Example antlr.CharStream that changes the case of the input.

CaseChangingStream.go

/*
Copyright 2017 Google Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

https://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

// CaseChangingStream wraps an existing CharStream, but upper cases, or
// lower cases the input before it is tokenized.
type CaseChangingStream struct {
	antlr.CharStream

	upper bool
}

func NewCaseChangingStream(in antlr.CharStream, upper bool) *CaseChangingStream {
	return &CaseChangingStream{
		in, upper,
	}
}

func (is *CaseChangingStream) LA(offset int) int {
	in := is.CharStream.LA(offset)
	if in < 0 {
		// Such as antlr.TokenEOF which is -1
		return in
	}
	if is.upper {
		return int(unicode.ToUpper(rune(in)))
	}
	return int(unicode.ToLower(rune(in)))
}