作者推荐 |【Redis技术进阶之路】「原理系列开篇」揭秘高效存储模型与数据结构底层实现(SDS)(二)https://developer.aliyun.com/article/1471144
sds.h的源码预览
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/* 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; /* Note: sdshdr5 is never used, we just access the flags byte directly. * However is here to document the layout of type 5 SDS strings. */ 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[]; }; #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 #define SDS_HDR_VAR(T,s) struct sdshdr##T *sh = (void*)((s)-(sizeof(struct sdshdr##T))); #define SDS_HDR(T,s) ((struct sdshdr##T *)((s)-(sizeof(struct sdshdr##T)))) #define SDS_TYPE_5_LEN(f) ((f)>>SDS_TYPE_BITS) static inline size_t sdslen(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)->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; } static inline size_t sdsavail(const sds s) { unsigned char flags = s[-1]; switch(flags&SDS_TYPE_MASK) { case SDS_TYPE_5: { 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; } 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; } } 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() */ 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; } 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 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); /* Callback for sdstemplate. The function gets called by sdstemplate * every time a variable needs to be expanded. The variable name is * provided as variable, and the callback is expected to return a * substitution value. Returning a NULL indicates an error. */ typedef sds (*sdstemplate_callback_t)(const sds variable, void *arg); sds sdstemplate(const char *template, sdstemplate_callback_t cb_func, void *cb_arg); /* Low level functions exposed to the user API */ 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, int would_regrow); sds sdsResize(sds s, size_t size, int would_regrow); 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[], int flags); #endif #endif
总之,文章内容的技术分析主要基于对源码的深入研究和探索。通过这种方法,我们能够更好地理解技术的本质和性能特点,为实际应用提供有力的支持和指导。
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