mirror of
https://gitea.com/Lydanne/buildx.git
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128 lines
3.4 KiB
Go
128 lines
3.4 KiB
Go
/*
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Copyright 2014 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package recognizer
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import (
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"bufio"
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"bytes"
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"fmt"
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"io"
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"k8s.io/apimachinery/pkg/runtime"
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"k8s.io/apimachinery/pkg/runtime/schema"
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)
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type RecognizingDecoder interface {
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runtime.Decoder
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// RecognizesData should return true if the input provided in the provided reader
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// belongs to this decoder, or an error if the data could not be read or is ambiguous.
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// Unknown is true if the data could not be determined to match the decoder type.
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// Decoders should assume that they can read as much of peek as they need (as the caller
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// provides) and may return unknown if the data provided is not sufficient to make a
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// a determination. When peek returns EOF that may mean the end of the input or the
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// end of buffered input - recognizers should return the best guess at that time.
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RecognizesData(peek io.Reader) (ok, unknown bool, err error)
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}
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// NewDecoder creates a decoder that will attempt multiple decoders in an order defined
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// by:
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//
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// 1. The decoder implements RecognizingDecoder and identifies the data
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// 2. All other decoders, and any decoder that returned true for unknown.
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//
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// The order passed to the constructor is preserved within those priorities.
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func NewDecoder(decoders ...runtime.Decoder) runtime.Decoder {
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return &decoder{
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decoders: decoders,
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}
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}
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type decoder struct {
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decoders []runtime.Decoder
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}
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var _ RecognizingDecoder = &decoder{}
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func (d *decoder) RecognizesData(peek io.Reader) (bool, bool, error) {
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var (
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lastErr error
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anyUnknown bool
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)
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data, _ := bufio.NewReaderSize(peek, 1024).Peek(1024)
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for _, r := range d.decoders {
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switch t := r.(type) {
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case RecognizingDecoder:
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ok, unknown, err := t.RecognizesData(bytes.NewBuffer(data))
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if err != nil {
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lastErr = err
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continue
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}
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anyUnknown = anyUnknown || unknown
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if !ok {
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continue
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}
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return true, false, nil
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}
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}
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return false, anyUnknown, lastErr
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}
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func (d *decoder) Decode(data []byte, gvk *schema.GroupVersionKind, into runtime.Object) (runtime.Object, *schema.GroupVersionKind, error) {
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var (
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lastErr error
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skipped []runtime.Decoder
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)
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// try recognizers, record any decoders we need to give a chance later
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for _, r := range d.decoders {
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switch t := r.(type) {
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case RecognizingDecoder:
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buf := bytes.NewBuffer(data)
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ok, unknown, err := t.RecognizesData(buf)
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if err != nil {
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lastErr = err
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continue
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}
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if unknown {
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skipped = append(skipped, t)
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continue
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}
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if !ok {
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continue
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}
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return r.Decode(data, gvk, into)
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default:
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skipped = append(skipped, t)
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}
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}
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// try recognizers that returned unknown or didn't recognize their data
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for _, r := range skipped {
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out, actual, err := r.Decode(data, gvk, into)
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if err != nil {
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lastErr = err
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continue
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}
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return out, actual, nil
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}
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if lastErr == nil {
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lastErr = fmt.Errorf("no serialization format matched the provided data")
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}
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return nil, nil, lastErr
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}
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