From 811b187a4f1e8052eb84a03b5fb399af1eefbdbe Mon Sep 17 00:00:00 2001 From: =?utf8?q?Daniel=20Mart=C3=AD?= Date: Fri, 18 May 2018 18:31:05 +0100 Subject: [PATCH] encoding/base64: slight decoding speed-up MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit First, use a dummy slice access on decode64 and decode32 to ensure that there is a single bounds check for src. Second, move the PutUint64/PutUint32 calls out of these functions, meaning that they are simpler and smaller. This may also open the door to inlineability in the future, but for now, they both go past the budget. While at it, get rid of the ilen and olen variables, which have no impact whatsoever on performance. At least, not measurable by any of the benchmarks. name old time/op new time/op delta DecodeString/2-4 54.3ns ± 1% 55.2ns ± 2% +1.60% (p=0.017 n=5+6) DecodeString/4-4 66.6ns ± 1% 66.8ns ± 2% ~ (p=0.903 n=6+6) DecodeString/8-4 79.3ns ± 2% 79.6ns ± 1% ~ (p=0.448 n=6+6) DecodeString/64-4 300ns ± 1% 281ns ± 3% -6.54% (p=0.002 n=6+6) DecodeString/8192-4 27.4µs ± 1% 23.7µs ± 2% -13.47% (p=0.002 n=6+6) name old speed new speed delta DecodeString/2-4 73.7MB/s ± 1% 72.5MB/s ± 2% -1.55% (p=0.026 n=5+6) DecodeString/4-4 120MB/s ± 1% 120MB/s ± 2% ~ (p=0.851 n=6+6) DecodeString/8-4 151MB/s ± 2% 151MB/s ± 1% ~ (p=0.485 n=6+6) DecodeString/64-4 292MB/s ± 1% 313MB/s ± 3% +7.03% (p=0.002 n=6+6) DecodeString/8192-4 399MB/s ± 1% 461MB/s ± 2% +15.58% (p=0.002 n=6+6) For #19636. Change-Id: I0dfbdafa2a41dc4c582f63aef94b90b8e473731c Reviewed-on: https://go-review.googlesource.com/113776 Reviewed-by: Ian Lance Taylor --- src/encoding/base64/base64.go | 66 +++++++++++++++++------------------ 1 file changed, 32 insertions(+), 34 deletions(-) diff --git a/src/encoding/base64/base64.go b/src/encoding/base64/base64.go index 9a99370f1e..e8afc48859 100644 --- a/src/encoding/base64/base64.go +++ b/src/encoding/base64/base64.go @@ -465,10 +465,9 @@ func (enc *Encoding) Decode(dst, src []byte) (n int, err error) { } si := 0 - ilen := len(src) - olen := len(dst) - for strconv.IntSize >= 64 && ilen-si >= 8 && olen-n >= 8 { - if ok := enc.decode64(dst[n:], src[si:]); ok { + for strconv.IntSize >= 64 && len(src)-si >= 8 && len(dst)-n >= 8 { + if dn, ok := enc.decode64(src[si:]); ok { + binary.BigEndian.PutUint64(dst[n:], dn) n += 6 si += 8 } else { @@ -481,8 +480,9 @@ func (enc *Encoding) Decode(dst, src []byte) (n int, err error) { } } - for ilen-si >= 4 && olen-n >= 4 { - if ok := enc.decode32(dst[n:], src[si:]); ok { + for len(src)-si >= 4 && len(dst)-n >= 4 { + if dn, ok := enc.decode32(src[si:]); ok { + binary.BigEndian.PutUint32(dst[n:], dn) n += 3 si += 4 } else { @@ -506,72 +506,70 @@ func (enc *Encoding) Decode(dst, src []byte) (n int, err error) { return n, err } -// decode32 tries to decode 4 base64 char into 3 bytes. -// len(dst) and len(src) must both be >= 4. -// Returns true if decode succeeded. -func (enc *Encoding) decode32(dst, src []byte) bool { - var dn, n uint32 +// decode32 tries to decode 4 base64 characters into 3 bytes, and returns those +// bytes. len(src) must be >= 4. +// Returns (0, false) if decoding failed. +func (enc *Encoding) decode32(src []byte) (dn uint32, ok bool) { + var n uint32 + _ = src[3] if n = uint32(enc.decodeMap[src[0]]); n == 0xff { - return false + return 0, false } dn |= n << 26 if n = uint32(enc.decodeMap[src[1]]); n == 0xff { - return false + return 0, false } dn |= n << 20 if n = uint32(enc.decodeMap[src[2]]); n == 0xff { - return false + return 0, false } dn |= n << 14 if n = uint32(enc.decodeMap[src[3]]); n == 0xff { - return false + return 0, false } dn |= n << 8 - - binary.BigEndian.PutUint32(dst, dn) - return true + return dn, true } -// decode64 tries to decode 8 base64 char into 6 bytes. -// len(dst) and len(src) must both be >= 8. -// Returns true if decode succeeded. -func (enc *Encoding) decode64(dst, src []byte) bool { - var dn, n uint64 +// decode64 tries to decode 8 base64 characters into 6 bytes, and returns those +// bytes. len(src) must be >= 8. +// Returns (0, false) if decoding failed. +func (enc *Encoding) decode64(src []byte) (dn uint64, ok bool) { + var n uint64 + _ = src[7] if n = uint64(enc.decodeMap[src[0]]); n == 0xff { - return false + return 0, false } dn |= n << 58 if n = uint64(enc.decodeMap[src[1]]); n == 0xff { - return false + return 0, false } dn |= n << 52 if n = uint64(enc.decodeMap[src[2]]); n == 0xff { - return false + return 0, false } dn |= n << 46 if n = uint64(enc.decodeMap[src[3]]); n == 0xff { - return false + return 0, false } dn |= n << 40 if n = uint64(enc.decodeMap[src[4]]); n == 0xff { - return false + return 0, false } dn |= n << 34 if n = uint64(enc.decodeMap[src[5]]); n == 0xff { - return false + return 0, false } dn |= n << 28 if n = uint64(enc.decodeMap[src[6]]); n == 0xff { - return false + return 0, false } dn |= n << 22 if n = uint64(enc.decodeMap[src[7]]); n == 0xff { - return false + return 0, false } dn |= n << 16 - - binary.BigEndian.PutUint64(dst, dn) - return true + return dn, true } type newlineFilteringReader struct { -- 2.50.0