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写了一个连接字符串的lib, 请指点一二.

时间：2010-08-02

来源：互联网

本帖最后由 liexusong 于 2010-08-02 11:42 编辑

/*
* FileName: mystring.c
* eg. MyString *mystr = mystr_new(); mystr->add(mystr, "Hello World\n"); mystr->free(mystr);
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define INITSIZE 1024
#define EXTSIZE 512
struct _MyString;
typedef struct _MyString MyString;
struct _MyString {
unsigned long size;
unsigned long used;
char *pstr;
char *current;
MyString *(*add)(MyString *, char *);
int (*free)(MyString *);
char *(*fetch)(MyString *);
};
MyString *mystr_add(MyString *ptr, char *str) {
size_t len, newsize;
char *tmp;
if (!ptr) {
return NULL;
}
len = strlen(str);
if (ptr->size - ptr->used >= len) {
memcpy(ptr->current, str, len);
ptr->current += len;
ptr->used += len;
} else {
newsize = (len / (ptr->size - ptr->used) + 1) * EXTSIZE + ptr->size; /* new malloc memory size */
tmp = (char *) malloc ( newsize + 1 );
if (!tmp) {
return NULL;
}
memcpy(tmp, ptr->pstr, ptr->used);
memcpy(tmp + ptr->used, str, len);
tmp[newsize] = '\0';
free(ptr->pstr);
ptr->size = newsize;
ptr->used += len;
ptr->pstr = tmp;
ptr->current = ptr->pstr + ptr->used;
}
return ptr;
}
int mystr_free(MyString *ptr) {
if (!ptr) {
return -1;
}
free(ptr->pstr);
free(ptr);
return 0;
}
char *mystr_fetch(MyString *ptr) {
if (!ptr) {
return NULL;
}
*(ptr->current) = '\0';
return ptr->pstr;
}
MyString *mystr_new() {
MyString *ptr;
ptr = (MyString *) malloc (sizeof (MyString));
if (!ptr) {
return NULL;
}
ptr->pstr = (char *) malloc (INITSIZE + 1);
if (!ptr->pstr) {
return NULL;
}
ptr->pstr[INITSIZE] = '\0';
ptr->size = INITSIZE;
ptr->used = 0;
ptr->current = ptr->pstr;
ptr->add = mystr_add;
ptr->free = mystr_free;
ptr->fetch = mystr_fetch;
return ptr;
}
int main() {
MyString *mystr;
mystr = mystr_new();
mystr->add(mystr, "The realloc function changes the size of an allocated memory block. The memblock argument points to the beginning of the memory block. If memblock is NULL, realloc behaves the same way as malloc and allocates a new block of size bytes. If memblock is not NULL, it should be a pointer returned by a previous call to calloc, malloc, or realloc.\n");
mystr->add(mystr, " The size argument gives the new size of the block, in bytes. The contents of the block are unchanged up to the shorter of the new and old sizes, although the new block can be in a different location. Because the new block can be in a new memory location, the pointer returned by realloc is not guaranteed to be the pointer passed through the memblock argument. realloc does not zero newly allocated memory in the case of buffer growth.\n");
mystr->add(mystr, "realloccalls mallocin order to use the C++ _set_new_mode function to set the new handler mode. The new handler mode indicates whether, on failure, malloc is to call the new handler routine as set by _set_new_handler. By default, malloc does not call the new handler routine on failure to allocate memory. You can override this default behavior so that, when realloc fails to allocate memory, malloc calls the new handler routine in the same way that the new operator does when it fails for the same reason. To override the default, call\n");
printf("%s", mystr->fetch(mystr));
printf("\nMemory size: %d Bytes, used: %d Bytes\n", mystr->size, mystr->used);
mystr->free(mystr);
return 0;
}

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不知道效率怎么样呢?