1 /* Hellodict -- An example of modules dictionary API
2  *
3  * This module implements a volatile key-value store on top of the
4  * dictionary exported by the Redis modules API.
5  *
6  * -----------------------------------------------------------------------------
7  *
8  * Copyright (c) 2018, Salvatore Sanfilippo <antirez at gmail dot com>
9  * All rights reserved.
10  *
11  * Redistribution and use in source and binary forms, with or without
12  * modification, are permitted provided that the following conditions are met:
13  *
14  *   * Redistributions of source code must retain the above copyright notice,
15  *     this list of conditions and the following disclaimer.
16  *   * Redistributions in binary form must reproduce the above copyright
17  *     notice, this list of conditions and the following disclaimer in the
18  *     documentation and/or other materials provided with the distribution.
19  *   * Neither the name of Redis nor the names of its contributors may be used
20  *     to endorse or promote products derived from this software without
21  *     specific prior written permission.
22  *
23  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
24  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
27  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
28  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
29  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
30  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
31  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
32  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
33  * POSSIBILITY OF SUCH DAMAGE.
34  */
35 
36 #define REDISMODULE_EXPERIMENTAL_API
37 #include "../redismodule.h"
38 #include <stdio.h>
39 #include <stdlib.h>
40 #include <ctype.h>
41 #include <string.h>
42 
43 static RedisModuleDict *Keyspace;
44 
45 /* HELLODICT.SET <key> <value>
46  *
47  * Set the specified key to the specified value. */
48 int cmd_SET(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
49     if (argc != 3) return RedisModule_WrongArity(ctx);
50     RedisModule_DictSet(Keyspace,argv[1],argv[2]);
51     /* We need to keep a reference to the value stored at the key, otherwise
52      * it would be freed when this callback returns. */
53     RedisModule_RetainString(NULL,argv[2]);
54     return RedisModule_ReplyWithSimpleString(ctx, "OK");
55 }
56 
57 /* HELLODICT.GET <key>
58  *
59  * Return the value of the specified key, or a null reply if the key
60  * is not defined. */
61 int cmd_GET(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
62     if (argc != 2) return RedisModule_WrongArity(ctx);
63     RedisModuleString *val = RedisModule_DictGet(Keyspace,argv[1],NULL);
64     if (val == NULL) {
65         return RedisModule_ReplyWithNull(ctx);
66     } else {
67         return RedisModule_ReplyWithString(ctx, val);
68     }
69 }
70 
71 /* HELLODICT.KEYRANGE <startkey> <endkey> <count>
72  *
73  * Return a list of matching keys, lexicographically between startkey
74  * and endkey. No more than 'count' items are emitted. */
75 int cmd_KEYRANGE(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
76     if (argc != 4) return RedisModule_WrongArity(ctx);
77 
78     /* Parse the count argument. */
79     long long count;
80     if (RedisModule_StringToLongLong(argv[3],&count) != REDISMODULE_OK) {
81         return RedisModule_ReplyWithError(ctx,"ERR invalid count");
82     }
83 
84     /* Seek the iterator. */
85     RedisModuleDictIter *iter = RedisModule_DictIteratorStart(
86         Keyspace, ">=", argv[1]);
87 
88     /* Reply with the matching items. */
89     char *key;
90     size_t keylen;
91     long long replylen = 0; /* Keep track of the amitted array len. */
92     RedisModule_ReplyWithArray(ctx,REDISMODULE_POSTPONED_ARRAY_LEN);
93     while((key = RedisModule_DictNextC(iter,&keylen,NULL)) != NULL) {
94         if (replylen >= count) break;
95         if (RedisModule_DictCompare(iter,"<=",argv[2]) == REDISMODULE_ERR)
96             break;
97         RedisModule_ReplyWithStringBuffer(ctx,key,keylen);
98         replylen++;
99     }
100     RedisModule_ReplySetArrayLength(ctx,replylen);
101 
102     /* Cleanup. */
103     RedisModule_DictIteratorStop(iter);
104     return REDISMODULE_OK;
105 }
106 
107 /* This function must be present on each Redis module. It is used in order to
108  * register the commands into the Redis server. */
109 int RedisModule_OnLoad(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
110     REDISMODULE_NOT_USED(argv);
111     REDISMODULE_NOT_USED(argc);
112 
113     if (RedisModule_Init(ctx,"hellodict",1,REDISMODULE_APIVER_1)
114         == REDISMODULE_ERR) return REDISMODULE_ERR;
115 
116     if (RedisModule_CreateCommand(ctx,"hellodict.set",
117         cmd_SET,"write deny-oom",1,1,0) == REDISMODULE_ERR)
118         return REDISMODULE_ERR;
119 
120     if (RedisModule_CreateCommand(ctx,"hellodict.get",
121         cmd_GET,"readonly",1,1,0) == REDISMODULE_ERR)
122         return REDISMODULE_ERR;
123 
124     if (RedisModule_CreateCommand(ctx,"hellodict.keyrange",
125         cmd_KEYRANGE,"readonly",1,1,0) == REDISMODULE_ERR)
126         return REDISMODULE_ERR;
127 
128     /* Create our global dictionray. Here we'll set our keys and values. */
129     Keyspace = RedisModule_CreateDict(NULL);
130 
131     return REDISMODULE_OK;
132 }
133