package main

import (
    "bytes"
    "compress/gzip"
    "fmt"
    "log"
)

// CompressData compresses a byte slice into a bytes.Buffer using gzip.
func CompressData(data []byte) (*bytes.Buffer, error) {
    var b bytes.Buffer // 創(chuàng)建一個內(nèi)存緩沖區(qū)，用于存儲壓縮后的數(shù)據(jù)
    w := gzip.NewWriter(&b) // 創(chuàng)建一個gzip寫入器，將壓縮數(shù)據(jù)寫入b

    // 將原始數(shù)據(jù)寫入gzip寫入器
    _, err := w.Write(data)
    if err != nil {
        return nil, fmt.Errorf("failed to write data to gzip writer: %w", err)
    }

    // 關(guān)閉gzip寫入器。這一步非常重要，它會刷新所有緩沖區(qū)，
    // 并寫入gzip文件尾部信息，確保壓縮數(shù)據(jù)的完整性。
    err = w.Close()
    if err != nil {
        return nil, fmt.Errorf("failed to close gzip writer: %w", err)
    }

    return &b, nil
}

func main() {
    originalData := []byte("hello, world\nThis is a test string for gzip compression.")
    fmt.Printf("Original data size: %d bytes\n", len(originalData))

    compressedBuffer, err := CompressData(originalData)
    if err != nil {
        log.Fatalf("Error compressing data: %v", err)
    }

    fmt.Printf("Compressed data size: %d bytes\n", compressedBuffer.Len())
    // fmt.Printf("Compressed data (hex): %x\n", compressedBuffer.Bytes()) // 可以打印查看壓縮后的字節(jié)
}

package main

import (
    "bytes"
    "compress/gzip"
    "fmt"
    "io"
    "log"
    "os"
)

// DecompressData decompresses data from a bytes.Buffer.
func DecompressData(compressedBuffer *bytes.Buffer) (*bytes.Buffer, error) {
    r, err := gzip.NewReader(compressedBuffer) // 創(chuàng)建一個gzip讀取器，從compressedBuffer中讀取壓縮數(shù)據(jù)
    if err != nil {
        return nil, fmt.Errorf("failed to create gzip reader: %w", err)
    }
    defer r.Close() // 確保在函數(shù)退出時關(guān)閉gzip讀取器，釋放資源

    var decompressedBuffer bytes.Buffer // 創(chuàng)建一個內(nèi)存緩沖區(qū)，用于存儲解壓后的數(shù)據(jù)
    _, err = io.Copy(&decompressedBuffer, r) // 將解壓后的數(shù)據(jù)從r復(fù)制到decompressedBuffer
    if err != nil {
        return nil, fmt.Errorf("failed to copy decompressed data: %w", err)
    }

    return &decompressedBuffer, nil
}

func main() {
    originalData := []byte("hello, world\nThis is a test string for gzip compression.")
    fmt.Printf("Original data size: %d bytes\n", len(originalData))

    // 壓縮數(shù)據(jù)
    compressedBuffer, err := CompressData(originalData)
    if err != nil {
        log.Fatalf("Error compressing data: %v", err)
    }
    fmt.Printf("Compressed data size: %d bytes\n", compressedBuffer.Len())

    // 解壓數(shù)據(jù)
    decompressedBuffer, err := DecompressData(compressedBuffer)
    if err != nil {
        log.Fatalf("Error decompressing data: %v", err)
    }

    fmt.Printf("Decompressed data size: %d bytes\n", decompressedBuffer.Len())
    fmt.Println("Decompressed content:")
    fmt.Println(decompressedBuffer.String())

    // 驗證解壓后的數(shù)據(jù)是否與原始數(shù)據(jù)一致
    if bytes.Equal(originalData, decompressedBuffer.Bytes()) {
        fmt.Println("Decompression successful: Data matches original.")
    } else {
        fmt.Println("Decompression failed: Data does not match original.")
    }
}

// CompressData function from previous section (included here for completeness if running separately)
func CompressData(data []byte) (*bytes.Buffer, error) {
    var b bytes.Buffer
    w := gzip.NewWriter(&b)
    _, err := w.Write(data)
    if err != nil {
        return nil, fmt.Errorf("failed to write data to gzip writer: %w", err)
    }
    err = w.Close()
    if err != nil {
        return nil, fmt.Errorf("failed to close gzip writer: %w", err)
    }
    return &b, nil
}

package main

import (
    "compress/gzip"
    "fmt"
    "io"
    "log"
    "os"
)

// CompressFile compresses the source file to a gzipped destination file.
func CompressFile(sourcePath, destPath string) error {
    // 打開源文件進行讀取
    sourceFile, err := os.Open(sourcePath)
    if err != nil {
        return fmt.Errorf("failed to open source file: %w", err)
    }
    defer sourceFile.Close()

    // 創(chuàng)建目標(biāo)gzip文件進行寫入
    destFile, err := os.Create(destPath)
    if err != nil {
        return fmt.Errorf("failed to create destination file: %w", err)
    }
    defer destFile.Close()

    // 創(chuàng)建gzip寫入器，將壓縮數(shù)據(jù)寫入destFile
    gzipWriter := gzip.NewWriter(destFile)
    defer gzipWriter.Close() // 確保關(guān)閉gzip寫入器

    // 將源文件內(nèi)容復(fù)制到gzip寫入器，實現(xiàn)壓縮
    _, err = io.Copy(gzipWriter, sourceFile)
    if err != nil {
        return fmt.Errorf("failed to copy data to gzip writer: %w", err)
    }

    fmt.Printf("File '%s' compressed to '%s' successfully.\n", sourcePath, destPath)
    return nil
}

// main function to demonstrate file compression
func main() {
    // 創(chuàng)建一個示例文件
    err := os.WriteFile("source.txt", []byte("This is some content to be compressed into a file.\nAnother line of text."), 0644)
    if err != nil {
        log.Fatalf("Failed to create source file: %v", err)
    }
    fmt.Println("Created source.txt")

    // 壓縮文件
    err = CompressFile("source.txt", "destination.txt.gz")
    if err != nil {
        log.Fatalf("Error compressing file: %v", err)
    }
}

package main

import (
    "compress/gzip"
    "fmt"
    "io"
    "log"
    "os"
)

// DecompressFile decompresses a gzipped source file to a plain destination file.
func DecompressFile(sourcePath, destPath string) error {
    // 打開源gzip文件進行讀取
    sourceFile, err := os.Open(sourcePath)
    if err != nil {
        return fmt.Errorf("failed to open source gzip file: %w", err)
    }
    defer sourceFile.Close()

    // 創(chuàng)建gzip讀取器，從sourceFile中讀取壓縮數(shù)據(jù)
    gzipReader, err := gzip.NewReader(sourceFile)
    if err != nil {
        return fmt.Errorf("failed to create gzip reader: %w", err)
    }
    defer gzipReader.Close() // 確保關(guān)閉gzip讀取器

    // 創(chuàng)建目標(biāo)文件進行寫入
    destFile, err := os.Create(destPath)
    if err != nil {
        return fmt.Errorf("failed to create destination file: %w", err)
    }
    defer destFile.Close()

    // 將解壓后的數(shù)據(jù)從gzip讀取器復(fù)制到目標(biāo)文件
    _, err = io.Copy(destFile, gzipReader)
    if err != nil {
        return fmt.Errorf("failed to copy decompressed data: %w", err)
    }

    fmt.Printf("File '%s' decompressed to '%s' successfully.\n", sourcePath, destPath)
    return nil
}

// main function to demonstrate file decompression
func main() {
    // 假設(shè) "destination.txt.gz" 已經(jīng)存在 (由上面的CompressFile創(chuàng)建)
    // 如果沒有，可以先運行上面的CompressFile示例來生成它

    // 解壓文件
    err := DecompressFile("destination.txt.gz", "decompressed.txt")
    if err != nil {
        log.Fatalf("Error decompressing file: %v", err)
    }

    // 驗證解壓后的文件內(nèi)容
    content, err := os.ReadFile("decompressed.txt")
    if err != nil {
        log.Fatalf("Failed to read decompressed file: %v", err)
    }
    fmt.Println("Content of decompressed.txt:")
    fmt.Println(string(content))
}