diff options
Diffstat (limited to 'src/pkg/strings/strings.go')
| -rw-r--r-- | src/pkg/strings/strings.go | 29 |
1 files changed, 16 insertions, 13 deletions
diff --git a/src/pkg/strings/strings.go b/src/pkg/strings/strings.go index 7be98e6c1..4e375b4d5 100644 --- a/src/pkg/strings/strings.go +++ b/src/pkg/strings/strings.go @@ -178,7 +178,8 @@ func HasSuffix(s, suffix string) bool { } // Map returns a copy of the string s with all its characters modified -// according to the mapping function. +// according to the mapping function. If mapping returns a negative value, the character is +// dropped from the string with no replacement. func Map(mapping func(rune int) int, s string) string { // In the worst case, the string can grow when mapped, making // things unpleasant. But it's so rare we barge in assuming it's @@ -188,20 +189,22 @@ func Map(mapping func(rune int) int, s string) string { b := make([]byte, maxbytes); for _, c := range s { rune := mapping(c); - wid := 1; - if rune >= utf8.RuneSelf { - wid = utf8.RuneLen(rune) - } - if nbytes+wid > maxbytes { - // Grow the buffer. - maxbytes = maxbytes*2 + utf8.UTFMax; - nb := make([]byte, maxbytes); - for i, c := range b[0:nbytes] { - nb[i] = c + if rune >= 0 { + wid := 1; + if rune >= utf8.RuneSelf { + wid = utf8.RuneLen(rune) + } + if nbytes+wid > maxbytes { + // Grow the buffer. + maxbytes = maxbytes*2 + utf8.UTFMax; + nb := make([]byte, maxbytes); + for i, c := range b[0:nbytes] { + nb[i] = c + } + b = nb; } - b = nb; + nbytes += utf8.EncodeRune(rune, b[nbytes:maxbytes]); } - nbytes += utf8.EncodeRune(rune, b[nbytes:maxbytes]); } return string(b[0:nbytes]); } |