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70 lines
1.9 KiB
70 lines
1.9 KiB
// Copyright 2016 Google Inc. All rights reserved. |
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// |
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// Licensed under the Apache License, Version 2.0 (the "License"); |
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// you may not use this file except in compliance with the License. |
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// You may obtain a copy of the License at |
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// |
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// http://www.apache.org/licenses/LICENSE-2.0 |
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// |
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// Unless required by applicable law or agreed to in writing, software |
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// distributed under the License is distributed on an "AS IS" BASIS, |
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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// See the License for the specific language governing permissions and |
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// limitations under the License. |
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package android |
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import ( |
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"fmt" |
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"strings" |
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"unicode" |
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) |
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// Expand substitutes $() variables in a string |
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// $(var) is passed to Expander(var) |
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// $$ is converted to $ |
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func Expand(s string, mapping func(string) (string, error)) (string, error) { |
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// based on os.Expand |
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buf := make([]byte, 0, 2*len(s)) |
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i := 0 |
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for j := 0; j < len(s); j++ { |
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if s[j] == '$' { |
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if j+1 >= len(s) { |
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return "", fmt.Errorf("expected character after '$'") |
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} |
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buf = append(buf, s[i:j]...) |
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value, w, err := getMapping(s[j+1:], mapping) |
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if err != nil { |
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return "", err |
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} |
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buf = append(buf, value...) |
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j += w |
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i = j + 1 |
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} |
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} |
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return string(buf) + s[i:], nil |
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} |
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func getMapping(s string, mapping func(string) (string, error)) (string, int, error) { |
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switch s[0] { |
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case '(': |
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// Scan to closing brace |
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for i := 1; i < len(s); i++ { |
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if s[i] == ')' { |
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ret, err := mapping(strings.TrimSpace(s[1:i])) |
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return ret, i + 1, err |
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} |
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} |
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return "", len(s), fmt.Errorf("missing )") |
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case '$': |
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return "$$", 1, nil |
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default: |
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i := strings.IndexFunc(s, unicode.IsSpace) |
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if i == 0 { |
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return "", 0, fmt.Errorf("unexpected character '%c' after '$'", s[0]) |
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} else if i == -1 { |
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i = len(s) |
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} |
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return "", 0, fmt.Errorf("expected '(' after '$', did you mean $(%s)?", s[:i]) |
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} |
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}
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