dlog token driver: improve the use of mathlib #1287 #1288
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,41 @@ | ||
| /* | ||
| Copyright IBM Corp. All Rights Reserved. | ||
| SPDX-License-Identifier: Apache-2.0 | ||
| */ | ||
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| package crypto | ||
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| import "encoding/binary" | ||
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| // AppendFixed32 appends slices prefixed with a 4-byte Little Endian length. | ||
|
Contributor
There was a problem hiding this comment. Little Endian this means that we support only x86 not power/z deployments? |
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| // Format: [Len(4 bytes)][Data]... | ||
| func AppendFixed32(dst []byte, s [][]byte) []byte { | ||
| // 1. Precise Size Calculation | ||
| // We calculate the exact total growth needed (4 bytes header + data length per slice). | ||
| // This allows us to perform exactly one allocation. | ||
| const headerSize = 4 | ||
| n := 0 | ||
| for _, v := range s { | ||
| n += headerSize + len(v) | ||
| } | ||
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| // 2. Single Growth / Allocation | ||
| // If the capacity is insufficient, we grow the slice exactly once. | ||
| // This avoids the 2x growth strategy of standard append(), saving | ||
| // potentially 25-50% memory overhead on large buffers. | ||
| if cap(dst)-len(dst) < n { | ||
| newDst := make([]byte, len(dst), len(dst)+n) | ||
| copy(newDst, dst) | ||
| dst = newDst | ||
| } | ||
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| // 3. Append Loop (Branch-free) | ||
| for _, v := range s { | ||
| // AppendUint32 is inlinable and highly optimized in Go 1.19+ [web:22] | ||
| dst = binary.LittleEndian.AppendUint32(dst, uint32(len(v))) | ||
| dst = append(dst, v...) | ||
| } | ||
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| return dst | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,120 @@ | ||
| /* | ||
| Copyright IBM Corp. All Rights Reserved. | ||
| SPDX-License-Identifier: Apache-2.0 | ||
| */ | ||
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| package crypto | ||
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| import ( | ||
| "bytes" | ||
| "encoding/binary" | ||
| "testing" | ||
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| "github.com/stretchr/testify/assert" | ||
| ) | ||
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| // Unit Test: Verifies correct Little Endian encoding and data integrity | ||
| func TestAppendFixed32(t *testing.T) { | ||
| tests := []struct { | ||
| name string | ||
| input [][]byte | ||
| expected []byte | ||
| }{ | ||
| { | ||
| name: "Basic Join", | ||
| input: [][]byte{ | ||
| []byte("Go"), | ||
| []byte("Lang"), | ||
| }, | ||
| // Expect: [Len:2][G][o] [Len:4][L][a][n][g] | ||
| // Little Endian 2: 0x02, 0x00, 0x00, 0x00 | ||
| expected: []byte{ | ||
| 0x02, 0x00, 0x00, 0x00, 'G', 'o', | ||
| 0x04, 0x00, 0x00, 0x00, 'L', 'a', 'n', 'g', | ||
| }, | ||
| }, | ||
| { | ||
| name: "Empty Input", | ||
| input: [][]byte{}, | ||
| expected: nil, // Or empty slice depending on init | ||
| }, | ||
| { | ||
| name: "Contains Empty Slice", | ||
| input: [][]byte{ | ||
| []byte("Hi"), | ||
| {}, | ||
| }, | ||
| // Expect: [Len:2][H][i] [Len:0] | ||
| expected: []byte{ | ||
| 0x02, 0x00, 0x00, 0x00, 'H', 'i', | ||
| 0x00, 0x00, 0x00, 0x00, | ||
| }, | ||
| }, | ||
| } | ||
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| for _, tt := range tests { | ||
| t.Run(tt.name, func(t *testing.T) { | ||
| // Using nil as dst to force new allocation | ||
| result := AppendFixed32(nil, tt.input) | ||
| assert.Equal(t, tt.expected, result) | ||
| }) | ||
| } | ||
| } | ||
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| // Verification Test: Reusing an existing buffer | ||
| func TestAppendFixed32_ReuseBuffer(t *testing.T) { | ||
| buffer := make([]byte, 0, 1024) | ||
| buffer = append(buffer, 0xFF) // Simulating existing data (dirty buffer) | ||
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| input := [][]byte{[]byte("A")} | ||
| result := AppendFixed32(buffer, input) | ||
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| // Check that we didn't lose the prefix 0xFF | ||
| assert.Equal(t, byte(0xFF), result[0]) | ||
| // Check the new data starts at index 1 | ||
| // Len: 1 (0x01 00 00 00) + 'A' | ||
| expectedPayload := []byte{0x01, 0x00, 0x00, 0x00, 'A'} | ||
| assert.Equal(t, expectedPayload, result[1:]) | ||
| } | ||
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| // --- Benchmarks --- | ||
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| // Setup helper for benchmarks | ||
| func generateBenchmarkData(count, size int) [][]byte { | ||
| data := make([][]byte, count) | ||
| for i := 0; i < count; i++ { | ||
| data[i] = bytes.Repeat([]byte{'a'}, size) | ||
| } | ||
| return data | ||
| } | ||
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| // Optimized Approach | ||
| func BenchmarkAppendFixed32(b *testing.B) { | ||
| // Scenario: 1000 items, 256 bytes each (~250KB total) | ||
| data := generateBenchmarkData(1000, 256) | ||
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| b.ReportAllocs() | ||
| b.ResetTimer() | ||
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| for i := 0; i < b.N; i++ { | ||
| // Use nil to strictly measure allocation of the result | ||
| _ = AppendFixed32(nil, data) | ||
| } | ||
| } | ||
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| // Comparison: Naive Loop (No pre-calculation) | ||
| func BenchmarkAppendFixed32_Naive(b *testing.B) { | ||
|
Contributor
There was a problem hiding this comment. Could you please add doc to this one? |
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| data := generateBenchmarkData(1000, 256) | ||
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| b.ReportAllocs() | ||
| b.ResetTimer() | ||
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| for i := 0; i < b.N; i++ { | ||
| var dst []byte | ||
| for _, v := range data { | ||
| dst = binary.LittleEndian.AppendUint32(dst, uint32(len(v))) | ||
| dst = append(dst, v...) | ||
| } | ||
| } | ||
| } | ||
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Is that something that we need to tune during testing? or does this fix? (does it worth to have it in config file)?