Xi: add XIPropToInt() auxiliary function.

Converts an XIPropertyValuePtr to an integer, provided that type and format is
right.

Code originally written by Simon Thum.

Signed-off-by: Peter Hutterer <peter.hutterer@redhat.com>

Xi/xiproperty.c

@@ -32,6 +32,7 @@
 #include "dix.h"
 #include "inputstr.h"
 #include <X11/extensions/XI.h>
+#include <X11/Xatom.h>
 #include <X11/extensions/XIproto.h>
 #include "exglobals.h"
 #include "exevents.h"
@@ -70,6 +71,73 @@ XIGetKnownProperty(char *name)
     return 0;
 }
 
+/**
+ * Convert the given property's value(s) into @nelem_return integer values and
+ * store them in @buf_return. If @nelem_return is larger than the number of
+ * values in the property, @nelem_return is set to the number of values in the
+ * property.
+ *
+ * If *@buf_return is NULL and @nelem_return is 0, memory is allocated
+ * automatically and must be freed by the caller.
+ *
+ * Possible return codes.
+ * Success ... No error.
+ * BadMatch ... Wrong atom type, atom is not XA_INTEGER
+ * BadAlloc ... NULL passed as buffer and allocation failed.
+ * BadLength ... @buff is NULL but @nelem_return is non-zero.
+ *
+ * @param val The property value
+ * @param nelem_return The maximum number of elements to return.
+ * @param buf_return Pointer to an array of at least @nelem_return values.
+ * @return Success or the error code if an error occured.
+ */
+_X_EXPORT int
+XIPropToInt(XIPropertyValuePtr val, int *nelem_return, int **buf_return)
+{
+    int i;
+    int *buf;
+
+    if (val->type != XA_INTEGER)
+        return BadMatch;
+    if (!*buf_return && *nelem_return)
+        return BadLength;
+
+    switch(val->format)
+    {
+        case 8:
+        case 16:
+        case 32:
+            break;
+        default:
+            return BadValue;
+    }
+
+    buf = *buf_return;
+
+    if (!buf && !(*nelem_return))
+    {
+        buf = xcalloc(val->size, sizeof(int));
+        if (!buf)
+            return BadAlloc;
+        *buf_return = buf;
+        *nelem_return = val->size;
+    } else if (val->size < *nelem_return)
+        *nelem_return = val->size;
+
+    for (i = 0; i < val->size && i < *nelem_return; i++)
+    {
+        switch(val->format)
+        {
+            case 8:  buf[i] = ((CARD8*)val->data)[i]; break;
+            case 16: buf[i] = ((CARD16*)val->data)[i]; break;
+            case 32: buf[i] = ((CARD32*)val->data)[i]; break;
+        }
+    }
+
+    return Success;
+}
+
+
 /**
  * Init those properties that are allocated by the server and most likely used
  * by the DIX or the DDX.

include/exevents.h

@@ -251,4 +251,10 @@ extern _X_EXPORT Atom XIGetKnownProperty(
 
 extern _X_EXPORT DeviceIntPtr XIGetDevice(xEvent *ev);
 
+extern _X_EXPORT int XIPropToInt(
+        XIPropertyValuePtr val,
+        int *nelem_return,
+        int **buf_return
+);
+
 #endif /* EXEVENTS_H */