76 lines
1.6 KiB
Go
76 lines
1.6 KiB
Go
package csstring
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func seekClosingBracket(s string, i int) int {
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for ; i < len(s); i++ {
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if s[i] == '}' {
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return i
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}
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}
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return -1
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}
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func seekEndVarname(s string, i int) int {
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// envvar names are more strict but this is good enough
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for ; i < len(s); i++ {
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if (s[i] < 'a' || s[i] > 'z') && (s[i] < 'A' || s[i] > 'Z') && (s[i] < '0' || s[i] > '9') && s[i] != '_' {
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break
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}
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}
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return i
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}
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func replaceVarBracket(s string, i int, mapping func(string) (string, bool)) string {
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j := seekClosingBracket(s, i+2)
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if j < 0 {
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return s
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}
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if j < len(s) {
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varName := s[i+2 : j]
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if val, ok := mapping(varName); ok {
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s = s[:i] + val + s[j+1:]
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}
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}
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return s
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}
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func replaceVar(s string, i int, mapping func(string) (string, bool)) string {
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if s[i+1] == '{' {
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return replaceVarBracket(s, i, mapping)
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}
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j := seekEndVarname(s, i+1)
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if j < 0 {
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return s
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}
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if j > i+1 {
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varName := s[i+1 : j]
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if val, ok := mapping(varName); ok {
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s = s[:i] + val + s[j:]
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}
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}
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return s
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}
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// StrictExpand replaces ${var} or $var in the string according to the mapping
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// function, like os.Expand. The difference is that the mapping function
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// returns a boolean indicating whether the variable was found.
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// If the variable was not found, the string is not modified.
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//
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// Whereas os.ExpandEnv uses os.Getenv, here we can use os.LookupEnv
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// to distinguish between an empty variable and an undefined one.
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func StrictExpand(s string, mapping func(string) (string, bool)) string {
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for i := 0; i < len(s); i++ {
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if s[i] == '$' {
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s = replaceVar(s, i, mapping)
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}
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}
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return s
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}
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