57aff40228
docs/ was ten files where a plan, a description, a guide and a bug report all
sat next to each other. It is now architecture/ (what SchOS is), plan/ (what it
will be), guides/ (how to work on it) and history/ (why it is like this), with
an index that states the one rule holding it together: when something is
finished it moves from plan/ to architecture/ and is rewritten as a description
of the thing rather than a record of building it.
A ticked checkbox says the work happened. It does not say what the work
*produced*, and six months later the checkbox is all that is left. The network
stack proved the point: finished, verified end to end, and for a month the only
description of it anywhere was a checkbox four levels of indentation deep.
So roadmap.md went from 534 lines to 181 -- nothing deleted, the done work
graduated. Seven subsystems that were finished and undescribed now have
descriptions: boot, kernel, syscalls, filesystem, networking, graphics, usb,
init. Every one ends with "What it does not do", which is the section that pays;
a document listing only strengths is marketing, and the reader who needs it most
is the one about to trip over a limitation nobody wrote down.
schfs.md still opened with "phases 1 through 3 1/2 are done, phase 4 is next"
long after all five had landed. It is a description now, with the phase record
and the hard-won bugs moved to history/.
Three corrections found on the way, all load-bearing:
* projects/schcom/README.md claimed SCM_RIGHTS was done. There is no
sendmsg/recvmsg in the kernel at all, and an entire GUI plan rested on it.
* The root README said "No TCP/IP" months after the stack landed.
* history/kernel.md sec.7 was marked "in progress" on a problem that process
groups solved.
Also adds plan/1.0.md, which draws a finish line so the open list stops being
infinite, and marks schwm/ and schde/ superseded: in Wayland the compositor is
the window manager, so that split dissolves rather than being abandoned.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VQ7Qx8E1q1M1bbCq8QLHS2
42 lines
1.9 KiB
C
42 lines
1.9 KiB
C
#pragma once
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// A QR encoder, for getting a crash report off a machine whose network stack is
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// dead.
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//
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// A panic report is worth nothing if it cannot leave the machine, and at panic
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// time there is no network, no filesystem write that can be trusted, and often
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// no second machine on the desk. A phone camera is a working out-of-band
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// channel that needs no drivers on our side at all. See docs/architecture/graphics.md.
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//
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// Deliberately small, in three ways:
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//
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// - Byte mode only. The report is arbitrary bytes; alphanumeric mode would
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// pack tighter but only for a restricted character set.
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// - Error correction level L only. The screen is a clean, evenly lit,
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// high-contrast source -- the failure mode QR's stronger levels protect
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// against (dirt, print damage, curved packaging) does not apply.
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// - Versions 1 to 6 only. Version 7 is where QR starts requiring an extra
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// 18-bit version-information block in two more places on the symbol, and
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// version 10 is where the character count field grows and the alignment
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// pattern grid becomes 2-dimensional. Stopping at 6 avoids both, and
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// 134 bytes is a large crash report.
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//
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// If a payload ever needs more than 134 bytes, the honest fix is to shorten the
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// report -- not to reach for version 10 and its two extra tables.
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#define QR_MAX_VERSION 6
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#define QR_MAX_SIZE (17 + 4 * QR_MAX_VERSION) // 41 modules per side
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#define QR_MAX_BYTES 134
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struct qr {
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int size; // modules per side; 0 if unencoded
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unsigned char mod[QR_MAX_SIZE][QR_MAX_SIZE]; // 1 = dark
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unsigned char fn[QR_MAX_SIZE][QR_MAX_SIZE]; // 1 = function pattern
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};
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// Encode len bytes into q. Picks the smallest version that fits.
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// Returns 0, or -1 if len > QR_MAX_BYTES.
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int qr_encode(struct qr *q, const unsigned char *data, int len);
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// Largest payload, in bytes, for a given version (1..QR_MAX_VERSION).
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int qr_capacity(int version);
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