Merge commit 'e4bec39a139363d1ee4cf3fb15a3fe4499215e77' into 4.6

2 files changed, 61 insertions, 0 deletions

diff --git a/src/corelib/global/qglobal.h b/src/corelib/global/qglobal.h
index 5ee1815..cbb8fda 100644
--- a/src/corelib/global/qglobal.h
+++ b/src/corelib/global/qglobal.h
@@ -2065,6 +2065,9 @@ Q_DECLARE_TYPEINFO(long double, Q_PRIMITIVE_TYPE);
 Q_CORE_EXPORT void *qMalloc(size_t size);
 Q_CORE_EXPORT void qFree(void *ptr);
 Q_CORE_EXPORT void *qRealloc(void *ptr, size_t size);
+Q_CORE_EXPORT void *qMallocAligned(size_t size, size_t alignment);
+Q_CORE_EXPORT void *qReallocAligned(void *ptr, size_t size, size_t oldsize, size_t alignment);
+Q_CORE_EXPORT void qFreeAligned(void *ptr);
 Q_CORE_EXPORT void *qMemCopy(void *dest, const void *src, size_t n);
 Q_CORE_EXPORT void *qMemSet(void *dest, int c, size_t n);
 
diff --git a/src/corelib/global/qmalloc.cpp b/src/corelib/global/qmalloc.cpp
index a9f103c..4aab1bd 100644
--- a/src/corelib/global/qmalloc.cpp
+++ b/src/corelib/global/qmalloc.cpp
@@ -65,4 +65,62 @@ void *qRealloc(void *ptr, size_t size)
     return ::realloc(ptr, size);
 }
 
+void *qMallocAligned(size_t size, size_t alignment)
+{
+    return qReallocAligned(0, size, 0, alignment);
+}
+
+void *qReallocAligned(void *oldptr, size_t newsize, size_t oldsize, size_t alignment)
+{
+    // fake an aligned allocation
+    Q_UNUSED(oldsize);
+
+    void *actualptr = oldptr ? static_cast<void **>(oldptr)[-1] : 0;
+    if (alignment <= sizeof(void*)) {
+        // special, fast case
+        void **newptr = static_cast<void **>(qRealloc(actualptr, newsize + sizeof(void*)));
+        if (!newptr)
+            return 0;
+        if (newptr == actualptr) {
+            // realloc succeeded without reallocating
+            return oldptr;
+        }
+
+        *newptr = newptr;
+        return newptr + 1;
+    }
+
+    union { void *ptr; void **pptr; quintptr n; } real, faked;
+
+    // qMalloc returns pointers aligned at least at sizeof(size_t) boundaries
+    // but usually more (8- or 16-byte boundaries).
+    // So we overallocate by alignment-sizeof(size_t) bytes, so we're guaranteed to find a
+    // somewhere within the first alignment-sizeof(size_t) that is properly aligned.
+
+    // However, we need to store the actual pointer, so we need to allocate actually size +
+    // alignment anyway.
+
+    real.ptr = qRealloc(actualptr, newsize + alignment);
+    if (!real.ptr)
+        return 0;
+
+    faked.n = real.n + alignment;
+    faked.n &= ~(alignment - 1);
+
+    // now save the value of the real pointer at faked-sizeof(void*)
+    // by construction, alignment > sizeof(void*) and is a power of 2, so
+    // faked-sizeof(void*) is properly aligned for a pointer
+    faked.pptr[-1] = real.ptr;
+
+    return faked.ptr;
+}
+
+void qFreeAligned(void *ptr)
+{
+    if (!ptr)
+        return;
+    void **ptr2 = static_cast<void **>(ptr);
+    free(ptr2[-1]);
+}
+
 QT_END_NAMESPACE