path: root/gawkapi.h

/*
 * gawkapi.h -- Definitions for use by extension functions calling into gawk.
 */

/* 
 * Copyright (C) 2012, the Free Software Foundation, Inc.
 * 
 * This file is part of GAWK, the GNU implementation of the
 * AWK Programming Language.
 * 
 * GAWK 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
 * (at your option) any later version.
 * 
 * GAWK 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 this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 */

/*
 * N.B. You must include <sys/types.h> and <sys/stat.h>
 * before including this file!
 */

#ifndef _GAWK_API_H
#define _GAWK_API_H

/*
 * General introduction:
 *
 * This API purposely restricts itself to C90 features.
 * In paticular, no bool, no // comments, no use of the
 * restrict keyword, or anything else, in order to provide
 * maximal portability.
 */

/* Allow use in C++ code.  */
#ifdef __cplusplus
extern "C" {
#endif

/* struct used for reading records and managing buffers */
typedef struct iobuf {
	const char *name;       /* filename */
	int fd;                 /* file descriptor */
	struct stat sbuf;       /* stat buf */
	char *buf;              /* start data buffer */
	char *off;              /* start of current record in buffer */
	char *dataend;          /* first byte in buffer to hold new data,
				   NULL if not read yet */
	char *end;              /* end of buffer */
	size_t readsize;        /* set from fstat call */
	size_t size;            /* buffer size */
	ssize_t count;          /* amount read last time */
	size_t scanoff;         /* where we were in the buffer when we had
				   to regrow/refill */
	/*
	 * No argument prototype on read_func. See get_src_buf()
	 * in awkgram.y.
	 */
	ssize_t (*read_func)();

	void *opaque;		/* private data for open hooks */
	int (*get_record)(char **out, struct iobuf *, int *errcode);
	void (*close_func)(struct iobuf *);	/* open and close hooks */
	
	int errcode;

	int flag;
#		define	IOP_IS_TTY	1
#		define	IOP_NOFREE_OBJ	2
#		define  IOP_AT_EOF      4
#		define  IOP_CLOSED      8
#		define  IOP_AT_START    16
} IOBUF;

#define GAWK_API_MAJOR_VERSION	0
#define GAWK_API_MINOR_VERSION	0

#define DO_FLAGS_SIZE	6

/*
 * This tag defines the type of a value.
 * Values are associated with regular variables and with array elements.
 * Since arrays can be multidimensional (as can regular variables)
 * it's valid to have a "value" that is actually an array.
 */
typedef enum {
	AWK_UNDEFINED,
	AWK_NUMBER,
	AWK_STRING,
	AWK_ARRAY
} awk_valtype_t;

/*
 * A mutable string. Gawk owns the memory pointed to if it supplied
 * the value. Otherwise, it takes ownership of the memory pointed to.
 */
typedef struct {
	char *str;
	size_t len;
} awk_string_t;

/* Arrays are represented as an opaque type */
typedef void *awk_array_t;

/*
 * An awk value. The val_type tag indicates what
 * is in the union.
 */
typedef struct {
	awk_valtype_t	val_type;
	union {
		awk_string_t	s;
		double		d;
		awk_array_t	a;
	} u;
#define str_value	u.s
#define num_value	u.d
#define array_cookie	u.a
} awk_value_t;

/* possible kinds of function parameters */
typedef enum {
	AWK_PARAM_STRING,	/* expecting a scalar string */
	AWK_PARAM_NUMBER,	/* expecting a scalar number */
	AWK_PARAM_ARRAY,	/* expecting an array */
} awk_param_type_t;

/*
 * A "flattened" array element. Gawk produces an array of these.
 * ALL memory pointed to belongs to gawk. Individual elements may
 * be marked for deletion. New elements must be added individually,
 * one at a time, using the API for that purpose.
 */

typedef struct awk_element {
	/* convenience linked list pointer, not used by gawk */
	struct awk_element *next;
	enum {
		AWK_ELEMENT_DEFAULT = 0,	/* set by gawk */
		AWK_ELEMENT_DELETE = 1		/* set by extension if
						   should be deleted */
	} flags;
	awk_string_t	index;
	awk_value_t	value;
} awk_element_t;

/*
 * A record describing an extension function. Upon being
 * loaded, the extension should pass in one of these for
 * each C function.
 */
typedef struct {
	const char *name;
	int (*function)(int num_args_actual);
	size_t num_args_expected;
} awk_ext_func_t;

typedef int awk_bool_t;	/* we don't use <stdbool.h> on purpose */

typedef void *awk_ext_id_t;	/* opaque type for extension id */

/*
 * The API into gawk. Lots of functions here. We hope that they are
 * logically organized.
 */
typedef struct gawk_api {
	int major_version;
	int minor_version;

	int do_flags[DO_FLAGS_SIZE];
/* Use these as indices into do_flags[] array to check the values */
#define gawk_do_lint		0
#define gawk_do_traditional	1
#define gawk_do_profile		2
#define gawk_do_sandbox		3
#define gawk_do_debug		4
#define gawk_do_mpfr		5

	/*
	 * Get the count'th paramater, zero-based.
	 * Returns NULL if count is out of range, or if actual paramater
	 * does not match what is specified in wanted.
	 */
	awk_value_t *(*get_curfunc_param)(awk_ext_id_t id, size_t count,
					awk_param_type_t wanted);

	/* Set the return value. Gawk takes ownership of string memory */
	void (*set_return_value)(awk_ext_id_t id, const awk_value_t *retval);

	/* Functions to print messages */
	void (*api_fatal)(awk_ext_id_t id, const char *format, ...);
	void (*api_warning)(awk_ext_id_t id, const char *format, ...);
	void (*api_lintwarn)(awk_ext_id_t id, const char *format, ...);

	/* Register an open hook; for opening files read-only */
	void (*register_open_hook)(awk_ext_id_t id, void* (*open_func)(IOBUF *));

	/* Functions to update ERRNO */
	void (*update_ERRNO_int)(awk_ext_id_t id, int errno_val);
	void (*update_ERRNO_string)(awk_ext_id_t id, const char *string,
			awk_bool_t translate);
	void (*unset_ERRNO)(awk_ext_id_t id);

	/* Add a function to the interpreter, returns true upon success */
	awk_bool_t (*add_ext_func)(awk_ext_id_t id, const awk_ext_func_t *func,
			const char *namespace);

	/* Add an exit call back, returns true upon success */
	awk_bool_t (*awk_atexit)(awk_ext_id_t id,
			void (*funcp)(void *data, int exit_status),
			void *arg0);

	/*
	 * Symbol table access:
	 * 	- No access to special variables (NF, etc.)
	 * 	- One special exception: PROCINFO.
	 *	- Use sym_update() to change a value, including from UNDEFINED
	 *	  to scalar or array. 
	 */
	/*
	 * Lookup a variable, return its value. No messing with the value
	 * returned. Return value is NULL if the variable doesn't exist.
	 *
	 * Returns a pointer to a static variable. Correct usage is thus:
	 *
	 * 	awk_value_t val, *vp;
	 * 	vp = api->sym_lookup(id, name);
	 * 	if (vp == NULL)
	 * 		error_code();
	 *	val = *vp;
	 *	// use val from here on
	 */
	const awk_value_t *const (*sym_lookup)(awk_ext_id_t id, const char *name);

	/*
	 * Update a value. Adds it to the symbol table if not there.
	 * Changing types is not allowed.
	 */
	awk_bool_t (*sym_update)(awk_ext_id_t id, const char *name, awk_value_t *value);

	/* Array management */
	/*
	 * Return the value of an element - read only!
	 * Use set_array_element to change it.
	 *
	 * As for sym_lookup(), this also returns a static pointer whose
	 * value should be copied before use.
	 */
	const awk_value_t *const (*get_array_element)(awk_ext_id_t id,
			awk_array_t a_cookie, const awk_value_t *const index);

	/*
	 * Change (or create) element in existing array with
	 * element->index and element->value.
	 */
	awk_bool_t (*set_array_element)(awk_ext_id_t id, awk_array_t a_cookie,
					awk_element_t *element);

	/*
	 * Remove the element with the given index.
	 * Returns success if removed or if element did not exist.
	 */
	awk_bool_t (*del_array_element)(awk_ext_id_t id,
			awk_array_t a_cookie, const awk_value_t* const index);

	/*
	 * Retrieve total number of elements in array.
	 * Returns false if some kind of error.
	 */
	awk_bool_t (*get_element_count)(awk_ext_id_t id,
			awk_array_t a_cookie, size_t *count);

	/* Create a new array cookie to which elements may be added */
	awk_array_t (*create_array)(awk_ext_id_t id);

	/* Clear out an array */
	awk_bool_t (*clear_array)(awk_ext_id_t id, awk_array_t a_cookie);

	/* Flatten out an array so that it can be looped over easily. */
	awk_bool_t (*flatten_array)(awk_ext_id_t id,
			awk_array_t a_cookie,
			size_t *count,
			awk_element_t **data);

	/*
	 * When done, release the memory, delete any marked elements
	 * Count must match what gawk thinks the size is.
	 */
	awk_bool_t (*release_flattened_array)(awk_ext_id_t id,
			awk_array_t a_cookie,
			size_t count,
			awk_element_t *data);

	/* Constructor functions */
	awk_value_t *(*api_make_string)(awk_ext_id_t id,
			const char *string, size_t length, awk_bool_t duplicate);
	awk_value_t *(*api_make_number)(awk_ext_id_t id, double num);

} gawk_api_t;

#ifndef GAWK	/* these are not for the gawk code itself */
/*
 * Use these if you want to define a "global" variable named api
 * to make the code a little easier to read.
 */
#define do_lint		api->do_flags[gawk_do_lint]
#define do_traditional	api->do_flags[gawk_do_traditional]
#define do_profile	api->do_flags[gawk_do_profile]
#define do_sandbox	api->do_flags[gawk_do_sandbox]
#define do_debug	api->do_flags[gawk_do_debug]
#define do_mpfr		api->do_flags[gawk_do_mpfr]

#define get_curfunc_param(count, wanted) \
	api->get_curfunc_param(ext_id, count, wanted)

#define set_return_value(retval) \
	api->set_return_value(ext_id, retval)

#define fatal		api->api_fatal
#define warning		api->api_warning
#define lintwarn	api->api_lintwarn

#define register_open_hook(func)	api->register_open_hook(ext_id, func)

#define update_ERRNO_int(e)	api->update_ERRNO_int(ext_id, e)
#define update_ERRNO_string(str, translate) \
	api->update_ERRNO_string(ext_id, str, translate)
#define unset_ERRNO	api->unset_ERRNO

#define add_ext_func(func, ns)	api->add_ext_func(ext_id, func, ns)
#define awk_atexit(funcp, arg0)	api->awk_atexit(ext_id, funcp, arg0)

#define sym_lookup(name)	api->sym_lookup(ext_id, name)
#define sym_update(name, value) \
	api->sym_update(ext_id, name, value)

#define get_array_element(array, element) \
	api->get_array_element(ext_id, array, element)

#define set_array_element(array, element) \
	api->set_array_element(ext_id, array, element)

#define del_array_element(array, index) \
	api->del_array_element(ext_id, array, index)

#define get_element_count(array, count_p) \
	api->get_element_count(ext_id, array, count_p)

#define create_array()		api->create_array(ext_id)

#define clear_array(array)	api->clear_array(ext_id, array)

#define flatten_array(array, count, data) \
	api->flatten_array(ext_id, array, count, data)

#define release_flattened_array(array, count, data) \
	api->release_flattened_array(ext_id, array, count, data)

#define make_string(str, len)	api->api_make_string(ext_id, str, len, 0)
#define dup_string(str, len)	api->api_make_string(ext_id, str, len, 1)
#define make_number(num)	api->api_make_number(ext_id, num)

#define emalloc(pointer, type, size, message) \
	do { \
		if ((pointer = (type) malloc(size)) == 0) \
			fatal(ext_id, "malloc of %d bytes failed\n", size); \
	} while(0)

#endif /* GAWK */

/*
 * Each extension must define a function with this prototype:
 *
 *	int dl_load(gawk_api_t *api_p, awk_ext_id_t id)
 *
 * For the macros to work, the function should save api_p in a
 * global variable named 'api'. The return value should be zero
 * on failure and non-zero on success.
 */

extern int dl_load(const gawk_api_t *const api_p, awk_ext_id_t id);

#if 0
/* Boiler plate code: */
static gawk_api_t *const api;
static awk_ext_id_t ext_id;
static awk_ext_func_t func_table[] = {
	{ "name", do_name, 1 },
	/* ... */
};

dl_load_func(api, ext_id, func_table, some_name, "name_space_in_quotes")
#endif

#define dl_load_func(global_api_p, global_ext_id, func_table, module, name_space) \
int dl_load(const gawk_api_t *const api_p, awk_ext_id_t id)  \
{ \
	size_t i, j; \
	int errors = 0; \
 \
	if (api->major_version != GAWK_API_MAJOR_VERSION \
	    || api->minor_version < GAWK_API_MINOR_VERSION) { \
		fprintf(stderr, #module ": version mismatch with gawk!\n"); \
		fprintf(stderr, "\tmy version (%d, %d), gawk version (%d, %d)\n", \
			GAWK_API_MAJOR_VERSION, GAWK_API_MINOR_VERSION, \
			api->major_version, api->minor_version); \
		exit(1); \
	} \
 \
	global_api_p = api_p; \
	global_ext_id = id; \
\
	/* load functions */ \
	for (i = 0, j = sizeof(func_table) / sizeof(func_table[0]); i < j; i++) { \
		if (! add_ext_func(& func_table[i], name_space)) { \
			warning(ext_id, #module ": could not add %s\n", \
					func_table[i].name); \
			errors++; \
		} \
	} \
\
	return (errors == 0); \
}

#ifdef __cplusplus
}
#endif	/* C++ */

#endif /* _GAWK_API_H */