FreeBSD下实现文件压缩和解压缩的示例代码及技术解答

这个示例展示了在FreeBSD操作系统上使用libarchive库实现文件的压缩和解压缩。通过该示例，可以了解如何利用libarchive提供的功能对文件进行打包压缩和解压操作。

#include <archive.h>
#include <archive_entry.h>

int compress_file(const char *filename) {
    struct archive *a;
    struct archive_entry *entry;

    a = archive_write_new();
    archive_write_add_filter_gzip(a);
    archive_write_set_format_ustar(a);
    archive_write_open_filename(a, "compressed_file.tar.gz");

    entry = archive_entry_new();
    archive_entry_set_pathname(entry, filename);
    archive_entry_set_size(entry, file_size(filename));

    archive_write_header(a, entry);

    int file = open(filename, O_RDONLY);
    char buff[8192];
    ssize_t len = read(file, buff, sizeof(buff));
    while (len > 0) {
        archive_write_data(a, buff, len);
        len = read(file, buff, sizeof(buff));
    }

    close(file);
    archive_entry_free(entry);
    archive_write_free(a);

    return 0;
}

int decompress_file(const char *filename) {
    struct archive *a;
    struct archive_entry *entry;

    a = archive_read_new();
    archive_read_support_filter_all(a);
    archive_read_support_format_all(a);

    archive_read_open_filename(a, filename, 10240);

    int r = archive_read_next_header(a, &entry);
    if (r != ARCHIVE_OK) {
        return 1;
    }

    int file = open(archive_entry_pathname(entry), O_CREAT | O_WRONLY, 0644);
    char buff[8192];
    ssize_t len = archive_read_data(a, buff, sizeof(buff));
    while (len > 0) {
        write(file, buff, len);
        len = archive_read_data(a, buff, sizeof(buff));
    }

    close(file);
    archive_read_close(a);
    archive_read_free(a);

    return 0;
}

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