Refactoring: move GUID operations out of Joystick

- SDL_JoystickGUID -> SDL_GUID (though we retain a type alias)
- Operations for GUID <-> String ops are now in
  src/SDL_guid.c and include/SDL_guid.h
- The corresponding Joystick operations delegate to SDL_guid.c
- Added test/testguid.c

src/SDL_guid.c

@@ -0,0 +1,91 @@
+/*
+  Simple DirectMedia Layer
+  Copyright (C) 1997-2022 Sam Lantinga <slouken@libsdl.org>
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.
+*/
+#include "SDL_internal.h"
+
+
+#include "SDL_guid.h"
+
+/* convert the guid to a printable string */
+void SDL_GUIDToString(SDL_GUID guid, char *pszGUID, int cbGUID)
+{
+    static const char k_rgchHexToASCII[] = "0123456789abcdef";
+    int i;
+
+    if ((pszGUID == NULL) || (cbGUID <= 0)) {
+        return;
+    }
+
+    for (i = 0; i < sizeof(guid.data) && i < (cbGUID-1)/2; i++) {
+        /* each input byte writes 2 ascii chars, and might write a null byte. */
+        /* If we don't have room for next input byte, stop */
+        unsigned char c = guid.data[i];
+
+        *pszGUID++ = k_rgchHexToASCII[c >> 4];
+        *pszGUID++ = k_rgchHexToASCII[c & 0x0F];
+    }
+    *pszGUID = '\0';
+}
+
+/*-----------------------------------------------------------------------------
+ * Purpose: Returns the 4 bit nibble for a hex character
+ * Input  : c -
+ * Output : unsigned char
+ *-----------------------------------------------------------------------------*/
+static unsigned char nibble(unsigned char c)
+{
+    if ((c >= '0') && (c <= '9')) {
+        return (c - '0');
+    }
+
+    if ((c >= 'A') && (c <= 'F')) {
+        return (c - 'A' + 0x0a);
+    }
+
+    if ((c >= 'a') && (c <= 'f')) {
+        return (c - 'a' + 0x0a);
+    }
+
+    /* received an invalid character, and no real way to return an error */
+    /* AssertMsg1(false, "Q_nibble invalid hex character '%c' ", c); */
+    return 0;
+}
+
+/* convert the string version of a guid to the struct */
+SDL_GUID SDL_GUIDFromString(const char *pchGUID)
+{
+    SDL_GUID guid;
+    int maxoutputbytes= sizeof(guid);
+    size_t len = SDL_strlen(pchGUID);
+    Uint8 *p;
+    size_t i;
+
+    /* Make sure it's even */
+    len = (len) & ~0x1;
+
+    SDL_memset(&guid, 0x00, sizeof(guid));
+
+    p = (Uint8 *)&guid;
+    for (i = 0; (i < len) && ((p - (Uint8 *)&guid) < maxoutputbytes); i+=2, p++) {
+        *p = (nibble((unsigned char)pchGUID[i]) << 4) | nibble((unsigned char)pchGUID[i+1]);
+    }
+
+    return guid;
+}

src/dynapi/SDL2.exports

@@ -843,3 +843,5 @@
 ++'_SDL_JoystickAttachVirtualEx'.'SDL2.dll'.'SDL_JoystickAttachVirtualEx'
 ++'_SDL_GameControllerGetFirmwareVersion'.'SDL2.dll'.'SDL_GameControllerGetFirmwareVersion'
 ++'_SDL_JoystickGetFirmwareVersion'.'SDL2.dll'.'SDL_JoystickGetFirmwareVersion'
+++'_SDL_GUIDToString'.'SDL2.dll'.'SDL_GUIDToString'
+++'_SDL_GUIDFromString'.'SDL2.dll'.'SDL_GUIDFromString'

src/dynapi/SDL_dynapi_overrides.h

@@ -869,3 +869,5 @@
 #define SDL_JoystickAttachVirtualEx SDL_JoystickAttachVirtualEx_REAL
 #define SDL_GameControllerGetFirmwareVersion SDL_GameControllerGetFirmwareVersion_REAL
 #define SDL_JoystickGetFirmwareVersion SDL_JoystickGetFirmwareVersion_REAL
+#define SDL_GUIDToString SDL_GUIDToString_REAL
+#define SDL_GUIDFromString SDL_GUIDFromString_REAL

src/dynapi/SDL_dynapi_procs.h

@@ -944,3 +944,5 @@ SDL_DYNAPI_PROC(const char*,SDL_JoystickPath,(SDL_Joystick *a),(a),return)
 SDL_DYNAPI_PROC(int,SDL_JoystickAttachVirtualEx,(const SDL_VirtualJoystickDesc *a),(a),return)
 SDL_DYNAPI_PROC(Uint16,SDL_GameControllerGetFirmwareVersion,(SDL_GameController *a),(a),return)
 SDL_DYNAPI_PROC(Uint16,SDL_JoystickGetFirmwareVersion,(SDL_Joystick *a),(a),return)
+SDL_DYNAPI_PROC(void,SDL_GUIDToString,(SDL_GUID a, char *b, int c),(a,b,c),)
+SDL_DYNAPI_PROC(SDL_GUID,SDL_GUIDFromString,(const char *a),(a),return)

src/joystick/SDL_joystick.c

@@ -2735,68 +2735,13 @@ SDL_JoystickType SDL_JoystickGetType(SDL_Joystick *joystick)
 /* convert the guid to a printable string */
 void SDL_JoystickGetGUIDString(SDL_JoystickGUID guid, char *pszGUID, int cbGUID)
 {
-    static const char k_rgchHexToASCII[] = "0123456789abcdef";
-    int i;
-
-    if ((pszGUID == NULL) || (cbGUID <= 0)) {
-        return;
-    }
-
-    for (i = 0; i < sizeof(guid.data) && i < (cbGUID-1)/2; i++) {
-        /* each input byte writes 2 ascii chars, and might write a null byte. */
-        /* If we don't have room for next input byte, stop */
-        unsigned char c = guid.data[i];
-
-        *pszGUID++ = k_rgchHexToASCII[c >> 4];
-        *pszGUID++ = k_rgchHexToASCII[c & 0x0F];
-    }
-    *pszGUID = '\0';
-}
-
-/*-----------------------------------------------------------------------------
- * Purpose: Returns the 4 bit nibble for a hex character
- * Input  : c -
- * Output : unsigned char
- *-----------------------------------------------------------------------------*/
-static unsigned char nibble(unsigned char c)
-{
-    if ((c >= '0') && (c <= '9')) {
-        return (c - '0');
-    }
-
-    if ((c >= 'A') && (c <= 'F')) {
-        return (c - 'A' + 0x0a);
-    }
-
-    if ((c >= 'a') && (c <= 'f')) {
-        return (c - 'a' + 0x0a);
-    }
-
-    /* received an invalid character, and no real way to return an error */
-    /* AssertMsg1(false, "Q_nibble invalid hex character '%c' ", c); */
-    return 0;
+    SDL_GUIDToString(guid, pszGUID, cbGUID);
 }
 
 /* convert the string version of a joystick guid to the struct */
 SDL_JoystickGUID SDL_JoystickGetGUIDFromString(const char *pchGUID)
 {
-    SDL_JoystickGUID guid;
-    int maxoutputbytes= sizeof(guid);
-    size_t len = SDL_strlen(pchGUID);
-    Uint8 *p;
-    size_t i;
-
-    /* Make sure it's even */
-    len = (len) & ~0x1;
-
-    SDL_memset(&guid, 0x00, sizeof(guid));
-
-    p = (Uint8 *)&guid;
-    for (i = 0; (i < len) && ((p - (Uint8 *)&guid) < maxoutputbytes); i+=2, p++) {
-        *p = (nibble((unsigned char)pchGUID[i]) << 4) | nibble((unsigned char)pchGUID[i+1]);
-    }
-
-    return guid;
+    return SDL_GUIDFromString(pchGUID);
 }
 
 /* update the power level for this joystick */