Buffers

In Luau, buffers are arbitrary chunks of memory. Luau can interact with these values through the buffer library.

Buffers are useful when Luau needs to interact with raw data. Buffers cannot be resized, but they can be modified.

// Allow Luau to fetch the binary contents of a file:
int read_file(lua_State* L) {
    const char* filepath = luaL_checkstring(L, 1);
    std::ifstream file(filepath, std::ios::binary);
    if (!file.is_open()) {
        luaL_error("failed to open file: %s", filepath);
    }

    std::string data;
    std::string line;
    while (std::getline(file, line)) {
        data += line;
    }

    // Create Luau buffer:
    void* buf = lua_newbuffer(L, data.size());

    // Write to buffer:
    memcpy(buf, data.data(), data.size());

    return 1;
}

// Expose to Luau:
lua_pushcfunction(L, read_file, "read_file");
lua_setglobal(L, "read_file");

Now we can read a file from Luau:

local filepath = "some/path/whatever.jpg"
local buf = read_file(filepath)
print(`size of {filepath}: {buffer.len(buf)}`)