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Clarify that the size of the GF is a power of two (#1612)

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Frederik van der Els 2023-04-04 23:08:58 +02:00 committed by GitHub
parent f3c2b44e35
commit fc4433ba3c
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1 changed files with 10 additions and 9 deletions
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19
core/src/main/java/com/google/zxing/common/reedsolomon/GenericGF.java
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@ -21,20 +21,21 @@ package com.google.zxing.common.reedsolomon;
* the Galois Fields. Operations use a given primitive polynomial in calculations.</p>
*
* <p>Throughout this package, elements of the GF are represented as an {@code int}
* for convenience and speed (but at the cost of memory).
* </p>
* for convenience and speed (but at the cost of memory).</p>
*
* <p>The size of the GF is assumed to be a power of two.</p>
*
* @author Sean Owen
* @author David Olivier
*/
public final class GenericGF {
public static final GenericGF AZTEC_DATA_12 = new GenericGF(0x1069, 4096, 1); // x^12 + x^6 + x^5 + x^3 + 1
public static final GenericGF AZTEC_DATA_10 = new GenericGF(0x409, 1024, 1); // x^10 + x^3 + 1
public static final GenericGF AZTEC_DATA_6 = new GenericGF(0x43, 64, 1); // x^6 + x + 1
public static final GenericGF AZTEC_PARAM = new GenericGF(0x13, 16, 1); // x^4 + x + 1
public static final GenericGF QR_CODE_FIELD_256 = new GenericGF(0x011D, 256, 0); // x^8 + x^4 + x^3 + x^2 + 1
public static final GenericGF DATA_MATRIX_FIELD_256 = new GenericGF(0x012D, 256, 1); // x^8 + x^5 + x^3 + x^2 + 1
public static final GenericGF AZTEC_DATA_12 = new GenericGF(0b1000001101001, 4096, 1); // x^12 + x^6 + x^5 + x^3 + 1
public static final GenericGF AZTEC_DATA_10 = new GenericGF(0b10000001001, 1024, 1); // x^10 + x^3 + 1
public static final GenericGF AZTEC_DATA_6 = new GenericGF(0b1000011, 64, 1); // x^6 + x + 1
public static final GenericGF AZTEC_PARAM = new GenericGF(0b10011, 16, 1); // x^4 + x + 1
public static final GenericGF QR_CODE_FIELD_256 = new GenericGF(0b100011101, 256, 0); // x^8 + x^4 + x^3 + x^2 + 1
public static final GenericGF DATA_MATRIX_FIELD_256 = new GenericGF(0b100101101, 256, 1); // x^8 + x^5 + x^3 + x^2 + 1
public static final GenericGF AZTEC_DATA_8 = DATA_MATRIX_FIELD_256;
public static final GenericGF MAXICODE_FIELD_64 = AZTEC_DATA_6;
@ -67,7 +68,7 @@ public final class GenericGF {
int x = 1;
for (int i = 0; i < size; i++) {
expTable[i] = x;
x *= 2; // we're assuming the generator alpha is 2
x *= 2; // 2 (the polynomial x) is a primitive element
if (x >= size) {
x ^= primitive;
x &= size - 1;