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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 | 1x 1x 1x 1x 1x 4x 4x 4x 4x 4x | import { Logger } from "../../../logger";
import { IRequest } from "../../../server/request";
import { DataType } from "../../data/data-type";
import { Database } from "../../data/database";
import { DatabaseValue } from "../../data/database-value";
import { RedisToken } from "../../protocol/redis-token";
import { IRespCommand } from "../resp-command";
/**
* ### Available since 1.0.0.
*
* ### LTRIM key start stop
*
* Trim an existing list so that it will contain only the specified range of elements specified.
* Both start and stop are zero-based indexes, where 0 is the first element of the list (the
* head), 1 the next element and so on.
*
* For example: LTRIM foobar 0 2 will modify the list stored at foobar so that only the first
* three elements of the list will remain.
*
* start and end can also be negative numbers indicating offsets from the end of the list, where
* -1 is the last element of the list, -2 the penultimate element and so on.
*
* Out of range indexes will not produce an error: if start is larger than the end of the list,
* or start > end, the result will be an empty list (which causes key to be removed). If end is
* larger than the end of the list, Redis will treat it like the last element of the list.
*
* A common use of LTRIM is together with LPUSH / RPUSH. For example:
* ```
* LPUSH mylist someelement
* LTRIM mylist 0 99
* ```
*
* This pair of commands will push a new element on the list, while making sure that the list will
* not grow larger than 100 elements. This is very useful when using Redis to store logs for
* example. It is important to note that when used in this way LTRIM is an O(1) operation because
* in the average case just one element is removed from the tail of the list.
*
* ### Return value
* Simple string reply
*
* ### Examples
* ```
* redis> RPUSH mylist "one"
* (integer) 1
* redis> RPUSH mylist "two"
* (integer) 2
* redis> RPUSH mylist "three"
* (integer) 3
* redis> LTRIM mylist 1 -1
* "OK"
* redis> LRANGE mylist 0 -1
* 1) "two"
* 2) "three"
* redis>
* ```
*/
export class LTrimCommand extends IRespCommand {
public DbDataType = DataType.LIST
public maxParams = 3
public minParams = 3
public name = "ltrim"
private logger: Logger = new Logger(module.id);
public execSync(request: IRequest, db: Database): RedisToken {
this.logger.debug(
`${request.getCommand()}.execute(%s)`,
...request.getParams()
);
const key: string = request.getParam(0);
let startIndex: any = Number(request.getParam(1));
this.logger.debug(`startIndex is ${startIndex}`);
let stopIndex: any = Number(request.getParam(2));
this.logger.debug(`stopIndex is ${stopIndex}`);
if (isNaN(startIndex) || isNaN(stopIndex) || !Number.isInteger(startIndex) || !Number.isInteger(stopIndex)) {
this.logger.debug("Invalid start or stop index");
return RedisToken.error("ERR value is not an integer or out of range");
}
const list: DatabaseValue = db.get(key);
this.logger.debug(`Getting list "${key}"`);
if (!list) {
this.logger.debug(`LIST ${key} does not exist. Bailing`);
return RedisToken.responseOk();
}
this.logger.debug(
"The full list is [%s]",
...list.getList()
);
// Normalize start and stop indices
if (startIndex < 0) {
startIndex = list.getList().length + startIndex;
if (startIndex < 0) {
startIndex = 0;
}
}
if (stopIndex < 0) {
stopIndex = list.getList().length + stopIndex;
}
// Create a temporary array with slice
this.logger.debug(`startIndex is ${startIndex}, stopIndex = ${stopIndex + 1}`);
// Slice does not include the end element
const temparray: any[] = list.getList().slice(
startIndex,
stopIndex + 1
);
// Replace list with the slice
list.getList().splice(
0,
list.getList().length,
...temparray
);
if (list.getList().length > 0) {
this.logger.debug(
`Saving potentially modified list ${key}: %s`,
...list.getList()
);
db.put(
key,
list
);
} else {
this.logger.debug(`Removing empty list ${key}`);
db.remove(key);
}
return RedisToken.responseOk();
}
}
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