/*
|
* Copyright 2012 ZXing authors
|
*
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
* you may not use this file except in compliance with the License.
|
* You may obtain a copy of the License at
|
*
|
* http://www.apache.org/licenses/LICENSE-2.0
|
*
|
* Unless required by applicable law or agreed to in writing, software
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
* See the License for the specific language governing permissions and
|
* limitations under the License.
|
*/
|
|
#import "ZXIntArray.h"
|
#import "ZXModulusGF.h"
|
#import "ZXModulusPoly.h"
|
#import "ZXPDF417Common.h"
|
|
@interface ZXModulusGF ()
|
|
@property (nonatomic, assign, readonly) int32_t *expTable;
|
@property (nonatomic, assign, readonly) int32_t *logTable;
|
@property (nonatomic, assign, readonly) int modulus;
|
|
@end
|
|
@implementation ZXModulusGF
|
|
+ (ZXModulusGF *)PDF417_GF {
|
static dispatch_once_t pred = 0;
|
__strong static id _mod = nil;
|
dispatch_once(&pred, ^{
|
@autoreleasepool {
|
_mod = [[ZXModulusGF alloc] initWithModulus:ZX_PDF417_NUMBER_OF_CODEWORDS generator:3];
|
}
|
});
|
return _mod;
|
}
|
|
- (id)initWithModulus:(int)modulus generator:(int)generator {
|
if (self = [super init]) {
|
_modulus = modulus;
|
_expTable = (int32_t *)calloc(self.modulus, sizeof(int32_t));
|
_logTable = (int32_t *)calloc(self.modulus, sizeof(int32_t));
|
int32_t x = 1;
|
for (int i = 0; i < modulus; i++) {
|
_expTable[i] = x;
|
x = (x * generator) % modulus;
|
}
|
for (int i = 0; i < self.size - 1; i++) {
|
_logTable[_expTable[i]] = i;
|
}
|
// logTable[0] == 0 but this should never be used
|
_zero = [[ZXModulusPoly alloc] initWithField:self coefficients:[[ZXIntArray alloc] initWithLength:1]];
|
_one = [[ZXModulusPoly alloc] initWithField:self coefficients:[[ZXIntArray alloc] initWithInts:1, -1]];
|
}
|
|
return self;
|
}
|
|
- (ZXModulusPoly *)buildMonomial:(int)degree coefficient:(int)coefficient {
|
if (degree < 0) {
|
[NSException raise:NSInvalidArgumentException format:@"Degree must be greater than 0."];
|
}
|
if (coefficient == 0) {
|
return self.zero;
|
}
|
ZXIntArray *coefficients = [[ZXIntArray alloc] initWithLength:degree + 1];
|
coefficients.array[0] = coefficient;
|
return [[ZXModulusPoly alloc] initWithField:self coefficients:coefficients];
|
}
|
|
- (int)add:(int)a b:(int)b {
|
return (a + b) % self.modulus;
|
}
|
|
- (int)subtract:(int)a b:(int)b {
|
return (self.modulus + a - b) % self.modulus;
|
}
|
|
- (int)exp:(int)a {
|
return _expTable[a];
|
}
|
|
- (int)log:(int)a {
|
if (a == 0) {
|
[NSException raise:NSInvalidArgumentException format:@"Argument must be non-zero."];
|
}
|
return _logTable[a];
|
}
|
|
- (int)inverse:(int)a {
|
if (a == 0) {
|
[NSException raise:NSInvalidArgumentException format:@"Argument must be non-zero."];
|
}
|
|
return _expTable[_modulus - _logTable[a] - 1];
|
}
|
|
- (int)multiply:(int)a b:(int)b {
|
if (a == 0 || b == 0) {
|
return 0;
|
}
|
|
return _expTable[(_logTable[a] + _logTable[b]) % (_modulus - 1)];
|
}
|
|
- (int)size {
|
return self.modulus;
|
}
|
|
@end
|
