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add STRPOP (#12) #13

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29a92b0
Add CHOP command to rxstrings
neomantra Dec 29, 2016
70fdc71
add CHOP to README.md and fast-path CHOP count == 0
neomantra Jan 6, 2017
5b07856
Fix CHOP when making the length 0
neomantra Jul 17, 2017
a9c79cb
Fix incorrect return values in PREPEND and CHOP.
neomantra Jul 17, 2017
0a650a5
add STRPOP (#12)
neomantra Jul 17, 2017
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21 changes: 21 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,18 @@ Note: the key shouldn't be repeated for the executed command.
**Reply:** Null if not equal or for non existing key when the `XX` flag is used.
On success, the reply depends on the actual command executed.

## `CHOP key count`

Removes characters from a value of a String key.

* If 'count' is positive, it removes from the right of the string;
* if 'count' is negative, it removes from the left of the string.
* If |count| is greater than the string length, the value is set as an empty string.
* If 'count' is zero, then the value remains unchanged.
* It is an error if the value is not a String.

**Reply:** Integer, the length of the string after the chop operation.

## `PREPEND key value`

> Time complexity: O(1). The amortized time complexity is O(1) assuming the prepended value is small and the already present value is of any size, since the dynamic string library used by Redis will double the free space available on every reallocation.
Expand Down Expand Up @@ -102,6 +114,15 @@ Credit: Meni Katz

**Reply:** Integer, the length of the String after it was modified.

## `STRPOP key`

Gets the value at `key`, deletes `key`, then returns the value.
It is equivalent to an atomic [GET](https://redis.io/commands/get) and [DEL](https://redis.io/commands/del).

* An error is returned if the key exists and does not hold a string.

**Reply:** String, the value at `key` or NULL if `key` didn't exist.

# rxhashes

This module provides extended Redis Hashes commands.
Expand Down
189 changes: 187 additions & 2 deletions src/rxstrings.c
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Expand Up @@ -135,6 +135,76 @@ int CheckAndCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
return REDISMODULE_OK;
}

/*
* CHOP key count
* Removes characters from a value of a String key.
* If 'count' is positive, it removes from the right of the string;
* if 'count' is negative, it removes from the left of the string.
* If |count| is greater than the string length, the value is set as an empty string.
* If 'count' is zero, then the value remains unchanged.
* It is an error if the value is not a String.
* Integer Reply: the length of the string after the chop operation.
*/
int ChopCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
if (argc != 3) {
return RedisModule_WrongArity(ctx);
}
RedisModule_AutoMemory(ctx);

/* Obtain key and extract offset argument. */
RedisModuleKey *key =
RedisModule_OpenKey(ctx, argv[1], REDISMODULE_READ | REDISMODULE_WRITE);
long long count;
if (RedisModule_StringToLongLong(argv[2], &count) != REDISMODULE_OK) {
RedisModule_ReplyWithError(ctx, "ERR invalid count");
return REDISMODULE_ERR;
}

/* Key must be a string. */
if (RedisModule_KeyType(key) != REDISMODULE_KEYTYPE_STRING) {
RedisModule_ReplyWithError(ctx, REDISMODULE_ERRORMSG_WRONGTYPE);
return REDISMODULE_ERR;
}

/* Calculate new length, protecting against overchop */
size_t valLen = RedisModule_ValueLength(key);
if (count == 0) {
RedisModule_ReplyWithLongLong(ctx, valLen);
return REDISMODULE_OK;
}
size_t absCount = (count < 0) ? -count : count;
size_t newLen = (valLen < absCount) ? 0 : (valLen - absCount);

/* Work around https://github.com/antirez/redis/issues/3717
* We use RM_StringSet to an empty string instead */
if (newLen == 0) {
RedisModuleString* emptyStr = RedisModule_CreateString(ctx, "", 0);
if (RedisModule_StringSet(key, emptyStr) != REDISMODULE_OK) {
RedisModule_ReplyWithError(ctx, "ERR RM_SetString empty failed");
return REDISMODULE_ERR;
}
RedisModule_ReplyWithLongLong(ctx, 0);
return REDISMODULE_OK;
}

/* If we chop from the left, we need to shift the characters,
* but only bother if we aren't zeroing the value */
if (count < 0 && newLen != 0) {
size_t dmaLen;
char* valPtr = RedisModule_StringDMA(key, &dmaLen, REDISMODULE_READ|REDISMODULE_WRITE);
memmove(valPtr, valPtr + absCount, newLen);
}

/* Truncate to new length */
if (RedisModule_StringTruncate(key, newLen) != REDISMODULE_OK) {
RedisModule_ReplyWithError(ctx, "ERR RM_StringTruncate failed");
return REDISMODULE_ERR;
}

RedisModule_ReplyWithLongLong(ctx, newLen);
return REDISMODULE_OK;
}

/*
* PREPEND key value
* Prepends a value to a String key.
Expand Down Expand Up @@ -167,7 +237,7 @@ int PrependCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
/* Otherwise key must be a string. */
if (RedisModule_KeyType(key) != REDISMODULE_KEYTYPE_STRING) {
RedisModule_ReplyWithError(ctx, REDISMODULE_ERRORMSG_WRONGTYPE);
return REDISMODULE_OK;
return REDISMODULE_ERR;
}

/* Prepend the string: 1) expand string, 2) shift oldVal via memmove, 3) prepend arg */
Expand Down Expand Up @@ -393,6 +463,49 @@ int SetRangeRandCommand(RedisModuleCtx *ctx, RedisModuleString **argv,
return REDISMODULE_OK;
}

/*
* STRPOP key
* Gets the value at key, deletes the key, then return the value.
* Equivalent to an atomic GET and DEL.
* An error is returned if there is a value stored that is not a string.
* String Reply: the value of key, or nil if key does not exist.
*/
int StrPopCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
if (argc != 2) {
return RedisModule_WrongArity(ctx);
}
RedisModule_AutoMemory(ctx);

/* Obtain key */
RedisModuleKey *key =
RedisModule_OpenKey(ctx, argv[1], REDISMODULE_READ | REDISMODULE_WRITE);

if (RedisModule_KeyType(key) == REDISMODULE_KEYTYPE_EMPTY) {
RedisModule_ReplyWithNull(ctx);
return REDISMODULE_OK;
}

/* Key must be a string */
if (RedisModule_KeyType(key) != REDISMODULE_KEYTYPE_STRING) {
RedisModule_ReplyWithError(ctx, REDISMODULE_ERRORMSG_WRONGTYPE);
return REDISMODULE_ERR;
}

/* GET the string */
size_t dmaLen;
char* valPtr = RedisModule_StringDMA(key, &dmaLen, REDISMODULE_READ);
RedisModuleString* valStr = RedisModule_CreateString(ctx, valPtr, dmaLen);

/* DELete the key */
if (RedisModule_DeleteKey(key) != REDISMODULE_OK) {
RedisModule_ReplyWithError(ctx, "ERR DeleteKey failed");
return REDISMODULE_ERR;
}

RedisModule_ReplyWithString(ctx, valStr);
return REDISMODULE_OK;
}

int testCheckAnd(RedisModuleCtx *ctx) {
RedisModuleCallReply *r;

Expand All @@ -409,6 +522,52 @@ int testCheckAnd(RedisModuleCtx *ctx) {
return 0;
}

int testChop(RedisModuleCtx *ctx) {
RedisModuleCallReply *r;

r = RedisModule_Call(ctx, "set", "cc", "foo", "abcde");
RMUtil_AssertReplyEquals(r,"OK");
r = RedisModule_Call(ctx, "chop", "cc", "foo", "-2");
RMUtil_Assert(RedisModule_CallReplyInteger(r) == 3);
r = RedisModule_Call(ctx, "get", "c", "foo");
RMUtil_AssertReplyEquals(r,"cde");
r = RedisModule_Call(ctx, "FLUSHALL", "");

r = RedisModule_Call(ctx, "set", "cc", "foo", "abcde");
RMUtil_AssertReplyEquals(r,"OK");
r = RedisModule_Call(ctx, "chop", "cc", "foo", "2");
RMUtil_Assert(RedisModule_CallReplyInteger(r) == 3);
r = RedisModule_Call(ctx, "get", "c", "foo");
RMUtil_AssertReplyEquals(r,"abc");
r = RedisModule_Call(ctx, "FLUSHALL", "");

r = RedisModule_Call(ctx, "set", "cc", "foo", "abcde");
RMUtil_AssertReplyEquals(r,"OK");
r = RedisModule_Call(ctx, "chop", "cc", "foo", "-10");
RMUtil_Assert(RedisModule_CallReplyInteger(r) == 0);
r = RedisModule_Call(ctx, "get", "c", "foo");
RMUtil_AssertReplyEquals(r,"");
r = RedisModule_Call(ctx, "FLUSHALL", "");

r = RedisModule_Call(ctx, "set", "cc", "foo", "abcde");
RMUtil_AssertReplyEquals(r,"OK");
r = RedisModule_Call(ctx, "chop", "cc", "foo", "10");
RMUtil_Assert(RedisModule_CallReplyInteger(r) == 0);
r = RedisModule_Call(ctx, "get", "c", "foo");
RMUtil_AssertReplyEquals(r,"");
r = RedisModule_Call(ctx, "FLUSHALL", "");

r = RedisModule_Call(ctx, "set", "cc", "foo", "abcde");
RMUtil_AssertReplyEquals(r,"OK");
r = RedisModule_Call(ctx, "chop", "cc", "foo", "0");
RMUtil_Assert(RedisModule_CallReplyInteger(r) == 5);
r = RedisModule_Call(ctx, "get", "c", "foo");
RMUtil_AssertReplyEquals(r,"abcde");
r = RedisModule_Call(ctx, "FLUSHALL", "");

return 0;
}

int testPrepend(RedisModuleCtx *ctx) {
RedisModuleCallReply *r;

Expand All @@ -433,6 +592,22 @@ int testSetRangeRand(RedisModuleCtx *ctx) {
return 0;
}

int testStrPop(RedisModuleCtx *ctx) {
RedisModuleCallReply *r;

r = RedisModule_Call(ctx, "set", "cc", "foo", "abcdef");
RMUtil_AssertReplyEquals(r,"OK");
r = RedisModule_Call(ctx, "strpop", "c", "foo");
RMUtil_AssertReplyEquals(r,"abcdef");
r = RedisModule_Call(ctx, "exists", "c", "foo");
RMUtil_Assert(RedisModule_CallReplyInteger(r) == 0);
r = RedisModule_Call(ctx, "strpop", "c", "bar");
RMUtil_Assert(RedisModule_CallReplyType(r) == REDISMODULE_REPLY_NULL);
r = RedisModule_Call(ctx, "FLUSHALL", "");

return 0;
}

int TestModule(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
RedisModule_AutoMemory(ctx);

Expand All @@ -445,8 +620,10 @@ int TestModule(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
}

RMUtil_Test(testCheckAnd);
RMUtil_Test(testChop);
RMUtil_Test(testPrepend);
RMUtil_Test(testSetRangeRand);
RMUtil_Test(testStrPop);

RedisModule_ReplyWithSimpleString(ctx, "PASS");
return REDISMODULE_OK;
Expand All @@ -460,6 +637,10 @@ int RedisModule_OnLoad(RedisModuleCtx *ctx) {
if (RedisModule_CreateCommand(ctx, "checkand", CheckAndCommand,
"write deny-oom", 1, 1, 1) == REDISMODULE_ERR)
return REDISMODULE_ERR;
if (RedisModule_CreateCommand(ctx, "chop", ChopCommand,
"write fast deny-oom", 1, 1,
1) == REDISMODULE_ERR)
return REDISMODULE_ERR;
if (RedisModule_CreateCommand(ctx, "prepend", PrependCommand,
"write fast deny-oom", 1, 1,
1) == REDISMODULE_ERR)
Expand All @@ -468,9 +649,13 @@ int RedisModule_OnLoad(RedisModuleCtx *ctx) {
"write fast deny-oom", 1, 1,
1) == REDISMODULE_ERR)
return REDISMODULE_ERR;
if (RedisModule_CreateCommand(ctx, "strpop", StrPopCommand,
"fast deny-oom", 1, 1,
1) == REDISMODULE_ERR)
return REDISMODULE_ERR;
if (RedisModule_CreateCommand(ctx, "rxstrings.test", TestModule, "write", 0,
0, 0) == REDISMODULE_ERR)
return REDISMODULE_ERR;

return REDISMODULE_OK;
}
}