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bitreverse.zig (2762B) - Raw

      1 const std = @import("std");
      2 const builtin = @import("builtin");
      3 const common = @import("common.zig");
      4 
      5 pub const panic = common.panic;
      6 
      7 comptime {
      8     @export(&__bitreversesi2, .{ .name = "__bitreversesi2", .linkage = common.linkage, .visibility = common.visibility });
      9     @export(&__bitreversedi2, .{ .name = "__bitreversedi2", .linkage = common.linkage, .visibility = common.visibility });
     10     @export(&__bitreverseti2, .{ .name = "__bitreverseti2", .linkage = common.linkage, .visibility = common.visibility });
     11 }
     12 
     13 inline fn bitreverseXi2(comptime T: type, a: T) T {
     14     switch (@bitSizeOf(T)) {
     15         32 => {
     16             var t: T = a;
     17             t = ((t >> 1) & 0x55555555) | ((t & 0x55555555) << 1);
     18             t = ((t >> 2) & 0x33333333) | ((t & 0x33333333) << 2);
     19             t = ((t >> 4) & 0x0F0F0F0F) | ((t & 0x0F0F0F0F) << 4);
     20             t = ((t >> 8) & 0x00FF00FF) | ((t & 0x00FF00FF) << 8);
     21             t = (t >> 16) | (t << 16);
     22             return t;
     23         },
     24         64 => {
     25             var t: T = a;
     26             t = ((t >> 1) & 0x5555555555555555) | ((t & 0x5555555555555555) << 1);
     27             t = ((t >> 2) & 0x3333333333333333) | ((t & 0x3333333333333333) << 2);
     28             t = ((t >> 4) & 0x0F0F0F0F0F0F0F0F) | ((t & 0x0F0F0F0F0F0F0F0F) << 4);
     29             t = ((t >> 8) & 0x00FF00FF00FF00FF) | ((t & 0x00FF00FF00FF00FF) << 8);
     30             t = ((t >> 16) & 0x0000FFFF0000FFFF) | ((t & 0x0000FFFF0000FFFF) << 16);
     31             t = (t >> 32) | (t << 32);
     32             return t;
     33         },
     34         128 => {
     35             var t: T = a;
     36             t = ((t >> 1) & 0x55555555555555555555555555555555) | ((t & 0x55555555555555555555555555555555) << 1);
     37             t = ((t >> 2) & 0x33333333333333333333333333333333) | ((t & 0x33333333333333333333333333333333) << 2);
     38             t = ((t >> 4) & 0x0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F) | ((t & 0x0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F) << 4);
     39             t = ((t >> 8) & 0x00FF00FF00FF00FF00FF00FF00FF00FF) | ((t & 0x00FF00FF00FF00FF00FF00FF00FF00FF) << 8);
     40             t = ((t >> 16) & 0x0000FFFF0000FFFF0000FFFF0000FFFF) | ((t & 0x0000FFFF0000FFFF0000FFFF0000FFFF) << 16);
     41             t = ((t >> 32) & 0x00000000FFFFFFFF00000000FFFFFFFF) | ((t & 0x00000000FFFFFFFF00000000FFFFFFFF) << 32);
     42             t = (t >> 64) | (t << 64);
     43             return t;
     44         },
     45         else => unreachable,
     46     }
     47 }
     48 
     49 pub fn __bitreversesi2(a: u32) callconv(.c) u32 {
     50     return bitreverseXi2(u32, a);
     51 }
     52 
     53 pub fn __bitreversedi2(a: u64) callconv(.c) u64 {
     54     return bitreverseXi2(u64, a);
     55 }
     56 
     57 pub fn __bitreverseti2(a: u128) callconv(.c) u128 {
     58     return bitreverseXi2(u128, a);
     59 }
     60 
     61 test {
     62     _ = @import("bitreversesi2_test.zig");
     63     _ = @import("bitreversedi2_test.zig");
     64     _ = @import("bitreverseti2_test.zig");
     65 }