108 lines
2.3 KiB
Go
108 lines
2.3 KiB
Go
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package clifmt
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import (
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"fmt"
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"reflect"
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"strings"
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)
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var ErrNoNewline = fmt.Errorf("no newline allowed in progress mode")
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// Printpf prints a progress (dynamic) line that rewrites itself
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// on arguments' update
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func Printpf(format string, args ...interface{}) error {
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// 1. check format
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if strings.ContainsAny(format, "\n\r") {
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return ErrNoNewline
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}
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// 2. init
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fixed := make([]interface{}, len(args), len(args)) // actual values
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update := make([]chan interface{}, 0, len(args)) // channels that update values
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updateIndex := make([]int, 0, len(args)) // association [order -> index in @fixed]
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// 3. manage fixed values vs. updatable values (channels)
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for i, arg := range args {
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// channel -> keep Zero value + store channel
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if reflect.TypeOf(arg).Kind() == reflect.Chan {
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updateIndex = append(updateIndex, i)
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update = append(update, arg.(chan interface{}))
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continue
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}
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// raw -> set value
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fixed[i] = arg
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}
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// 4. launch dynamic select for each channel
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maxlen := 0
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nselect(update, func(i int, value interface{}, ok bool) {
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// channel is closed -> do nothing
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if !ok {
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return
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}
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// extract real index
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index := updateIndex[i]
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// update value
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fixed[index] = value
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// ignore on errors (updatable values still NIL)
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str, err := Sprintf(format, fixed...)
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if err != nil {
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return
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}
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reallen := displaySize(str)
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// print string
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fmt.Printf("\r%s", str)
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// pad right to end of max size
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if reallen < maxlen {
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pad := make([]byte, 0, maxlen-reallen)
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for i := reallen; i < maxlen; i++ {
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pad = append(pad, ' ')
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}
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fmt.Printf("%s", pad)
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} else {
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maxlen = reallen
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}
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})
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fmt.Printf("\n")
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return nil
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}
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// nselect selects on N channels
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func nselect(channels []chan interface{}, handler func(int, interface{}, bool)) {
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// 1. build the case list containing each channel
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cases := make([]reflect.SelectCase, len(channels))
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for i, ch := range channels {
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cases[i] = reflect.SelectCase{Dir: reflect.SelectRecv, Chan: reflect.ValueOf(ch)}
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}
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// 2. wait for selections
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remaining := len(cases)
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for remaining > 0 {
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index, value, ok := reflect.Select(cases)
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// (1) Closed
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if !ok {
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cases[index].Chan = reflect.ValueOf(nil)
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remaining--
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continue
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}
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// (2) Received data
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handler(index, value, ok)
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}
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}
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