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| //go:build generate
| // +build generate
|
| package main
|
| import (
| "fmt"
| "log"
| "os"
| )
|
| func writeQuarterRound(file *os.File, a, b, c, d int) {
| add := "x%d+=x%d\n"
| xor := "x=x%d^x%d\n"
| rotate := "x%d=(x << %d) | (x >> (32 - %d))\n"
|
| fmt.Fprintf(file, add, a, b)
| fmt.Fprintf(file, xor, d, a)
| fmt.Fprintf(file, rotate, d, 16, 16)
|
| fmt.Fprintf(file, add, c, d)
| fmt.Fprintf(file, xor, b, c)
| fmt.Fprintf(file, rotate, b, 12, 12)
|
| fmt.Fprintf(file, add, a, b)
| fmt.Fprintf(file, xor, d, a)
| fmt.Fprintf(file, rotate, d, 8, 8)
|
| fmt.Fprintf(file, add, c, d)
| fmt.Fprintf(file, xor, b, c)
| fmt.Fprintf(file, rotate, b, 7, 7)
| }
|
| func writeChacha20Block(file *os.File) {
| fmt.Fprintln(file, `
| func ChaCha20Block(s *[16]uint32, out []byte, rounds int) {
| var x0,x1,x2,x3,x4,x5,x6,x7,x8,x9,x10,x11,x12,x13,x14,x15 = s[0],s[1],s[2],s[3],s[4],s[5],s[6],s[7],s[8],s[9],s[10],s[11],s[12],s[13],s[14],s[15]
| for i := 0; i < rounds; i+=2 {
| var x uint32
| `)
|
| writeQuarterRound(file, 0, 4, 8, 12)
| writeQuarterRound(file, 1, 5, 9, 13)
| writeQuarterRound(file, 2, 6, 10, 14)
| writeQuarterRound(file, 3, 7, 11, 15)
| writeQuarterRound(file, 0, 5, 10, 15)
| writeQuarterRound(file, 1, 6, 11, 12)
| writeQuarterRound(file, 2, 7, 8, 13)
| writeQuarterRound(file, 3, 4, 9, 14)
| fmt.Fprintln(file, "}")
| for i := 0; i < 16; i++ {
| fmt.Fprintf(file, "binary.LittleEndian.PutUint32(out[%d:%d], s[%d]+x%d)\n", i*4, i*4+4, i, i)
| }
| fmt.Fprintln(file, "}")
| fmt.Fprintln(file)
| }
|
| func main() {
| file, err := os.OpenFile("chacha_core.generated.go", os.O_WRONLY|os.O_TRUNC|os.O_CREATE, 0o644)
| if err != nil {
| log.Fatalf("Failed to generate chacha_core.go: %v", err)
| }
| defer file.Close()
|
| fmt.Fprintln(file, "package internal")
| fmt.Fprintln(file)
| fmt.Fprintln(file, "import \"encoding/binary\"")
| fmt.Fprintln(file)
| writeChacha20Block(file)
| }
|
|
