github.com/westcoastroms/westcoastroms-build@v0.0.0-20190928114312-2350e5a73030/build/soong/android/expand.go (about)

     1  // Copyright 2016 Google Inc. All rights reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package android
    16  
    17  import (
    18  	"fmt"
    19  	"strings"
    20  	"unicode"
    21  )
    22  
    23  // Expand substitutes $() variables in a string
    24  // $(var) is passed to Expander(var)
    25  // $$ is converted to $
    26  func Expand(s string, mapping func(string) (string, error)) (string, error) {
    27  	// based on os.Expand
    28  	buf := make([]byte, 0, 2*len(s))
    29  	i := 0
    30  	for j := 0; j < len(s); j++ {
    31  		if s[j] == '$' {
    32  			if j+1 >= len(s) {
    33  				return "", fmt.Errorf("expected character after '$'")
    34  			}
    35  			buf = append(buf, s[i:j]...)
    36  			value, w, err := getMapping(s[j+1:], mapping)
    37  			if err != nil {
    38  				return "", err
    39  			}
    40  			buf = append(buf, value...)
    41  			j += w
    42  			i = j + 1
    43  		}
    44  	}
    45  	return string(buf) + s[i:], nil
    46  }
    47  
    48  func getMapping(s string, mapping func(string) (string, error)) (string, int, error) {
    49  	switch s[0] {
    50  	case '(':
    51  		// Scan to closing brace
    52  		for i := 1; i < len(s); i++ {
    53  			if s[i] == ')' {
    54  				ret, err := mapping(strings.TrimSpace(s[1:i]))
    55  				return ret, i + 1, err
    56  			}
    57  		}
    58  		return "", len(s), fmt.Errorf("missing )")
    59  	case '$':
    60  		return "$$", 1, nil
    61  	default:
    62  		i := strings.IndexFunc(s, unicode.IsSpace)
    63  		if i == 0 {
    64  			return "", 0, fmt.Errorf("unexpected character '%c' after '$'", s[0])
    65  		} else if i == -1 {
    66  			i = len(s)
    67  		}
    68  		return "", 0, fmt.Errorf("expected '(' after '$', did you mean $(%s)?", s[:i])
    69  	}
    70  }