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x/text/width: lose one character #14817

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naduma opened this issue Mar 14, 2016 · 3 comments
Closed

x/text/width: lose one character #14817

naduma opened this issue Mar 14, 2016 · 3 comments
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@naduma
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naduma commented Mar 14, 2016

When Fold.String/Narrow.String was called, it was lost one character.

want := "A" + strings.Repeat("0", 127) + "B"
got := width.Fold.String("\uff21" + strings.Repeat("0", 127) + "B")
=> got != want, "B" is lost.

conditions:

  • long string (more than 128 [initialBufSize])
  • contains wide character

initialBufSize from https://github.com/golang/text/blob/master/transform/transform.go#L506

cause:

https://github.com/golang/text/blob/master/width/transform.go#L25

Even when the length of "dst" is 0, "nSrc" increases one.

InitStmt(nSrc++) is necessary?
@bradfitz
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Please post a complete and minimal program demonstrating the problem, not just a snippet. Is the \uff21 necessary for the repro? Ideally please provide a share link from https://play.golang.org/ where it reproduces online.

InitStmt(nSrc++) is not valid Go. ++ is not an expression in Go.

@naduma
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naduma commented Mar 15, 2016 

$ go version
go version go1.6 linux/amd64

Steps to Reproduce

$ go get "golang.org/x/text"

$ go run sample.go

sample.go

package main

import (
    "fmt"
    "strings"

    "golang.org/x/text/width"
)

func main() {
    want := "A" + strings.Repeat("0", 127) + "B"
    got := width.Fold.String("\uff21" + strings.Repeat("0", 127) + "B")
    if got != want {
        fmt.Println("Fold.String NG!")
        fmt.Printf("got  %s (%d)\n", got, len(got))
        fmt.Printf("want %s (%d)\n", want, len(want))
    } else {
        fmt.Println("Fold.String OK!")
    }

    want = "A" + strings.Repeat("0", 127) + "B"
    got = width.Narrow.String("\uff21" + strings.Repeat("0", 127) + "B")
    if got != want {
        fmt.Println("Narrow.String NG!")
        fmt.Printf("got  %s (%d)\n", got, len(got))
        fmt.Printf("want %s (%d)\n", want, len(want))
    } else {
        fmt.Println("Narrow.String OK!")
    }
}

InitStmt(nSrc++) is not valid Go. ++ is not an expression in Go.

InitStm is ForClause's InitStmt. ex. for i:=0; i < 10; i++ {

I'm not good at English. I wrote a patch sample, please check it.

https://gist.github.com/naduma/90a8fa3e21fffa1bbf80

@bradfitz bradfitz changed the title text/width: lose one character x/text/width: lose one character Apr 3, 2016
@bradfitz bradfitz added this to the Unreleased milestone Apr 3, 2016
@gopherbot
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CL https://golang.org/cl/21500 mentions this issue.

@golang golang locked and limited conversation to collaborators Apr 8, 2017
@rsc rsc unassigned mpvl Jun 23, 2022
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