diff options
Diffstat (limited to 'lpg/libqr/code-parse.c')
| -rw-r--r-- | lpg/libqr/code-parse.c | 312 |
1 files changed, 308 insertions, 4 deletions
diff --git a/lpg/libqr/code-parse.c b/lpg/libqr/code-parse.c index a794cdc..50d621c 100644 --- a/lpg/libqr/code-parse.c +++ b/lpg/libqr/code-parse.c @@ -1,10 +1,314 @@ +#include <assert.h> +#include <limits.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> + +#include <qr/bitmap.h> +#include <qr/bitstream.h> #include <qr/code.h> +#include <qr/data.h> +#include <qr/layout.h> +#include <qr/parse.h> + +#include "constants.h" +#include "galois.h" + +/* XXX: duplicated */ +static int get_px(const struct qr_bitmap * bmp, int x, int y) +{ + size_t off = y * bmp->stride + x / CHAR_BIT; + unsigned char bit = 1 << (x % CHAR_BIT); + + return bmp->bits[off] & bit; +} + +static int unpack_bits(int version, + enum qr_ec_level ec, + struct qr_bitstream * raw_bits, + struct qr_bitstream * bits_out) +{ + /* FIXME: less math here (get the values from a common helper fn) */ + /* FIXME: more comments to explain the algorithm */ + + const size_t total_bits = qr_code_total_capacity(version); + const size_t total_words = total_bits / 8; + const size_t total_data = QR_DATA_WORD_COUNT[version - 1][ec ^ 0x1]; + int total_blocks, block_count[2], row_length[2], data_words, rs_words; + int i, w, block; + struct qr_bitstream ** blocks = 0; + + /* copied from make_data */ + block_count[0] = QR_RS_BLOCK_COUNT[version - 1][ec ^ 0x1][0]; + block_count[1] = QR_RS_BLOCK_COUNT[version - 1][ec ^ 0x1][1]; + total_blocks = block_count[0] + block_count[1]; + data_words = total_data / total_blocks; + rs_words = total_words / total_blocks - data_words; + assert((data_words + rs_words) * block_count[0] + + (data_words + rs_words + 1) * block_count[1] == total_words); + + blocks = calloc(total_blocks, sizeof(*blocks)); + /* XXX: check return (and below) */ + + for (i = 0; i < total_blocks; ++i) + blocks[i] = qr_bitstream_create(); + + /* Read in the data & EC (see spec table 19) */ + + qr_bitstream_seek(raw_bits, 0); + + /* XXX: 14-M will be incorrect */ + row_length[0] = data_words; + row_length[1] = block_count[1] > 0 ? (total_data - row_length[0] * block_count[0]) / block_count[1] : 0; + + fprintf(stderr, "block counts %d and %d\n", block_count[0], block_count[1]); + fprintf(stderr, "row lengths %d and %d\n", row_length[0], row_length[1]); + + block = 0; + for (w = 0; w < total_words; ++w) { + if (block == 0 && w / total_blocks == row_length[0] && block_count[1] != 0) { + /* Skip the short blocks, if there are any */ + block += block_count[0]; + } + qr_bitstream_write(blocks[block], qr_bitstream_read(raw_bits, 8), 8); + block = (block + 1) % total_blocks; + } + + /* XXX: apply ec */ + + for (block = 0; block < total_blocks; ++block) { + struct qr_bitstream * stream = blocks[block]; + qr_bitstream_seek(stream, 0); + for (w = 0; w < row_length[block >= block_count[0]]; ++w) + qr_bitstream_write(bits_out, + qr_bitstream_read(stream, 8), + 8); + qr_bitstream_destroy(stream); + } + free(blocks); + + return 0; +} -struct qr_code * qr_code_parse(const void * buffer, - size_t line_bits, - size_t line_stride, - size_t line_count) +static int read_bits(const struct qr_code * code, + enum qr_ec_level ec, + struct qr_bitstream * data_bits) { + const size_t total_bits = qr_code_total_capacity(code->version); + const size_t total_words = total_bits / 8; + struct qr_bitstream * raw_bits; + struct qr_iterator * layout; + int w; + int ret; + + raw_bits = qr_bitstream_create(); + layout = qr_layout_begin((struct qr_code *) code); /* dropping const! */ + for (w = 0; w < total_words; ++w) + qr_bitstream_write(raw_bits, qr_layout_read(layout), 8); + qr_layout_end(layout); + + ret = unpack_bits(code->version, ec, raw_bits, data_bits); + qr_bitstream_destroy(raw_bits); + + return ret; +} + +static int read_format(const struct qr_bitmap * bmp, enum qr_ec_level * ec, int * mask) +{ + int dim; + int i; + unsigned bits1, bits2; + enum qr_ec_level ec1, ec2; + int mask1, mask2; + int err1, err2; + + dim = bmp->width; + bits1 = bits2 = 0; + + for (i = 14; i >= 8; --i) { + bits1 = (bits1 << 1) | !!get_px(bmp, 14 - i + (i <= 8), 8); + bits2 = (bits2 << 1) | !!get_px(bmp, 8, dim - 1 - (14 - i)); + } + + for (; i >= 0; --i) { + bits1 = (bits1 << 1) | !!get_px(bmp, 8, i + (i >= 6)); + bits2 = (bits2 << 1) | !!get_px(bmp, dim - 1 - i, 8); + } + + fprintf(stderr, "read format bits %x / %x\n", bits1, bits2); + + err1 = qr_decode_format(bits1, &ec1, &mask1); + err2 = qr_decode_format(bits2, &ec2, &mask2); + + if (err1 < 0 && err2 < 0) + return -1; + + if (err1 < err2) + *ec = ec1, *mask = mask1; + else + *ec = ec2, *mask = mask2; + return 0; } +static int read_version(const struct qr_bitmap * bmp) +{ + int dim; + int i; + unsigned long bits1, bits2; + int ver1, ver2; + int err1, err2; + + dim = bmp->width; + bits1 = bits2 = 0; + + for (i = 17; i >= 0; --i) { + bits1 = (bits1 << 1) | !!get_px(bmp, i / 3, dim - 11 + (i % 3)); + bits2 = (bits2 << 1) | !!get_px(bmp, dim - 11 + (i % 3), i / 3); + } + + fprintf(stderr, "read version bits %lx / %lx\n", bits1, bits2); + + err1 = qr_decode_version(bits1, &ver1); + err2 = qr_decode_version(bits2, &ver2); + + fprintf(stderr, "got versions %d[%d] / %d[%d]\n", ver1, err1, ver2, err2); + + if (err1 < 0 && err2 < 0) + return -1; + + return err1 < err2 ? ver1 : ver2; +} + +int qr_code_parse(const void * buffer, + size_t line_bits, + size_t line_stride, + size_t line_count, + struct qr_data ** data) +{ + struct qr_bitmap src_bmp; + struct qr_code code; + enum qr_ec_level ec; + int mask; + struct qr_bitstream * data_bits; + + fprintf(stderr, "parsing code bitmap %lux%lu\n", line_bits, line_count); + + if (line_bits != line_count + || line_bits < 21 + || (line_bits - 17) % 4 != 0) { + /* Invalid size */ + fprintf(stderr, "Invalid size\n"); + return -1; + } + + code.version = (line_bits - 17) / 4; + fprintf(stderr, "assuming version %d\n", code.version); + + src_bmp.bits = (unsigned char *) buffer; /* dropping const! */ + src_bmp.mask = NULL; + src_bmp.stride = line_stride; + src_bmp.width = line_bits; + src_bmp.height = line_count; + + if (code.version >= 7 && read_version(&src_bmp) != code.version) { + fprintf(stderr, "Invalid version info\n"); + return -1; + } + + if (read_format(&src_bmp, &ec, &mask) != 0) { + fprintf(stderr, "Failed to read format\n"); + return -1; + } + + fprintf(stderr, "detected ec type %d; mask %d\n", ec, mask); + + code.modules = qr_mask_apply(&src_bmp, mask); + if (code.modules == NULL) { + fprintf(stderr, "failed to apply mask\n"); + return -1; + } + + qr_layout_init_mask(&code); + + data_bits = qr_bitstream_create(); + /* XXX: check return */ + + read_bits(&code, ec, data_bits); + /* XXX: check return */ + + /* + { + fprintf(stderr, "decoding failed\n"); + qr_bitmap_destroy(code.modules); + qr_bitstream_destroy(bits); + *data = NULL; + return -1; + } + */ + + *data = malloc(sizeof(*data)); + /* XXX: check return */ + + (*data)->version = code.version; + (*data)->ec = ec; + (*data)->bits = data_bits; + (*data)->offset = 0; + + return 0; +} + +int qr_decode_format(unsigned bits, enum qr_ec_level * ec, int * mask) +{ + bits ^= 0x5412; + + /* TODO: check and fix errors */ + + bits >>= 10; + *mask = bits & 7; + *ec = bits >> 3; + + return 0; +} + +int qr_decode_version(unsigned long bits, int * version) +{ + int v, errors; + unsigned long version_bits; + int best_err, best_version; + + if (bits != (bits & 0x3FFFF)) + fprintf(stderr, "WARNING: excess version bits"); + + best_err = 18; + + for (v = 7; v <= 40; ++v) { + /* FIXME: cache these values */ + /* see calc_version_bits() */ + version_bits = v; + version_bits <<= 12; + version_bits |= gf_residue(version_bits, 0x1F25); + + /* count errors */ + errors = 0; + version_bits ^= bits; + while (version_bits != 0) { + if ((version_bits & 1) == 1) + ++errors; + version_bits >>= 1; + } + + if (errors < best_err) { + best_version = v; + best_err = errors; + } + + if (errors == 0) /* can we do better than this? */ + break; + } + + *version = best_version; + + return best_err; +} + |