1657244220
Level-sublevel: Separate Sections Of Levelup, with Hooks!
level-sublevel
Separate sections of levelup, with hooks!
This module allows you to create separate sections of a levelup database, kinda like tables in an sql database, but evented, and ranged, for real-time changing data.
level-sublevel@6 BREAKING CHANGES
The long awaited level-sublevel rewrite is out! You are hereby warned this is a significant breaking change. So it's good to use it with a new project, The user api is mostly the same as before, but the way that keys are encoded has changed, and this means you cannot run 6 on a database you created with 5.
Also, createWriteStream has been removed, in anticipation of this change use something like level-write-stream
Legacy Mode
Using leveldb with legacy mode is the simplest way to get the new sublevel on top of a database that used old sublevel. Simply require sublevel like this:
var level = require('level')
// V *** require legacy.js ***
var sublevel = require('level-sublevel/legacy')
var db = sublevel(level(path))
Migration Tool
@calvinmetcalf has created a migration tool: sublevel-migrate
This can be used to copy an old level-sublevel into the new format.
Stability
Unstable: Expect patches and features, possible api changes.
This module is working well, but may change in the future as its use is further explored.
Example
var LevelUp = require('levelup')
var Sublevel = require('level-sublevel')
var db = Sublevel(LevelUp('/tmp/sublevel-example'))
var sub = db.sublevel('stuff')
//put a key into the main levelup
db.put(key, value, function () {})
//put a key into the sub-section!
sub.put(key2, value, function () {})
Sublevel prefixes each subsection so that it will not collide with the outer db when saving or reading!
Hooks
Hooks are specially built into Sublevel so that you can do all sorts of clever stuff, like generating views or logs when records are inserted!
Records added via hooks will be atomically inserted with the triggering change.
Hooks Example
Whenever a record is inserted, save an index to it by the time it was inserted.
var sub = db.sublevel('SEQ')
db.pre(function (ch, add) {
add({
key: ''+Date.now(),
value: ch.key,
type: 'put',
// NOTE: pass the destination db to add the value to that subsection!
prefix: sub
})
})
db.put('key', 'VALUE', function (err) {
// read all the records inserted by the hook!
sub.createReadStream().on('data', console.log)
})
Notice that the prefix property to add() is set to sub, which tells the hook to save the new record in the sub section.
Batches
In sublevel batches also support a prefix: subdb property, if set, this row will be inserted into that database section, instead of the current section, similar to the pre hook above.
var sub1 = db.sublevel('SUB_1')
var sub2 = db.sublevel('SUM_2')
sub.batch([
{key: 'key', value: 'Value', type: 'put'},
{key: 'key', value: 'Value', type: 'put', prefix: sub2},
], function (err) {...})
Author: Dominictarr
Source Code: https://github.com/dominictarr/level-sublevel
License: MIT license
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Buddha Community
1657244220
Level-sublevel: Separate Sections Of Levelup, with Hooks!
level-sublevel
Separate sections of levelup, with hooks!
This module allows you to create separate sections of a levelup database, kinda like tables in an sql database, but evented, and ranged, for real-time changing data.
level-sublevel@6 BREAKING CHANGES
The long awaited level-sublevel rewrite is out! You are hereby warned this is a significant breaking change. So it's good to use it with a new project, The user api is mostly the same as before, but the way that keys are encoded has changed, and this means you cannot run 6 on a database you created with 5.
Also, createWriteStream has been removed, in anticipation of this change use something like level-write-stream
Legacy Mode
Using leveldb with legacy mode is the simplest way to get the new sublevel on top of a database that used old sublevel. Simply require sublevel like this:
var level = require('level')
// V *** require legacy.js ***
var sublevel = require('level-sublevel/legacy')
var db = sublevel(level(path))
Migration Tool
@calvinmetcalf has created a migration tool: sublevel-migrate
This can be used to copy an old level-sublevel into the new format.
Stability
Unstable: Expect patches and features, possible api changes.
This module is working well, but may change in the future as its use is further explored.
Example
var LevelUp = require('levelup')
var Sublevel = require('level-sublevel')
var db = Sublevel(LevelUp('/tmp/sublevel-example'))
var sub = db.sublevel('stuff')
//put a key into the main levelup
db.put(key, value, function () {})
//put a key into the sub-section!
sub.put(key2, value, function () {})
Sublevel prefixes each subsection so that it will not collide with the outer db when saving or reading!
Hooks
Hooks are specially built into Sublevel so that you can do all sorts of clever stuff, like generating views or logs when records are inserted!
Records added via hooks will be atomically inserted with the triggering change.
Hooks Example
Whenever a record is inserted, save an index to it by the time it was inserted.
var sub = db.sublevel('SEQ')
db.pre(function (ch, add) {
add({
key: ''+Date.now(),
value: ch.key,
type: 'put',
// NOTE: pass the destination db to add the value to that subsection!
prefix: sub
})
})
db.put('key', 'VALUE', function (err) {
// read all the records inserted by the hook!
sub.createReadStream().on('data', console.log)
})
Notice that the prefix property to add() is set to sub, which tells the hook to save the new record in the sub section.
Batches
In sublevel batches also support a prefix: subdb property, if set, this row will be inserted into that database section, instead of the current section, similar to the pre hook above.
var sub1 = db.sublevel('SUB_1')
var sub2 = db.sublevel('SUM_2')
sub.batch([
{key: 'key', value: 'Value', type: 'put'},
{key: 'key', value: 'Value', type: 'put', prefix: sub2},
], function (err) {...})
Author: Dominictarr
Source Code: https://github.com/dominictarr/level-sublevel
License: MIT license
1656899776
Graph-scroll: Simple Scrolling Events for D3 Graphs
graph-scroll.js
Simple scrolling events for d3 graphs. Based on stack
Demo/Documentation
graph-scroll takes a selection of explanatory text sections and dispatches active events as different sections are scrolled into to view. These active events can be used to update a chart's state.
d3.graphScroll()
.sections(d3.selectAll('#sections > div'))
.on('active', function(i){ console.log(i + 'th section active') })
The top most element scrolled fully into view is classed graph-scroll-active. This makes it easy to highlight the active section with css:
#sections > div{
opacity: .3
}
#sections div.graph-scroll-active{
opacity: 1;
}
To support headers and intro images/text, we use a container element containing the explanatory text and graph.
<h1>Page Title</div>
<div id='container'>
<div id='graph'></div>
<div id='sections'>
<div>Section 0</div>
<div>Section 1</div>
<div>Section 2</div>
</div>
</div>
<h1>Footer</h1>
If these elements are passed to graphScroll as selections with container and graph, every element in the graph selection will be classed graph-scroll-graph if the top of the container is out of view.
d3.graphScroll()
.graph(d3.selectAll('#graph'))
.container(d3.select('#container'))
.sections(d3.selectAll('#sections > div'))
.on('active', function(i){ console.log(i + 'th section active') })
When the graph starts to scroll out of view, position: sticky keeps the graph element stuck to the top of the page while the text scrolls by.
#container{
position: relative;
}
#sections{
width: 340px;
}
#graph{
margin-left: 40px;
width: 500px;
position: sticky;
top: 0px;
float: right;
}
On mobile centering the graph and sections while adding a some padding for the first slide is a good option:
@media (max-width: 925px) {
#graph{
width: 100%;
margin-left: 0px;
float: none;
}
#sections{
position: relative;
margin: 0px auto;
padding-top: 400px;
}
}
Adjust the amount of pixels before a new section is triggered is also helpful on mobile (Defaults to 200 pixels):
graphScroll.offset(300)
To update or replace a graphScroll instance, pass a string to eventId to remove the old event listeners:
graphScroll.eventId('uniqueId1')Author: 1wheel
Source Code: https://github.com/1wheel/graph-scroll
License: MIT license
1607768450
What are hooks in React JS? - INFO AT ONE
In this article, you will learn what are hooks in React JS? and when to use react hooks? React JS is developed by Facebook in the year 2013. There are many students and the new developers who have confusion between react and hooks in react. Well, it is not different, react is a programming language and hooks is a function which is used in react programming language.
Read More:- https://infoatone.com/what-are-hooks-in-react-js/
#react #hooks in react #react hooks example #react js projects for beginners #what are hooks in react js? #when to use react hooks
1667425440
Pdf2gerb: Perl Script Converts PDF Files to Gerber format
pdf2gerb
Perl script converts PDF files to Gerber format
Pdf2Gerb generates Gerber 274X photoplotting and Excellon drill files from PDFs of a PCB. Up to three PDFs are used: the top copper layer, the bottom copper layer (for 2-sided PCBs), and an optional silk screen layer. The PDFs can be created directly from any PDF drawing software, or a PDF print driver can be used to capture the Print output if the drawing software does not directly support output to PDF.
The general workflow is as follows:
- Design the PCB using your favorite CAD or drawing software.
- Print the top and bottom copper and top silk screen layers to a PDF file.
- Run Pdf2Gerb on the PDFs to create Gerber and Excellon files.
- Use a Gerber viewer to double-check the output against the original PCB design.
- Make adjustments as needed.
- Submit the files to a PCB manufacturer.
Please note that Pdf2Gerb does NOT perform DRC (Design Rule Checks), as these will vary according to individual PCB manufacturer conventions and capabilities. Also note that Pdf2Gerb is not perfect, so the output files must always be checked before submitting them. As of version 1.6, Pdf2Gerb supports most PCB elements, such as round and square pads, round holes, traces, SMD pads, ground planes, no-fill areas, and panelization. However, because it interprets the graphical output of a Print function, there are limitations in what it can recognize (or there may be bugs).
See docs/Pdf2Gerb.pdf for install/setup, config, usage, and other info.
pdf2gerb_cfg.pm
#Pdf2Gerb config settings:
#Put this file in same folder/directory as pdf2gerb.pl itself (global settings),
#or copy to another folder/directory with PDFs if you want PCB-specific settings.
#There is only one user of this file, so we don't need a custom package or namespace.
#NOTE: all constants defined in here will be added to main namespace.
#package pdf2gerb_cfg;
use strict; #trap undef vars (easier debug)
use warnings; #other useful info (easier debug)
##############################################################################################
#configurable settings:
#change values here instead of in main pfg2gerb.pl file
use constant WANT_COLORS => ($^O !~ m/Win/); #ANSI colors no worky on Windows? this must be set < first DebugPrint() call
#just a little warning; set realistic expectations:
#DebugPrint("${\(CYAN)}Pdf2Gerb.pl ${\(VERSION)}, $^O O/S\n${\(YELLOW)}${\(BOLD)}${\(ITALIC)}This is EXPERIMENTAL software. \nGerber files MAY CONTAIN ERRORS. Please CHECK them before fabrication!${\(RESET)}", 0); #if WANT_DEBUG
use constant METRIC => FALSE; #set to TRUE for metric units (only affect final numbers in output files, not internal arithmetic)
use constant APERTURE_LIMIT => 0; #34; #max #apertures to use; generate warnings if too many apertures are used (0 to not check)
use constant DRILL_FMT => '2.4'; #'2.3'; #'2.4' is the default for PCB fab; change to '2.3' for CNC
use constant WANT_DEBUG => 0; #10; #level of debug wanted; higher == more, lower == less, 0 == none
use constant GERBER_DEBUG => 0; #level of debug to include in Gerber file; DON'T USE FOR FABRICATION
use constant WANT_STREAMS => FALSE; #TRUE; #save decompressed streams to files (for debug)
use constant WANT_ALLINPUT => FALSE; #TRUE; #save entire input stream (for debug ONLY)
#DebugPrint(sprintf("${\(CYAN)}DEBUG: stdout %d, gerber %d, want streams? %d, all input? %d, O/S: $^O, Perl: $]${\(RESET)}\n", WANT_DEBUG, GERBER_DEBUG, WANT_STREAMS, WANT_ALLINPUT), 1);
#DebugPrint(sprintf("max int = %d, min int = %d\n", MAXINT, MININT), 1);
#define standard trace and pad sizes to reduce scaling or PDF rendering errors:
#This avoids weird aperture settings and replaces them with more standardized values.
#(I'm not sure how photoplotters handle strange sizes).
#Fewer choices here gives more accurate mapping in the final Gerber files.
#units are in inches
use constant TOOL_SIZES => #add more as desired
(
#round or square pads (> 0) and drills (< 0):
.010, -.001, #tiny pads for SMD; dummy drill size (too small for practical use, but needed so StandardTool will use this entry)
.031, -.014, #used for vias
.041, -.020, #smallest non-filled plated hole
.051, -.025,
.056, -.029, #useful for IC pins
.070, -.033,
.075, -.040, #heavier leads
# .090, -.043, #NOTE: 600 dpi is not high enough resolution to reliably distinguish between .043" and .046", so choose 1 of the 2 here
.100, -.046,
.115, -.052,
.130, -.061,
.140, -.067,
.150, -.079,
.175, -.088,
.190, -.093,
.200, -.100,
.220, -.110,
.160, -.125, #useful for mounting holes
#some additional pad sizes without holes (repeat a previous hole size if you just want the pad size):
.090, -.040, #want a .090 pad option, but use dummy hole size
.065, -.040, #.065 x .065 rect pad
.035, -.040, #.035 x .065 rect pad
#traces:
.001, #too thin for real traces; use only for board outlines
.006, #minimum real trace width; mainly used for text
.008, #mainly used for mid-sized text, not traces
.010, #minimum recommended trace width for low-current signals
.012,
.015, #moderate low-voltage current
.020, #heavier trace for power, ground (even if a lighter one is adequate)
.025,
.030, #heavy-current traces; be careful with these ones!
.040,
.050,
.060,
.080,
.100,
.120,
);
#Areas larger than the values below will be filled with parallel lines:
#This cuts down on the number of aperture sizes used.
#Set to 0 to always use an aperture or drill, regardless of size.
use constant { MAX_APERTURE => max((TOOL_SIZES)) + .004, MAX_DRILL => -min((TOOL_SIZES)) + .004 }; #max aperture and drill sizes (plus a little tolerance)
#DebugPrint(sprintf("using %d standard tool sizes: %s, max aper %.3f, max drill %.3f\n", scalar((TOOL_SIZES)), join(", ", (TOOL_SIZES)), MAX_APERTURE, MAX_DRILL), 1);
#NOTE: Compare the PDF to the original CAD file to check the accuracy of the PDF rendering and parsing!
#for example, the CAD software I used generated the following circles for holes:
#CAD hole size: parsed PDF diameter: error:
# .014 .016 +.002
# .020 .02267 +.00267
# .025 .026 +.001
# .029 .03167 +.00267
# .033 .036 +.003
# .040 .04267 +.00267
#This was usually ~ .002" - .003" too big compared to the hole as displayed in the CAD software.
#To compensate for PDF rendering errors (either during CAD Print function or PDF parsing logic), adjust the values below as needed.
#units are pixels; for example, a value of 2.4 at 600 dpi = .0004 inch, 2 at 600 dpi = .0033"
use constant
{
HOLE_ADJUST => -0.004 * 600, #-2.6, #holes seemed to be slightly oversized (by .002" - .004"), so shrink them a little
RNDPAD_ADJUST => -0.003 * 600, #-2, #-2.4, #round pads seemed to be slightly oversized, so shrink them a little
SQRPAD_ADJUST => +0.001 * 600, #+.5, #square pads are sometimes too small by .00067, so bump them up a little
RECTPAD_ADJUST => 0, #(pixels) rectangular pads seem to be okay? (not tested much)
TRACE_ADJUST => 0, #(pixels) traces seemed to be okay?
REDUCE_TOLERANCE => .001, #(inches) allow this much variation when reducing circles and rects
};
#Also, my CAD's Print function or the PDF print driver I used was a little off for circles, so define some additional adjustment values here:
#Values are added to X/Y coordinates; units are pixels; for example, a value of 1 at 600 dpi would be ~= .002 inch
use constant
{
CIRCLE_ADJUST_MINX => 0,
CIRCLE_ADJUST_MINY => -0.001 * 600, #-1, #circles were a little too high, so nudge them a little lower
CIRCLE_ADJUST_MAXX => +0.001 * 600, #+1, #circles were a little too far to the left, so nudge them a little to the right
CIRCLE_ADJUST_MAXY => 0,
SUBST_CIRCLE_CLIPRECT => FALSE, #generate circle and substitute for clip rects (to compensate for the way some CAD software draws circles)
WANT_CLIPRECT => TRUE, #FALSE, #AI doesn't need clip rect at all? should be on normally?
RECT_COMPLETION => FALSE, #TRUE, #fill in 4th side of rect when 3 sides found
};
#allow .012 clearance around pads for solder mask:
#This value effectively adjusts pad sizes in the TOOL_SIZES list above (only for solder mask layers).
use constant SOLDER_MARGIN => +.012; #units are inches
#line join/cap styles:
use constant
{
CAP_NONE => 0, #butt (none); line is exact length
CAP_ROUND => 1, #round cap/join; line overhangs by a semi-circle at either end
CAP_SQUARE => 2, #square cap/join; line overhangs by a half square on either end
CAP_OVERRIDE => FALSE, #cap style overrides drawing logic
};
#number of elements in each shape type:
use constant
{
RECT_SHAPELEN => 6, #x0, y0, x1, y1, count, "rect" (start, end corners)
LINE_SHAPELEN => 6, #x0, y0, x1, y1, count, "line" (line seg)
CURVE_SHAPELEN => 10, #xstart, ystart, x0, y0, x1, y1, xend, yend, count, "curve" (bezier 2 points)
CIRCLE_SHAPELEN => 5, #x, y, 5, count, "circle" (center + radius)
};
#const my %SHAPELEN =
#Readonly my %SHAPELEN =>
our %SHAPELEN =
(
rect => RECT_SHAPELEN,
line => LINE_SHAPELEN,
curve => CURVE_SHAPELEN,
circle => CIRCLE_SHAPELEN,
);
#panelization:
#This will repeat the entire body the number of times indicated along the X or Y axes (files grow accordingly).
#Display elements that overhang PCB boundary can be squashed or left as-is (typically text or other silk screen markings).
#Set "overhangs" TRUE to allow overhangs, FALSE to truncate them.
#xpad and ypad allow margins to be added around outer edge of panelized PCB.
use constant PANELIZE => {'x' => 1, 'y' => 1, 'xpad' => 0, 'ypad' => 0, 'overhangs' => TRUE}; #number of times to repeat in X and Y directions
# Set this to 1 if you need TurboCAD support.
#$turboCAD = FALSE; #is this still needed as an option?
#CIRCAD pad generation uses an appropriate aperture, then moves it (stroke) "a little" - we use this to find pads and distinguish them from PCB holes.
use constant PAD_STROKE => 0.3; #0.0005 * 600; #units are pixels
#convert very short traces to pads or holes:
use constant TRACE_MINLEN => .001; #units are inches
#use constant ALWAYS_XY => TRUE; #FALSE; #force XY even if X or Y doesn't change; NOTE: needs to be TRUE for all pads to show in FlatCAM and ViewPlot
use constant REMOVE_POLARITY => FALSE; #TRUE; #set to remove subtractive (negative) polarity; NOTE: must be FALSE for ground planes
#PDF uses "points", each point = 1/72 inch
#combined with a PDF scale factor of .12, this gives 600 dpi resolution (1/72 * .12 = 600 dpi)
use constant INCHES_PER_POINT => 1/72; #0.0138888889; #multiply point-size by this to get inches
# The precision used when computing a bezier curve. Higher numbers are more precise but slower (and generate larger files).
#$bezierPrecision = 100;
use constant BEZIER_PRECISION => 36; #100; #use const; reduced for faster rendering (mainly used for silk screen and thermal pads)
# Ground planes and silk screen or larger copper rectangles or circles are filled line-by-line using this resolution.
use constant FILL_WIDTH => .01; #fill at most 0.01 inch at a time
# The max number of characters to read into memory
use constant MAX_BYTES => 10 * M; #bumped up to 10 MB, use const
use constant DUP_DRILL1 => TRUE; #FALSE; #kludge: ViewPlot doesn't load drill files that are too small so duplicate first tool
my $runtime = time(); #Time::HiRes::gettimeofday(); #measure my execution time
print STDERR "Loaded config settings from '${\(__FILE__)}'.\n";
1; #last value must be truthful to indicate successful load
#############################################################################################
#junk/experiment:
#use Package::Constants;
#use Exporter qw(import); #https://perldoc.perl.org/Exporter.html
#my $caller = "pdf2gerb::";
#sub cfg
#{
# my $proto = shift;
# my $class = ref($proto) || $proto;
# my $settings =
# {
# $WANT_DEBUG => 990, #10; #level of debug wanted; higher == more, lower == less, 0 == none
# };
# bless($settings, $class);
# return $settings;
#}
#use constant HELLO => "hi there2"; #"main::HELLO" => "hi there";
#use constant GOODBYE => 14; #"main::GOODBYE" => 12;
#print STDERR "read cfg file\n";
#our @EXPORT_OK = Package::Constants->list(__PACKAGE__); #https://www.perlmonks.org/?node_id=1072691; NOTE: "_OK" skips short/common names
#print STDERR scalar(@EXPORT_OK) . " consts exported:\n";
#foreach(@EXPORT_OK) { print STDERR "$_\n"; }
#my $val = main::thing("xyz");
#print STDERR "caller gave me $val\n";
#foreach my $arg (@ARGV) { print STDERR "arg $arg\n"; }Download Details:
Author: swannman
Source Code: https://github.com/swannman/pdf2gerb
License: GPL-3.0 license
1585500660
React hooks - Giới thiệu tổng quát về Hooks
React hooks ra đời đã giúp functional component trở nên powerful hơn bao giờ hết! 😍Trước đây khi cần dùng đến các tính năng của React như state, life cycle thì mình bắt buộc phải dùng class component. Nhưng giờ thì đã khác, có hooks, functional component như hổ mọc thêm cánh, có thể xử lý được state, life cycle và những thứ khác của React một cách êm đềm.
Cùng mình xem hết videos để khám phá những điều thú vị từ React hooks nhé! 😉
Link tham khảo:
- Tài liệu trong video: https://drive.google.com/open?id=11FZZ6B5TzASNTYEPSXTuywzJ9jqxR8Xq
- Introduction to react hooks: https://reactjs.org/docs/hooks-intro.html
- React hooks API reference: https://reactjs.org/docs/hooks-reference.html
- React hooks FAQ: https://reactjs.org/docs/hooks-faq.html
#reactjs #react-hook #hook #javascript #web-development