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| author | Cholerae Hu <choleraehyq@gmail.com> | 2018-08-03 14:29:37 +0800 |
|---|---|---|
| committer | Brad Fitzpatrick <bradfitz@golang.org> | 2018-08-21 04:50:21 +0000 |
| commit | 2a5df067654970557f5038d238954eb9893e7f31 (patch) | |
| tree | 23f0e2a0db445c2d4e99aeeb4f9db708bc88dd8a /src/hash | |
| parent | 80fe2e6e37120e665cd523e1edf7eb1401b9b73b (diff) | |
| download | go-2a5df067654970557f5038d238954eb9893e7f31.tar.gz go-2a5df067654970557f5038d238954eb9893e7f31.zip | |
hash/crc64: lazily initialize slice8Tables
Saves 36KB of memory in stdlib packages.
Updates #26775
Change-Id: I0f9d7b17d9768f6fb980d5fbba7c45920215a5fc
Reviewed-on: https://go-review.googlesource.com/127735
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Diffstat (limited to 'src/hash')
| -rw-r--r-- | src/hash/crc64/crc64.go | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/src/hash/crc64/crc64.go b/src/hash/crc64/crc64.go index a799a017c9..063c63c6a3 100644 --- a/src/hash/crc64/crc64.go +++ b/src/hash/crc64/crc64.go @@ -10,6 +10,7 @@ package crc64 import ( "errors" "hash" + "sync" ) // The size of a CRC-64 checksum in bytes. @@ -28,13 +29,24 @@ const ( type Table [256]uint64 var ( - slicing8TableISO = makeSlicingBy8Table(makeTable(ISO)) - slicing8TableECMA = makeSlicingBy8Table(makeTable(ECMA)) + slicing8TablesBuildOnce sync.Once + slicing8TableISO *[8]Table + slicing8TableECMA *[8]Table ) +func buildSlicing8TablesOnce() { + slicing8TablesBuildOnce.Do(buildSlicing8Tables) +} + +func buildSlicing8Tables() { + slicing8TableISO = makeSlicingBy8Table(makeTable(ISO)) + slicing8TableECMA = makeSlicingBy8Table(makeTable(ECMA)) +} + // MakeTable returns a Table constructed from the specified polynomial. // The contents of this Table must not be modified. func MakeTable(poly uint64) *Table { + buildSlicing8TablesOnce() switch poly { case ISO: return &slicing8TableISO[0] @@ -141,6 +153,7 @@ func readUint64(b []byte) uint64 { } func update(crc uint64, tab *Table, p []byte) uint64 { + buildSlicing8TablesOnce() crc = ^crc // Table comparison is somewhat expensive, so avoid it for small sizes for len(p) >= 64 { |