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matchVar.go
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matchVar.go
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// shellexpand is a replacement for Golang's `os.Expand()` that supports
// UNIX shell string expansion and substituation
//
// Copyright 2019-present Ganbaro Digital Ltd
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//
// * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in
// the documentation and/or other materials provided with the
// distribution.
//
// * Neither the names of the copyright holders nor the names of his
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
// ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
package shellexpand
import "unicode/utf8"
func matchVar(input string) (int, bool) {
// have we started on a dollar?
if input[0] != '$' {
return 0, false
}
// no, it is not
//
// special case: positional parameters are not subject to normal
// matching rules (sigh)
if isNumericChar(rune(input[1])) {
return 2, true
}
// general case - a non-positional parameter that may be wrapped
// in braces
braceDepth := 0
inEscape := false
w := 0
var c rune
for i := 0; i < len(input); i += w {
// what are we looking at?
c, w = utf8.DecodeRuneInString(input[i:])
// are we dealing with an escaped char?
if inEscape {
inEscape = false
} else if c == '\\' && !inEscape {
// skip escaped chars
inEscape = true
} else if c == '{' {
braceDepth++
} else if c == '}' {
braceDepth--
if braceDepth == 0 {
return i + w, true
}
} else if c == ' ' {
if braceDepth == 0 {
// we must be looking at a var that was not surrounded
// by braces
return i, true
}
// no spaces allowed inside a var name
// return 0, false
}
}
// end of the string
if braceDepth == 0 {
return len(input), true
}
// we did not find a matching closing brace
return 0, false
}