Life in a Nutshell

Pelican自定义Jinja过滤器

使用Pelican的时候发现需要在模板中使用Hash函数，但是Jinja并没有提供Hash 过滤器，需要自己实现一个Hash过滤器，这里以Hash过滤器为例子讲讲如何在 Pelican中使用自定义过滤器。

Hash函数功能实现

通过Python的标准库函数实现一个md5的哈希函数，函数的功能的是传入一个字符串 返回该字符串的md5串，实现如下：

# (c) 2012-2014, Michael DeHaan <michael.dehaan@gmail.com>
#
# This file is part of Ansible
#
# Ansible is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Ansible is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.

# Make coding more python3-ish
from __future__ import (absolute_import, division, print_function)
__metaclass__ = type


# Note, sha1 is the only hash algorithm compatible with python2.4 and with
# FIPS-140 mode (as of 11-2014)
try:
    from hashlib import sha1 as sha1
except ImportError:
    from sha import sha as sha1

# Backwards compat only
try:
    from hashlib import md5 as _md5
except ImportError:
    try:
        from md5 import md5 as _md5
    except ImportError:
        # Assume we're running in FIPS mode here
        _md5 = None

def secure_hash_s(data, hash_func=sha1):
    ''' Return a secure hash hex digest of data. '''

    digest = hash_func()
    try:
        if not isinstance(data, basestring):
            data = "%s" % data
        digest.update(data)
    except UnicodeEncodeError:
        digest.update(data.encode('utf-8'))
    return digest.hexdigest()


# The checksum algorithm must match with the algorithm in ShellModule.checksum() method
checksum_s = secure_hash_s

# Backwards compat functions.  Some modules include md5s in their return values
# Continue to support that for now.  As of ansible-1.8, all of those modules
# should also return "checksum" (sha1 for now)
# Do not use md5 unless it is needed for:
# 1) Optional backwards compatibility
# 2) Compliance with a third party protocol
#
# MD5 will not work on systems which are FIPS-140-2 compliant.


def md5s(data):
    if not _md5:
        raise ValueError('MD5 not available.  Possibly running in FIPS mode')
    return secure_hash_s(data, _md5)

这里的md5s实现了我们需要的功能。

向Pelican注册Jinja过滤器

通过配置Pelican的配置文件pelicanconf.py注册过滤器的名字和对应的函数，如下：

# add customer filter
import os
import sys
sys.path.append(os.curdir)
from hashing import md5s as md5hash
JINJA_FILTERS = {
    "md5hash": md5hash
}

代码中注册了一个名字为md5hash的过滤器，并且对应的函数名字也叫md5hash。

在Jinja模板中使用自定义过滤器

下面的模板中通过文章的url产生一个唯一的key给多说插件使用 data-thread-key="{{ article.url|md5hash }}"

{%if DUOSHUO %}
<div class="row">
    <div class="alpha span9">
            <!-- 多说评论框 start -->
            <!--data-thread-key="的ID"-->
            <div class="ds-thread" data-thread-key="{{ article.url|md5hash }}" data-title="{{ article.title|striptags }}" data-url="{{article.url}}"></div>
            <!-- 多说评论框 end -->
            <!-- 多说公共JS代码 start (一个网页只需插入一次) -->
            <script type="text/javascript">
            var duoshuoQuery = {short_name:"{{DUOSHUO}}"};
                (function() {
                    var ds = document.createElement('script');
                    ds.type = 'text/javascript';ds.async = true;
                    ds.src = (document.location.protocol == 'https:' ? 'https:' : 'http:') + '//static.duoshuo.com/embed.js';
                    ds.charset = 'UTF-8';
                    (document.getElementsByTagName('head')[0] 
                     || document.getElementsByTagName('body')[0]).appendChild(ds);
                })();
                </script>
            <!-- 多说公共JS代码 end -->
</div></div>
{%endif%}

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