这两天的C语言开发工作中用到了多次字符串格式化拼接，分享一下自己写的一个接口，动态分配内存，减少因缓冲区大小不够导致字符串被截断的烦恼
直接上代码：
#include <stdio.h>#include <stdlib.h>#include <string.h>#include <stdarg.h>int str_append_to_string(char **str, const char *fmt, ...) {int ret = 0;char *ptr = NULL;va_list args;int limit_size = 0;static int init_size = 256;static int use_size = 0;int size = 0;int append_ok = 0;if (fmt == NULL || strlen(fmt) <= 0){printf("[%s:%d] param error\n", __FUNCTION__, __LINE__);return -1;}ptr = *str;if (ptr == NULL){ptr = (char *)malloc(init_size * sizeof(char));if (ptr == NULL){printf("[%s:%d] malloc failed\n", __FUNCTION__, __LINE__);return -1;}init_size = 256;use_size = 0;memset(ptr, 0, (init_size * sizeof(char)));}do{limit_size = init_size - use_size - 1;va_start(args, fmt);size = vsnprintf((ptr + use_size), limit_size, fmt, args);va_end(args);if (size > 0 && size <= limit_size){use_size += size;append_ok = 1;continue;}// need more memoryinit_size += init_size >> 2;char *ptr_backup = ptr; // 备份ptr指针ptr = (char *)realloc(ptr, init_size * sizeof(char)); // realloc失败的话，ptr之前malloc的内存是不会被释放的if (ptr == NULL){printf("[%s:%d] realloc failed\n", __FUNCTION__, __LINE__);ptr = ptr_backup; // 还原ptr指针ret = -1;break;}} while(!append_ok);*str = ptr;return ret;}int main(int argc, char*argv[]){int ret = -1;char *string = NULL;ret = str_append_to_string(&string, "letters/%s/id_card/%d/name/%s", "ABC", 123, "Bob");if (ret == 0){printf("string:%s\n", string);}if (string != NULL){free(string);string = NULL;}return 0;}
运行效果：
