Redis—数据结构之sds

Redis是一个Key Value数据库。Redis有5种数据类型:字符串、列表、哈希、集合、有序集合。而字符串的底层实现方法之一就是使用sds。以下描述中请读者注意区分sds是指简单动态字符串这一数据结构(用大写表示)还是sdshdr头部中buf数组的起始地址(用小写表示)。

SDS源码

如下源码所示。

根据要保存的字符串长度选用不同的头部大小,从而 节省内存
,注意sdshdr5与其他不同,下面会有介绍。

SDS由两部分组成:sds、sdshdr。sds是一个char类型的指针,指向buf数组首元素,buf数组是存储字符串的实际位置;sdshdr是SDS的头部,为SDS加上一个头部的好处就是为了提高某些地方的效率,比如获取buf数组中字符串长度,用O(1)的复杂度从头部就能取得。buf数组是一个空数组,从而使得sdshdr是一个可变长度的结构体,用一个空数组的好处就是分配内存时, 只用分配一次
,而且头部所占用的内存和sds的 内存是连续的
,释放时也 只用释放一次

sdshdr结构体中各字段的介绍:len : 已存储的字符串长度;alloc : 能存储的字符串的最大容量,不包括SDS头部和结尾的NULL字符;flags : 标志位,低3位代表了sds头部类型,高5位未用;buf[] : 字符数组,存储字符串;注意sdshdr5没有len和alloc字段,其flags的低3位同样代表头部类型,但高5位代表保存的字符串长度。 __attribute__ ((__packed__)) : 使得编译器不会因为内存对齐而在结构体中填充字节,以保证内存的紧凑,这样sds – 1就可以得到flags字段,进而能够得到其头部类型。如果填充了字节,则就不能得到flags字段。

buf数组尾部隐含有一个”,SDS是以len字段来判断是否到达字符串末尾,而不是以”判断结尾。所以sds存储的字符串中间可以出现”,即sds字符串是 二进制安全的

typedef char *sds;

struct __attribute__ ((__packed__)) sdshdr5 {
    unsigned char flags; /* 3 lsb of type, and 5 msb of string length */
    char buf[];
};
struct __attribute__ ((__packed__)) sdshdr8 {
    uint8_t len; /* used */
    uint8_t alloc; /* excluding the header and null terminator */
    unsigned char flags; /* 3 lsb of type, 5 unused bits */
    char buf[];
};
struct __attribute__ ((__packed__)) sdshdr16 {
    uint16_t len; /* used */
    uint16_t alloc; /* excluding the header and null terminator */
    unsigned char flags; /* 3 lsb of type, 5 unused bits */
    char buf[];
};
struct __attribute__ ((__packed__)) sdshdr32 {
    uint32_t len; /* used */
    uint32_t alloc; /* excluding the header and null terminator */
    unsigned char flags; /* 3 lsb of type, 5 unused bits */
    char buf[];
};
struct __attribute__ ((__packed__)) sdshdr64 {
    uint64_t len; /* used */
    uint64_t alloc; /* excluding the header and null terminator */
    unsigned char flags; /* 3 lsb of type, 5 unused bits */
    char buf[];
};

既然有这么多类型的头部,一定会有类似宏定义之类能够标识头部,的确有,如下所示:

// flags的低三位代表不同类型的sds头部:
#define SDS_TYPE_5  0
#define SDS_TYPE_8  1
#define SDS_TYPE_16 2
#define SDS_TYPE_32 3
#define SDS_TYPE_64 4
#define SDS_TYPE_MASK 7
#define SDS_TYPE_BITS 3

SDS操作

因为sds和头部是内存连续的,所以当我们得到了一个sds,只要将它-1就可得到flags字段,减头部大小即可得到头部起始地址。SDS的很多操作就是利用了这一点,从而带来了极大的方便和快速。下面我们介绍几个SDS比较重要的几个操作

1. 获取头部起始地址

将sds减去头部大小即可。非常方便快速。

// 返回一个指向sds头部的起始地址的指针
#define SDS_HDR_VAR(T,s) struct sdshdr##T *sh = (void*)((s)-(sizeof(struct sdshdr##T)));
// 返回sds头部的起始地址
#define SDS_HDR(T,s) ((struct sdshdr##T *)((s)-(sizeof(struct sdshdr##T))))

2. 获取buf数组中sds存储的字符串长度

先后移1位,得到flags字段,再和掩码相与即可得到头部类型。

static inline size_t sdslen(const sds s) {
    unsigned char flags = s[-1]; // 内存空间连续,所以往后移1个字节,便是flags字段
    switch(flags&SDS_TYPE_MASK) { // 和flags低3位相与,得到sds头部类型
        case SDS_TYPE_5:
            return SDS_TYPE_5_LEN(flags);
        case SDS_TYPE_8:
            return SDS_HDR(8,s)->len; // 先移动到sds头部的起始地址,进而可以直接获取len字段的值。下同
        case SDS_TYPE_16:
            return SDS_HDR(16,s)->len;
        case SDS_TYPE_32:
            return SDS_HDR(32,s)->len;
        case SDS_TYPE_64:
            return SDS_HDR(64,s)->len;
    }
    return 0;
}

3. 获取buf数组中剩余可用的内存大小

static inline size_t sdsavail(const sds s) {
    unsigned char flags = s[-1]; // 后移1字节,得到flags字段
    switch(flags&SDS_TYPE_MASK) { // 得到sds头部类型
        case SDS_TYPE_5: {
            return 0;
        }
        case SDS_TYPE_8: {
            SDS_HDR_VAR(8,s);
            return sh->alloc - sh->len; // 总大小减去已使用大小
        }
        case SDS_TYPE_16: {
            SDS_HDR_VAR(16,s);
            return sh->alloc - sh->len;
        }
        case SDS_TYPE_32: {
            SDS_HDR_VAR(32,s);
            return sh->alloc - sh->len;
        }
        case SDS_TYPE_64: {
            SDS_HDR_VAR(64,s);
            return sh->alloc - sh->len;
        }
    }
    return 0;
}

4. 使用字符串初始化一个SDS

注意分配时,程序会自动为buf数组最后一个元素后面添加上”,”对外部完全是透明的,分配内存时自动多分配1个字节保存”,buf数组最后自动添加”。

// sds尾部隐含有一个'';sds是以len字段来判断是否到达字符串末尾
// 所以sds存储的字符串中间可以出现'',即sds字符串是二进制安全的

// 分配一个新sds,buf数组存储内容init
sds sdsnewlen(const void *init, size_t initlen) {
    void *sh;
    sds s;
    char type = sdsReqType(initlen); // 根据长度大小选择合适的sds头部
    /* Empty strings are usually created in order to append. Use type 8
     * since type 5 is not good at this. */
    if (type == SDS_TYPE_5 && initlen == 0) type = SDS_TYPE_8;
    int hdrlen = sdsHdrSize(type); // 获取sds头部大小
    unsigned char *fp; /* flags pointer. */

    // 为sds分配内存,总大小为:头部大小+存储字符串的长度+末尾隐含的空字符大小
    sh = s_malloc(hdrlen+initlen+1); 
    if (!init)
        memset(sh, 0, hdrlen+initlen+1); // 内存初始化为0
    if (sh == NULL) return NULL;
    s = (char*)sh+hdrlen; // buf数组的起始地址
    fp = ((unsigned char*)s)-1; // 指向flags字段
    // 初始化sds头部的len,alloc,flags字段
    switch(type) {
        case SDS_TYPE_5: {
            *fp = type | (initlen <len = initlen;
            sh->alloc = initlen;
            *fp = type;
            break;
        }
        case SDS_TYPE_16: {
            SDS_HDR_VAR(16,s);
            sh->len = initlen;
            sh->alloc = initlen;
            *fp = type;
            break;
        }
        case SDS_TYPE_32: {
            SDS_HDR_VAR(32,s);
            sh->len = initlen;
            sh->alloc = initlen;
            *fp = type;
            break;
        }
        case SDS_TYPE_64: {
            SDS_HDR_VAR(64,s);
            sh->len = initlen;
            sh->alloc = initlen;
            *fp = type;
            break;
        }
    }
    // 初始化buf数组
    if (initlen && init)
        memcpy(s, init, initlen); // 拷贝init到buf数组
    s[initlen] = ''; // 添加末尾的空字符
    return s;
}

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5. 空间预分配

当需要将SDS的len增加addlen个字节时,如果SDS剩余空间足够,则什么都不用做。如果剩余空间不够,则会分配新的内存空间,并且采用 预分配
。新长度newlen为原len+addlen,若newlen小于1M,则为SDS分配新的内存大小为2*newlen;若newlen大于等于1M,则SDS分配新的内存大小为newlen + 1M。

 // 为sds的len字段增加addlen个字节,剩余空间不足时会引起空间重新分配
sds sdsMakeRoomFor(sds s, size_t addlen) {
    void *sh, *newsh;
    size_t avail = sdsavail(s);
    size_t len, newlen;
    char type, oldtype = s[-1] & SDS_TYPE_MASK;
    int hdrlen;

    /* Return ASAP if there is enough space left. */
    if (avail >= addlen) return s; // sds剩余空间足够

    len = sdslen(s);
    sh = (char*)s-sdsHdrSize(oldtype);
    newlen = (len+addlen); // sds剩余空间不够,新的len为len+addlen
    
    // 下面两步实现空间预分配
    if (newlen < SDS_MAX_PREALLOC) // 新长度小于1M,则len设为2*(len+addlen)大小
        newlen *= 2;
    else
        newlen += SDS_MAX_PREALLOC; // 新长度大于1M,则len设为 len+1M 大小

    type = sdsReqType(newlen); // 新len对应的sds头部

    /* Don't use type 5: the user is appending to the string and type 5 is
     * not able to remember empty space, so sdsMakeRoomFor() must be called
     * at every appending operation. */
    if (type == SDS_TYPE_5) type = SDS_TYPE_8;

    hdrlen = sdsHdrSize(type);
    if (oldtype==type) {
        newsh = s_realloc(sh, hdrlen+newlen+1);
        if (newsh == NULL) return NULL;
        s = (char*)newsh+hdrlen;
    } else {
        /* Since the header size changes, need to move the string forward,
         * and can't use realloc */
        newsh = s_malloc(hdrlen+newlen+1);
        if (newsh == NULL) return NULL;
        memcpy((char*)newsh+hdrlen, s, len+1);
        s_free(sh);
        s = (char*)newsh+hdrlen;
        s[-1] = type;
        sdssetlen(s, len);
    }
    sdssetalloc(s, newlen);
    return s;
}

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6. 惰性空间释放

当要清空一个SDS时,并不真正释放其内存,而是设置len字段为0即可,这样当之后再次使用到该SDS时,可避免重新分配内存,从而提高效率。

 // 清空sds内容,len字段清为0
 // 但之前的空间并未释放,可避免以后的重新分配内存。实现惰性空间释放
void sdsclear(sds s) {
    sdssetlen(s, 0);
    s[0] = '';
}

只要理解了sds和sdshdr,其操作函数便很容易理解。剩下的就不一一介绍了,我在阅读过程中也做了部分注释,下面附上源码及注释。SDS共两个文件:sds.h和sds.c

sds.h :

/* SDSLib 2.0 -- A C dynamic strings library
 * 简单动态字符串
 */

#ifndef __SDS_H
#define __SDS_H

#define SDS_MAX_PREALLOC (1024*1024) // 1M,空间预分配使用

#include 
#include 
#include 

// 指向存储数据的起始地址
typedef char *sds;

/* Note: sdshdr5 is never used, we just access the flags byte directly.
 * However is here to document the layout of type 5 SDS strings. */

// sds由两部分组成:sds头部(即下面的各种结构体)、真正存储字符串的字符数组
// 这两部分在内存上连续 
// len : 已存储的字符串长度
// alloc : 能存储的字符串的最大容量,不包括sds头部和结尾的NULL字符
// flags : 标志位,最低三位代表了sds头部类型
// buf[] : 字符数组,存储字符串
// __attribute__ ((__packed__)) : 
// 使得编译器不会因为内存对齐而在结构体中填充字节,以保证内存的紧凑,使得下面的s[-1]得到正确的地址
// char buf[] : 初始时不占用内存,而且使得头部内存和存储字符串的内存地址连续。
// sdshdr5比较特殊,flags字段低3位代表sds头部类型,高5位代表已存储的字符串长度
// 分为不同类型的头部,目的是为了存储不同长度的字符串使用不同类型,从而节省内存

 struct __attribute__ ((__packed__)) sdshdr5 {
    unsigned char flags; /* 3 lsb of type, and 5 msb of string length */
    char buf[];
};
struct __attribute__ ((__packed__)) sdshdr8 {
    uint8_t len; /* used */
    uint8_t alloc; /* excluding the header and null terminator */
    unsigned char flags; /* 3 lsb of type, 5 unused bits */
    char buf[];
};
struct __attribute__ ((__packed__)) sdshdr16 {
    uint16_t len; /* used */
    uint16_t alloc; /* excluding the header and null terminator */
    unsigned char flags; /* 3 lsb of type, 5 unused bits */
    char buf[];
};
struct __attribute__ ((__packed__)) sdshdr32 {
    uint32_t len; /* used */
    uint32_t alloc; /* excluding the header and null terminator */
    unsigned char flags; /* 3 lsb of type, 5 unused bits */
    char buf[];
};
struct __attribute__ ((__packed__)) sdshdr64 {
    uint64_t len; /* used */
    uint64_t alloc; /* excluding the header and null terminator */
    unsigned char flags; /* 3 lsb of type, 5 unused bits */
    char buf[];
};

// flags的低三位代表不同类型的sds头部:
#define SDS_TYPE_5  0
#define SDS_TYPE_8  1
#define SDS_TYPE_16 2
#define SDS_TYPE_32 3
#define SDS_TYPE_64 4
#define SDS_TYPE_MASK 7
#define SDS_TYPE_BITS 3

// 返回一个指向sds头部的起始地址的指针
#define SDS_HDR_VAR(T,s) struct sdshdr##T *sh = (void*)((s)-(sizeof(struct sdshdr##T)));
// 返回sds头部的起始地址
#define SDS_HDR(T,s) ((struct sdshdr##T *)((s)-(sizeof(struct sdshdr##T))))
// 获取sdshdr5类型的sds存储的字符串长度
#define SDS_TYPE_5_LEN(f) ((f)>>SDS_TYPE_BITS)

// 获取buf数组中sds存储的字符串长度
static inline size_t sdslen(const sds s) {
    unsigned char flags = s[-1]; // 内存空间连续,所以往后移1个字节,便是flags字段
    switch(flags&SDS_TYPE_MASK) { // 和flags低3位相与,得到sds头部类型
        case SDS_TYPE_5:
            return SDS_TYPE_5_LEN(flags);
        case SDS_TYPE_8:
            return SDS_HDR(8,s)->len; // 先移动到sds头部的起始地址,进而可以直接获取len字段的值。下同
        case SDS_TYPE_16:
            return SDS_HDR(16,s)->len;
        case SDS_TYPE_32:
            return SDS_HDR(32,s)->len;
        case SDS_TYPE_64:
            return SDS_HDR(64,s)->len;
    }
    return 0;
}

// 获取buf数组中剩余可用的内存大小
static inline size_t sdsavail(const sds s) {
    unsigned char flags = s[-1]; // 后移1字节,得到flags字段
    switch(flags&SDS_TYPE_MASK) { // 得到sds头部类型
        case SDS_TYPE_5: {
            return 0;
        }
        case SDS_TYPE_8: {
            SDS_HDR_VAR(8,s);
            return sh->alloc - sh->len; // 总大小减去已使用大小
        }
        case SDS_TYPE_16: {
            SDS_HDR_VAR(16,s);
            return sh->alloc - sh->len;
        }
        case SDS_TYPE_32: {
            SDS_HDR_VAR(32,s);
            return sh->alloc - sh->len;
        }
        case SDS_TYPE_64: {
            SDS_HDR_VAR(64,s);
            return sh->alloc - sh->len;
        }
    }
    return 0;
}

// 设置sds头部的len字段
static inline void sdssetlen(sds s, size_t newlen) {
    unsigned char flags = s[-1];
    switch(flags&SDS_TYPE_MASK) {
        case SDS_TYPE_5:
            {
                // 对于sdshdr5,则是设置flags的高5位
                unsigned char *fp = ((unsigned char*)s)-1;
                *fp = SDS_TYPE_5 | (newlen <len = newlen;
            break;
        case SDS_TYPE_16:
            SDS_HDR(16,s)->len = newlen;
            break;
        case SDS_TYPE_32:
            SDS_HDR(32,s)->len = newlen;
            break;
        case SDS_TYPE_64:
            SDS_HDR(64,s)->len = newlen;
            break;
    }
}

// 将sds头部的len字段增加inc
static inline void sdsinclen(sds s, size_t inc) {
    unsigned char flags = s[-1];
    switch(flags&SDS_TYPE_MASK) {
        case SDS_TYPE_5:
            {
                // 对于sdshdr5,则是设置flags的高5位
                unsigned char *fp = ((unsigned char*)s)-1;
                unsigned char newlen = SDS_TYPE_5_LEN(flags)+inc;
                *fp = SDS_TYPE_5 | (newlen <len += inc;
            break;
        case SDS_TYPE_16:
            SDS_HDR(16,s)->len += inc;
            break;
        case SDS_TYPE_32:
            SDS_HDR(32,s)->len += inc;
            break;
        case SDS_TYPE_64:
            SDS_HDR(64,s)->len += inc;
            break;
    }
}

/* sdsalloc() = sdsavail() + sdslen() */
// 获取sds的buf数组总的大小
static inline size_t sdsalloc(const sds s) {
    unsigned char flags = s[-1];
    switch(flags&SDS_TYPE_MASK) {
        case SDS_TYPE_5:
            return SDS_TYPE_5_LEN(flags);
        case SDS_TYPE_8:
            return SDS_HDR(8,s)->alloc;
        case SDS_TYPE_16:
            return SDS_HDR(16,s)->alloc;
        case SDS_TYPE_32:
            return SDS_HDR(32,s)->alloc;
        case SDS_TYPE_64:
            return SDS_HDR(64,s)->alloc;
    }
    return 0;
}

// 设置sds的buf数组总的大小
static inline void sdssetalloc(sds s, size_t newlen) {
    unsigned char flags = s[-1];
    switch(flags&SDS_TYPE_MASK) {
        case SDS_TYPE_5:
            /* Nothing to do, this type has no total allocation info. */
            break;
        case SDS_TYPE_8:
            SDS_HDR(8,s)->alloc = newlen;
            break;
        case SDS_TYPE_16:
            SDS_HDR(16,s)->alloc = newlen;
            break;
        case SDS_TYPE_32:
            SDS_HDR(32,s)->alloc = newlen;
            break;
        case SDS_TYPE_64:
            SDS_HDR(64,s)->alloc = newlen;
            break;
    }
}

sds sdsnewlen(const void *init, size_t initlen);
sds sdsnew(const char *init);
sds sdsempty(void);
sds sdsdup(const sds s);
void sdsfree(sds s);
sds sdsgrowzero(sds s, size_t len);
sds sdscatlen(sds s, const void *t, size_t len);
sds sdscat(sds s, const char *t);
sds sdscatsds(sds s, const sds t);
sds sdscpylen(sds s, const char *t, size_t len);
sds sdscpy(sds s, const char *t);

sds sdscatvprintf(sds s, const char *fmt, va_list ap);
#ifdef __GNUC__
sds sdscatprintf(sds s, const char *fmt, ...)
    __attribute__((format(printf, 2, 3)));
#else
sds sdscatprintf(sds s, const char *fmt, ...);
#endif

sds sdscatfmt(sds s, char const *fmt, ...);
sds sdstrim(sds s, const char *cset);
void sdsrange(sds s, int start, int end);
void sdsupdatelen(sds s);
void sdsclear(sds s);
int sdscmp(const sds s1, const sds s2);
sds *sdssplitlen(const char *s, int len, const char *sep, int seplen, int *count);
void sdsfreesplitres(sds *tokens, int count);
void sdstolower(sds s);
void sdstoupper(sds s);
sds sdsfromlonglong(long long value);
sds sdscatrepr(sds s, const char *p, size_t len);
sds *sdssplitargs(const char *line, int *argc);
sds sdsmapchars(sds s, const char *from, const char *to, size_t setlen);
sds sdsjoin(char **argv, int argc, char *sep);
sds sdsjoinsds(sds *argv, int argc, const char *sep, size_t seplen);

/* Low level functions exposed to the user API */
sds sdsMakeRoomFor(sds s, size_t addlen);
void sdsIncrLen(sds s, int incr);
sds sdsRemoveFreeSpace(sds s);
size_t sdsAllocSize(sds s);
void *sdsAllocPtr(sds s);

/* Export the allocator used by SDS to the program using SDS.
 * Sometimes the program SDS is linked to, may use a different set of
 * allocators, but may want to allocate or free things that SDS will
 * respectively free or allocate. */
void *sds_malloc(size_t size);
void *sds_realloc(void *ptr, size_t size);
void sds_free(void *ptr);

#ifdef REDIS_TEST
int sdsTest(int argc, char *argv[]);
#endif

#endif

View Code

sds.c :

/* SDSLib 2.0 -- A C dynamic strings library
 */

#include 
#include 
#include 
#include 
#include 
#include "sds.h"
#include "sdsalloc.h"

// 获取type类型的sds对应的头部类型大小
static inline int sdsHdrSize(char type) {
    switch(type&SDS_TYPE_MASK) {
        case SDS_TYPE_5:
            return sizeof(struct sdshdr5);
        case SDS_TYPE_8:
            return sizeof(struct sdshdr8);
        case SDS_TYPE_16:
            return sizeof(struct sdshdr16);
        case SDS_TYPE_32:
            return sizeof(struct sdshdr32);
        case SDS_TYPE_64:
            return sizeof(struct sdshdr64);
    }
    return 0;
}

// 根据不同大小选用不同类型的sds头部
static inline char sdsReqType(size_t string_size) {
    if (string_size < 1<<5) // 0~2^5-1
        return SDS_TYPE_5;
    if (string_size < 1<<8) // 2^5~2^8-1
        return SDS_TYPE_8;
    if (string_size < 1<<16) // 2^8~2^16-1
        return SDS_TYPE_16;
    if (string_size < 1<<32) // 2^16~2^32-1
        return SDS_TYPE_32;
    return SDS_TYPE_64; // 2^32~
}

/* 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尾部隐含有一个'';sds是以len字段来判断是否到达字符串末尾
// 所以sds存储的字符串中间可以出现'',即sds字符串是二进制安全的

// 分配一个新sds,buf数组存储内容init
sds sdsnewlen(const void *init, size_t initlen) {
    void *sh;
    sds s;
    char type = sdsReqType(initlen); // 根据长度大小选择合适的sds头部
    /* Empty strings are usually created in order to append. Use type 8
     * since type 5 is not good at this. */
    if (type == SDS_TYPE_5 && initlen == 0) type = SDS_TYPE_8;
    int hdrlen = sdsHdrSize(type); // 获取sds头部大小
    unsigned char *fp; /* flags pointer. */

    // 为sds分配内存,总大小为:头部大小+存储字符串的长度+末尾隐含的空字符大小
    sh = s_malloc(hdrlen+initlen+1); 
    if (!init)
        memset(sh, 0, hdrlen+initlen+1); // 内存初始化为0
    if (sh == NULL) return NULL;
    s = (char*)sh+hdrlen; // buf数组的起始地址
    fp = ((unsigned char*)s)-1; // 指向flags字段
    // 初始化sds头部的len,alloc,flags字段
    switch(type) {
        case SDS_TYPE_5: {
            *fp = type | (initlen <len = initlen;
            sh->alloc = initlen;
            *fp = type;
            break;
        }
        case SDS_TYPE_16: {
            SDS_HDR_VAR(16,s);
            sh->len = initlen;
            sh->alloc = initlen;
            *fp = type;
            break;
        }
        case SDS_TYPE_32: {
            SDS_HDR_VAR(32,s);
            sh->len = initlen;
            sh->alloc = initlen;
            *fp = type;
            break;
        }
        case SDS_TYPE_64: {
            SDS_HDR_VAR(64,s);
            sh->len = initlen;
            sh->alloc = initlen;
            *fp = type;
            break;
        }
    }
    // 初始化buf数组
    if (initlen && init)
        memcpy(s, init, initlen); // 拷贝init到buf数组
    s[initlen] = ''; // 添加末尾的空字符
    return s;
}

/* Create an empty (zero length) sds string. Even in this case the string
 * always has an implicit null term. */
// 分配一个空的sds
sds sdsempty(void) {
    return sdsnewlen("",0);
}

/* Create a new sds string starting from a null terminated C string. */
// 分配一个新sds,以c字符串初始化其buf数组
sds sdsnew(const char *init) {
    size_t initlen = (init == NULL) ? 0 : strlen(init);
    return sdsnewlen(init, initlen);
}

/* Duplicate an sds string. */
// 复制一个sds
sds sdsdup(const sds s) {
    return sdsnewlen(s, sdslen(s));
}

/* Free an sds string. No operation is performed if 's' is NULL. */
// 释放一个sds
void sdsfree(sds s) {
    if (s == NULL) return;
    s_free((char*)s-sdsHdrSize(s[-1])); // 先移动到sds头部起始地址,再释放
}

/* Set the sds string length to the length as obtained with strlen(), so
 * considering as content only up to the first null term character.
 *
 * This function is useful when the sds string is hacked manually in some
 * way, like in the following example:
 *
 * s = sdsnew("foobar");
 * s[2] = '';
 * sdsupdatelen(s);
 * printf("%dn", sdslen(s));
 *
 * The output will be "2", but if we comment out the call to sdsupdatelen()
 * the output will be "6" as the string was modified but the logical length
 * remains 6 bytes. */
 
 // 以第1个''位置为sds长度,重新设置sds长度
 // 这样做目的是将第一个''后面的部分全部截断
void sdsupdatelen(sds s) {
    int reallen = strlen(s); // 以strlen()来计算长度,到第1个''截止
    sdssetlen(s, reallen);
}

/* Modify an sds string in-place to make it empty (zero length).
 * However all the existing buffer is not discarded but set as free space
 * so that next append operations will not require allocations up to the
 * number of bytes previously available. */
 
 // 清空sds内容,len字段清为0
 // 但之前的空间并未释放,可避免以后的重新分配内存。实现惰性空间释放
void sdsclear(sds s) {
    sdssetlen(s, 0);
    s[0] = '';
}

/* Enlarge the free space at the end of the sds string so that the caller
 * is sure that after calling this function can overwrite up to addlen
 * bytes after the end of the string, plus one more byte for nul term.
 *
 * Note: this does not change the *length* of the sds string as returned
 * by sdslen(), but only the free buffer space we have. */
 
 // 为sds的len字段增加addlen个字节,剩余空间不足时会引起空间重新分配
sds sdsMakeRoomFor(sds s, size_t addlen) {
    void *sh, *newsh;
    size_t avail = sdsavail(s);
    size_t len, newlen;
    char type, oldtype = s[-1] & SDS_TYPE_MASK;
    int hdrlen;

    /* Return ASAP if there is enough space left. */
    if (avail >= addlen) return s; // sds剩余空间足够

    len = sdslen(s);
    sh = (char*)s-sdsHdrSize(oldtype);
    newlen = (len+addlen); // sds剩余空间不够,新的len为len+addlen
    
    // 下面两步实现空间预分配
    if (newlen < SDS_MAX_PREALLOC) // 新长度小于1M,则len设为2*(len+addlen)大小
        newlen *= 2;
    else
        newlen += SDS_MAX_PREALLOC; // 新长度大于1M,则len设为 len+1M 大小

    type = sdsReqType(newlen); // 新len对应的sds头部

    /* Don't use type 5: the user is appending to the string and type 5 is
     * not able to remember empty space, so sdsMakeRoomFor() must be called
     * at every appending operation. */
    if (type == SDS_TYPE_5) type = SDS_TYPE_8;

    hdrlen = sdsHdrSize(type);
    if (oldtype==type) {
        newsh = s_realloc(sh, hdrlen+newlen+1);
        if (newsh == NULL) return NULL;
        s = (char*)newsh+hdrlen;
    } else {
        /* Since the header size changes, need to move the string forward,
         * and can't use realloc */
        newsh = s_malloc(hdrlen+newlen+1);
        if (newsh == NULL) return NULL;
        memcpy((char*)newsh+hdrlen, s, len+1);
        s_free(sh);
        s = (char*)newsh+hdrlen;
        s[-1] = type;
        sdssetlen(s, len);
    }
    sdssetalloc(s, newlen);
    return s;
}

/* Reallocate the sds string so that it has no free space at the end. The
 * contained string remains not altered, but next concatenation operations
 * will require a reallocation.
 *
 * After the call, the passed sds string is no longer valid and all the
 * references must be substituted with the new pointer returned by the call. */
sds sdsRemoveFreeSpace(sds s) {
    void *sh, *newsh;
    char type, oldtype = s[-1] & SDS_TYPE_MASK;
    int hdrlen;
    size_t len = sdslen(s);
    sh = (char*)s-sdsHdrSize(oldtype);

    type = sdsReqType(len);
    hdrlen = sdsHdrSize(type);
    if (oldtype==type) {
        newsh = s_realloc(sh, hdrlen+len+1);
        if (newsh == NULL) return NULL;
        s = (char*)newsh+hdrlen;
    } else {
        newsh = s_malloc(hdrlen+len+1);
        if (newsh == NULL) return NULL;
        memcpy((char*)newsh+hdrlen, s, len+1);
        s_free(sh);
        s = (char*)newsh+hdrlen;
        s[-1] = type;
        sdssetlen(s, len);
    }
    sdssetalloc(s, len);
    return s;
}

/* Return the total size of the allocation of the specifed sds string,
 * including:
 * 1) The sds header before the pointer.
 * 2) The string.
 * 3) The free buffer at the end if any.
 * 4) The implicit null term.
 */
 // 返回sds的总长度:sds头部+alloc字段+结尾的空字符
size_t sdsAllocSize(sds s) {
    size_t alloc = sdsalloc(s);
    return sdsHdrSize(s[-1])+alloc+1;
}

/* Return the pointer of the actual SDS allocation (normally SDS strings
 * are referenced by the start of the string buffer). */
 // 返回sds的起始地址
void *sdsAllocPtr(sds s) {
    return (void*) (s-sdsHdrSize(s[-1]));
}

/* Increment the sds length and decrements the left free space at the
 * end of the string according to 'incr'. Also set the null term
 * in the new end of the string.
 *
 * This function is used in order to fix the string length after the
 * user calls sdsMakeRoomFor(), writes something after the end of
 * the current string, and finally needs to set the new length.
 *
 * Note: it is possible to use a negative increment in order to
 * right-trim the string.
 *
 * Usage example:
 *
 * Using sdsIncrLen() and sdsMakeRoomFor() it is possible to mount the
 * following schema, to cat bytes coming from the kernel to the end of an
 * sds string without copying into an intermediate buffer:
 *
 * oldlen = sdslen(s);
 * s = sdsMakeRoomFor(s, BUFFER_SIZE);
 * nread = read(fd, s+oldlen, BUFFER_SIZE);
 * ... check for nread  0 && oldlen+incr < 32) || (incr = (unsigned int)(-incr)));
            *fp = SDS_TYPE_5 | ((oldlen+incr) <= 0 && sh->alloc-sh->len >= incr) || (incr len >= (unsigned int)(-incr)));
            len = (sh->len += incr);
            break;
        }
        case SDS_TYPE_16: {
            SDS_HDR_VAR(16,s);
            assert((incr >= 0 && sh->alloc-sh->len >= incr) || (incr len >= (unsigned int)(-incr)));
            len = (sh->len += incr);
            break;
        }
        case SDS_TYPE_32: {
            SDS_HDR_VAR(32,s);
            assert((incr >= 0 && sh->alloc-sh->len >= (unsigned int)incr) || (incr len >= (unsigned int)(-incr)));
            len = (sh->len += incr);
            break;
        }
        case SDS_TYPE_64: {
            SDS_HDR_VAR(64,s);
            assert((incr >= 0 && sh->alloc-sh->len >= (uint64_t)incr) || (incr len >= (uint64_t)(-incr)));
            len = (sh->len += incr);
            break;
        }
        default: len = 0; /* Just to avoid compilation warnings. */
    }
    s[len] = '';
}

/* Grow the sds to have the specified length. Bytes that were not part of
 * the original length of the sds will be set to zero.
 *
 * if the specified length is smaller than the current length, no operation
 * is performed. */
 
 // 为sds分配len大小的空间,len小于目前的len字段,则什么都不做
sds sdsgrowzero(sds s, size_t len) {
    size_t curlen = sdslen(s);

    if (len <= curlen) return s;
    s = sdsMakeRoomFor(s,len-curlen);
    if (s == NULL) return NULL;

    /* Make sure added region doesn't contain garbage */
    memset(s+curlen,0,(len-curlen+1)); /* also set trailing  byte */
    sdssetlen(s, len);
    return s;
}

/* Append the specified binary-safe string pointed by 't' of 'len' bytes to the
 * end of the specified sds string 's'.
 *
 * After the call, the passed sds string is no longer valid and all the
 * references must be substituted with the new pointer returned by the call. */
 
 // 在原sds后追加内容*t
sds sdscatlen(sds s, const void *t, size_t len) {
    size_t curlen = sdslen(s);

    s = sdsMakeRoomFor(s,len);
    if (s == NULL) return NULL;
    memcpy(s+curlen, t, len);
    sdssetlen(s, curlen+len);
    s[curlen+len] = '';
    return s;
}

/* Append the specified null termianted C string to the sds string 's'.
 *
 * After the call, the passed sds string is no longer valid and all the
 * references must be substituted with the new pointer returned by the call. */
 
 // 在原sds后追加字符串
sds sdscat(sds s, const char *t) {
    return sdscatlen(s, t, strlen(t));
}

/* Append the specified sds 't' to the existing sds 's'.
 *
 * After the call, the modified sds string is no longer valid and all the
 * references must be substituted with the new pointer returned by the call. */
 
  // 在原sds后追加sds
sds sdscatsds(sds s, const sds t) {
    return sdscatlen(s, t, sdslen(t));
}

/* Destructively modify the sds string 's' to hold the specified binary
 * safe string pointed by 't' of length 'len' bytes. */
 
 // 将长度为len的字符串*t拷贝到sds
sds sdscpylen(sds s, const char *t, size_t len) {
    if (sdsalloc(s)  string
 * conversion. 's' must point to a string with room for at least
 * SDS_LLSTR_SIZE bytes.
 *
 * The function returns the length of the null-terminated string
 * representation stored at 's'. */
#define SDS_LLSTR_SIZE 21

// 将一个long long类型的值转换为一个字符串
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 = '';

    /* 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. */

// 将一个unsigned long long类型的值转换为一个字符串
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 = '';

    /* Reverse the string. */
    p--;
    while(s 

sizeof(staticbuf)) { buf = s_malloc(buflen); if (buf == NULL) return NULL; } else { buflen = sizeof(staticbuf); } /* Try with buffers two times bigger every time we fail to * fit the string in the current buffer size. */ while(1) { buf[buflen-2] = ''; va_copy(cpy,ap); vsnprintf(buf, buflen, fmt, cpy); va_end(cpy); if (buf[buflen-2] != '') { if (buf != staticbuf) s_free(buf); buflen *= 2; buf = s_malloc(buflen); if (buf == NULL) return NULL; continue; } break; } /* Finally concat the obtained string to the SDS string and return it. */ t = sdscat(s, buf); if (buf != staticbuf) s_free(buf); return t; } /* Append to the sds string 's' a string obtained using printf-alike format * specifier. * * After the call, the modified sds string is no longer valid and all the * references must be substituted with the new pointer returned by the call. * * Example: * * s = sdsnew("Sum is: "); * s = sdscatprintf(s,"%d+%d = %d",a,b,a+b). * * Often you need to create a string from scratch with the printf-alike * format. When this is the need, just use sdsempty() as the target string: * * s = sdscatprintf(sdsempty(), "... your format ...", args); */ // 打印不定参数的内容到sds sds sdscatprintf(sds s, const char *fmt, ...) { va_list ap; char *t; va_start(ap, fmt); t = sdscatvprintf(s,fmt,ap); va_end(ap); return t; } /* This function is similar to sdscatprintf, but much faster as it does * not rely on sprintf() family functions implemented by the libc that * are often very slow. Moreover directly handling the sds string as * new data is concatenated provides a performance improvement. * * However this function only handles an incompatible subset of printf-alike * format specifiers: * * %s - C String * %S - SDS string * %i - signed int * %I - 64 bit signed integer (long long, int64_t) * %u - unsigned int * %U - 64 bit unsigned integer (unsigned long long, uint64_t) * %% - Verbatim "%" character. */ // 格式化输出字符串到sds sds sdscatfmt(sds s, char const *fmt, ...) { size_t initlen = sdslen(s); const char *f = fmt; int i; va_list ap; va_start(ap,fmt); f = fmt; /* Next format specifier byte to process. */ i = initlen; /* Position of the next byte to write to dest str. */ while(*f) { char next, *str; size_t l; long long num; unsigned long long unum; /* Make sure there is always space for at least 1 char. */ if (sdsavail(s)==0) { s = sdsMakeRoomFor(s,1); } switch(*f) { case '%': next = *(f+1); f++; switch(next) { case 's': case 'S': str = va_arg(ap,char*); l = (next == 's') ? strlen(str) : sdslen(str); if (sdsavail(s) < l) { s = sdsMakeRoomFor(s,l); } memcpy(s+i,str,l); sdsinclen(s,l); i += l; break; case 'i': case 'I': if (next == 'i') num = va_arg(ap,int); else num = va_arg(ap,long long); { char buf[SDS_LLSTR_SIZE]; l = sdsll2str(buf,num); if (sdsavail(s) < l) { s = sdsMakeRoomFor(s,l); } memcpy(s+i,buf,l); sdsinclen(s,l); i += l; } break; case 'u': case 'U': if (next == 'u') unum = va_arg(ap,unsigned int); else unum = va_arg(ap,unsigned long long); { char buf[SDS_LLSTR_SIZE]; l = sdsull2str(buf,unum); if (sdsavail(s) < l) { s = sdsMakeRoomFor(s,l); } memcpy(s+i,buf,l); sdsinclen(s,l); i += l; } break; default: /* Handle %% and generally %. */ s[i++] = next; sdsinclen(s,1); break; } break; default: s[i++] = *f; sdsinclen(s,1); break; } f++; } va_end(ap); /* Add null-term */ s[i] = ''; return s; } /* Remove the part of the string from left and from right composed just of * contiguous characters found in 'cset', that is a null terminted C string. * * After the call, the modified sds string is no longer valid and all the * references must be substituted with the new pointer returned by the call. * * Example: * * s = sdsnew("AA...AA.a.aa.aHelloWorld :::"); * s = sdstrim(s,"Aa. :"); * printf("%sn", s); * * Output will be just "Hello World". */ sds sdstrim(sds s, const char *cset) { char *start, *end, *sp, *ep; size_t len; sp = start = s; ep = end = s+sdslen(s)-1; while(sp sp && strchr(cset, *ep)) ep--; len = (sp > ep) ? 0 : ((ep-sp)+1); if (s != sp) memmove(s, sp, len); s[len] = ''; sdssetlen(s,len); return s; } /* Turn the string into a smaller (or equal) string containing only the * substring specified by the 'start' and 'end' indexes. * * start and end can be negative, where -1 means the last character of the * string, -2 the penultimate character, and so forth. * * The interval is inclusive, so the start and end characters will be part * of the resulting string. * * The string is modified in-place. * * Example: * * s = sdsnew("Hello World"); * sdsrange(s,1,-1); => "ello World" */ void sdsrange(sds s, int start, int end) { size_t newlen, len = sdslen(s); if (len == 0) return; if (start < 0) { start = len+start; if (start < 0) start = 0; } if (end < 0) { end = len+end; if (end end) ? 0 : (end-start)+1; if (newlen != 0) { if (start >= (signed)len) { newlen = 0; } else if (end >= (signed)len) { end = len-1; newlen = (start > end) ? 0 : (end-start)+1; } } else { start = 0; } if (start && newlen) memmove(s, s+start, newlen); s[newlen] = 0; sdssetlen(s,newlen); } /* Apply tolower() to every character of the sds string 's'. */ void sdstolower(sds s) { int len = sdslen(s), j; for (j = 0; j < len; j++) s[j] = tolower(s[j]); } /* Apply toupper() to every character of the sds string 's'. */ void sdstoupper(sds s) { int len = sdslen(s), j; for (j = 0; j s2. * negative if s1 < s2. * 0 if s1 and s2 are exactly the same binary string. * * If two strings share exactly the same prefix, but one of the two has * additional characters, the longer string is considered to be greater than * the smaller one. */ int sdscmp(const sds s1, const sds s2) { size_t l1, l2, minlen; int cmp; l1 = sdslen(s1); l2 = sdslen(s2); minlen = (l1 < l2) ? l1 : l2; cmp = memcmp(s1,s2,minlen); if (cmp == 0) return l1-l2; return cmp; } /* Split 's' with separator in 'sep'. An array * of sds strings is returned. *count will be set * by reference to the number of tokens returned. * * On out of memory, zero length string, zero length * separator, NULL is returned. * * Note that 'sep' is able to split a string using * a multi-character separator. For example * sdssplit("foo_-_bar","_-_"); will return two * elements "foo" and "bar". * * This version of the function is binary-safe but * requires length arguments. sdssplit() is just the * same function but for zero-terminated strings. */ sds *sdssplitlen(const char *s, int len, const char *sep, int seplen, int *count) { int elements = 0, slots = 5, start = 0, j; sds *tokens; if (seplen < 1 || len < 0) return NULL; tokens = s_malloc(sizeof(sds)*slots); if (tokens == NULL) return NULL; if (len == 0) { *count = 0; return tokens; } for (j = 0; j < (len-(seplen-1)); j++) { /* make sure there is room for the next element and the final one */ if (slots < elements+2) { sds *newtokens; slots *= 2; newtokens = s_realloc(tokens,sizeof(sds)*slots); if (newtokens == NULL) goto cleanup; tokens = newtokens; } /* search the separator */ if ((seplen == 1 && *(s+j) == sep[0]) || (memcmp(s+j,sep,seplen) == 0)) { tokens[elements] = sdsnewlen(s+start,j-start); if (tokens[elements] == NULL) goto cleanup; elements++; start = j+seplen; j = j+seplen-1; /* skip the separator */ } } /* Add the final element. We are sure there is room in the tokens array. */ tokens[elements] = sdsnewlen(s+start,len-start); if (tokens[elements] == NULL) goto cleanup; elements++; *count = elements; return tokens; cleanup: { int i; for (i = 0; i < elements; i++) sdsfree(tokens[i]); s_free(tokens); *count = 0; return NULL; } } /* Free the result returned by sdssplitlen(), or do nothing if 'tokens' is NULL. */ void sdsfreesplitres(sds *tokens, int count) { if (!tokens) return; while(count--) sdsfree(tokens[count]); s_free(tokens); } /* Append to the sds string "s" an escaped string representation where * all the non-printable characters (tested with isprint()) are turned into * escapes in the form "nra...." or "x". * * After the call, the modified sds string is no longer valid and all the * references must be substituted with the new pointer returned by the call. */ sds sdscatrepr(sds s, const char *p, size_t len) { s = sdscatlen(s,""",1); while(len--) { switch(*p) { case '\': case '"': s = sdscatprintf(s,"\%c",*p); break; case 'n': s = sdscatlen(s,"\n",2); break; case 'r': s = sdscatlen(s,"\r",2); break; case 't': s = sdscatlen(s,"\t",2); break; case 'a': s = sdscatlen(s,"\a",2); break; case 'b': s = sdscatlen(s,"\b",2); break; default: if (isprint(*p)) s = sdscatprintf(s,"%c",*p); else s = sdscatprintf(s,"\x%02x",(unsigned char)*p); break; } p++; } return sdscatlen(s,""",1); } /* Helper function for sdssplitargs() that returns non zero if 'c' * is a valid hex digit. */ int is_hex_digit(char c) { return (c >= '0' && c = 'a' && c = 'A' && c <= 'F'); } /* Helper function for sdssplitargs() that converts a hex digit into an * integer from 0 to 15 */ int hex_digit_to_int(char c) { switch(c) { case '0': return 0; case '1': return 1; case '2': return 2; case '3': return 3; case '4': return 4; case '5': return 5; case '6': return 6; case '7': return 7; case '8': return 8; case '9': return 9; case 'a': case 'A': return 10; case 'b': case 'B': return 11; case 'c': case 'C': return 12; case 'd': case 'D': return 13; case 'e': case 'E': return 14; case 'f': case 'F': return 15; default: return 0; } } /* Split a line into arguments, where every argument can be in the * following programming-language REPL-alike form: * * foo bar "newline are supportedn" and "xffx00otherstuff" * * The number of arguments is stored into *argc, and an array * of sds is returned. * * The caller should free the resulting array of sds strings with * sdsfreesplitres(). * * Note that sdscatrepr() is able to convert back a string into * a quoted string in the same format sdssplitargs() is able to parse. * * The function returns the allocated tokens on success, even when the * input string is empty, or NULL if the input contains unbalanced * quotes or closed quotes followed by non space characters * as in: "foo"bar or "foo' */ sds *sdssplitargs(const char *line, int *argc) { const char *p = line; char *current = NULL; char **vector = NULL; *argc = 0; while(1) { /* skip blanks */ while(*p && isspace(*p)) p++; if (*p) { /* get a token */ int inq=0; /* set to 1 if we are in "quotes" */ int insq=0; /* set to 1 if we are in 'single quotes' */ int done=0; if (current == NULL) current = sdsempty(); while(!done) { if (inq) { if (*p == '\' && *(p+1) == 'x' && is_hex_digit(*(p+2)) && is_hex_digit(*(p+3))) { unsigned char byte; byte = (hex_digit_to_int(*(p+2))*16)+ hex_digit_to_int(*(p+3)); current = sdscatlen(current,(char*)&byte,1); p += 3; } else if (*p == '\' && *(p+1)) { char c; p++; switch(*p) { case 'n': c = 'n'; break; case 'r': c = 'r'; break; case 't': c = 't'; break; case 'b': c = 'b'; break; case 'a': c = 'a'; break; default: c = *p; break; } current = sdscatlen(current,&c,1); } else if (*p == '"') { /* closing quote must be followed by a space or * nothing at all. */ if (*(p+1) && !isspace(*(p+1))) goto err; done=1; } else if (!*p) { /* unterminated quotes */ goto err; } else { current = sdscatlen(current,p,1); } } else if (insq) { if (*p == '\' && *(p+1) == ''') { p++; current = sdscatlen(current,"'",1); } else if (*p == ''') { /* closing quote must be followed by a space or * nothing at all. */ if (*(p+1) && !isspace(*(p+1))) goto err; done=1; } else if (!*p) { /* unterminated quotes */ goto err; } else { current = sdscatlen(current,p,1); } } else { switch(*p) { case ' ': case 'n': case 'r': case 't': case '': done=1; break; case '"': inq=1; break; case ''': insq=1; break; default: current = sdscatlen(current,p,1); break; } } if (*p) p++; } /* add the token to the vector */ vector = s_realloc(vector,((*argc)+1)*sizeof(char*)); vector[*argc] = current; (*argc)++; current = NULL; } else { /* Even on empty input string return something not NULL. */ if (vector == NULL) vector = s_malloc(sizeof(void*)); return vector; } } err: while((*argc)--) sdsfree(vector[*argc]); s_free(vector); if (current) sdsfree(current); *argc = 0; return NULL; } /* Modify the string substituting all the occurrences of the set of * characters specified in the 'from' string to the corresponding character * in the 'to' array. * * For instance: sdsmapchars(mystring, "ho", "01", 2) * will have the effect of turning the string "hello" into "0ell1". * * The function returns the sds string pointer, that is always the same * as the input pointer since no resize is needed. */ sds sdsmapchars(sds s, const char *from, const char *to, size_t setlen) { size_t j, i, l = sdslen(s); for (j = 0; j < l; j++) { for (i = 0; i < setlen; i++) { if (s[j] == from[i]) { s[j] = to[i]; break; } } } return s; } /* Join an array of C strings using the specified separator (also a C string). * Returns the result as an sds string. */ sds sdsjoin(char **argv, int argc, char *sep) { sds join = sdsempty(); int j; for (j = 0; j < argc; j++) { join = sdscat(join, argv[j]); if (j != argc-1) join = sdscat(join,sep); } return join; } /* Like sdsjoin, but joins an array of SDS strings. */ sds sdsjoinsds(sds *argv, int argc, const char *sep, size_t seplen) { sds join = sdsempty(); int j; for (j = 0; j < argc; j++) { join = sdscatsds(join, argv[j]); if (j != argc-1) join = sdscatlen(join,sep,seplen); } return join; } /* Wrappers to the allocators used by SDS. Note that SDS will actually * just use the macros defined into sdsalloc.h in order to avoid to pay * the overhead of function calls. Here we define these wrappers only for * the programs SDS is linked to, if they want to touch the SDS internals * even if they use a different allocator. */ void *sds_malloc(size_t size) { return s_malloc(size); } void *sds_realloc(void *ptr, size_t size) { return s_realloc(ptr,size); } void sds_free(void *ptr) { s_free(ptr); } #if defined(SDS_TEST_MAIN) #include #include "testhelp.h" #include "limits.h" #define UNUSED(x) (void)(x) int sdsTest(void) { { sds x = sdsnew("foo"), y; test_cond("Create a string and obtain the length", sdslen(x) == 3 && memcmp(x,"foo",4) == 0) sdsfree(x); x = sdsnewlen("foo",2); test_cond("Create a string with specified length", sdslen(x) == 2 && memcmp(x,"fo",3) == 0) x = sdscat(x,"bar"); test_cond("Strings concatenation", sdslen(x) == 5 && memcmp(x,"fobar",6) == 0); x = sdscpy(x,"a"); test_cond("sdscpy() against an originally longer string", sdslen(x) == 1 && memcmp(x,"a",2) == 0) x = sdscpy(x,"xyzxxxxxxxxxxyyyyyyyyyykkkkkkkkkk"); test_cond("sdscpy() against an originally shorter string", sdslen(x) == 33 && memcmp(x,"xyzxxxxxxxxxxyyyyyyyyyykkkkkkkkkk",33) == 0) sdsfree(x); x = sdscatprintf(sdsempty(),"%d",123); test_cond("sdscatprintf() seems working in the base case", sdslen(x) == 3 && memcmp(x,"123",4) == 0) sdsfree(x); x = sdsnew("--"); x = sdscatfmt(x, "Hello %s World %I,%I--", "Hi!", LLONG_MIN,LLONG_MAX); test_cond("sdscatfmt() seems working in the base case", sdslen(x) == 60 && memcmp(x,"--Hello Hi! World -9223372036854775808," "9223372036854775807--",60) == 0) printf("[%s]n",x); sdsfree(x); x = sdsnew("--"); x = sdscatfmt(x, "%u,%U--", UINT_MAX, ULLONG_MAX); test_cond("sdscatfmt() seems working with unsigned numbers", sdslen(x) == 35 && memcmp(x,"--4294967295,18446744073709551615--",35) == 0) sdsfree(x); x = sdsnew(" x "); sdstrim(x," x"); test_cond("sdstrim() works when all chars match", sdslen(x) == 0) sdsfree(x); x = sdsnew(" x "); sdstrim(x," "); test_cond("sdstrim() works when a single char remains", sdslen(x) == 1 && x[0] == 'x') sdsfree(x); x = sdsnew("xxciaoyyy"); sdstrim(x,"xy"); test_cond("sdstrim() correctly trims characters", sdslen(x) == 4 && memcmp(x,"ciao",5) == 0) y = sdsdup(x); sdsrange(y,1,1); test_cond("sdsrange(...,1,1)", sdslen(y) == 1 && memcmp(y,"i",2) == 0) sdsfree(y); y = sdsdup(x); sdsrange(y,1,-1); test_cond("sdsrange(...,1,-1)", sdslen(y) == 3 && memcmp(y,"iao",4) == 0) sdsfree(y); y = sdsdup(x); sdsrange(y,-2,-1); test_cond("sdsrange(...,-2,-1)", sdslen(y) == 2 && memcmp(y,"ao",3) == 0) sdsfree(y); y = sdsdup(x); sdsrange(y,2,1); test_cond("sdsrange(...,2,1)", sdslen(y) == 0 && memcmp(y,"",1) == 0) sdsfree(y); y = sdsdup(x); sdsrange(y,1,100); test_cond("sdsrange(...,1,100)", sdslen(y) == 3 && memcmp(y,"iao",4) == 0) sdsfree(y); y = sdsdup(x); sdsrange(y,100,100); test_cond("sdsrange(...,100,100)", sdslen(y) == 0 && memcmp(y,"",1) == 0) sdsfree(y); sdsfree(x); x = sdsnew("foo"); y = sdsnew("foa"); test_cond("sdscmp(foo,foa)", sdscmp(x,y) > 0) sdsfree(y); sdsfree(x); x = sdsnew("bar"); y = sdsnew("bar"); test_cond("sdscmp(bar,bar)", sdscmp(x,y) == 0) sdsfree(y); sdsfree(x); x = sdsnew("aar"); y = sdsnew("bar"); test_cond("sdscmp(bar,bar)", sdscmp(x,y) < 0) sdsfree(y); sdsfree(x); x = sdsnewlen("anfoor",7); y = sdscatrepr(sdsempty(),x,sdslen(x)); test_cond("sdscatrepr(...data...)", memcmp(y,""\a\n\x00foo\r"",15) == 0) { unsigned int oldfree; char *p; int step = 10, j, i; sdsfree(x); sdsfree(y); x = sdsnew("0"); test_cond("sdsnew() free/len buffers", sdslen(x) == 1 && sdsavail(x) == 0); /* Run the test a few times in order to hit the first two * SDS header types. */ for (i = 0; i = step); oldfree = sdsavail(x); } p = x+oldlen; for (j = 0; j < step; j++) { p[j] = 'A'+j; } sdsIncrLen(x,step); } test_cond("sdsMakeRoomFor() content", memcmp("0ABCDEFGHIJABCDEFGHIJABCDEFGHIJABCDEFGHIJABCDEFGHIJABCDEFGHIJABCDEFGHIJABCDEFGHIJABCDEFGHIJABCDEFGHIJ",x,101) == 0); test_cond("sdsMakeRoomFor() final length",sdslen(x)==101); sdsfree(x); } } test_report() return 0; } #endif #ifdef SDS_TEST_MAIN int main(void) { return sdsTest(); } #endif View Code

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