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// macho_walker.h: Iterate over the load commands in a mach-o file
//
// Author: Dan Waylonis

#ifndef COMMON_MAC_MACHO_WALKER_H__
#define COMMON_MAC_MACHO_WALKER_H__

#include <mach-o/loader.h>
#include <sys/types.h>

namespace MacFileUtilities {

class MachoWalker {
 public:
  // A callback function executed when a new load command is read.  If no
  // further processing of load commands is desired, return false.  Otherwise,
  // return true.
  // |cmd| is the current command, and |offset| is the location relative to the
  // beginning of the file (not header) where the command was read.  If |swap|
  // is set, then any command data (other than the returned load_command) should
  // be swapped when read
  typedef bool (*LoadCommandCallback)(MachoWalker *walker, load_command *cmd,
                                      off_t offset, bool swap, void *context);

  MachoWalker(const char *path, LoadCommandCallback callback, void *context);
  MachoWalker(int file_descriptor, LoadCommandCallback callback, void *context);
  ~MachoWalker();

  // Begin walking the header for |cpu_type|.  If |cpu_type| is 0, then the
  // native cpu type is used.  Otherwise, accepted values are listed in
  // /usr/include/mach/machine.h (e.g., CPU_TYPE_X86 or CPU_TYPE_POWERPC).
  // Returns false if opening the file failed or if the |cpu_type| is not
  // present in the file.
  bool WalkHeader(int cpu_type);

  // Locate (if any) the header offset for |cpu_type| and return in |offset|.
  // Return true if found, false otherwise.
  bool FindHeader(int cpu_type, off_t &offset);

  // Read |size| bytes from the opened file at |offset| into |buffer|
  bool ReadBytes(void *buffer, size_t size, off_t offset);
  
  // Return the current header and header offset
  bool CurrentHeader(struct mach_header_64 *header, off_t *offset);

 private:
  // Validate the |cpu_type|
  int ValidateCPUType(int cpu_type);

  // Process an individual header starting at |offset| from the start of the
  // file.  Return true if successful, false otherwise.
  bool WalkHeaderAtOffset(off_t offset);
  bool WalkHeader64AtOffset(off_t offset);

  // Bottleneck for walking the load commands
  bool WalkHeaderCore(off_t offset, uint32_t number_of_commands, bool swap);

  // File descriptor to the opened file
  int file_;

  // User specified callback & context
  LoadCommandCallback callback_;
  void *callback_context_;
  
  // Current header, size, and offset.  The mach_header_64 is used for both
  // 32-bit and 64-bit headers because they only differ in their last field
  // (reserved).  By adding the |current_header_size_| and the 
  // |current_header_offset_|, you can determine the offset in the file just
  // after the header.
  struct mach_header_64 *current_header_;
  unsigned long current_header_size_;
  off_t current_header_offset_;
};

}  // namespace MacFileUtilities

#endif  // COMMON_MAC_MACHO_WALKER_H__
