Making a modifiable copy of a string in C
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- Subject: Making a modifiable copy of a string in C
- From: Marc Balmer <marc@...>
- Date: Sun, 7 Apr 2019 12:53:40 +0200
(sorry if I spam the list a bit with my questions)
My goal: Create a modifiable copy of a string in a C module, so that the copy of the string can be used with the strtok_r() function (which modifies the string passed as first argument).
So far I came up with two different ways:
First variant:
const char *s;
char *u;
s = luaL_checklstring(L, 2, &len);
u = lua_newuserdata(L, len);
memcpy(u, s, len);
Here I use 'u' as the first argument to the strtok_r() call.
Second variant:
char *s;
s = (char *)lua_pushfstring(L, "%s,", luaL_checkstring(L, 2));
Not that I add a command in the format string, to make the strings not similar, which apparently causes Lua to create a new string and not reuse the original string data. The comma is part of the delimiter argument to strtok_r(), so it does not affect my code.
Are both variants valid?
fwiw, I am using strtok_r to tokenize a a string passed to a function, and then use luaL_checkoption() to get the individual values for each token, or'ing them together to a flag value. The following C code
p = dlopen('whatever', RTLD_LAZY | RTLD_GLOBAL)
becomes the following Lua code
local p = dlopen('whatever', 'lazy, global')