Change SkMemory to the more accurately named SkMalloc.

Change-Id: I6b08a74234b99bac866bad71014b94f7ec2d4bc8
Reviewed-on: https://skia-review.googlesource.com/10188
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>

1 files changed, 84 insertions, 0 deletions

diff --git a/include/private/SkMalloc.h b/include/private/SkMalloc.h
new file mode 100644
index 0000000000..58e11f657c
--- /dev/null
+++ b/include/private/SkMalloc.h
@@ -0,0 +1,84 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkMalloc_DEFINED
+#define SkMalloc_DEFINED
+
+#include <cstddef>
+#include <cstring>
+
+#include "SkPreConfig.h"
+
+/*
+    memory wrappers to be implemented by the porting layer (platform)
+*/
+
+enum {
+    SK_MALLOC_TEMP  = 0x01, //!< hint to sk_malloc that the requested memory will be freed in the scope of the stack frame
+    SK_MALLOC_THROW = 0x02  //!< instructs sk_malloc to call sk_throw if the memory cannot be allocated.
+};
+/** Return a block of memory (at least 4-byte aligned) of at least the
+    specified size. If the requested memory cannot be returned, either
+    return null (if SK_MALLOC_TEMP bit is clear) or throw an exception
+    (if SK_MALLOC_TEMP bit is set). To free the memory, call sk_free().
+*/
+SK_API extern void* sk_malloc_flags(size_t size, unsigned flags);
+/** Same as sk_malloc(), but hard coded to pass SK_MALLOC_THROW as the flag
+*/
+SK_API extern void* sk_malloc_throw(size_t size);
+/** Same as standard realloc(), but this one never returns null on failure. It will throw
+    an exception if it fails.
+*/
+SK_API extern void* sk_realloc_throw(void* buffer, size_t size);
+/** Free memory returned by sk_malloc(). It is safe to pass null.
+*/
+SK_API extern void sk_free(void*);
+
+/** Much like calloc: returns a pointer to at least size zero bytes, or NULL on failure.
+ */
+SK_API extern void* sk_calloc(size_t size);
+
+/** Same as sk_calloc, but throws an exception instead of returning NULL on failure.
+ */
+SK_API extern void* sk_calloc_throw(size_t size);
+
+/** Called internally if we run out of memory. The platform implementation must
+    not return, but should either throw an exception or otherwise exit.
+*/
+SK_API extern void sk_out_of_memory(void);
+
+// bzero is safer than memset, but we can't rely on it, so... sk_bzero()
+static inline void sk_bzero(void* buffer, size_t size) {
+    // Please c.f. sk_careful_memcpy.  It's undefined behavior to call memset(null, 0, 0).
+    if (size) {
+        memset(buffer, 0, size);
+    }
+}
+
+/**
+ *  sk_careful_memcpy() is just like memcpy(), but guards against undefined behavior.
+ *
+ * It is undefined behavior to call memcpy() with null dst or src, even if len is 0.
+ * If an optimizer is "smart" enough, it can exploit this to do unexpected things.
+ *     memcpy(dst, src, 0);
+ *     if (src) {
+ *         printf("%x\n", *src);
+ *     }
+ * In this code the compiler can assume src is not null and omit the if (src) {...} check,
+ * unconditionally running the printf, crashing the program if src really is null.
+ * Of the compilers we pay attention to only GCC performs this optimization in practice.
+ */
+static inline void* sk_careful_memcpy(void* dst, const void* src, size_t len) {
+    // When we pass >0 len we had better already be passing valid pointers.
+    // So we just need to skip calling memcpy when len == 0.
+    if (len) {
+        memcpy(dst,src,len);
+    }
+    return dst;
+}
+
+#endif  // SkMalloc_DEFINED