# FFI Helper APIs

The helper APIs are the low-level tools you use when a binding needs explicit memory management, pointer inspection, or typed reads and writes.

## Allocation and Ownership

The owned-memory helpers are `tcc_malloc()` and `tcc_cstring()`.

    buf <- tcc_malloc(16)
    str_ptr <- tcc_cstring("hello")

    tcc_ptr_is_owned(buf)
    #> [1] TRUE
    tcc_ptr_is_owned(str_ptr)
    #> [1] TRUE

Both return owned external pointers. They can be freed explicitly with `tcc_free()` and also carry finalizers.

    tcc_free(buf)
    #> NULL
    tcc_free(str_ptr)
    #> NULL

## Reading and Writing Raw Bytes

    buf <- tcc_malloc(8)
    tcc_write_bytes(buf, as.raw(1:8))
    #> NULL
    tcc_read_bytes(buf, 8)
    #> [1] 01 02 03 04 05 06 07 08
    tcc_free(buf)
    #> NULL

## Typed Reads and Writes

The helper layer also exposes typed accessors for primitive values at byte offsets.

    buf <- tcc_malloc(16)
    tcc_write_i32(buf, 0L, 42L)
    tcc_write_f64(buf, 8L, 3.5)

    tcc_read_i32(buf, offset = 0L)
    #> [1] 42
    tcc_read_f64(buf, offset = 8L)
    #> [1] 3.5

    tcc_free(buf)
    #> NULL

These helpers are useful for manual struct-like layouts, output buffers, or pointer-heavy APIs that do not map cleanly onto ordinary R vectors.

## Pointer-to-Pointer Helpers

Some C APIs fill outputs through `T **` or `void **`. `Rtinycc` exposes a small set of helpers for that pattern.

    ptr_size <- if (!is.null(.Machine$sizeof.pointer)) .Machine$sizeof.pointer else 8L
    ptr_ref <- tcc_malloc(ptr_size)
    target <- tcc_malloc(4)

    tcc_ptr_set(ptr_ref, target)
    #> <pointer: 0x5d19d1409f60>
    tcc_ptr_addr(tcc_data_ptr(ptr_ref))
    #> [1] "102365452478320"
    tcc_ptr_addr(target)
    #> [1] "102365452478320"

    tcc_ptr_set(ptr_ref, tcc_null_ptr())
    #> <pointer: 0x5d19d1409f60>
    tcc_ptr_is_null(tcc_data_ptr(ptr_ref))
    #> [1] TRUE

    tcc_free(target)
    #> NULL
    tcc_free(ptr_ref)
    #> NULL

`tcc_data_ptr()` returns a borrowed pointer view. It is not an owned allocation.

## C String Helpers

    str_ptr <- tcc_cstring("Hello, world")
    tcc_read_cstring(str_ptr)
    #> [1] "Hello, world"
    tcc_read_cstring(str_ptr, max_bytes = 5)
    #> [1] "Hello"
    tcc_free(str_ptr)
    #> NULL

This helper is the safe way to allocate a C-owned NUL-terminated string when the callee expects a mutable or longer-lived `char *`.