decoder.h

00001 /*------------------------------------------------------------------------
00002  *  Copyright 2007-2009 (c) Jeff Brown <spadix@users.sourceforge.net>
00003  *
00004  *  This file is part of the ZBar Bar Code Reader.
00005  *
00006  *  The ZBar Bar Code Reader is free software; you can redistribute it
00007  *  and/or modify it under the terms of the GNU Lesser Public License as
00008  *  published by the Free Software Foundation; either version 2.1 of
00009  *  the License, or (at your option) any later version.
00010  *
00011  *  The ZBar Bar Code Reader is distributed in the hope that it will be
00012  *  useful, but WITHOUT ANY WARRANTY; without even the implied warranty
00013  *  of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00014  *  GNU Lesser Public License for more details.
00015  *
00016  *  You should have received a copy of the GNU Lesser Public License
00017  *  along with the ZBar Bar Code Reader; if not, write to the Free
00018  *  Software Foundation, Inc., 51 Franklin St, Fifth Floor,
00019  *  Boston, MA  02110-1301  USA
00020  *
00021  *  http://sourceforge.net/projects/zbar
00022  *------------------------------------------------------------------------*/
00023 #ifndef _DECODER_H_
00024 #define _DECODER_H_
00025 
00026 #include <config.h>
00027 #include <stdlib.h>     /* realloc */
00028 
00029 #include <zbar.h>
00030 
00031 #define NUM_CFGS (ZBAR_CFG_MAX_LEN - ZBAR_CFG_MIN_LEN + 1)
00032 
00033 #ifdef ENABLE_EAN
00034 # include "decoder/ean.h"
00035 #endif
00036 #ifdef ENABLE_I25
00037 # include "decoder/i25.h"
00038 #endif
00039 #ifdef ENABLE_CODE39
00040 # include "decoder/code39.h"
00041 #endif
00042 #ifdef ENABLE_CODE128
00043 # include "decoder/code128.h"
00044 #endif
00045 #ifdef ENABLE_PDF417
00046 # include "decoder/pdf417.h"
00047 #endif
00048 #ifdef ENABLE_QRCODE
00049 # include "decoder/qr_finder.h"
00050 #endif
00051 
00052 /* size of bar width history (implementation assumes power of two) */
00053 #ifndef DECODE_WINDOW
00054 # define DECODE_WINDOW  16
00055 #endif
00056 
00057 /* initial data buffer allocation */
00058 #ifndef BUFFER_MIN
00059 # define BUFFER_MIN   0x20
00060 #endif
00061 
00062 /* maximum data buffer allocation
00063  * (longer symbols are rejected)
00064  */
00065 #ifndef BUFFER_MAX
00066 # define BUFFER_MAX  0x100
00067 #endif
00068 
00069 /* buffer allocation increment */
00070 #ifndef BUFFER_INCR
00071 # define BUFFER_INCR  0x10
00072 #endif
00073 
00074 #define CFG(dcode, cfg) ((dcode).configs[(cfg) - ZBAR_CFG_MIN_LEN])
00075 #define TEST_CFG(config, cfg) (((config) >> (cfg)) & 1)
00076 
00077 /* symbology independent decoder state */
00078 struct zbar_decoder_s {
00079     unsigned char idx;                  /* current width index */
00080     unsigned w[DECODE_WINDOW];          /* window of last N bar widths */
00081     zbar_symbol_type_t type;            /* type of last decoded data */
00082     zbar_symbol_type_t lock;            /* buffer lock */
00083 
00084     /* everything above here is automatically reset */
00085     unsigned buf_alloc;                 /* dynamic buffer allocation */
00086     unsigned buflen;                    /* binary data length */
00087     unsigned char *buf;                 /* decoded characters */
00088     void *userdata;                     /* application data */
00089     zbar_decoder_handler_t *handler;    /* application callback */
00090 
00091     /* symbology specific state */
00092 #ifdef ENABLE_EAN
00093     ean_decoder_t ean;                  /* EAN/UPC parallel decode attempts */
00094 #endif
00095 #ifdef ENABLE_I25
00096     i25_decoder_t i25;                  /* Interleaved 2 of 5 decode state */
00097 #endif
00098 #ifdef ENABLE_CODE39
00099     code39_decoder_t code39;            /* Code 39 decode state */
00100 #endif
00101 #ifdef ENABLE_CODE128
00102     code128_decoder_t code128;          /* Code 128 decode state */
00103 #endif
00104 #ifdef ENABLE_PDF417
00105     pdf417_decoder_t pdf417;            /* PDF417 decode state */
00106 #endif
00107 #ifdef ENABLE_QRCODE
00108     qr_finder_t qrf;                    /* QR Code finder state */
00109 #endif
00110 };
00111 
00112 /* return current element color */
00113 static inline char get_color (const zbar_decoder_t *dcode)
00114 {
00115     return(dcode->idx & 1);
00116 }
00117 
00118 /* retrieve i-th previous element width */
00119 static inline unsigned get_width (const zbar_decoder_t *dcode,
00120                                   unsigned char offset)
00121 {
00122     return(dcode->w[(dcode->idx - offset) & (DECODE_WINDOW - 1)]);
00123 }
00124 
00125 /* retrieve bar+space pair width starting at offset i */
00126 static inline unsigned pair_width (const zbar_decoder_t *dcode,
00127                                    unsigned char offset)
00128 {
00129     return(get_width(dcode, offset) + get_width(dcode, offset + 1));
00130 }
00131 
00132 /* calculate total character width "s"
00133  *   - start of character identified by context sensitive offset
00134  *     (<= DECODE_WINDOW - n)
00135  *   - size of character is n elements
00136  */
00137 static inline unsigned calc_s (const zbar_decoder_t *dcode,
00138                                unsigned char offset,
00139                                unsigned char n)
00140 {
00141     /* FIXME check that this gets unrolled for constant n */
00142     unsigned s = 0;
00143     while(n--)
00144         s += get_width(dcode, offset++);
00145     return(s);
00146 }
00147 
00148 /* fixed character width decode assist
00149  * bar+space width are compared as a fraction of the reference dimension "x"
00150  *   - +/- 1/2 x tolerance
00151  *   - measured total character width (s) compared to symbology baseline (n)
00152  *     (n = 7 for EAN/UPC, 11 for Code 128)
00153  *   - bar+space *pair width* "e" is used to factor out bad "exposures"
00154  *     ("blooming" or "swelling" of dark or light areas)
00155  *     => using like-edge measurements avoids these issues
00156  *   - n should be > 3
00157  */
00158 static inline int decode_e (unsigned e,
00159                             unsigned s,
00160                             unsigned n)
00161 {
00162     /* result is encoded number of units - 2
00163      * (for use as zero based index)
00164      * or -1 if invalid
00165      */
00166     unsigned char E = ((e * n * 2 + 1) / s - 3) / 2;
00167     return((E >= n - 3) ? -1 : E);
00168 }
00169 
00170 /* acquire shared state lock */
00171 static inline char get_lock (zbar_decoder_t *dcode,
00172                              zbar_symbol_type_t req)
00173 {
00174     if(dcode->lock)
00175         return(1);
00176     dcode->lock = req;
00177     return(0);
00178 }
00179 
00180 /* ensure output buffer has sufficient allocation for request */
00181 static inline char size_buf (zbar_decoder_t *dcode,
00182                              unsigned len)
00183 {
00184     if(len < dcode->buf_alloc)
00185         /* FIXME size reduction heuristic? */
00186         return(0);
00187     if(len > BUFFER_MAX)
00188         return(1);
00189     if(len < dcode->buf_alloc + BUFFER_INCR) {
00190         len = dcode->buf_alloc + BUFFER_INCR;
00191         if(len > BUFFER_MAX)
00192             len = BUFFER_MAX;
00193     }
00194     unsigned char *buf = realloc(dcode->buf, len);
00195     if(!buf)
00196         return(1);
00197     dcode->buf = buf;
00198     dcode->buf_alloc = len;
00199     return(0);
00200 }
00201 
00202 extern const char *_zbar_decoder_buf_dump (unsigned char *buf,
00203                                             unsigned int buflen);
00204 
00205 #endif
00206