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directives.go
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directives.go
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package dnsserver
import (
"fmt"
"os"
"strings"
)
// RegisterDevDirective splices name into the list of directives
// immediately before another directive. This function is ONLY
// for plugin development purposes! NEVER use it for a plugin
// that you are not currently building. If before is empty,
// the directive will be appended to the end of the list.
//
// It is imperative that directives execute in the proper
// order, and hard-coding the list of directives guarantees
// a correct, absolute order every time. This function is
// convenient when developing a plugin, but it does not
// guarantee absolute ordering. Multiple plugins registering
// directives with this function will lead to non-
// deterministic builds and buggy software.
//
// Directive names must be lower-cased and unique. Any errors
// here are fatal, and even successful calls print a message
// to stdout as a reminder to use it only in development.
func RegisterDevDirective(name, before string) {
if name == "" {
fmt.Println("[FATAL] Cannot register empty directive name")
os.Exit(1)
}
if strings.ToLower(name) != name {
fmt.Printf("[FATAL] %s: directive name must be lowercase\n", name)
os.Exit(1)
}
for _, dir := range directives {
if dir == name {
fmt.Printf("[FATAL] %s: directive name already exists\n", name)
os.Exit(1)
}
}
if before == "" {
directives = append(directives, name)
} else {
var found bool
for i, dir := range directives {
if dir == before {
directives = append(directives[:i], append([]string{name}, directives[i:]...)...)
found = true
break
}
}
if !found {
fmt.Printf("[FATAL] %s: directive not found\n", before)
os.Exit(1)
}
}
msg := fmt.Sprintf("Registered directive '%s' ", name)
if before == "" {
msg += "at end of list"
} else {
msg += fmt.Sprintf("before '%s'", before)
}
fmt.Printf("[INFO] %s\n", msg)
}