1 /* SDSLib, A C dynamic strings library
2 *
3 * Copyright (c) 2006-2012, Salvatore Sanfilippo <antirez at gmail dot com>
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions are met:
8 *
9 * * Redistributions of source code must retain the above copyright notice,
10 * this list of conditions and the following disclaimer.
11 * * Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * * Neither the name of Redis nor the names of its contributors may be used
15 * to endorse or promote products derived from this software without
16 * specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
19 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
22 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
23 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
24 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
25 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
26 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
27 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
28 * POSSIBILITY OF SUCH DAMAGE.
29 */
30
31 #include <stdio.h>
32 #include <stdlib.h>
33 #include <string.h>
34 #include <ctype.h>
35 #include <assert.h>
36 #include "sds.h"
37 #include "zmalloc.h"
38
39 /* 创建一个指定长度的sds */
40 sds sdsnewlen(const void *init, size_t initlen) {
41 struct sdshdr *sh;
42
43 if (init) { /* 如果init不为NULL的话,则分配内存空间 */
44 sh = zmalloc(sizeof(struct sdshdr)+initlen+1);
45 } else { /* 如果init为NULL的话,则calloc()将分配的内存空间中的每一位都初始化为零 */
46 sh = zcalloc(sizeof(struct sdshdr)+initlen+1);
47 }
48
49 /* 内存不足,分配失败 */
50 if (sh == NULL) return NULL;
51
52 /* 更新属性,sh->len(已占用长度),sh->free(剩余可用长度) */
53 sh->len = initlen;
54 sh->free = 0;
55
56 if (initlen && init)
57 memcpy(sh->buf, init, initlen);
58
59 /* 加上终结符 */
60 sh->buf[initlen] = '\0';
61
62 /* 返回buf,而不是整个sdshdr */
63 return (char*)sh->buf;
64 }
65
66 /* 创建一个包含空字符串""的sds */
67 sds sdsempty(void) {
68 return sdsnewlen("",0);
69 }
70
71 /* 根据给定初始值init,创建sds */
72 sds sdsnew(const char *init) {
73 /* 如果init为NULL,那么创建一个buf内只包含\0终结符的sds */
74 size_t initlen = (init == NULL) ? 0 : strlen(init);
75 return sdsnewlen(init, initlen);
76 }
77
78 /* 复制sds的一个副本 */
79 sds sdsdup(const sds s) {
80 return sdsnewlen(s, sdslen(s));
81 }
82
83 /* 释放sds所对应的sdshdr结构的内容 */
84 void sdsfree(sds s) {
85 if (s == NULL) return;
86 zfree(s-sizeof(struct sdshdr));
87 }
88
89 /* 更新给定sds所对应的sdshdr结构的free和len属性 */
90 void sdsupdatelen(sds s) {
91 /* s - (sizeof(struct sdshdr))表示将指针向前移动到struct sdshdr的起点,从而得出一个指向 sdshdr 结构的指针 */
92 struct sdshdr *sh = (void*) (s-(sizeof(struct sdshdr)));
93
94 /* 计算正确的buf长度 */
95 int reallen = strlen(s);
96
97 /* 更新free和len属性 */
98 sh->free += (sh->len-reallen);
99 sh->len = reallen;
100 }
101
102 /* 清除给定sds buf中的内容,让它只包含一个\0终结符 */
103 void sdsclear(sds s) {
104 /* 使用指针运算，可以从sds值中计算出相应的sdshdr结构： */
105 struct sdshdr *sh = (void*) (s-(sizeof(struct sdshdr)));
106
107 /* 更新属性 */
108 sh->free += sh->len;
109 sh->len = 0;
110 sh->buf[0] = '\0';
111 }
112
113 /* Enlarge the free space at the end of the sds string so that the caller
114 * is sure that after calling this function can overwrite up to addlen
115 * bytes after the end of the string, plus one more byte for nul term.
116 *
117 * Note: this does not change the *size* of the sds string as returned
118 * by sdslen(), but only the free buffer space we have. */
119 /* 对sds的buf进行扩展,扩展的长度不少于addlen */
120 sds sdsMakeRoomFor(sds s, size_t addlen) {
121 struct sdshdr *sh, *newsh;
122 size_t free = sdsavail(s);
123 size_t len, newlen;
124
125 /* 剩余空间可满足需求,无需扩展 */
126 if (free >= addlen) return s;
127
128 /* 目前buf长度 */
129 len = sdslen(s);
130
131 sh = (void*) (s-(sizeof(struct sdshdr)));
132
133 /* 新buf长度 */
134 newlen = (len+addlen);
135
136 /* 如果新buf长度小于SDS_MAX_PREALLOC(1024*1024)长度时,将buf的长度设为新buf长度的两倍 */
137 if (newlen < SDS_MAX_PREALLOC)
138 newlen *= 2;
139 else
140 newlen += SDS_MAX_PREALLOC;
141 newsh = zrealloc(sh, sizeof(struct sdshdr)+newlen+1);
142 if (newsh == NULL) return NULL;
143
144 newsh->free = newlen - len;
145
146 /* 只返回字符串部分 */
147 return newsh->buf;
148 }
149
150 /* Reallocate the sds string so that it has no free space at the end. The
151 * contained string remains not altered, but next concatenation operations
152 * will require a reallocation. */
153 /* 在不改动sds buf内容的情况下,将buf内多余的空间释放出去。在对sds执行这个函数之后,下一次对这个sds的拼接操作必须需要一次内存分配 */
154 sds sdsRemoveFreeSpace(sds s) {
155 struct sdshdr *sh;
156
157 sh = (void*) (s-(sizeof(struct sdshdr)));
158 sh = zrealloc(sh, sizeof(struct sdshdr)+sh->len+1);
159
160 /* 修改buf长度为sh->len + 1,不保留任何多余空间 */
161 sh->free = 0;
162 return sh->buf;
163 }
164
165 /* 计算给定sds buf的内容长度(包括已使用和未使用的) */
166 size_t sdsAllocSize(sds s) {
167 struct sdshdr *sh = (void*) (s-(sizeof(struct sdshdr)));
168
169 return sizeof(*sh)+sh->len+sh->free+1;
170 }
171
172 /* Increment the sds length and decrements the left free space at the
173 * end of the string accordingly to 'incr'. Also set the null term
174 * in the new end of the string.
175 *
176 * This function is used in order to fix the string length after the
177 * user calls sdsMakeRoomFor(), writes something after the end of
178 * the current string, and finally needs to set the new length.
179 *
180 * Note: it is possible to use a negative increment in order to
181 * right-trim the string.
182 *
183 * Using sdsIncrLen() and sdsMakeRoomFor() it is possible to mount the
184 * following schema to cat bytes coming from the kernel to the end of an
185 * sds string new things without copying into an intermediate buffer:
186 *
187 * oldlen = sdslen(s);
188 * s = sdsMakeRoomFor(s, BUFFER_SIZE);
189 * nread = read(fd, s+oldlen, BUFFER_SIZE);
190 * ... check for nread <= 0 and handle it ...
191 * sdsIncrLen(s, nhread);
192 */
193 /*
194 * 在sds buf的右端添加incr个位置。
195 * 如果incr为负数时,可作为right-trim使用
196 *
197 * incr为正数的例子:
198 * hdr = sdshdr {
199 * len = 10;
200 * free = 10;
201 * buf = "Hello Moto\0";
202 * };
203 * sdsIncrLen(hdr->buf, 2);
204 * hdr = sdshdr {
205 * len = 12;
206 * free = 8;
207 * buf = "Hello Moto\0[ ]\0"
208 * };
209 * 这里的[ ]表示一个任意内容的byte.
210 *
211 * incr为负数的例子:
212 * hdr = sdshdr {
213 * len = 10;
214 * free = 10;
215 * buf = "Hello Moto\0"
216 * };
217 * sdsIncrLen(hdr->buf, -2);
218 * hdr = sdshdr {
219 * len = 8;
220 * free = 12;
221 * buf = "Hello Mo\0"
222 * };
223 */
224 void sdsIncrLen(sds s, int incr) {
225 struct sdshdr *sh = (void*) (s-(sizeof(struct sdshdr)));
226
227 assert(sh->free >= incr);
228 sh->len += incr;
229 sh->free -= incr;
230 assert(sh->free >= 0);
231 s[sh->len] = '\0';
232 }
233
234 /* Grow the sds to have the specified length. Bytes that were not part of
235 * the original length of the sds will be set to zero. */
236 /* 将sds的buf扩展至给定长度,无内容部分用\0填充 */
237 sds sdsgrowzero(sds s, size_t len) {
238 struct sdshdr *sh = (void*)(s-(sizeof(struct sdshdr)));
239 size_t totlen, curlen = sh->len;
240
241 /* 如果现有长度比给定长度要大,则无需扩展 */
242 if (len <= curlen) return s;
243
244 /* 扩展sds */
245 s = sdsMakeRoomFor(s,len-curlen);
246
247 if (s == NULL) return NULL;
248
249 /* Make sure added region doesn't contain garbage */
250 /* 使用\0来填充空位,确保空位中不包含垃圾数据 */
251 sh = (void*)(s-(sizeof(struct sdshdr)));
252 memset(s+curlen,0,(len-curlen+1)); /* also set trailing \0 byte */
253
254 /* 更新属性 */
255 totlen = sh->len+sh->free;
256 sh->len = len;
257 sh->free = totlen-sh->len;
258
259 return s;
260 }
261
262 /* 按给定长度扩展sds,并将t拼接到sds的末尾 */
263 sds sdscatlen(sds s, const void *t, size_t len) {
264 struct sdshdr *sh;
265 size_t curlen = sdslen(s);
266
267 s = sdsMakeRoomFor(s,len);
268 if (s == NULL) return NULL;
269 sh = (void*) (s-(sizeof(struct sdshdr)));
270
271 /* 将给定长度的t拼接到sds的末尾 */
272 memcpy(s+curlen, t, len);
273
274 /* 更新属性 */
275 sh->len = curlen+len;
276 sh->free = sh->free-len;
277
278 /* 终结符 */
279 s[curlen+len] = '\0';
280
281 return s;
282 }
283
284 /* 将一个char数组拼接到sds末尾 */
285 sds sdscat(sds s, const char *t) {
286 return sdscatlen(s, t, strlen(t));
287 }
288
289 /* 拼接两个sds */
290 sds sdscatsds(sds s, const sds t) {
291 return sdscatlen(s, t, sdslen(t));
292 }
293
294 /* 将一个char数组的前len个字节复制至sds,如果sds的buf不足以容纳要复制的内容,那么扩展buf的长度,让buf的长度大于等于len */
295 sds sdscpylen(sds s, const char *t, size_t len) {
296 struct sdshdr *sh = (void*) (s-(sizeof(struct sdshdr)));
297 size_t totlen = sh->free+sh->len;
298
299 if (totlen < len) {/* 扩展buf的长度,让它的长度大于等于len */
300 s = sdsMakeRoomFor(s,len-sh->len);
301 if (s == NULL) return NULL;
302 sh = (void*) (s-(sizeof(struct sdshdr)));
303 totlen = sh->free+sh->len;
304 }
305 memcpy(s, t, len);
306 s[len] = '\0';
307
308 /* 更新属性 */
309 sh->len = len;
310 sh->free = totlen-len;
311
312 return s;
313 }
314
315 /* 将一个char数组复制到sds */
316 sds sdscpy(sds s, const char *t) {
317 return sdscpylen(s, t, strlen(t));
318 }
319
320 /* 因为类似printf操作,事先不知道源串长度,因此采用一种类似启发式的方法,从16byte开始,按照倍数递增的方法来猜测长度,猜测长度时,是在倒数第二个字节处打了个标记('\0'),然后判断操作前后是否保持一致来判断是否空间够。好好看while循环,挺有意思的 */
321 sds sdscatvprintf(sds s, const char *fmt, va_list ap) {
322 va_list cpy;
323 char *buf, *t;
324 size_t buflen = 16;
325
326 while(1) {
327 buf = zmalloc(buflen);
328 if (buf == NULL) return NULL;
329 buf[buflen-2] = '\0';
330 va_copy(cpy,ap);
331 vsnprintf(buf, buflen, fmt, cpy);
332 if (buf[buflen-2] != '\0') {
333 zfree(buf);
334 buflen *= 2;
335 continue;
336 }
337 break;
338 }
339 t = sdscat(s, buf);
340 zfree(buf);
341 return t;
342 }
343
344 sds sdscatprintf(sds s, const char *fmt, ...) {
345 va_list ap;
346 char *t;
347 va_start(ap, fmt);
348 t = sdscatvprintf(s,fmt,ap);
349 va_end(ap);
350 return t;
351 }
352
353 sds sdstrim(sds s, const char *cset) {
354 struct sdshdr *sh = (void*) (s-(sizeof(struct sdshdr)));
355 char *start, *end, *sp, *ep;
356 size_t len;
357
358 sp = start = s;
359
360 /* 最后一个有意义的字节,非'\0' */
361 ep = end = s+sdslen(s)-1;
362
363 /* strchr()函数功能为:查找字符串s中首次出现字符c的位置;返回值:返回首次出现c位置的指针,返回的地址是字符串在内存中随机分配的地址再加上你搜索的字符在字符串的位置,如果不存在c则返回NULL */
364 /* 将头尾出现在字符串cset中的字符都删干净,*sp和*ep都是字符而非字符指针 */
365 while(sp <= end && strchr(cset, *sp)) sp++;
366 while(ep > start && strchr(cset, *ep)) ep--;
367
368 len = (sp > ep) ? 0 : ((ep-sp)+1);
369 if (sh->buf != sp) memmove(sh->buf, sp, len);/* 因为sp和sh->buf有可能重叠,所以用了memmove */
370 sh->buf[len] = '\0';
371
372 /* 更新属性 */
373 sh->free = sh->free+(sh->len-len);
374 sh->len = len;
375
376 /* 删除特定空间后,并不释放内存,只是增大sh->free */
377 return s;
378 }
379
380 sds sdsrange(sds s, int start, int end) {
381 struct sdshdr *sh = (void*) (s-(sizeof(struct sdshdr)));
382 size_t newlen, len = sdslen(s);
383
384 if (len == 0) return s;
385 if (start < 0) {
386 start = len+start;
387 if (start < 0) start = 0;
388 }
389 if (end < 0) {
390 end = len+end;
391 if (end < 0) end = 0;
392 }
393 newlen = (start > end) ? 0 : (end-start)+1;
394 if (newlen != 0) {
395 if (start >= (signed)len) {
396 newlen = 0;
397 } else if (end >= (signed)len) {
398 end = len-1;
399 newlen = (start > end) ? 0 : (end-start)+1;
400 }
401 } else {
402 start = 0;
403 }
404 if (start && newlen) memmove(sh->buf, sh->buf+start, newlen);
405 sh->buf[newlen] = 0;
406
407 /* 更新属性 */
408 sh->free = sh->free+(sh->len-newlen);
409 sh->len = newlen;
410
411 return s;
412 }
413
414 void sdstolower(sds s) {
415 int len = sdslen(s), j;
416
417 /* 逐个字符转为小写 */
418 for (j = 0; j < len; j++) s[j] = tolower(s[j]);
419 }
420
421 void sdstoupper(sds s) {
422 int len = sdslen(s), j;
423
424 /* 逐个字符转为大写 */
425 for (j = 0; j < len; j++) s[j] = toupper(s[j]);
426 }
427
428 /* 比较两个sds */
429 int sdscmp(const sds s1, const sds s2) {
430 size_t l1, l2, minlen;
431 int cmp;
432
433 l1 = sdslen(s1);
434 l2 = sdslen(s2);
435 minlen = (l1 < l2) ? l1 : l2;
436 cmp = memcmp(s1,s2,minlen);
437 if (cmp == 0) return l1-l2;
438 return cmp;
439 }
440
441 /* Split 's' with separator in 'sep'. An array
442 * of sds strings is returned. *count will be set
443 * by reference to the number of tokens returned.
444 *
445 * On out of memory, zero length string, zero length
446 * separator, NULL is returned.
447 *
448 * Note that 'sep' is able to split a string using
449 * a multi-character separator. For example
450 * sdssplit("foo_-_bar","_-_"); will return two
451 * elements "foo" and "bar".
452 *
453 * This version of the function is binary-safe but
454 * requires length arguments. sdssplit() is just the
455 * same function but for zero-terminated strings.
456 */
457 sds *sdssplitlen(const char *s, int len, const char *sep, int seplen, int *count) {
458 int elements = 0, slots = 5, start = 0, j;
459 sds *tokens;
460
461 if (seplen < 1 || len < 0) return NULL;
462
463 /* 先假设有5个tokens供返回。在这个函数里返回值叫tokens,但在后续的sdssplitargs里返回值被起名为vector,而且类型一个时sds*,一个是char*,本质一样 */
464 tokens = zmalloc(sizeof(sds)*slots);
465 if (tokens == NULL) return NULL;
466
467 if (len == 0) {
468 *count = 0;
469 return tokens;
470 }
471 for (j = 0; j < (len-(seplen-1)); j++) {
472 /* make sure there is room for the next element and the final one */
473 if (slots < elements+2) {
474 sds *newtokens;
475
476 slots *= 2;
477 newtokens = zrealloc(tokens,sizeof(sds)*slots);
478 if (newtokens == NULL) goto cleanup;
479 tokens = newtokens;
480 }
481 /* search the separator */
482 if ((seplen == 1 && *(s+j) == sep[0]) || (memcmp(s+j,sep,seplen) == 0)) {
483 tokens[elements] = sdsnewlen(s+start,j-start);
484 if (tokens[elements] == NULL) goto cleanup;
485 elements++;
486 start = j+seplen;
487 j = j+seplen-1; /* skip the separator */
488 }
489 }
490 /* Add the final element. We are sure there is room in the tokens array. */
491 tokens[elements] = sdsnewlen(s+start,len-start);
492 if (tokens[elements] == NULL) goto cleanup;
493 elements++;
494 *count = elements;
495 return tokens;
496
497 cleanup:
498 {
499 int i;
500 for (i = 0; i < elements; i++) sdsfree(tokens[i]);
501 zfree(tokens);
502 *count = 0;
503 return NULL;
504 }
505 }
506
507 void sdsfreesplitres(sds *tokens, int count) {
508 if (!tokens) return;
509 while(count--)
510 sdsfree(tokens[count]);
511 zfree(tokens);
512 }
513
514 /* 将long long转成字符串 */
515 sds sdsfromlonglong(long long value) {
516 char buf[32], *p;
517 unsigned long long v;
518
519 v = (value < 0) ? -value : value;
520 p = buf+31; /* point to the last character */
521 do {
522 *p-- = '0'+(v%10);
523 v /= 10;
524 } while(v);
525 if (value < 0) *p-- = '-';
526 p++;
527 return sdsnewlen(p,32-(p-buf));
528 }
529
530 /* 将参数p原封不动(做过处理的,时计算机认为合法的),保存在一个sds里,用于协议交换 */
531 sds sdscatrepr(sds s, const char *p, size_t len) {
532 s = sdscatlen(s,"\"",1);
533 while(len--) {
534 switch(*p) {
535 case '\\':
536 case '"':
537 s = sdscatprintf(s,"\\%c",*p);
538 break;
539 case '\n': s = sdscatlen(s,"\\n",2); break;
540 case '\r': s = sdscatlen(s,"\\r",2); break;
541 case '\t': s = sdscatlen(s,"\\t",2); break;
542 case '\a': s = sdscatlen(s,"\\a",2); break;
543 case '\b': s = sdscatlen(s,"\\b",2); break;
544 default:
545 if (isprint(*p))
546 s = sdscatprintf(s,"%c",*p);
547 else
548 s = sdscatprintf(s,"\\x%02x",(unsigned char)*p);
549 break;
550 }
551 p++;
552 }
553 return sdscatlen(s,"\"",1);
554 }
555
556 /* Helper function for sdssplitargs() that returns non zero if 'c'
557 * is a valid hex digit. */
558 int is_hex_digit(char c) {
559 return (c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') ||
560 (c >= 'A' && c <= 'F');
561 }
562
563 /* Helper function for sdssplitargs() that converts an hex digit into an
564 * integer from 0 to 15 */
565 /* 十六进制转换成十进制 */
566 int hex_digit_to_int(char c) {
567 switch(c) {
568 case '0': return 0;
569 case '1': return 1;
570 case '2': return 2;
571 case '3': return 3;
572 case '4': return 4;
573 case '5': return 5;
574 case '6': return 6;
575 case '7': return 7;
576 case '8': return 8;
577 case '9': return 9;
578 case 'a': case 'A': return 10;
579 case 'b': case 'B': return 11;
580 case 'c': case 'C': return 12;
581 case 'd': case 'D': return 13;
582 case 'e': case 'E': return 14;
583 case 'f': case 'F': return 15;
584 default: return 0;
585 }
586 }
587
588 /* Split a line into arguments, where every argument can be in the
589 * following programming-language REPL-alike form:
590 *
591 * foo bar "newline are supported\n" and "\xff\x00otherstuff"
592 *
593 * The number of arguments is stored into *argc, and an array
594 * of sds is returned.
595 *
596 * The caller should free the resulting array of sds strings with
597 * sdsfreesplitres().
598 *
599 * Note that sdscatrepr() is able to convert back a string into
600 * a quoted string in the same format sdssplitargs() is able to parse.
601 *
602 * The function returns the allocated tokens on success, even when the
603 * input string is empty, or NULL if the input contains unbalanced
604 * quotes or closed quotes followed by non space characters
605 * as in: "foo"bar or "foo'
606 */
607 sds *sdssplitargs(const char *line, int *argc) {
608 const char *p = line;
609 char *current = NULL;
610 char **vector = NULL;
611
612 *argc = 0;
613 while(1) {
614 /* skip blanks */
615 while(*p && isspace(*p)) p++;
616 if (*p) {
617 /* get a token */
618 int inq=0; /* set to 1 if we are in "quotes" */
619 int insq=0; /* set to 1 if we are in 'single quotes' */
620 int done=0;
621
622 if (current == NULL) current = sdsempty();
623 while(!done) {
624 if (inq) {
625 if (*p == '\\' && *(p+1) == 'x' &&
626 is_hex_digit(*(p+2)) &&
627 is_hex_digit(*(p+3)))
628 {
629 unsigned char byte;
630
631 byte = (hex_digit_to_int(*(p+2))*16)+
632 hex_digit_to_int(*(p+3));
633 current = sdscatlen(current,(char*)&byte,1);
634 p += 3;
635 } else if (*p == '\\' && *(p+1)) {
636 char c;
637
638 p++;
639 switch(*p) {
640 case 'n': c = '\n'; break;
641 case 'r': c = '\r'; break;
642 case 't': c = '\t'; break;
643 case 'b': c = '\b'; break;
644 case 'a': c = '\a'; break;
645 default: c = *p; break;
646 }
647 current = sdscatlen(current,&c,1);
648 } else if (*p == '"') {
649 /* closing quote must be followed by a space or
650 * nothing at all. */
651 if (*(p+1) && !isspace(*(p+1))) goto err;
652 done=1;
653 } else if (!*p) {
654 /* unterminated quotes */
655 goto err;
656 } else {
657 current = sdscatlen(current,p,1);
658 }
659 } else if (insq) {
660 if (*p == '\\' && *(p+1) == '\'') {
661 p++;
662 current = sdscatlen(current,"'",1);
663 } else if (*p == '\'') {
664 /* closing quote must be followed by a space or
665 * nothing at all. */
666 if (*(p+1) && !isspace(*(p+1))) goto err;
667 done=1;
668 } else if (!*p) {
669 /* unterminated quotes */
670 goto err;
671 } else {
672 current = sdscatlen(current,p,1);
673 }
674 } else {
675 switch(*p) {
676 case ' ':
677 case '\n':
678 case '\r':
679 case '\t':
680 case '\0':
681 done=1;
682 break;
683 case '"':
684 inq=1;
685 break;
686 case '\'':
687 insq=1;
688 break;
689 default:
690 current = sdscatlen(current,p,1);
691 break;
692 }
693 }
694 if (*p) p++;
695 }
696 /* add the token to the vector */
697 vector = zrealloc(vector,((*argc)+1)*sizeof(char*));
698 vector[*argc] = current;
699 (*argc)++;
700 current = NULL;
701 } else {
702 /* Even on empty input string return something not NULL. */
703 if (vector == NULL) vector = zmalloc(sizeof(void*));
704 return vector;
705 }
706 }
707
708 err:
709 while((*argc)--)
710 sdsfree(vector[*argc]);
711 zfree(vector);
712 if (current) sdsfree(current);
713 *argc = 0;
714 return NULL;
715 }
716
717 /* Modify the string substituting all the occurrences of the set of
718 * characters specified in the 'from' string to the corresponding character
719 * in the 'to' array.
720 *
721 * For instance: sdsmapchars(mystring, "ho", "01", 2)
722 * will have the effect of turning the string "hello" into "0ell1".
723 *
724 * The function returns the sds string pointer, that is always the same
725 * as the input pointer since no resize is needed. */
726 /* 遍历字符 */
727 sds sdsmapchars(sds s, const char *from, const char *to, size_t setlen) {
728 size_t j, i, l = sdslen(s);
729
730 for (j = 0; j < l; j++) {
731 for (i = 0; i < setlen; i++) {
732 if (s[j] == from[i]) {
733 s[j] = to[i];
734 break;
735 }
736 }
737 }
738 return s;
739 }
740
741 #ifdef SDS_TEST_MAIN
742 #include <stdio.h>
743 #include "testhelp.h"
744
745 int main(void) {
746 {
747 struct sdshdr *sh;
748 sds x = sdsnew("foo"), y;
749
750 test_cond("Create a string and obtain the length",
751 sdslen(x) == 3 && memcmp(x,"foo\0",4) == 0)
752
753 sdsfree(x);
754 x = sdsnewlen("foo",2);
755 test_cond("Create a string with specified length",
756 sdslen(x) == 2 && memcmp(x,"fo\0",3) == 0)
757
758 x = sdscat(x,"bar");
759 test_cond("Strings concatenation",
760 sdslen(x) == 5 && memcmp(x,"fobar\0",6) == 0);
761
762 x = sdscpy(x,"a");
763 test_cond("sdscpy() against an originally longer string",
764 sdslen(x) == 1 && memcmp(x,"a\0",2) == 0)
765
766 x = sdscpy(x,"xyzxxxxxxxxxxyyyyyyyyyykkkkkkkkkk");
767 test_cond("sdscpy() against an originally shorter string",
768 sdslen(x) == 33 &&
769 memcmp(x,"xyzxxxxxxxxxxyyyyyyyyyykkkkkkkkkk\0",33) == 0)
770
771 sdsfree(x);
772 x = sdscatprintf(sdsempty(),"%d",123);
773 test_cond("sdscatprintf() seems working in the base case",
774 sdslen(x) == 3 && memcmp(x,"123\0",4) ==0)
775
776 sdsfree(x);
777 x = sdstrim(sdsnew("xxciaoyyy"),"xy");
778 test_cond("sdstrim() correctly trims characters",
779 sdslen(x) == 4 && memcmp(x,"ciao\0",5) == 0)
780
781 y = sdsrange(sdsdup(x),1,1);
782 test_cond("sdsrange(...,1,1)",
783 sdslen(y) == 1 && memcmp(y,"i\0",2) == 0)
784
785 sdsfree(y);
786 y = sdsrange(sdsdup(x),1,-1);
787 test_cond("sdsrange(...,1,-1)",
788 sdslen(y) == 3 && memcmp(y,"iao\0",4) == 0)
789
790 sdsfree(y);
791 y = sdsrange(sdsdup(x),-2,-1);
792 test_cond("sdsrange(...,-2,-1)",
793 sdslen(y) == 2 && memcmp(y,"ao\0",3) == 0)
794
795 sdsfree(y);
796 y = sdsrange(sdsdup(x),2,1);
797 test_cond("sdsrange(...,2,1)",
798 sdslen(y) == 0 && memcmp(y,"\0",1) == 0)
799
800 sdsfree(y);
801 y = sdsrange(sdsdup(x),1,100);
802 test_cond("sdsrange(...,1,100)",
803 sdslen(y) == 3 && memcmp(y,"iao\0",4) == 0)
804
805 sdsfree(y);
806 y = sdsrange(sdsdup(x),100,100);
807 test_cond("sdsrange(...,100,100)",
808 sdslen(y) == 0 && memcmp(y,"\0",1) == 0)
809
810 sdsfree(y);
811 sdsfree(x);
812 x = sdsnew("foo");
813 y = sdsnew("foa");
814 test_cond("sdscmp(foo,foa)", sdscmp(x,y) > 0)
815
816 sdsfree(y);
817 sdsfree(x);
818 x = sdsnew("bar");
819 y = sdsnew("bar");
820 test_cond("sdscmp(bar,bar)", sdscmp(x,y) == 0)
821
822 sdsfree(y);
823 sdsfree(x);
824 x = sdsnew("aar");
825 y = sdsnew("bar");
826 test_cond("sdscmp(bar,bar)", sdscmp(x,y) < 0)
827
828 {
829 int oldfree;
830
831 sdsfree(x);
832 x = sdsnew("0");
833 sh = (void*) (x-(sizeof(struct sdshdr)));
834 test_cond("sdsnew() free/len buffers", sh->len == 1 && sh->free == 0);
835 x = sdsMakeRoomFor(x,1);
836 sh = (void*) (x-(sizeof(struct sdshdr)));
837 test_cond("sdsMakeRoomFor()", sh->len == 1 && sh->free > 0);
838 oldfree = sh->free;
839 x[1] = '1';
840 sdsIncrLen(x,1);
841 test_cond("sdsIncrLen() -- content", x[0] == '0' && x[1] == '1');
842 test_cond("sdsIncrLen() -- len", sh->len == 2);
843 test_cond("sdsIncrLen() -- free", sh->free == oldfree-1);
844 }
845 }
846 test_report()
847 return 0;
848 }
849 #endif
本文介绍了SDS动态字符串库的实现原理与核心函数。该库通过特殊的内部结构实现了高效字符串操作，如拼接、复制等，并具备内存预分配机制减少频繁内存分配开销。
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