windows平台修改libnfc 1.7.0使其支持pn532_uart模块

前几天写了一篇文章，详述了libnfc 1.7.0在windows下的编译过程，打开了对acr122u模块、pn53x_usb模块、pn532_uart模块等的支持，今天试了一下，发现在win下libnfc默认好像只扫描使用acr122_pcsc driver和pn53x_usb driver的模块，而我连接了pn532_uart模块之后提示没有找到NFC设备。

Debug模式编译运行nfc-list.exe输出如下:
unknown libnfc.general  log_level is set to 3
debug   libnfc.general  allow_autoscan is set to true
debug   libnfc.general  allow_intrusive_scan is set to false
debug   libnfc.general  0 device(s) defined by user
nfc-list.exe uses libnfc 1.7.0
debug   libnfc.general  0 device(s) found using acr122_pcsc driver
debug   libnfc.general  0 device(s) found using pn53x_usb driver
No NFC device found.

于是，我开始查找支持pn532_uart的方法，通过查看源码发现libnfc使用两种方式获取nfc设备：
1.自动扫描 autoscan
2.用户自定义设备 user_defined_device

libnfc支持读取libnfc.conf配置文件的方式加载用户定义的设备。

最开始，我尝试了在cmake生成的config.h里增加#define CONFFILES，重新编译的时候报错：

undefined reference to '_imp__regcomp'
这是由于conf.c里面调用了regcomp等函数，这些函数属于regex正则解析库，但是我使用的MinGW64里面没有这个库。

于是我复制了早期的MinGW的libregex库以及头文件，编译能通过，但是运行nfc-list.exe运行到读取配置文件时就出错退出了，估计还是正则库有问题。

libregex使用不了也没关系，其实可以修改conf.c去掉正则解析的过程，直接将参数赋值给nfc_context。

主要需要修改config.h和conf.c两个文件。

在config.h里增加 #define CONFFILES
修改conf.c如下：

#include "conf.h"#ifdef HAVE_CONFIG_H#  include "config.h"#endif // HAVE_CONFIG_H#ifdef CONFFILES#include <stdio.h>#include <stdlib.h>#include <dirent.h>#include <string.h>#include <regex.h>#include <sys/stat.h>#include <nfc/nfc.h>#include "nfc-internal.h"#include "log.h"#define LOG_CATEGORY "libnfc.config"#define LOG_GROUP    NFC_LOG_GROUP_CONFIG#ifndef LIBNFC_SYSCONFDIR// If this define does not already exists, we build it using SYSCONFDIR#ifndef SYSCONFDIR#error "SYSCONFDIR is not defined but required."#endif // SYSCONFDIR#define LIBNFC_SYSCONFDIR      SYSCONFDIR"/nfc"#endif // LIBNFC_SYSCONFDIR//#define LIBNFC_CONFFILE        LIBNFC_SYSCONFDIR"/libnfc.conf"//#define LIBNFC_DEVICECONFDIR   LIBNFC_SYSCONFDIR"/devices.d"#define LIBNFC_CONFFILE        "libnfc.conf"#define LIBNFC_DEVICECONFDIR   "devices.d"static boolconf_parse_file(const char *filename, void (*conf_keyvalue)(void *data), void *data){  printf("Try to Conf Key Value by chenxupro\n");   conf_keyvalue(data);  return true;}static voidconf_keyvalue_context(void *data){  nfc_context *context = (nfc_context *)data;  //if (strcmp(key, "allow_autoscan") == 0) {    string_as_boolean("true", &(context->allow_autoscan));  //} else if (strcmp(key, "allow_intrusive_scan") == 0) {    string_as_boolean("false", &(context->allow_intrusive_scan));  //} else if (strcmp(key, "log_level") == 0) {    context->log_level = atoi("2");  //} else if (strcmp(key, "device.name") == 0) {    if ((context->user_defined_device_count == 0) || strcmp(context->user_defined_devices[context->user_defined_device_count - 1].name, "") != 0) {      if (context->user_defined_device_count >= MAX_USER_DEFINED_DEVICES) {        log_put(LOG_GROUP, LOG_CATEGORY, NFC_LOG_PRIORITY_ERROR, "%s", "Configuration exceeded maximum user-defined devices.");        return;      }      context->user_defined_device_count++;    }    strcpy(context->user_defined_devices[context->user_defined_device_count - 1].name, "chenxupro PN532");  //} else if (strcmp(key, "device.connstring") == 0) {    if ((context->user_defined_device_count == 0) || strcmp(context->user_defined_devices[context->user_defined_device_count - 1].connstring, "") != 0) {      if (context->user_defined_device_count >= MAX_USER_DEFINED_DEVICES) {        log_put(LOG_GROUP, LOG_CATEGORY, NFC_LOG_PRIORITY_ERROR, "%s", "Configuration exceeded maximum user-defined devices.");        return;      }      context->user_defined_device_count++;    }    strcpy(context->user_defined_devices[context->user_defined_device_count - 1].connstring, "pn532_uart:COM9:115200");}void conf_load(nfc_context *context){  conf_parse_file(LIBNFC_CONFFILE, conf_keyvalue_context, context);}#endif // CONFFILES

重新编译，运行结果如下：
unknown libnfc.general  log_level is set to 2
debug   libnfc.general  allow_autoscan is set to true
debug   libnfc.general  allow_intrusive_scan is set to false
debug   libnfc.general  1 device(s) defined by user
debug   libnfc.general    #0 name: "chenxupro PN532", connstring: "pn532_uart:COM9:115200"
debug   libnfc.general  0 device(s) found using acr122_pcsc driver
debug   libnfc.general  0 device(s) found using pn53x_usb driver
debug   libnfc.driver.pn532_uart        Attempt to open: COM9 at 115200 bauds.


Try to Conf Key Value by chenxupro
nfc-list.exe uses libnfc 1.7.0
NFC device: pn532_uart:COM9 opened
1 ISO14443A passive target(s) found:
ISO/IEC 14443A (106 kbps) target:
    ATQA (SENS_RES): 00  04  
       UID (NFCID1): 7d  88  c9  1d  
      SAK (SEL_RES): 08