【Redisソース解析】Redis内蔵データ構造の文字列sds

オリジナル作品は、転載して表示してください:http://blog.csdn.net/Xiejingfa/article/details/50972592
今日は一晩でRedisの文字列操作の実現を分析しました.ソースファイルはsds.hとsds.cです.まとめは以下の通りです
1、C言語では文字列は文字配列として具現化されています('\0'で終端符として)、Redisの文字列は次のように定義されています.

/*       （         ） */
struct sdshdr {
    //        
    unsigned int len;
    //       
    unsigned int free;
    //     （          ）
    char buf[];
};

実際に使用する場合、Redisは直接sdshdr構造を使用しないで、sdsタイプを定義してsdshdr構造を操作します.

/*  char *       sds */
typedef char *sds;

ここでsdsはsdshdr構造のbuf[]を指し、sdshdr構造全体を以下のように操作して得る.

//  sizeof(struct sdshdr)   8
/*        s-(sizeof(struct sdshdr))   sdshdr *  ？
             sds  sdshdr   buf[]    ，  
    s-(sizeof(struct sdshdr))  sdshdr     。
*/
struct sdshdr *sh = (void*)(s-(sizeof(struct sdshdr)));

2、Redisの文字置換操作はsdsmappers関数によって実現され、その原型は以下の通りである.

sds sdsmapchars(sds s, const char *from, const char *to, size_t setlen)

sdsmasharsが実行している文字の置き換え操作は、私たちが通常理解している文字とは少し違っています.fromに登場するsdsの文字をtoに置き換えます.
例えば、from=「ho」to=「01」s=「hello」sdsmappers処理後s=「0 ell 1」
3、Redisではsdscatvprintfを定義してフォーマット出力の文字列をソース文字列に接続していますが、その原型は以下の通りです.

sds sdscatvprintf(sds s, const char *fmt, va_list ap)

この方法は比較的興味深いものであり、出力をフォーマットする文字列を保存するために適切なサイズのバッファ領域を決定するために試行錯誤を続けている.具体的には後のソースコードを参照することができます.
Redisで定義されている文字列の操作関数は比較的簡単で、より詳細な注釈をしました.
sds.hヘッダの定義は以下の通りである.

/* SDSLib, A C dynamic strings library
 *
 * Copyright (c) 2006-2010, Salvatore Sanfilippo 
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   * Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *   * Neither the name of Redis nor the names of its contributors may be used
 *     to endorse or promote products derived from this software without
 *     specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef __SDS_H
#define __SDS_H

/*         1024*1024bytes = 1M */
#define SDS_MAX_PREALLOC (1024*1024)

#include 
#include 

/*  char *       sds */
typedef char *sds;

/*       （         ） */
struct sdshdr {
    //        
    unsigned int len;
    //       
    unsigned int free;
    //     （          ）
    char buf[];
};

/*       static  ，        */

/*         */
static inline size_t sdslen(const sds s) {
    //  sizeof(struct sdshdr)   8
    /*        s-(sizeof(struct sdshdr))   sdshdr *  ？
                 sds  sdshdr   buf[]    ，  
        s-(sizeof(struct sdshdr))  sdshdr     。
    */
    struct sdshdr *sh = (void*)(s-(sizeof(struct sdshdr)));
    return sh->len;
}

/*              */
static inline size_t sdsavail(const sds s) {
    //  sizeof(struct sdshdr)   8
    struct sdshdr *sh = (void*)(s-(sizeof(struct sdshdr)));
    return sh->free;
}

/*            ，      sds  sdshdr   buf[]    。  
     “  sds” “  sdshdr  ”    。
*/


/*         init             */
sds sdsnewlen(const void *init, size_t initlen);
/*         sds */
sds sdsnew(const char *init);
/*          */
sds sdsempty(void);
/*   sds  */
size_t sdslen(const sds s);
/*     sds */
sds sdsdup(const sds s);
/*   sds      */
void sdsfree(sds s);
/*   sds      */
size_t sdsavail(const 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
 /*      ，  C    sprintf   */
sds sdscatprintf(sds s, const char *fmt, ...);
#endif

/*          */
sds sdscatfmt(sds s, char const *fmt, ...);
/*     trim  ，         */
sds sdstrim(sds s, const char *cset);
/*       */
void sdsrange(sds s, int start, int end);
/*         ，        
    s = sdsnew("foobar");
    s[2] = '\0';
           sdsupdatelen(s)       ，     strlen       
 */
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);
/*   sdssplitlen     sds   */
void sdsfreesplitres(sds *tokens, int count);
/*           */
void sdstolower(sds s);
/*           */
void sdstoupper(sds s);
/*    long long            */
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);
/*    C                      */
sds sdsjoin(char **argv, int argc, char *sep);

/* Low level functions exposed to the user API */

/*   sds           addlen，                      */
sds sdsMakeRoomFor(sds s, size_t addlen);
/*       incr              */
void sdsIncrLen(sds s, int incr);
/*       buf      ，             */
sds sdsRemoveFreeSpace(sds s);
/*   sds         （     '\0'   ） */
size_t sdsAllocSize(sds s);

#endif

sds.cソースの定義は以下の通りです.

/* SDSLib, A C dynamic strings library
 *
 * Copyright (c) 2006-2012, Salvatore Sanfilippo 
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   * Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *   * Neither the name of Redis nor the names of its contributors may be used
 *     to endorse or promote products derived from this software without
 *     specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include 
#include 
#include 
#include 
#include 
#include "sds.h"
#include "zmalloc.h"

/* 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 \0 at the
 * end of the string. However the string is binary safe and can contain
 * \0 characters in the middle, as the length is stored in the sds header. */
sds sdsnewlen(const void *init, size_t initlen) {
    struct sdshdr *sh;

    //                    （       ）
    // +1                   ‘\0’
    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] = '\0';
    //      ，    sdshdr   buf[]
    return (char*)sh->buf;
}

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

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

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

/* Free an sds string. No operation is performed if 's' is NULL. */
/*   sds      */
void sdsfree(sds s) {
    if (s == NULL) return;
    zfree(s-sizeof(struct sdshdr));
}

/* 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] = '\0';
 * sdsupdatelen(s);
 * printf("%d
", 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. */

/*         ，        
    s = sdsnew("foobar");
    s[2] = '\0';
           sdsupdatelen(s)       ，     strlen       
 */
void sdsupdatelen(sds s) {
    struct sdshdr *sh = (void*) (s-(sizeof(struct sdshdr)));
    int reallen = strlen(s);
    sh->free += (sh->len-reallen);
    sh->len = 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. */
 /*       */
void sdsclear(sds s) {
    struct sdshdr *sh = (void*) (s-(sizeof(struct sdshdr)));
    //       、    
    sh->free += sh->len;
    sh->len = 0;
    sh->buf[0] = '\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. */
 /*   sds           addlen，                      */
sds sdsMakeRoomFor(sds s, size_t addlen) {
    struct sdshdr *sh, *newsh;
    size_t free = sdsavail(s);
    size_t len, newlen;

    //         ，    
    if (free >= addlen) return s;
    len = sdslen(s);
    sh = (void*) (s-(sizeof(struct sdshdr)));
    //                       ，    2        。     STL  vector
    newlen = (len+addlen);
    if (newlen < SDS_MAX_PREALLOC)
        newlen *= 2;
    else
        newlen += SDS_MAX_PREALLOC;
    //   zrealloc         
    newsh = zrealloc(sh, sizeof(struct sdshdr)+newlen+1);
    if (newsh == NULL) return NULL;

    //       
    newsh->free = newlen - len;
    return newsh->buf;
}

/* 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. */
 /*       buf      ，             */
sds sdsRemoveFreeSpace(sds s) {
    struct sdshdr *sh;

    sh = (void*) (s-(sizeof(struct sdshdr)));
    //       ，              （sizeof(struct sdshdr)+sh->len+1）
    sh = zrealloc(sh, sizeof(struct sdshdr)+sh->len+1);
    //             0
    sh->free = 0;
    return sh->buf;
}

/* 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.
 */
/*   sds         （     '\0'   ） */
size_t sdsAllocSize(sds s) {
    struct sdshdr *sh = (void*) (s-(sizeof(struct sdshdr)));

    return sizeof(*sh)+sh->len+sh->free+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 and handle it ...
 * sdsIncrLen(s, nread);
 */
 /*       incr              
        ：
        oldlen = sdslen(s);
        s = sdsMakeRoomFor(s, BUFFER_SIZE);
        nread = read(fd, s+oldlen, BUFFER_SIZE);
        ... check for nread <= 0 and handle it ...
        sdsIncrLen(s, nread);
 */
void sdsIncrLen(sds s, int incr) {
    struct sdshdr *sh = (void*) (s-(sizeof(struct sdshdr)));

    //     incr    ，               
    if (incr >= 0)
        assert(sh->free >= (unsigned int)incr);
    else
        assert(sh->len >= (unsigned int)(-incr));
    //       incr
    sh->len += incr;
    //       incr
    sh->free -= incr;
    s[sh->len] = '\0';
}

/* 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. */
 /*             */
sds sdsgrowzero(sds s, size_t len) {
    struct sdshdr *sh = (void*)(s-(sizeof(struct sdshdr)));
    size_t totlen, curlen = sh->len;

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

    /* Make sure added region doesn't contain garbage */
    //             0，        
    sh = (void*)(s-(sizeof(struct sdshdr)));
    memset(s+curlen,0,(len-curlen+1)); /* also set trailing \0 byte */
    //            
    totlen = sh->len+sh->free;
    sh->len = len;
    sh->free = totlen-sh->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. */
 /*     len    t   sds   */
sds sdscatlen(sds s, const void *t, size_t len) {
    struct sdshdr *sh;
    size_t curlen = sdslen(s);

    //   sds             t
    s = sdsMakeRoomFor(s,len);
    if (s == NULL) return NULL;
    sh = (void*) (s-(sizeof(struct sdshdr)));
    //     t   sds  
    memcpy(s+curlen, t, len);
    //            
    sh->len = curlen+len;
    sh->free = sh->free-len;
    //   '\0'   
    s[curlen+len] = '\0';
    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. */
/*     t   sds  ，     sdscatlen(sds s, const void *t, size_t len)   */
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. */
/*      sds t   sds s  ，     sdscatlen(sds s, const void *t, size_t len)   */
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. */
/*       len       sds  */
sds sdscpylen(sds s, const char *t, size_t len) {
    struct sdshdr *sh = (void*) (s-(sizeof(struct sdshdr)));
    size_t totlen = sh->free+sh->len; //         

    //                      t，             
    if (totlen < len) {
        //       
        s = sdsMakeRoomFor(s,len-sh->len);
        if (s == NULL) return NULL;
        sh = (void*) (s-(sizeof(struct sdshdr)));
        totlen = sh->free+sh->len;
    }
    //      
    memcpy(s, t, len);
    //            
    s[len] = '\0';
    sh->len = len;
    sh->free = totlen-len;
    return s;
}

/* Like sdscpylen() but 't' must be a null-termined string so that the length
 * of the string is obtained with strlen(). */
/*       t   sds ，    sdscpylen   */
sds sdscpy(sds s, const char *t) {
    return sdscpylen(s, t, strlen(t));
}

/* Helper for sdscatlonglong() doing the actual number -> 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
 /*    long long            */
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. */
    //      ，             ，          （ 123 => "321"）。
    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. */
/* sdsll2str   unsigned long long ， long long      */
int sdsull2str(char *s, unsigned long long v) {
    char *p, aux;
    size_t l;

    /* Generate the string representation, this method produces
     * an reversed string. */
    //   unsigned long long     
    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;
}

/* Create an sds string from a long long value. It is much faster than:
 *
 * sdscatprintf(sdsempty(),"%lld
", value);
 */
 /*    long long           sds */
sds sdsfromlonglong(long long value) {
    //             ，    sds
    char buf[SDS_LLSTR_SIZE];
    int len = sdsll2str(buf,value);

    return sdsnewlen(buf,len);
}


/*             ，  C    sprintf  。*/

/* Like sdscatprintf() but gets va_list instead of being variadic. */
/*                s   */
sds sdscatvprintf(sds s, const char *fmt, va_list ap) {
    /*          ，            */

    va_list cpy;
    char staticbuf[1024], *buf = staticbuf, *t;
    size_t buflen = strlen(fmt)*2;

    /* We try to start using a static buffer for speed.
     * If not possible we revert to heap allocation. */
    //   fmt       1024，            staticbuf，                
    if (buflen > sizeof(staticbuf)) {
        buf = zmalloc(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] = '\0';
        va_copy(cpy,ap);
        //           
        vsnprintf(buf, buflen, fmt, cpy);
        va_end(cpy);
        //            ，         ，            
        if (buf[buflen-2] != '\0') {
            if (buf != staticbuf) zfree(buf);
            buflen *= 2;
            buf = zmalloc(buflen);
            if (buf == NULL) return NULL;
            continue;
        }
        break;
    }

    /* Finally concat the obtained string to the SDS string and return it. */
    //                    s  
    t = sdscat(s, buf);
    if (buf != staticbuf) zfree(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);
 */
 /*   sdscatvprintf  ，          */
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.
 */
 /*       */
sds sdscatfmt(sds s, char const *fmt, ...) {
    struct sdshdr *sh = (void*) (s-(sizeof(struct sdshdr)));
    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;
        unsigned int l;
        long long num;
        unsigned long long unum;

        /* Make sure there is always space for at least 1 char. */
        //               
        if (sh->free == 0) {
            s = sdsMakeRoomFor(s,1);
            sh = (void*) (s-(sizeof(struct sdshdr)));
        }

        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 (sh->free < l) {
                    s = sdsMakeRoomFor(s,l);
                    sh = (void*) (s-(sizeof(struct sdshdr)));
                }
                memcpy(s+i,str,l);
                sh->len += l;
                sh->free -= 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 (sh->free < l) {
                        s = sdsMakeRoomFor(s,l);
                        sh = (void*) (s-(sizeof(struct sdshdr)));
                    }
                    memcpy(s+i,buf,l);
                    sh->len += l;
                    sh->free -= 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 (sh->free < l) {
                        s = sdsMakeRoomFor(s,l);
                        sh = (void*) (s-(sizeof(struct sdshdr)));
                    }
                    memcpy(s+i,buf,l);
                    sh->len += l;
                    sh->free -= l;
                    i += l;
                }
                break;
            default: /* Handle %% and generally %. */
                s[i++] = next;
                sh->len += 1;
                sh->free -= 1;
                break;
            }
            break;
        default:
            s[i++] = *f;
            sh->len += 1;
            sh->free -= 1;
            break;
        }
        f++;
    }
    va_end(ap);

    /* Add null-term */
    s[i] = '\0';
    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("%s
", s);
 *
 * Output will be just "Hello World".
 */
 /*     trim  ，                   ，  java.lang.String trim   */
sds sdstrim(sds s, const char *cset) {
    struct sdshdr *sh = (void*) (s-(sizeof(struct sdshdr)));
    char *start, *end, *sp, *ep;
    size_t len;

    sp = start = s;
    ep = end = s+sdslen(s)-1;
    //           cset      
    while(sp <= end && strchr(cset, *sp)) sp++;
    //           cset      
    while(ep > start && strchr(cset, *ep)) ep--;
    //        
    len = (sp > ep) ? 0 : ((ep-sp)+1);
    //     
    if (sh->buf != sp) memmove(sh->buf, sp, len);
    //            
    sh->buf[len] = '\0';
    sh->free = sh->free+(sh->len-len);
    sh->len = 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"
 */
 /*     start   end           */
void sdsrange(sds s, int start, int end) {
    struct sdshdr *sh = (void*) (s-(sizeof(struct sdshdr)));
    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 < 0) end = 0;
    }
    //         
    newlen = (start > end) ? 0 : (end-start)+1;
    //   start end         ，           
    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(sh->buf, sh->buf+start, newlen);
    //             
    sh->buf[newlen] = 0;
    sh->free = sh->free+(sh->len-newlen);
    sh->len = 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 < len; j++) s[j] = toupper(s[j]);
}

/* Compare two sds strings s1 and s2 with memcmp().
 *
 * Return value:
 *
 *     positive if s1 > 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. */
 /*        ，    memcmp   */
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.
 */
 /*        ，    sep    ，  sds  ，  ：  count         。
      java.lang.String spilt  
 */
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;

    //     ，          5 ，         
    tokens = zmalloc(sizeof(sds)*slots);
    //           
    if (tokens == NULL) return NULL;

    //      0，    
    if (len == 0) {
        *count = 0;
        return tokens;
    }
    //         。             sep    len-(seplen-1)
    for (j = 0; j < (len-(seplen-1)); j++) {
        /* make sure there is room for the next element and the final one */
        //                      +2  ，    
        if (slots < elements+2) {
            sds *newtokens;

            //            
            slots *= 2;
            newtokens = zrealloc(tokens,sizeof(sds)*slots);
            //     ，           
            if (newtokens == NULL) goto cleanup;
            //  tokens        
            tokens = newtokens;
        }
        /* search the separator */
        //                
        if ((seplen == 1 && *(s+j) == sep[0]) || (memcmp(s+j,sep,seplen) == 0)) {
            //        ，      sds
            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;

//            ，      tokens    ，             
cleanup:
    {
        int i;
        for (i = 0; i < elements; i++) sdsfree(tokens[i]);
        zfree(tokens);
        *count = 0;
        return NULL;
    }
}

/* Free the result returned by sdssplitlen(), or do nothing if 'tokens' is NULL. */
/*   sdssplitlen     sds   */
void sdsfreesplitres(sds *tokens, int count) {
    if (!tokens) return;
    while(count--)
        sdsfree(tokens[count]);
    zfree(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 "
\r\a...." 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 '
': s = sdscatlen(s,"\
",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 <= '9') || (c >= 'a' && c <= 'f') ||
           (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 supported
" and "\xff\x00otherstuff"
 *
 * 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'
 */
 /*      ，argc           */
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 */
            //        ，inq = 1
            int inq=0;  /* set to 1 if we are in "quotes" */
            //        ，insq = 1
            int insq=0; /* set to 1 if we are in 'single quotes' */
            int done=0;

            //   current == NULL，        
            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 = '
'; 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 '
':
                    case '\r':
                    case '\t':
                    case '\0':
                        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 
            vector = zrealloc(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 = zmalloc(sizeof(void*));
            return vector;
        }
    }

/*                   */
err:
    while((*argc)--)
        sdsfree(vector[*argc]);
    zfree(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. */
 /*        ，  from to           */
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++) {
            //        from   ，       to    
            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. */
/*    C                      */
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;
}


/*            */
#ifdef SDS_TEST_MAIN
#include 
#include "testhelp.h"
#include "limits.h"

int main(void) {
    {
        struct sdshdr *sh;
        sds x = sdsnew("foo"), y;

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

        sdsfree(x);
        x = sdsnewlen("foo",2);
        test_cond("Create a string with specified length",
            sdslen(x) == 2 && memcmp(x,"fo\0",3) == 0)

        x = sdscat(x,"bar");
        test_cond("Strings concatenation",
            sdslen(x) == 5 && memcmp(x,"fobar\0",6) == 0);

        x = sdscpy(x,"a");
        test_cond("sdscpy() against an originally longer string",
            sdslen(x) == 1 && memcmp(x,"a\0",2) == 0)

        x = sdscpy(x,"xyzxxxxxxxxxxyyyyyyyyyykkkkkkkkkk");
        test_cond("sdscpy() against an originally shorter string",
            sdslen(x) == 33 &&
            memcmp(x,"xyzxxxxxxxxxxyyyyyyyyyykkkkkkkkkk\0",33) == 0)

        sdsfree(x);
        x = sdscatprintf(sdsempty(),"%d",123);
        test_cond("sdscatprintf() seems working in the base case",
            sdslen(x) == 3 && memcmp(x,"123\0",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)

        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("xxciaoyyy");
        sdstrim(x,"xy");
        test_cond("sdstrim() correctly trims characters",
            sdslen(x) == 4 && memcmp(x,"ciao\0",5) == 0)

        y = sdsdup(x);
        sdsrange(y,1,1);
        test_cond("sdsrange(...,1,1)",
            sdslen(y) == 1 && memcmp(y,"i\0",2) == 0)

        sdsfree(y);
        y = sdsdup(x);
        sdsrange(y,1,-1);
        test_cond("sdsrange(...,1,-1)",
            sdslen(y) == 3 && memcmp(y,"iao\0",4) == 0)

        sdsfree(y);
        y = sdsdup(x);
        sdsrange(y,-2,-1);
        test_cond("sdsrange(...,-2,-1)",
            sdslen(y) == 2 && memcmp(y,"ao\0",3) == 0)

        sdsfree(y);
        y = sdsdup(x);
        sdsrange(y,2,1);
        test_cond("sdsrange(...,2,1)",
            sdslen(y) == 0 && memcmp(y,"\0",1) == 0)

        sdsfree(y);
        y = sdsdup(x);
        sdsrange(y,1,100);
        test_cond("sdsrange(...,1,100)",
            sdslen(y) == 3 && memcmp(y,"iao\0",4) == 0)

        sdsfree(y);
        y = sdsdup(x);
        sdsrange(y,100,100);
        test_cond("sdsrange(...,100,100)",
            sdslen(y) == 0 && memcmp(y,"\0",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("\a
\0foo\r",7);
        y = sdscatrepr(sdsempty(),x,sdslen(x));
        test_cond("sdscatrepr(...data...)",
            memcmp(y,"\"\\a\
\\x00foo\\r\"",15) == 0)

        {
            int oldfree;

            sdsfree(x);
            sdsfree(y);
            x = sdsnew("0");
            sh = (void*) (x-(sizeof(struct sdshdr)));
            test_cond("sdsnew() free/len buffers", sh->len == 1 && sh->free == 0);
            x = sdsMakeRoomFor(x,1);
            sh = (void*) (x-(sizeof(struct sdshdr)));
            test_cond("sdsMakeRoomFor()", sh->len == 1 && sh->free > 0);
            oldfree = sh->free;
            x[1] = '1';
            sdsIncrLen(x,1);
            test_cond("sdsIncrLen() -- content", x[0] == '0' && x[1] == '1');
            test_cond("sdsIncrLen() -- len", sh->len == 2);
            test_cond("sdsIncrLen() -- free", sh->free == oldfree-1);

            sdsfree(x);
        }
    }
    test_report()
    return 0;
}
#endif