56 lines
1.2 KiB
Go
56 lines
1.2 KiB
Go
package parser
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import (
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"encoding/binary"
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"io"
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"os"
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)
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// This cache implementation is using a temp file to provide key-value data storage
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// It allows to avoid storing intermediate calculations in RAM
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// The stored data must be a fixed-size value or a slice of fixed-size values, or a pointer to such data
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type cache struct {
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file *os.File
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chunkSize int64
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}
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func newCache(filename string, data interface{}) (*cache, error) {
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f, err := os.CreateTemp("", filename)
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if err != nil {
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return nil, err
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}
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if err := os.Remove(f.Name()); err != nil {
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return nil, err
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}
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return &cache{file: f, chunkSize: int64(binary.Size(data))}, nil
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}
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func (c *cache) SetEntry(id Id, data interface{}) error {
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if err := c.setOffset(id); err != nil {
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return err
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}
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return binary.Write(c.file, binary.LittleEndian, data)
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}
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func (c *cache) Entry(id Id, data interface{}) error {
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if err := c.setOffset(id); err != nil {
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return err
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}
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return binary.Read(c.file, binary.LittleEndian, data)
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}
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func (c *cache) Close() error {
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return c.file.Close()
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}
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func (c *cache) setOffset(id Id) error {
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offset := int64(id) * c.chunkSize
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_, err := c.file.Seek(offset, io.SeekStart)
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return err
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}
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