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Allen Hill
39 lines
1.4 KiB
C
39 lines
1.4 KiB
C
// Copyright (C) 2026 Allen Hill <allenofthehills@gmail.com>
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// SPDX-License-Identifier: GPL-3.0-or-later
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#pragma once
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#include <stddef.h>
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#include <stdint.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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// Generic stdio interface initialization. All user I/O goes through <stdio.h>
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// functions. Assumptions/invariants:
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// - A libc read of stdin blocks the calling task (not the CPU) until at least
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// one byte is available.
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// - stdout is *raw*. There is no '\n' -> "\r\n" translation. The port does not
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// change a bare LF or a binary frame payload. Writes through
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// <stdio.h> and writes through stdio_write_nonblock() must reach the same
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// stream, in order.
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void stdio_init(void);
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// Queue a buffer onto stdout--if it has space, or return false.
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//
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// If stdout cannot accept all `len` bytes now, the function queues
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// a "\n!\n" indicator onto stdout, overwriting the last 3 chars if stdout is
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// full. The caller must not assume that the buffer went out.
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//
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// A port MUST emit that indicator for every dropped buffer, and MUST be able to
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// emit it even if stdout is full. A reader detects the loss as a line that
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// holds only '!'. In the overwrite case the buffer in front of that line is
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// truncated, so a reader MUST tolerate one malformed buffer there. The return
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// value is useful only for diagnostics.
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bool stdio_write_nonblock(const void *buf, uint8_t len);
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#ifdef __cplusplus
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}
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#endif
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