sds.h

/* SDSLib 2.0 -- A C dynamic strings library
 *
 * Copyright (c) 2006-2015, Salvatore Sanfilippo <antirez at gmail dot com>
 * Copyright (c) 2015, Oran Agra
 * Copyright (c) 2015, Redis Labs, Inc
 * 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

#define SDS_MAX_PREALLOC (1024*1024)
extern const char *SDS_NOINIT;

#include <sys/types.h>
#include <stdarg.h>
#include <stdint.h>

typedef char *sds; /* Simple Dynamic String 简单动态字符串 */

/* __packed__ 取消结构在编译过程中的优化对齐，按照实际占用字节数进行内存分配
 * SDS 数据结构定义：<len><alloc><flags><buf>
 * 特性1：sds 指针是直接指向 buf 字节数组，使得 SDS 可以直接使用 C 语言 string.h 库中的函数
 * 特性2：并且根据 buf 前进一位就能直接获取 flags，从而快速拿到类型，例如 `unsigned char flags = s[-1]`
 * */

/* 注意: sdshdr5 从未被使用, 我们仅访问 flags 字节.
 * 虽说如此, 这里还是记录一下 SDS5 字符串的空间布局. */
struct __attribute__ ((__packed__)) sdshdr5 {
    unsigned char flags; /* 3 个最低有效位表示类型, 同时 5 个最高有效位表示字符串长度 */
    char buf[];
};
struct __attribute__ ((__packed__)) sdshdr8 {
    uint8_t len; /* 已使用的长度 */
    uint8_t alloc; /* 不包含头部和空终止符号(\0) */
    unsigned char flags; /* 3位最低有效位表示类型, 其余5个比特位未被使用 */
    char buf[];
};
struct __attribute__ ((__packed__)) sdshdr16 {
    uint16_t len; /* 已使用的长度 */
    uint16_t alloc; /* 不包含头部和空终止符号 */
    unsigned char flags; /* 3位最低有效位表示类型, 其余5个比特位未被使用 */
    char buf[];
};
struct __attribute__ ((__packed__)) sdshdr32 {
    uint32_t len; /* 已使用的长度 */
    uint32_t alloc; /* 不包含头部和空终止符号 */
    unsigned char flags; /* 3位最低有效位表示类型, 其余5个比特位未被使用 */
    char buf[];
};
struct __attribute__ ((__packed__)) sdshdr64 {
    uint64_t len; /* 已使用的长度 */
    uint64_t alloc; /* 不包含头部和空终止符号 */
    unsigned char flags; /* 3位最低有效位表示类型, 其余5个比特位未被使用 */
    char buf[];
};

#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 /* 0b0111 三位最低有效位的 SDS 类型掩码 */
#define SDS_TYPE_BITS 3
/* 获取指向 SDS 头部的指针并将其复制给相应 SDS 类型的指针变量 sh */
#define SDS_HDR_VAR(T,s) struct sdshdr##T *sh = (void*)((s)-(sizeof(struct sdshdr##T)));
/* HDR header 这个宏的作用是获取SDS的头部的指针 */
#define SDS_HDR(T,s) ((struct sdshdr##T *)((s)-(sizeof(struct sdshdr##T))))
#define SDS_TYPE_5_LEN(f) ((f)>>SDS_TYPE_BITS)

/* 获取 SDS 的长度 */
static inline size_t sdslen(const sds s) {
    unsigned char flags = s[-1]; /* 根据 sds 数据结构的定义，sds 的指针是指向 buf,前一个字节就是 flags，用作类型判断 */
    switch(flags&SDS_TYPE_MASK) { /* & 0b0111 取出3位低有效位中的类型 */
        case SDS_TYPE_5:
            return SDS_TYPE_5_LEN(flags);
        case SDS_TYPE_8:
            return SDS_HDR(8,s)->len;
        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;
}

/* 剩余可用的柔性数组的大小 */
static inline size_t sdsavail(const sds s) {
    unsigned char flags = s[-1];
    switch(flags&SDS_TYPE_MASK) {
        case SDS_TYPE_5: { /* 暂未使用 buf 字段 */
            return 0;
        }
        case SDS_TYPE_8: {
            SDS_HDR_VAR(8,s);
            return sh->alloc - sh->len;
        }
        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;
}

/* 为一个 SDS 的变量 s 设置新的一个长度值 newlen */
static inline void sdssetlen(sds s, size_t newlen) {
    unsigned char flags = s[-1];
    switch(flags&SDS_TYPE_MASK) {
        case SDS_TYPE_5:
            {
                unsigned char *fp = ((unsigned char*)s)-1;
                *fp = SDS_TYPE_5 | (newlen << SDS_TYPE_BITS);
            }
            break;
        case SDS_TYPE_8:
            SDS_HDR(8,s)->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;
    }
}

/* 将一个 SDS 变量 s 的长度增加 inc */
static inline void sdsinclen(sds s, size_t inc) {
    unsigned char flags = s[-1];
    switch(flags&SDS_TYPE_MASK) {
        case SDS_TYPE_5:
            {
                unsigned char *fp = ((unsigned char*)s)-1;
                unsigned char newlen = SDS_TYPE_5_LEN(flags)+inc;
                *fp = SDS_TYPE_5 | (newlen << SDS_TYPE_BITS);
            }
            break;
        case SDS_TYPE_8:
            SDS_HDR(8,s)->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() */
/* 获取分配给 SDS 类型变量 s 的空间大小 */
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;
}

/* 将一个 SDS 变量 s 记录的分配空间大小设置为 newlen */
static inline void sdssetalloc(sds s, size_t newlen) {
    unsigned char flags = s[-1];
    switch(flags&SDS_TYPE_MASK) {
        case SDS_TYPE_5:
            /* 什么也不做, 这个类型没有总空间分配记录. */
            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 sdstrynewlen(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 sdssubstr(sds s, size_t start, size_t len);
void sdsrange(sds s, ssize_t start, ssize_t end);
void sdsupdatelen(sds s);
void sdsclear(sds s);
int sdscmp(const sds s1, const sds s2);
sds *sdssplitlen(const char *s, ssize_t 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);
int sdsneedsrepr(const sds s);

/* 为 sdstemplate 设置的回调函数. 每次, 当一个变量需要扩充自身时,
 * sdstemplate 都会调用该函数.
 * 变量名是作为变量提供的, 回调函数将返回一个替换值. 返回NULL表示错误.
 */
typedef sds (*sdstemplate_callback_t)(const sds variable, void *arg);
sds sdstemplate(const char *template, sdstemplate_callback_t cb_func, void *cb_arg);

/* 暴露给用户的底层接口 */
sds sdsMakeRoomFor(sds s, size_t addlen);
sds sdsMakeRoomForNonGreedy(sds s, size_t addlen);
void sdsIncrLen(sds s, ssize_t incr);
sds sdsRemoveFreeSpace(sds s);
sds sdsResize(sds s, size_t size);
size_t sdsAllocSize(sds s);
void *sdsAllocPtr(sds s);

/* 将SDS使用的分配器导出到使用SDS的程序中.
 * 有时链接到SDS的程序，可能使用了一组不同的分配器，但可能其想要完成的分配或释放任务是可以由SDS分别释放或分配的。
 */
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[], int flags);
#endif

#endif