Go语言中Base64编码与解码的正确实践

package main

import (
    "encoding/base64"
    "fmt"
)

// EncodeB64 encodes a string to its Base64 representation.
func EncodeB64(message string) string {
    // Convert the input string to a byte slice before encoding.
    encodedText := base64.StdEncoding.EncodeToString([]byte(message))
    return encodedText
}

func main() {
    originalMessage := "Hello, playground"
    encodedMessage := EncodeB64(originalMessage)
    fmt.Printf("Original: %s\n", originalMessage)
    fmt.Printf("Encoded: %s\n", encodedMessage)
    // Output: SGVsbG8sIHBsYXlncm91bmQ=
}

package main

import (
    "encoding/base64"
    "fmt"
    "log"
)

// DecodeB64 decodes a Base64 string back to its original string representation.
func DecodeB64(encodedMessage string) (string, error) {
    // Decode the Base64 string to a byte slice.
    decodedBytes, err := base64.StdEncoding.DecodeString(encodedMessage)
    if err != nil {
        return "", fmt.Errorf("Base64 decoding error: %w", err)
    }
    // Convert the decoded byte slice back to a string.
    return string(decodedBytes), nil
}

func main() {
    encodedMessage := "SGVsbG8sIHBsYXlncm91bmQ="
    decodedMessage, err := DecodeB64(encodedMessage)
    if err != nil {
        log.Fatalf("Failed to decode: %v", err)
    }
    fmt.Printf("Encoded: %s\n", encodedMessage)
    fmt.Printf("Decoded: %s\n", decodedMessage)
    // Output: Hello, playground
}

// 原始问题中的错误示例
func DecodeB64Incorrect(message string) (retour string) {
    // base64.StdEncoding.DecodedLen(len(message)) 计算的是最大可能解码长度
    // 但实际解码的字节数可能小于此值。
    base64Text := make([]byte, base64.StdEncoding.DecodedLen(len(message)))

    // Decode 函数返回写入的字节数 n 和错误 err。
    // 如果没有错误，n 是实际解码的字节数。
    // 此处直接将整个 base64Text 转换为字符串，
    // 如果 n 小于 len(base64Text)，则 base64Text 中会包含多余的零值字节。
    // 将包含零值字节的切片直接转换为字符串，可能导致无效的UTF-8序列。
    _, _ = base64.StdEncoding.Decode(base64Text, []byte(message)) 
    // fmt.Printf("base64: %s\n", base64Text) // 打印时可能已出现问题
    return string(base64Text) // 错误源头：未根据实际写入长度截取切片
}

package main

import (
    "encoding/base64"
    "fmt"
    "log"
)

// DecodeB64CorrectlyWithDecode decodes a Base64 string using the Decode function,
// correctly handling the output buffer.
func DecodeB64CorrectlyWithDecode(encodedMessage string) (string, error) {
    // Allocate a buffer large enough to hold the maximum possible decoded data.
    // This is often slightly oversized, but safe.
    decodedBytesBuffer := make([]byte, base64.StdEncoding.DecodedLen(len(encodedMessage)))

    // Perform the decoding. 'n' will be the actual number of bytes written.
    n, err := base64.StdEncoding.Decode(decodedBytesBuffer, []byte(encodedMessage))
    if err != nil {
        return "", fmt.Errorf("Base64 decoding error: %w", err)
    }

    // Crucial step: Slice the buffer to only include the actual decoded bytes (up to n).
    // Then convert this valid portion to a string.
    return string(decodedBytesBuffer[:n]), nil
}

func main() {
    encodedMessage := "SGVsbG8sIHBsYXlncm91bmQ="
    decodedMessage, err := DecodeB64CorrectlyWithDecode(encodedMessage)
    if err != nil {
        log.Fatalf("Failed to decode: %v", err)
    }
    fmt.Printf("Encoded: %s\n", encodedMessage)
    fmt.Printf("Decoded (using Decode func): %s\n", decodedMessage)
    // Output: Hello, playground
}

package main

import (
    "encoding/base64"
    "fmt"
    "log"
)

// EncodeToStringB64 encodes a string to its Base64 representation using EncodeToString.
func EncodeToStringB64(message string) string {
    return base64.StdEncoding.EncodeToString([]byte(message))
}

// DecodeStringB64 decodes a Base64 string back to its original string representation using DecodeString.
func DecodeStringB64(encodedMessage string) (string, error) {
    decodedBytes, err := base64.StdEncoding.DecodeString(encodedMessage)
    if err != nil {
        return "", fmt.Errorf("Base64 decoding error: %w", err)
    }
    return string(decodedBytes), nil
}

func main() {
    originalData := "Go语言Base64编码教程"
    fmt.Printf("原始数据: %s\n", originalData)

    // 编码
    encodedData := EncodeToStringB64(originalData)
    fmt.Printf("Base64编码: %s\n", encodedData)

    // 解码
    decodedData, err := DecodeStringB64(encodedData)
    if err != nil {
        log.Fatalf("解码失败: %v", err)
    }
    fmt.Printf("Base64解码: %s\n", decodedData)

    // 验证解码结果
    if originalData == decodedData {
        fmt.Println("编码与解码结果一致。")
    } else {
        fmt.Println("编码与解码结果不一致！")
    }

    // 演示使用Decode函数（需要注意截取）
    fmt.Println("\n--- 演示使用Decode函数 ---")
    encodedMessageForDecode := "SGVsbG8sIHBsYXlncm91bmQ="
    decodedBytesBuffer := make([]byte, base64.StdEncoding.DecodedLen(len(encodedMessageForDecode)))
    n, err := base64.StdEncoding.Decode(decodedBytesBuffer, []byte(encodedMessageForDecode))
    if err != nil {
        log.Fatalf("使用Decode函数解码失败: %v", err)
    }
    fmt.Printf("使用Decode函数解码: %s\n", string(decodedBytesBuffer[:n]))
}