Function write_incremental_file

tools/comdb2ar/serialise.cpp:1518–1630

extern uint32_t myflip(uint32_t in);

void write_incremental_file (
        const std::string &dbdir, 
        const std::string &abspath, 
        const std::string &incrname, 
        struct stat *st
) 
// Write checksum/LSN information for a database file
{
    DB_Wrap db(abspath);
    int flags = O_RDONLY; 
    size_t pagesize;
    int fd;

    RIIA_fd fd_guard(fd);

    // TODO: optionally O_DIRECT?
    fd = open(abspath.c_str(), flags);
    if (fd == -1) {
        std::ostringstream ss;
        ss << "Can't open" << abspath << " " << strerror(errno) << std::endl;
        throw SerialiseError(abspath, ss.str());
    }

    pagesize = db.get_pagesize();
    if (pagesize == 0)
        pagesize = 4096;
    size_t bufsize = pagesize;
    while((bufsize << 1) <= MAX_BUF_SIZE) {
        bufsize <<= 1;
    }
    off_t uptosize = st->st_size;

    // st->st_size is going to be the size of the incremental file
    // save the size of the real file here
    // 12 bytes per page
    st->st_size = 12 * (st->st_size / pagesize);

    TarHeader head;
    head.set_filename(incrname);
    head.set_attrs(*st);
    head.set_checksum();
    tar_block_header hdr = head.get();

    // Write tar header
    if (writeall(1, &hdr, sizeof(tar_block_header)) != sizeof(tar_block_header)) {
        std::ostringstream ss;
        ss << "error writing tar block header: " << std::strerror(errno);
        throw Error(ss.str());
    }

    uint8_t *pagebuf = NULL;
    off_t bytesleft = uptosize;
    unsigned long long pageno = 0;
    off_t offset = 0;

#if ! defined  ( _SUN_SOURCE ) && ! defined ( _HP_SOURCE )
    if(posix_memalign((void**) &pagebuf, 512, bufsize))
        throw Error("Failed to allocate output buffer");