From f05bb5306d60a30b2a519369e9f11d4f8a00745e Mon Sep 17 00:00:00 2001
From: David Reid <mackron@gmail.com>
Date: Thu, 18 May 2023 20:44:46 +1000
Subject: [PATCH] Try fixing Windows 95/98 build.

This commit makes it so SetFilePointer/Ex() are dynamically loaded at
runtime which allows miniaudio to branch dynamically based on available
support.

This is necessary because versions of Windows prior to XP do not
support the Ex version which results in an error when trying to run the
program.

Public issue https://github.com/mackron/miniaudio/issues/672
---
 miniaudio.h | 70 ++++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 53 insertions(+), 17 deletions(-)

diff --git a/miniaudio.h b/miniaudio.h
index 5bef689b..5c613f5d 100644
--- a/miniaudio.h
+++ b/miniaudio.h
@@ -58974,6 +58974,31 @@ MA_API ma_result ma_vfs_open_and_read_file_w(ma_vfs* pVFS, const wchar_t* pFileP
 #endif
 
 #if defined(MA_USE_WIN32_FILEIO)
+/*
+We need to dynamically load SetFilePointer or SetFilePointerEx because older versions of Windows do
+not have the Ex version. We therefore need to do some dynamic branching depending on what's available.
+
+We load these when we load our first file from the default VFS. It's left open for the life of the
+program and is left to the OS to uninitialize when the program terminates.
+*/
+typedef DWORD (__stdcall * ma_SetFilePointer_proc)(HANDLE hFile, LONG lDistanceToMove, LONG* lpDistanceToMoveHigh, DWORD dwMoveMethod);
+typedef BOOL  (__stdcall * ma_SetFilePointerEx_proc)(HANDLE hFile, LARGE_INTEGER liDistanceToMove, LARGE_INTEGER* lpNewFilePointer, DWORD dwMoveMethod);
+
+static ma_handle hKernel32DLL = NULL;
+static ma_SetFilePointer_proc   ma_SetFilePointer   = NULL;
+static ma_SetFilePointerEx_proc ma_SetFilePointerEx = NULL;
+
+static void ma_win32_fileio_init(void)
+{
+    if (hKernel32DLL == NULL) {
+        hKernel32DLL = ma_dlopen(NULL, "kernel32.dll");
+        if (hKernel32DLL != NULL) {
+            ma_SetFilePointer   = (ma_SetFilePointer_proc)  ma_dlsym(NULL, hKernel32DLL, "SetFilePointer");
+            ma_SetFilePointerEx = (ma_SetFilePointerEx_proc)ma_dlsym(NULL, hKernel32DLL, "SetFilePointerEx");
+        }
+    }
+}
+
 static void ma_default_vfs__get_open_settings_win32(ma_uint32 openMode, DWORD* pDesiredAccess, DWORD* pShareMode, DWORD* pCreationDisposition)
 {
     *pDesiredAccess = 0;
@@ -59005,6 +59030,9 @@ static ma_result ma_default_vfs_open__win32(ma_vfs* pVFS, const char* pFilePath,
 
     (void)pVFS;
 
+    /* Load some Win32 symbols dynamically so we can dynamically check for the existence of SetFilePointerEx. */
+    ma_win32_fileio_init();
+
     ma_default_vfs__get_open_settings_win32(openMode, &dwDesiredAccess, &dwShareMode, &dwCreationDisposition);
 
     hFile = CreateFileA(pFilePath, dwDesiredAccess, dwShareMode, NULL, dwCreationDisposition, FILE_ATTRIBUTE_NORMAL, NULL);
@@ -59025,6 +59053,9 @@ static ma_result ma_default_vfs_open_w__win32(ma_vfs* pVFS, const wchar_t* pFile
 
     (void)pVFS;
 
+    /* Load some Win32 symbols dynamically so we can dynamically check for the existence of SetFilePointerEx. */
+    ma_win32_fileio_init();
+
     ma_default_vfs__get_open_settings_win32(openMode, &dwDesiredAccess, &dwShareMode, &dwCreationDisposition);
 
     hFile = CreateFileW(pFilePath, dwDesiredAccess, dwShareMode, NULL, dwCreationDisposition, FILE_ATTRIBUTE_NORMAL, NULL);
@@ -59150,16 +59181,19 @@ static ma_result ma_default_vfs_seek__win32(ma_vfs* pVFS, ma_vfs_file file, ma_i
         dwMoveMethod = FILE_BEGIN;
     }
 
-#if (defined(_MSC_VER) && _MSC_VER <= 1200) || defined(__DMC__)
-    /* No SetFilePointerEx() so restrict to 31 bits. */
-    if (origin > 0x7FFFFFFF) {
-        return MA_OUT_OF_RANGE;
+    if (ma_SetFilePointerEx != NULL) {
+        result = ma_SetFilePointerEx((HANDLE)file, liDistanceToMove, NULL, dwMoveMethod);
+    } else if (ma_SetFilePointer != NULL) {
+        /* No SetFilePointerEx() so restrict to 31 bits. */
+        if (origin > 0x7FFFFFFF) {
+            return MA_OUT_OF_RANGE;
+        }
+
+        result = ma_SetFilePointer((HANDLE)file, (LONG)liDistanceToMove.QuadPart, NULL, dwMoveMethod);
+    } else {
+        return MA_NOT_IMPLEMENTED;
     }
 
-    result = SetFilePointer((HANDLE)file, (LONG)liDistanceToMove.QuadPart, NULL, dwMoveMethod);
-#else
-    result = SetFilePointerEx((HANDLE)file, liDistanceToMove, NULL, dwMoveMethod);
-#endif
     if (result == 0) {
         return ma_result_from_GetLastError(GetLastError());
     }
@@ -59172,20 +59206,22 @@ static ma_result ma_default_vfs_tell__win32(ma_vfs* pVFS, ma_vfs_file file, ma_i
     LARGE_INTEGER liZero;
     LARGE_INTEGER liTell;
     BOOL result;
-#if (defined(_MSC_VER) && _MSC_VER <= 1200) || defined(__DMC__)
-    LONG tell;
-#endif
 
     (void)pVFS;
 
     liZero.QuadPart = 0;
 
-#if (defined(_MSC_VER) && _MSC_VER <= 1200) || defined(__DMC__)
-    result = SetFilePointer((HANDLE)file, (LONG)liZero.QuadPart, &tell, FILE_CURRENT);
-    liTell.QuadPart = tell;
-#else
-    result = SetFilePointerEx((HANDLE)file, liZero, &liTell, FILE_CURRENT);
-#endif
+    if (ma_SetFilePointerEx != NULL) {
+        result = ma_SetFilePointerEx((HANDLE)file, liZero, &liTell, FILE_CURRENT);
+    } else if (ma_SetFilePointer != NULL) {
+        LONG tell;
+
+        result = ma_SetFilePointer((HANDLE)file, (LONG)liZero.QuadPart, &tell, FILE_CURRENT);
+        liTell.QuadPart = tell;
+    } else {
+        return MA_NOT_IMPLEMENTED;
+    }
+
     if (result == 0) {
         return ma_result_from_GetLastError(GetLastError());
     }