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Fix CircularBuffer reporting wrong readable/writable length #835

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Merged
mattnite merged 2 commits into from
Jan 5, 2026
Merged

Fix CircularBuffer reporting wrong readable/writable length #835

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a696df2
add some tests for CircularBuffer
Copper280z Jan 4, 2026
15793eb
set buffer.full in write
Copper280z Jan 5, 2026
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24 changes: 23 additions & 1 deletion core/src/utilities.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -602,13 +602,14 @@ pub fn CircularBuffer(comptime T: type, comptime len: usize) type {
pub fn write(buffer: *Self, data: []const u8) error{Full}!void {
buffer.assert_valid();
defer buffer.assert_valid();

for (data) |d| {
if (buffer.full)
return error.Full;

buffer.items[buffer.end] = d;
buffer.increment_end();
if (buffer.start == buffer.end)
buffer.full = true;
}
}

Expand Down Expand Up @@ -639,3 +640,24 @@ pub fn CircularBuffer(comptime T: type, comptime len: usize) type {
}
};
}

test "CircularBuffer bounds" {
const expectEqual = std.testing.expectEqual;
const bufsize: usize = 64;
const FIFO = CircularBuffer(u8, bufsize);
var fifo: FIFO = .empty;
try expectEqual(bufsize, fifo.get_writable_len());

const one_data: [1]u8 = .{42};
try fifo.write(one_data[0..]);
try expectEqual(bufsize - 1, fifo.get_writable_len());
try expectEqual(1, fifo.get_readable_len());

var buf: [100]u8 = undefined;
const big_data = buf[0..];
@memset(big_data, 42);
try expectEqual(big_data.len, 100);
const maybe_err = fifo.write(big_data);

try std.testing.expectError(error.Full, maybe_err);
}
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