Implement a dynamically growing memory log buffer with an upper limit.

test/cctest/test-log-utils.cc

+// Copyright 2006-2009 the V8 project authors. All rights reserved.
+//
+// Tests of logging utilities from log-utils.h
+
+#ifdef ENABLE_LOGGING_AND_PROFILING
+
+#include "v8.h"
+
+#include "log-utils.h"
+#include "cctest.h"
+
+using v8::internal::EmbeddedVector;
+using v8::internal::LogDynamicBuffer;
+using v8::internal::Vector;
+
+// Writes ref_buffer.length chars into dynabuf.

[Søren Thygesen Gjesse, 2009/05/27 12:00:40]

Please add to comment that this also actually fills the ref_buffer before
writing it to the dynabuf.

[Mikhail Naganov, 2009/05/28 07:05:35]

Done.

+// The data written is a sequence of two-digit hex numbers: '0001020304...'.
+static void WriteData(LogDynamicBuffer* dynabuf, Vector<char>* ref_buffer) {
+  static const char kHex[] = "0123456789ABCDEF";
+  CHECK_GT(ref_buffer->length(), 0);
+  CHECK_GT(513, ref_buffer->length());
+  for (int i = 0, half_len = ref_buffer->length() >> 1; i < half_len; ++i) {
+    (*ref_buffer)[i << 1] = kHex[i >> 4];
+    (*ref_buffer)[(i << 1) + 1] = kHex[i & 15];
+  }
+  if (ref_buffer->length() & 1) {
+    ref_buffer->last() = kHex[ref_buffer->length() >> 5];
+  }
+  CHECK_EQ(ref_buffer->length(),
+           dynabuf->Write(ref_buffer->start(), ref_buffer->length()));
+}
+
+
+static int ReadData(
+    LogDynamicBuffer* dynabuf, int start_pos, i::Vector<char>* buffer) {
+  return dynabuf->Read(start_pos, buffer->start(), buffer->length());
+}
+
+
+// Helper function used by CHECK_EQ to compare Vectors.
+static inline void CheckEqualsHelper(const char* file, int line,
+                                     const char* expected_source,
+                                     const Vector<char>& expected,
+                                     const char* value_source,
+                                     const Vector<char>& value) {
+  if (expected.length() != value.length()) {
+    V8_Fatal(file, line, "CHECK_EQ(%s, %s) failed\n"
+             "#   Vectors lengths differ: %d expected, %d found",
+             expected_source, value_source,
+             expected.length(), value.length());
+  }
+  if (strncmp(expected.start(), value.start(), expected.length()) != 0) {
+    V8_Fatal(file, line, "CHECK_EQ(%s, %s) failed\n"
+             "#   Vectors contents differ:\n"
+             "#   Expected: %.*s\n"
+             "#   Found: %.*s",
+             expected_source, value_source,
+             expected.length(), expected.start(),
+             value.length(), value.start());
+  }
+}
+
+
+TEST(DynaBufSingleBlock) {
+  LogDynamicBuffer dynabuf(32, 32);
+  EmbeddedVector<char, 32> ref_buf;
+  WriteData(&dynabuf, &ref_buf);
+  EmbeddedVector<char, 32> buf;
+  CHECK_EQ(32, dynabuf.Read(0, buf.start(), buf.length()));
+  CHECK_EQ(32, ReadData(&dynabuf, 0, &buf));
+  CHECK_EQ(ref_buf, buf);
+
+  // Verify that we can't read and write past the end.
+  CHECK_EQ(0, dynabuf.Read(32, buf.start(), buf.length()));
+  CHECK_EQ(0, dynabuf.Write(buf.start(), buf.length()));
+}
+
+
+TEST(DynaBufCrossBlocks) {
+  LogDynamicBuffer dynabuf(32, 128);
+  EmbeddedVector<char, 48> ref_buf;
+  WriteData(&dynabuf, &ref_buf);
+  CHECK_EQ(48, dynabuf.Write(ref_buf.start(), ref_buf.length()));
+  // Verify that we can't write data when remaining buffer space isn't enough.
+  CHECK_EQ(0, dynabuf.Write(ref_buf.start(), ref_buf.length()));
+  EmbeddedVector<char, 48> buf;
+  CHECK_EQ(48, ReadData(&dynabuf, 0, &buf));
+  CHECK_EQ(ref_buf, buf);
+  CHECK_EQ(48, ReadData(&dynabuf, 48, &buf));
+  CHECK_EQ(ref_buf, buf);
+  CHECK_EQ(0, ReadData(&dynabuf, 48 * 2, &buf));
+}
+
+
+TEST(DynaBufReadTruncation) {
+  LogDynamicBuffer dynabuf(32, 128);
+  EmbeddedVector<char, 128> ref_buf;
+  WriteData(&dynabuf, &ref_buf);
+  EmbeddedVector<char, 128> buf;
+  CHECK_EQ(128, ReadData(&dynabuf, 0, &buf));
+  CHECK_EQ(ref_buf, buf);
+  // Try to read near the end with a buffer larger than remaining data size.
+  EmbeddedVector<char, 48> tail_buf;
+  CHECK_EQ(32, ReadData(&dynabuf, 128 - 32, &tail_buf));
+  CHECK_EQ(ref_buf.SubVector(128 - 32, 128), tail_buf.SubVector(0, 32));
+}
+
+#endif  // ENABLE_LOGGING_AND_PROFILING