jhseodev · March 11, 2021 23:57 · Mar 11, 2021 · Dec 20, 2015
diff --git a/luaF.c b/luaF.c
@@ -6,6 +6,20 @@
 // a table construct
 //
 // this avoids extra memory bloat and will keep the resulting strings on the stack
+//
+// Build:
+//   gcc -shared -fpic -O -I/usr/include/luajit-2.0 luaF.c -o luaF.so
+//
+// Test Script:
+//   local split_test = require("luaF_split")
+//   local first, second = split("hello; world", ";")
+//
+// Run:
+//   luajit test_script.lua
+
+#include <string.h>
+#include <lua.h>
+
 static int luaF_split(lua_State* state) {
     if (lua_isstring(state, 1) && lua_isstring(state, 2)) {
         size_t len, dlen;
@@ -24,11 +38,11 @@ static int luaF_split(lua_State* state) {
                 else d = 0;
             }
             if (d == dlen) { // delimeter matched section
-                size_t slen = (i - dlen) - t; // length of section
+                size_t slen = i - t; // length of section
                 if (slen) {
                     char section[slen];
-                    strncpy(&section, str + t, slen);
-                    lua_pushlstring(state, &section, slen);
+                    strncpy(section, str + t, slen);
+                    lua_pushlstring(state, section, slen);
                 }
                 else {
                     char empty = '\0';
@@ -41,8 +55,8 @@ static int luaF_split(lua_State* state) {
         if (t < len) { // if the 't' cursor isn't at the end of string, create one more section
             size_t slen = len - t; // length of section
             char section[slen];
-            strncpy(&section, str + t, slen);
-            lua_pushlstring(state, &section, slen);
+            strncpy(section, str + t, slen);
+            lua_pushlstring(state, section, slen);
             section_amt++;
         }
         return section_amt;
@@ -70,4 +84,10 @@ static int luaF_fsplit(lua_State* state) {
     }
     else luaL_error(state, "excepted `function` final argument");
     return 0;
-}
+}
+
+int luaopen_split(lua_State *L)
+{
+    lua_register(L, "luaF_split", luaF_split);
+    return 0;
+}
diff --git a/luaF.c b/luaF.c
@@ -0,0 +1,73 @@
+// Faster split method, the only alternative within lua is using gsub, which
+// is insanely slower. This function will actually return strings on the stack,
+// so {str:split(d)} can be used to collect the return values in a table
+//
+// A more memory effecient use would be to use string.fsplit rather than using
+// a table construct
+//
+// this avoids extra memory bloat and will keep the resulting strings on the stack
+static int luaF_split(lua_State* state) {
+    if (lua_isstring(state, 1) && lua_isstring(state, 2)) {
+        size_t len, dlen;
+        char* str = lua_tolstring(state, 1, &len);
+        char* dstr = lua_tolstring(state, 2, &dlen);
+        if (!str || !dstr) return 0;
+        size_t i, t = 0, d = 0; // parse index, last found section index, and delimeter index, respectively
+        size_t section_amt = 0;
+        for (i = 0; i < len; i++) {
+            if (str[i] == dstr[d]) { // match characters, advance 'd' if a character matches
+                d++;
+            }
+            else { // if a comparison failed, reset 'd' idx
+                if (str[i] == *dstr) // if the failed character matches the first delimeter char, set d = 1
+                    d = 1;
+                else d = 0;
+            }
+            if (d == dlen) { // delimeter matched section
+                size_t slen = (i - dlen) - t; // length of section
+                if (slen) {
+                    char section[slen];
+                    strncpy(&section, str + t, slen);
+                    lua_pushlstring(state, &section, slen);
+                }
+                else {
+                    char empty = '\0';
+                    lua_pushlstring(state, &empty, 0);
+                }
+                section_amt++;
+                t = i + 1; // move 't' to after the matched delimeter
+            }
+        }
+        if (t < len) { // if the 't' cursor isn't at the end of string, create one more section
+            size_t slen = len - t; // length of section
+            char section[slen];
+            strncpy(&section, str + t, slen);
+            lua_pushlstring(state, &section, slen);
+            section_amt++;
+        }
+        return section_amt;
+    }
+    else luaL_error(state, "excepted `string` arguments");
+    return 0;
+}
+
+// Splits a string, using a delimeter, and calls a function for each delimeter.
+// This function can be used to iterate on a split string without ever creating
+// table garbage
+static int luaF_fsplit(lua_State* state) {
+    if (lua_isfunction(state, 3)) {
+        // remove string and delimeter
+        lua_remove(state, 1);
+        lua_remove(state, 1);
+        // call split function using the current stack
+        luaB_split(state);
+        // loop on every string result
+        while (lua_gettop(state) != 1) {
+            lua_pushvalue(state, 1);
+            luaB_swap(state, -1, -2);
+            lua_call(state, 1, 0);
+        }
+    }
+    else luaL_error(state, "excepted `function` final argument");
+    return 0;
+}
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