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ell/ell.c

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#define _XOPEN_SOURCE 500
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>
#include <stdarg.h>
#include <assert.h>
#include <time.h>
#include <stdbool.h>
#include <strings.h>
#include <math.h>
#if defined __GNUC__
#define ATTRIBUTE_PRINTF(x, y) __attribute__ ((format (printf, x, y)))
#else // ! __GNUC__
#define ATTRIBUTE_PRINTF(x, y)
#endif // ! __GNUC__
#define N_ELEMENTS(a) (sizeof (a) / sizeof ((a)[0]))
// --- Utilities ---------------------------------------------------------------
static char *format (const char *format, ...) ATTRIBUTE_PRINTF (1, 2);
static char *
strdup_vprintf (const char *format, va_list ap) {
va_list aq;
va_copy (aq, ap);
int size = vsnprintf (NULL, 0, format, aq);
va_end (aq);
if (size < 0)
return NULL;
char buf[size + 1];
size = vsnprintf (buf, sizeof buf, format, ap);
if (size < 0)
return NULL;
return strdup (buf);
}
static char *
format (const char *format, ...) {
va_list ap;
va_start (ap, format);
char *result = strdup_vprintf (format, ap);
va_end (ap);
return result;
}
// --- Generic buffer ----------------------------------------------------------
struct buffer {
char *s; ///< Buffer data
size_t alloc; ///< Number of bytes allocated
size_t len; ///< Number of bytes used
bool memory_failure; ///< Memory allocation failed
};
#define BUFFER_INITIALIZER { NULL, 0, 0, false }
static bool
buffer_append (struct buffer *self, const void *s, size_t n) {
if (self->memory_failure)
return false;
if (!self->s)
self->s = malloc (self->alloc = 8);
while (self->len + n > self->alloc)
self->s = realloc (self->s, self->alloc <<= 1);
if (!self->s) {
self->memory_failure = true;
return false;
}
memcpy (self->s + self->len, s, n);
self->len += n;
return true;
}
inline static bool
buffer_append_c (struct buffer *self, char c) {
return buffer_append (self, &c, 1);
}
// --- Data types --------------------------------------------------------------
enum item_type { ITEM_STRING, ITEM_LIST };
struct item {
enum item_type type; ///< The type of this object
struct item *next; ///< Next item on the list/stack
struct item *head; ///< The head of the list
size_t len; ///< Length of the string (sans '\0')
char value[]; ///< The null-terminated string value
};
const char *
item_type_to_str (enum item_type type) {
switch (type) {
case ITEM_STRING: return "string";
case ITEM_LIST: return "list";
}
abort ();
}
// --- Item management ---------------------------------------------------------
static void item_free_list (struct item *);
static struct item *new_clone_list (const struct item *);
static void
item_free (struct item *item) {
if (item->type == ITEM_LIST)
item_free_list (get_list (item));
free (item);
}
static void
item_free_list (struct item *item) {
while (item) {
struct item *link = item;
item = item->next;
item_free (link);
}
}
static struct item *
new_clone (const struct item *item) {
size_t size = sizeof *item;
if (item->type == ITEM_STRING)
size += item->len + 1;
struct item *clone = malloc (size);
if (!clone)
return NULL;
memcpy (clone, item, size);
if (item->type == ITEM_LIST) {
if (clone->head && !(clone->head = new_clone_list (clone->head))) {
free (clone);
return NULL;
}
}
clone->next = NULL;
return clone;
}
static struct item *
new_clone_list (const struct item *item) {
struct item *head = NULL, *clone;
for (struct item **out = &head; item; item = item->next) {
if (!(clone = *out = new_clone (item))) {
item_free_list (head);
return NULL;
}
clone->next = NULL;
out = &clone->next;
}
return head;
}
static struct item *
new_string (const char *s, ssize_t len) {
if (len < 0)
len = strlen (s);
struct item *item = calloc (1, sizeof *item + len + 1);
if (!item)
return NULL;
item->type = ITEM_STRING;
item->len = len;
memcpy (item->value, s, len);
item->value[len] = '\0';
return item;
}
static struct item *
new_list (struct item *head) {
struct item *item = calloc (1, sizeof *item);
if (!item)
return NULL;
item->type = ITEM_LIST;
item->head = head;
return item;
}
// --- Lexer -------------------------------------------------------------------
enum token {
T_ABORT, ///< EOF or error
T_LPAREN, ///< Left parenthesis
T_RPAREN, ///< Right parenthesis
T_LBRACKET, ///< Left bracket
T_RBRACKET, ///< Right bracket
T_LBRACE, ///< Left curly bracket
T_RBRACE, ///< Right curly bracket
T_STRING, ///< Everything else that's not space
T_NEWLINE, ///< New line
T_AT ///< At symbol
};
static const char *
token_name (enum token token) {
switch (token) {
case T_ABORT: return "end of input";
case T_LPAREN: return "left parenthesis";
case T_RPAREN: return "right parenthesis";
case T_LBRACKET: return "left bracket";
case T_RBRACKET: return "right bracket";
case T_LBRACE: return "left brace";
case T_RBRACE: return "right brace";
case T_STRING: return "string";
case T_NEWLINE: return "newline";
case T_AT: return "at symbol";
default:
abort ();
return NULL;
}
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
struct lexer {
const char *p; ///< Current position in input
size_t len; ///< How many bytes of input are left
unsigned line; ///< Current line
unsigned column; ///< Current column
int64_t integer; ///< Parsed boolean or integer value
struct str string; ///< Parsed string value
};
/// Input has to be null-terminated anyway
static void
lexer_init (struct lexer *self, const char *p, size_t len) {
memset (self, 0, sizeof *self);
self->p = p;
self->len = len;
str_init (&self->string);
}
static void
lexer_free (struct lexer *self) {
str_free (&self->string);
}
static bool lexer_is_word_char (int c) { return !strchr ("()[]{}\n@#'", c); }
static int
lexer_advance (struct lexer *self) {
int c = *self->p++;
if (c == '\n') {
self->column = 0;
self->line++;
} else
self->column++;
self->len--;
return c;
}
static void lexer_error (struct lexer *self,
struct error **e, const char *format, ...) ATTRIBUTE_PRINTF (3, 4);
static void
lexer_error (struct lexer *self, struct error **e, const char *format, ...) {
struct str description;
str_init (&description);
va_list ap;
va_start (ap, format);
str_append_vprintf (&description, format, ap);
va_end (ap);
if (self->report_line)
error_set (e, "near line %u, column %u: %s",
self->line + 1, self->column + 1, description.str);
else if (self->len)
error_set (e, "near character %u: %s",
self->column + 1, description.str);
else
error_set (e, "near end: %s", description.str);
str_free (&description);
}
static bool
lexer_hexa_escape (struct lexer *self, struct str *output) {
int i;
unsigned char code = 0;
for (i = 0; self->len && i < 2; i++) {
unsigned char c = tolower (*self->p);
if (c >= '0' && c <= '9')
code = (code << 4) | (c - '0');
else if (c >= 'a' && c <= 'f')
code = (code << 4) | (c - 'a' + 10);
else
break;
lexer_advance (self);
}
if (!i)
return false;
str_append_c (output, code);
return true;
}
static bool
lexer_escape_sequence
(struct lexer *self, struct str *output, struct error **e) {
if (!self->len) {
lexer_error (self, e, "premature end of escape sequence");
return false;
}
unsigned char c;
switch ((c = *self->p)) {
case '"': break;
case '\\': break;
case 'a': c = '\a'; break;
case 'b': c = '\b'; break;
case 'f': c = '\f'; break;
case 'n': c = '\n'; break;
case 'r': c = '\r'; break;
case 't': c = '\t'; break;
case 'v': c = '\v'; break;
case 'x':
case 'X':
lexer_advance (self);
if (lexer_hexa_escape (self, output))
return true;
lexer_error (self, e, "invalid hexadecimal escape");
return false;
default:
lexer_error (self, e, "unknown escape sequence");
return false;
}
str_append_c (output, c);
lexer_advance (self);
return true;
}
static bool
lexer_string (struct lexer *self, struct str *output, struct error **e) {
unsigned char c;
while (self->len) {
if ((c = lexer_advance (self)) == '\'')
return true;
if (c != '\\')
str_append_c (output, c);
else if (!lexer_escape_sequence (self, output, e))
return false;
}
lexer_error (self, e, "premature end of string");
return false;
}
static enum token
lexer_next (struct lexer *self, struct error **e) {
// Skip over any whitespace between tokens
while (self->len && isspace_ascii (*self->p) && *self->p != '\n')
lexer_advance (self);
if (!self->len)
return T_ABORT;
switch (*self->p) {
case '(': lexer_advance (self); return T_LPAREN;
case ')': lexer_advance (self); return T_RPAREN;
case '[': lexer_advance (self); return T_LBRACKET;
case ']': lexer_advance (self); return T_RBRACKET;
case '{': lexer_advance (self); return T_LBRACE;
case '}': lexer_advance (self); return T_RBRACE;
case '\n': lexer_advance (self); return T_NEWLINE;
case '@': lexer_advance (self); return T_AT;
case '#':
// Comments go until newline
while (self->len)
if (lexer_advance (self) == '\n')
return T_NEWLINE;
return T_ABORT;
case '\'':
lexer_advance (self);
str_reset (&self->string);
if (!lexer_string (self, &self->string, e))
return T_ABORT;
return T_STRING;
}
assert (lexer_is_word_char (*self->p));
str_reset (&self->string);
do
str_append_c (&self->string, lexer_advance (self));
while (lexer_is_word_char (*self->p));
return T_STRING;
}
// --- Parsing -----------------------------------------------------------------
#define PARSE_ERROR_TABLE(XX) \
XX( OK, NULL ) \
XX( EOF, "unexpected end of input" ) \
XX( INVALID_HEXA_ESCAPE, "invalid hexadecimal escape sequence" ) \
XX( INVALID_ESCAPE, "unrecognized escape sequence" ) \
XX( MEMORY, "memory allocation failure" ) \
XX( FLOAT_RANGE, "floating point value out of range" ) \
XX( INTEGER_RANGE, "integer out of range" ) \
XX( INVALID_INPUT, "invalid input" ) \
XX( UNEXPECTED_INPUT, "unexpected input" )
enum tokenizer_error {
#define XX(x, y) PARSE_ERROR_ ## x,
PARSE_ERROR_TABLE (XX)
#undef XX
PARSE_ERROR_COUNT
};
struct tokenizer {
const char *cursor;
enum tokenizer_error error;
};
static bool
decode_hexa_escape (struct tokenizer *self, struct buffer *buf) {
int i;
char c, code = 0;
for (i = 0; i < 2; i++) {
c = tolower (*self->cursor);
if (c >= '0' && c <= '9')
code = (code << 4) | (c - '0');
else if (c >= 'a' && c <= 'f')
code = (code << 4) | (c - 'a' + 10);
else
break;
self->cursor++;
}
if (!i)
return false;
buffer_append_c (buf, code);
return true;
}
static bool
decode_escape_sequence (struct tokenizer *self, struct buffer *buf) {
// Support some basic escape sequences from the C language
char c;
switch ((c = *self->cursor)) {
case '\0':
self->error = PARSE_ERROR_EOF;
return false;
case 'x':
case 'X':
self->cursor++;
if (decode_hexa_escape (self, buf))
return true;
self->error = PARSE_ERROR_INVALID_HEXA_ESCAPE;
return false;
default:
self->cursor++;
const char *from = "abfnrtv\"\\", *to = "\a\b\f\n\r\t\v\"\\", *x;
if ((x = strchr (from, c))) {
buffer_append_c (buf, to[x - from]);
return true;
}
self->error = PARSE_ERROR_INVALID_ESCAPE;
return false;
}
}
static struct item *
parse_string (struct tokenizer *self) {
struct buffer buf = BUFFER_INITIALIZER;
struct item *item = NULL;
char c;
while (true)
switch ((c = *self->cursor++)) {
case '\0':
self->cursor--;
self->error = PARSE_ERROR_EOF;
goto end;
case '"':
if (buf.memory_failure
|| !(item = new_string (buf.s, buf.len)))
self->error = PARSE_ERROR_MEMORY;
goto end;
case '\\':
if (decode_escape_sequence (self, &buf))
break;
goto end;
default:
buffer_append_c (&buf, c);
}
end:
free (buf.s);
return item;
}
static struct item *
parse_word (struct tokenizer *self) {
struct buffer buf = BUFFER_INITIALIZER;
struct item *item = NULL;
char c;
// Here we accept almost anything that doesn't break the grammar
while (!strchr (" []\"", (c = *self->cursor++)) && (unsigned char) c > ' ')
buffer_append_c (&buf, c);
self->cursor--;
if (buf.memory_failure)
self->error = PARSE_ERROR_MEMORY;
else if (!buf.len)
self->error = PARSE_ERROR_INVALID_INPUT;
else if (!(item = new_word (buf.s, buf.len)))
self->error = PARSE_ERROR_MEMORY;
free (buf.s);
return item;
}
static struct item *parse_item_list (struct tokenizer *);
static struct item *
parse_list (struct tokenizer *self) {
struct item *list = parse_item_list (self);
if (self->error) {
assert (list == NULL);
return NULL;
}
if (!*self->cursor) {
self->error = PARSE_ERROR_EOF;
item_free_list (list);
return NULL;
}
assert (*self->cursor == ']');
self->cursor++;
return new_list (list);
}
static struct item *
parse_item (struct tokenizer *self) {
char c;
switch ((c = *self->cursor++)) {
case '[': return parse_list (self);
case '"': return parse_string (self);
default:;
}
self->cursor--;
return parse_word (self);
}
static struct item *
parse_item_list (struct tokenizer *self) {
struct item *head = NULL;
struct item **tail = &head;
char c;
bool expected = true;
while ((c = *self->cursor) && c != ']') {
if (isspace (c)) {
self->cursor++;
expected = true;
continue;
} else if (!expected) {
self->error = PARSE_ERROR_UNEXPECTED_INPUT;
goto fail;
}
if (!(*tail = parse_item (self)))
goto fail;
tail = &(*tail)->next;
expected = false;
}
return head;
fail:
item_free_list (head);
return NULL;
}
static struct item *
parse (const char *s, const char **error) {
struct tokenizer self = { .cursor = s, .error = PARSE_ERROR_OK };
struct item *list = parse_item_list (&self);
if (!self.error && *self.cursor != '\0') {
self.error = PARSE_ERROR_UNEXPECTED_INPUT;
item_free_list (list);
list = NULL;
}
#define XX(x, y) y,
static const char *strings[PARSE_ERROR_COUNT] =
{ PARSE_ERROR_TABLE (XX) };
#undef XX
static char error_buf[128];
if (self.error && error) {
snprintf (error_buf, sizeof error_buf, "at character %d: %s",
(int) (self.cursor - s) + 1, strings[self.error]);
*error = error_buf;
}
return list;
}
// --- Runtime -----------------------------------------------------------------
struct context {
struct item *stack; ///< The current top of the stack
size_t stack_size; ///< Number of items on the stack
char *error; ///< Error information
bool error_is_fatal; ///< Whether the error can be catched
bool memory_failure; ///< Memory allocation failure
void *user_data; ///< User data
};
/// Internal handler for a function
typedef bool (*handler_fn) (struct context *);
struct fn {
struct fn *next; ///< The next link in the chain
handler_fn handler; ///< Internal C handler, or NULL
struct item *script; ///< Alternatively runtime code
char name[]; ///< The name of the function
};
struct fn *g_functions; ///< Maps words to functions
static void
context_init (struct context *ctx) {
ctx->stack = NULL;
ctx->stack_size = 0;
ctx->error = NULL;
ctx->error_is_fatal = false;
ctx->memory_failure = false;
ctx->user_data = NULL;
}
static void
context_free (struct context *ctx) {
item_free_list (ctx->stack);
ctx->stack = NULL;
free (ctx->error);
ctx->error = NULL;
}
static bool
set_error (struct context *ctx, const char *format, ...) {
free (ctx->error);
va_list ap;
va_start (ap, format);
ctx->error = strdup_vprintf (format, ap);
va_end (ap);
if (!ctx->error)
ctx->memory_failure = true;
return false;
}
static bool
push (struct context *ctx, struct item *item) {
// The `item' is typically a result from new_<type>(), thus when it is null,
// that function must have failed. This is a shortcut for convenience.
if (!item) {
ctx->memory_failure = true;
return false;
}
assert (item->next == NULL);
item->next = ctx->stack;
ctx->stack = item;
ctx->stack_size++;
return true;
}
static bool execute (struct context *, struct item *);
static bool
call_function (struct context *ctx, const char *name) {
struct fn *iter;
for (iter = g_functions; iter; iter = iter->next)
if (!strcmp (name, iter->name))
goto found;
return set_error (ctx, "unknown function: %s", name);
found:
if (iter->handler
? iter->handler (ctx)
: execute (ctx, iter->script))
return true;
// In this case, `error' is NULL
if (ctx->memory_failure)
return false;
// This creates some form of a stack trace
char *tmp = ctx->error;
ctx->error = NULL;
set_error (ctx, "%s -> %s", name, tmp);
free (tmp);
return false;
}
static void
free_function (struct fn *fn) {
item_free_list (fn->script);
free (fn);
}
static void
unregister_function (const char *name) {
for (struct fn **iter = &g_functions; *iter; iter = &(*iter)->next)
if (!strcmp ((*iter)->name, name)) {
struct fn *tmp = *iter;
*iter = tmp->next;
free_function (tmp);
break;
}
}
static struct fn *
prepend_new_fn (const char *name) {
struct fn *fn = calloc (1, sizeof *fn + strlen (name) + 1);
if (!fn)
return NULL;
strcpy (fn->name, name);
fn->next = g_functions;
return g_functions = fn;
}
static bool
register_handler (const char *name, handler_fn handler) {
unregister_function (name);
struct fn *fn = prepend_new_fn (name);
if (!fn)
return false;
fn->handler = handler;
return true;
}
static bool
register_script (const char *name, struct item *script) {
unregister_function (name);
struct fn *fn = prepend_new_fn (name);
if (!fn)
return false;
fn->script = script;
return true;
}
static bool
execute (struct context *ctx, struct item *script) {
for (; script; script = script->next) {
if (script->type != ITEM_STRING) {
if (!push (ctx, new_clone (script)))
return false;
}
else if (!call_function (ctx, get_word (script)))
return false;
}
return true;
}
// --- Runtime library ---------------------------------------------------------
#define defn(name) static bool name (struct context *ctx)
static bool
init_runtime_library_scripts (void) {
bool ok = true;
// It's much cheaper (and more fun) to define functions in terms of other
// ones. The "unit tests" serve a secondary purpose of showing the usage.
struct script {
const char *name; ///< Name of the function
const char *definition; ///< The defining script
} scripts[] = {
{ "greet", "print (.. 'hello ' (.. @1))" },
};
for (size_t i = 0; i < N_ELEMENTS (scripts); i++) {
const char *error = NULL;
struct item *script = parse (scripts[i].definition, &error);
if (error) {
printf ("error parsing internal script `%s': %s\n",
scripts[i].definition, error);
ok = false;
} else
ok &= register_script (scripts[i].name, script);
}
return ok;
}
defn (fn_print) {
check_stack (1);
struct item *item = pop (ctx);
struct user_info *info = ctx->user_data;
struct buffer buf = BUFFER_INITIALIZER;
item_to_str (item, &buf);
item_free (item);
buffer_append_c (&buf, '\0');
if (buf.memory_failure) {
ctx->memory_failure = true;
return false;
}
printf ("%s\n", buf.s);
free (buf.s);
return true;
}
defn (fn_concatenate) {
// TODO: concatenate string arguments, error on list
return true;
}
static bool
init_runtime_library (void)
{
return register_handler ("..", fn_concatenate);
&& register_handler ("print", fn_print);
&& init_runtime_library_scripts ();
}
static void
free_runtime_library (void) {
struct fn *next, *iter;
for (iter = g_functions; iter; iter = next) {
next = iter->next;
free_function (iter);
}
}
// --- Main --------------------------------------------------------------------
static void
process_message (const char *msg) {
// Finally parse and execute the macro
const char *error = NULL;
struct item *script = parse (msg, &error);
if (error) {
printf ("%s: %s\r\n", "parse error", error);
goto end;
}
struct context ctx;
context_init (&ctx);
ctx.user_data = &info;
execute (&ctx, script);
item_free_list (script);
const char *failure = NULL;
if (ctx.memory_failure)
failure = "memory allocation failure";
else if (ctx.error)
failure = ctx.error;
if (failure)
printf ("%s: %s\r\n", "runtime error", failure);
context_free (&ctx);
end:
free (msg_ctx_quote);
}
int
main (int argc, char *argv[]) {
freopen (NULL, "rb", stdin); setvbuf (stdin, NULL, _IOLBF, BUFSIZ);
freopen (NULL, "wb", stdout); setvbuf (stdout, NULL, _IOLBF, BUFSIZ);
if (!init_runtime_library ()
|| !register_handler (".", fn_dot))
printf ("%s\n", "runtime library initialization failed");
// TODO: load the entirety of stdin and execute it
process_message ("print 'hello world\n'");
free_runtime_library ();
return 0;
}
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