user-0 提问: c语言 字符串转化为16进制数和16进制数转化为char型如何实现

回复:
user: user-1
content: #include <stdio.h> #include <stdlib.h>  unsigned long long StrToHex(const char *pstr) {     unsigned long long ull = 0ULL;     if (pstr != NULL) {         while (*pstr != 0) {             char ch = *pstr++;             if (ch != ' ') {                 if (ch == '0' && (*pstr == 'x' || *pstr == 'X')) {                     pstr++;                     while (*pstr != 0) {                         unsigned char uc = 0;                         if (*pstr >= '0' && *pstr <= '9') {                             uc = (unsigned char)(*pstr - '0');                         } else if (*pstr >= 'a' && *pstr <= 'f') {                             uc = (unsigned char)(*pstr - 'a' + 10);                         } else if (*pstr >= 'A' && *pstr <= 'F') {                             uc = (unsigned char)(*pstr - 'A' + 10);                         } else {                             break;                         }                         ull <<= 4;                         ull |= uc;                         pstr++;                     }                 }                 break;             }         }     }     return ull; }  int HexToStr(unsigned long long ull, char *pstr, size_t size) {     int ret = -1;     if (pstr != NULL && size > 0) {         char pref[] = { '0', 'x' };         size_t cch = sizeof(pref);         unsigned long long _ull = ull;          while (_ull > 0) {             _ull >>= 4;             cch++;         }          if (size >= cch) {             *pstr++ = pref[0];             *pstr++ = pref[1];              while (cch-- > sizeof(pref)) {                 pstr++;             }              *pstr-- = 0;              while (ull > 0ULL) {                 unsigned char uc = ull & 0xF;                 *pstr-- = uc + ((uc < 10) ? '0' : ('A' - 10));                 ull >>= 4;             }              ret = 0;         }     }     return ret; }  int main(int argc, char *argv[]) {     char str[32] = { 0 };     char *hexstr = "0x00123abcdefgh";     unsigned long long ullret = 0ULL;     unsigned long long ulltest = 0x123456789ABCDEFULL;      // 自己编写函数将字符串作为 16 进制数字字符串解释为整数     ullret = StrToHex(hexstr);     printf("StrToHex:\n%s -> 0x%llX\n", hexstr, ullret);      // 自己编写函数将整数格式化为以 16 进制表示的字符串     if (HexToStr(ulltest, str, 32) != -1) {         printf("HexToStr:\n0x%llX -> %s\n", ulltest, str);     }      putchar('\n');      // 用 strtoull 将字符串作为 16 进制数字字符串解释为整数     ullret = strtoull(hexstr, NULL, 16);     printf("strtoull:\n%s -> 0x%llX\n", hexstr, ullret);      // 用 sprintf/snprintf 将整数格式化为以 16 进制表示的字符串     if (snprintf(str, 32, "0x%llX", ulltest) > 0) {         printf("snprintf:\n0x%llX -> %s\n", ulltest, str);     }      putchar('\n');      return 0; }

user: user-2
content: 其实字符在计算机中存储的都是ASCII码，可以再MSDN搜索ASCII character codes 有2种方法转换，一种是，输入ASCII表，直接在表中搜素字符对应的16进制； 一种是根据字符对应的10进制数转换到16进制

user: user-3
content: 打错了,是GNU不是GUN

user: user-3
content: GUN提供了类似的例子，楼主可以看卡． /* Copyright (C) 1991-2014 Free Software Foundation, Inc.    This file is part of the GNU C Library.     The GNU C Library 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 2.1 of the License, or (at your option) any later version.     The GNU C Library 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    Lesser General Public License for more details.     You should have received a copy of the GNU Lesser General Public    License along with the GNU C Library; if not, see    <http://www.gnu.org/licenses/>.  */  #include <ctype.h> #include <locale.h> #include <stddef.h> #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <string.h> #include <math.h>  struct ltest   {     const char *str;		/* Convert this.  */     double expect;		/* To get this.  */     char left;			/* With this left over.  */     int err;			/* And this in errno.  */   }; static const struct ltest tests[] =   {     { "12.345", 12.345, '\0', 0 },     { "12.345e19", 12.345e19, '\0', 0 },     { "-.1e+9", -.1e+9, '\0', 0 },     { ".125", .125, '\0', 0 },     { "1e20", 1e20, '\0', 0 },     { "0e-19", 0, '\0', 0 },     { "4\00012", 4.0, '\0', 0 },     { "5.9e-76", 5.9e-76, '\0', 0 },     { "0x1.4p+3", 10.0, '\0', 0 },     { "0xAp0", 10.0, '\0', 0 },     { "0x0Ap0", 10.0, '\0', 0 },     { "0x0A", 10.0, '\0', 0 },     { "0xA0", 160.0, '\0', 0 },     { "0x0.A0p8", 160.0, '\0', 0 },     { "0x0.50p9", 160.0, '\0', 0 },     { "0x0.28p10", 160.0, '\0', 0 },     { "0x0.14p11", 160.0, '\0', 0 },     { "0x0.0A0p12", 160.0, '\0', 0 },     { "0x0.050p13", 160.0, '\0', 0 },     { "0x0.028p14", 160.0, '\0', 0 },     { "0x0.014p15", 160.0, '\0', 0 },     { "0x00.00A0p16", 160.0, '\0', 0 },     { "0x00.0050p17", 160.0, '\0', 0 },     { "0x00.0028p18", 160.0, '\0', 0 },     { "0x00.0014p19", 160.0, '\0', 0 },     { "0x1p-1023",       1.11253692925360069154511635866620203210960799023116591527666e-308,       '\0', 0 },     { "0x0.8p-1022",       1.11253692925360069154511635866620203210960799023116591527666e-308,       '\0', 0 },     { "Inf", HUGE_VAL, '\0', 0 },     { "-Inf", -HUGE_VAL, '\0', 0 },     { "+InFiNiTy", HUGE_VAL, '\0', 0 },     { "0x80000Ap-23", 0x80000Ap-23, '\0', 0 },     { "1e-324", 0, '\0', ERANGE },     { "0x100000000000008p0", 0x1p56, '\0', 0 },     { "0x100000000000008.p0", 0x1p56, '\0', 0 },     { "0x100000000000008.00p0", 0x1p56, '\0', 0 },     { "0x10000000000000800p0", 0x1p64, '\0', 0 },     { "0x10000000000000801p0", 0x1.0000000000001p64, '\0', 0 },     { NULL, 0, '\0', 0 }   };  static void expand (char *dst, int c); static int long_dbl (void); static int locale_test (void);  int main (int argc, char ** argv) {   char buf[100];   const struct ltest *lt;   char *ep;   int status = 0;   int save_errno;    for (lt = tests; lt->str != NULL; ++lt)     {       double d;        errno = 0;       d = strtod(lt->str, &ep);       save_errno = errno;       printf ("strtod (\"%s\") test %u", 	     lt->str, (unsigned int) (lt - tests));       if (d == lt->expect && *ep == lt->left && save_errno == lt->err) 	puts ("\tOK");       else 	{ 	  puts ("\tBAD"); 	  if (d != lt->expect) 	    printf ("  returns %.60g, expected %.60g\n", d, lt->expect); 	  if (lt->left != *ep) 	    { 	      char exp1[5], exp2[5]; 	      expand (exp1, *ep); 	      expand (exp2, lt->left); 	      printf ("  leaves '%s', expected '%s'\n", exp1, exp2); 	    } 	  if (save_errno != lt->err) 	    printf ("  errno %d (%s)  instead of %d (%s)\n", 		    save_errno, strerror (save_errno), 		    lt->err, strerror (lt->err)); 	  status = 1; 	}     }    sprintf (buf, "%f", strtod ("-0.0", NULL));   if (strcmp (buf, "-0.000000") != 0)     {       printf ("  strtod (\"-0.0\", NULL) returns \"%s\"\n", buf);       status = 1;     }    const char input[] = "3752432815e-39";    float f1 = strtold (input, NULL);   float f2;   float f3 = strtof (input, NULL);   sscanf (input, "%g", &f2);    if (f1 != f2)     {       printf ("f1 = %a != f2 = %a\n", f1, f2);       status = 1;     }   if (f1 != f3)     {       printf ("f1 = %a != f3 = %a\n", f1, f3);       status = 1;     }   if (f2 != f3)     {       printf ("f2 = %a != f3 = %a\n", f2, f3);       status = 1;     }    const char input2[] = "+1.000000000116415321826934814453125";   if (strtold (input2, NULL) != +1.000000000116415321826934814453125L)     {       printf ("input2: %La != %La\n", strtold (input2, NULL), 	      +1.000000000116415321826934814453125L);       status = 1;     }    static struct { const char *str; long double l; } ltests[] =     {       { "42.0000000000000000001", 42.0000000000000000001L },       { "42.00000000000000000001", 42.00000000000000000001L },       { "42.000000000000000000001", 42.000000000000000000001L }     };   int n;   for (n = 0; n < sizeof (ltests) / sizeof (ltests[0]); ++n)     if (strtold (ltests[n].str, NULL) != ltests[n].l)       { 	printf ("ltests[%d]: %La != %La\n", n, 		strtold (ltests[n].str, NULL), ltests[n].l); 	status = 1;       }    status |= long_dbl ();    status |= locale_test ();    return status ? EXIT_FAILURE : EXIT_SUCCESS; }  static void expand (dst, c)      char *dst;      int c; {   if (isprint (c))     {       dst[0] = c;       dst[1] = '\0';     }   else     (void) sprintf (dst, "%#.3o", (unsigned int) c); }  static int long_dbl (void) {   /* Regenerate this string using       echo '(2^53-1)*2^(1024-53)' | bc | sed 's/\([^\]*\)\\*$/    "\1"/'    */   static const char longestdbl[] =     "17976931348623157081452742373170435679807056752584499659891747680315"     "72607800285387605895586327668781715404589535143824642343213268894641"     "82768467546703537516986049910576551282076245490090389328944075868508"     "45513394230458323690322294816580855933212334827479782620414472316873"     "8177180919299881250404026184124858368";   double d = strtod (longestdbl, NULL);    printf ("strtod (\"%s\", NULL) = %g\n", longestdbl, d);    if (d != 179769313486231570814527423731704356798070567525844996598917476803157260780028538760589558632766878171540458953514382464234321326889464182768467546703537516986049910576551282076245490090389328944075868508455133942304583236903222948165808559332123348274797826204144723168738177180919299881250404026184124858368.000000)     return 1;    return 0; }  /* Perform a few tests in a locale with thousands separators.  */ static int locale_test (void) {   static const struct   {     const char *loc;     const char *str;     double exp;     ptrdiff_t nread;   } tests[] =     {       { "de_DE.UTF-8", "1,5", 1.5, 3 },       { "de_DE.UTF-8", "1.5", 1.0, 1 },       { "de_DE.UTF-8", "1.500", 1500.0, 5 },       { "de_DE.UTF-8", "36.893.488.147.419.103.232", 0x1.0p65, 26 }     }; #define ntests (sizeof (tests) / sizeof (tests[0]))   size_t n;   int result = 0;    puts ("\nLocale tests");    for (n = 0; n < ntests; ++n)     {       double d;       char *endp;        if (setlocale (LC_ALL, tests[n].loc) == NULL) 	{ 	  printf ("cannot set locale %s\n", tests[n].loc); 	  result = 1; 	  continue; 	}        /* We call __strtod_interal here instead of strtod to tests the 	 handling of grouping.  */       d = __strtod_internal (tests[n].str, &endp, 1);       if (d != tests[n].exp) 	{ 	  printf ("strtod(\"%s\") returns %g and not %g\n", 		  tests[n].str, d, tests[n].exp); 	  result = 1; 	}       else if (endp - tests[n].str != tests[n].nread) 	{ 	  printf ("strtod(\"%s\") read %td bytes and not %td\n", 		  tests[n].str, endp - tests[n].str, tests[n].nread); 	  result = 1; 	}     }    if (result == 0)     puts ("all OK");    return result; }

user: user-3
content: 仅供参考． /*************************************************************************     > File Name: sprintf_3.c     > Author: 傻李     > Mail: hellojukay@gmail.com      > Created Time: 2014年11月23日 星期日 16时39分18秒  ************************************************************************/ #include<string.h> #include<stdio.h> int main() { 	char buffer[10]; 	char buffer_0x[20]; 	long int test; 	//输入字符创，转化为16进制打印 	printf("输入一个字符串:") 	fgets(buffer,10,stdin); 	test = atol(buffer); 	printf("%x(16)\n",test); 	//输入整数，转化为字符串打印,首先转化为对应十进制 	printf("输入一个16进制数:") 	scanf("%x",&test); 	sprintf(buffer_0x,"%d",test); 	puts(buffer_0x); 	return 0; }