redis 源碼閱讀 數值轉字元 longlong2str

標籤：

redis 在底層中會把long long轉成string 再做儲存。 主個功能是在sds模組裡。下面兩函數是把long long 轉成 char  和   unsiged long long 轉成 char。大致的思路是：1 把數值從尾到頭一個一個轉成字元，2 算出長度，加上結束符。3 把字串反轉一下。4 如果是 long long 型 要考慮有負數的情況。 

int sdsll2str(char *s, long long value) {    char *p, aux;    unsigned long long v;    size_t l;    /* Generate the string representation, this method produces     * an reversed string. */    v = (value < 0) ? -value : value;    p = s;    do {        *p++ = ‘0‘+(v%10);        v /= 10;    } while(v);    if (value < 0) *p++ = ‘-‘;    /* Compute length and add null term. */    l = p-s;    *p = ‘\0‘;    /* Reverse the string. */    p--;    while(s < p) {        aux = *s;        *s = *p;        *p = aux;        s++;        p--;    }    return l;}/* Identical sdsll2str(), but for unsigned long long type. */int sdsull2str(char *s, unsigned long long v) {    char *p, aux;    size_t l;    /* Generate the string representation, this method produces     * an reversed string. */    p = s;    do {        *p++ = ‘0‘+(v%10);        v /= 10;    } while(v);    /* Compute length and add null term. */    l = p-s;    *p = ‘\0‘;    /* Reverse the string. */    p--;    while(s < p) {        aux = *s;        *s = *p;        *p = aux;        s++;        p--;    }    return l;}

 

redis 源碼閱讀 數值轉字元 longlong2str