ASCIIMX | Log

Tracking 13,000 marine vessel route points. Needed shortest paths between ports for arrival prediction. Neo4j’s Dijkstra’s algorithm slows after 4,000 route diff --git a/_site/log/search-with-cgi/index.html b/_site/log/search-with-cgi/index.html deleted file mode 100644 index 71b9f23..0000000 --- a/_site/log/search-with-cgi/index.html +++ /dev/null @@ -1,133 +0,0 @@ - - - - - Site search using Perl + CGI - - - - - Site search using Perl + CGI - - - - - - - - - -

SITE SEARCH USING PERL + CGI

29 DECEMBER 2025

-
-

Number of articles on the site are growing. Need a way to search site.

- -

Searching the RSS feed client-side using JavaScript is not an option. That -would make the feed much heavier and break the site for text-based web browsers -like Lynx.

- -

Not gonna use an inverted index–More than an evening’s effort, especially if I -want partial matching. I want partial matching.

- -

Few lines of Perl could do a regex search and send the result back via CGI. -OpenBSD httpd speaks CGI. Perl and slowcgi are in the base system. No -dependencies.

- -

Perl: traverse directory with File::Find. If search text is found grab the file -name, title and up to 50 chars from the first paragraph to include in the -search result.

- -

find({
-    wanted => sub {
-        return unless -f $_ && $_ eq 'index.html';
-        # ... file reading ...
-        if ($content =~ /\Q$search_text\E/i) {
-            # Extract title, snippet
-            push @results, { 
-                path    => $File::Find::name,
-                title   => $title, 
-                snippet => $snippet 
-            };
-        }
-    },
-    follow => 0,
-}, $dir);
-

- -

httpd sets the search text in QUERY_STRING env. Don’t need Perl’s CGI module.

- -

my %params;
-if ($ENV{QUERY_STRING}) {
-    foreach my $pair (split /&/, $ENV{QUERY_STRING}) {
-        my ($key, $value) = split /=/, $pair;
-        $value =~ tr/+/ /;
-        $value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg;
-        $params{$key} = $value;
-    }
-}
-

- -

Security.

- -

ReDOS, XSS, command injection, symlink attacks. Did I miss anything? Probably.

- -

ReDOS: sanitized user input, length-limit search text, quote metacharacters -with \Q$search_text\E.

- -

XSS: sanitized user input. Escaped HTML.

- -

Command injection: no exec()/system() calls. Non-privileged user (www).

- -

Symlink attacks: File::Find don’t follow symlinks (follow => 0). chroot.

- -

Access controls: files (444), directories and CGI script: 554.

- -

Verdict: O(n) speed. Works on every conceivable browser. Good enough.

- -

Commit: 9fec793

by W. D. Sadeep Madurange

@@ -86,8 +70,7 @@ ST-LINK/v2 programmer connects to that to communicate with the chip. Upload procedure - Sample LED blink program with OpenOCD config and linker scripts in tarball -below. + Build. Magic is in the script.ld linker script. `$ arm-none-eabi-gcc -mcpu=cortex-m3 -mthumb -T script.ld \ -nostartfiles \ @@ -95,7 +78,7 @@ below. -o a.elf main.c` - Upload: + Upload using OpenOCD: $ openocd -f openocd-due.cfg $ telnet localhost 4444 @@ -124,8 +107,8 @@ GPNVM2=0: flash0 (0x80000) maps to 0x00000. Both cleared: flash1 maps to Linker script notes -Vector table must be at first flash address–mandatory for ARM chips unless -using VTOR register for relocation. +Vector table must be at first flash address–required for ARM chips unless +relocated using VTOR register. First vector table entry: stack pointer. Initialize to highest memory location (ATSAM3X8E has descending stack). diff --git a/_site/log/arduino-uno/index.html b/_site/log/arduino-uno/index.html index 66fff37..33ca118 100644 --- a/_site/log/arduino-uno/index.html +++ b/_site/log/arduino-uno/index.html @@ -1,9 +1,5 @@ - - - ATmega328P at 3.3V and 5V - @@ -13,8 +9,6 @@ - - @@ -47,7 +41,7 @@ ATMEGA328P AT 3.3V AND 5V - 10 JUNE 2025 + 10 JUNE 2025 Quick reference for wiring ATmega328P ICs at 5V and 3.3V. 5V uses 16MHz crystal, 3.3V uses 8MHz. diff --git a/_site/log/bumblebee/index.html b/_site/log/bumblebee/index.html index b4c9c25..9d12851 100644 --- a/_site/log/bumblebee/index.html +++ b/_site/log/bumblebee/index.html @@ -1,9 +1,5 @@ - - - Bumblebee: browser automation - @@ -13,8 +9,6 @@ - - @@ -47,7 +41,7 @@ BUMBLEBEE: BROWSER AUTOMATION - 02 APRIL 2025 + 02 APRIL 2025 Built with Andy Zhang for an employer. Tool to automate web scraping script generation. diff --git a/_site/log/e-reader/index.html b/_site/log/e-reader/index.html index 44ae1e6..2d76f26 100644 --- a/_site/log/e-reader/index.html +++ b/_site/log/e-reader/index.html @@ -1,9 +1,5 @@ - - - ESP32 e-reader prototype - @@ -13,8 +9,6 @@ - - @@ -47,7 +41,7 @@ ESP32 E-READER PROTOTYPE - 24 OCTOBER 2023 + 24 OCTOBER 2023 First project with e-paper displays and ESP32. diff --git a/_site/log/etlas/index.html b/_site/log/etlas/index.html index 8149618..97f0ff8 100644 --- a/_site/log/etlas/index.html +++ b/_site/log/etlas/index.html @@ -1,9 +1,5 @@ - - - Etlas: e-paper dashboard - @@ -13,8 +9,6 @@ - - @@ -47,7 +41,7 @@ ETLAS: E-PAPER DASHBOARD - 05 SEPTEMBER 2024 + 05 SEPTEMBER 2024 Repurposed e-reader prototype into something for regular use. News, stocks, weather dashboard. ESP32 NodeMCU D1 + 7.5” Waveshare e-paper + diff --git a/_site/log/fpm-door-lock-lp/index.html b/_site/log/fpm-door-lock-lp/index.html index a5d237c..8d1c721 100644 --- a/_site/log/fpm-door-lock-lp/index.html +++ b/_site/log/fpm-door-lock-lp/index.html @@ -1,9 +1,5 @@ - - - Fingerprint door lock (LP) - @@ -13,8 +9,6 @@ - - @@ -47,7 +41,7 @@ FINGERPRINT DOOR LOCK (LP) - 18 AUGUST 2025 + 18 AUGUST 2025 Second iteration of the RF door lock. Old version worked but drew too much quiescent current. Sensor and servo pulled 13.8mA and 4.6mA diff --git a/_site/log/fpm-door-lock-rf/index.html b/_site/log/fpm-door-lock-rf/index.html index 04c84de..342fa44 100644 --- a/_site/log/fpm-door-lock-rf/index.html +++ b/_site/log/fpm-door-lock-rf/index.html @@ -1,9 +1,5 @@ - - - Fingerprint door lock (RF) - @@ -13,8 +9,6 @@ - - @@ -47,7 +41,7 @@ FINGERPRINT DOOR LOCK (RF) - 05 JUNE 2025 + 05 JUNE 2025 Wanted to unlock door with fingerprint, wirelessly to avoid drilling. diff --git a/_site/log/index.html b/_site/log/index.html index defcfed..955f645 100644 --- a/_site/log/index.html +++ b/_site/log/index.html @@ -49,19 +49,6 @@ -
- Site search using Perl + CGI -	- - 2025-12-29 - -
Matrix Rain: 2025 refactor diff --git a/_site/log/matrix-digital-rain/index.html b/_site/log/matrix-digital-rain/index.html index a570230..86d918d 100644 --- a/_site/log/matrix-digital-rain/index.html +++ b/_site/log/matrix-digital-rain/index.html @@ -1,9 +1,5 @@ - - - Matrix Rain: 2025 refactor - @@ -13,8 +9,6 @@ - - @@ -47,7 +41,7 @@ MATRIX RAIN: 2025 REFACTOR - 21 DECEMBER 2025 + 21 DECEMBER 2025 The 2022 version worked but had some loose ends. Unicode support was inflexible–couldn’t mix ASCII with Katakana; Phosphor decay was stored in a diff --git a/_site/log/mosfet-switches/index.html b/_site/log/mosfet-switches/index.html index 37d6707..e3a6868 100644 --- a/_site/log/mosfet-switches/index.html +++ b/_site/log/mosfet-switches/index.html @@ -1,9 +1,5 @@ - - - High-side MOSFET switching - @@ -13,8 +9,6 @@ - - @@ -47,7 +41,7 @@ HIGH-SIDE MOSFET SWITCHING - 22 JUNE 2025 + 22 JUNE 2025 Needed low-power switching for the fingerprint door lock. Servo and FPM draw high quiescent current–had to diff --git a/_site/log/neo4j-a-star-search/index.html b/_site/log/neo4j-a-star-search/index.html index 013cd95..4154255 100644 --- a/_site/log/neo4j-a-star-search/index.html +++ b/_site/log/neo4j-a-star-search/index.html @@ -1,9 +1,5 @@ - - - Neo4j shortest path optimization - @@ -13,8 +9,6 @@ - - @@ -47,9 +41,9 @@ NEO4J SHORTEST PATH OPTIMIZATION - 06 MARCH 2018 + 06 MARCH 2018 - Replaced Dijkstra’s for vessel route tracking in Neo4J. + Replaced Dijkstra’s search for vessel route tracking in Neo4J. Tracking 13,000 marine vessel route points. Needed shortest paths between ports for arrival prediction. Neo4j’s Dijkstra’s algorithm slows after 4,000 route diff --git a/_site/log/search-with-cgi/index.html b/_site/log/search-with-cgi/index.html deleted file mode 100644 index 71b9f23..0000000 --- a/_site/log/search-with-cgi/index.html +++ /dev/null @@ -1,133 +0,0 @@ - - - - - Site search using Perl + CGI - - - - - Site search using Perl + CGI - - - - - - - - - - - - - - hme - - - log - - - poc - - - abt - - - sws - - - rss - - - - - - - - - - SITE SEARCH USING PERL + CGI - 29 DECEMBER 2025 - - Number of articles on the site are growing. Need a way to search site. - - Searching the RSS feed client-side using JavaScript is not an option. That -would make the feed much heavier and break the site for text-based web browsers -like Lynx. - - Not gonna use an inverted index–More than an evening’s effort, especially if I -want partial matching. I want partial matching. - - Few lines of Perl could do a regex search and send the result back via CGI. -OpenBSD httpd speaks CGI. Perl and slowcgi are in the base system. No -dependencies. - - Perl: traverse directory with File::Find. If search text is found grab the file -name, title and up to 50 chars from the first paragraph to include in the -search result. - - `find({ - wanted => sub { - return unless -f $_ && $_ eq 'index.html'; - # ... file reading ... - if ($content =~ /\Q$search_text\E/i) { - # Extract title, snippet - push @results, { - path => $File::Find::name, - title => $title, - snippet => $snippet - }; - } - }, - follow => 0, -}, $dir); -` - - httpd sets the search text in QUERY_STRING env. Don’t need Perl’s CGI module. - - `my %params; -if ($ENV{QUERY_STRING}) { - foreach my $pair (split /&/, $ENV{QUERY_STRING}) { - my ($key, $value) = split /=/, $pair; - $value =~ tr/+/ /; - $value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg; - $params{$key} = $value; - } -} -` - - Security. - - ReDOS, XSS, command injection, symlink attacks. Did I miss anything? Probably. - - ReDOS: sanitized user input, length-limit search text, quote metacharacters -with `\Q$search_text\E`. - - XSS: sanitized user input. Escaped HTML. - - Command injection: no exec()/system() calls. Non-privileged user (www). - - Symlink attacks: File::Find don’t follow symlinks (follow => 0). chroot. - - Access controls: files (444), directories and CGI script: 554. - - Verdict: O(n) speed. Works on every conceivable browser. Good enough. - - Commit: 9fec793 - - by W. D. Sadeep Madurange - - - - - - - - © ASCIIMX - 2025 - - - - - - - diff --git a/_site/posts.xml b/_site/posts.xml index 6f08cc2..88f6d2f 100644 --- a/_site/posts.xml +++ b/_site/posts.xml @@ -1 +1 @@ -Jekyll2025-12-30T22:31:10+08:00/posts.xmlASCIIMXW. D. Sadeep Madurange \ No newline at end of file +Jekyll2025-12-31T21:45:45+08:00/posts.xmlASCIIMXW. D. Sadeep Madurange \ No newline at end of file diff --git a/_site/projects/index.html b/_site/projects/index.html index 2357793..6a2f996 100644 --- a/_site/projects/index.html +++ b/_site/projects/index.html @@ -74,6 +74,14 @@
+ + + + Fingerprint door lock (RF) + +	@@ -82,6 +90,11 @@
@@ -90,11 +103,6 @@
@@ -106,8 +114,6 @@ -

ATSAM3X8E BARE-METAL PROGRAMMING

16 SEPTEMBER 2024

16 SEPTEMBER 2024

Toolchain

Electrical connections

Upload procedure

Linker script notes

ATMEGA328P AT 3.3V AND 5V

10 JUNE 2025

10 JUNE 2025

BUMBLEBEE: BROWSER AUTOMATION

02 APRIL 2025

02 APRIL 2025

ESP32 E-READER PROTOTYPE

24 OCTOBER 2023

24 OCTOBER 2023

ETLAS: E-PAPER DASHBOARD

05 SEPTEMBER 2024

05 SEPTEMBER 2024

FINGERPRINT DOOR LOCK (LP)

18 AUGUST 2025

18 AUGUST 2025

FINGERPRINT DOOR LOCK (RF)

05 JUNE 2025

05 JUNE 2025

MATRIX RAIN: 2025 REFACTOR

21 DECEMBER 2025

21 DECEMBER 2025

HIGH-SIDE MOSFET SWITCHING

22 JUNE 2025

22 JUNE 2025

NEO4J SHORTEST PATH OPTIMIZATION

06 MARCH 2018

06 MARCH 2018

SITE SEARCH USING PERL + CGI

29 DECEMBER 2025

Fingerprint door lock (RF)