LCS -> STRALGO LCS.

STRALGO should be a container for mostly read-only string
algorithms in Redis. The algorithms should have two main
characteristics:

1. They should be non trivial to compute, and often not part of
programming language standard libraries.
2. They should be fast enough that it is a good idea to have optimized C
implementations.

Next thing I would love to see? A small strings compression algorithm.

src/server.c

@@ -1006,7 +1006,7 @@ struct redisCommand redisCommandTable[] = {
      "admin no-script no-slowlog ok-loading ok-stale",
      0,NULL,0,0,0,0,0,0},
 
-    {"lcs",lcsCommand,-4,
+    {"stralgo",stralgoCommand,-2,
      "write use-memory @string",
      0,lcsGetKeys,0,0,0,0,0,0}
 };

src/server.h

@@ -2389,7 +2389,7 @@ void xdelCommand(client *c);
 void xtrimCommand(client *c);
 void lolwutCommand(client *c);
 void aclCommand(client *c);
-void lcsCommand(client *c);
+void stralgoCommand(client *c);
 
 #if defined(__GNUC__)
 void *calloc(size_t count, size_t size) __attribute__ ((deprecated));

src/t_string.c

@@ -480,18 +480,31 @@ void strlenCommand(client *c) {
     addReplyLongLong(c,stringObjectLen(o));
 }
 
-/* LCS -- Longest common subsequence.
+
+/* STRALGO -- Implement complex algorithms on strings.
  *
- * LCS [IDX] [MINMATCHLEN <len>]
- *     STRINGS <string> <string> | KEYS <keya> <keyb> */
-void lcsCommand(client *c) {
+ * STRALGO <algorithm> ... arguments ... */
+void stralgoLCS(client *c);     /* This implements the LCS algorithm. */
+void stralgoCommand(client *c) {
+    /* Select the algorithm. */
+    if (!strcasecmp(c->argv[1]->ptr,"lcs")) {
+        stralgoLCS(c);
+    } else {
+        addReply(c,shared.syntaxerr);
+    }
+}
+
+/* STRALGO <algo> [IDX] [MINMATCHLEN <len>] [WITHMATCHLEN]
+ *     STRINGS <string> <string> | KEYS <keya> <keyb>
+ */
+void stralgoLCS(client *c) {
     uint32_t i, j;
     long long minmatchlen = 0;
     sds a = NULL, b = NULL;
     int getlen = 0, getidx = 0, withmatchlen = 0;
     robj *obja = NULL, *objb = NULL;
 
-    for (j = 1; j < (uint32_t)c->argc; j++) {
+    for (j = 2; j < (uint32_t)c->argc; j++) {
         char *opt = c->argv[j]->ptr;
         int moreargs = (c->argc-1) - j;
 

tests/unit/type/string.tcl

@@ -424,29 +424,29 @@ start_server {tags {"string"}} {
     set rna2 {ATTAAAGGTTTATACCTTCCCAGGTAACAAACCAACCAACTTTCGATCTCTTGTAGATCTGTTCTCTAAACGAACTTTAAAATCTGTGTGGCTGTCACTCGGCTGCATGCTTAGTGCACTCACGCAGTATAATTAATAACTAATTACTGTCGTTGACAGGACACGAGTAACTCGTCTATCTTCTGCAGGCTGCTTACGGTTTCGTCCGTGTTGCAGCCGATCATCAGCACATCTAGGTTT}
     set rnalcs {ACCTTCCCAGGTAACAAACCAACCAACTTTCGATCTCTTGTAGATCTGTTCTCTAAACGAACTTTAAAATCTGTGTGGCTGTCACTCGGCTGCATGCTTAGTGCACTCACGCAGTATAATTAATAACTAATTACTGTCGTTGACAGGACACGAGTAACTCGTCTATCTTCTGCAGGCTGCTTACGGTTTCGTCCGTGTTGCAGCCGATCATCAGCACATCTAGGTTT}
 
-    test {LCS string output with STRINGS option} {
-        r LCS STRINGS $rna1 $rna2
+    test {STRALGO LCS string output with STRINGS option} {
+        r STRALGO LCS STRINGS $rna1 $rna2
     } $rnalcs
 
-    test {LCS len} {
-        r LCS LEN STRINGS $rna1 $rna2
+    test {STRALGO LCS len} {
+        r STRALGO LCS LEN STRINGS $rna1 $rna2
     } [string length $rnalcs]
 
     test {LCS with KEYS option} {
         r set virus1 $rna1
         r set virus2 $rna2
-        r LCS KEYS virus1 virus2
+        r STRALGO LCS KEYS virus1 virus2
     } $rnalcs
 
     test {LCS indexes} {
-        dict get [r LCS IDX KEYS virus1 virus2] matches
+        dict get [r STRALGO LCS IDX KEYS virus1 virus2] matches
     } {{{238 238} {239 239}} {{236 236} {238 238}} {{229 230} {236 237}} {{224 224} {235 235}} {{1 222} {13 234}}}
 
     test {LCS indexes with match len} {
-        dict get [r LCS IDX KEYS virus1 virus2 WITHMATCHLEN] matches
+        dict get [r STRALGO LCS IDX KEYS virus1 virus2 WITHMATCHLEN] matches
     } {{{238 238} {239 239} 1} {{236 236} {238 238} 1} {{229 230} {236 237} 2} {{224 224} {235 235} 1} {{1 222} {13 234} 222}}
 
     test {LCS indexes with match len and minimum match len} {
-        dict get [r LCS IDX KEYS virus1 virus2 WITHMATCHLEN MINMATCHLEN 5] matches
+        dict get [r STRALGO LCS IDX KEYS virus1 virus2 WITHMATCHLEN MINMATCHLEN 5] matches
     } {{{1 222} {13 234} 222}}
 }