tiny.quic.connection.stream.ring

1const std = @import("std");23/// Copies the input into the buffer from `index` on, carrying on at the buffer start where it runs4/// off the end. The index sits inside the buffer and the input fits. The sending and receiving5/// parts both buffer stream bytes through this write.6pub fn write(ring: []u8, index: usize, input: []const u8) void {7    std.debug.assert(index < ring.len);8    std.debug.assert(input.len <= ring.len);9    const first = @min(input.len, ring.len - index);10    @memcpy(ring[index..][0..first], input[0..first]);11    @memcpy(ring[0 .. input.len - first], input[first..]);12}1314/// Fills the output from the buffer from `index` on, carrying on at the buffer start where it runs15/// off the end. The index sits inside the buffer and the output fits. The receiving part hands an16/// application its bytes through this read.17pub fn read(ring: []const u8, index: usize, output: []u8) void {18    std.debug.assert(index < ring.len);19    std.debug.assert(output.len <= ring.len);20    const first = @min(output.len, ring.len - index);21    @memcpy(output[0..first], ring[index..][0..first]);22    @memcpy(output[first..], ring[0 .. output.len - first]);23}2425test "ring copies wrap once at the buffer end" {26    var ring: [4]u8 = @splat(0);27    write(&ring, 3, "abc");28    try std.testing.expectEqualSlices(u8, &.{ 'b', 'c', 0, 'a' }, &ring);29    var output: [3]u8 = undefined;30    read(&ring, 3, &output);31    try std.testing.expectEqualStrings("abc", &output);32    write(&ring, 0, "wxyz");33    try std.testing.expectEqualStrings("wxyz", &ring);34}

1pub const ring = @import("ring.zig");