chore: migrate to gitea

vendor/github.com/googleapis/gax-go/v2/callctx/callctx.go

@@ -0,0 +1,100 @@
+// Copyright 2023, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Package callctx provides helpers for storing and retrieving values out of
+// [context.Context]. These values are used by our client libraries in various
+// ways across the stack.
+package callctx
+
+import (
+	"context"
+	"fmt"
+)
+
+const (
+	// XGoogFieldMaskHeader is the canonical header key for the [System Parameter]
+	// that specifies the response read mask. The value(s) for this header
+	// must adhere to format described in [fieldmaskpb].
+	//
+	// [System Parameter]: https://cloud.google.com/apis/docs/system-parameters
+	// [fieldmaskpb]: https://google.golang.org/protobuf/types/known/fieldmaskpb
+	XGoogFieldMaskHeader = "x-goog-fieldmask"
+
+	headerKey = contextKey("header")
+)
+
+// contextKey is a private type used to store/retrieve context values.
+type contextKey string
+
+// HeadersFromContext retrieves headers set from [SetHeaders]. These headers
+// can then be cast to http.Header or metadata.MD to send along on requests.
+func HeadersFromContext(ctx context.Context) map[string][]string {
+	m, ok := ctx.Value(headerKey).(map[string][]string)
+	if !ok {
+		return nil
+	}
+	return m
+}
+
+// SetHeaders stores key value pairs in the returned context that can later
+// be retrieved by [HeadersFromContext]. Values stored in this manner will
+// automatically be retrieved by client libraries and sent as outgoing headers
+// on all requests. keyvals should have a corresponding value for every key
+// provided. If there is an odd number of keyvals this method will panic.
+func SetHeaders(ctx context.Context, keyvals ...string) context.Context {
+	if len(keyvals)%2 != 0 {
+		panic(fmt.Sprintf("callctx: an even number of key value pairs must be provided, got %d", len(keyvals)))
+	}
+	h, ok := ctx.Value(headerKey).(map[string][]string)
+	if !ok {
+		h = make(map[string][]string)
+	} else {
+		h = cloneHeaders(h)
+	}
+
+	for i := 0; i < len(keyvals); i = i + 2 {
+		h[keyvals[i]] = append(h[keyvals[i]], keyvals[i+1])
+	}
+	return context.WithValue(ctx, headerKey, h)
+}
+
+// cloneHeaders makes a new key-value map while reusing the value slices.
+// As such, new values should be appended to the value slice, and modifying
+// indexed values is not thread safe.
+//
+// TODO: Replace this with maps.Clone when Go 1.21 is the minimum version.
+func cloneHeaders(h map[string][]string) map[string][]string {
+	c := make(map[string][]string, len(h))
+	for k, v := range h {
+		vc := make([]string, len(v))
+		copy(vc, v)
+		c[k] = vc
+	}
+	return c
+}