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      1 // Copyright (c) 2011 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 "net/disk_cache/blockfile/trace.h"
      6 
      7 #include <stdio.h>
      8 #if defined(OS_WIN)
      9 #include <windows.h>
     10 #endif
     11 
     12 #include "base/lazy_instance.h"
     13 #include "base/logging.h"
     14 #include "base/synchronization/lock.h"
     15 #include "net/disk_cache/blockfile/stress_support.h"
     16 
     17 // Change this value to 1 to enable tracing on a release build. By default,
     18 // tracing is enabled only on debug builds.
     19 #define ENABLE_TRACING 0
     20 
     21 #ifndef NDEBUG
     22 #undef ENABLE_TRACING
     23 #define ENABLE_TRACING 1
     24 #endif
     25 
     26 namespace {
     27 
     28 const int kEntrySize = 12 * sizeof(size_t);
     29 #if defined(NET_BUILD_STRESS_CACHE)
     30 const int kNumberOfEntries = 500000;
     31 #else
     32 const int kNumberOfEntries = 5000;  // 240 KB on 32bit, 480 KB on 64bit
     33 #endif
     34 
     35 bool s_trace_enabled = false;
     36 base::LazyInstance<base::Lock>::Leaky s_lock = LAZY_INSTANCE_INITIALIZER;
     37 
     38 struct TraceBuffer {
     39   int num_traces;
     40   int current;
     41   char buffer[kNumberOfEntries][kEntrySize];
     42 };
     43 
     44 #if ENABLE_TRACING
     45 void DebugOutput(const char* msg) {
     46 #if defined(OS_WIN)
     47   OutputDebugStringA(msg);
     48 #else
     49   NOTIMPLEMENTED();
     50 #endif
     51 }
     52 #endif  // ENABLE_TRACING
     53 
     54 }  // namespace
     55 
     56 namespace disk_cache {
     57 
     58 // s_trace_buffer and s_trace_object are not singletons because I want the
     59 // buffer to be destroyed and re-created when the last user goes away, and it
     60 // must be straightforward to access the buffer from the debugger.
     61 static TraceObject* s_trace_object = NULL;
     62 
     63 // Static.
     64 TraceObject* TraceObject::GetTraceObject() {
     65   base::AutoLock lock(s_lock.Get());
     66 
     67   if (s_trace_object)
     68     return s_trace_object;
     69 
     70   s_trace_object = new TraceObject();
     71   return s_trace_object;
     72 }
     73 
     74 TraceObject::TraceObject() {
     75   InitTrace();
     76 }
     77 
     78 TraceObject::~TraceObject() {
     79   DestroyTrace();
     80 }
     81 
     82 void TraceObject::EnableTracing(bool enable) {
     83   base::AutoLock lock(s_lock.Get());
     84   s_trace_enabled = enable;
     85 }
     86 
     87 #if ENABLE_TRACING
     88 
     89 static TraceBuffer* s_trace_buffer = NULL;
     90 
     91 void InitTrace(void) {
     92   s_trace_enabled = true;
     93   if (s_trace_buffer)
     94     return;
     95 
     96   s_trace_buffer = new TraceBuffer;
     97   memset(s_trace_buffer, 0, sizeof(*s_trace_buffer));
     98 }
     99 
    100 void DestroyTrace(void) {
    101   base::AutoLock lock(s_lock.Get());
    102 
    103   delete s_trace_buffer;
    104   s_trace_buffer = NULL;
    105   s_trace_object = NULL;
    106 }
    107 
    108 void Trace(const char* format, ...) {
    109   if (!s_trace_buffer || !s_trace_enabled)
    110     return;
    111 
    112   va_list ap;
    113   va_start(ap, format);
    114   char line[kEntrySize + 2];
    115 
    116 #if defined(OS_WIN)
    117   vsprintf_s(line, format, ap);
    118 #else
    119   vsnprintf(line, kEntrySize, format, ap);
    120 #endif
    121 
    122 #if defined(DISK_CACHE_TRACE_TO_LOG)
    123   line[kEntrySize] = '\0';
    124   LOG(INFO) << line;
    125 #endif
    126 
    127   va_end(ap);
    128 
    129   {
    130     base::AutoLock lock(s_lock.Get());
    131     if (!s_trace_buffer || !s_trace_enabled)
    132       return;
    133 
    134     memcpy(s_trace_buffer->buffer[s_trace_buffer->current], line, kEntrySize);
    135 
    136     s_trace_buffer->num_traces++;
    137     s_trace_buffer->current++;
    138     if (s_trace_buffer->current == kNumberOfEntries)
    139       s_trace_buffer->current = 0;
    140   }
    141 }
    142 
    143 // Writes the last num_traces to the debugger output.
    144 void DumpTrace(int num_traces) {
    145   DCHECK(s_trace_buffer);
    146   DebugOutput("Last traces:\n");
    147 
    148   if (num_traces > kNumberOfEntries || num_traces < 0)
    149     num_traces = kNumberOfEntries;
    150 
    151   if (s_trace_buffer->num_traces) {
    152     char line[kEntrySize + 2];
    153 
    154     int current = s_trace_buffer->current - num_traces;
    155     if (current < 0)
    156       current += kNumberOfEntries;
    157 
    158     for (int i = 0; i < num_traces; i++) {
    159       memcpy(line, s_trace_buffer->buffer[current], kEntrySize);
    160       line[kEntrySize] = '\0';
    161       size_t length = strlen(line);
    162       if (length) {
    163         line[length] = '\n';
    164         line[length + 1] = '\0';
    165         DebugOutput(line);
    166       }
    167 
    168       current++;
    169       if (current ==  kNumberOfEntries)
    170         current = 0;
    171     }
    172   }
    173 
    174   DebugOutput("End of Traces\n");
    175 }
    176 
    177 #else  // ENABLE_TRACING
    178 
    179 void InitTrace(void) {
    180   return;
    181 }
    182 
    183 void DestroyTrace(void) {
    184   s_trace_object = NULL;
    185 }
    186 
    187 void Trace(const char* format, ...) {
    188 }
    189 
    190 #endif  // ENABLE_TRACING
    191 
    192 }  // namespace disk_cache
    193