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[Go] Force a single, early bounds check on read and write paths. 

As an example, GetInt64 used to perform 8 bounds checks, one for each
slice access. By performing a bound check on the highest index, the
number of checks is reduced to one through bounds-check-elimination.
This commit is contained in:
Brian Atkinson 2018-07-15 16:38:56 -07:00
parent e2eb6af3e3
commit b3e4d9169b
1 changed files with 12 additions and 0 deletions
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12
go/encode.go
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@ -36,6 +36,7 @@ func GetUint8(buf []byte) (n uint8) {
// GetUint16 decodes a little-endian uint16 from a byte slice.
func GetUint16(buf []byte) (n uint16) {
_ = buf[1] // Force one bounds check. See: golang.org/issue/14808
n |= uint16(buf[0])
n |= uint16(buf[1]) << 8
return
@ -43,6 +44,7 @@ func GetUint16(buf []byte) (n uint16) {
// GetUint32 decodes a little-endian uint32 from a byte slice.
func GetUint32(buf []byte) (n uint32) {
_ = buf[3] // Force one bounds check. See: golang.org/issue/14808
n |= uint32(buf[0])
n |= uint32(buf[1]) << 8
n |= uint32(buf[2]) << 16
@ -52,6 +54,7 @@ func GetUint32(buf []byte) (n uint32) {
// GetUint64 decodes a little-endian uint64 from a byte slice.
func GetUint64(buf []byte) (n uint64) {
_ = buf[7] // Force one bounds check. See: golang.org/issue/14808
n |= uint64(buf[0])
n |= uint64(buf[1]) << 8
n |= uint64(buf[2]) << 16
@ -71,6 +74,7 @@ func GetInt8(buf []byte) (n int8) {
// GetInt16 decodes a little-endian int16 from a byte slice.
func GetInt16(buf []byte) (n int16) {
_ = buf[1] // Force one bounds check. See: golang.org/issue/14808
n |= int16(buf[0])
n |= int16(buf[1]) << 8
return
@ -78,6 +82,7 @@ func GetInt16(buf []byte) (n int16) {
// GetInt32 decodes a little-endian int32 from a byte slice.
func GetInt32(buf []byte) (n int32) {
_ = buf[3] // Force one bounds check. See: golang.org/issue/14808
n |= int32(buf[0])
n |= int32(buf[1]) << 8
n |= int32(buf[2]) << 16
@ -87,6 +92,7 @@ func GetInt32(buf []byte) (n int32) {
// GetInt64 decodes a little-endian int64 from a byte slice.
func GetInt64(buf []byte) (n int64) {
_ = buf[7] // Force one bounds check. See: golang.org/issue/14808
n |= int64(buf[0])
n |= int64(buf[1]) << 8
n |= int64(buf[2]) << 16
@ -145,12 +151,14 @@ func WriteUint8(buf []byte, n uint8) {
// WriteUint16 encodes a little-endian uint16 into a byte slice.
func WriteUint16(buf []byte, n uint16) {
_ = buf[1] // Force one bounds check. See: golang.org/issue/14808
buf[0] = byte(n)
buf[1] = byte(n >> 8)
}
// WriteUint32 encodes a little-endian uint32 into a byte slice.
func WriteUint32(buf []byte, n uint32) {
_ = buf[3] // Force one bounds check. See: golang.org/issue/14808
buf[0] = byte(n)
buf[1] = byte(n >> 8)
buf[2] = byte(n >> 16)
@ -159,6 +167,7 @@ func WriteUint32(buf []byte, n uint32) {
// WriteUint64 encodes a little-endian uint64 into a byte slice.
func WriteUint64(buf []byte, n uint64) {
_ = buf[7] // Force one bounds check. See: golang.org/issue/14808
buf[0] = byte(n)
buf[1] = byte(n >> 8)
buf[2] = byte(n >> 16)
@ -176,12 +185,14 @@ func WriteInt8(buf []byte, n int8) {
// WriteInt16 encodes a little-endian int16 into a byte slice.
func WriteInt16(buf []byte, n int16) {
_ = buf[1] // Force one bounds check. See: golang.org/issue/14808
buf[0] = byte(n)
buf[1] = byte(n >> 8)
}
// WriteInt32 encodes a little-endian int32 into a byte slice.
func WriteInt32(buf []byte, n int32) {
_ = buf[3] // Force one bounds check. See: golang.org/issue/14808
buf[0] = byte(n)
buf[1] = byte(n >> 8)
buf[2] = byte(n >> 16)
@ -190,6 +201,7 @@ func WriteInt32(buf []byte, n int32) {
// WriteInt64 encodes a little-endian int64 into a byte slice.
func WriteInt64(buf []byte, n int64) {
_ = buf[7] // Force one bounds check. See: golang.org/issue/14808
buf[0] = byte(n)
buf[1] = byte(n >> 8)
buf[2] = byte(n >> 16)