From e671fe0c3efc497397af3362a4b79c895fbd8bfc Mon Sep 17 00:00:00 2001 From: Joe Tsai Date: Mon, 6 Feb 2023 11:37:39 -0800 Subject: bytes: add Buffer.Available and Buffer.AvailableBuffer MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This adds a new Buffer.AvailableBuffer method that returns an empty buffer with a possibly non-empty capacity for use with append-like APIs. The typical usage pattern is something like: b := bb.AvailableBuffer() b = appendValue(b, v) bb.Write(b) It allows logic combining append-like APIs with Buffer to avoid needing to allocate and manage buffers themselves and allows the append-like APIs to directly write into the Buffer. The Buffer.Write method uses the builtin copy function, which avoids copying bytes if the source and destination are identical. Thus, Buffer.Write is a constant-time call for this pattern. Performance: BenchmarkBufferAppendNoCopy 2.909 ns/op 5766942167.24 MB/s This benchmark should only be testing the cost of bookkeeping and never the copying of the input slice. Thus, the MB/s should be orders of magnitude faster than RAM. Fixes #53685 Change-Id: I0b41e54361339df309db8d03527689b123f99085 Reviewed-on: https://go-review.googlesource.com/c/go/+/474635 Run-TryBot: Joseph Tsai Reviewed-by: Daniel Martí Reviewed-by: Cherry Mui TryBot-Result: Gopher Robot Auto-Submit: Joseph Tsai Reviewed-by: Ian Lance Taylor --- src/bytes/example_test.go | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'src/bytes/example_test.go') diff --git a/src/bytes/example_test.go b/src/bytes/example_test.go index e5b7b60dbb..41a5e2e5bf 100644 --- a/src/bytes/example_test.go +++ b/src/bytes/example_test.go @@ -11,6 +11,7 @@ import ( "io" "os" "sort" + "strconv" "unicode" ) @@ -37,6 +38,18 @@ func ExampleBuffer_Bytes() { // Output: hello world } +func ExampleBuffer_AvailableBuffer() { + var buf bytes.Buffer + for i := 0; i < 4; i++ { + b := buf.AvailableBuffer() + b = strconv.AppendInt(b, int64(i), 10) + b = append(b, ' ') + buf.Write(b) + } + os.Stdout.Write(buf.Bytes()) + // Output: 0 1 2 3 +} + func ExampleBuffer_Cap() { buf1 := bytes.NewBuffer(make([]byte, 10)) buf2 := bytes.NewBuffer(make([]byte, 0, 10)) -- cgit v1.3