自己给libnfc库添加一个头文件 很波折

//log.h

/*-
 * Free/Libre Near Field Communication (NFC) library
 *
 * Libnfc historical contributors:
 * Copyright (C) 2009      Roel Verdult
 * Copyright (C) 2009-2013 Romuald Conty
 * Copyright (C) 2010-2012 Romain Tartière
 * Copyright (C) 2010-2013 Philippe Teuwen
 * Copyright (C) 2012-2013 Ludovic Rousseau
 * Additional contributors of this file:
 *
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or (at your
 * option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>
 */



#ifndef __LOG_H__
#define __LOG_H__

#ifdef HAVE_CONFIG_H
#  include "config.h"


#endif // HAVE_CONFIG_H

#include "nfc-internal.h"
//#include "MycharToInt.h" // by wangyong 2013-6-8
//上面就是我准备添加的头文件，头文件里定义了一个函数int MycharToInt(char *pch) ;
//MycharToInt.c实现了这个函数

#define NFC_LOG_PRIORITY_NONE   0
#define NFC_LOG_PRIORITY_ERROR  1
#define NFC_LOG_PRIORITY_INFO   2
#define NFC_LOG_PRIORITY_DEBUG  3

#define NFC_LOG_GROUP_GENERAL   1
#define NFC_LOG_GROUP_CONFIG    2
#define NFC_LOG_GROUP_CHIP      3
#define NFC_LOG_GROUP_DRIVER    4
#define NFC_LOG_GROUP_COM       5
#define NFC_LOG_GROUP_LIBUSB    6

/*
  To enable log only for one (or more) group, you can use this formula:
    log_level = NFC_LOG_PRIORITY(main) + NFC_LOG_PRIORITY(group) * 2 ^ (NFC_LOG_GROUP(group) * 2)

  Examples:
   * Main log level is NONE and only communication group log is set to DEBUG verbosity (for rx/tx trace):
       LIBNFC_LOG_LEVEL=3072  // 0+3072
   * Main log level is ERROR and driver layer log is set to DEBUG level:
       LIBNFC_LOG_LEVEL=769   // 1+768
   * Main log level is ERROR, driver layer is set to INFO and communication is set to DEBUG:
       LIBNFC_LOG_LEVEL=3585  // 1+512+3072
*/

//int log_priority_to_int(const char* priority);
const char *log_priority_to_str(const int priority);

char *getDataFrom_acBuf;

#if defined LOG

#  ifndef __has_attribute
#    define __has_attribute(x) 0
#  endif

#  if __has_attribute(format) || defined(__GNUC__)
#    define __has_attribute_format 1
#  endif

void log_init(const nfc_context *context);
void log_exit(void);
void log_put(const uint8_t group, const char *category, const uint8_t priority, const char *format, ...)
#  if __has_attribute_format
__attribute__((format(printf, 4, 5)))
#  endif
;
#else
// No logging
#define log_init(nfc_context) ((void) 0)
#define log_exit() ((void) 0)
#define log_put(group, category, priority, format, ...) do {} while (0)

#endif // LOG

/**
 * @macro LOG_HEX
 * @brief Log a byte-array in hexadecimal format
 * Max values:  pcTag of 121 bytes + ": " + 300 bytes of data+ "\0" => acBuf of 1024 bytes
 */
#  ifdef LOG
#    define LOG_HEX(group, pcTag, pbtData, szBytes) do { \
    size_t     __szPos; \
    char     __acBuf[4096]; \
    size_t     __szBuf = 0; \
    if ((int)szBytes < 0) { \
      fprintf (stderr, "%s:%d: Attempt to print %d bytes!\n", __FILE__, __LINE__, (int)szBytes); \
      log_put (group, LOG_CATEGORY, NFC_LOG_PRIORITY_ERROR, "%s:%d: Attempt to print %d bytes!\n", __FILE__, __LINE__, (int)szBytes); \
      abort(); \
      break; \
    } \
    snprintf (__acBuf + __szBuf, sizeof(__acBuf) - __szBuf, "%s: ", pcTag); \
    __szBuf += strlen (pcTag) + 2; \
    for (__szPos=0; (__szPos < (size_t)(szBytes)) && (__szBuf < sizeof(__acBuf)); __szPos++) { \
      snprintf (__acBuf + __szBuf, sizeof(__acBuf) - __szBuf, "%02x ",((uint8_t *)(pbtData))[__szPos]); \
      __szBuf += 3; \
    } \
    log_put (group, LOG_CATEGORY, NFC_LOG_PRIORITY_DEBUG, "acBuf: %s endofacBuf", __acBuf); \     
    getDataFrom_acBuf = __acBuf; \ 
    if (getDataFrom_acBuf[0] == 'R' && getDataFrom_acBuf[1] == 'X' && getDataFrom_acBuf[2] == 'X' && getDataFrom_acBuf[3] == ':'  \
        && getDataFrom_acBuf[4] == ' ' && getDataFrom_acBuf[5] == 0x30 && getDataFrom_acBuf[6] == 0x30 && getDataFrom_acBuf[7] == ' ' \
        && getDataFrom_acBuf[8] == 0x34 && getDataFrom_acBuf[9] == 0x33 && getDataFrom_acBuf[10] == ' ' && getDataFrom_acBuf[11]==0x32 \
        && getDataFrom_acBuf[12]==0x30 && getDataFrom_acBuf[13]==' ' && getDataFrom_acBuf[14]==0x30 && getDataFrom_acBuf[15]==0x30) { \        
        printf("log.h __acBuf:%s\n",__acBuf); \        
        int len = strlen(__acBuf); \
        int i; \
        for (i=68;i<len;) \
        { \
            char tmp[3]; \
            strncpy(tmp,__acBuf+i,2); \
            tmp[2]='\0'; \
            int res = MycharToInt(tmp); \ //这里对 MycharToInt 调用

printf("%c",res); \ i += 3; \ } \ }\ } while (0); # else # define LOG_HEX(group, pcTag, pbtData, szBytes) do { \ (void) group; \ (void) pcTag; \ (void) pbtData; \ (void) szBytes; \ } while (0); # endif #endif // __LOG_H__

头文件MycharToInt.h:

#ifndef __MYCHARTOINT_H__
#define __MYCHARTOINT_H__
#endif

int MycharToInt(char *pch) ;

MycharToInt.c:

#include "MycharToInt.h"

//十六进制字符数组转为int型
int MycharToInt(char *pch) {
    int result=0;
    char ch1 = pch[0];
    char ch2 = pch[1];
    int shiwei,gewei;
    switch(ch1) {
        case '0': shiwei=0; break;
        case '1': shiwei=1; break;
        case '2': shiwei=2; break;
        case '3': shiwei=3; break;
        case '4': shiwei=4; break;
        case '5': shiwei=5; break;
        case '6': shiwei=6; break;
        case '7': shiwei=7; break;
        case '8': shiwei=8; break;
        case '9': shiwei=9; break;
        case 'a': shiwei=10; break;
        case 'b': shiwei=11; break;
        case 'c': shiwei=12; break;
        case 'd': shiwei=13; break;
        case 'e': shiwei=14; break;
        case 'f': shiwei=15; break;
    }
    
    switch(ch2) {
        case '0': gewei=0; break;
        case '1': gewei=1; break;
        case '2': gewei=2; break;
        case '3': gewei=3; break;
        case '4': gewei=4; break;
        case '5': gewei=5; break;
        case '6': gewei=6; break;
        case '7': gewei=7; break;
        case '8': gewei=8; break;
        case '9': gewei=9; break;
        case 'a': gewei=10; break;
        case 'b': gewei=11; break;
        case 'c': gewei=12; break;
        case 'd': gewei=13; break;
        case 'e': gewei=14; break;
        case 'f': gewei=15; break;
    }
    
    result = shiwei*16+gewei;
    return result;
}

添加好了，然后在libnfc目录下：

sudo ./configure --with-drivers=pn532_uart --enable-debug

sudo make clean all

sudo make install

总算没有报错，之前一直报错说“multiple definition of MychatToInt”,因为之前我没有MychatToInt.c这个文件，函数定义和实现都在MychatToInt.h里。

虽然这里没报错，但是运行这个库上的函数就报错了，在libllcp的examples下：

sudo ./npp-server

就会报“ no symbol of MychatToInt”。

最后解决方法是，在log.h包含的头文件nfc-internal.h里添加我们自己定义的函数：

int MycharToInt(char *pch) ;

然后在nfc-internal.c里面加上我们的 MycharToInt(char *pch)具体实现。

这样之后在log.h里就能使用 MycharToInt 这个方法了。