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encode_amd64.go
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encode_amd64.go
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// +build !appengine
// +build !noasm
// +build gc
package s2
import "encoding/binary"
func init() {
avxAvailable = cpu.avx()
}
// encodeBlock encodes a non-empty src to a guaranteed-large-enough dst. It
// assumes that the varint-encoded length of the decompressed bytes has already
// been written.
//
// It also assumes that:
// len(dst) >= MaxEncodedLen(len(src)) &&
// minNonLiteralBlockSize <= len(src) && len(src) <= maxBlockSize
func encodeBlock(dst, src []byte) (d int) {
const (
// Use 12 bit table when less than...
limit12B = 16 << 10
// Use 10 bit table when less than...
limit10B = 4 << 10
// Use 8 bit table when less than...
limit8B = 512
)
if avxAvailable {
// Big blocks, use full table...
if len(src) >= limit12B {
return encodeBlockAsmAvx(dst, src)
}
if len(src) >= limit10B {
return encodeBlockAsm12BAvx(dst, src)
}
if len(src) >= limit8B {
return encodeBlockAsm10BAvx(dst, src)
}
if len(src) < minNonLiteralBlockSize {
return 0
}
return encodeBlockAsm8BAvx(dst, src)
}
if len(src) >= limit12B {
return encodeBlockAsm(dst, src)
}
if len(src) >= limit10B {
return encodeBlockAsm12B(dst, src)
}
if len(src) >= limit8B {
return encodeBlockAsm10B(dst, src)
}
if len(src) < minNonLiteralBlockSize {
return 0
}
return encodeBlockAsm8B(dst, src)
}
// EncodeSnappy returns the encoded form of src. The returned slice may be a sub-
// slice of dst if dst was large enough to hold the entire encoded block.
// Otherwise, a newly allocated slice will be returned.
//
// The output is Snappy compatible and will likely decompress faster.
//
// The dst and src must not overlap. It is valid to pass a nil dst.
//
// The blocks will require the same amount of memory to decode as encoding,
// and does not make for concurrent decoding.
// Also note that blocks do not contain CRC information, so corruption may be undetected.
//
// If you need to encode larger amounts of data, consider using
// the streaming interface which gives all of these features.
func EncodeSnappy(dst, src []byte) []byte {
if n := MaxEncodedLen(len(src)); n < 0 {
panic(ErrTooLarge)
} else if cap(dst) < n {
dst = make([]byte, n)
} else {
dst = dst[:n]
}
// The block starts with the varint-encoded length of the decompressed bytes.
d := binary.PutUvarint(dst, uint64(len(src)))
if len(src) == 0 {
return dst[:d]
}
if len(src) < minNonLiteralBlockSize {
d += emitLiteral(dst[d:], src)
return dst[:d]
}
n := encodeBlockSnappy(dst[d:], src)
if n > 0 {
d += n
return dst[:d]
}
// Not compressible
d += emitLiteral(dst[d:], src)
return dst[:d]
}
// encodeBlock encodes a non-empty src to a guaranteed-large-enough dst. It
// assumes that the varint-encoded length of the decompressed bytes has already
// been written.
//
// It also assumes that:
// len(dst) >= MaxEncodedLen(len(src)) &&
// minNonLiteralBlockSize <= len(src) && len(src) <= maxBlockSize
func encodeBlockSnappy(dst, src []byte) (d int) {
const (
// Use 12 bit table when less than...
limit12B = 16 << 10
// Use 10 bit table when less than...
limit10B = 4 << 10
// Use 8 bit table when less than...
limit8B = 512
)
if avxAvailable {
// Big blocks, use full table...
if len(src) >= limit12B {
return encodeSnappyBlockAsmAvx(dst, src)
}
if len(src) >= limit10B {
return encodeSnappyBlockAsm12BAvx(dst, src)
}
if len(src) >= limit8B {
return encodeSnappyBlockAsm10BAvx(dst, src)
}
if len(src) < minNonLiteralBlockSize {
return 0
}
return encodeSnappyBlockAsm8BAvx(dst, src)
}
if len(src) >= limit12B {
return encodeSnappyBlockAsm(dst, src)
}
if len(src) >= limit10B {
return encodeSnappyBlockAsm12B(dst, src)
}
if len(src) >= limit8B {
return encodeSnappyBlockAsm10B(dst, src)
}
if len(src) < minNonLiteralBlockSize {
return 0
}
return encodeSnappyBlockAsm8B(dst, src)
}