src: add node's internals constants

This commit refactors llv8-constants to make it easier to introduce
Node's internals constants. Common code for llv8 and node constants is
now on src/constants.h. Also moved the Error class to its own file,
removing the dependency on src/llv8.h to use Errors.

llnode.gyp.json

@@ -16,10 +16,13 @@
     ],
 
     "sources": [
+      "src/constants.cc",
+      "src/error.cc",
       "src/llnode.cc",
       "src/llv8.cc",
       "src/llv8-constants.cc",
       "src/llscan.cc",
+      "src/node-constants.cc",
     ],
 
     "conditions": [

src/constants.cc

@@ -0,0 +1,121 @@
+#include <cinttypes>
+
+#include <lldb/API/SBExpressionOptions.h>
+
+#include "src/constants.h"
+
+using lldb::SBAddress;
+using lldb::SBError;
+using lldb::SBSymbol;
+using lldb::SBSymbolContext;
+using lldb::SBSymbolContextList;
+
+namespace llnode {
+
+template <typename T>
+T ReadSymbolFromTarget(SBTarget& target, SBAddress& start, const char* name,
+                       Error& err) {
+  SBError sberr;
+  T res = 0;
+  target.ReadMemory(start, &res, sizeof(T), sberr);
+  if (!sberr.Fail()) {
+    err = Error::Ok();
+  } else {
+    err = Error::Failure("Failed to read symbol %s", name);
+  }
+  return res;
+}
+
+int64_t Constants::LookupConstant(SBTarget target, const char* name,
+                                  int64_t def, Error& err) {
+  int64_t res = 0;
+  res = def;
+
+  SBSymbolContextList context_list = target.FindSymbols(name);
+
+  if (!context_list.IsValid() || context_list.GetSize() == 0) {
+    err = Error::Failure("Failed to find symbol %s", name);
+    return res;
+  }
+
+  SBSymbolContext context = context_list.GetContextAtIndex(0);
+  SBSymbol symbol = context.GetSymbol();
+  if (!symbol.IsValid()) {
+    err = Error::Failure("Failed to fetch symbol %s from context", name);
+    return res;
+  }
+
+  SBAddress start = symbol.GetStartAddress();
+  SBAddress end = symbol.GetEndAddress();
+  uint32_t size = end.GetOffset() - start.GetOffset();
+
+  // NOTE: size could be bigger for at the end symbols
+  if (size >= 8) {
+    res = ReadSymbolFromTarget<int64_t>(target, start, name, err);
+  } else if (size == 4) {
+    int32_t tmp = ReadSymbolFromTarget<int32_t>(target, start, name, err);
+    res = static_cast<int64_t>(tmp);
+  } else if (size == 2) {
+    int16_t tmp = ReadSymbolFromTarget<int16_t>(target, start, name, err);
+    res = static_cast<int64_t>(tmp);
+  } else if (size == 1) {
+    int8_t tmp = ReadSymbolFromTarget<int8_t>(target, start, name, err);
+    res = static_cast<int64_t>(tmp);
+  } else {
+    err = Error::Failure("Unexpected symbol size %" PRIu32 " of symbol %s",
+                         size, name);
+  }
+
+  return res;
+}
+
+void Constants::Assign(SBTarget target) {
+  loaded_ = false;
+  target_ = target;
+}
+
+
+int64_t Constants::LoadRawConstant(const char* name, int64_t def) {
+  Error err;
+  int64_t v = Constants::LookupConstant(target_, name, def, err);
+  if (err.Fail()) {
+    Error::PrintInDebugMode(
+        "Failed to load raw constant %s, default to %" PRId64, name, def);
+  }
+
+  return v;
+}
+
+int64_t Constants::LoadConstant(const char* name, Error& err, int64_t def) {
+  int64_t v = Constants::LookupConstant(
+      target_, (constant_prefix() + name).c_str(), def, err);
+  return v;
+}
+
+int64_t Constants::LoadConstant(const char* name, int64_t def) {
+  Error err;
+  int64_t v = LoadConstant(name, err, def);
+  if (err.Fail()) {
+    Error::PrintInDebugMode("Failed to load constant %s, default to %" PRId64,
+                            name, def);
+  }
+
+  return v;
+}
+
+int64_t Constants::LoadConstant(const char* name, const char* fallback,
+                                int64_t def) {
+  Error err;
+  int64_t v = LoadConstant(name, err, def);
+  if (err.Fail()) v = LoadConstant(fallback, err, def);
+  if (err.Fail()) {
+    Error::PrintInDebugMode(
+        "Failed to load constant %s, fallback %s, default to %" PRId64, name,
+        fallback, def);
+  }
+
+  return v;
+}
+
+
+}  // namespace llnode

src/constants.h

@@ -0,0 +1,47 @@
+#ifndef SRC_CONSTANTS_H_
+#define SRC_CONSTANTS_H_
+
+#include <lldb/API/LLDB.h>
+#include <string>
+
+#include "src/error.h"
+
+using lldb::SBTarget;
+
+namespace llnode {
+
+#define CONSTANTS_DEFAULT_METHODS(NAME) \
+  inline NAME* operator()() {           \
+    if (loaded_) return this;           \
+    loaded_ = true;                     \
+    Load();                             \
+    return this;                        \
+  }
+
+class Constants {
+ public:
+  Constants() : loaded_(false) {}
+
+  inline bool is_loaded() const { return loaded_; }
+
+  void Assign(lldb::SBTarget target);
+
+  inline virtual std::string constant_prefix() { return ""; };
+
+  static int64_t LookupConstant(SBTarget target, const char* name, int64_t def,
+                                Error& err);
+
+ protected:
+  int64_t LoadRawConstant(const char* name, int64_t def = -1);
+  int64_t LoadConstant(const char* name, Error& err, int64_t def = -1);
+  int64_t LoadConstant(const char* name, int64_t def = -1);
+  int64_t LoadConstant(const char* name, const char* fallback,
+                       int64_t def = -1);
+
+  lldb::SBTarget target_;
+  bool loaded_;
+};
+
+}  // namespace llnode
+
+#endif

src/error.cc

@@ -0,0 +1,44 @@
+#include "error.h"
+
+namespace llnode {
+bool Error::is_debug_mode = false;
+
+Error::Error(bool failed, const char* format, ...) {
+  failed_ = failed;
+  char tmp[kMaxMessageLength];
+  va_list arglist;
+  va_start(arglist, format);
+  vsnprintf(tmp, sizeof(tmp), format, arglist);
+  va_end(arglist);
+  msg_ = tmp;
+}
+
+
+void Error::PrintInDebugMode(const char* format, ...) {
+  if (!is_debug_mode) {
+    return;
+  }
+  char fmt[kMaxMessageLength];
+  snprintf(fmt, sizeof(fmt), "[llv8] %s\n", format);
+  va_list arglist;
+  va_start(arglist, format);
+  vfprintf(stderr, fmt, arglist);
+  va_end(arglist);
+}
+
+
+Error Error::Failure(std::string msg) {
+  PrintInDebugMode("%s", msg.c_str());
+  return Error(true, msg);
+}
+
+
+Error Error::Failure(const char* format, ...) {
+  char tmp[kMaxMessageLength];
+  va_list arglist;
+  va_start(arglist, format);
+  vsnprintf(tmp, sizeof(tmp), format, arglist);
+  va_end(arglist);
+  return Error::Failure(std::string(tmp));
+}
+}  // namespace llnode

src/error.h

@@ -0,0 +1,37 @@
+#ifndef SRC_ERROR_H_
+#define SRC_ERROR_H_
+
+#include <string>
+
+namespace llnode {
+
+class Error {
+ public:
+  Error() : failed_(false), msg_("") {}
+  Error(bool failed, std::string msg) : failed_(failed), msg_(msg) {}
+  Error(bool failed, const char* format, ...)
+      __attribute__((format(printf, 3, 4)));
+
+  static inline Error Ok() { return Error(false, "ok"); }
+  static Error Failure(std::string msg);
+  static Error Failure(const char* format, ...)
+      __attribute__((format(printf, 1, 2)));
+  static void PrintInDebugMode(const char* format, ...)
+      __attribute__((format(printf, 1, 2)));
+
+  inline bool Success() const { return !Fail(); }
+  inline bool Fail() const { return failed_; }
+
+  inline const char* GetMessage() { return msg_.c_str(); }
+
+  static void SetDebugMode(bool mode) { is_debug_mode = mode; }
+
+ private:
+  bool failed_;
+  std::string msg_;
+  static const size_t kMaxMessageLength = 128;
+  static bool is_debug_mode;
+};
+}  // namespace llnode
+
+#endif

src/llnode.cc

@@ -7,6 +7,7 @@
 
 #include <lldb/API/SBExpressionOptions.h>
 
+#include "src/error.h"
 #include "src/llnode.h"
 #include "src/llscan.h"
 #include "src/llv8.h"
@@ -121,7 +122,7 @@ bool BacktraceCmd::DoExecute(SBDebugger d, char** cmd,
     const uint64_t pc = frame.GetPC();
 
     if (!frame.GetSymbol().IsValid()) {
-      v8::Error err;
+      Error err;
       v8::JSFrame v8_frame(llv8_, static_cast<int64_t>(frame.GetFP()));
       std::string res = v8_frame.Inspect(true, err);
       if (err.Success()) {
@@ -197,7 +198,7 @@ bool PrintCmd::DoExecute(SBDebugger d, char** cmd,
   llv8_->Load(target);
 
   v8::Value v8_value(llv8_, value.GetValueAsSigned());
-  v8::Error err;
+  Error err;
   std::string res = v8_value.Inspect(&inspect_options, err);
   if (err.Fail()) {
     result.SetError(err.GetMessage());
@@ -276,7 +277,7 @@ bool ListCmd::DoExecute(SBDebugger d, char** cmd,
   }
 
   // V8 frame
-  v8::Error err;
+  Error err;
   v8::JSFrame v8_frame(llv8_, static_cast<int64_t>(frame.GetFP()));
 
   const static uint32_t kDisplayLines = 4;
@@ -307,7 +308,7 @@ void InitDebugMode() {
     is_debug_mode = true;
   }
 
-  v8::Error::SetDebugMode(is_debug_mode);
+  Error::SetDebugMode(is_debug_mode);
 }
 
 }  // namespace llnode