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Index for binary compatibility, button to copy all code and LOC count

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Suzanne Soy 2021-04-02 06:35:02 +01:00
parent 80081c29be
commit 1763ff9ca3
1 changed files with 156 additions and 10 deletions
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index.html
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@ -254,18 +254,22 @@ h1:hover + .permalink, .permalink:hover { opacity: 1; }
}
function ___lolite(src, dest) {
}
function ___hex_hash(s) {
var id = ___global_unique_id++;
var hash = "object-hash-"+___to_hex(s.substr(0,20));
return '<span id="'+id+'" class="hex-hash" onmouseover="___hilite('+id+',\''+hash+'\')" onmouseout="___lolite('+id+',\''+hash+'\')">'
+ ___to_hex_for_printf(s.substr(0,10))
+ ___to_hex_for_printf(s.substr(10,10))
+ '</span>'
+ ___specialchars_and_colour(s.substr(20) /* should be empty unless there's a bug */);
}
function ___specialchars_and_colour_and_hex(s) {
if (s.substr(0,5) == "tree ") {
var sp = s.split('\0');
sp[0] = ___specialchars_and_colour(sp[0]);
sp[1] = ___specialchars_and_colour(sp[1]);
for (i = 2; i < sp.length; i++) {
var id=___global_unique_id++;
var hash = "object-hash-"+___to_hex(sp[i].substr(0,20));
sp[i] = '<span id="'+id+'" class="hex-hash" onmouseover="___hilite('+id+',\''+hash+'\')" onmouseout="___lolite('+id+',\''+hash+'\')">'
+ ___to_hex_for_printf(sp[i].substr(0,10))
+ ___to_hex_for_printf(sp[i].substr(10,10))
+ '</span>'
sp[i] = ___hex_hash(sp[i].substr(0,20))
+ ___specialchars_and_colour(sp[i].substr(20));
}
return sp.join('<span class="specialchar newline">\\000</span>');
@ -284,6 +288,56 @@ h1:hover + .permalink, .permalink:hover { opacity: 1; }
+ ___specialchars_and_colour(s.substr(5, s.length-6))
+ '</span>'
+ ___specialchars_and_colour(s.substr(s.length-1));
} else if(s.substr(0,4) == "DIRC") {
var html = 'DIRC'; // magic
var i = 4;
var binary_span = function(bits) {
var bytes = bits / 8;
html += '<span class="newline">' + ___to_hex_for_printf(s.substr(i, bytes)) + '</span>';
i += bytes;
}
binary_span(32); // version
binary_span(32); // entries
var entry_start = i;
while (i + 20 < s.length) {
binary_span(64); // ctime
binary_span(64); // mtime
binary_span(32); // device
binary_span(32); // inode
binary_span(32); // mode (stored as octal → binary)
binary_span(32); // uid
binary_span(32); // gid
binary_span(32); // size
html += ___hex_hash(s.substr(i, 20)); // hash
i += 20;
var length = s.substr(i, 2);
length = length.charCodeAt(0) * 256 + length.charCodeAt(1);
length &= 0xfff;
binary_span(16); // 4 bits flags, 12 bits file length
// file path until null
html += ___specialchars_and_colour(s.substr(i, length));
i += length;
while (i < s.length && (i - entry_start) % 8 != 0) {
// null bytes
if (s.charCodeAt(i) == 0) {
// as expected
html += '<span class="specialchar">\\000</span>';
} else {
// there's a bug in this git index, display the hex chars as they come.
html += ___specialchars_and_colour(s.substr(i, 1));
}
i++;
}
entry_start = i;
}
html += ___hex_hash(s.substr(i, 20)); // hash
i += 20;
html += ___specialchars_and_colour(s.substr(i)); // should be empty
return html;
} else if(s.substr(0,7) == "commit ") {
var sz = s.split('\0');
var sp = sz[1].split('\n');
@ -397,7 +451,7 @@ h1:hover + .permalink, .permalink:hover { opacity: 1; }
+ "</a>."
+ "<br />"
+ '<textarea id="elem-'+id+'" disabled="disabled" style="display:none">'
+ ___specialchars(___filesystem_to_printf(fs))
+ ___specialchars(___filesystem_to_printf(fs) || 'echo "Empty filesystem."')
+ '</textarea>'
+ "<table>" + entries.join('') + "</table></div>";
}
@ -1140,8 +1194,66 @@ git_checkout(initial_commit);
to the default branch (a file which does not exist yet, as this branch does not contain any commit at this point).</p>
<textarea id="in21">
function git_init() {
git_init_mkdir();
git_init_head();
git_init_mkdir();
git_init_head();
}
</textarea>
</section>
<section id="index">
<h1>The index</h1>
<p>When adding files with <code>git add</code>, GIT does not immediately create a commit object.
Instead, it adds the files to the index, which uses a binary format with lots of metadata.
The mock filesystem used here lacks most of these pieces of information, so thr value <code>0</code>
will be used for most fields. See <a href="https://mincong.io/2018/04/28/git-index/">this blog post</a>
for a more in-depth study of the index.</p>
<textarea id="index-binary-utils">
function binary(val, bytes) {
return from_hex(left_pad(val.toString(16), '0', bytes*2));
}
function binary16(val) { return binary(val, 2); }
function binary32(val) { return binary(val, 4); }
function binary64(val) { return binary(val, 8); }
</textarea>
<textarea id="make-index">
function store_index(paths) {
var magic = 'DIRC' // DIRectory Cache
var version = binary32(2);
var entries = binary32(paths.length);
var header = magic + version + entries;
index = header;
for (var i = 0; i < paths.length; i++) {
var ctime = binary64(0);
var mtime = binary64(0);
var device = binary32(0);
var inode = binary32(0);
// default permissions for files, in octal.
var mode = binary32(0100644);
var uid = binary32(0);
var gid = binary32(0);
var size = binary32(read(join_paths(current_directory, paths[i])).length);
var hash = from_hex(hash_object(true, 'blob', false, paths[i]));
// for this simple index, the flags (the 4 higher bits) are 0.
assert(paths[i].length < 0xfff)
var flags_and_file_path_length = binary16(paths[i].length)
var file_path = paths[i] + '\0';
entry = ctime + mtime + device + inode + mode + uid + gid + size
+ hash + flags_and_file_path_length + file_path;
while (entry.length % 8 != 0) {
// pad with null bytes to a multiple of 8 bytes (64-bits).
entry += '\0';
}
index += entry;
}
index += from_hex(sha1(index));
write(join_paths(current_directory, '.git/index'), index)
}
</textarea>
</section>
@ -1172,12 +1284,19 @@ write('proj/src/main.scm', "(define filesystem '())\n(define current_directory \
git_commit(['README', 'src/main.scm'], 'What an update!');
git_checkout('main');
// update the cache of the working directory. Without this,
// GIT finds an empty cache, and thinks all files are scheduled
// for deletion, until "git add ." allows it to realize that
// the working directory matches the contents of HEAD.
store_index(['README', 'src/main.scm']);
</textarea>
</section>
<section id="conclusion">
<h1>Conclusion</h1>
<p>This article shows that the core of GIT can be re-implemented in a few lines of code.</p>
<p>This article shows that a large part of the core of GIT can be re-implemented in <span id="loc-count">a few</span> lines of code (<a href="javascript:___copy_all_code(); void(0);">copy all the code</a>).</p>
<div id="copy-all-code" style="display: none;"></div>
<ul>
</ul>
@ -1351,7 +1470,34 @@ git_checkout('main');
document.getElementById('hide-eval-' + editor_id).style.display = 'none';
___hilite_off();
}
function ___get_all_code() {
var all = '';
for (var i = 0; i < ___global_editors.length; i++) {
all += ___global_editors[i].getValue();
}
return all;
}
function ___copy_all_code() {
var elem = document.getElementById('copy-all-code');
if (elem.style.display != "none") {
elem.style.display = "none";
} else {
elem.style.display = '';
var elem2 = document.createElement('textarea');
elem.innerHTML = '';
elem.appendChild(elem2);
var all_code = ___get_all_code();
elem2.value = all_code
elem2.focus();
elem2.disabled = false;
elem2.select();
elem2.setSelectionRange(0, elem2.value.length * 10); // for mobile devices?
document.execCommand('copy');
elem2.disabled = true;
}
}
___process_elements();
document.getElementById('loc-count').innerText = ___get_all_code().split('\n').length;
</script>
</body>
</html>