Month: January 2019

Python: Parsing XML and Retaining the Comments

By default, Python’s built-in ElementTree module strips comments as it reads them. The solution is just obscure enough to be hard to find.

import xml.etree.ElementTree as ET

class _CommentedTreeBuilder(ET.TreeBuilder):
    def comment(self, data):
        self.start('!comment', {})
        self.data(data)
        self.end('!comment')

def parse(filepath):
    ctb = _CommentedTreeBuilder()
    xp = ET.XMLParser(target=ctb)
    tree = ET.parse(filepath, parser=xp)

    root = tree.getroot()
    # ...

When enumerating the parsed nodes, the comments will have a tag-name of “!comment”.

ssl: Promoting Existing Client Socket to SSL in C/C++

You may be in a situation where something else produces the sockets for you (such as an event-loop) or you otherwise need to manage the socket rather then allowing something else to.

#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <openssl/ssl.h>

int main(int argc, char *argv[])
{
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (!sockfd) {
        printf("Error creating socket.\n");
        return -1;
    }

    struct sockaddr_in sa;
    memset (&sa, 0, sizeof(sa));

    sa.sin_family = AF_INET;
    sa.sin_addr.s_addr = inet_addr("172.217.2.196");
    sa.sin_port = htons (443); 

    socklen_t socklen = sizeof(sa);
    if (connect(sockfd, (struct sockaddr *)&sa, socklen)) {
        printf("Error connecting to server.\n");
        return -1;
    }

    SSL_library_init();
    SSLeay_add_ssl_algorithms();
    SSL_load_error_strings();

    const SSL_METHOD *meth = TLSv1_2_client_method();
    SSL_CTX *ctx = SSL_CTX_new (meth);

    SSL *ssl = SSL_new (ctx);
    if (ssl == NULL) {
        printf("Could not create SSL context.\n");
        return -1;
    }

    SSL_set_fd(ssl, sockfd);

    int err = SSL_connect(ssl);
    if (err <= 0) {
        printf("Could not connect.\n");
        return -1;
    }

    printf ("SSL connection using %s\n", SSL_get_cipher (ssl));

    // Do send/receive here.

    return 0;
}

Adapted from openssl-in-c-socket-connection-https-client, and works with both OpenSSL and BoringSSL.

Receive Daily Digest Emails with Active Github Issues

go-github-reminders is a project that you can schedule in order to receive periodic emails of recently updated Github issues that you are involved in (technically, subscribed to) that you have not recently responded to.

For those of us with a lot to do, this keeps us on top of things.

Go: Parsing Time Expressions

go-time-parse will parse time expressions into time.Duration quantities. From the example:

actualDuration, phraseType, err := ParseDuration("24 days from now")
log.PanicIf(err)

fmt.Printf("%d [%s]\n", actualDuration/time.Hour/24, phraseType)

actualDuration, phraseType, err = ParseDuration("now")
log.PanicIf(err)

fmt.Printf("%d [%s]\n", actualDuration, phraseType)

actualDuration, phraseType, err = ParseDuration("12m")
log.PanicIf(err)

fmt.Printf("%d [%s]\n", actualDuration/time.Minute, phraseType)

actualDuration, phraseType, err = ParseDuration("every 6 hours")
log.PanicIf(err)

fmt.Printf("%d [%s]\n", actualDuration/time.Hour, phraseType)

Output:

24 [time]
0 [time]
12 [interval]
6 [interval]