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doc(uint256): bits table #490

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Feb 3, 2025
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doc(uint256): bits table #490

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42 changes: 39 additions & 3 deletions contract/p/gnoswap/uint256/bits_table.gno
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Original file line number Diff line number Diff line change
@@ -1,11 +1,18 @@
// Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Code generated by go run make_tables.go. DO NOT EDIT.

package uint256

// ntz8tab: A lookup table for 8-bit values (0-255) that shows
// the number of trailing zeros (zeros from the rightmost/LSB position).
//
// Example) 0x28 (binary 00101000)
//
// Binary: [ 0 0 1 0 1 0 0 0 ]
// ^^^^^^^^
// 3 consecutive zeros
//
// ntz8tab[0x28] = 3
const ntz8tab = "" +
"\x08\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
"\x04\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
Expand All @@ -24,6 +31,15 @@ const ntz8tab = "" +
"\x05\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00" +
"\x04\x00\x01\x00\x02\x00\x01\x00\x03\x00\x01\x00\x02\x00\x01\x00"

// pop8tab: A lookup table for 8-bit values (0-255) that allows
// quick lookup of the number of set bits (bits set to 1).
//
// Example) 0xB2 (binary 10110010)
//
// Binary: [ 1 0 1 1 0 0 1 0 ]
// Total of 4 set bits
//
// pop8tab[0xB2] = 4
const pop8tab = "" +
"\x00\x01\x01\x02\x01\x02\x02\x03\x01\x02\x02\x03\x02\x03\x03\x04" +
"\x01\x02\x02\x03\x02\x03\x03\x04\x02\x03\x03\x04\x03\x04\x04\x05" +
Expand All @@ -42,6 +58,15 @@ const pop8tab = "" +
"\x03\x04\x04\x05\x04\x05\x05\x06\x04\x05\x05\x06\x05\x06\x06\x07" +
"\x04\x05\x05\x06\x05\x06\x06\x07\x05\x06\x06\x07\x06\x07\x07\x08"

// rev8tab: A lookup table that pre-calculates bit-reversed results
// for 8-bit values (0-255).
//
// Example) 0x16 (binary 00010110)
//
// Binary: [ 0 0 0 1 0 1 1 0 ]
// Reversed: [ 0 1 1 0 1 0 0 0 ] -> 0x68 (104 in decimal)
//
// rev8tab[0x16] = 0x68
const rev8tab = "" +
"\x00\x80\x40\xc0\x20\xa0\x60\xe0\x10\x90\x50\xd0\x30\xb0\x70\xf0" +
"\x08\x88\x48\xc8\x28\xa8\x68\xe8\x18\x98\x58\xd8\x38\xb8\x78\xf8" +
Expand All @@ -60,6 +85,17 @@ const rev8tab = "" +
"\x07\x87\x47\xc7\x27\xa7\x67\xe7\x17\x97\x57\xd7\x37\xb7\x77\xf7" +
"\x0f\x8f\x4f\xcf\x2f\xaf\x6f\xef\x1f\x9f\x5f\xdf\x3f\xbf\x7f\xff"

// len8tab: A lookup table that pre-calculates the "bit length"
// of 8-bit values (0-255).
// (Bit length: position of the most significant bit + 1)
//
// Examples)
//
// 0x00 (binary 00000000) → No MSB → length 0
// 0x01 (binary 00000001) → MSB at rightmost position → length 1
// 0x02 (binary 00000010) ~ 0x03 (00000011) → length 2
// 0x04 (binary 00000100) ~ 0x07 (00000111) → length 3
// ...
const len8tab = "" +
"\x00\x01\x02\x02\x03\x03\x03\x03\x04\x04\x04\x04\x04\x04\x04\x04" +
"\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05\x05" +
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