sds.c(一）

#include <stdio.h>
#include <string.h>
#include "zmalloc.h"
#include "testhelp.h"

typedef char *sds;

struct sdshdr {
    unsigned int len;
    unsigned int free;
    char buf[];
};

static inline size_t sdslen(const sds s) {
    printf("sizeof(struct sdshdr)=%d
",sizeof(struct sdshdr));
    struct sdshdr *sh = (void*)(s-(sizeof(struct sdshdr)));
    printf("sh->buf=%s
",sh->buf);
    printf("sh->len=%d
",sh->len);
    return sh->len;
}

/* Create a new sds string with the content specified by the 'init' pointer
 * and 'initlen'.
 * If NULL is used for 'init' the string is initialized with zero bytes.
 *
 * The string is always null-termined (all the sds strings are, always) so
 * even if you create an sds string with:
 *
 * mystring = sdsnewlen("abc",3);
 *
 * You can print the string with printf() as there is an implicit  at the
 * end of the string. However the string is binary safe and can contain
 *  characters in the middle, as the length is stored in the sds header. */
sds sdsnewlen(const void *init, size_t initlen) {
    struct sdshdr *sh;
    
    printf("***sdsnewlen init=%s len=%d***
",init,initlen);
    printf("sizeof(struct sdshdr)+initlen+1=%d***
",sizeof(struct sdshdr)+initlen+1);
    if (init) {
        sh = zmalloc(sizeof(struct sdshdr)+initlen+1);
    } else {
        sh = zcalloc(sizeof(struct sdshdr)+initlen+1);
    }
    if (sh == NULL) return NULL;
    sh->len = initlen;
    sh->free = 0;
    if (initlen && init)
        memcpy(sh->buf, init, initlen);
    sh->buf[initlen] = '';
    return (char*)sh->buf;
}

/* Create a new sds string starting from a null termined C string. */
sds sdsnew(const char *init) {
    size_t initlen = (init == NULL) ? 0 : strlen(init);
    return sdsnewlen(init, initlen);
}

int main()
{

    struct sdshdr *sh;
    sds x = sdsnew("foo"), y;

    test_cond("Create a string and obtain the length",
        sdslen(x) == 3 && memcmp(x,"foo",4) == 0);
    
    
}

/*
gcc sds.c zmalloc.c

[root@rac1 Sds]# ./a.out 123
***sdsnewlen init=foo len=3***
sizeof(struct sdshdr)+initlen+1=12***
1 - Create a string and obtain the length: sizeof(struct sdshdr)=8
sh->buf=foo
sh->len=3
PASSED
*/