From 7eb7f8f5a75fcff520b5b93a7831fa7044d86887 Mon Sep 17 00:00:00 2001 From: Michael Schurter Date: Sat, 3 Jun 2017 13:36:54 -0700 Subject: encoding/json: reduce allocations by Decoder for \uXXXX MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Manually convert hex escape sequence to rune instead of calling strconv.ParseUint. This inlines the unhex func from docs (and many other packages). name old time/op new time/op delta UnicodeDecoder-4 468ns ± 1% 402ns ± 1% -14.26% (p=0.000 n=10+10) name old speed new speed delta UnicodeDecoder-4 29.9MB/s ± 1% 34.8MB/s ± 1% +16.59% (p=0.000 n=10+10) name old alloc/op new alloc/op delta UnicodeDecoder-4 44.0B ± 0% 36.0B ± 0% -18.18% (p=0.000 n=10+10) name old allocs/op new allocs/op delta UnicodeDecoder-4 4.00 ± 0% 2.00 ± 0% -50.00% (p=0.000 n=10+10) Fixes #20567 Change-Id: If350978d5bb98ff517485752184d02249f5d1f3a Reviewed-on: https://go-review.googlesource.com/44738 Run-TryBot: Russ Cox Reviewed-by: Russ Cox TryBot-Result: Gobot Gobot --- src/encoding/json/decode.go | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) (limited to 'src/encoding/json/decode.go') diff --git a/src/encoding/json/decode.go b/src/encoding/json/decode.go index 70179e60ac..4f98916105 100644 --- a/src/encoding/json/decode.go +++ b/src/encoding/json/decode.go @@ -1148,11 +1148,21 @@ func getu4(s []byte) rune { if len(s) < 6 || s[0] != '\\' || s[1] != 'u' { return -1 } - r, err := strconv.ParseUint(string(s[2:6]), 16, 64) - if err != nil { - return -1 + var r rune + for _, c := range s[2:6] { + switch { + case '0' <= c && c <= '9': + c = c - '0' + case 'a' <= c && c <= 'f': + c = c - 'a' + 10 + case 'A' <= c && c <= 'F': + c = c - 'A' + 10 + default: + return -1 + } + r = r*16 + rune(c) } - return rune(r) + return r } // unquote converts a quoted JSON string literal s into an actual string t. -- cgit v1.3-5-g9baa