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Diffstat (limited to 'libgo/go/cmd/go/internal/str/str.go')
-rw-r--r-- | libgo/go/cmd/go/internal/str/str.go | 141 |
1 files changed, 141 insertions, 0 deletions
diff --git a/libgo/go/cmd/go/internal/str/str.go b/libgo/go/cmd/go/internal/str/str.go new file mode 100644 index 00000000000..0413ed8e69e --- /dev/null +++ b/libgo/go/cmd/go/internal/str/str.go @@ -0,0 +1,141 @@ +// Copyright 2017 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Package str provides string manipulation utilities. +package str + +import ( + "bytes" + "fmt" + "unicode" + "unicode/utf8" +) + +// StringList flattens its arguments into a single []string. +// Each argument in args must have type string or []string. +func StringList(args ...interface{}) []string { + var x []string + for _, arg := range args { + switch arg := arg.(type) { + case []string: + x = append(x, arg...) + case string: + x = append(x, arg) + default: + panic("stringList: invalid argument of type " + fmt.Sprintf("%T", arg)) + } + } + return x +} + +// ToFold returns a string with the property that +// strings.EqualFold(s, t) iff ToFold(s) == ToFold(t) +// This lets us test a large set of strings for fold-equivalent +// duplicates without making a quadratic number of calls +// to EqualFold. Note that strings.ToUpper and strings.ToLower +// do not have the desired property in some corner cases. +func ToFold(s string) string { + // Fast path: all ASCII, no upper case. + // Most paths look like this already. + for i := 0; i < len(s); i++ { + c := s[i] + if c >= utf8.RuneSelf || 'A' <= c && c <= 'Z' { + goto Slow + } + } + return s + +Slow: + var buf bytes.Buffer + for _, r := range s { + // SimpleFold(x) cycles to the next equivalent rune > x + // or wraps around to smaller values. Iterate until it wraps, + // and we've found the minimum value. + for { + r0 := r + r = unicode.SimpleFold(r0) + if r <= r0 { + break + } + } + // Exception to allow fast path above: A-Z => a-z + if 'A' <= r && r <= 'Z' { + r += 'a' - 'A' + } + buf.WriteRune(r) + } + return buf.String() +} + +// FoldDup reports a pair of strings from the list that are +// equal according to strings.EqualFold. +// It returns "", "" if there are no such strings. +func FoldDup(list []string) (string, string) { + clash := map[string]string{} + for _, s := range list { + fold := ToFold(s) + if t := clash[fold]; t != "" { + if s > t { + s, t = t, s + } + return s, t + } + clash[fold] = s + } + return "", "" +} + +// Contains reports whether x contains s. +func Contains(x []string, s string) bool { + for _, t := range x { + if t == s { + return true + } + } + return false +} + +func isSpaceByte(c byte) bool { + return c == ' ' || c == '\t' || c == '\n' || c == '\r' +} + +// SplitQuotedFields splits s into a list of fields, +// allowing single or double quotes around elements. +// There is no unescaping or other processing within +// quoted fields. +func SplitQuotedFields(s string) ([]string, error) { + // Split fields allowing '' or "" around elements. + // Quotes further inside the string do not count. + var f []string + for len(s) > 0 { + for len(s) > 0 && isSpaceByte(s[0]) { + s = s[1:] + } + if len(s) == 0 { + break + } + // Accepted quoted string. No unescaping inside. + if s[0] == '"' || s[0] == '\'' { + quote := s[0] + s = s[1:] + i := 0 + for i < len(s) && s[i] != quote { + i++ + } + if i >= len(s) { + return nil, fmt.Errorf("unterminated %c string", quote) + } + f = append(f, s[:i]) + s = s[i+1:] + continue + } + i := 0 + for i < len(s) && !isSpaceByte(s[i]) { + i++ + } + f = append(f, s[:i]) + s = s[i:] + } + return f, nil +} |