Auto V [▋ ] 3% 64405 Team Fortress 2 [▍ ] 1% 21228 The Sims™ 4 [▏ ] 0% 5564 Sekiro™: Shadows Die Twice [ ]
func C ¶
func C(err error)
C panics if its argument is a non-nil error. Examples:
C(os.Chdir("directory"))
C(json.NewDecoder(os.Stdin).Decode(&data))
func C2 ¶
C2 panics if its second argument is a non-nil error and returns the first one. Examples:
i := C2(strconv.Atoi("123"))
f := C2(os.Open("file"))
func C3 ¶
C3 panics if its third argument is a non-nil error and returns the first two. Examples:
img, _ := C3(image.Decode(f)) _, port := C3(net.SplitHostPort(address))
func CloseAfterRead ¶
func CloseAfterRead(r io.ReadCloser) io.Reader
CloseAfterRead returns a Reader that automatically closes when there is no more data to read or an error has occurred. Examples:
// Prints SHA2 of "file_to_hash" in hexadecimal notation
h := sha256.New()
C2(io.Copy(h, CloseAfterRead(C2(os.Open("file_to_hash")))))
fmt.Println(hex.EncodeToString(h.Sum(nil)))
// Downloads a file
const url = "https://go.dev/dl/go1.20.2.linux-amd64.tar.gz"
dst := C2(os.Create(path.Base(url)))
defer Closing(dst)
C2(io.Copy(dst, CloseAfterRead(C2(http.Get(url)).Body)))
func Closing ¶
Closing is a shortcut, instead of writing:
defer func() { C(f.Close()) }()
One can write:
defer Closing(f)
func FormatByte ¶
func Goroutines ¶
func Goroutines(nb int, fn func()) (wait func())
Goroutines spawns nb goroutines executing fn. It returns a function that waits for them to finish.
func HasKey ¶
func HasKey[M ~map[K]V, K comparable, V any](m M, k K) bool
HasKey returns whether k is present in the map m.
func InitUnicodeCategory ¶
func InitUnicodeCategory()
InitUnicodeCategory inits the cache for UnicodeCategory It is exported so that the user can trigger cache building instead of waiting for the first call to UnicodeCategory
func Intn ¶
func Intn[T Integer](n T) T
Intn returns a uniform random value in [0, n). It panics if n <= 0 or n > math.MaxInt64.
func Keys ¶
func Keys[M ~map[K]V, K comparable, V any](m M) []K
Keys returns the keys of the map m. The keys will be in an indeterminate order.
func MultiLines ¶
MultiLines formats a multiline raw string, changing:
` First line Second line Third line `
to:
`First line Second line Third line`
It is intended to be called like this:
MultiLines(` First Line Second line Third line `)
func Output ¶
Output is similar to (*exec.Cmd).Output() but conveniently wraps exec.ExitError with stderr:
_, err1 := exec.Command("ls", "").Output() // standard way
_, err2 := Output(exec.Command("ls", "")) // with this function
err1.Error() == "exit status 2"
err2.Error() == "exit status 2: ls: cannot access '': No such file or directory"
The underlying *exec.ExitError remains recoverable:
if err := new(exec.ExitError); errors.As(err2, &err) {
fmt.Println(err.UserTime())
}
func Run ¶
Run is similar to (*exec.Cmd).Run() but conveniently wraps exec.ExitError with stderr:
err1 := exec.Command("go", "run").Run() // standard way
err2 := Run(exec.Command("go", "run")) // with this function
err1.Error() == "exit status 1"
err2.Error() == "exit status 1: go: no go files listed"
The underlying *exec.ExitError remains recoverable:
if err := new(exec.ExitError); errors.As(err2, &err) {
fmt.Println(err.UserTime())
}
func StdinIsPipe ¶
func StdinIsPipe() bool
func StdoutIsTerminal ¶
func StdoutIsTerminal() bool
func UnicodeBar ¶
func UnicodeCategory ¶
UnicodeCategory returns the code point General Category. It is a two bytes string with major & minor e.g. "Lu", "Zs", "Nd"...
Source Files