--- /dev/null
+++ libmalloc/libmalloc-646.0.13/src/thresholds.h
@@ -0,0 +1,235 @@
+/*
+ * Copyright (c) 2015 Apple Inc. All rights reserved.
+ *
+ * @APPLE_LICENSE_HEADER_START@
+ *
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this
+ * file.
+ *
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ *
+ * @APPLE_LICENSE_HEADER_END@
+ */
+
+#ifndef __THRESHOLDS_H
+#define __THRESHOLDS_H
+
+/*
+ * The actual threshold boundaries between allocators. These boundaries are
+ * where the next allocator will take over and they are *inclusive* of the
+ * limit value.  That is, a TINY limit of X implies that an X-byte
+ * allocation will come from TINY.
+ *
+ * The LARGE allocator cuts in at whatever the last boundary limit is. So, when
+ * the medium allocator is compiled out, or not engaged, then large starts at
+ * the limit of SMALL.
+ */
+#if MALLOC_TARGET_64BIT
+#define TINY_LIMIT_THRESHOLD (1008)
+#else // MALLOC_TARGET_64BIT
+#define TINY_LIMIT_THRESHOLD (496)
+#endif // MALLOC_TARGET_64BIT
+
+#if MALLOC_TARGET_IOS
+#define SMALL_LIMIT_THRESHOLD (15 * 1024)
+#else // MALLOC_TARGET_IOS
+#define SMALL_LIMIT_THRESHOLD (32 * 1024)
+#endif // MALLOC_TARGET_IOS
+#define MEDIUM_LIMIT_THRESHOLD (8 * 1024 * 1024)
+
+/*
+ * Tiny region size definitions; these are split into quanta of 16 bytes,
+ * 64504 blocks is the magical value of how many quanta we can fit in a 1mb
+ * region including the region trailer and metadata.
+ *
+ * XXX Although much of the tiny implementation handles (msize == 0) values as
+ * 65536, this configuration of NUM_TINY_BLOCKS makes that value impossible to
+ * reach.  That should be cleaned up, as it would greatly simplify msize
+ * handling.
+ */
+#define SHIFT_TINY_QUANTUM 4ull
+#define SHIFT_TINY_CEIL_BLOCKS 16 // ceil(log2(NUM_TINY_BLOCKS))
+#define TINY_QUANTUM (1 << SHIFT_TINY_QUANTUM)
+#define NUM_TINY_BLOCKS 64504
+#define NUM_TINY_CEIL_BLOCKS (1 << SHIFT_TINY_CEIL_BLOCKS)
+#define NUM_TINY_SLOTS (TINY_LIMIT_THRESHOLD >> SHIFT_TINY_QUANTUM)
+
+#if MALLOC_TARGET_64BIT
+#define TINY_BITMAP_RANGE_LIMIT 63
+#else
+#define TINY_BITMAP_RANGE_LIMIT 31
+#endif
+
+/*
+ * Small region size definitions.
+ *
+ * We can only represent up to 1<<15 for msize; but we choose to stay
+ * even below that to avoid the convention msize=0 => msize = (1<<15)
+ */
+#define SHIFT_SMALL_QUANTUM (SHIFT_TINY_QUANTUM + 5) // 9
+#define SHIFT_SMALL_CEIL_BLOCKS 14 // ceil(log2(NUM_SMALL_BLOCKs))
+#define SMALL_QUANTUM (1 << SHIFT_SMALL_QUANTUM) // 512 bytes
+#define SMALL_BLOCKS_ALIGN (SHIFT_SMALL_CEIL_BLOCKS + SHIFT_SMALL_QUANTUM) // 23
+#define NUM_SMALL_BLOCKS 16319
+#define NUM_SMALL_CEIL_BLOCKS (1 << SHIFT_SMALL_CEIL_BLOCKS)
+#define NUM_SMALL_SLOTS (SMALL_LIMIT_THRESHOLD >> SHIFT_SMALL_QUANTUM)
+
+/*
+ * Medium region size definitions.
+ *
+ * We can only represent up to 1<<15 for msize; but we choose to stay
+ * even below that to avoid the convention msize=0 => msize = (1<<15)
+ */
+#define SHIFT_MEDIUM_QUANTUM (SHIFT_SMALL_QUANTUM + 6) // 15
+#define SHIFT_MEDIUM_CEIL_BLOCKS 12ull // ceil(log2(NUM_MEDIUM_BLOCKS))
+#define MEDIUM_QUANTUM ((uint64_t)(1 << SHIFT_MEDIUM_QUANTUM)) // 32kbytes
+#define MEDIUM_BLOCKS_ALIGN (SHIFT_MEDIUM_CEIL_BLOCKS + SHIFT_MEDIUM_QUANTUM) // 27
+#define NUM_MEDIUM_BLOCKS 4095
+#define NUM_MEDIUM_CEIL_BLOCKS (1ull << SHIFT_MEDIUM_CEIL_BLOCKS)
+#define NUM_MEDIUM_SLOTS (MEDIUM_LIMIT_THRESHOLD >> SHIFT_MEDIUM_QUANTUM)
+#define MEDIUM_ACTIVATION_THRESHOLD (32ull * 1024 * 1024 * 1024)
+#define MEDIUM_CONDITIONAL_MADVISE_LIMIT (2 * 1024 * 1024)
+#define MEDIUM_MADVISE_SHIFT 4
+#define MEDIUM_MADVISE_MIN ((3 * 1024 * 1024) / 2) // 1.5 megabytes
+#define MEDIUM_MADVISE_DRAM_SCALE_DIVISOR (128ull * 1024 * 1024 * 1024) // 128GB
+
+
+/*
+ * When performing a realloc() that must fallback to creating a new allocation
+ * and copying the previous contents to the new allocation, vm_copy is used if
+ * the allocation is greater than a given size.
+ *
+ * This threshold must be set such that all eligible allocations would have
+ * come from a page-sized, page-aligned allocator (so, medium or large).
+ *
+ * Note: iOS disables this threshold because the VM forces non-sharing from
+ * malloc-tagged allocations.
+ */
+#define VM_COPY_THRESHOLD (2 * 1024 * 1024)
+
+/*
+ * <rdar://problem/6881926&27190324> Extremely old versions of Microsoft Word
+ * (and, subsequently, versions of Adobe apps) required the Leopard behaviour
+ * where LARGE allocations were zero-filled prior to returning them to the
+ * caller.
+ *
+ * We've always used LARGE_THRESHOLD to denote this boundary but as we keep
+ * moving it around it's better to fix it at the point it was originally.
+ */
+#define LEGACY_ZEROING_THRESHOLD (127 * 1024)
+
+/*
+ * Large entry cache (death row) sizes. The large cache is bounded with
+ * an overall top limit size, each entry is allowed a given slice of
+ * that limit.
+ */
+
+#define LARGE_CACHE_EXPANDED_THRESHOLD (32ull * 1024 * 1024 * 1024)
+
+#if MALLOC_TARGET_64BIT
+#define LARGE_ENTRY_CACHE_SIZE_HIGH 64
+#define LARGE_ENTRY_SIZE_ENTRY_LIMIT_HIGH (512 * 1024 * 1024)
+// lowmem config
+#define LARGE_ENTRY_CACHE_SIZE_LOW 16
+#define LARGE_ENTRY_SIZE_ENTRY_LIMIT_LOW (128 * 1024 * 1024)
+#else // MALLOC_TARGET_64BIT
+#define LARGE_ENTRY_CACHE_SIZE_HIGH 8
+#define LARGE_ENTRY_SIZE_ENTRY_LIMIT_HIGH (32 * 1024 * 1024)
+// lowmem config same as "highmem"
+#define LARGE_ENTRY_CACHE_SIZE_LOW LARGE_ENTRY_CACHE_SIZE_HIGH
+#define LARGE_ENTRY_SIZE_ENTRY_LIMIT_LOW LARGE_ENTRY_SIZE_ENTRY_LIMIT_HIGH
+#endif // MALLOC_TARGET_64BIT
+
+/*
+ * Large entry cache (death row) "flotsam" limits. Until the large cache
+ * contains at least "high" bytes, the cache is not cleaned under memory
+ * pressure. After that, memory pressure notifications cause cache cleaning
+ * until the large cache drops below the "low" limit.
+ */
+#define SZONE_FLOTSAM_THRESHOLD_LOW (1024 * 512)
+#define SZONE_FLOTSAM_THRESHOLD_HIGH (1024 * 1024)
+
+/*
+ * The magazine freelist array must be large enough to accomodate the allocation
+ * granularity of the tiny, small and medium allocators. In addition, the last
+ * slot in the list is special and reserved for coalesced regions bigger than
+ * the overall max allocation size of the allocator.
+ */
+#define MAGAZINE_FREELIST_SLOTS (NUM_MEDIUM_SLOTS + 1)
+#define MAGAZINE_FREELIST_BITMAP_WORDS ((MAGAZINE_FREELIST_SLOTS + 31) >> 5)
+
+/*
+ * Density threshold used in determining the level of emptiness before
+ * moving regions to the recirc depot.
+ */
+#define DENSITY_THRESHOLD(a) \
+	((a) - ((a) >> 2)) // "Emptiness" f = 0.25, so "Density" is (1 - f)*a. Generally: ((a) - ((a) >> -log2(f)))
+
+/*
+ * Minimum number of regions to retain in a recirc depot.
+ */
+#define DEFAULT_RECIRC_RETAINED_REGIONS 2
+
+/* Sanity checks. */
+
+// Tiny performs an ffsl of a uint64_t in order to determine how big an
+// allocation is. Therefore, the total allocation size of small cannot exceed
+// 63-bits worth of 16-byte quanta (64-bits but minus one for the start of the
+// allocation itself).
+MALLOC_STATIC_ASSERT((TINY_LIMIT_THRESHOLD / TINY_QUANTUM) <= TINY_BITMAP_RANGE_LIMIT,
+		"TINY_LIMIT_THRESHOLD cannot exceed TINY_BITMAP_RANGE_LIMIT-bits worth of metadata");
+
+// Check that the given threshold limits are a round multiple of their
+// allocator's quantum size.
+MALLOC_STATIC_ASSERT((TINY_LIMIT_THRESHOLD % TINY_QUANTUM) == 0,
+		"TINY_LIMIT_THRESHOLD must be a multiple of TINY_QUANTUM");
+
+MALLOC_STATIC_ASSERT((SMALL_LIMIT_THRESHOLD % SMALL_QUANTUM) == 0,
+		"SMALL_LIMIT_THRESHOLD must be a multiple of SMALL_QUANTUM");
+
+MALLOC_STATIC_ASSERT((MEDIUM_LIMIT_THRESHOLD % MEDIUM_QUANTUM) == 0,
+		"MEDIUM_LIMIT_THRESHOLD must be a multiple of MEDIUM_QUANTUM");
+
+// All the "slot" counts are calculated as a shift of thresholds now but
+// in-case someone decides to try hand-crafted values, make sure they adhere to
+// the basic expectation that slot count must account for all valid sizes of
+// allocations.
+MALLOC_STATIC_ASSERT(NUM_TINY_SLOTS >= TINY_LIMIT_THRESHOLD >> SHIFT_TINY_QUANTUM,
+		"NUM_TINY_SLOTS must allow a free list for every valid TINY allocation");
+
+MALLOC_STATIC_ASSERT(NUM_SMALL_SLOTS >= SMALL_LIMIT_THRESHOLD >> SHIFT_SMALL_QUANTUM,
+		"NUM_SMALL_SLOTS must allow a free list for every valid SMALL allocation");
+
+MALLOC_STATIC_ASSERT(NUM_MEDIUM_SLOTS >= MEDIUM_LIMIT_THRESHOLD >> SHIFT_MEDIUM_QUANTUM,
+		"NUM_MEDIUM_SLOTS must allow a free list for every valid MEDIUM allocation");
+
+// MAGAZINE_FREELIST_SLOTS cannot be dynamically selected by the MAX() of all
+// three allocators, so it must match (at least) the maxmium slot count of the
+// allocator with the largest range.
+//
+// Additionally, each allocator assumes that there is one additional free-list
+// slot above their maximum allocation size. This allows each allocator to
+// store an unordered list of maximally-sized free list entries.
+MALLOC_STATIC_ASSERT(NUM_TINY_SLOTS < MAGAZINE_FREELIST_SLOTS,
+		"NUM_TINY_SLOTS must be less than MAGAZINE_FREELIST_SLOTS");
+
+MALLOC_STATIC_ASSERT(NUM_SMALL_SLOTS < MAGAZINE_FREELIST_SLOTS,
+		"NUM_SMALL_SLOTS must be less than MAGAZINE_FREELIST_SLOTS");
+
+MALLOC_STATIC_ASSERT(NUM_MEDIUM_SLOTS < MAGAZINE_FREELIST_SLOTS,
+		"NUM_MEDIUM_SLOTS must be less than MAGAZINE_FREELIST_SLOTS");
+
+MALLOC_STATIC_ASSERT(VM_COPY_THRESHOLD >= SMALL_LIMIT_THRESHOLD,
+		"VM_COPY_THRESHOLD must be larger than SMALL_LIMIT_THRESHOLD");
+
+#endif // __THRESHOLDS_H