Affix
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```perl
# Find the address of the library's custom free function
my $free_func = find_symbol($my_lib, 'custom_free');
# When $ptr goes out of scope, Affix will call custom_free($ptr)
attach_destructor($ptr, $free_func, $my_lib);
```
## Type Casting
### `cast( $ptr, $type )`
Reinterprets a memory address as a new type. The behavior depends on the requested `$type`:
- **Casting to a Value (Primitives/Strings):** Reads the memory immediately and returns a Perl scalar copy.
- **Casting to a Reference (Pointers/Live Views):** Returns a **new unmanaged Pin** that aliases the same memory address, allowing you to interact with it using the new type's rules.
```perl
my $void_ptr = malloc(4);
# 1. Alias the memory as an Integer pointer
my $int_ptr = cast($void_ptr, Pointer[Int]);
$int_ptr->[0] = 99;
# 2. Read the memory immediately as an integer value
my $val = cast($void_ptr, Int); # Returns 99
```
# POINTER UTILITIES
### `address( $ptr )`
Returns the virtual memory address of the pointer as a Perl Unsigned Integer (`UInt64`). Useful for passing addresses
to other FFI libraries or debugging.
```
say sprintf("Address: 0x%X", address($ptr));
```
### `ptr_add( $ptr, $offset_bytes )`
Returns a new **unmanaged alias Pin** offset by `$offset_bytes`.
```perl
my $int_arr = calloc(10, Int);
my $next_elem = ptr_add($int_arr, sizeof(Int));
```
_Note: If `$ptr` is an Array type, `ptr_add` correctly decays the returned pin into a Pointer to the element type._
### `ptr_diff( $ptr1, $ptr2 )`
Returns the byte difference (`$ptr1 - $ptr2`) between two pointers as an integer.
### `is_null( $ptr )`
Returns true if the address is `NULL` (`0x0`).
### `strnlen( $ptr, $max )`
Safe string length calculation. Checks the pointer for a `NULL` terminator, scanning at most `$max` bytes.
# RAW MEMORY OPERATIONS
Affix exposes standard C memory operations for high-performance, raw byte manipulation. These functions accept either
Pins or raw integer addresses.
- `memcpy( $dest, $src, $bytes )`: Copies exactly `$bytes` from `$src` to `$dest`.
- `memmove( $dest, $src, $bytes )`: Copies `$bytes` from `$src` to `$dest`. Safe to use if the memory regions overlap.
- `memset( $ptr, $byte_val, $bytes )`: Fills the first `$bytes` of the memory block with the value `$byte_val`.
- `memcmp( $ptr1, $ptr2, $bytes )`: Compares the first `$bytes` of two memory blocks. Returns an integer less than, equal to, or greater than zero.
- `memchr( $ptr, $byte_val, $bytes )`: Locates the first occurrence of `$byte_val` within the first `$bytes` of the memory block. Returns a new Pin pointing to the match, or `undef`.
# LIBRARIES & SYMBOLS
Loading dynamic libraries across different operating systems (Windows, macOS, Linux, BSD) can be a nightmare of varying
extensions, prefixes, and search paths. Affix abstracts this complexity away with a smart library discovery engine.
## Library Discovery
When you provide a bare library name (e.g., `'z'`, `'ssl'`, `'user32'`) rather than an absolute path, Affix
automatically formats the name for the current platform (e.g., `libz.so`, `libz.dylib`, `z.dll`) and searches the
following locations in order:
- 1. **Standard System Paths:** Windows `System32`/`SysWOW64`; Unix `/usr/local/lib`, `/usr/lib`, `/lib`, `/usr/lib/system`.
- 2. **Environment Variables:** Paths defined in `LD_LIBRARY_PATH`, `DYLD_LIBRARY_PATH`, `DYLD_FALLBACK_LIBRARY_PATH`, or `PATH`.
- 3. **Local Paths:** The current working directory (`.`) and its `lib/` subdirectory.
## Functions
### `load_library( $path_or_name )`
Locates and loads a dynamic library into memory, returning an opaque `Affix::Lib` handle.
```perl
my $lib = load_library('sqlite3');
```
**Lifecycle:** Library handles are thread-safe and internally reference-counted. The underlying OS library is only
closed (e.g., via `dlclose` or `FreeLibrary`) when all Affix wrappers and pins relying on it are destroyed.
_Note:_ When using `affix()` or `wrap()`, you can safely pass the string name directly (e.g., `affix('sqlite3',
...)`) and Affix will call `load_library` for you internally. If you pass `undef` instead of a library name, Affix
will search the currently running executable process.
### `locate_lib( $name, [$version] )`
Searches for a library using Affix's discovery engine and returns its absolute file path as a string. It **does not**
load the library into memory. This is useful if you need to pass the library path to another tool or check for its
existence.
```perl
# Find libssl.so.1.1 or libssl.1.1.dylib
my $path = locate_lib('ssl', '1.1');
say "Found SSL at: $path" if $path;
```
### `find_symbol( $lib_handle, $symbol_name )`
Looks up an exported symbol (function or global variable) inside an already-loaded `Affix::Lib` handle. Returns an
unmanaged `Affix::Pointer` (Pin) of type `Pointer[Void]` pointing to the memory address of the symbol.
typedef Rect => Struct[ x => Int, y => Int, w => Int, h => Int ];
# C: offsetof(Rect, w);
say offsetof( Rect(), 'w' ); # 8 (skips x and y, 4 bytes each)
```
### `types()`
Returns a list of all custom type names currently registered in Affix's global type registry via `typedef`. In scalar
context, returns the total number of registered types.
```perl
my @known_types = types();
say "Registered types: " . join(', ', @known_types);
```
# INTERFACING WITH OTHER LANGUAGES
Because Affix dynamically loads symbols according to the C Application Binary Interface (C ABI), it can interact with
libraries written in almost any language, provided they expose their functions correctly. Companion modules like
[Affix::Build](https://metacpan.org/pod/Affix%3A%3ABuild) make compiling these languages seamless.
Here are the requirements and quirks for interfacing with non-C languages.
## C++
C++ uses "name mangling" to support function overloading and namespaces, which alters the final symbol name inside the
compiled library.
- 1. **Prevent Mangling:** Wrap your exported functions in `extern "C"` to ensure they have predictable names.
```
extern "C" {
int add(int a, int b) { return a + b; }
}
```
- 2. **Or Use Mangled Names:** If you cannot change the C++ source, you must look up the exact mangled name (e.g., `_Z3addii`) using tools like `nm` or `objdump`, and bind to that.
- 3. **Object Methods:** Calling an object's method requires passing the object instance pointer (the `this` pointer) as the first argument. Use the `ThisCall( ... )` wrapper around your callback/signature to automatically insert `Pointer[Void]` at t...
## Rust
Rust does not use the C ABI by default. You must explicitly instruct the compiler to format the function correctly.
- 1. **Exporting:** Use `#[no_mangle]` and `pub extern "C"`.
```rust
#[no_mangle]
pub extern "C" fn add(a: i32, b: i32) -> i32 { a + b }
```
- 2. **Structs:** Rust structs must be annotated with `#[repr(C)]` to guarantee their memory layout matches C (and thus Affix's `Struct`).
- 3. **Strings:** Rust strings are not null-terminated. You must receive `String` arguments as `*const std::os::raw::c_char` and convert them using `CStr::from_ptr`.
## Fortran
Fortran relies heavily on pass-by-reference.
- 1. **Pointers Everywhere:** Unless a parameter uses the modern Fortran `VALUE` attribute, you must pass everything as a pointer. If the function expects a Float, your Affix signature must be `Pointer[Float]`.
- 2. **Name Mangling:** Most Fortran compilers convert subroutine names to lowercase and append an underscore. A Fortran subroutine named `CALC_STRESS` will likely be exported as `calc_stress_`.
- 3. **Strings:** Fortran does not use null-terminated strings. When passing character arrays, Fortran compilers silently append hidden "length" parameters at the **end** of the argument list (passed by value as integers).
## Assembly
When writing raw Assembly (NASM/GAS), you must manually adhere to the calling convention of your target platform:
- **Linux/macOS (System V AMD64 ABI):** Arguments are passed in `rdi, rsi, rdx, rcx, r8, r9`, with the rest on the stack.
- **Windows (Microsoft x64):** Arguments are passed in `rcx, rdx, r8, r9`, with "shadow space" reserved on the stack.
## Go
Go libraries can be loaded if they are compiled with `-buildmode=c-shared`. Note that Go slices and strings contain
internal metadata (length/capacity) and do not map directly to C arrays or `char*`. Use the `C` package inside Go
(`import "C"`) and `*C.char` to bridge the boundary.
# ERROR HANDLING & DEBUGGING
Bridging two entirely different runtimes can lead to spectacular crashes if types or memory boundaries are mismatched.
Affix provides built-in tools to help you identify what went wrong.
## Error Handling
### `errno()`
Accesses the system error code from the most recent FFI or standard library call (reads `errno` on Unix and
`GetLastError` on Windows).
This function returns a **dualvar**. It behaves as an integer in numeric context, and magically resolves to the
human-readable system error message (via `strerror` or `FormatMessage`) in string context.
```perl
# Suppose a C file-open function fails
my $fd = c_open("/does/not/exist");
if (!$fd) {
my $err = errno();
# String context
say "Failed to open: $err"; # "No such file or directory"
# Numeric context
if (int($err) == 2) {
say "Code 2 specifically triggered.";
}
}
```
**Note:** You must call `errno()` immediately after the C function invokes, as subsequent Perl operations (like
printing to STDOUT) might overwrite the system's error register.
## Memory Inspection
### `dump( $pin, $length_in_bytes )`
Prints a formatted hex dump of the memory pointed to by a Pin directly to `STDOUT`. This is an invaluable tool for
verifying that C structs or buffers contain the data you expect.
```perl
my $ptr = strdup("Affix Debugging");
dump($ptr, 16);
# Output:
# Dumping 16 bytes from 0x55E9A8A5 at script.pl line 42
# 000 41 66 66 69 78 20 44 65 62 75 67 67 69 6e 67 00 | Affix Debugging.
```
### `sv_dump( $scalar )`
Dumps Perl's internal interpreter structure (SV) for a given scalar to `STDOUT`. This exposes the raw flags, reference
counts, and memory layout of the Perl variable itself.
```perl
my $val = 42;
sv_dump($val);
# Exposes IV flags, memory addresses of the SV head, etc.
```
## Advanced Debugging
### `set_destruct_level( $level )`
Sets the internal `PL_perl_destruct_level` variable.
When testing XS/FFI code for memory leaks using tools like Valgrind or AddressSanitizer, you often want Perl to
meticulously clean up all global memory during its destruction phase (otherwise the leak checker will be flooded with
false-positive "leaks" that are actually just memory Perl intentionally leaves to the OS to reclaim).
```
# Call this at the start of your script when running under Valgrind
set_destruct_level(2);
```
# COMPANION MODULES
Affix ships with two powerful companion modules to streamline your FFI development:
- [**Affix::Wrap**](https://metacpan.org/pod/Affix%3A%3AWrap): Parses C/C++ headers using the Clang AST to automatically generate Affix bindings for entire libraries.
- [**Affix::Build**](https://metacpan.org/pod/Affix%3A%3ABuild): A polyglot builder that compiles inline C, C++, Rust, Zig, Go, and 15+ other languages into dynamic libraries you can bind instantly.
# THREAD SAFETY & CONCURRENCY
Affix bridges Perl (a single-threaded interpreter, generally) with libraries that may be multi-threaded. This creates
potential hazards that you must manage.
## 1. Initialization Phase vs. Execution Phase
Functions that modify Affix's global state are **not thread-safe**. You must perform all definitions in the main thread
before starting any background threads or loops in the library.
Unsafe operations that you should never call from Callbacks or in a threaded context:
- `affix( ... )` - Binding new functions.
- `typedef( ... )` - Registering new types.
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