/* * SharedBuffer — JS-visible wrapper around a memfd-backed mmap region. * * Lifecycle * ───────── * Two construction paths: * * 1. `SharedBuffer.create(size)` — allocates a fresh memfd, ftruncates to * @size, and mmaps MAP_SHARED. The region owns the fd; it is closed * and the mapping freed when the SharedBuffer instance is collected. * * 2. `SharedBuffer.from_fd(fd, size)` — mmaps a fd received from another * process (typically via SCM_RIGHTS in @gjsify/worker_threads). The * original fd is dup'd, so the caller can close their copy safely. * * Wire protocol * ───────────── * All multi-byte accessors are explicitly LE on the wire (little-endian), * so a SharedBuffer written on x86_64 and read on s390x sees the same * values. The C shim handles byte-swapping where needed. * * Atomics * ─────── * `atomic_*_i32` family operates with SEQ_CST memory ordering via GCC * `__atomic_*` builtins. `futex_wait` / `futex_wake` give cross-process * wait/notify via Linux SYS_futex (FUTEX_*_PRIVATE flavour). * * Buffer ownership: read_bytes returns a GLib.Bytes that borrows the * mmap'd memory (no copy) and ref-counts the region so the mapping * survives until every outstanding bytes reference is released. */ namespace GjsifySabNative { /* ── Opaque pointer wrappers + C entry points ───────────────────────── * * Same pattern as @gjsify/http2-native: opaque region travels as void* * across the FFI boundary; Vala destructor explicitly calls free. */ [CCode (cname = "gjsify_sab_region_new_anonymous", cheader_filename = "sab-helpers.h")] private extern void* _region_new_anonymous (size_t size); [CCode (cname = "gjsify_sab_region_new_from_fd", cheader_filename = "sab-helpers.h")] private extern void* _region_new_from_fd (int fd, size_t size); [CCode (cname = "gjsify_sab_region_free", cheader_filename = "sab-helpers.h")] private extern void _region_free (void* region); [CCode (cname = "gjsify_sab_region_get_fd", cheader_filename = "sab-helpers.h")] private extern int _region_get_fd (void* region); [CCode (cname = "gjsify_sab_region_get_size", cheader_filename = "sab-helpers.h")] private extern size_t _region_get_size (void* region); /* Read/write */ [CCode (cname = "gjsify_sab_region_read_u8", cheader_filename = "sab-helpers.h")] private extern uint8 _region_read_u8 (void* region, size_t offset); [CCode (cname = "gjsify_sab_region_write_u8", cheader_filename = "sab-helpers.h")] private extern void _region_write_u8 (void* region, size_t offset, uint8 v); [CCode (cname = "gjsify_sab_region_read_u32_le", cheader_filename = "sab-helpers.h")] private extern uint32 _region_read_u32_le (void* region, size_t offset); [CCode (cname = "gjsify_sab_region_write_u32_le", cheader_filename = "sab-helpers.h")] private extern void _region_write_u32_le (void* region, size_t offset, uint32 v); [CCode (cname = "gjsify_sab_region_read_i32_le", cheader_filename = "sab-helpers.h")] private extern int32 _region_read_i32_le (void* region, size_t offset); [CCode (cname = "gjsify_sab_region_write_i32_le", cheader_filename = "sab-helpers.h")] private extern void _region_write_i32_le (void* region, size_t offset, int32 v); [CCode (cname = "gjsify_sab_region_read_u64_le", cheader_filename = "sab-helpers.h")] private extern uint64 _region_read_u64_le (void* region, size_t offset); [CCode (cname = "gjsify_sab_region_write_u64_le", cheader_filename = "sab-helpers.h")] private extern void _region_write_u64_le (void* region, size_t offset, uint64 v); /* Bulk */ [CCode (cname = "gjsify_sab_region_read_bytes", cheader_filename = "sab-helpers.h")] private extern GLib.Bytes _region_read_bytes (void* region, size_t offset, size_t length); [CCode (cname = "gjsify_sab_region_write_bytes", cheader_filename = "sab-helpers.h")] private extern void _region_write_bytes (void* region, size_t offset, GLib.Bytes data); /* Atomics */ [CCode (cname = "gjsify_sab_region_atomic_add_i32", cheader_filename = "sab-helpers.h")] private extern int32 _region_atomic_add_i32 (void* region, size_t offset, int32 v); [CCode (cname = "gjsify_sab_region_atomic_sub_i32", cheader_filename = "sab-helpers.h")] private extern int32 _region_atomic_sub_i32 (void* region, size_t offset, int32 v); [CCode (cname = "gjsify_sab_region_atomic_load_i32", cheader_filename = "sab-helpers.h")] private extern int32 _region_atomic_load_i32 (void* region, size_t offset); [CCode (cname = "gjsify_sab_region_atomic_store_i32", cheader_filename = "sab-helpers.h")] private extern void _region_atomic_store_i32 (void* region, size_t offset, int32 v); [CCode (cname = "gjsify_sab_region_atomic_xchg_i32", cheader_filename = "sab-helpers.h")] private extern int32 _region_atomic_xchg_i32 (void* region, size_t offset, int32 v); [CCode (cname = "gjsify_sab_region_atomic_cmpxchg_i32", cheader_filename = "sab-helpers.h")] private extern bool _region_atomic_cmpxchg_i32 (void* region, size_t offset, ref int32 expected, int32 desired); /* Futex */ [CCode (cname = "gjsify_sab_region_futex_wait", cheader_filename = "sab-helpers.h")] private extern int _region_futex_wait (void* region, size_t offset, int32 expected, int64 timeout_ms); [CCode (cname = "gjsify_sab_region_futex_wake", cheader_filename = "sab-helpers.h")] private extern int _region_futex_wake (void* region, size_t offset, int count); /* ── Public GObject wrapper ─────────────────────────────────────────── */ public class SharedBuffer : GLib.Object { /* Opaque region pointer. Lifetime: bound to this instance, freed * in the destructor. */ private void* _region; /* Default constructor — never used directly from JS (factory only). */ private SharedBuffer.with_region (void* region) { this._region = region; } /** * Allocate a fresh anonymous shared-memory region. Returns null if * the underlying memfd_create / mmap fails (errno preserved on * the calling thread). */ public static SharedBuffer? create (size_t size) { void* r = _region_new_anonymous (size); if (r == null) return null; return new SharedBuffer.with_region (r); } /** * Map an existing shared-memory fd into this process. The fd is * dup'd; the caller retains ownership of their copy and may close * it after this call returns. */ public static SharedBuffer? from_fd (int fd, size_t size) { void* r = _region_new_from_fd (fd, size); if (r == null) return null; return new SharedBuffer.with_region (r); } public int fd { get { return _region_get_fd (_region); } } public size_t byte_length { get { return _region_get_size (_region); } } /* Read / write — slow path, one accessor per integer width. * For bulk operations use read_bytes / write_bytes. */ public uint8 get_u8 (size_t offset) { return _region_read_u8 (_region, offset); } public void set_u8 (size_t offset, uint8 v) { _region_write_u8 (_region, offset, v); } public uint32 get_u32_le (size_t offset) { return _region_read_u32_le (_region, offset); } public void set_u32_le (size_t offset, uint32 v) { _region_write_u32_le(_region, offset, v); } public int32 get_i32_le (size_t offset) { return _region_read_i32_le (_region, offset); } public void set_i32_le (size_t offset, int32 v) { _region_write_i32_le(_region, offset, v); } public uint64 get_u64_le (size_t offset) { return _region_read_u64_le (_region, offset); } public void set_u64_le (size_t offset, uint64 v) { _region_write_u64_le(_region, offset, v); } /* Bulk: zero-copy read (Bytes borrows the mmap), memcpy write. */ public GLib.Bytes read_bytes (size_t offset, size_t length) { return _region_read_bytes (_region, offset, length); } public void write_bytes (size_t offset, GLib.Bytes data) { _region_write_bytes (_region, offset, data); } /* Atomics — SEQ_CST. fetch-style: return value BEFORE the op. */ public int32 atomic_add_i32 (size_t offset, int32 v) { return _region_atomic_add_i32 (_region, offset, v); } public int32 atomic_sub_i32 (size_t offset, int32 v) { return _region_atomic_sub_i32 (_region, offset, v); } public int32 atomic_load_i32 (size_t offset) { return _region_atomic_load_i32 (_region, offset); } public void atomic_store_i32 (size_t offset, int32 v) { _region_atomic_store_i32(_region, offset, v); } public int32 atomic_xchg_i32 (size_t offset, int32 v) { return _region_atomic_xchg_i32 (_region, offset, v); } /** * Strong compare-and-swap on a 32-bit slot. * Returns the actual previous value. CAS succeeded iff the * returned value === @expected. */ public int32 atomic_cmpxchg_i32 (size_t offset, int32 expected, int32 desired) { int32 actual = expected; _region_atomic_cmpxchg_i32 (_region, offset, ref actual, desired); return actual; } /** * Linux futex_wait. Compares *((int32_t*)region+offset) to @expected; * if equal, blocks until woken or timeout. timeout_ms < 0 = infinite. * * Return: 0 woken, -1 not-equal (EAGAIN), -2 timed-out, -3 interrupted, * other negative = generic errno. */ public int futex_wait (size_t offset, int32 expected, int64 timeout_ms) { return _region_futex_wait (_region, offset, expected, timeout_ms); } /** * Wake up to @count waiters on this address. Returns number actually * woken (can be less than count). */ public int futex_wake (size_t offset, int count) { return _region_futex_wake (_region, offset, count); } ~SharedBuffer () { if (_region != null) { _region_free (_region); _region = null; } } } }