文章标题

apache运行时文件读写注释

1. apr_file_t的结构使用

struct apr_file_t {    apr_pool_t *pool;//apache对应的内存池使用效果    int filedes;//文件描述符    char *fname;//文件名    apr_int32_t flags;//文件操作权限    int eof_hit;//是否到达文件尾    int is_pipe;//是否是管道文件    apr_interval_time_t timeout;//是否超时    int buffered;//是否是buffer    //是否阻塞    enum {BLK_UNKNOWN, BLK_OFF, BLK_ON } blocking;    int ungetchar;    /* Last char provided by an unget op. (-1 = no char)*/    /* if there is a timeout set, then this pollset is used */    apr_pollset_t *pollset;    /* Stuff for buffered mode */    char *buffer;    apr_size_t bufpos;    /* Read/Write position in buffer */    apr_size_t bufsize;   /* The buffer size */    apr_off_t dataRead;   /* amount of valid data read into buffer */    int direction;            /* buffer being used for 0 = read, 1 = write */    //文件偏移位置    apr_off_t filePtr;    /* position in file of handle */#if APR_HAS_THREADS    struct apr_thread_mutex_t *thlock;#endif};

2.关于文件的open函数注释

APR_DECLARE(apr_status_t) apr_file_open(apr_file_t **new,                                         const char *fname,                                         apr_int32_t flag,                                         apr_fileperms_t perm,                                         apr_pool_t *pool){    apr_os_file_t fd;    int oflags = 0;#if APR_HAS_THREADS //是否多线程环境    apr_thread_mutex_t *thlock;    apr_status_t rv;#endif    //可以读写    if ((flag & APR_FOPEN_READ) && (flag & APR_FOPEN_WRITE)) {        oflags = O_RDWR;    }    //只读    else if (flag & APR_FOPEN_READ) {        oflags = O_RDONLY;    }    //只写    else if (flag & APR_FOPEN_WRITE) {        oflags = O_WRONLY;    }    //其他    else {        return APR_EACCES;     }    //文件不存在第一次创建文件，如果文件有内存就删除    if (flag & APR_FOPEN_CREATE) {        oflags |= O_CREAT;        if (flag & APR_FOPEN_EXCL) {            oflags |= O_EXCL;        }    }    if ((flag & APR_FOPEN_EXCL) && !(flag & APR_FOPEN_CREATE)) {        return APR_EACCES;    }       //文件追加内容    if (flag & APR_FOPEN_APPEND) {        oflags |= O_APPEND;    }    //文件截断    if (flag & APR_FOPEN_TRUNCATE) {        oflags |= O_TRUNC;    }#ifdef O_BINARY    if (flag & APR_FOPEN_BINARY) {        oflags |= O_BINARY;    }#endif    if (flag & APR_FOPEN_NONBLOCK) {#ifdef O_NONBLOCK        oflags |= O_NONBLOCK;#else        return APR_ENOTIMPL;#endif    }#ifdef O_CLOEXEC    /* Introduced in Linux 2.6.23. Silently ignored on earlier Linux kernels.     */    if (!(flag & APR_FOPEN_NOCLEANUP)) {        oflags |= O_CLOEXEC;}#endif#if APR_HAS_LARGE_FILES && defined(_LARGEFILE64_SOURCE)    oflags |= O_LARGEFILE;#elif defined(O_LARGEFILE)    if (flag & APR_FOPEN_LARGEFILE) {        oflags |= O_LARGEFILE;    }#endif#if APR_HAS_THREADS    if ((flag & APR_FOPEN_BUFFERED) && (flag & APR_FOPEN_XTHREAD)) {        rv = apr_thread_mutex_create(&thlock,                                     APR_THREAD_MUTEX_DEFAULT, pool);        if (rv) {            return rv;        }    }#endif    if (perm == APR_OS_DEFAULT) {        fd = open(fname, oflags, 0666);    }    else {        fd = open(fname, oflags, apr_unix_perms2mode(perm));    }     if (fd < 0) {       return errno;    }    if (!(flag & APR_FOPEN_NOCLEANUP)) {#ifdef O_CLOEXEC        static int has_o_cloexec = 0;        if (!has_o_cloexec)#endif        {            int flags;            if ((flags = fcntl(fd, F_GETFD)) == -1) {                close(fd);                return errno;            }            if ((flags & FD_CLOEXEC) == 0) {                flags |= FD_CLOEXEC;                if (fcntl(fd, F_SETFD, flags) == -1) {                    close(fd);                    return errno;                }            }#ifdef O_CLOEXEC            else {                has_o_cloexec = 1;            }#endif        }    }    //创建file    //实例化文件对象    (*new) = (apr_file_t *)apr_pcalloc(pool, sizeof(apr_file_t));    (*new)->pool = pool;    (*new)->flags = flag;    (*new)->filedes = fd;    (*new)->fname = apr_pstrdup(pool, fname);    (*new)->blocking = BLK_ON;    (*new)->buffered = (flag & APR_FOPEN_BUFFERED) > 0;    if ((*new)->buffered) {        (*new)->buffer = apr_palloc(pool, APR_FILE_DEFAULT_BUFSIZE);        (*new)->bufsize = APR_FILE_DEFAULT_BUFSIZE;#if APR_HAS_THREADS        if ((*new)->flags & APR_FOPEN_XTHREAD) {            (*new)->thlock = thlock;        }#endif    }    else {        (*new)->buffer = NULL;    }    (*new)->is_pipe = 0;    (*new)->timeout = -1;    (*new)->ungetchar = -1;    (*new)->eof_hit = 0;    (*new)->filePtr = 0;    (*new)->bufpos = 0;    (*new)->dataRead = 0;    (*new)->direction = 0;#ifndef WAITIO_USES_POLL    /* Start out with no pollset.  apr_wait_for_io_or_timeout() will     * initialize the pollset if needed.     */    (*new)->pollset = NULL;#endif    if (!(flag & APR_FOPEN_NOCLEANUP)) {        apr_pool_cleanup_register((*new)->pool, (void *)(*new),                                   apr_unix_file_cleanup,                                   apr_unix_child_file_cleanup);    }    return APR_SUCCESS;}