feat(linux): Ported aio to linux

I had to rename the header, because the POSIX async io header has the same name.

src/asset_compiler/asset_compiler.c

@@ -1,7 +1,7 @@
 #include "asset_compiler.h"
 #include "processor.h"
 
-#include "runtime/aio.h"
+#include "runtime/rt_aio.h"
 #include "runtime/buffer_manager.h"
 #include "runtime/config.h"
 #include "runtime/file_tab.h"

src/runtime/aio.c

@@ -1,377 +0,0 @@
-#include "aio.h"
-#include "config.h"
-#include "threading.h"
-
-#ifdef _WIN32
-#define WIN32_LEAN_AND_MEAN
-#include <windows.h>
-
-void Win32ErrorToString(DWORD last_error, char *out, int bufsize);
-
-#elif defined(__linux__)
-#include <sched.h>
-
-#endif
-
-#include <assert.h>
-#include <stdlib.h>
-
-/* Maintain a ringbuffer of pending operations */
-
-typedef struct {
-#ifdef _WIN32
-    HANDLE file_handle;
-    OVERLAPPED overlapped;
-#endif
-    volatile rt_aio_state state;
-} rt_aio;
-
-typedef struct {
-    rt_mutex *guard;
-
-    rt_aio *storage;
-    uint32_t capacity;
-    uint32_t head;
-    uint32_t tail;
-} rt_aio_ringbuffer;
-
-typedef struct {
-    rt_aio *a;
-    rt_aio *b;
-    uint32_t a_count;
-} rt_ringbuffer_space;
-
-static rt_aio_ringbuffer _ringbuffer;
-
-static rt_ringbuffer_space ReserveRingbufferSpace(uint32_t count) {
-    if (!rtLockMutex(_ringbuffer.guard)) {
-        rt_ringbuffer_space failed = {NULL, NULL, 0};
-        return failed;
-    }
-
-    rt_ringbuffer_space result = {NULL, NULL, 0};
-
-    if (_ringbuffer.head >= _ringbuffer.tail) {
-        if (_ringbuffer.head + count <= _ringbuffer.capacity) {
-            result.a_count   = count;
-            result.a         = &_ringbuffer.storage[_ringbuffer.head];
-            _ringbuffer.head = (_ringbuffer.head + count) % _ringbuffer.capacity;
-        } else {
-            /* Check if enough space is free at the end */
-            uint32_t a_count = _ringbuffer.capacity - _ringbuffer.head;
-            uint32_t b_count = count - a_count;
-
-            if (b_count <= _ringbuffer.tail) {
-                result.a_count   = a_count;
-                result.a         = &_ringbuffer.storage[_ringbuffer.head];
-                result.b         = &_ringbuffer.storage[0];
-                _ringbuffer.head = b_count;
-            } else {
-                /* Not enough space, we would overwrite the tail */
-                rtLog("aio", "Ringbuffer is full.");
-            }
-        }
-    } else {
-        /* Head is lower than tail */
-        uint32_t num_free = _ringbuffer.tail - _ringbuffer.head;
-        if (count < num_free) {
-            result.a_count   = count;
-            result.a         = &_ringbuffer.storage[_ringbuffer.head];
-            _ringbuffer.head = (_ringbuffer.head + count) % _ringbuffer.capacity;
-        } else {
-            /* Not enough space, we would overwrite the tail */
-            rtLog("aio", "Ringbuffer is full.");
-        }
-    }
-
-    rtUnlockMutex(_ringbuffer.guard);
-    return result;
-}
-
-#ifdef _WIN32
-static void
-win32CompletionRoutine(DWORD error_code, DWORD num_bytes_transfered, LPOVERLAPPED overlapped) {
-    rt_aio *op = (rt_aio *)overlapped->hEvent;
-    assert(op->state == RT_AIO_STATE_PENDING);
-
-    if (error_code != ERROR_SUCCESS) {
-        op->state = RT_AIO_STATE_FAILED;
-        rtLog("aio", "Async io failed: %u", error_code);
-    } else {
-        op->state = RT_AIO_STATE_FINISHED;
-    }
-
-    CloseHandle(op->file_handle);
-}
-#endif
-
-RT_CVAR_I(rt_MaxConcurrentAsyncIO,
-          "Maximum number of concurrent async. I/O operations. Default: 1024",
-          1024);
-
-rt_result InitAIO(void) {
-    unsigned int max_concurrent_operations = rt_MaxConcurrentAsyncIO.i;
-    _ringbuffer.guard                      = rtCreateMutex();
-    if (!_ringbuffer.guard) {
-        return RT_AIO_OUT_OF_MEMORY;
-    }
-    if (max_concurrent_operations == 0)
-        max_concurrent_operations = 1024;
-
-    _ringbuffer.storage = calloc(max_concurrent_operations, sizeof(rt_aio));
-    if (!_ringbuffer.storage)
-        return RT_AIO_OUT_OF_MEMORY;
-    _ringbuffer.head     = 0;
-    _ringbuffer.tail     = 0;
-    _ringbuffer.capacity = max_concurrent_operations;
-    return RT_SUCCESS;
-}
-
-void ShutdownAIO(void) {
-    rtDestroyMutex(_ringbuffer.guard);
-    free(_ringbuffer.storage);
-    _ringbuffer.capacity = 0;
-}
-
-RT_DLLEXPORT rt_result rtSubmitLoadBatch(const rt_load_batch *batch, rt_aio_handle *handles) {
-    if (batch->num_loads > RT_LOAD_BATCH_MAX_SIZE) {
-        return RT_AIO_LOAD_TOO_LARGE;
-    }
-
-    rt_ringbuffer_space rbspace = ReserveRingbufferSpace(batch->num_loads);
-    if (!rbspace.a) {
-        rtReportError("aio", "Too many pending file operations");
-        return RT_AIO_TOO_MANY_OPERATIONS;
-    }
-
-    for (unsigned int i = 0; i < batch->num_loads; ++i) {
-        rt_aio *op = (i < rbspace.a_count) ? &rbspace.a[i] : &rbspace.b[i - rbspace.a_count];
-        op->state  = RT_AIO_STATE_PENDING;
-        const char *file_path = rtGetFilePath(batch->loads[i].file);
-        if (!file_path) {
-            rtReportError("aio", "Failed to resolve file path for a batched load");
-            op->state  = RT_AIO_STATE_INVALID;
-            handles[i] = RT_AIO_INVALID_HANDLE;
-            continue;
-        }
-#ifdef _WIN32
-        op->overlapped = (OVERLAPPED){
-            /* ReadFileEx does not use hEvent and we are free to use it for our own purposes. */
-            .hEvent       = (HANDLE)(op),
-            .Internal     = 0,
-            .InternalHigh = 0,
-            .Offset       = (DWORD)(batch->loads[i].offset & MAXDWORD),
-            .OffsetHigh   = (DWORD)(batch->loads[i].offset >> 32),
-        };
-
-        WCHAR wpath[MAX_PATH];
-        if (MultiByteToWideChar(CP_UTF8,
-                                MB_PRECOMPOSED,
-                                file_path,
-                                -1,
-                                wpath,
-                                RT_ARRAY_COUNT(wpath)) == 0) {
-            rtReportError("aio", "MultiByteToWideChar failed with error code: %u", GetLastError());
-            op->state  = RT_AIO_STATE_FINISHED;
-            handles[i] = RT_AIO_INVALID_HANDLE;
-            continue;
-        }
-
-        HANDLE file_handle = CreateFileW(wpath,
-                                         GENERIC_READ,
-                                         FILE_SHARE_READ,
-                                         NULL,
-                                         OPEN_EXISTING,
-                                         FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED,
-                                         NULL);
-        if (file_handle == INVALID_HANDLE_VALUE) {
-            DWORD err = GetLastError();
-            char error_msg[256];
-            Win32ErrorToString(err, error_msg, 256);
-            rtReportError("aio",
-                          "CreateFileW failed for file: %s with error code: %u  (%s)",
-                          file_path,
-                          err,
-                          error_msg);
-            op->state  = RT_AIO_STATE_INVALID;
-            handles[i] = RT_AIO_INVALID_HANDLE;
-            continue;
-        }
-        op->file_handle = file_handle;
-        BOOL result     = ReadFileEx(file_handle,
-                                 batch->loads[i].dest,
-                                 (DWORD)batch->loads[i].num_bytes,
-                                 &op->overlapped,
-                                 win32CompletionRoutine);
-        DWORD err       = GetLastError();
-        if (!result || err != ERROR_SUCCESS) {
-            char error_msg[256];
-            Win32ErrorToString(err, error_msg, 256);
-            rtReportError("aio", "ReadFileEx failed with error code: %u  (%s)", err, error_msg);
-            op->state  = RT_AIO_STATE_FINISHED;
-            handles[i] = RT_AIO_INVALID_HANDLE;
-            CloseHandle(file_handle);
-            op->file_handle = NULL;
-        }
-
-        /* Handle is the index into the ringbuffer + 1 */
-        ptrdiff_t op_idx = op - _ringbuffer.storage;
-        handles[i]       = (uint32_t)op_idx + 1;
-#endif
-    }
-
-    return RT_SUCCESS;
-}
-
-RT_DLLEXPORT rt_result rtSubmitWriteBatch(const rt_write_batch *batch, rt_aio_handle *handles) {
-    if (batch->num_writes > RT_LOAD_BATCH_MAX_SIZE) {
-        return RT_AIO_WRITE_TOO_LARGE;
-    }
-
-    rt_ringbuffer_space rbspace = ReserveRingbufferSpace(batch->num_writes);
-    if (!rbspace.a) {
-        rtReportError("aio", "Too many pending file operations");
-        return RT_AIO_TOO_MANY_OPERATIONS;
-    }
-
-    for (unsigned int i = 0; i < batch->num_writes; ++i) {
-        rt_aio *op = (i < rbspace.a_count) ? &rbspace.a[i] : &rbspace.b[i - rbspace.a_count];
-        op->state  = RT_AIO_STATE_PENDING;
-        const char *file_path = rtGetFilePath(batch->writes[i].file);
-        if (!file_path) {
-            rtReportError("aio", "Failed to resolve file path for a batched write");
-            op->state  = RT_AIO_STATE_INVALID;
-            handles[i] = RT_AIO_INVALID_HANDLE;
-            continue;
-        }
-#ifdef _WIN32
-        op->overlapped = (OVERLAPPED){
-            /* ReadFileEx does not use hEvent and we are free to use it for our own purposes. */
-            .hEvent       = (HANDLE)(op),
-            .Internal     = 0,
-            .InternalHigh = 0,
-            .Offset       = (DWORD)(batch->writes[i].offset & MAXDWORD),
-            .OffsetHigh   = (DWORD)(batch->writes[i].offset >> 32),
-        };
-
-        WCHAR wpath[MAX_PATH];
-        if (MultiByteToWideChar(CP_UTF8,
-                                MB_PRECOMPOSED,
-                                file_path,
-                                -1,
-                                wpath,
-                                RT_ARRAY_COUNT(wpath)) == 0) {
-            rtReportError("aio", "MultiByteToWideChar failed with error code: %u", GetLastError());
-            op->state  = RT_AIO_STATE_FINISHED;
-            handles[i] = RT_AIO_INVALID_HANDLE;
-            continue;
-        }
-
-        HANDLE file_handle = CreateFileW(wpath,
-                                         GENERIC_WRITE,
-                                         0,
-                                         NULL,
-                                         OPEN_ALWAYS,
-                                         FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED,
-                                         NULL);
-        if (file_handle == INVALID_HANDLE_VALUE) {
-            DWORD err = GetLastError();
-            char error_msg[256];
-            Win32ErrorToString(err, error_msg, 256);
-            rtReportError("aio",
-                          "CreateFileW failed for file: %s with error code: %u  (%s)",
-                          file_path,
-                          err,
-                          error_msg);
-            op->state  = RT_AIO_STATE_INVALID;
-            handles[i] = RT_AIO_INVALID_HANDLE;
-            continue;
-        }
-        op->file_handle = file_handle;
-        BOOL result     = WriteFileEx(file_handle,
-                                  batch->writes[i].buffer,
-                                  (DWORD)batch->writes[i].num_bytes,
-                                  &op->overlapped,
-                                  win32CompletionRoutine);
-        DWORD err       = GetLastError();
-        if (!result || (err != ERROR_SUCCESS && err != ERROR_ALREADY_EXISTS)) {
-            char error_msg[256];
-            Win32ErrorToString(err, error_msg, 256);
-            rtReportError("aio", "WriteFileEx failed with error code: %u  (%s)", err, error_msg);
-            op->state  = RT_AIO_STATE_FINISHED;
-            handles[i] = RT_AIO_INVALID_HANDLE;
-            CloseHandle(file_handle);
-            op->file_handle = NULL;
-        }
-
-        /* Handle is the index into the ringbuffer + 1 */
-        ptrdiff_t op_idx = op - _ringbuffer.storage;
-        handles[i]       = (uint32_t)op_idx + 1;
-#endif
-    }
-
-    return RT_SUCCESS;
-}
-
-RT_DLLEXPORT rt_aio_state rtGetAIOState(rt_aio_handle handle) {
-    if (handle == RT_AIO_INVALID_HANDLE || handle > _ringbuffer.capacity)
-        return RT_AIO_STATE_INVALID;
-#ifdef _WIN32
-    /* Give the compation function an opportunity to run */
-    SleepEx(0, TRUE);
-#endif
-    rtLockMutex(_ringbuffer.guard);
-    rt_aio_state state = _ringbuffer.storage[handle - 1].state;
-    rtUnlockMutex(_ringbuffer.guard);
-    return state;
-}
-
-RT_DLLEXPORT void rtReleaseAIO(rt_aio_handle handle) {
-    if (handle == RT_AIO_INVALID_HANDLE || handle > _ringbuffer.capacity) {
-        return;
-    }
-    rtLockMutex(_ringbuffer.guard);
-    _ringbuffer.storage[handle - 1].state = RT_AIO_STATE_INVALID;
-    if (handle - 1 == _ringbuffer.tail) {
-        /* Advance the tail such that it points to the last used slot. (Or to head, if the
-         * ringbuffer is now empty) */
-        uint32_t i = _ringbuffer.tail;
-        while ((_ringbuffer.storage[i].state == RT_AIO_STATE_INVALID) && i != _ringbuffer.head) {
-            i = (i + 1) % _ringbuffer.capacity;
-        }
-        _ringbuffer.tail = i;
-    }
-    rtUnlockMutex(_ringbuffer.guard);
-}
-
-RT_DLLEXPORT rt_aio_state rtWaitForAIOCompletion(rt_aio_handle handle) {
-    if (handle == RT_AIO_INVALID_HANDLE || handle > _ringbuffer.capacity)
-        return RT_AIO_STATE_INVALID;
-    rt_aio_state state;
-    do {
-        state = rtGetAIOState(handle);
-        /* NOTE(Kevin): This is where we could temporarily run a job. */
-#ifdef _WIN32
-        YieldProcessor();
-#elif defined(__linux__)
-        sched_yield();
-#endif
-    } while (state == RT_AIO_STATE_PENDING);
-    return state;
-}
-
-RT_DLLEXPORT rt_result rtSubmitSingleLoad(rt_file_load load, rt_aio_handle *handle) {
-    rt_load_batch batch;
-    batch.loads[0]  = load;
-    batch.num_loads = 1;
-    return rtSubmitLoadBatch(&batch, handle);
-}
-
-RT_DLLEXPORT rt_aio_state rtSubmitSingleLoadSync(rt_file_load load) {
-    rt_aio_handle handle;
-    if (rtSubmitSingleLoad(load, &handle) != RT_SUCCESS)
-        return RT_AIO_STATE_FAILED;
-    rt_aio_state state = rtWaitForAIOCompletion(handle);
-    rtReleaseAIO(handle);
-    return state;
-}

src/runtime/config.c

@@ -3,7 +3,7 @@
 #include "runtime.h"
 #include "threading.h"
 
-#include "aio.h"
+#include "rt_aio.h"
 #include "buffer_manager.h"
 #include "file_tab.h"
 #include "mem_arena.h"

src/runtime/fsutils.c

@@ -258,16 +258,13 @@ RT_DLLEXPORT uint64_t rtGetFileModificationTimestamp(const char *path) {
 }
 
 RT_DLLEXPORT bool rtSyncReadWholeFile(const char *path, void *dest, size_t dest_size) {
+    size_t fsz = rtGetFileSize(path);
+    if (fsz > dest_size) {
+        return false;
+    }
     FILE *f = fopen(path, "rb");
     if (!f)
         return false;
-    fseek(f, SEEK_END, 0);
-    size_t fsz = (size_t)ftell(f);
-    fseek(f, SEEK_SET, 0);
-    if (fsz > dest_size) {
-        fclose(f);
-        return false;
-    }
     size_t n = fread(dest, 1, fsz, f);
     fclose(f);
     return n == fsz;

src/runtime/meson.build

@@ -7,10 +7,15 @@ xxhash_proj = subproject('xxhash', default_options: ['default_library=static', '
 xxhash_dep = xxhash_proj.get_variable('xxhash_dep')
 
 runtime_deps = [thread_dep, m_dep, inih_dep, lz4_dep, xxhash_dep]
+
+if host_machine.system() == 'linux'
+  rt_dep = declare_dependency(link_args: ['-lrt'])
+  runtime_deps += rt_dep
+endif
+
 runtime_incdirs = contrib_incdir
 runtime_lib = library('rt',
   # Project Sources
-  'aio.h',
   'atomics.h',
   'buffer_manager.h',
   'compression.h',
@@ -25,13 +30,13 @@ runtime_lib = library('rt',
   'jobs.h',
   'mem_arena.h',
   'resources.h',
+  'rt_aio.h',
   'runtime.h',
   'string_storage.h',
   'threading.h',
   'threading_helpers.hpp',
   'timing.h',
-  
-  'aio.c',
+
   'assert.c',
   'buffer_manager.c',
   'compression.c',
@@ -48,6 +53,7 @@ runtime_lib = library('rt',
   'jobs.c',
   'mem_arena.c',
   'resource_manager.c',
+  'rt_aio.c',
   'sprint.c',
   'string_storage.c',
   'text.c',

src/runtime/resource_manager.c

@@ -1,4 +1,4 @@
-#include "aio.h"
+#include "rt_aio.h"
 #include "buffer_manager.h"
 #include "compression.h"
 #include "config.h"

src/runtime/rt_aio.c

@@ -0,0 +1,503 @@
+#include "rt_aio.h"
+#include "config.h"
+#include "runtime.h"
+#include "threading.h"
+
+#ifdef _WIN32
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+
+void Win32ErrorToString(DWORD last_error, char *out, int bufsize);
+
+#elif defined(__linux__)
+#include <sys/types.h>
+#include <sys/file.h>
+#include <sched.h>
+#include <aio.h>
+#include <signal.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+
+
+#define IO_SIGNAL SIGUSR1
+
+#endif
+
+#include <assert.h>
+#include <stdlib.h>
+
+/* Maintain a ringbuffer of pending operations */
+
+typedef struct {
+#ifdef _WIN32
+    HANDLE file_handle;
+    OVERLAPPED overlapped;
+#elif defined(__linux__)
+    int fd;
+    struct aiocb64 cb;
+#endif
+    volatile rt_aio_state state;
+} rt_aio;
+
+typedef struct {
+    rt_mutex *guard;
+
+    rt_aio *storage;
+    uint32_t capacity;
+    uint32_t head;
+    uint32_t tail;
+} rt_aio_ringbuffer;
+
+typedef struct {
+    rt_aio *a;
+    rt_aio *b;
+    uint32_t a_count;
+} rt_ringbuffer_space;
+
+static rt_aio_ringbuffer _ringbuffer;
+
+static rt_ringbuffer_space ReserveRingbufferSpace(uint32_t count) {
+    if (!rtLockMutex(_ringbuffer.guard)) {
+        rt_ringbuffer_space failed = {NULL, NULL, 0};
+        return failed;
+    }
+
+    rt_ringbuffer_space result = {NULL, NULL, 0};
+
+    if (_ringbuffer.head >= _ringbuffer.tail) {
+        if (_ringbuffer.head + count <= _ringbuffer.capacity) {
+            result.a_count   = count;
+            result.a         = &_ringbuffer.storage[_ringbuffer.head];
+            _ringbuffer.head = (_ringbuffer.head + count) % _ringbuffer.capacity;
+        } else {
+            /* Check if enough space is free at the end */
+            uint32_t a_count = _ringbuffer.capacity - _ringbuffer.head;
+            uint32_t b_count = count - a_count;
+
+            if (b_count <= _ringbuffer.tail) {
+                result.a_count   = a_count;
+                result.a         = &_ringbuffer.storage[_ringbuffer.head];
+                result.b         = &_ringbuffer.storage[0];
+                _ringbuffer.head = b_count;
+            } else {
+                /* Not enough space, we would overwrite the tail */
+                rtLog("aio", "Ringbuffer is full.");
+            }
+        }
+    } else {
+        /* Head is lower than tail */
+        uint32_t num_free = _ringbuffer.tail - _ringbuffer.head;
+        if (count < num_free) {
+            result.a_count   = count;
+            result.a         = &_ringbuffer.storage[_ringbuffer.head];
+            _ringbuffer.head = (_ringbuffer.head + count) % _ringbuffer.capacity;
+        } else {
+            /* Not enough space, we would overwrite the tail */
+            rtLog("aio", "Ringbuffer is full.");
+        }
+    }
+
+    rtUnlockMutex(_ringbuffer.guard);
+    return result;
+}
+
+#ifdef _WIN32
+static void
+win32CompletionRoutine(DWORD error_code, DWORD num_bytes_transfered, LPOVERLAPPED overlapped) {
+    rt_aio *op = (rt_aio *)overlapped->hEvent;
+    assert(op->state == RT_AIO_STATE_PENDING);
+
+    if (error_code != ERROR_SUCCESS) {
+        op->state = RT_AIO_STATE_FAILED;
+        rtLog("aio", "Async io failed: %u", error_code);
+    } else {
+        op->state = RT_AIO_STATE_FINISHED;
+    }
+
+    CloseHandle(op->file_handle);
+}
+
+#elif defined(__linux__)
+static void linuxAIOSigHandler(int sig, siginfo_t *si, void *ucontext) {
+    RT_ASSERT(sig == IO_SIGNAL, "The signal handler was called for an unexpected signal.");
+    if (si->si_code !=SI_ASYNCIO)
+        return;
+    rt_aio *op = si->si_value.sival_ptr;
+    RT_ASSERT(op->state == RT_AIO_STATE_PENDING, "The async io operation was in an unexpected state.");
+
+    if (si->si_errno != 0) {
+        const char *err = strerror(si->si_errno);
+        rtLog("aio", "Async io failed: %u (%s)", si->si_errno, err);
+        op->state = RT_AIO_STATE_FAILED;
+    }
+    else {
+        op->state = RT_AIO_STATE_FINISHED;
+    }
+    
+    close(op->fd);
+    op->fd = -1;
+}
+#endif
+
+RT_CVAR_I(rt_MaxConcurrentAsyncIO,
+          "Maximum number of concurrent async. I/O operations. Default: 1024",
+          1024);
+
+rt_result InitAIO(void) {
+    unsigned int max_concurrent_operations = rt_MaxConcurrentAsyncIO.i;
+    _ringbuffer.guard                      = rtCreateMutex();
+    if (!_ringbuffer.guard) {
+        return RT_AIO_OUT_OF_MEMORY;
+    }
+    if (max_concurrent_operations == 0)
+        max_concurrent_operations = 1024;
+
+    _ringbuffer.storage = calloc(max_concurrent_operations, sizeof(rt_aio));
+    if (!_ringbuffer.storage)
+        return RT_AIO_OUT_OF_MEMORY;
+    _ringbuffer.head     = 0;
+    _ringbuffer.tail     = 0;
+    _ringbuffer.capacity = max_concurrent_operations;
+
+#ifdef __linux__
+    /* Register the handler for the IO completion signal */
+    struct sigaction sa;
+    sigemptyset(&sa.sa_mask);
+    sa.sa_flags = SA_RESTART | SA_SIGINFO;
+    sa.sa_sigaction = linuxAIOSigHandler;
+    if (sigaction(IO_SIGNAL, &sa, NULL) == -1) {
+        return RT_UNKNOWN_ERROR;
+    }
+#endif
+
+    return RT_SUCCESS;
+}
+
+void ShutdownAIO(void) {
+    rtDestroyMutex(_ringbuffer.guard);
+    free(_ringbuffer.storage);
+    _ringbuffer.capacity = 0;
+}
+
+#ifdef _WIN32
+static void win32LoadBatchInner(const char *file_path, const rt_file_load *load, rt_aio *op, rt_aio_handle *handle) {
+    op->overlapped = (OVERLAPPED){
+        /* ReadFileEx does not use hEvent and we are free to use it for our own purposes. */
+        .hEvent       = (HANDLE)(op),
+        .Internal     = 0,
+        .InternalHigh = 0,
+        .Offset       = (DWORD)(load->offset & MAXDWORD),
+        .OffsetHigh   = (DWORD)(load->offset >> 32),
+    };
+
+    WCHAR wpath[MAX_PATH];
+    if (MultiByteToWideChar(CP_UTF8, MB_PRECOMPOSED, file_path, -1, wpath, RT_ARRAY_COUNT(wpath)) ==
+        0) {
+        rtReportError("aio", "MultiByteToWideChar failed with error code: %u", GetLastError());
+        op->state = RT_AIO_STATE_FINISHED;
+        *handle   = RT_AIO_INVALID_HANDLE;
+        return;
+    }
+
+    HANDLE file_handle = CreateFileW(wpath,
+                                     GENERIC_READ,
+                                     FILE_SHARE_READ,
+                                     NULL,
+                                     OPEN_EXISTING,
+                                     FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED,
+                                     NULL);
+    if (file_handle == INVALID_HANDLE_VALUE) {
+        DWORD err = GetLastError();
+        char error_msg[256];
+        Win32ErrorToString(err, error_msg, 256);
+        rtReportError("aio",
+                      "CreateFileW failed for file: %s with error code: %u  (%s)",
+                      file_path,
+                      err,
+                      error_msg);
+        op->state = RT_AIO_STATE_INVALID;
+        *handle   = RT_AIO_INVALID_HANDLE;
+        return;
+    }
+    op->file_handle = file_handle;
+    BOOL result     = ReadFileEx(file_handle,
+                             load->dest,
+                             (DWORD)load->num_bytes,
+                             &op->overlapped,
+                             win32CompletionRoutine);
+    DWORD err       = GetLastError();
+    if (!result || err != ERROR_SUCCESS) {
+        char error_msg[256];
+        Win32ErrorToString(err, error_msg, 256);
+        rtReportError("aio", "ReadFileEx failed with error code: %u  (%s)", err, error_msg);
+        op->state  = RT_AIO_STATE_FINISHED;
+        *handle = RT_AIO_INVALID_HANDLE;
+        CloseHandle(file_handle);
+        op->file_handle = NULL;
+    }
+
+    /* Handle is the index into the ringbuffer + 1 */
+    ptrdiff_t op_idx = op - _ringbuffer.storage;
+    *handle          = (uint32_t)op_idx + 1;
+}
+#endif
+
+#ifdef __linux__
+static void linuxLoadBatchInner(const char *file_path, const rt_file_load *load, rt_aio *op, rt_aio_handle *handle) {
+    memset(&op->cb, 0, sizeof(op->cb));
+    int fd = open(file_path, O_RDONLY | O_LARGEFILE);
+    if (fd == -1) {
+        const char *err = strerror(errno);
+        rtReportError("aio", "open failed for file: %s with error: %d (%s)", file_path, errno, err);;
+        op->state = RT_AIO_STATE_INVALID;
+        *handle = RT_AIO_INVALID_HANDLE;
+        return;
+    }
+    op->fd = fd;
+    op->cb.aio_fildes = fd;
+    op->cb.aio_offset = load->offset;
+    op->cb.aio_buf = load->dest;
+    op->cb.aio_nbytes = load->num_bytes;
+    op->cb.aio_reqprio = 0;
+    op->cb.aio_sigevent.sigev_notify = SIGEV_SIGNAL;
+    op->cb.aio_sigevent.sigev_signo = IO_SIGNAL;
+    op->cb.aio_sigevent.sigev_value.sival_ptr = op;
+
+    if (aio_read64(&op->cb) == -1) {
+        const char *err = strerror(errno);
+        rtReportError("aio", "aio_read64 failed for file: %s with error: %d (%s)", file_path, errno, err);
+        close(fd);
+        op->state = RT_AIO_STATE_INVALID;
+        *handle = RT_AIO_INVALID_HANDLE;
+        return;
+    }
+
+    ptrdiff_t op_idx = op - _ringbuffer.storage;
+    *handle = (uint32_t)op_idx + 1;
+}
+#endif
+
+RT_DLLEXPORT rt_result rtSubmitLoadBatch(const rt_load_batch *batch, rt_aio_handle *handles) {
+    if (batch->num_loads > RT_LOAD_BATCH_MAX_SIZE) {
+        return RT_AIO_LOAD_TOO_LARGE;
+    }
+
+    rt_ringbuffer_space rbspace = ReserveRingbufferSpace(batch->num_loads);
+    if (!rbspace.a) {
+        rtReportError("aio", "Too many pending file operations");
+        return RT_AIO_TOO_MANY_OPERATIONS;
+    }
+
+    for (unsigned int i = 0; i < batch->num_loads; ++i) {
+        rt_aio *op = (i < rbspace.a_count) ? &rbspace.a[i] : &rbspace.b[i - rbspace.a_count];
+        op->state  = RT_AIO_STATE_PENDING;
+        const char *file_path = rtGetFilePath(batch->loads[i].file);
+        if (!file_path) {
+            rtReportError("aio", "Failed to resolve file path for a batched load");
+            op->state  = RT_AIO_STATE_INVALID;
+            handles[i] = RT_AIO_INVALID_HANDLE;
+            continue;
+        }
+#ifdef _WIN32
+        win32LoadBatchInner(file_path, &batch->loads[i], op, &handles[i]);
+#elif defined(__linux__)
+        linuxLoadBatchInner(file_path, &batch->loads[i], op, &handles[i]);
+#endif
+    }
+
+    return RT_SUCCESS;
+}
+
+#ifdef _WIN32
+static void win32WriteBatchInner(const char *file_path, const rt_file_write *write, rt_aio *op, rt_aio_handle *handle) {
+    op->overlapped = (OVERLAPPED){
+        /* ReadFileEx does not use hEvent and we are free to use it for our own purposes. */
+        .hEvent       = (HANDLE)(op),
+        .Internal     = 0,
+        .InternalHigh = 0,
+        .Offset       = (DWORD)(write->offset & MAXDWORD),
+        .OffsetHigh   = (DWORD)(write->offset >> 32),
+    };
+
+    WCHAR wpath[MAX_PATH];
+    if (MultiByteToWideChar(CP_UTF8, MB_PRECOMPOSED, file_path, -1, wpath, RT_ARRAY_COUNT(wpath)) ==
+        0) {
+        rtReportError("aio", "MultiByteToWideChar failed with error code: %u", GetLastError());
+        op->state = RT_AIO_STATE_FINISHED;
+        *handle   = RT_AIO_INVALID_HANDLE;
+        return;
+    }
+
+    HANDLE file_handle = CreateFileW(wpath,
+                                     GENERIC_WRITE,
+                                     0,
+                                     NULL,
+                                     OPEN_ALWAYS,
+                                     FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED,
+                                     NULL);
+    if (file_handle == INVALID_HANDLE_VALUE) {
+        DWORD err = GetLastError();
+        char error_msg[256];
+        Win32ErrorToString(err, error_msg, 256);
+        rtReportError("aio",
+                      "CreateFileW failed for file: %s with error code: %u  (%s)",
+                      file_path,
+                      err,
+                      error_msg);
+        op->state = RT_AIO_STATE_INVALID;
+        *handle   = RT_AIO_INVALID_HANDLE;
+        return;
+    }
+    op->file_handle = file_handle;
+    BOOL result     = WriteFileEx(file_handle,
+                              write->buffer,
+                              (DWORD)write->num_bytes,
+                              &op->overlapped,
+                              win32CompletionRoutine);
+    DWORD err       = GetLastError();
+    if (!result || (err != ERROR_SUCCESS && err != ERROR_ALREADY_EXISTS)) {
+        char error_msg[256];
+        Win32ErrorToString(err, error_msg, 256);
+        rtReportError("aio", "WriteFileEx failed with error code: %u  (%s)", err, error_msg);
+        op->state = RT_AIO_STATE_FINISHED;
+        *handle   = RT_AIO_INVALID_HANDLE;
+        CloseHandle(file_handle);
+        op->file_handle = INVALID_HANDLE;
+    }
+
+    /* Handle is the index into the ringbuffer + 1 */
+    ptrdiff_t op_idx = op - _ringbuffer.storage;
+    *handle          = (uint32_t)op_idx + 1;
+}
+#endif
+
+#ifdef __linux__
+static void linuxWriteBatchInner(const char *file_path, const rt_file_write *write, rt_aio *op, rt_aio_handle *handle) {
+    memset(&op->cb, 0, sizeof(op->cb));
+    int fd = open(file_path, O_WRONLY | O_CREAT | O_LARGEFILE);
+    if (fd == -1) {
+        const char *err = strerror(errno);
+        rtReportError("aio", "open failed for file: %s with error: %d (%s)", file_path, errno, err);;
+        op->state = RT_AIO_STATE_INVALID;
+        *handle = RT_AIO_INVALID_HANDLE;
+        return;
+    }
+    op->fd = fd;
+    op->cb.aio_fildes = fd;
+    op->cb.aio_offset = write->offset;
+    op->cb.aio_buf = (volatile void *)write->buffer;
+    op->cb.aio_nbytes = write->num_bytes;
+    op->cb.aio_reqprio = 0;
+    op->cb.aio_sigevent.sigev_notify = SIGEV_SIGNAL;
+    op->cb.aio_sigevent.sigev_signo = IO_SIGNAL;
+    op->cb.aio_sigevent.sigev_value.sival_ptr = op;
+
+    if (aio_write64(&op->cb) == -1) {
+        const char *err = strerror(errno);
+        rtReportError("aio", "aio_write64 failed for file: %s with error: %d (%s)", file_path, errno, err);
+        close(fd);
+        op->state = RT_AIO_STATE_INVALID;
+        *handle = RT_AIO_INVALID_HANDLE;
+        return;
+    }
+
+    ptrdiff_t op_idx = op - _ringbuffer.storage;
+    *handle = (uint32_t)op_idx + 1;
+}
+#endif
+
+RT_DLLEXPORT rt_result rtSubmitWriteBatch(const rt_write_batch *batch, rt_aio_handle *handles) {
+    if (batch->num_writes > RT_LOAD_BATCH_MAX_SIZE) {
+        return RT_AIO_WRITE_TOO_LARGE;
+    }
+
+    rt_ringbuffer_space rbspace = ReserveRingbufferSpace(batch->num_writes);
+    if (!rbspace.a) {
+        rtReportError("aio", "Too many pending file operations");
+        return RT_AIO_TOO_MANY_OPERATIONS;
+    }
+
+    for (unsigned int i = 0; i < batch->num_writes; ++i) {
+        rt_aio *op = (i < rbspace.a_count) ? &rbspace.a[i] : &rbspace.b[i - rbspace.a_count];
+        op->state  = RT_AIO_STATE_PENDING;
+        const char *file_path = rtGetFilePath(batch->writes[i].file);
+        if (!file_path) {
+            rtReportError("aio", "Failed to resolve file path for a batched write");
+            op->state  = RT_AIO_STATE_INVALID;
+            handles[i] = RT_AIO_INVALID_HANDLE;
+            continue;
+        }
+#ifdef _WIN32
+        win32WriteBatchInner(file_path, &batch->writes[i], op, &handles[i]);
+#elif defined(__linux__)
+        linuxWriteBatchInner(file_path, &batch->writes[i], op, &handles[i]);
+#endif
+    }
+
+    return RT_SUCCESS;
+}
+
+RT_DLLEXPORT rt_aio_state rtGetAIOState(rt_aio_handle handle) {
+    if (handle == RT_AIO_INVALID_HANDLE || handle > _ringbuffer.capacity)
+        return RT_AIO_STATE_INVALID;
+#ifdef _WIN32
+    /* Give the compation function an opportunity to run */
+    SleepEx(0, TRUE);
+#endif
+    rtLockMutex(_ringbuffer.guard);
+    rt_aio_state state = _ringbuffer.storage[handle - 1].state;
+    rtUnlockMutex(_ringbuffer.guard);
+    return state;
+}
+
+RT_DLLEXPORT void rtReleaseAIO(rt_aio_handle handle) {
+    if (handle == RT_AIO_INVALID_HANDLE || handle > _ringbuffer.capacity) {
+        return;
+    }
+    rtLockMutex(_ringbuffer.guard);
+    _ringbuffer.storage[handle - 1].state = RT_AIO_STATE_INVALID;
+    if (handle - 1 == _ringbuffer.tail) {
+        /* Advance the tail such that it points to the last used slot. (Or to head, if the
+         * ringbuffer is now empty) */
+        uint32_t i = _ringbuffer.tail;
+        while ((_ringbuffer.storage[i].state == RT_AIO_STATE_INVALID) && i != _ringbuffer.head) {
+            i = (i + 1) % _ringbuffer.capacity;
+        }
+        _ringbuffer.tail = i;
+    }
+    rtUnlockMutex(_ringbuffer.guard);
+}
+
+RT_DLLEXPORT rt_aio_state rtWaitForAIOCompletion(rt_aio_handle handle) {
+    if (handle == RT_AIO_INVALID_HANDLE || handle > _ringbuffer.capacity)
+        return RT_AIO_STATE_INVALID;
+    rt_aio_state state;
+    do {
+        state = rtGetAIOState(handle);
+        /* NOTE(Kevin): This is where we could temporarily run a job. */
+#ifdef _WIN32
+        YieldProcessor();
+#elif defined(__linux__)
+        sched_yield();
+#endif
+    } while (state == RT_AIO_STATE_PENDING);
+    return state;
+}
+
+RT_DLLEXPORT rt_result rtSubmitSingleLoad(rt_file_load load, rt_aio_handle *handle) {
+    rt_load_batch batch;
+    batch.loads[0]  = load;
+    batch.num_loads = 1;
+    return rtSubmitLoadBatch(&batch, handle);
+}
+
+RT_DLLEXPORT rt_aio_state rtSubmitSingleLoadSync(rt_file_load load) {
+    rt_aio_handle handle;
+    if (rtSubmitSingleLoad(load, &handle) != RT_SUCCESS)
+        return RT_AIO_STATE_FAILED;
+    rt_aio_state state = rtWaitForAIOCompletion(handle);
+    rtReleaseAIO(handle);
+    return state;
+}