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Use fnv64a instead of sha256 for cache keys #15

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Use fnv64a instead of sha256 for cache keys #15

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6 changes: 3 additions & 3 deletions cache.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,6 @@ package httpcache
import (
"bufio"
"bytes"
"crypto/sha256"
"errors"
"fmt"
"io"
Expand All @@ -16,6 +15,7 @@ import (
"strings"
"time"

"hash/fnv"
"github.com/rainycape/vfs"
)

Expand Down Expand Up @@ -190,8 +190,8 @@ func (c *Cache) Freshen(res *Resource, keys ...string) error {
}

func hashKey(key string) string {
h := sha256.New()
io.WriteString(h, key)
h := fnv.New64a()
h.Write([]byte(key))
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@dmitshur dmitshur Aug 7, 2015

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I would imagine a part of the speedup comes from using Write method directly, instead of going through io.WriteString which incurs a func call and additional computation (a type assertion which fails).

Have you tried benchmarking with sha256 but rewriting it to do h.Write([]byte(key)) as well? How does that compare?

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@hectorj hectorj Aug 7, 2015

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I did in there : https://gist.github.com/hectorj/8ac959c071d44ec4d718#file-cache_key_hash_test-go-L19

Though I only included the fastest results in the gist, and I don't have the numbers right here right now (will get them once I'm home)
IIRC Write([]byte(key)) instead of WriteString does help a bit, but FNV stays faster than sha256

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@dmitshur dmitshur Aug 7, 2015

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IIRC Write([]byte(key)) instead of WriteString does help a bit, but FNV stays faster than sha256

Cool, thanks. I was just curious.

return fmt.Sprintf("%x", h.Sum(nil))
}

Expand Down