Refactors CPU feature detection.

runtime/vm/cpuinfo_android.cc

Index: runtime/vm/cpuinfo_android.cc
===================================================================
--- runtime/vm/cpuinfo_android.cc	(revision 0)
+++ runtime/vm/cpuinfo_android.cc	(revision 0)
@@ -0,0 +1,169 @@
+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#include "vm/globals.h"
+#if defined(TARGET_OS_ANDROID)
+
+#include "vm/cpuinfo.h"
+
+#include <ctype.h>  // NOLINT
+#include <string.h>  // NOLINT
+
+#include "platform/assert.h"
+
+namespace dart {
+
+char* CpuInfo::data_ = NULL;
+intptr_t CpuInfo::datalen_ = 0;
+
+void CpuInfo::Read() {
+  // Get the size of the cpuinfo file by reading it until the end. This is
+  // required because files under /proc do not always return a valid size
+  // when using fseek(0, SEEK_END) + ftell(). Nor can they be mmap()-ed.
+  static const char PATHNAME[] = "/proc/cpuinfo";
+  FILE* fp = fopen(PATHNAME, "r");
+  if (fp != NULL) {
+    for (;;) {
+      char buffer[256];
+      size_t n = fread(buffer, 1, sizeof(buffer), fp);
+      if (n == 0) {
+        break;
+      }
+      datalen_ += n;
+    }
+    fclose(fp);
+  }
+
+  // Read the contents of the cpuinfo file.
+  data_ = new char[datalen_ + 1];
+  fp = fopen(PATHNAME, "r");
+  if (fp != NULL) {
+    for (intptr_t offset = 0; offset < datalen_; ) {
+      size_t n = fread(data_ + offset, 1, datalen_ - offset, fp);
+      if (n == 0) {
+        break;
+      }
+      offset += n;
+    }
+    fclose(fp);
+  }
+
+  // Zero-terminate the data.
+  data_[datalen_] = '\0';
+}
+
+
+static char* FieldStart(char* data, const char* field) {
+  // Look for first field occurrence, and ensure it starts the line.
+  size_t fieldlen = strlen(field);
+  char* p = data;
+  for (;;) {
+    p = strstr(p, field);
+    if (p == NULL) {
+      return NULL;
+    }
+    if (p == data || p[-1] == '\n') {
+      break;
+    }
+    p += fieldlen;
+  }
+
+  // Skip to the first colon followed by a space.
+  p = strchr(p + fieldlen, ':');
+  if (p == NULL || !isspace(p[1])) {
+    return NULL;
+  }
+  p += 2;
+
+  return p;
+}
+
+
+bool CpuInfo::FieldContains(const char* field, const char* search_string) {
+  ASSERT(data_ != NULL);
+  ASSERT(search_string != NULL);
+
+  char *p = FieldStart(data_, field);
+  if (p == NULL) {
+    return false;
+  }
+
+  // Find the end of the line.
+  char* q = strchr(p, '\n');
+  if (q == NULL) {
+    q = data_ + datalen_;
+  }
+
+  char saved_end = *q;
+  *q = '\0';
+  bool ret = (strcasestr(p, search_string) != NULL);
+  *q = saved_end;
+
+  return ret;
+}
+
+
+// Extract the content of a the first occurrence of a given field in
+// the content of the cpuinfo file and return it as a heap-allocated
+// string that must be freed by the caller using delete[].
+// Return NULL if not found.
+intptr_t CpuInfo::ExtractField(
+    const char* field, char* dest, const intptr_t dest_len) {

[Cutch, 2014/01/02 19:39:19]

Should the OS specific code populate a field table and then ExtractField,
HasField just queries the table?

+  ASSERT(field != NULL);
+  ASSERT(data_ != NULL);
+
+  char* p = FieldStart(data_, field);
+  if (p == NULL) {
+    if (dest != NULL) {
+      dest[0] = '\0';
+    }
+    return 0;
+  }
+
+  // Find the end of the line.
+  char* q = strchr(p, '\n');
+  if (q == NULL) {
+    q = data_ + datalen_;
+  }
+
+  intptr_t len = (dest_len < (q - p + 1)) ? (dest_len - 1) : q - p;
+  if (dest != NULL) {
+    // Copy the line into dest, leaving enough room for a null-terminator.
+    char saved_end = *q;
+    *q = '\0';
+    strncpy(dest, p, len);
+    dest[len] = '\0';
+    *q = saved_end;
+  }
+
+  return len;
+}
+
+
+bool CpuInfo::HasField(const char* field) {
+  ASSERT(field != NULL);
+  ASSERT(data_ != NULL);
+  intptr_t len = ExtractField(field, NULL, 0);
+  return (len != 0);
+}
+
+
+intptr_t CpuInfo::GetCpuModel(char* dest, const intptr_t dest_len) {
+#if defined(HOST_ARCH_IA32) || defined(HOST_ARCH_X64)
+  ASSERT(HasField("model name"));
+  return ExtractField("model name", dest, dest_len);
+#elif defined(HOST_ARCH_ARM)
+  ASSERT(HasField("Hardware"));
+  return ExtractField("Hardware", dest, dest_len);
+#elif defined(HOST_ARCH_MIPS)
+  ASSERT(HasField("cpu model"));
+  return ExtractField("cpu model", dest, dest_len);
+#else
+#error Unrecognized target architecture
+#endif
+}
+
+}  // namespace dart
+
+#endif  // defined(TARGET_OS_ANDROID)