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|
/* ScummVM - Graphic Adventure Engine
*
* ScummVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the COPYRIGHT
* file distributed with this source distribution.
*
* This program 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 2
* of the License, or (at your option) any later version.
*
* This program 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.
*
*/
#include "glk/adrift/scare.h"
#include "glk/adrift/scprotos.h"
namespace Glk {
namespace Adrift {
/*
* Module notes:
*
* o The tokenizer doesn't differentiate between "&", "&&", and "and", but "&"
* is context sensitive -- either a logical and for numerics, or concaten-
* ation for strings. As a result, "&&" and "and" also work as string
* concatenators when used in string expressions. It may not be to spec,
* but we'll call this a "feature".
*/
/* Assorted definitions and constants. */
enum { MAX_NESTING_DEPTH = 32 };
static const sc_char NUL = '\0';
static const sc_char PERCENT = '%';
static const sc_char SINGLE_QUOTE = '\'';
static const sc_char DOUBLE_QUOTE = '"';
/*
* Tokens. Single character tokens are represented by their ascii value
* (0-255), others by values above 255. -1 represents a null token. Because
* '&' and '+' are context sensitive, the pseudo-token TOK_CONCATENATE
* serves to indicate string concatenation -- it's never returned by the
* tokenizer.
*/
enum
{ TOK_NONE = -1,
TOK_ADD = '+', TOK_SUBTRACT = '-', TOK_MULTIPLY = '*', TOK_DIVIDE = '/',
TOK_AND = '&', TOK_OR = '|',
TOK_LPAREN = '(', TOK_RPAREN = ')', TOK_COMMA = ',', TOK_POWER = '^',
TOK_EQUAL = '=', TOK_GREATER = '>', TOK_LESS = '<',
TOK_IDENT = 256,
TOK_INTEGER, TOK_STRING, TOK_VARIABLE, TOK_UMINUS, TOK_UPLUS,
TOK_MOD, TOK_NOT_EQUAL, TOK_GREATER_EQ, TOK_LESS_EQ, TOK_IF,
TOK_MIN, TOK_MAX, TOK_EITHER, TOK_RANDOM, TOK_INSTR, TOK_LEN, TOK_VAL,
TOK_ABS, TOK_UPPER, TOK_LOWER, TOK_PROPER, TOK_RIGHT, TOK_LEFT, TOK_MID,
TOK_STR, TOK_CONCATENATE,
TOK_EOS
};
/*
* Small tables tying multicharacter tokens strings to tokens. At present,
* the string lengths for names are not used.
*/
typedef struct
{
const sc_char *const name;
const sc_int length;
const sc_int token;
} sc_expr_multichar_t;
static const sc_expr_multichar_t FUNCTION_TOKENS[] = {
{"either", 6, TOK_EITHER},
{"proper", 6, TOK_PROPER}, {"pcase", 5, TOK_PROPER}, {"instr", 5, TOK_INSTR},
{"upper", 5, TOK_UPPER}, {"ucase", 5, TOK_UPPER},
{"lower", 5, TOK_LOWER}, {"lcase", 5, TOK_LOWER},
{"right", 5, TOK_RIGHT}, {"left", 4, TOK_LEFT},
{"rand", 4, TOK_RANDOM}, {"max", 3, TOK_MAX}, {"min", 3, TOK_MIN},
{"mod", 3, TOK_MOD}, {"abs", 3, TOK_ABS}, {"len", 3, TOK_LEN},
{"val", 3, TOK_VAL}, {"and", 3, TOK_AND}, {"mid", 3, TOK_MID},
{"str", 3, TOK_STR}, {"or", 2, TOK_OR}, {"if", 2, TOK_IF},
{NULL, 0, TOK_NONE}
};
static const sc_expr_multichar_t OPERATOR_TOKENS[] = {
{"&&", 2, TOK_AND}, {"||", 2, TOK_OR},
{"==", 2, TOK_EQUAL}, {"!=", 2, TOK_NOT_EQUAL},
{"<>", 2, TOK_NOT_EQUAL}, {">=", 2, TOK_GREATER_EQ}, {"<=", 2, TOK_LESS_EQ},
{NULL, 0, TOK_NONE}
};
/*
* expr_multichar_search()
*
* Multicharacter token table search, returns the matching token, or
* TOK_NONE if no match.
*/
static sc_int
expr_multichar_search (const sc_char *name, const sc_expr_multichar_t *table)
{
const sc_expr_multichar_t *entry;
/* Scan the table for a case-independent full string match. */
for (entry = table; entry->name; entry++)
{
if (sc_strcasecmp (name, entry->name) == 0)
break;
}
/* Return the token matched, or TOK_NONE. */
return entry->name ? entry->token : TOK_NONE;
}
/* Tokenizer variables. */
static const sc_char *expr_expression = NULL;
static sc_int expr_index = 0;
static sc_vartype_t expr_token_value;
static sc_char *expr_temporary = NULL;
static sc_int expr_current_token = TOK_NONE;
/*
* expr_tokenize_start()
* expr_tokenize_end()
*
* Start and wrap up expression string tokenization.
*/
static void
expr_tokenize_start (const sc_char *expression)
{
static sc_bool initialized = FALSE;
/* On first call only, verify the string lengths in the tables. */
if (!initialized)
{
const sc_expr_multichar_t *entry;
/* Compare table lengths with string lengths. */
for (entry = FUNCTION_TOKENS; entry->name; entry++)
{
if (entry->length != (sc_int) strlen (entry->name))
{
sc_fatal ("expr_tokenize_start:"
" token string length is wrong for \"%s\"\n",
entry->name);
}
}
for (entry = OPERATOR_TOKENS; entry->name; entry++)
{
if (entry->length != (sc_int) strlen (entry->name))
{
sc_fatal ("expr_tokenize_start:"
" operator string length is wrong for \"%s\"\n",
entry->name);
}
}
initialized = TRUE;
}
/* Save expression, and restart index. */
expr_expression = expression;
expr_index = 0;
/* Allocate a temporary token value/literals string. */
assert (!expr_temporary);
expr_temporary = (sc_char *)sc_malloc (strlen (expression) + 1);
/* Reset last token to none. */
expr_current_token = TOK_NONE;
}
static void
expr_tokenize_end (void)
{
/* Deallocate temporary strings, clear expression. */
sc_free (expr_temporary);
expr_temporary = NULL;
expr_expression = NULL;
expr_index = 0;
expr_current_token = TOK_NONE;
}
/*
* expr_next_token_unadjusted()
* expr_next_token()
*
* Return the next token from the current expression. The initial token may
* be adjusted into a unary +/- depending on the value of the previous token.
*/
static sc_int
expr_next_token_unadjusted (sc_vartype_t *token_value)
{
sc_int c;
assert (expr_expression);
/* Skip any and all leading whitespace. */
do
{
c = expr_expression[expr_index++];
}
while (sc_isspace (c) && c != NUL);
/* Return EOS if at expression end. */
if (c == NUL)
{
expr_index--;
return TOK_EOS;
}
/*
* Identify and return numerics. We deal only with unsigned numbers here;
* the unary +/- tokens take care of any integer sign issues.
*/
else if (sc_isdigit (c))
{
sc_int value;
sscanf (expr_expression + expr_index - 1, "%ld", &value);
while (sc_isdigit (c) && c != NUL)
c = expr_expression[expr_index++];
expr_index--;
token_value->integer = value;
return TOK_INTEGER;
}
/* Identify and return variable references. */
else if (c == PERCENT)
{
sc_int index_;
/* Copy variable name. */
c = expr_expression[expr_index++];
for (index_ = 0; c != PERCENT && c != NUL;)
{
expr_temporary[index_++] = c;
c = expr_expression[expr_index++];
}
expr_temporary[index_++] = NUL;
if (c == NUL)
{
sc_error ("expr_next_token_unadjusted:"
" warning: unterminated variable name\n");
expr_index--;
}
/* Return a variable name. */
token_value->string = expr_temporary;
return TOK_VARIABLE;
}
/* Identify and return string literals. */
else if (c == DOUBLE_QUOTE || c == SINGLE_QUOTE)
{
sc_int index_;
sc_char quote;
/* Copy maximal string literal. */
quote = c;
c = expr_expression[expr_index++];
for (index_ = 0; c != quote && c != NUL;)
{
expr_temporary[index_++] = c;
c = expr_expression[expr_index++];
}
expr_temporary[index_++] = NUL;
if (c == NUL)
{
sc_error ("expr_next_token_unadjusted:"
" warning: unterminated string literal\n");
expr_index--;
}
/* Return string literal. */
token_value->string = expr_temporary;
return TOK_STRING;
}
/* Identify ids and other multicharacter tokens. */
else if (sc_isalpha (c))
{
sc_int index_, token;
/*
* Copy maximal alphabetical string. While an ident would normally
* be alpha followed by zero or more alnum, for Adrift purposes we
* use only alpha -- all idents should really be "functions", and
* in particular we want to see "mod7" as "mod" and 7 separately.
*/
for (index_ = 0; sc_isalpha (c) && c != NUL;)
{
expr_temporary[index_++] = c;
c = expr_expression[expr_index++];
}
expr_index--;
expr_temporary[index_++] = NUL;
/*
* Check for a function name, and if known, return that, otherwise
* return a bare id.
*/
token = expr_multichar_search (expr_temporary, FUNCTION_TOKENS);
if (token == TOK_NONE)
{
token_value->string = expr_temporary;
return TOK_IDENT;
}
else
return token;
}
/*
* Last chance check for two-character (multichar) operators, and if none
* then return a single-character token.
*/
else
{
sc_char operator_[3];
sc_int token;
/*
* Build a two-character string. If we happen to be at the last
* expression character, we'll pick up the expression NUL into
* operator_[1], so no need to special case end of expression here.
*/
operator_[0] = c;
operator_[1] = expr_expression[expr_index];
operator_[2] = NUL;
/* Search for this two-character operator. */
if (operator_[0] != NUL && operator_[1] != NUL)
{
token = expr_multichar_search (operator_, OPERATOR_TOKENS);
if (token != TOK_NONE)
{
/* Matched, so advance expression index and return this token. */
expr_index++;
return token;
}
}
/*
* No match, or at last expression character; return a single character
* token.
*/
return c;
}
}
static sc_int
expr_next_token (void)
{
sc_int token;
sc_vartype_t token_value;
/*
* Get the basic next token. We may adjust it later for unary minus/plus
* depending on what it is, and the prior token.
*/
token_value.voidp = NULL;
token = expr_next_token_unadjusted (&token_value);
/* Special handling for unary minus/plus signs. */
if (token == TOK_SUBTRACT || token == TOK_ADD)
{
/*
* Unary minus/plus if prior token was an operator or a comparison, left
* parenthesis, or comma, or if there was no prior token.
*/
switch (expr_current_token)
{
case TOK_MOD:
case TOK_POWER:
case TOK_ADD:
case TOK_SUBTRACT:
case TOK_MULTIPLY:
case TOK_DIVIDE:
case TOK_AND:
case TOK_OR:
case TOK_EQUAL:
case TOK_GREATER:
case TOK_LESS:
case TOK_NOT_EQUAL:
case TOK_GREATER_EQ:
case TOK_LESS_EQ:
case TOK_LPAREN:
case TOK_COMMA:
case TOK_NONE:
token = (token == TOK_SUBTRACT) ? TOK_UMINUS : TOK_UPLUS;
break;
default:
break;
}
}
/* Set current token to the one just found, and return it. */
expr_current_token = token;
expr_token_value = token_value;
return token;
}
/*
* expr_current_token_value()
*
* Return the token value of the current token. Undefined if the current
* token is not numeric, an id, or a variable.
*/
static void
expr_current_token_value (sc_vartype_t *value)
{
/* Quick check that the value is a valid one. */
switch (expr_current_token)
{
case TOK_INTEGER:
case TOK_STRING:
case TOK_VARIABLE:
case TOK_IDENT:
break;
default:
sc_fatal ("expr_current_token_value:"
" taking undefined token value, %ld\n", expr_current_token);
}
/* Return value. */
*value = expr_token_value;
}
/*
* Evaluation values stack, uses a variable type so it can contain both
* integers and strings, and flags strings for possible garbage collection
* on parse errors.
*/
typedef struct
{
sc_bool is_collectible;
sc_vartype_t value;
} sc_stack_t;
static sc_stack_t expr_eval_stack[MAX_NESTING_DEPTH];
static sc_int expr_eval_stack_index = 0;
/* Variables set to reference for %...% values. */
static sc_var_setref_t expr_varset = NULL;
/*
* expr_eval_start()
*
* Reset the evaluation stack to an empty state, and register the variables
* set to use when referencing %...% variables.
*/
static void
expr_eval_start (sc_var_setref_t vars)
{
expr_eval_stack_index = 0;
expr_varset = vars;
}
/*
* expr_eval_garbage_collect()
*
* In case of parse error, empty out and free all collectible malloced
* strings left in the evaluation array.
*/
static void
expr_eval_garbage_collect (void)
{
sc_int index_;
/*
* Find and free all collectible strings still in the stack. We have to
* free through mutable string rather than const string.
*/
for (index_ = 0; index_ < expr_eval_stack_index; index_++)
{
if (expr_eval_stack[index_].is_collectible)
sc_free (expr_eval_stack[index_].value.mutable_string);
}
/* Reset the stack index, for clarity and neatness. */
expr_eval_stack_index = 0;
}
/*
* expr_eval_push_integer()
* expr_eval_push_string()
* expr_eval_push_alloced_string()
*
* Push a value onto the values stack. Strings are malloc'ed and copied,
* and the copy is placed onto the stack, unless _alloced_string() is used;
* for this case, the input string is assumed to be already malloc'ed, and
* the caller should not subsequently free the string.
*/
static void
expr_eval_push_integer (sc_int value)
{
if (expr_eval_stack_index >= MAX_NESTING_DEPTH)
sc_fatal ("expr_eval_push_integer: stack overflow\n");
expr_eval_stack[expr_eval_stack_index].is_collectible = FALSE;
expr_eval_stack[expr_eval_stack_index++].value.integer = value;
}
static void
expr_eval_push_string (const sc_char *value)
{
sc_char *value_copy;
if (expr_eval_stack_index >= MAX_NESTING_DEPTH)
sc_fatal ("expr_eval_push_string: stack overflow\n");
/* Push a copy of value. */
value_copy = (sc_char *)sc_malloc (strlen (value) + 1);
strcpy (value_copy, value);
expr_eval_stack[expr_eval_stack_index].is_collectible = TRUE;
expr_eval_stack[expr_eval_stack_index++].value.mutable_string = value_copy;
}
static void
expr_eval_push_alloced_string (sc_char *value)
{
if (expr_eval_stack_index >= MAX_NESTING_DEPTH)
sc_fatal ("expr_eval_push_alloced_string: stack overflow\n");
expr_eval_stack[expr_eval_stack_index].is_collectible = TRUE;
expr_eval_stack[expr_eval_stack_index++].value.mutable_string = value;
}
/*
* expr_eval_pop_integer()
* expr_eval_pop_string()
*
* Pop values off the values stack. Returned strings are malloc'ed copies,
* and the caller is responsible for freeing them.
*/
static sc_int
expr_eval_pop_integer (void)
{
if (expr_eval_stack_index == 0)
sc_fatal ("expr_eval_pop_integer: stack underflow\n");
assert (!expr_eval_stack[expr_eval_stack_index - 1].is_collectible);
return expr_eval_stack[--expr_eval_stack_index].value.integer;
}
static sc_char *
expr_eval_pop_string (void)
{
if (expr_eval_stack_index == 0)
sc_fatal ("expr_eval_pop_string: stack underflow\n");
/* Returns mutable string rather than const string. */
assert (expr_eval_stack[expr_eval_stack_index - 1].is_collectible);
return expr_eval_stack[--expr_eval_stack_index].value.mutable_string;
}
/*
* expr_eval_result()
*
* Return the top of the values stack as the expression result.
*/
static void
expr_eval_result (sc_vartype_t *vt_rvalue)
{
if (expr_eval_stack_index != 1)
sc_fatal ("expr_eval_result: values stack not completed\n");
/* Clear down stack and return the top value. */
expr_eval_stack_index = 0;
*vt_rvalue = expr_eval_stack[0].value;
}
/*
* expr_eval_abs()
*
* Return the absolute value of the given sc_int. Replacement for labs(),
* avoids tying sc_int to long types too closely.
*/
static sc_int
expr_eval_abs (sc_int value)
{
return value < 0 ? -value : value;
}
/* Parse error jump buffer. */
static jmp_buf expr_parse_error;
/*
* expr_eval_action()
*
* Evaluate the effect of a token into the values stack.
*/
static void
expr_eval_action (sc_int token)
{
sc_vartype_t token_value;
switch (token)
{
/* Handle tokens representing stack pushes. */
case TOK_INTEGER:
expr_current_token_value (&token_value);
expr_eval_push_integer (token_value.integer);
break;
case TOK_STRING:
expr_current_token_value (&token_value);
expr_eval_push_string (token_value.string);
break;
case TOK_VARIABLE:
{
sc_vartype_t vt_rvalue;
sc_int type;
expr_current_token_value (&token_value);
if (!var_get (expr_varset, token_value.string, &type, &vt_rvalue))
{
sc_error ("expr_eval_action:"
" undefined variable, %s\n", token_value.string);
longjmp (expr_parse_error, 1);
}
switch (type)
{
case VAR_INTEGER:
expr_eval_push_integer (vt_rvalue.integer);
break;
case VAR_STRING:
expr_eval_push_string (vt_rvalue.string);
break;
default:
sc_fatal ("expr_eval_action: bad variable type\n");
}
break;
}
/* Handle tokens representing functions returning numeric. */
case TOK_IF:
{
sc_int test, val1, val2;
/* Pop the test and alternatives, and push back result. */
val2 = expr_eval_pop_integer ();
val1 = expr_eval_pop_integer ();
test = expr_eval_pop_integer ();
expr_eval_push_integer (test ? val1 : val2);
break;
}
case TOK_MAX:
case TOK_MIN:
{
sc_int argument_count, index_, result;
/* Get argument count off the top of the stack. */
argument_count = expr_eval_pop_integer ();
assert (argument_count > 0);
/* Find the max or min of these stacked values. */
result = expr_eval_pop_integer ();
for (index_ = 1; index_ < argument_count; index_++)
{
sc_int next;
next = expr_eval_pop_integer ();
switch (token)
{
case TOK_MAX:
result = (next > result) ? next : result;
break;
case TOK_MIN:
result = (next < result) ? next : result;
break;
default:
sc_fatal ("expr_eval_action: bad token, %ld\n", token);
}
}
/* Push back the result. */
expr_eval_push_integer (result);
break;
}
case TOK_EITHER:
{
sc_int argument_count, pick, index_;
sc_int result = 0;
/* Get argument count off the top of the stack. */
argument_count = expr_eval_pop_integer ();
assert (argument_count > 0);
/*
* Pick one of the top N items at random, then unstack all N and
* push back the value of the one picked.
*/
pick = sc_rand () % argument_count;
for (index_ = 0; index_ < argument_count; index_++)
{
sc_int val;
val = expr_eval_pop_integer ();
if (index_ == pick)
result = val;
}
/* Push back the result. */
expr_eval_push_integer (result);
break;
}
case TOK_INSTR:
{
sc_char *val1, *val2, *search;
sc_int result;
/* Extract the two values to work on. */
val2 = expr_eval_pop_string ();
val1 = expr_eval_pop_string ();
/*
* Search for the second in the first. The result is the character
* position, starting at 1, or 0 if not found. Then free the popped
* strings, and push back the result.
*/
search = (val1[0] != NUL) ? strstr (val1, val2) : NULL;
result = (!search) ? 0 : search - val1 + 1;
sc_free (val1);
sc_free (val2);
expr_eval_push_integer (result);
break;
}
case TOK_LEN:
{
sc_char *val;
sc_int result;
/* Pop the top string, and push back its length. */
val = expr_eval_pop_string ();
result = strlen (val);
sc_free (val);
expr_eval_push_integer (result);
break;
}
case TOK_VAL:
{
sc_char *val;
sc_int result = 0;
/*
* Extract the string at stack top, and try to convert, returning
* zero if conversion fails. Free the popped string, and push back
* the result.
*/
val = expr_eval_pop_string ();
sscanf (val, "%ld", &result);
sc_free (val);
expr_eval_push_integer (result);
break;
}
/* Handle tokens representing unary numeric operations. */
case TOK_UMINUS:
expr_eval_push_integer (-(expr_eval_pop_integer ()));
break;
case TOK_UPLUS:
break;
case TOK_ABS:
expr_eval_push_integer (expr_eval_abs (expr_eval_pop_integer ()));
break;
/* Handle tokens representing most binary numeric operations. */
case TOK_ADD:
case TOK_SUBTRACT:
case TOK_MULTIPLY:
case TOK_AND:
case TOK_OR:
case TOK_EQUAL:
case TOK_GREATER:
case TOK_LESS:
case TOK_NOT_EQUAL:
case TOK_GREATER_EQ:
case TOK_LESS_EQ:
case TOK_RANDOM:
{
sc_int val1, val2, result = 0;
/* Extract the two values to work on. */
val2 = expr_eval_pop_integer ();
val1 = expr_eval_pop_integer ();
/* Generate the result value. */
switch (token)
{
case TOK_ADD:
result = val1 + val2;
break;
case TOK_SUBTRACT:
result = val1 - val2;
break;
case TOK_MULTIPLY:
result = val1 * val2;
break;
case TOK_AND:
result = val1 && val2;
break;
case TOK_OR:
result = val1 || val2;
break;
case TOK_EQUAL:
result = val1 == val2;
break;
case TOK_GREATER:
result = val1 > val2;
break;
case TOK_LESS:
result = val1 < val2;
break;
case TOK_NOT_EQUAL:
result = val1 != val2;
break;
case TOK_GREATER_EQ:
result = val1 >= val2;
break;
case TOK_LESS_EQ:
result = val1 <= val2;
break;
case TOK_RANDOM:
result = sc_randomint (val1, val2);
break;
default:
sc_fatal ("expr_eval_action: bad token, %ld\n", token);
}
/* Put result back at top of stack. */
expr_eval_push_integer (result);
break;
}
/* Handle division and modulus separately; they're "eccentric". */
case TOK_DIVIDE:
case TOK_MOD:
{
sc_int val1, val2, x, y, result = 0;
/* Extract the two values to work on, complain about division by 0. */
val2 = expr_eval_pop_integer ();
val1 = expr_eval_pop_integer ();
if (val2 == 0)
{
sc_error ("expr_eval_action: attempt to divide by zero\n");
expr_eval_push_integer (result);
break;
}
/*
* ANSI/ISO C only defines integer division for positive values.
* Negative values usually work consistently across platforms, but are
* not guaranteed. For maximum portability, then, here we'll work
* carefully with positive integers only.
*/
x = expr_eval_abs (val1);
y = expr_eval_abs (val2);
/* Generate the result value. */
switch (token)
{
case TOK_DIVIDE:
/*
* Adrift's division apparently works by dividing using floating
* point, then applying (asymmetrical) rounding, so we have to do
* the same here.
*/
result = ((val1 < 0) == (val2 < 0))
? ((x / y) + (((x % y) * 2 >= y) ? 1 : 0))
: -((x / y) + (((x % y) * 2 > y) ? 1 : 0));
break;
case TOK_MOD:
/*
* Adrift also breaks numerical consistency by defining mod in a
* conventional (non-rounded), way, so that A=(AdivB)*B+AmodB
* does not hold.
*/
result = (val1 < 0) ? -(x % y) : (x % y);
break;
default:
sc_fatal ("expr_eval_action: bad token, %ld\n", token);
}
/* Put result back at top of stack. */
expr_eval_push_integer (result);
break;
}
/* Handle power individually, to avoid needing a maths library. */
case TOK_POWER:
{
sc_int val1, val2, result;
/* Extract the two values to work on. */
val2 = expr_eval_pop_integer ();
val1 = expr_eval_pop_integer ();
/* Handle negative and zero power values first, as special cases. */
if (val2 == 0)
result = 1;
else if (val2 < 0)
{
if (val1 == 0)
{
sc_error ("expr_eval_action: attempt to divide by zero\n");
result = 0;
}
else if (val1 == 1)
result = val1;
else if (val1 == -1)
result = (-val2 & 1) ? val1 : -val1;
else
result = 0;
}
else
{
/* Raise to positive powers using the Russian Peasant algorithm. */
while ((val2 & 1) == 0)
{
val1 = val1 * val1;
val2 >>= 1;
}
result = val1;
val2 >>= 1;
while (val2 > 0)
{
val1 = val1 * val1;
if (val2 & 1)
result = result * val1;
val2 >>= 1;
}
}
/* Put result back at top of stack. */
expr_eval_push_integer (result);
break;
}
/* Handle tokens representing functions returning string. */
case TOK_LEFT:
case TOK_RIGHT:
{
sc_char *text;
sc_int length;
/*
* Extract the text and length. If length is longer than text, or
* negative, do nothing.
*/
length = expr_eval_pop_integer ();
text = expr_eval_pop_string ();
if (length < 0 || length >= (sc_int) strlen (text))
{
expr_eval_push_alloced_string (text);
break;
}
/*
* Take the left or right segment -- for left, the operation is a
* simple truncation; for right, it's a memmove.
*/
switch (token)
{
case TOK_LEFT:
text[length] = NUL;
break;
case TOK_RIGHT:
memmove (text, text + strlen (text) - length, length + 1);
break;
default:
sc_fatal ("expr_eval_action: bad token, %ld\n", token);
}
/* Put result back at top of stack. */
expr_eval_push_alloced_string (text);
break;
}
case TOK_MID:
{
sc_char *text;
sc_int length, start, limit;
/*
* Extract the text, start, and length, re-basing start from 1 to 0,
* and calculate the limit on characters available for the move.
*/
length = expr_eval_pop_integer ();
start = expr_eval_pop_integer () - 1;
text = expr_eval_pop_string ();
limit = strlen (text);
/*
* Clamp ranges that roam outside the available text -- start less
* than 0 to 0, and greater than len(text) to len(text), and length
* less than 0 to 0, and off string end to string end.
*/
if (start < 0)
start = 0;
else if (start > limit)
start = limit;
if (length < 0)
length = 0;
else if (length > limit - start)
length = limit - start;
/* Move substring, terminate, and put back at top of stack. */
memmove (text, text + start, length + 1);
text[length] = NUL;
expr_eval_push_alloced_string (text);
break;
}
case TOK_STR:
{
sc_int val;
sc_char buffer[32];
/*
* Extract the value, convert it, and push back the resulting string.
* The leading space on positive values matches the Runner.
*/
val = expr_eval_pop_integer ();
sprintf (buffer, "% ld", val);
expr_eval_push_string (buffer);
break;
}
/* Handle tokens representing unary string operations. */
case TOK_UPPER:
case TOK_LOWER:
case TOK_PROPER:
{
sc_char *text;
sc_int index_;
/* Extract the value to work on. */
text = expr_eval_pop_string ();
/* Convert the entire string in place -- it's malloc'ed. */
for (index_ = 0; text[index_] != NUL; index_++)
{
switch (token)
{
case TOK_UPPER:
text[index_] = sc_toupper (text[index_]);
break;
case TOK_LOWER:
text[index_] = sc_tolower (text[index_]);
break;
case TOK_PROPER:
if (index_ == 0 || sc_isspace (text[index_ - 1]))
text[index_] = sc_toupper (text[index_]);
else
text[index_] = sc_tolower (text[index_]);
break;
default:
sc_fatal ("expr_eval_action: bad token, %ld\n", token);
}
}
/* Put result back at top of stack. */
expr_eval_push_alloced_string (text);
break;
}
/* Handle token representing binary string operation. */
case TOK_CONCATENATE:
{
sc_char *text1, *text2;
/* Extract the two texts to work on. */
text2 = expr_eval_pop_string ();
text1 = expr_eval_pop_string ();
/*
* Resize text1 to be long enough for both, and concatenate, then
* free text2, and push back the concatenation.
*/
text1 = (sc_char *)sc_realloc (text1, strlen (text1) + strlen (text2) + 1);
strcat (text1, text2);
sc_free (text2);
expr_eval_push_alloced_string (text1);
break;
}
default:
sc_fatal ("expr_eval_action: bad token, %ld\n", token);
}
}
/* Predictive parser lookahead token. */
static sc_int expr_parse_lookahead = TOK_NONE;
/* Forward declaration of factor parsers and string expression parser. */
static void expr_parse_numeric_factor (void);
static void expr_parse_string_factor (void);
static void expr_parse_string_expr (void);
/*
* expr_parse_match()
*
* Match a token to the lookahead, then advance lookahead.
*/
static void
expr_parse_match (sc_int token)
{
if (expr_parse_lookahead == token)
expr_parse_lookahead = expr_next_token ();
else
{
/* Syntax error. */
sc_error ("expr_parse_match: syntax error,"
" expected %ld, got %ld\n", expr_parse_lookahead, token);
longjmp (expr_parse_error, 1);
}
}
/*
* Numeric operator precedence table. Operators are in order of precedence,
* with the highest being a factor. Each precedence entry permits several
* listed tokens. The end of the table (highest precedence) is marked by
* a list with no operators (although in practice we need to put a TOK_NONE
* in here since some C compilers won't accept { } as an empty initializer).
*/
typedef struct
{
const sc_int token_count;
const sc_int tokens[6];
} sc_precedence_entry_t;
#if 0
/*
* Conventional (BASIC, C) precedence table for the parser. Exponentiation
* has the highest precedence, then multiplicative operations, additive,
* comparisons, and boolean combiners.
*/
static const sc_precedence_entry_t PRECEDENCE_TABLE[] = {
{1, {TOK_OR}},
{1, {TOK_AND}},
{2, {TOK_EQUAL, TOK_NOT_EQUAL}},
{4, {TOK_GREATER, TOK_LESS, TOK_GREATER_EQ, TOK_LESS_EQ}},
{2, {TOK_ADD, TOK_SUBTRACT}},
{3, {TOK_MULTIPLY, TOK_DIVIDE, TOK_MOD}},
{1, {TOK_POWER}},
{0, {TOK_NONE}}
};
#else
/*
* Adrift-like precedence table for the parser. Exponentiation and modulus
* operations seem to be implemented at the same level as addition and
* subtraction, and boolean 'and' and 'or' have equal precedence.
*/
static const sc_precedence_entry_t PRECEDENCE_TABLE[] = {
{2, {TOK_OR, TOK_AND}},
{6, {TOK_EQUAL, TOK_NOT_EQUAL,
TOK_GREATER, TOK_LESS, TOK_GREATER_EQ, TOK_LESS_EQ}},
{4, {TOK_ADD, TOK_SUBTRACT, TOK_POWER, TOK_MOD}},
{2, {TOK_MULTIPLY, TOK_DIVIDE}},
{0, {TOK_NONE}}
};
#endif
/*
* expr_parse_contains_token()
*
* Helper for expr_parse_numeric_element(). Search the token list for the
* entry passed in, and return TRUE if it contains the given token.
*/
static int
expr_parse_contains_token (const sc_precedence_entry_t *entry, sc_int token)
{
sc_bool is_matched;
sc_int index_;
/* Search the entry's token list for the token passed in. */
is_matched = FALSE;
for (index_ = 0; index_ < entry->token_count; index_++)
{
if (entry->tokens[index_] == token)
{
is_matched = TRUE;
break;
}
}
return is_matched;
}
/*
* expr_parse_numeric_element()
*
* Parse numeric expression elements. This function uses the precedence table
* to match tokens, then decide whether, and how, to recurse into itself, or
* whether to parse a highest-precedence factor.
*/
static void
expr_parse_numeric_element (sc_int precedence)
{
const sc_precedence_entry_t *entry;
/* See if the level passed in has listed tokens. */
entry = PRECEDENCE_TABLE + precedence;
if (entry->token_count == 0)
{
/* Precedence levels that hit the table end are factors. */
expr_parse_numeric_factor ();
return;
}
/*
* Parse initial higher-precedence factor, then others that associate
* with the given level.
*/
expr_parse_numeric_element (precedence + 1);
while (expr_parse_contains_token (entry, expr_parse_lookahead))
{
sc_int token;
/* Note token and match, parse next level, then action this token. */
token = expr_parse_lookahead;
expr_parse_match (token);
expr_parse_numeric_element (precedence + 1);
expr_eval_action (token);
}
}
/*
* expr_parse_numeric_expr()
*
* Parse a complete numeric (sub-)expression.
*/
static void
expr_parse_numeric_expr (void)
{
/* Call the parser of the lowest precedence operators. */
expr_parse_numeric_element (0);
}
/*
* expr_parse_numeric_factor()
*
* Parse a numeric expression factor.
*/
static void
expr_parse_numeric_factor (void)
{
/* Handle factors based on lookahead token. */
switch (expr_parse_lookahead)
{
/* Handle straightforward factors first. */
case TOK_LPAREN:
expr_parse_match (TOK_LPAREN);
expr_parse_numeric_expr ();
expr_parse_match (TOK_RPAREN);
break;
case TOK_UMINUS:
expr_parse_match (TOK_UMINUS);
expr_parse_numeric_factor ();
expr_eval_action (TOK_UMINUS);
break;
case TOK_UPLUS:
expr_parse_match (TOK_UPLUS);
expr_parse_numeric_factor ();
break;
case TOK_INTEGER:
expr_eval_action (TOK_INTEGER);
expr_parse_match (TOK_INTEGER);
break;
case TOK_VARIABLE:
{
sc_vartype_t token_value, vt_rvalue;
sc_int type;
expr_current_token_value (&token_value);
if (!var_get (expr_varset, token_value.string, &type, &vt_rvalue))
{
sc_error ("expr_parse_numeric_factor:"
" undefined variable, %s\n", token_value.string);
longjmp (expr_parse_error, 1);
}
if (type != VAR_INTEGER)
{
sc_error ("expr_parse_numeric_factor:"
" string variable in numeric context, %s\n",
token_value.string);
longjmp (expr_parse_error, 1);
}
expr_eval_action (TOK_VARIABLE);
expr_parse_match (TOK_VARIABLE);
break;
}
/* Handle functions as factors. */
case TOK_ABS:
/* Parse as "abs (val)". */
expr_parse_match (TOK_ABS);
expr_parse_match (TOK_LPAREN);
expr_parse_numeric_expr ();
expr_parse_match (TOK_RPAREN);
expr_eval_action (TOK_ABS);
break;
case TOK_IF:
/* Parse as "if (boolean, val1, val2)". */
expr_parse_match (TOK_IF);
expr_parse_match (TOK_LPAREN);
expr_parse_numeric_expr ();
expr_parse_match (TOK_COMMA);
expr_parse_numeric_expr ();
expr_parse_match (TOK_COMMA);
expr_parse_numeric_expr ();
expr_parse_match (TOK_RPAREN);
expr_eval_action (TOK_IF);
break;
case TOK_RANDOM:
/* Parse as "random (low, high)". */
expr_parse_match (TOK_RANDOM);
expr_parse_match (TOK_LPAREN);
expr_parse_numeric_expr ();
expr_parse_match (TOK_COMMA);
expr_parse_numeric_expr ();
expr_parse_match (TOK_RPAREN);
expr_eval_action (TOK_RANDOM);
break;
case TOK_MAX:
case TOK_MIN:
case TOK_EITHER:
/* Parse as "<func> (val1[,val2[,val3...]]])". */
{
sc_int token, argument_count;
/* Match up the function name and opening parenthesis. */
token = expr_parse_lookahead;
expr_parse_match (token);
expr_parse_match (TOK_LPAREN);
/* Count variable number of arguments as they are stacked. */
expr_parse_numeric_expr ();
argument_count = 1;
while (expr_parse_lookahead == TOK_COMMA)
{
expr_parse_match (TOK_COMMA);
expr_parse_numeric_expr ();
argument_count++;
}
expr_parse_match (TOK_RPAREN);
/* Push additional value -- the count of arguments. */
expr_eval_push_integer (argument_count);
expr_eval_action (token);
break;
}
case TOK_INSTR:
/* Parse as "instr (val1, val2)". */
expr_parse_match (TOK_INSTR);
expr_parse_match (TOK_LPAREN);
expr_parse_string_expr ();
expr_parse_match (TOK_COMMA);
expr_parse_string_expr ();
expr_parse_match (TOK_RPAREN);
expr_eval_action (TOK_INSTR);
break;
case TOK_LEN:
/* Parse as "len (val)". */
expr_parse_match (TOK_LEN);
expr_parse_match (TOK_LPAREN);
expr_parse_string_expr ();
expr_parse_match (TOK_RPAREN);
expr_eval_action (TOK_LEN);
break;
case TOK_VAL:
/* Parse as "val (val)". */
expr_parse_match (TOK_VAL);
expr_parse_match (TOK_LPAREN);
expr_parse_string_expr ();
expr_parse_match (TOK_RPAREN);
expr_eval_action (TOK_VAL);
break;
case TOK_IDENT:
/* Unrecognized function-type token. */
sc_error ("expr_parse_numeric_factor: syntax error, unknown ident\n");
longjmp (expr_parse_error, 1);
default:
/* Syntax error. */
sc_error ("expr_parse_numeric_factor:"
" syntax error, unexpected token, %ld\n", expr_parse_lookahead);
longjmp (expr_parse_error, 1);
}
}
/*
* expr_parse_string_expr()
*
* Parse a complete string (sub-)expression.
*/
static void
expr_parse_string_expr (void)
{
/*
* Parse a string factor, then all repeated concatenations. Because the '+'
* and '&' are context sensitive, we have to invent/translate them into the
* otherwise unused TOK_CONCATENATE for evaluation.
*/
expr_parse_string_factor ();
while (expr_parse_lookahead == TOK_AND || expr_parse_lookahead == TOK_ADD)
{
expr_parse_match (expr_parse_lookahead);
expr_parse_string_factor ();
expr_eval_action (TOK_CONCATENATE);
}
}
/*
* expr_parse_string_factor()
*
* Parse a string expression factor.
*/
static void
expr_parse_string_factor (void)
{
/* Handle factors based on lookahead token. */
switch (expr_parse_lookahead)
{
/* Handle straightforward factors first. */
case TOK_LPAREN:
expr_parse_match (TOK_LPAREN);
expr_parse_string_expr ();
expr_parse_match (TOK_RPAREN);
break;
case TOK_STRING:
expr_eval_action (TOK_STRING);
expr_parse_match (TOK_STRING);
break;
case TOK_VARIABLE:
{
sc_vartype_t token_value, vt_rvalue;
sc_int type;
expr_current_token_value (&token_value);
if (!var_get (expr_varset, token_value.string, &type, &vt_rvalue))
{
sc_error ("expr_parse_string_factor:"
" undefined variable, %s\n", token_value.string);
longjmp (expr_parse_error, 1);
}
if (type != VAR_STRING)
{
sc_error ("expr_parse_string_factor:"
" numeric variable in string context, %s\n",
token_value.string);
longjmp (expr_parse_error, 1);
}
expr_eval_action (TOK_VARIABLE);
expr_parse_match (TOK_VARIABLE);
break;
}
/* Handle functions as factors. */
case TOK_UPPER:
case TOK_LOWER:
case TOK_PROPER:
/* Parse as "<func> (text)". */
{
sc_int token;
token = expr_parse_lookahead;
expr_parse_match (token);
expr_parse_match (TOK_LPAREN);
expr_parse_string_expr ();
expr_parse_match (TOK_RPAREN);
expr_eval_action (token);
break;
}
case TOK_LEFT:
case TOK_RIGHT:
/* Parse as "<func> (text,length)". */
{
sc_int token;
token = expr_parse_lookahead;
expr_parse_match (token);
expr_parse_match (TOK_LPAREN);
expr_parse_string_expr ();
expr_parse_match (TOK_COMMA);
expr_parse_numeric_expr ();
expr_parse_match (TOK_RPAREN);
expr_eval_action (token);
break;
}
case TOK_MID:
/* Parse as "mid (text,start,length)". */
expr_parse_match (TOK_MID);
expr_parse_match (TOK_LPAREN);
expr_parse_string_expr ();
expr_parse_match (TOK_COMMA);
expr_parse_numeric_expr ();
expr_parse_match (TOK_COMMA);
expr_parse_numeric_expr ();
expr_parse_match (TOK_RPAREN);
expr_eval_action (TOK_MID);
break;
case TOK_STR:
/* Parse as "str (val)". */
expr_parse_match (TOK_STR);
expr_parse_match (TOK_LPAREN);
expr_parse_numeric_expr ();
expr_parse_match (TOK_RPAREN);
expr_eval_action (TOK_STR);
break;
case TOK_IDENT:
/* Unrecognized function-type token. */
sc_error ("expr_parse_string_factor: syntax error, unknown ident\n");
longjmp (expr_parse_error, 1);
default:
/* Syntax error. */
sc_error ("expr_parse_string_factor:"
" syntax error, unexpected token, %ld\n", expr_parse_lookahead);
longjmp (expr_parse_error, 1);
}
}
/*
* expr_evaluate_expression()
*
* Parse a string expression into a runtime values stack. Return the
* value of the expression.
*/
static sc_bool
expr_evaluate_expression (const sc_char *expression, sc_var_setref_t vars,
sc_int assign_type, sc_vartype_t *vt_rvalue)
{
assert (assign_type == VAR_INTEGER || assign_type == VAR_STRING);
/* Reset values stack and start tokenizer. */
expr_eval_start (vars);
expr_tokenize_start (expression);
/* Try parsing an expression, and catch errors. */
if (setjmp (expr_parse_error) == 0)
{
/* Parse an expression, and ensure it ends at string end. */
expr_parse_lookahead = expr_next_token ();
if (assign_type == VAR_STRING)
expr_parse_string_expr ();
else
expr_parse_numeric_expr ();
expr_parse_match (TOK_EOS);
}
else
{
/* Parse error -- clean up tokenizer, collect garbage, and fail. */
expr_tokenize_end ();
expr_eval_garbage_collect ();
return FALSE;
}
/* Clean up tokenizer and return successfully with result. */
expr_tokenize_end ();
expr_eval_result (vt_rvalue);
return TRUE;
}
/*
* expr_eval_numeric_expression()
* expr_eval_string_expression()
*
* Public interfaces to expression evaluation. Evaluate an expression, and
* assign the result to either a numeric or a string. For string expressions,
* the return value is malloc'ed, and the caller is responsible for freeing
* it.
*/
sc_bool
expr_eval_numeric_expression (const sc_char *expression,
sc_var_setref_t vars, sc_int *rvalue)
{
sc_vartype_t vt_rvalue;
sc_bool status;
assert (expression && vars && rvalue);
/* Evaluate numeric expression, and return value if valid. */
status = expr_evaluate_expression (expression, vars, VAR_INTEGER, &vt_rvalue);
if (status)
*rvalue = vt_rvalue.integer;
return status;
}
sc_bool
expr_eval_string_expression (const sc_char *expression,
sc_var_setref_t vars, sc_char **rvalue)
{
sc_vartype_t vt_rvalue;
sc_bool status;
assert (expression && vars && rvalue);
/* Evaluate string expression, and return value if valid. */
status = expr_evaluate_expression (expression, vars, VAR_STRING, &vt_rvalue);
if (status)
*rvalue = vt_rvalue.mutable_string;
return status;
}
} // End of namespace Adrift
} // End of namespace Glk
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