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#include <limits.h>
#include <stdlib.h>
#include "code-common.h"
#include "code-layout.h"
struct qr_iterator {
struct qr_code * code;
int dim;
int column;
int row;
int up;
int mask;
unsigned char * p;
};
static int is_data_bit(const struct qr_iterator * i)
{
if (i->row == 6 || i->column == 6) /* timing */
return 0;
if (i->column < 9 && i->row < 9) /* top-left */
return 0;
if (i->column >= i->dim - 8 && i->row < 9) /* top-right */
return 0;
if (i->column < 9 && i->row >= i->dim - 8) /* bottom-left */
return 0;
/* XXX: format data */
/* XXX: alignment pattern */
return 1;
}
static void set_pointer(struct qr_iterator * i)
{
i->mask = 1 << (i->column % CHAR_BIT);
i->p = i->code->modules->bits
+ i->code->modules->stride * i->row
+ i->column / CHAR_BIT;
}
static void advance(struct qr_iterator * i)
{
do {
/* This XOR is to account for the vertical strip of
* timing bits in column 6 which displaces everything.
*/
if ((i->column < 6) ^ !(i->column % 2)) {
/* Right-hand part or at left edge */
i->column -= 1;
} else {
/* Left-hand part */
i->column += 1;
if (( i->up && i->row == 0) ||
(!i->up && i->row == i->dim - 1)) {
/* Hit the top / bottom */
i->column -= 2;
i->up = !i->up;
} else {
i->row += i->up ? -1 : 1;
}
}
if (i->column < 0)
continue; /* don't go off left edge */
/* Check for one-past-end */
if (i->column == 0 && i->row >= i->dim - 8)
break;
} while (!is_data_bit(i));
set_pointer(i);
}
struct qr_iterator * qr_layout_begin(struct qr_code * code)
{
struct qr_iterator * i;
i = malloc(sizeof(*i));
if (i) {
i->dim = code_side_length(code->format);
i->code = code;
i->column = i->dim - 1;
i->row = i->dim - 1;
i->up = 1;
set_pointer(i);
}
return i;
}
void qr_layout_end(struct qr_iterator * i)
{
free(i);
}
unsigned int qr_layout_read(struct qr_iterator * i)
{
unsigned int x = 0;
int b;
for (b = 0; b < 8; ++b) {
x |= (*i->p & i->mask) ? 1 : 0;
advance(i);
x <<= 1;
}
return x;
}
void qr_layout_write(struct qr_iterator * i, unsigned int x)
{
int b;
for (b = 0; b < 8; ++b) {
*i->p |= (x & 0x80) ? i->mask : 0;
advance(i);
x <<= 1;
}
}
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