region: Simplify buffer funcs

Replace `growBuffer` with 'append' and `resizeBufferCap` with
`slices.Grow`. And remove redundant 'if' checks on capacity or size
that `append` will do as well. This is equivalent behavior after
undoing the unintentional change from commit 1fee39f. Benchmarks
show the performance is equivalent to the code before commit
1fee39f.

Also replace some deprecated calls to rand funcs.

region/client.go

@@ -108,10 +108,7 @@ func newBuffer(size int) []byte {
 	if v != nil {
 		b = v.([]byte)
 	}
-	if cap(b) < size {
-		return append(b[:0], make([]byte, size)...)[:size]
-	}
-	return b[:size]
+	return append(b[:0], make([]byte, size)...)
 }
 
 func freeBuffer(b []byte) {

region/compressor.go

@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"slices"
 
 	"github.com/tsuna/gohbase/compression"
 )
@@ -25,24 +26,6 @@ func min(x, y uint32) int {
 	return int(y)
 }
 
-func growBuffer(b []byte, sz int) []byte {
-	l := len(b) + sz
-	if l <= cap(b) {
-		return b[:l]
-	}
-	return append(b, make([]byte, sz)...)
-}
-
-func resizeBufferCap(b []byte, capacity int) []byte {
-	if capacity <= cap(b) {
-		return b
-	}
-
-	b2 := make([]byte, capacity)
-	copy(b2, b)
-	return b2[:len(b)]
-}
-
 func (c *compressor) compressCellblocks(cbs net.Buffers, uncompressedLen uint32) []byte {
 	b := newBuffer(4)
 
@@ -62,7 +45,7 @@ func (c *compressor) compressCellblocks(cbs net.Buffers, uncompressedLen uint32)
 
 		// grow for chunk length
 		lenOffset = len(b)
-		b = growBuffer(b, 4)
+		b = append(b, make([]byte, 4)...)
 
 		b, chunkLen = c.Encode(uncompressedBuffer[:n], b)
 
@@ -122,7 +105,7 @@ func (c *compressor) decompressCellblocks(b []byte) ([]byte, error) {
 			return nil, fmt.Errorf("failed to read uncompressed block length: %w", err)
 		}
 
-		out = resizeBufferCap(out, len(out)+int(uncompressedBlockLen))
+		out = slices.Grow(out, int(uncompressedBlockLen))
 
 		// read and decompress encoded chunks until whole block is read
 		var uncompressedSoFar uint32

region/compressor_test.go

@@ -170,13 +170,13 @@ func benchmarkDecompressCellblocks(b *testing.B, blockLen int, blocksCount int)
 	b.ReportAllocs()
 
 	data := make([]byte, blockLen)
-	rand.Seed(int64(b.N))
+	r := rand.New(rand.NewSource(42))
 
 	c := &compressor{Codec: mockCodec{}}
 
 	var compressedCellblocks []byte
 	for i := 0; i < blocksCount; i++ {
-		_, err := rand.Read(data)
+		_, err := r.Read(data)
 		if err != nil {
 			b.FailNow()
 		}