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decode.c
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/* quirc -- QR-code recognition library
* Copyright (C) 2010-2012 Daniel Beer <dlbeer@gmail.com>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include "quirc_internal.h"
#include <string.h>
#include <stdlib.h>
#define MAX_POLY 64
/************************************************************************
* Galois fields
*/
struct galois_field {
int p;
const uint8_t *log;
const uint8_t *exp;
};
static const uint8_t gf16_exp[16] = {
0x01, 0x02, 0x04, 0x08, 0x03, 0x06, 0x0c, 0x0b,
0x05, 0x0a, 0x07, 0x0e, 0x0f, 0x0d, 0x09, 0x01
};
static const uint8_t gf16_log[16] = {
0x00, 0x0f, 0x01, 0x04, 0x02, 0x08, 0x05, 0x0a,
0x03, 0x0e, 0x09, 0x07, 0x06, 0x0d, 0x0b, 0x0c
};
static const struct galois_field gf16 = {
.p = 15,
.log = gf16_log,
.exp = gf16_exp
};
static const uint8_t gf256_exp[256] = {
0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80,
0x1d, 0x3a, 0x74, 0xe8, 0xcd, 0x87, 0x13, 0x26,
0x4c, 0x98, 0x2d, 0x5a, 0xb4, 0x75, 0xea, 0xc9,
0x8f, 0x03, 0x06, 0x0c, 0x18, 0x30, 0x60, 0xc0,
0x9d, 0x27, 0x4e, 0x9c, 0x25, 0x4a, 0x94, 0x35,
0x6a, 0xd4, 0xb5, 0x77, 0xee, 0xc1, 0x9f, 0x23,
0x46, 0x8c, 0x05, 0x0a, 0x14, 0x28, 0x50, 0xa0,
0x5d, 0xba, 0x69, 0xd2, 0xb9, 0x6f, 0xde, 0xa1,
0x5f, 0xbe, 0x61, 0xc2, 0x99, 0x2f, 0x5e, 0xbc,
0x65, 0xca, 0x89, 0x0f, 0x1e, 0x3c, 0x78, 0xf0,
0xfd, 0xe7, 0xd3, 0xbb, 0x6b, 0xd6, 0xb1, 0x7f,
0xfe, 0xe1, 0xdf, 0xa3, 0x5b, 0xb6, 0x71, 0xe2,
0xd9, 0xaf, 0x43, 0x86, 0x11, 0x22, 0x44, 0x88,
0x0d, 0x1a, 0x34, 0x68, 0xd0, 0xbd, 0x67, 0xce,
0x81, 0x1f, 0x3e, 0x7c, 0xf8, 0xed, 0xc7, 0x93,
0x3b, 0x76, 0xec, 0xc5, 0x97, 0x33, 0x66, 0xcc,
0x85, 0x17, 0x2e, 0x5c, 0xb8, 0x6d, 0xda, 0xa9,
0x4f, 0x9e, 0x21, 0x42, 0x84, 0x15, 0x2a, 0x54,
0xa8, 0x4d, 0x9a, 0x29, 0x52, 0xa4, 0x55, 0xaa,
0x49, 0x92, 0x39, 0x72, 0xe4, 0xd5, 0xb7, 0x73,
0xe6, 0xd1, 0xbf, 0x63, 0xc6, 0x91, 0x3f, 0x7e,
0xfc, 0xe5, 0xd7, 0xb3, 0x7b, 0xf6, 0xf1, 0xff,
0xe3, 0xdb, 0xab, 0x4b, 0x96, 0x31, 0x62, 0xc4,
0x95, 0x37, 0x6e, 0xdc, 0xa5, 0x57, 0xae, 0x41,
0x82, 0x19, 0x32, 0x64, 0xc8, 0x8d, 0x07, 0x0e,
0x1c, 0x38, 0x70, 0xe0, 0xdd, 0xa7, 0x53, 0xa6,
0x51, 0xa2, 0x59, 0xb2, 0x79, 0xf2, 0xf9, 0xef,
0xc3, 0x9b, 0x2b, 0x56, 0xac, 0x45, 0x8a, 0x09,
0x12, 0x24, 0x48, 0x90, 0x3d, 0x7a, 0xf4, 0xf5,
0xf7, 0xf3, 0xfb, 0xeb, 0xcb, 0x8b, 0x0b, 0x16,
0x2c, 0x58, 0xb0, 0x7d, 0xfa, 0xe9, 0xcf, 0x83,
0x1b, 0x36, 0x6c, 0xd8, 0xad, 0x47, 0x8e, 0x01
};
static const uint8_t gf256_log[256] = {
0x00, 0xff, 0x01, 0x19, 0x02, 0x32, 0x1a, 0xc6,
0x03, 0xdf, 0x33, 0xee, 0x1b, 0x68, 0xc7, 0x4b,
0x04, 0x64, 0xe0, 0x0e, 0x34, 0x8d, 0xef, 0x81,
0x1c, 0xc1, 0x69, 0xf8, 0xc8, 0x08, 0x4c, 0x71,
0x05, 0x8a, 0x65, 0x2f, 0xe1, 0x24, 0x0f, 0x21,
0x35, 0x93, 0x8e, 0xda, 0xf0, 0x12, 0x82, 0x45,
0x1d, 0xb5, 0xc2, 0x7d, 0x6a, 0x27, 0xf9, 0xb9,
0xc9, 0x9a, 0x09, 0x78, 0x4d, 0xe4, 0x72, 0xa6,
0x06, 0xbf, 0x8b, 0x62, 0x66, 0xdd, 0x30, 0xfd,
0xe2, 0x98, 0x25, 0xb3, 0x10, 0x91, 0x22, 0x88,
0x36, 0xd0, 0x94, 0xce, 0x8f, 0x96, 0xdb, 0xbd,
0xf1, 0xd2, 0x13, 0x5c, 0x83, 0x38, 0x46, 0x40,
0x1e, 0x42, 0xb6, 0xa3, 0xc3, 0x48, 0x7e, 0x6e,
0x6b, 0x3a, 0x28, 0x54, 0xfa, 0x85, 0xba, 0x3d,
0xca, 0x5e, 0x9b, 0x9f, 0x0a, 0x15, 0x79, 0x2b,
0x4e, 0xd4, 0xe5, 0xac, 0x73, 0xf3, 0xa7, 0x57,
0x07, 0x70, 0xc0, 0xf7, 0x8c, 0x80, 0x63, 0x0d,
0x67, 0x4a, 0xde, 0xed, 0x31, 0xc5, 0xfe, 0x18,
0xe3, 0xa5, 0x99, 0x77, 0x26, 0xb8, 0xb4, 0x7c,
0x11, 0x44, 0x92, 0xd9, 0x23, 0x20, 0x89, 0x2e,
0x37, 0x3f, 0xd1, 0x5b, 0x95, 0xbc, 0xcf, 0xcd,
0x90, 0x87, 0x97, 0xb2, 0xdc, 0xfc, 0xbe, 0x61,
0xf2, 0x56, 0xd3, 0xab, 0x14, 0x2a, 0x5d, 0x9e,
0x84, 0x3c, 0x39, 0x53, 0x47, 0x6d, 0x41, 0xa2,
0x1f, 0x2d, 0x43, 0xd8, 0xb7, 0x7b, 0xa4, 0x76,
0xc4, 0x17, 0x49, 0xec, 0x7f, 0x0c, 0x6f, 0xf6,
0x6c, 0xa1, 0x3b, 0x52, 0x29, 0x9d, 0x55, 0xaa,
0xfb, 0x60, 0x86, 0xb1, 0xbb, 0xcc, 0x3e, 0x5a,
0xcb, 0x59, 0x5f, 0xb0, 0x9c, 0xa9, 0xa0, 0x51,
0x0b, 0xf5, 0x16, 0xeb, 0x7a, 0x75, 0x2c, 0xd7,
0x4f, 0xae, 0xd5, 0xe9, 0xe6, 0xe7, 0xad, 0xe8,
0x74, 0xd6, 0xf4, 0xea, 0xa8, 0x50, 0x58, 0xaf
};
static const struct galois_field gf256 = {
.p = 255,
.log = gf256_log,
.exp = gf256_exp
};
/************************************************************************
* Polynomial operations
*/
static void poly_add(uint8_t *dst, const uint8_t *src, uint8_t c,
int shift, const struct galois_field *gf)
{
int i;
int log_c = gf->log[c];
if (!c)
return;
for (i = 0; i < MAX_POLY; i++) {
int p = i + shift;
uint8_t v = src[i];
if (p < 0 || p >= MAX_POLY)
continue;
if (!v)
continue;
dst[p] ^= gf->exp[(gf->log[v] + log_c) % gf->p];
}
}
static uint8_t poly_eval(const uint8_t *s, uint8_t x,
const struct galois_field *gf)
{
int i;
uint8_t sum = 0;
uint8_t log_x = gf->log[x];
if (!x)
return s[0];
for (i = 0; i < MAX_POLY; i++) {
uint8_t c = s[i];
if (!c)
continue;
sum ^= gf->exp[(gf->log[c] + log_x * i) % gf->p];
}
return sum;
}
/************************************************************************
* Berlekamp-Massey algorithm for finding error locator polynomials.
*/
static void berlekamp_massey(const uint8_t *s, int N,
const struct galois_field *gf,
uint8_t *sigma)
{
uint8_t C[MAX_POLY];
uint8_t B[MAX_POLY];
int L = 0;
int m = 1;
uint8_t b = 1;
int n;
memset(B, 0, sizeof(B));
memset(C, 0, sizeof(C));
B[0] = 1;
C[0] = 1;
for (n = 0; n < N; n++) {
uint8_t d = s[n];
uint8_t mult;
int i;
for (i = 1; i <= L; i++) {
if (!(C[i] && s[n - i]))
continue;
d ^= gf->exp[(gf->log[C[i]] +
gf->log[s[n - i]]) %
gf->p];
}
mult = gf->exp[(gf->p - gf->log[b] + gf->log[d]) % gf->p];
if (!d) {
m++;
} else if (L * 2 <= n) {
uint8_t T[MAX_POLY];
memcpy(T, C, sizeof(T));
poly_add(C, B, mult, m, gf);
memcpy(B, T, sizeof(B));
L = n + 1 - L;
b = d;
m = 1;
} else {
poly_add(C, B, mult, m, gf);
m++;
}
}
memcpy(sigma, C, MAX_POLY);
}
/************************************************************************
* Code stream error correction
*
* Generator polynomial for GF(2^8) is x^8 + x^4 + x^3 + x^2 + 1
*/
static int block_syndromes(const uint8_t *data, int bs, int npar, uint8_t *s)
{
int nonzero = 0;
int i;
memset(s, 0, MAX_POLY);
for (i = 0; i < npar; i++) {
int j;
for (j = 0; j < bs; j++) {
uint8_t c = data[bs - j - 1];
if (!c)
continue;
s[i] ^= gf256_exp[((int)gf256_log[c] +
i * j) % 255];
}
if (s[i])
nonzero = 1;
}
return nonzero;
}
static void eloc_poly(uint8_t *omega,
const uint8_t *s, const uint8_t *sigma,
int npar)
{
int i;
memset(omega, 0, MAX_POLY);
for (i = 0; i < npar; i++) {
const uint8_t a = sigma[i];
const uint8_t log_a = gf256_log[a];
int j;
if (!a)
continue;
for (j = 0; j + 1 < MAX_POLY; j++) {
const uint8_t b = s[j + 1];
if (i + j >= npar)
break;
if (!b)
continue;
omega[i + j] ^=
gf256_exp[(log_a + gf256_log[b]) % 255];
}
}
}
static quirc_decode_error_t correct_block(uint8_t *data,
const struct quirc_rs_params *ecc)
{
int npar = ecc->bs - ecc->dw;
uint8_t s[MAX_POLY];
uint8_t sigma[MAX_POLY];
uint8_t sigma_deriv[MAX_POLY];
uint8_t omega[MAX_POLY];
int i;
/* Compute syndrome vector */
if (!block_syndromes(data, ecc->bs, npar, s))
return QUIRC_SUCCESS;
berlekamp_massey(s, npar, &gf256, sigma);
/* Compute derivative of sigma */
memset(sigma_deriv, 0, MAX_POLY);
for (i = 0; i + 1 < MAX_POLY; i += 2)
sigma_deriv[i] = sigma[i + 1];
/* Compute error evaluator polynomial */
eloc_poly(omega, s, sigma, npar - 1);
/* Find error locations and magnitudes */
for (i = 0; i < ecc->bs; i++) {
uint8_t xinv = gf256_exp[255 - i];
if (!poly_eval(sigma, xinv, &gf256)) {
uint8_t sd_x = poly_eval(sigma_deriv, xinv, &gf256);
uint8_t omega_x = poly_eval(omega, xinv, &gf256);
uint8_t error = gf256_exp[(255 - gf256_log[sd_x] +
gf256_log[omega_x]) % 255];
data[ecc->bs - i - 1] ^= error;
}
}
if (block_syndromes(data, ecc->bs, npar, s))
return QUIRC_ERROR_DATA_ECC;
return QUIRC_SUCCESS;
}
/************************************************************************
* Format value error correction
*
* Generator polynomial for GF(2^4) is x^4 + x + 1
*/
#define FORMAT_MAX_ERROR 3
#define FORMAT_SYNDROMES (FORMAT_MAX_ERROR * 2)
#define FORMAT_BITS 15
static int format_syndromes(uint16_t u, uint8_t *s)
{
int i;
int nonzero = 0;
memset(s, 0, MAX_POLY);
for (i = 0; i < FORMAT_SYNDROMES; i++) {
int j;
s[i] = 0;
for (j = 0; j < FORMAT_BITS; j++)
if (u & (1 << j))
s[i] ^= gf16_exp[((i + 1) * j) % 15];
if (s[i])
nonzero = 1;
}
return nonzero;
}
static quirc_decode_error_t correct_format(uint16_t *f_ret)
{
uint16_t u = *f_ret;
int i;
uint8_t s[MAX_POLY];
uint8_t sigma[MAX_POLY];
/* Evaluate U (received codeword) at each of alpha_1 .. alpha_6
* to get S_1 .. S_6 (but we index them from 0).
*/
if (!format_syndromes(u, s))
return QUIRC_SUCCESS;
berlekamp_massey(s, FORMAT_SYNDROMES, &gf16, sigma);
/* Now, find the roots of the polynomial */
for (i = 0; i < 15; i++)
if (!poly_eval(sigma, gf16_exp[15 - i], &gf16))
u ^= (1 << i);
if (format_syndromes(u, s))
return QUIRC_ERROR_FORMAT_ECC;
*f_ret = u;
return QUIRC_SUCCESS;
}
/************************************************************************
* Decoder algorithm
*/
struct datastream {
uint8_t *raw;
int data_bits;
int ptr;
uint8_t data[QUIRC_MAX_PAYLOAD];
};
static inline int grid_bit(const struct quirc_code *code, int x, int y)
{
int p = y * code->size + x;
return (code->cell_bitmap[p >> 3] >> (p & 7)) & 1;
}
static quirc_decode_error_t read_format(const struct quirc_code *code,
struct quirc_data *data, int which)
{
int i;
uint16_t format = 0;
uint16_t fdata;
quirc_decode_error_t err;
if (which) {
for (i = 0; i < 7; i++)
format = (format << 1) |
grid_bit(code, 8, code->size - 1 - i);
for (i = 0; i < 8; i++)
format = (format << 1) |
grid_bit(code, code->size - 8 + i, 8);
} else {
static const int xs[15] = {
8, 8, 8, 8, 8, 8, 8, 8, 7, 5, 4, 3, 2, 1, 0
};
static const int ys[15] = {
0, 1, 2, 3, 4, 5, 7, 8, 8, 8, 8, 8, 8, 8, 8
};
for (i = 14; i >= 0; i--)
format = (format << 1) | grid_bit(code, xs[i], ys[i]);
}
format ^= 0x5412;
err = correct_format(&format);
if (err)
return err;
fdata = format >> 10;
data->ecc_level = fdata >> 3;
data->mask = fdata & 7;
return QUIRC_SUCCESS;
}
static int mask_bit(int mask, int i, int j)
{
switch (mask) {
case 0: return !((i + j) % 2);
case 1: return !(i % 2);
case 2: return !(j % 3);
case 3: return !((i + j) % 3);
case 4: return !(((i / 2) + (j / 3)) % 2);
case 5: return !((i * j) % 2 + (i * j) % 3);
case 6: return !(((i * j) % 2 + (i * j) % 3) % 2);
case 7: return !(((i * j) % 3 + (i + j) % 2) % 2);
}
return 0;
}
static int reserved_cell(int version, int i, int j)
{
const struct quirc_version_info *ver = &quirc_version_db[version];
int size = version * 4 + 17;
int ai = -1, aj = -1, a;
/* Finder + format: top left */
if (i < 9 && j < 9)
return 1;
/* Finder + format: bottom left */
if (i + 8 >= size && j < 9)
return 1;
/* Finder + format: top right */
if (i < 9 && j + 8 >= size)
return 1;
/* Exclude timing patterns */
if (i == 6 || j == 6)
return 1;
/* Exclude version info, if it exists. Version info sits adjacent to
* the top-right and bottom-left finders in three rows, bounded by
* the timing pattern.
*/
if (version >= 7) {
if (i < 6 && j + 11 >= size)
return 1;
if (i + 11 >= size && j < 6)
return 1;
}
/* Exclude alignment patterns */
for (a = 0; a < QUIRC_MAX_ALIGNMENT && ver->apat[a]; a++) {
int p = ver->apat[a];
if (abs(p - i) < 3)
ai = a;
if (abs(p - j) < 3)
aj = a;
}
if (ai >= 0 && aj >= 0) {
a--;
if (ai > 0 && ai < a)
return 1;
if (aj > 0 && aj < a)
return 1;
if (aj == a && ai == a)
return 1;
}
return 0;
}
static void read_bit(const struct quirc_code *code,
struct quirc_data *data,
struct datastream *ds, int i, int j)
{
int bitpos = ds->data_bits & 7;
int bytepos = ds->data_bits >> 3;
int v = grid_bit(code, j, i);
if (mask_bit(data->mask, i, j))
v ^= 1;
if (v)
ds->raw[bytepos] |= (0x80 >> bitpos);
ds->data_bits++;
}
static void read_data(const struct quirc_code *code,
struct quirc_data *data,
struct datastream *ds)
{
int y = code->size - 1;
int x = code->size - 1;
int dir = -1;
while (x > 0) {
if (x == 6)
x--;
if (!reserved_cell(data->version, y, x))
read_bit(code, data, ds, y, x);
if (!reserved_cell(data->version, y, x - 1))
read_bit(code, data, ds, y, x - 1);
y += dir;
if (y < 0 || y >= code->size) {
dir = -dir;
x -= 2;
y += dir;
}
}
}
static quirc_decode_error_t codestream_ecc(struct quirc_data *data,
struct datastream *ds)
{
const struct quirc_version_info *ver =
&quirc_version_db[data->version];
const struct quirc_rs_params *sb_ecc = &ver->ecc[data->ecc_level];
struct quirc_rs_params lb_ecc;
const int lb_count =
(ver->data_bytes - sb_ecc->bs * sb_ecc->ns) / (sb_ecc->bs + 1);
const int bc = lb_count + sb_ecc->ns;
const int ecc_offset = sb_ecc->dw * bc + lb_count;
int dst_offset = 0;
int i;
memcpy(&lb_ecc, sb_ecc, sizeof(lb_ecc));
lb_ecc.dw++;
lb_ecc.bs++;
for (i = 0; i < bc; i++) {
uint8_t *dst = ds->data + dst_offset;
const struct quirc_rs_params *ecc =
(i < sb_ecc->ns) ? sb_ecc : &lb_ecc;
const int num_ec = ecc->bs - ecc->dw;
quirc_decode_error_t err;
int j;
for (j = 0; j < ecc->dw; j++)
dst[j] = ds->raw[j * bc + i];
for (j = 0; j < num_ec; j++)
dst[ecc->dw + j] = ds->raw[ecc_offset + j * bc + i];
err = correct_block(dst, ecc);
if (err)
return err;
dst_offset += ecc->dw;
}
ds->data_bits = dst_offset * 8;
return QUIRC_SUCCESS;
}
static inline int bits_remaining(const struct datastream *ds)
{
return ds->data_bits - ds->ptr;
}
static int take_bits(struct datastream *ds, int len)
{
int ret = 0;
while (len && (ds->ptr < ds->data_bits)) {
uint8_t b = ds->data[ds->ptr >> 3];
int bitpos = ds->ptr & 7;
ret <<= 1;
if ((b << bitpos) & 0x80)
ret |= 1;
ds->ptr++;
len--;
}
return ret;
}
static int numeric_tuple(struct quirc_data *data,
struct datastream *ds,
int bits, int digits)
{
int tuple;
int i;
if (bits_remaining(ds) < bits)
return -1;
tuple = take_bits(ds, bits);
for (i = digits - 1; i >= 0; i--) {
data->payload[data->payload_len + i] = tuple % 10 + '0';
tuple /= 10;
}
data->payload_len += digits;
return 0;
}
static quirc_decode_error_t decode_numeric(struct quirc_data *data,
struct datastream *ds)
{
int bits = 14;
int count;
if (data->version < 10)
bits = 10;
else if (data->version < 27)
bits = 12;
count = take_bits(ds, bits);
if (data->payload_len + count + 1 > QUIRC_MAX_PAYLOAD)
return QUIRC_ERROR_DATA_OVERFLOW;
while (count >= 3) {
if (numeric_tuple(data, ds, 10, 3) < 0)
return QUIRC_ERROR_DATA_UNDERFLOW;
count -= 3;
}
if (count >= 2) {
if (numeric_tuple(data, ds, 7, 2) < 0)
return QUIRC_ERROR_DATA_UNDERFLOW;
count -= 2;
}
if (count) {
if (numeric_tuple(data, ds, 4, 1) < 0)
return QUIRC_ERROR_DATA_UNDERFLOW;
count--;
}
return QUIRC_SUCCESS;
}
static int alpha_tuple(struct quirc_data *data,
struct datastream *ds,
int bits, int digits)
{
int tuple;
int i;
if (bits_remaining(ds) < bits)
return -1;
tuple = take_bits(ds, bits);
for (i = 0; i < digits; i++) {
static const char *alpha_map =
"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:";
data->payload[data->payload_len + digits - i - 1] =
alpha_map[tuple % 45];
tuple /= 45;
}
data->payload_len += digits;
return 0;
}
static quirc_decode_error_t decode_alpha(struct quirc_data *data,
struct datastream *ds)
{
int bits = 13;
int count;
if (data->version < 10)
bits = 9;
else if (data->version < 27)
bits = 11;
count = take_bits(ds, bits);
if (data->payload_len + count + 1 > QUIRC_MAX_PAYLOAD)
return QUIRC_ERROR_DATA_OVERFLOW;
while (count >= 2) {
if (alpha_tuple(data, ds, 11, 2) < 0)
return QUIRC_ERROR_DATA_UNDERFLOW;
count -= 2;
}
if (count) {
if (alpha_tuple(data, ds, 6, 1) < 0)
return QUIRC_ERROR_DATA_UNDERFLOW;
count--;
}
return QUIRC_SUCCESS;
}
static quirc_decode_error_t decode_byte(struct quirc_data *data,
struct datastream *ds)
{
int bits = 16;
int count;
int i;
if (data->version < 10)
bits = 8;
count = take_bits(ds, bits);
if (data->payload_len + count + 1 > QUIRC_MAX_PAYLOAD)
return QUIRC_ERROR_DATA_OVERFLOW;
if (bits_remaining(ds) < count * 8)
return QUIRC_ERROR_DATA_UNDERFLOW;
for (i = 0; i < count; i++)
data->payload[data->payload_len++] = take_bits(ds, 8);
return QUIRC_SUCCESS;
}
static quirc_decode_error_t decode_kanji(struct quirc_data *data,
struct datastream *ds)
{
int bits = 12;
int count;
int i;
if (data->version < 10)
bits = 8;
else if (data->version < 27)
bits = 10;
count = take_bits(ds, bits);
if (data->payload_len + count * 2 + 1 > QUIRC_MAX_PAYLOAD)
return QUIRC_ERROR_DATA_OVERFLOW;
if (bits_remaining(ds) < count * 13)
return QUIRC_ERROR_DATA_UNDERFLOW;
for (i = 0; i < count; i++) {
int d = take_bits(ds, 13);
int msB = d / 0xc0;
int lsB = d % 0xc0;
int intermediate = (msB << 8) | lsB;
uint16_t sjw;
if (intermediate + 0x8140 <= 0x9ffc) {
/* bytes are in the range 0x8140 to 0x9FFC */
sjw = intermediate + 0x8140;
} else {
/* bytes are in the range 0xE040 to 0xEBBF */
sjw = intermediate + 0xc140;
}
data->payload[data->payload_len++] = sjw >> 8;
data->payload[data->payload_len++] = sjw & 0xff;
}
return QUIRC_SUCCESS;
}
static quirc_decode_error_t decode_eci(struct quirc_data *data,
struct datastream *ds)
{
if (bits_remaining(ds) < 8)
return QUIRC_ERROR_DATA_UNDERFLOW;
data->eci = take_bits(ds, 8);
if ((data->eci & 0xc0) == 0x80) {
if (bits_remaining(ds) < 8)
return QUIRC_ERROR_DATA_UNDERFLOW;
data->eci = (data->eci << 8) | take_bits(ds, 8);
} else if ((data->eci & 0xe0) == 0xc0) {
if (bits_remaining(ds) < 16)
return QUIRC_ERROR_DATA_UNDERFLOW;
data->eci = (data->eci << 16) | take_bits(ds, 16);
}
return QUIRC_SUCCESS;
}
static quirc_decode_error_t decode_payload(struct quirc_data *data,
struct datastream *ds)
{
while (bits_remaining(ds) >= 4) {
quirc_decode_error_t err = QUIRC_SUCCESS;
int type = take_bits(ds, 4);
switch (type) {
case QUIRC_DATA_TYPE_NUMERIC:
err = decode_numeric(data, ds);
break;
case QUIRC_DATA_TYPE_ALPHA:
err = decode_alpha(data, ds);
break;
case QUIRC_DATA_TYPE_BYTE:
err = decode_byte(data, ds);
break;
case QUIRC_DATA_TYPE_KANJI:
err = decode_kanji(data, ds);
break;
case 7:
err = decode_eci(data, ds);
break;
default:
goto done;
}
if (err)
return err;
if (!(type & (type - 1)) && (type > data->data_type))
data->data_type = type;
}
done:
/* Add nul terminator to all payloads */
if (data->payload_len >= (int) sizeof(data->payload))
data->payload_len--;
data->payload[data->payload_len] = 0;
return QUIRC_SUCCESS;
}
quirc_decode_error_t quirc_decode(const struct quirc_code *code,
struct quirc_data *data)
{
quirc_decode_error_t err;
struct datastream ds;
if (code->size > QUIRC_MAX_GRID_SIZE)
return QUIRC_ERROR_INVALID_GRID_SIZE;
if ((code->size - 17) % 4)
return QUIRC_ERROR_INVALID_GRID_SIZE;
memset(data, 0, sizeof(*data));
memset(&ds, 0, sizeof(ds));
data->version = (code->size - 17) / 4;
if (data->version < 1 ||
data->version > QUIRC_MAX_VERSION)
return QUIRC_ERROR_INVALID_VERSION;
/* Read format information -- try both locations */
err = read_format(code, data, 0);
if (err)
err = read_format(code, data, 1);
if (err)
return err;
/*
* Borrow data->payload to store the raw bits.
* It's only used during read_data + coddestream_ecc below.
*
* This trick saves the size of struct datastream, which we allocate
* on the stack.
*/
ds.raw = data->payload;
read_data(code, data, &ds);
err = codestream_ecc(data, &ds);
if (err)
return err;
ds.raw = NULL; /* We've done with this buffer. */
err = decode_payload(data, &ds);
if (err)
return err;
return QUIRC_SUCCESS;
}
void quirc_flip(struct quirc_code *code)
{
struct quirc_code flipped = {0};
unsigned int offset = 0;
for (int y = 0; y < code->size; y++) {
for (int x = 0; x < code->size; x++) {
if (grid_bit(code, y, x)) {
flipped.cell_bitmap[offset >> 3u] |= (1u << (offset & 7u));
}
offset++;
}
}
memcpy(&code->cell_bitmap, &flipped.cell_bitmap, sizeof(flipped.cell_bitmap));
}