[go] internal/zstd: refactor huffman symbol decoding
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Garrick Gross (Gerrit)
Dec 28, 2025, 8:51:03 PM (7 hours ago) Dec 28
to goph...@pubsubhelper.golang.org, golang-co...@googlegroups.com
Garrick Gross has uploaded the change for review![]( "Open in Gerrit")
Commit message
internal/zstd: refactor huffman symbol decoding
Refactor duplicated decoding logic in readLiteralsOneStream and readLiteralsFourStreams into a shared decodeSymbol helper. No behavior changes
all.bash tests pass successfully after change.
Fixes #64031
Change-Id: Id26eb64de41b3fa2ab1d021b5905e50d524fb231
Change diff
diff --git a/src/internal/zstd/literals.go b/src/internal/zstd/literals.go
index 11ef859..af2ad5d 100644
--- a/src/internal/zstd/literals.go
+++ b/src/internal/zstd/literals.go
@@ -175,6 +175,18 @@
return roff, outbuf, nil
}
+func decodeSymbol(huffBits, huffMask uint32, huffTable []uint16, rbr *reverseBitReader, outbuf []byte, off int) (int, error) {
+ if !rbr.fetch(uint8(huffBits)) {
+ return 0, rbr.makeError("literals Huffman stream out of bits")
+ }
+ idx := (rbr.bits >> (rbr.cnt - huffBits)) & huffMask
+ t := huffTable[idx]
+ outbuf[off] = byte(t >> 8)
+ off++
+ rbr.cnt -= uint32(t & 0xff)
+ return off, nil
+}
+
// readLiteralsOneStream reads a single stream of compressed literals.
func (r *Reader) readLiteralsOneStream(data block, off, compressedSize, regeneratedSize int, outbuf []byte) ([]byte, error) {
// We let the reverse bit reader read earlier bytes,
@@ -188,16 +200,14 @@
huffBits := uint32(r.huffmanTableBits)
huffMask := (uint32(1) << huffBits) - 1
- for i := 0; i < regeneratedSize; i++ {
- if !rbr.fetch(uint8(huffBits)) {
- return nil, rbr.makeError("literals Huffman stream out of bits")
- }
+ out := len(outbuf)
+ outbuf = append(outbuf, make([]byte, regeneratedSize)...)
- var t uint16
- idx := (rbr.bits >> (rbr.cnt - huffBits)) & huffMask
- t = huffTable[idx]
- outbuf = append(outbuf, byte(t>>8))
- rbr.cnt -= uint32(t & 0xff)
+ for i := 0; i < regeneratedSize; i++ {
+ out, err = decodeSymbol(huffBits, huffMask, huffTable, &rbr, outbuf, out)
+ if err != nil {
+ return nil, err
+ }
}
return outbuf, nil
@@ -286,50 +296,25 @@
for i := 0; i < regeneratedStreamSize; i++ {
use4 := i < regeneratedStreamSize4
- fetchHuff := func(rbr *reverseBitReader) (uint16, error) {
- if !rbr.fetch(uint8(huffBits)) {
- return 0, rbr.makeError("literals Huffman stream out of bits")
- }
- idx := (rbr.bits >> (rbr.cnt - huffBits)) & huffMask
- return huffTable[idx], nil
- }
-
- t1, err := fetchHuff(&rbr1)
+ var err error
+ out1, err = decodeSymbol(huffBits, huffMask, huffTable, &rbr1, outbuf, out1)
if err != nil {
return nil, err
}
-
- t2, err := fetchHuff(&rbr2)
+ out2, err = decodeSymbol(huffBits, huffMask, huffTable, &rbr2, outbuf, out2)
if err != nil {
return nil, err
}
-
- t3, err := fetchHuff(&rbr3)
+ out3, err = decodeSymbol(huffBits, huffMask, huffTable, &rbr3, outbuf, out3)
if err != nil {
return nil, err
}
-
if use4 {
- t4, err := fetchHuff(&rbr4)
+ out4, err = decodeSymbol(huffBits, huffMask, huffTable, &rbr4, outbuf, out4)
if err != nil {
return nil, err
}
- outbuf[out4] = byte(t4 >> 8)
- out4++
- rbr4.cnt -= uint32(t4 & 0xff)
}
-
- outbuf[out1] = byte(t1 >> 8)
- out1++
- rbr1.cnt -= uint32(t1 & 0xff)
-
- outbuf[out2] = byte(t2 >> 8)
- out2++
- rbr2.cnt -= uint32(t2 & 0xff)
-
- outbuf[out3] = byte(t3 >> 8)
- out3++
- rbr3.cnt -= uint32(t3 & 0xff)
}
return outbuf, nil
Change information
Files:
- M src/internal/zstd/literals.go
Change size: M
Delta: 1 file changed, 24 insertions(+), 39 deletions(-)
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Gopher Robot (Gerrit)
Dec 28, 2025, 8:54:50 PM (7 hours ago) Dec 28
to Garrick Gross, goph...@pubsubhelper.golang.org, golang-co...@googlegroups.com
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Ian Lance Taylor (Gerrit)
Dec 28, 2025, 9:02:16 PM (7 hours ago) Dec 28
to Garrick Gross, goph...@pubsubhelper.golang.org, Ian Lance Taylor, Gopher Robot, golang-co...@googlegroups.com
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Ian Lance Taylor voted Commit-Queue+1![]( "Open in Gerrit")
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