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在包golang.org/x/crypto/nacl/sign中，Sign函数有一个out []byte参数，它返回一个字节切片。

阅读源代码，我正在努力弄清楚如何正确使用它们，它们是头部和尾部，尽管在下面的示例中，生成的字节切片为零 len。

请看下面的例子，


package main

import (
    "crypto/rand"
    "encoding/base64"
    "fmt"

    "golang.org/x/crypto/nacl/sign"
)

func main() {
    _, priv, err := sign.GenerateKey(rand.Reader)
    if err != nil {
        panic(err)
    }
    msg := []byte("hello world!")
    out := make([]byte, 0, len(msg)+sign.Overhead)
    ret := sign.Sign(out, msg, priv)

    fmt.Printf("len(msg): %v %s\n", len(msg), msg)
    fmt.Printf("len(out): %v %v\n", len(out), base64.StdEncoding.EncodeToString(out))
    fmt.Printf("len(ret): %v %v\n", len(ret), base64.StdEncoding.EncodeToString(ret))
}
// Output:
// len(msg): 12 hello world!
// len(out): 0 
// len(ret): 76 h+ZkFoWxuxOj7zV3tekiQz/z/yfuvXNUHxBjklo4iGBy7PfCEwvAiy3gi7GnuYGWB3SMxuxHtV5tNuUL1b3kAGhlbGxvIHdvcmxkIQ==

我不明白为什么 Sign 会同时返回和返回。我不确定要签署.Sign 的输出缓冲区应该多长时间。

相反，这个例子有效，但它是否正确？

package main

import (
    "crypto/rand"
    "encoding/base64"
    "fmt"

    "golang.org/x/crypto/nacl/sign"
)

func main() {
    pub, priv, err := sign.GenerateKey(rand.Reader)
    if err != nil {
        panic(err)
    }
    msg := []byte("hello world!")
    out := make([]byte, 0, len(msg)+sign.Overhead)
    ret := sign.Sign(out, msg, priv)

    fmt.Printf("len(msg): %v %s\n", len(msg), msg)
    fmt.Printf("len(out): %v %v\n", len(out), base64.StdEncoding.EncodeToString(out))
    fmt.Printf("len(ret): %v %v\n", len(ret), base64.StdEncoding.EncodeToString(ret))

    openOut := make([]byte, 0, len(ret)-sign.Overhead)
    res, ok := sign.Open(openOut, ret, pub)
    if !ok {
        panic("failed to open signed message")
    }
    fmt.Printf("len(res): %v %s\n", len(res), res)
}
// Output:
// len(msg): 12 hello world!
// len(out): 0 
// len(ret): 76 h+ZkFoWxuxOj7zV3tekiQz/z/yfuvXNUHxBjklo4iGBy7PfCEwvAiy3gi7GnuYGWB3SMxuxHtV5tNuUL1b3kAGhlbGxvIHdvcmxkIQ==
// len(res): 12 hello world!

期待一些解释和正确性帮助。

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