53 lines
1.3 KiB
Go
53 lines
1.3 KiB
Go
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package cache
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import (
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"sync"
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"github.com/evanw/esbuild/internal/fs"
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)
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// This cache uses information from the "stat" syscall to try to avoid re-
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// reading files from the file system during subsequent builds if the file
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// hasn't changed. The assumption is reading the file metadata is faster than
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// reading the file contents.
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type FSCache struct {
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mutex sync.Mutex
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entries map[string]*fsEntry
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}
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type fsEntry struct {
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contents string
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modKey fs.ModKey
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isModKeyUsable bool
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}
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func (c *FSCache) ReadFile(fs fs.FS, path string) (contents string, canonicalError error, originalError error) {
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entry := func() *fsEntry {
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c.mutex.Lock()
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defer c.mutex.Unlock()
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return c.entries[path]
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}()
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// If the file's modification key hasn't changed since it was cached, assume
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// the contents of the file are also the same and skip reading the file.
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modKey, modKeyErr := fs.ModKey(path)
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if entry != nil && entry.isModKeyUsable && modKeyErr == nil && entry.modKey == modKey {
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return entry.contents, nil, nil
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}
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contents, err, originalError := fs.ReadFile(path)
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if err != nil {
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return "", err, originalError
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}
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c.mutex.Lock()
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defer c.mutex.Unlock()
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c.entries[path] = &fsEntry{
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contents: contents,
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modKey: modKey,
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isModKeyUsable: modKeyErr == nil,
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}
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return contents, nil, nil
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}
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