85 lines
3.0 KiB
Zig
85 lines
3.0 KiB
Zig
const std = @import("std");
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const builtin = @import("builtin");
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const compiler_rt = @import("../compiler_rt.zig");
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const symbol = compiler_rt.symbol;
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comptime {
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symbol(&__bswapsi2, "__bswapsi2");
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symbol(&__bswapdi2, "__bswapdi2");
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symbol(&__bswapti2, "__bswapti2");
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}
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// bswap - byteswap
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// - bswapXi2 for unoptimized big and little endian
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// ie for u32
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// DE AD BE EF <- little|big endian
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// FE BE AD DE <- big|little endian
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// ff 00 00 00 >> 3*8 (leftmost byte)
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// 00 ff 00 00 >> 1*8 (2nd left byte)
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// 00 00 ff 00 << 1*8 (2n right byte)
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// 00 00 00 ff << 3*8 (rightmost byte)
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inline fn bswapXi2(comptime T: type, a: T) T {
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switch (@bitSizeOf(T)) {
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32 => {
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// zig fmt: off
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return (((a & 0xff000000) >> 24)
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| ((a & 0x00ff0000) >> 8 )
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| ((a & 0x0000ff00) << 8 )
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| ((a & 0x000000ff) << 24));
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// zig fmt: on
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},
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64 => {
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// zig fmt: off
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return (((a & 0xff00000000000000) >> 56)
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| ((a & 0x00ff000000000000) >> 40 )
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| ((a & 0x0000ff0000000000) >> 24 )
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| ((a & 0x000000ff00000000) >> 8 )
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| ((a & 0x00000000ff000000) << 8 )
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| ((a & 0x0000000000ff0000) << 24 )
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| ((a & 0x000000000000ff00) << 40 )
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| ((a & 0x00000000000000ff) << 56));
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// zig fmt: on
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},
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128 => {
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// zig fmt: off
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return (((a & 0xff000000000000000000000000000000) >> 120)
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| ((a & 0x00ff0000000000000000000000000000) >> 104)
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| ((a & 0x0000ff00000000000000000000000000) >> 88 )
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| ((a & 0x000000ff000000000000000000000000) >> 72 )
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| ((a & 0x00000000ff0000000000000000000000) >> 56 )
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| ((a & 0x0000000000ff00000000000000000000) >> 40 )
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| ((a & 0x000000000000ff000000000000000000) >> 24 )
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| ((a & 0x00000000000000ff0000000000000000) >> 8 )
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| ((a & 0x0000000000000000ff00000000000000) << 8 )
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| ((a & 0x000000000000000000ff000000000000) << 24 )
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| ((a & 0x00000000000000000000ff0000000000) << 40 )
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| ((a & 0x0000000000000000000000ff00000000) << 56 )
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| ((a & 0x000000000000000000000000ff000000) << 72 )
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| ((a & 0x00000000000000000000000000ff0000) << 88 )
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| ((a & 0x0000000000000000000000000000ff00) << 104)
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| ((a & 0x000000000000000000000000000000ff) << 120));
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// zig fmt: on
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},
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else => unreachable,
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}
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}
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pub fn __bswapsi2(a: u32) callconv(.c) u32 {
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return bswapXi2(u32, a);
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}
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pub fn __bswapdi2(a: u64) callconv(.c) u64 {
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return bswapXi2(u64, a);
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}
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pub fn __bswapti2(a: u128) callconv(.c) u128 {
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return bswapXi2(u128, a);
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}
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test {
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_ = @import("bswapsi2_test.zig");
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_ = @import("bswapdi2_test.zig");
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_ = @import("bswapti2_test.zig");
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}
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