Bottle源码阅读（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) #注意这里使用title函数，它能将每个单词的开头大写
    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) #注意这里使用了递归
        elif key in self:
            if isinstance(self[key], list):
                self[key].append(value)
            else:
                self[key] = [self[key], value]
        else:
          self[key] = [value]

HeaderDict封装了dict，并将字典的键的单词的首字母进行大写。并且将value变成一个可迭代的对象，将value变成一个list对象，即value=[value]。WSGI标准中定义了要将一个字符串类型转换成list类型，这样会使其有更好的表现形式。server也可以不用一次全部输出可以用yield进行控制输出，以免一次输出过多。总而言之，这个封装了dict的类就实现了两个功能：

1. 将value转换为list，优化数据表现形式
2. 将key中单词的首字母大写

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)
    #判断文件是否可获得
    if not filename.startswith(root): #主目录下的文件不可以下载
        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.")
    # 获得文件类型
    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
    #设置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'))

上面的三个函数分别实现了，服务器内部错误、重定向、以及文件下载。文件下载这个函数实现了，文件类型的判断，Content_type的设置、文件权限的判断、文件状态的获得等。这个函数还是很简单，可以做定制。