a1c965da1e
Sixty-five headers sat side by side in include/, so `#include "irq.h"` said nothing about where irq.h was or what it belonged to, and errno.h, stat.h and fcntl.h at the top shadowed the system's for any host tool built with -I./include. They are in folders now -- arch/ core/ fs/ dev/ gfx/ net/ uapi/ (and ldls/ for the Linux driver layer) -- and every include names the folder, as Linux's do: "core/proc.h". Done mechanically and checked the hard way: the kernel built from this tree disassembles identically to the one built from the tree before it. The full image boots, and userland is the same set of programs. Paths in docs and comments follow; docs/guides/layout.md has a table of what is where, and tools/fix-includes.py rewrites old-style includes from the folders in the tree, for code written before this. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
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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