slc/engine/slc.h

#ifndef SLC_H
#define SLC_H

/** Possible word types */
enum SLC_WORDTYP {
	/** Still in plain text */
	SLC_WORDTYP_TEXT = 0,
	/** Native code, use get_word_storage_offset to get what to run (relative pointer or array of pointers) */
	SLC_WORDTYP_NATIVE = 1,
	/** "Threaded code" (utf16-like word offsets) and encoded parentheses IN-PLACE inlined where text was before */
	SLC_WORDTYP_THREADED_INLINE = 2,
	/** "Threaded code" that did not fit in-place and is thus stored in session storage, word offset tells where */
	SLC_WORDTYP_THREADED_SESSION = 3
};
typedef enum SLC_WORDTYP SLC_WORDTYP;

/** Gets the wordtyp from a flags field - see wordstart */
static inline SLC_WORDTYP get_word_type(uint8_t flags) {
	return (SLC_WORDTYP)(flags >> 6);
}

// TODO: probably should remove this?
/** Gets the 6-bit variable count (at most 64 vars possible per word) */
static inline uint8_t get_word_var_count(uint8_t flags) {
	return (flags && 0x3F); /* 0011 1111 */
}

/** Gets the 24bit storage offset of the word: Natives contain pointers in an offseted array */
static inline uint32_t get_word_storage_offset(uint8_t high_offset, uint16_t low_offset) {
	return ((uint32_t)high_offset << 16) + low_offset;
}

/**
 * A word definition starts right after this. After processing it, we inline overwrite random parts of it in memory...
 *
 * Examples:
 *
 * 	#: just_code
 * 	  #dup
 * 	  #inc
 * 	  #swap
 * 	#
 *
 * 	: with_vars @a; @b; @c;
 * 		@a
 * 		inc
 * 		@a(.)
 * 	;
 *
 * 	#builtin: to_prefix
 * 		#swap
 * 		#dup
 *
 * TODO: How to do this builtin to be properly changed inline? If it can be inline threaded-coded, then its fine, but is spec-case
 * 	^^The above always needs starting '#builtin' at the definition and inside. That is exchanged to real prefix...
 *    This is used for implementation implementing built-ins with FORTH-like code instead of native (saves native interpret. space)
 *
 * 	#: structural (
 * 		#parse_num
 * 		#dup
 * 		#inc
 * 		#swap
 * 		#print
 * 		#print
 * 	) [ #parse_num #print ] { #parse_num #print }
 * 	#
 */
struct wordstart {
	/** The ':' char - after processing it stores the flags */
	uint8_t flags;
	/** whitespace after ':' and first char of name - after processing contains the high-offset */
	uint16_t high_offset;
	/** Either remaining parts of the name - or the leading tab/space for starting variables (or newline if there's none) */
	uint8_t low_offset;
	/* char ..name[]; // The REMAINS of name of the word being defined. Can be empty! */
	/* char vars[]; // The local (at least 1-letter) variables of the word. Can be empty - min 4x8bit per a var, like: " @a;" */
	// TODO: process vars when doing the reader->session store
	/* char newline; // there is always a newline at this point! XXX: "@a; ", "@b;\n" is how we store vars (*/
	/* char data[]; // The "body" of the word - either text source or inline threaded code (at least 1 character) */
	/* char ender[]; // The ender-string that ends the word - always at least 1 character! */
};
typedef struct wordstart wordstart;

enum SLC_SYM_OP { SLC_SYM_SET, SLC_SYM_GET, SLC_SYM_ERASE };
typedef enum SLC_SYM_OP SLC_SYM_OP;
enum SLC_STACK_OP { SLC_STACK_PUSH, SLC_STACK_POP, SLC_STACK_AT, SLC_STACK_COUNT, SLC_STACK_ERASE };
typedef enum SLC_STACK_OP SLC_STACK_OP;
enum SLC_SESSION_OP {
	SLC_SESSION_ALLOC,
	SLC_SESSION_ERASE,
	SLC_SESSION_PUSH,
	SLC_SESSION_GET,
	SLC_SESSION_SET,
	SLC_SESSION_PROCESS
};
typedef enum SLC_SESSION_OP SLC_SESSION_OP;
enum SLC_IO_OP {
	SLC_IO_OPEN,
	SLC_IO_OPEN_TMP,
	SLC_IO_REMOVE_TMPS,
	SLC_IO_CLOSE,
	SLC_IO_READ,
	SLC_IO_WRITE,
	SLC_IO_LOCK,
	SLC_IO_UNLOCK,
	SLC_IO_CMD,
};
typedef enum SLC_IO_OP SLC_IO_OP;

/**
 * Function-abstraction for a "symbol-table".
 *
 * Operations:
 *
 * 		SLC_SYM_SET Saves a mapping from key->word in symbol table. word==NULL removes mapping. Returns ptr back or NULL on errors.
 * 		SLC_SYM_GET Gets the symbol at key (the word parameter is unused). Returns NULL if there is no word for the key.
 * 		SLC_SYM_ERASE Erases the symbol table so it becomes empty again. Can never fail, returns NULL.
 *
 * Rem.: On GET we return a wordstart* in case the key is to a word and a regular uint32_t* if its a variable name!
 *
 * @param op Defines which operation the caller wants.
 * @param key The key (both for SET and GET)
 * @param ptr When adding a found word/variable to the symbol table, the key will point to this wordstart* or uint32_t*
 * @returns The word/var definition stored for the key, or NULL when it is not stored yet or op is SET and there was an error.
 */
typedef void* (*sym)(SLC_SYM_OP op, char *key, void *ptr);
// TODO: union for this?

/**
 * Function-abstraction for an integer "stack".
 *
 * Operations:
 * 
 * 		SLC_STACK_PUSH pushes the "elem" to the stack. Returns 1 if succeeded, otherwise 0.
 * 		SLC_STACK_POP pops the stack - does not return meaningful value, beware of underflowing!
 * 		SLC_STACK_AT returns the "param"th element down from the top of the stack
 * 		SLC_STACK_COUNT returns the number of elements in the stack
 * 		SLC_STACK_ERASE Makes the stack empty. Basically as if you would POP the COUNT times.
 *
 * @param op Defines which operation the caller wants.
 * @param param On SLC_STACK_PUSH, this is the element to push onto the stack, in case of SLC_STACK_AT, its the index.
 * @return The element at the given stack location in case of SLC_STACK_AT or the count in case of SLC_STACK_COUNT. Can show error!
 */
typedef uint32_t (*stack)(SLC_STACK_OP op, uint32_t param);

/**
 * Function-abstraction for a "session-storage".
 *
 * Operations:
 * 		SLC_SESSION_ALLOC allocates parameter amount of memory and returns an accessor index.
 * 		SLC_SESSION_ERASE erase the session storage (all of it) - all parameters are unused
 * 		SLC_SESSION_PUSH adds the given byte (value in i) to the end of the session storage (by growing it) - j unused
 * 		SLC_SESSION_GET gets byte at the ith accessor index - j unused
 * 		SLC_SESSION_SET gets byte at the ith accessor index to be of (byte)j
 * 		SLC_SESSION_PROCESS gets the last j bytes and moves them overriding bytes at index i, then "shrinks" the storage by j.
 *
 * @param op Defines which operation the caller wants.
 * @param i Used on SESSION_GET and is the accessor index, in case of SESSIN_ALLOC it is the amount to allocate.
 * @param j Used on SESSION_SET as the byte value and on SESSION_PROCESS as the amount of bytes to "process" / shrink.
 * @returns The accessor index in case of ALLOC (0xFFFFFFFF == -1 means error), on get it returns the store BYTE as uint32_t
 */
typedef uint32_t (*session)(SLC_SESSION_OP op, uint32_t i, uint32_t j);

/**
 * Function-abstraction for io connectors.
 *
 * Operations:
 *
 * 		SLC_IO_OPEN Opens a PERSISTENT file with the given name. Returns the handle pointer (or NULL on error).
 * 		SLC_IO_CLOSE Closes a PERSISTENT file with the given handle.
 * 		SLC_IO_OPEN_TMP Opens a TEMPORARY file with the given name. Returns the handle pointer.
 * 		SLC_IO_CLOSE_TMP Removes the TEMPORARY file with the given handle.
 * 		SLC_IO_READ Reads a character from the given file handle. Returns pointer to the character that got read.
 * 		SLC_IO_WRITE Writes a character from the given file handle. The 'param' points to the character to write (1 byte)
 * 		SLC_IO_LOCK Locks the given file handle for exclusive reads and writes (others need to use lock/unlock too)
 * 		SLC_IO_UNLOCK Locks the given file handle for exclusive reads and writes (others need to use lock/unlock too)
 * 		SLC_IO_CMD Runs the given command on the operating system. The 'param' is the command (+args) and returned is std output.
 *
 * @param op Defines which operation the caller wants.
 * @param param The name or temporary name or command or the handle pointer parameter depending on op.
 * @returns A handle pointer or pointer to character to read / written or closed/unlocked handle (NULL on errors). Also cmd stdout.
 */
typedef const char* (*ioconn)(SLC_IO_OP op, const char *param);
// TODO: union for this?

/**
 * Function-abstraction for reading the source code byte-by-byte.
 */
typedef uint8_t (*coderead)();

/**
 * This function runs the main slc engine over a snippet of code.
 *
 * The code_src is the entry of what we start interpreting, but you can do (un)buffered reads in it
 * because we will use session_storage to store the source code data into memory while processing...
 * Rem.: This also helps with the "include" directives using io_connector and do some kind of recursion maybe.
 * Rem.: This architecture also let us try to immediately "threaded_code" optimize the newly added word definition,
 *       which is possible if it relies on no forward references - this is the most happy case in my opinion!
 *
 * The session_storage is where we process the words data (possibly introducing threaded code as early as possible).
 * This should also let the code "allocate" some random memory too and get an offset for it (there will be no other way).
 *
 * The symbol_table not only store "words", but direct access offsets for:
 *
 * - words themselves (direct offset)
 * - variables of the words (direct offset)
 *
 * The code stack is what the interpreter uses for return addresses, the data stack however is FORTH-style usual stack.
 * The "insert_stack" collects things that we will read instead of reading the code_src AFTER a return from current word.
 * A \0 value should be there at the end of it until we RETURN from the word - from when we start processing.
 *
 * The io_connector is needed so that the engine have connection for temporary and real files and things simulating those.
 *
 * The prefix, ender and varprefix strings really just help when you use SLC to define a compiler and you need these.
 *
 * @param code_src The input source code to interpret / run. Code ends either with \0 or EOF.
 * @param session_storage Can allocate and use arbitrary memory with this.
 * @param symbol_table The symbol table to use while processing.
 * @param code_stack The code stack (return addresses) to use.
 * @param data_stack The data stack (forth-like stack) to use.
 * @param insert_stack Used for temporarily expanding the input stream (one word level above current) with further words.
 * @param io_connector The engine uses this to open/close pipes/files and write/read them.
 * @param prefix The prefix added to the lookup of built-ins. Useful when you write a compiler with SLC. Defaults to "" (empty).
 * @param ender The character string that ends a word definition. Defaults to ";".
 * @param varprefix The character string that prefixes variable declarations. Defaults to "@".
 */
static inline void slc(
	coderead code_src,
	session session_storage,
	sym symbol_table,
	stack code_stack,
	stack data_stack,
	stack insert_stack,
	ioconn io_connector,
	const char *prefix,
	const char *ender,
	const char *varprefix
) {
	// TODO
}

#endif /* SLC_H */