/*
 * Copyright (C) 2020 Weber Yann
 * 
 * This file is part of pyrpn.
 * 
 * pyrpn is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * any later version.
 * 
 * pyrpn is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with pyrpn.  If not, see <http://www.gnu.org/licenses/>.
 */
#ifndef __rpn_jit__h__
#define __rpn_jit__h__

#include "config.h"

#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/random.h>


#include "rpn_lib.h"
#include "rpn_parse.h"

/**@defgroup rpn RPN evaluation lib
 * @brief High speed RPN expression evaluation librarie
 */
/**@defgroup rpn_compile RPN expression compilation
 * @brief How is an RPN expression transformed into a callable function
 *
 * Compilation is done in two steps :
 * - @ref rpn_tokenize 
 * - @ref rpn_exec
 * @ingroup rpn
 */
/**@defgroup rpn_cmap Executable code map creation
 * @brief A code map containing compiled code to evaluate the expression
 * 
 * In order to provide a callable memory adress, the compilation process starts
 * by creating a new memory map. Then @ref rpn_lib precompiled symbols are
 * copyied in it, suffixed by @ref rpn_exec_ret symbol. Finally, the map is set executable using mprotect.
 * @ingroup rpn_compile
 */

/**@file rpn_jit.h
 * @brief Contains structure & functions for rpn_expr_t manipulation & evaluation
 * @ingroup rpn
 */

/**@brief Mremap chunk size */
#define RPN_MAP_CHUNK 512

/**@brief @ref rpn_expr_t error state */
#define RPN_ERROR -1
/**@brief @ref rpn_expr_t initialization state */
#define RPN_SOURCE 0
/**@brief @ref rpn_expr_t ready to eval state */
#define RPN_READY 1

/**@brief Code part copy macro
 * @param expr rpn_expr_t* A pointer on @ref rpn_expr_t
 * @param NAME code part name
 * @see _rpn_code_part_cpy
 * @ingroup rpn_cmap
 */
#define CODE_PART_CPY(expr, NAME) _rpn_code_part_cpy(expr, &NAME, CODE_SZ(NAME), NULL)

/**@brief Copy a value push in rpn code ptr
 * @param expr rpn_expr_t* A pointer on @ref rpn_expr_t
 * @param value unsigned long that will be push
 * @see _rpn_code_part_cpy
 * @ingroup rpn_cmap
 */
#define CODE_VALUE_CPY(expr, value) _rpn_code_part_cpy(expr, &rpn_value, CODE_SZ(rpn_value), &(value));

/**@brief Add an instruction to push an argument on RPN stack
 * @param expr rpn_expr_t* A pointer on @ref rpn_expr_t
 * @param value unsigned long The argument number
 * @see _rpn_code_part_cpy
 * @ingroup rpn_cmap
 */
#define CODE_ARG_CPY(expr, value) _rpn_code_part_cpy(expr, &rpn_arg, CODE_SZ(rpn_arg), &(value));

/**@brief RPN evaluation function type
 * @ingroup rpn_cmap
 */
typedef unsigned long (*rpn_run_f)(unsigned long, unsigned long*, void*);

/**@brief RPN expression type
 * @ingroup rpn */
typedef struct rpn_expr_s rpn_expr_t;

/**@brief Stores RPN expression informations 
 * @ingroup rpn
 */
struct rpn_expr_s
{
	/**@brief pointer on RPN expression */
	char *expr;
	/**@brief Tokenized version of expression (set by @ref rpn_expr_compile)*/
	rpn_tokenized_t toks;

	/**@brief pointer on jit code memory map */
	void *code_map;

	/**@brief Pointer on next copy addr in code map */
	void *code_map_ptr;
	/**@brief Code map size */
	size_t code_map_sz;

	/**@brief rpn expression arguments count */
	size_t args_count;

	/**@brief Stack values memory */
	rpn_value_t *stack;
	/**@brief rpn jit function stack size
	 * @note item size (size in bytes is sizeof(long) * stack_sz */
	unsigned char stack_sz;

	/**@brief Expression status. Takes value in @ref RPN_ERROR,
	 * @ref RPN_SOURCE, @ref RPN_READY */
	short state;
	/**@brief Error reason */
	char err_reason[128];
};

/**@brief Initialize a new @ref rpn_expr_s
 * @param expr Pointer on the expression
 * @param stack_sz Expression stack size
 * @param args_count Expression argument counter
 * @return 0 if no error else -1
 * @note Once rpn_expr_init has been called, you have to call
 * @ref rpn_expr_close in order to free handled ressources
 * @ingroup rpn
 */
int rpn_expr_init(rpn_expr_t* expr, const unsigned char stack_sz,
	  const size_t args_count);

/**@brief Reinit an existing @ref rpn_expr_s avoiding mmap and malloc
 * for executable memory map and for stack
 * @param expr
 */
int rpn_expr_reinit(rpn_expr_t* expr);

/**@brief Starts a new initialized expression from an expression string
 * @param expr Pointer on an intialized expression ( see @ref rpn_expr_init )
 * @param code '\0' terminated string representing the RPN expr
 * @return 0 if no error else -1 and @ref rpn_expr_s::err_reason is set
 * @note The expression is copied, given buffer can be deallocated after call
 * @ingroup rpn
 */
int rpn_expr_compile(rpn_expr_t *expr, const char *code);

/**@brief Starts a new initialized expression from a tokenized form
 * @param expr Pointer on an intialized expression ( see @ref rpn_expr_init )
 * @param tokens Tokenized form
 * @param long_op If true long operation are used, else 1 chr op are used
 * @return 0 if no error else -1 and @ref rpn_expr_s::err_reason is set
 * @note The @ref rpn_tokenized_s::tokens attribute is "captured" by the
 * @ref rpn_expr_s structure and will be deallocated when @ref rpn_expr_close
 * is called. It is not encouraged to keep a reference on this attribute after
 * @ref rpn_expr_start_untokenize call (but pointed @ref rpn_tokenized_t 
 * can be reused)
 * @ingroup rpn
 */
int rpn_expr_untokenize(rpn_expr_t *expr, rpn_tokenized_t *tokens, char long_op);

/**@brief Generate a new random rpn_expression
 * @param op_sz Number of token in generated expression
 * @param args_count Number of arguments for generated expression
 * @return A pointer on allocated memory storing a valid random RPN expression.
 * NULL if error with errno set (produce a message on stderr)
 * @ingroup rpn
 */
char* rpn_random(size_t op_sz, size_t args_count);

/**@brief Compile an new RPN expression from string expression
 * @param expr Pointer on @ref rpn_expr_s
 * @return 0 if no error else -1 and set @ref rpn_expr_s err_reason
 * @ingroup rpn_compile
 */
int _rpn_expr_compile_expr(rpn_expr_t* expr);
/**@brief Compile an new RPN expression from string expression
 * @param expr Pointer on @ref rpn_expr_s
 * @return 0 if no error else -1 and set @ref rpn_expr_s err_reason
 * @ingroup rpn_compile
 */
int _rpn_expr_compile_tokens(rpn_expr_t* expr);

/**@brief Evaluate an RPN expression
 * @param expr Pointer on @ref rpn_expr_s
 * @param args List of arguments
 * @return Head of stack after evaluation
 * @note If expression not compiled yet compile it before eval
 * @ingroup rpn
 */
unsigned long rpn_expr_eval(rpn_expr_t *expr, unsigned long *args);

/**@brief Free ressources handled by given @ref rpn_expr_s
 * @param expr Pointer on rpn_expr_t
 * @param expr Pointer on @ref rpn_expr_s
 * @ingroup rpn
 */
void rpn_expr_close(rpn_expr_t* expr);

/**@brief bzero memory allocated for stack
 * @param expr Pointer on rpn_expr_t
 * @ingroup rpn
 */
void rpn_expr_reset_stack(rpn_expr_t *expr);

/**@brief Copy precompiled code from @ref rpn_lib.h in expression code map
 * @param expr The expression being compiled
 * @param token Pointer on token informations
 * @return 0 if no error else -1, set error and errno
 * @ingroup rpn_cmap
 */
int _rpn_expr_token_copy(rpn_expr_t *expr, rpn_token_t *token);

/**@brief Copy a part of code to the code map
 * @warning designed to be use with @ref CODE_PART_CPY and CODE_VALUE_CPY macros
 * @param expr Pointer on rpn_expr_t
 * @param code_part copy src address
 * @param code_part_sz the code part size
 * @param value if not NULL set the first code part
 * 	instruction argument to this value
 * @return 0 if no error else -1 and set errno
 * @ingroup rpn_cmap
 */
int _rpn_code_part_cpy(rpn_expr_t* expr, const void* code_part,
	unsigned long code_part_sz, const unsigned long *value);

/**@brief Allocate a memory map for given rpn_expt_t and copy the function
 * header
 * @param expr Pointer on rpn_expr_t
 * @return 0 if no error, else -1 and set errno
 * @ingroup rpn_cmap
 */
int _rpn_expr_init_map(rpn_expr_t* expr);

/**@brief Copy the function suffix and change memory map protection
 * @param expr Pointer on rpn_expr_t
 * @return 0 if no error, else -1 and set errno
 * @ingroup rpn_cmap
 */
int _rpn_expr_end_map(rpn_expr_t *expr);

#endif