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90 lines
2.8 KiB
90 lines
2.8 KiB
/*
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Copyright The Helm 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 downloader
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import (
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"crypto/sha256"
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"errors"
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"fmt"
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"io"
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"log/slog"
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"os"
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"path/filepath"
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"helm.sh/helm/v4/internal/fileutil"
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)
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// Cache describes a cache that can get and put chart data.
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// The cache key is the sha256 has of the content. sha256 is used in Helm for
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// digests in index files providing a common key for checking content.
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type Cache interface {
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// Get returns a reader for the given key.
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Get(key [sha256.Size]byte, cacheType string) (string, error)
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// Put stores the given reader for the given key.
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Put(key [sha256.Size]byte, data io.Reader, cacheType string) (string, error)
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}
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// CacheChart specifies the content is a chart
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var CacheChart = ".chart"
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// CacheProv specifies the content is a provenance file
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var CacheProv = ".prov"
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// TODO: The cache assumes files because much of Helm assumes files. Convert
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// Helm to pass content around instead of file locations.
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// DiskCache is a cache that stores data on disk.
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type DiskCache struct {
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Root string
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}
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// Get returns a reader for the given key.
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func (c *DiskCache) Get(key [sha256.Size]byte, cacheType string) (string, error) {
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p := c.fileName(key, cacheType)
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fi, err := os.Stat(p)
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if err != nil {
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return "", err
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}
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// Empty files treated as not exist because there is no content.
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if fi.Size() == 0 {
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return p, os.ErrNotExist
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}
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// directories should never happen unless something outside helm is operating
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// on this content.
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if fi.IsDir() {
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return p, errors.New("is a directory")
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}
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return p, nil
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}
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// Put stores the given reader for the given key.
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// It returns the path to the stored file.
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func (c *DiskCache) Put(key [sha256.Size]byte, data io.Reader, cacheType string) (string, error) {
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// TODO: verify the key and digest of the key are the same.
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p := c.fileName(key, cacheType)
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if err := os.MkdirAll(filepath.Dir(p), 0755); err != nil {
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slog.Error("failed to create cache directory")
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return p, err
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}
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return p, fileutil.AtomicWriteFile(p, data, 0644)
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}
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// fileName generates the filename in a structured manner where the first part is the
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// directory and the full hash is the filename.
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func (c *DiskCache) fileName(id [sha256.Size]byte, cacheType string) string {
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return filepath.Join(c.Root, fmt.Sprintf("%02x", id[0]), fmt.Sprintf("%x", id)+cacheType)
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}
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