types

Here we list all functions from the auxiliary library in alphabetical order.

luaL_Buffer

typedef struct luaL_Buffer luaL_Buffer;

Type for a string buffer.

A string buffer allows C code to build Lua strings piecemeal. Its pattern of use is as follows:

• First declare a variable b of type luaL_Buffer.

• Then initialize it with a call luaL_buffinit(L, &b).

• Then add string pieces to the buffer calling any of the luaL_add* functions.

• Finish by calling luaL_pushresult(&b). This call leaves the final string on the top of the stack.

If you know beforehand the maximum size of the resulting string, you can use the buffer like this:

• First declare a variable b of type luaL_Buffer.

• Then initialize it and preallocate a space of size sz with a call luaL_buffinitsize(L, &b, sz).

• Then produce the string into that space.

• Finish by calling luaL_pushresultsize(&b, sz), where sz is the total size of the resulting string copied into that space (which may be less than or equal to the preallocated size).

During its normal operation, a string buffer uses a variable number of stack slots. So, while using a buffer, you cannot assume that you know where the top of the stack is. You can use the stack between successive calls to buffer operations as long as that use is balanced; that is, when you call a buffer operation, the stack is at the same level it was immediately after the previous buffer operation. (The only exception to this rule is luaL_addvalue.) After calling luaL_pushresult, the stack is back to its level when the buffer was initialized, plus the final string on its top.

luaL_Reg

typedef struct luaL_Reg {
  const char *name;
  lua_CFunction func;
} luaL_Reg;

Type for arrays of functions to be registered by luaL_setfuncs. name is the function name and func is a pointer to the function. Any array of luaL_Reg must end with a sentinel entry in which both name and func are NULL.

luaL_Stream

typedef struct luaL_Stream {
  FILE *f;
  lua_CFunction closef;
} luaL_Stream;

The standard representation for file handles used by the standard I/O library.

A file handle is implemented as a full userdata, with a metatable called LUA_FILEHANDLE (where LUA_FILEHANDLE is a macro with the actual metatable's name). The metatable is created by the I/O library (see luaL_newmetatable).

This userdata must start with the structure luaL_Stream; it can contain other data after this initial structure. The field f points to the corresponding C stream (or it can be NULL to indicate an incompletely created handle). The field closef points to a Lua function that will be called to close the stream when the handle is closed or collected; this function receives the file handle as its sole argument and must return either a true value, in case of success, or a false value plus an error message, in case of error. Once Lua calls this field, it changes the field value to NULL to signal that the handle is closed.