59 lines
1.3 KiB
Go
59 lines
1.3 KiB
Go
package cache
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import "sync"
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// Functions for caching redirects.
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var redirUrls = make(map[string]string) // map original URL to redirect
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var redirMu = sync.RWMutex{}
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// AddRedir adds a original-to-redirect pair to the cache.
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func AddRedir(og, redir string) {
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redirMu.Lock()
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defer redirMu.Unlock()
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for k, v := range redirUrls {
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if og == v {
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// The original URL param is the redirect URL for `k`.
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// This means there is a chain: k -> og -> redir
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// The chain should be removed
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redirUrls[k] = redir
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}
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if redir == k {
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// There's a loop
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// The newer version is preferred
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delete(redirUrls, k)
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}
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}
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redirUrls[og] = redir
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}
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// ClearRedirs removes all redirects from the cache.
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func ClearRedirs() {
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redirMu.Lock()
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redirUrls = make(map[string]string)
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redirMu.Unlock()
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}
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// Redirect takes the provided URL and returns a redirected version, if a redirect
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// exists for that URL in the cache.
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// If one does not then the original URL is returned.
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func Redirect(u string) string {
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redirMu.RLock()
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defer redirMu.RUnlock()
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// A single lookup is enough, because AddRedir
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// removes loops and chains.
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redir, ok := redirUrls[u]
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if ok {
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return redir
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}
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return u
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}
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func NumRedirs() int {
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redirMu.RLock()
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defer redirMu.RUnlock()
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return len(redirUrls)
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}
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