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1 // Copyright 2015 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #include "base/trace_event/heap_profiler_allocation_context.h"
6 
7 #include <cstring>
8 
9 #include "base/hash.h"
10 #include "base/macros.h"
11 
12 namespace base {
13 namespace trace_event {
14 
operator <(const StackFrame & lhs,const StackFrame & rhs)15 bool operator < (const StackFrame& lhs, const StackFrame& rhs) {
16   return lhs.value < rhs.value;
17 }
18 
operator ==(const StackFrame & lhs,const StackFrame & rhs)19 bool operator == (const StackFrame& lhs, const StackFrame& rhs) {
20   return lhs.value == rhs.value;
21 }
22 
operator !=(const StackFrame & lhs,const StackFrame & rhs)23 bool operator != (const StackFrame& lhs, const StackFrame& rhs) {
24   return !(lhs.value == rhs.value);
25 }
26 
Backtrace()27 Backtrace::Backtrace(): frame_count(0) {}
28 
operator ==(const Backtrace & lhs,const Backtrace & rhs)29 bool operator==(const Backtrace& lhs, const Backtrace& rhs) {
30   if (lhs.frame_count != rhs.frame_count) return false;
31   return std::equal(lhs.frames, lhs.frames + lhs.frame_count, rhs.frames);
32 }
33 
operator !=(const Backtrace & lhs,const Backtrace & rhs)34 bool operator!=(const Backtrace& lhs, const Backtrace& rhs) {
35   return !(lhs == rhs);
36 }
37 
AllocationContext()38 AllocationContext::AllocationContext(): type_name(nullptr) {}
39 
AllocationContext(const Backtrace & backtrace,const char * type_name)40 AllocationContext::AllocationContext(const Backtrace& backtrace,
41                                      const char* type_name)
42   : backtrace(backtrace), type_name(type_name) {}
43 
operator ==(const AllocationContext & lhs,const AllocationContext & rhs)44 bool operator==(const AllocationContext& lhs, const AllocationContext& rhs) {
45   return (lhs.backtrace == rhs.backtrace) && (lhs.type_name == rhs.type_name);
46 }
47 
operator !=(const AllocationContext & lhs,const AllocationContext & rhs)48 bool operator!=(const AllocationContext& lhs, const AllocationContext& rhs) {
49   return !(lhs == rhs);
50 }
51 }  // namespace trace_event
52 }  // namespace base
53 
54 namespace BASE_HASH_NAMESPACE {
55 using base::trace_event::AllocationContext;
56 using base::trace_event::Backtrace;
57 using base::trace_event::StackFrame;
58 
operator ()(const StackFrame & frame) const59 size_t hash<StackFrame>::operator()(const StackFrame& frame) const {
60   return hash<const void*>()(frame.value);
61 }
62 
operator ()(const Backtrace & backtrace) const63 size_t hash<Backtrace>::operator()(const Backtrace& backtrace) const {
64   const void* values[Backtrace::kMaxFrameCount];
65   for (size_t i = 0; i != backtrace.frame_count; ++i) {
66     values[i] = backtrace.frames[i].value;
67   }
68   return base::SuperFastHash(
69       reinterpret_cast<const char*>(values),
70       static_cast<int>(backtrace.frame_count * sizeof(*values)));
71 }
72 
operator ()(const AllocationContext & ctx) const73 size_t hash<AllocationContext>::operator()(const AllocationContext& ctx) const {
74   size_t backtrace_hash = hash<Backtrace>()(ctx.backtrace);
75 
76   // Multiplicative hash from [Knuth 1998]. Works best if |size_t| is 32 bits,
77   // because the magic number is a prime very close to 2^32 / golden ratio, but
78   // will still redistribute keys bijectively on 64-bit architectures because
79   // the magic number is coprime to 2^64.
80   size_t type_hash = reinterpret_cast<size_t>(ctx.type_name) * 2654435761;
81 
82   // Multiply one side to break the commutativity of +. Multiplication with a
83   // number coprime to |numeric_limits<size_t>::max() + 1| is bijective so
84   // randomness is preserved.
85   return (backtrace_hash * 3) + type_hash;
86 }
87 
88 }  // BASE_HASH_NAMESPACE
89