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chain.go
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chain.go
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package aviation
import (
"context"
"google.golang.org/grpc"
)
// ChainUnaryServer creates a single interceptor out of a chain of many interceptors.
//
// Execution is done in left-to-right order, including passing of context.
// For example ChainUnaryServer(one, two, three) will execute one before two before three, and three
// will see context changes of one and two.
//
// Implementation from https://github.com/grpc-ecosystem/go-grpc-middleware/blob/master/chain.go
func ChainUnaryServer(interceptors ...grpc.UnaryServerInterceptor) grpc.UnaryServerInterceptor {
n := len(interceptors)
if n > 1 {
lastI := n - 1
return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
var (
chainHandler grpc.UnaryHandler
curI int
)
chainHandler = func(currentCtx context.Context, currentReq interface{}) (interface{}, error) {
if curI == lastI {
return handler(currentCtx, currentReq)
}
curI++
resp, err := interceptors[curI](currentCtx, currentReq, info, chainHandler)
curI--
return resp, err
}
return interceptors[0](ctx, req, info, chainHandler)
}
}
if n == 1 {
return interceptors[0]
}
// n == 0; Dummy interceptor maintained for backward compatibility to avoid returning nil.
return func(ctx context.Context, req interface{}, _ *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
return handler(ctx, req)
}
}
// ChainStreamServer creates a single interceptor out of a chain of many interceptors.
//
// Execution is done in left-to-right order, including passing of context.
// For example ChainUnaryServer(one, two, three) will execute one before two before three.
// If you want to pass context between interceptors, use WrapServerStream.
//
// Implementation from https://github.com/grpc-ecosystem/go-grpc-middleware/blob/master/chain.go
func ChainStreamServer(interceptors ...grpc.StreamServerInterceptor) grpc.StreamServerInterceptor {
n := len(interceptors)
if n > 1 {
lastI := n - 1
return func(srv interface{}, stream grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
var (
chainHandler grpc.StreamHandler
curI int
)
chainHandler = func(currentSrv interface{}, currentStream grpc.ServerStream) error {
if curI == lastI {
return handler(currentSrv, currentStream)
}
curI++
err := interceptors[curI](currentSrv, currentStream, info, chainHandler)
curI--
return err
}
return interceptors[0](srv, stream, info, chainHandler)
}
}
if n == 1 {
return interceptors[0]
}
// n == 0; Dummy interceptor maintained for backward compatibility to avoid returning nil.
return func(srv interface{}, stream grpc.ServerStream, _ *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
return handler(srv, stream)
}
}