Bottle源碼閱讀（3） HeaderDict

class HeaderDict(dict):
    ''' A dictionary with case insensitive (titled) keys.
    
    You may add a list of strings to send multible headers with the same name.'''
    def __setitem__(self, key, value):
        return dict.__setitem__(self,key.title(), value) #註意這裡使用title函數，它能將每個單詞的開頭大寫
    def __getitem__(self, key):
        return dict.__getitem__(self,key.title())
    def __delitem__(self, key):
        return dict.__delitem__(self,key.title())
    def __contains__(self, key):
        return dict.__contains__(self,key.title())

    def items(self):
        """ Returns a list of (key, value) tuples """
        for key, values in dict.items(self):
            if not isinstance(values, list):
                values = [values]
            for value in values:
                yield (key, str(value))
                
    def add(self, key, value):
        """ Adds a new header without deleting old ones """
        if isinstance(value, list):
            for v in value:
                self.add(key, v) #註意這裡使用了遞歸
        elif key in self:
            if isinstance(self[key], list):
                self[key].append(value)
            else:
                self[key] = [self[key], value]
        else:
          self[key] = [value]

HeaderDict封裝了dict，並將字典的鍵的單詞的首字母進行大寫。並且將value變成一個可迭代的對象，將value變成一個list對象，即value=[value]。WSGI標準中定義了要將一個字元串類型轉換成list類型，這樣會使其有更好的表現形式。server也可以不用一次全部輸出可以用yield進行控制輸出，以免一次輸出過多。總而言之，這個封裝了dict的類就實現了兩個功能：

1. 將value轉換為list，優化數據表現形式
2. 將key中單詞的首字母大寫

def abort(code=500, text='Unknown Error: Appliction stopped.'):
    """ Aborts execution and causes a HTTP error. """
    raise HTTPError(code, text)


def redirect(url, code=307):
    """ Aborts execution and causes a 307 redirect """
    response.status = code
    response.header['Location'] = url
    raise BreakTheBottle("")


def send_file(filename, root, guessmime = True, mimetype = 'text/plain'):
    """ Aborts execution and sends a static files as response. """
    root = os.path.abspath(root) + '/'
    filename = os.path.normpath(filename).strip('/')
    filename = os.path.join(root, filename)
    #判斷文件是否可獲得
    if not filename.startswith(root): #主目錄下的文件不可以下載
        abort(401, "Access denied.")
    if not os.path.exists(filename) or not os.path.isfile(filename):
        abort(404, "File does not exist.")
    if not os.access(filename, os.R_OK):
        abort(401, "You do not have permission to access this file.")
    # 獲得文件類型
    if guessmime:
        guess = mimetypes.guess_type(filename)[0]
        if guess:
            response.content_type = guess
        elif mimetype:
            response.content_type = mimetype
    elif mimetype:
        response.content_type = mimetype
    #設置Content_type
    stats = os.stat(filename)
    # TODO: HTTP_IF_MODIFIED_SINCE -> 304 (Thu, 02 Jul 2009 23:16:31 CEST)
    if 'Content-Length' not in response.header:
        response.header['Content-Length'] = stats.st_size
    if 'Last-Modified' not in response.header:
        ts = time.gmtime(stats.st_mtime)
        ts = time.strftime("%a, %d %b %Y %H:%M:%S +0000", ts)
        response.header['Last-Modified'] = ts

    raise BreakTheBottle(open(filename, 'r'))

上面的三個函數分別實現了，伺服器內部錯誤、重定向、以及文件下載。文件下載這個函數實現了，文件類型的判斷，Content_type的設置、文件許可權的判斷、文件狀態的獲得等。這個函數還是很簡單，可以做定製。