Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

avoid double alloc in NewCidV1 #132

Merged
merged 1 commit into from Sep 12, 2021
Merged

avoid double alloc in NewCidV1 #132

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Jump to
Jump to file
Failed to load files.
Diff view
Diff view
21 changes: 15 additions & 6 deletions cid.go
View file
Open in desktop
Expand Up @@ -22,6 +22,7 @@ package cid
import (
"bytes"
"encoding"
"encoding/binary"
"encoding/json"
"errors"
"fmt"
Expand Down Expand Up @@ -173,16 +174,24 @@ func NewCidV0(mhash mh.Multihash) Cid {
// Panics if the multihash is invalid.
func NewCidV1(codecType uint64, mhash mh.Multihash) Cid {
hashlen := len(mhash)
// two 8 bytes (max) numbers plus hash
buf := make([]byte, 1+varint.UvarintSize(codecType)+hashlen)
n := varint.PutUvarint(buf, 1)
n += varint.PutUvarint(buf[n:], codecType)
cn := copy(buf[n:], mhash)

// Two 8 bytes (max) numbers plus hash.
// We use strings.Builder to only allocate once.
var b strings.Builder
b.Grow(1 + varint.UvarintSize(codecType) + hashlen)

b.WriteByte(1)

var buf [binary.MaxVarintLen64]byte
n := varint.PutUvarint(buf[:], codecType)
b.Write(buf[:n])

cn, _ := b.Write(mhash)
if cn != hashlen {
panic("copy hash length is inconsistent")
}

return Cid{string(buf[:n+hashlen])}
return Cid{b.String()}
}

var (
Expand Down