src/vm/Printer.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=8 sts=2 et sw=2 tw=80:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef vm_Printer_h
#define vm_Printer_h

#include "mozilla/Attributes.h"
#include "mozilla/Range.h"

#include <stdarg.h>
#include <stddef.h>
#include <stdio.h>
#include <string.h>

#include "js/TypeDecls.h"
#include "js/Utility.h"

namespace js {

class LifoAlloc;

// Generic printf interface, similar to an ostream in the standard library.
//
// This class is useful to make generic printers which can work either with a
// file backend, with a buffer allocated with an JSContext or a link-list
// of chunks allocated with a LifoAlloc.
class GenericPrinter {
 protected:
  bool hadOOM_;  // whether reportOutOfMemory() has been called.

  constexpr GenericPrinter() : hadOOM_(false) {}

 public:
  // Puts |len| characters from |s| at the current position and
  // return true on success, false on failure.
  virtual bool put(const char* s, size_t len) = 0;
  virtual void flush() { /* Do nothing */
  }

  inline bool put(const char* s) { return put(s, strlen(s)); }
  inline bool putChar(const char c) { return put(&c, 1); }

  // Prints a formatted string into the buffer.
  bool printf(const char* fmt, ...) MOZ_FORMAT_PRINTF(2, 3);
  bool vprintf(const char* fmt, va_list ap) MOZ_FORMAT_PRINTF(2, 0);

  // Report that a string operation failed to get the memory it requested.
  virtual void reportOutOfMemory();

  // Return true if this Sprinter ran out of memory.
  virtual bool hadOutOfMemory() const;
};

// Sprintf, but with unlimited and automatically allocated buffering.
class Sprinter final : public GenericPrinter {
 public:
  struct InvariantChecker {
    const Sprinter* parent;

    explicit InvariantChecker(const Sprinter* p) : parent(p) {
      parent->checkInvariants();
    }

    ~InvariantChecker() { parent->checkInvariants(); }
  };

  JSContext* context;  // context executing the decompiler

 private:
  static const size_t DefaultSize;
#ifdef DEBUG
  bool initialized;  // true if this is initialized, use for debug builds
#endif
  bool shouldReportOOM;  // whether to report OOM to the context
  char* base;            // malloc'd buffer address
  size_t size;           // size of buffer allocated at base
  ptrdiff_t offset;      // offset of next free char in buffer

  [[nodiscard]] bool realloc_(size_t newSize);

 public:
  explicit Sprinter(JSContext* cx, bool shouldReportOOM = true);
  ~Sprinter();

  // Initialize this sprinter, returns false on error.
  [[nodiscard]] bool init();

  void checkInvariants() const;

  const char* string() const { return base; }
  const char* stringEnd() const { return base + offset; }
  JS::UniqueChars release();

  // Returns the string at offset |off|.
  char* stringAt(ptrdiff_t off) const;
  // Returns the char at offset |off|.
  char& operator[](size_t off);

  // Attempt to reserve len + 1 space (for a trailing nullptr byte). If the
  // attempt succeeds, return a pointer to the start of that space and adjust
  // the internal content. The caller *must* completely fill this space on
  // success.
  char* reserve(size_t len);

  // Puts |len| characters from |s| at the current position and
  // return true on success, false on failure.
  virtual bool put(const char* s, size_t len) override;
  using GenericPrinter::put;  // pick up |inline bool put(const char* s);|

  // Format the given format/arguments as if by JS_vsmprintf, then put it.
  // Return true on success, else return false and report an error (typically
  // OOM).
  [[nodiscard]] bool jsprintf(const char* fmt, ...) MOZ_FORMAT_PRINTF(2, 3);

  bool putString(JSString* str);

  ptrdiff_t getOffset() const;

  // Report that a string operation failed to get the memory it requested. The
  // first call to this function calls JS_ReportOutOfMemory, and sets this
  // Sprinter's outOfMemory flag; subsequent calls do nothing.
  virtual void reportOutOfMemory() override;
};

// Fprinter, print a string directly into a file.
class Fprinter final : public GenericPrinter {
 private:
  FILE* file_;
  bool init_;

 public:
  explicit Fprinter(FILE* fp);

  constexpr Fprinter() : file_(nullptr), init_(false) {}

#ifdef DEBUG
  ~Fprinter();
#endif

  // Initialize this printer, returns false on error.
  [[nodiscard]] bool init(const char* path);
  void init(FILE* fp);
  bool isInitialized() const { return file_ != nullptr; }
  void flush() override;
  void finish();

  // Puts |len| characters from |s| at the current position and
  // return true on success, false on failure.
  virtual bool put(const char* s, size_t len) override;
  using GenericPrinter::put;  // pick up |inline bool put(const char* s);|
};

// LSprinter, is similar to Sprinter except that instead of using an
// JSContext to allocate strings, it use a LifoAlloc as a backend for the
// allocation of the chunk of the string.
class LSprinter final : public GenericPrinter {
 private:
  struct Chunk {
    Chunk* next;
    size_t length;

    char* chars() { return reinterpret_cast<char*>(this + 1); }
    char* end() { return chars() + length; }
  };

 private:
  LifoAlloc* alloc_;  // LifoAlloc used as a backend of chunk allocations.
  Chunk* head_;
  Chunk* tail_;
  size_t unused_;

 public:
  explicit LSprinter(LifoAlloc* lifoAlloc);
  ~LSprinter();

  // Copy the content of the chunks into another printer, such that we can
  // flush the content of this printer to a file.
  void exportInto(GenericPrinter& out) const;

  // Drop the current string, and let them be free with the LifoAlloc.
  void clear();

  // Puts |len| characters from |s| at the current position and
  // return true on success, false on failure.
  virtual bool put(const char* s, size_t len) override;
  using GenericPrinter::put;  // pick up |inline bool put(const char* s);|
};

// Map escaped code to the letter/symbol escaped with a backslash.
extern const char js_EscapeMap[];

// Return a C-string containing the chars in str, with any non-printing chars
// escaped. If the optional quote parameter is present and is not '\0', quotes
// (as specified by the quote argument) are also escaped, and the quote
// character is appended at the beginning and end of the result string.
// The returned string is guaranteed to contain only ASCII characters.
extern JS::UniqueChars QuoteString(JSContext* cx, JSString* str,
                                   char quote = '\0');

// Appends the quoted string to the given Sprinter. Follows the same semantics
// as QuoteString from above.
extern bool QuoteString(Sprinter* sp, JSString* str, char quote = '\0');

// Appends the quoted string to the given Sprinter. Follows the same
// Appends the JSON quoted string to the given Sprinter.
extern bool JSONQuoteString(Sprinter* sp, JSString* str);

// Internal implementation code for QuoteString methods above.
enum class QuoteTarget { String, JSON };

template <QuoteTarget target, typename CharT>
bool QuoteString(Sprinter* sp, const mozilla::Range<const CharT> chars,
                 char quote = '\0');

}  // namespace js

#endif  // vm_Printer_h