gistfile2.lua

package = "stringext"
version = "0.2-1"
source = {
   url = "http://bpbio.googlecode.com/files/stringext-0.2.tar.gz"
}
description = {
   summary = "C extension for string.split, string.strip",
   detailed = [[
    Implementation of string.split and string.strip in the
    lua c-api as borrowed from the wiki and book.
    This was implemented as a learning exercise. Additions
    are welcome if the library is kept simple. Usage is:

    > require "stringext" -- adds to string methods
    > astr = " asdf "
    > = astr:strip()
    asdf

    -- split() returns a table/array.
    > bstr = "aXbXc"
    > table.concat(bstr.split("X"), "|")
    a|b|c

   ]],
   homepage = "http://hackmap.blogspot.com",
   license = "MIT/X11"
}
dependencies = {
   "lua >= 5.1"
}
build = {
    type = "builtin",
    modules = {
       stringext = "stringext.c"
    }
}

Makefile

LUA_CFLAGS=`pkg-config lua5.1 --cflags`

all: stringext.so

stringext.so: stringext.c
    gcc $(LUA_CFLAGS) -O3 -fPIC -o stringext.o -c stringext.c
    gcc -shared -O3 stringext.o -o stringext.so

stringext.c

#define LUA_LIB
#include <lua.h>
#include <lauxlib.h>
#include <stdio.h>
#include <string.h>
#include <stddef.h>
#include <ctype.h>

static int split(lua_State *L) {
    const char *string = luaL_checkstring(L, 1);
    const char *sep = luaL_checkstring(L, 2);
    const char *token;
    int i = 1;
    lua_newtable(L);
    while ((token = strchr(string, *sep)) != NULL) {
        lua_pushlstring(L, string, token - string);
        lua_rawseti(L, -2, i++);
        string = token + 1;
    }
    lua_pushstring(L, string);
    lua_rawseti(L, -2, i);
    return 1;
}

// http://lua-users.org/wiki/StringTrim
int strip(lua_State *L) {
    const char *front;
    const char *end;
    size_t      size;

    front = luaL_checklstring(L, 1, &size);
    end   = &front[size - 1];
    
    for ( ; size && isspace(*front) ; size-- , front++)
    ;
    for ( ; size && isspace(*end) ; size-- , end--)
    ;
    
    lua_pushlstring(L, front, (size_t)(end - front) + 1);
    return 1;
}   
    
static const luaL_reg stringext[] = {
    {"split", split},
    {"strip", strip},
    {NULL, NULL}
};
    
int luaopen_stringext(lua_State *L){
    luaL_openlib(L, "string", stringext, 0);
    return 1;
}

stringext_test.lua

require "stringext"
b = ("asdfsk"):split("s")
assert(#b == 3, #b)

print(table.concat(string.split("a\tb\tc", "\t"), "|"))
assert(("asdf"):split("s")[1] == "a")

print(table.concat(string.split("aXXbXXc", "XX"), "|"))


assert(string.strip(" asdf ") == "asdf")
assert(string.strip("asdf ") == "asdf")
assert(string.strip(" asdf  ") == "asdf")
assert(string.strip("asdf") == "asdf")
assert(("asdf"):strip() == "asdf")
assert(("\nasdf\r\n"):strip() == "asdf")