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redis/expr.c

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/* Filtering of objects based on simple expressions.
* This powers the FILTER option of Vector Sets, but it is otherwise
* general code to be used when we want to tell if a given object (with fields)
* passes or fails a given test for scalars, strings, ...
*
* Copyright(C) 2024-2025 Salvatore Sanfilippo. All Rights Reserved.
*/
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <math.h>
#include <string.h>
#include "cJSON.h"
#ifdef TEST_MAIN
#define RedisModule_Alloc malloc
#define RedisModule_Realloc realloc
#define RedisModule_Free free
#define RedisModule_Strdup strdup
#endif
#define EXPR_TOKEN_EOF 0
#define EXPR_TOKEN_NUM 1
#define EXPR_TOKEN_STR 2
#define EXPR_TOKEN_TUPLE 3
#define EXPR_TOKEN_SELECTOR 4
#define EXPR_TOKEN_OP 5
#define EXPR_OP_OPAREN 0 /* ( */
#define EXPR_OP_CPAREN 1 /* ) */
#define EXPR_OP_NOT 2 /* ! */
#define EXPR_OP_POW 3 /* ** */
#define EXPR_OP_MULT 4 /* * */
#define EXPR_OP_DIV 5 /* / */
#define EXPR_OP_MOD 6 /* % */
#define EXPR_OP_SUM 7 /* + */
#define EXPR_OP_DIFF 8 /* - */
#define EXPR_OP_GT 9 /* > */
#define EXPR_OP_GTE 10 /* >= */
#define EXPR_OP_LT 11 /* < */
#define EXPR_OP_LTE 12 /* <= */
#define EXPR_OP_EQ 13 /* == */
#define EXPR_OP_NEQ 14 /* != */
#define EXPR_OP_IN 15 /* in */
#define EXPR_OP_AND 16 /* and */
#define EXPR_OP_OR 17 /* or */
/* This structure represents a token in our expression. It's either
* literals like 4, "foo", or operators like "+", "-", "and", or
* json selectors, that start with a dot: ".age", ".properties.somearray[1]" */
typedef struct exprtoken {
int refcount; // Reference counting for memory reclaiming.
int token_type; // Token type of the just parsed token.
int offset; // Chars offset in expression.
union {
double num; // Value for EXPR_TOKEN_NUM.
struct {
char *start; // String pointer for EXPR_TOKEN_STR / SELECTOR.
size_t len; // String len for EXPR_TOKEN_STR / SELECTOR.
char *heapstr; // True if we have a private allocation for this
// string. When possible, it just references to the
// string expression we compiled, exprstate->expr.
} str;
int opcode; // Opcode ID for EXPR_TOKEN_OP.
struct {
struct exprtoken **ele;
size_t len;
} tuple; // Tuples are like [1, 2, 3] for "in" operator.
};
} exprtoken;
/* Simple stack of expr tokens. This is used both to represent the stack
* of values and the stack of operands during VM execution. */
typedef struct exprstack {
exprtoken **items;
int numitems;
int allocsize;
} exprstack;
typedef struct exprstate {
char *expr; /* Expression string to compile. Note that
* expression token strings point directly to this
* string. */
char *p; // Currnet position inside 'expr', while parsing.
// Virtual machine state.
exprstack values_stack;
exprstack ops_stack; // Operator stack used during compilation.
exprstack tokens; // Expression processed into a sequence of tokens.
exprstack program; // Expression compiled into opcodes and values.
} exprstate;
/* Valid operators. */
struct {
char *opname;
int oplen;
int opcode;
int precedence;
int arity;
} ExprOptable[] = {
{"(", 1, EXPR_OP_OPAREN, 7, 0},
{")", 1, EXPR_OP_CPAREN, 7, 0},
{"!", 1, EXPR_OP_NOT, 6, 1},
{"not", 3, EXPR_OP_NOT, 6, 1},
{"**", 2, EXPR_OP_POW, 5, 2},
{"*", 1, EXPR_OP_MULT, 4, 2},
{"/", 1, EXPR_OP_DIV, 4, 2},
{"%", 1, EXPR_OP_MOD, 4, 2},
{"+", 1, EXPR_OP_SUM, 3, 2},
{"-", 1, EXPR_OP_DIFF, 3, 2},
{">", 1, EXPR_OP_GT, 2, 2},
{">=", 2, EXPR_OP_GTE, 2, 2},
{"<", 1, EXPR_OP_LT, 2, 2},
{"<=", 2, EXPR_OP_LTE, 2, 2},
{"==", 2, EXPR_OP_EQ, 2, 2},
{"!=", 2, EXPR_OP_NEQ, 2, 2},
{"in", 2, EXPR_OP_IN, 2, 2},
{"and", 3, EXPR_OP_AND, 1, 2},
{"&&", 2, EXPR_OP_AND, 1, 2},
{"or", 2, EXPR_OP_OR, 0, 2},
{"||", 2, EXPR_OP_OR, 0, 2},
{NULL, 0, 0, 0, 0} // Terminator.
};
#define EXPR_OP_SPECIALCHARS "+-*%/!()<>=|&"
#define EXPR_SELECTOR_SPECIALCHARS "_-"
/* ================================ Expr token ============================== */
/* Return an heap allocated token of the specified type, setting the
* reference count to 1. */
exprtoken *exprNewToken(int type) {
exprtoken *t = RedisModule_Alloc(sizeof(exprtoken));
memset(t,0,sizeof(*t));
t->token_type = type;
t->refcount = 1;
return t;
}
/* Generic free token function, can be used to free stack allocated
* objects (in this case the pointer itself will not be freed) or
* heap allocated objects. See the wrappers below. */
void exprTokenRelease(exprtoken *t) {
if (t == NULL) return;
if (t->refcount <= 0) {
printf("exprTokenRelease() against a token with refcount %d!\n"
"Aborting program execution\n",
t->refcount);
exit(1);
}
t->refcount--;
if (t->refcount > 0) return;
// We reached refcount 0: free the object.
if (t->token_type == EXPR_TOKEN_STR) {
if (t->str.heapstr != NULL) RedisModule_Free(t->str.heapstr);
} else if (t->token_type == EXPR_TOKEN_TUPLE) {
for (size_t j = 0; j < t->tuple.len; j++)
exprTokenRelease(t->tuple.ele[j]);
if (t->tuple.ele) RedisModule_Free(t->tuple.ele);
}
RedisModule_Free(t);
}
void exprTokenRetain(exprtoken *t) {
t->refcount++;
}
/* ============================== Stack handling ============================ */
#include <stdlib.h>
#include <string.h>
#define EXPR_STACK_INITIAL_SIZE 16
/* Initialize a new expression stack. */
void exprStackInit(exprstack *stack) {
stack->items = RedisModule_Alloc(sizeof(exprtoken*) * EXPR_STACK_INITIAL_SIZE);
stack->numitems = 0;
stack->allocsize = EXPR_STACK_INITIAL_SIZE;
}
/* Push a token pointer onto the stack. Does not increment the refcount
* of the token: it is up to the caller doing this. */
void exprStackPush(exprstack *stack, exprtoken *token) {
/* Check if we need to grow the stack. */
if (stack->numitems == stack->allocsize) {
size_t newsize = stack->allocsize * 2;
exprtoken **newitems =
RedisModule_Realloc(stack->items, sizeof(exprtoken*) * newsize);
stack->items = newitems;
stack->allocsize = newsize;
}
stack->items[stack->numitems] = token;
stack->numitems++;
}
/* Pop a token pointer from the stack. Return NULL if the stack is
* empty. Does NOT recrement the refcount of the token, it's up to the
* caller to do so, as the new owner of the reference. */
exprtoken *exprStackPop(exprstack *stack) {
if (stack->numitems == 0) return NULL;
stack->numitems--;
return stack->items[stack->numitems];
}
/* Just return the last element pushed, without consuming it nor altering
* the reference count. */
exprtoken *exprStackPeek(exprstack *stack) {
if (stack->numitems == 0) return NULL;
return stack->items[stack->numitems-1];
}
/* Free the stack structure state, including the items it contains, that are
* assumed to be heap allocated. The passed pointer itself is not freed. */
void exprStackFree(exprstack *stack) {
for (int j = 0; j < stack->numitems; j++)
exprTokenRelease(stack->items[j]);
RedisModule_Free(stack->items);
}
/* Just reset the stack removing all the items, but leaving it in a state
* that makes it still usable for new elements. */
void exprStackReset(exprstack *stack) {
for (int j = 0; j < stack->numitems; j++)
exprTokenRelease(stack->items[j]);
stack->numitems = 0;
}
/* =========================== Expression compilation ======================= */
void exprConsumeSpaces(exprstate *es) {
while(es->p[0] && isspace(es->p[0])) es->p++;
}
/* Parse an operator, trying to match the longer match in the
* operators table. */
exprtoken *exprParseOperator(exprstate *es) {
exprtoken *t = exprNewToken(EXPR_TOKEN_OP);
char *start = es->p;
while(es->p[0] &&
(isalpha(es->p[0]) ||
strchr(EXPR_OP_SPECIALCHARS,es->p[0]) != NULL))
{
es->p++;
}
int matchlen = es->p - start;
int bestlen = 0;
int j;
// Find the longest matching operator.
for (j = 0; ExprOptable[j].opname != NULL; j++) {
if (ExprOptable[j].oplen > matchlen) continue;
if (memcmp(ExprOptable[j].opname, start, ExprOptable[j].oplen) != 0)
{
continue;
}
if (ExprOptable[j].oplen > bestlen) {
t->opcode = ExprOptable[j].opcode;
bestlen = ExprOptable[j].oplen;
}
}
if (bestlen == 0) {
exprTokenRelease(t);
return NULL;
} else {
es->p = start + bestlen;
}
return t;
}
// Valid selector charset.
static int is_selector_char(int c) {
return (isalpha(c) ||
isdigit(c) ||
strchr(EXPR_SELECTOR_SPECIALCHARS,c) != NULL);
}
/* Parse selectors, they start with a dot and can have alphanumerical
* or few special chars. */
exprtoken *exprParseSelector(exprstate *es) {
exprtoken *t = exprNewToken(EXPR_TOKEN_SELECTOR);
es->p++; // Skip dot.
char *start = es->p;
while(es->p[0] && is_selector_char(es->p[0])) es->p++;
int matchlen = es->p - start;
t->str.start = start;
t->str.len = matchlen;
return t;
}
exprtoken *exprParseNumber(exprstate *es) {
exprtoken *t = exprNewToken(EXPR_TOKEN_NUM);
char num[64];
int idx = 0;
while(isdigit(es->p[0]) || es->p[0] == '.' || es->p[0] == 'e' ||
es->p[0] == 'E' || (idx == 0 && es->p[0] == '-'))
{
if (idx >= (int)sizeof(num)-1) {
exprTokenRelease(t);
return NULL;
}
num[idx++] = es->p[0];
es->p++;
}
num[idx] = 0;
char *endptr;
t->num = strtod(num, &endptr);
if (*endptr != '\0') {
exprTokenRelease(t);
return NULL;
}
return t;
}
exprtoken *exprParseString(exprstate *es) {
char quote = es->p[0]; /* Store the quote type (' or "). */
es->p++; /* Skip opening quote. */
exprtoken *t = exprNewToken(EXPR_TOKEN_STR);
t->str.start = es->p;
while(es->p[0] != '\0') {
if (es->p[0] == '\\' && es->p[1] != '\0') {
es->p += 2; // Skip escaped char.
continue;
}
if (es->p[0] == quote) {
t->str.len = es->p - t->str.start;
es->p++; // Skip closing quote.
return t;
}
es->p++;
}
/* If we reach here, string was not terminated. */
exprTokenRelease(t);
return NULL;
}
/* Parse a tuple of the form [1, "foo", 42]. No nested tuples are
* supported. This type is useful mostly to be used with the "IN"
* operator. */
exprtoken *exprParseTuple(exprstate *es) {
exprtoken *t = exprNewToken(EXPR_TOKEN_TUPLE);
t->tuple.ele = NULL;
t->tuple.len = 0;
es->p++; /* Skip opening '['. */
size_t allocated = 0;
while(1) {
exprConsumeSpaces(es);
/* Check for empty tuple or end. */
if (es->p[0] == ']') {
es->p++;
break;
}
/* Grow tuple array if needed. */
if (t->tuple.len == allocated) {
size_t newsize = allocated == 0 ? 4 : allocated * 2;
exprtoken **newele = RedisModule_Realloc(t->tuple.ele,
sizeof(exprtoken*) * newsize);
t->tuple.ele = newele;
allocated = newsize;
}
/* Parse tuple element. */
exprtoken *ele = NULL;
if (isdigit(es->p[0]) || es->p[0] == '-') {
ele = exprParseNumber(es);
} else if (es->p[0] == '"' || es->p[0] == '\'') {
ele = exprParseString(es);
} else {
exprTokenRelease(t);
return NULL;
}
/* Error parsing number/string? */
if (ele == NULL) {
exprTokenRelease(t);
return NULL;
}
/* Store element if no error was detected. */
t->tuple.ele[t->tuple.len] = ele;
t->tuple.len++;
/* Check for next element. */
exprConsumeSpaces(es);
if (es->p[0] == ']') {
es->p++;
break;
}
if (es->p[0] != ',') {
exprTokenRelease(t);
return NULL;
}
es->p++; /* Skip comma. */
}
return t;
}
/* Deallocate the object returned by exprCompile(). */
void exprFree(exprstate *es) {
if (es == NULL) return;
/* Free the original expression string. */
if (es->expr) RedisModule_Free(es->expr);
/* Free all stacks. */
exprStackFree(&es->values_stack);
exprStackFree(&es->ops_stack);
exprStackFree(&es->tokens);
exprStackFree(&es->program);
/* Free the state object itself. */
RedisModule_Free(es);
}
/* Split the provided expression into a stack of tokens. Returns
* 0 on success, 1 on error. */
int exprTokenize(exprstate *es, int *errpos) {
/* Main parsing loop. */
while(1) {
exprConsumeSpaces(es);
/* Set a flag to see if we can consider the - part of the
* number, or an operator. */
int minus_is_number = 0; // By default is an operator.
exprtoken *last = exprStackPeek(&es->tokens);
if (last == NULL) {
/* If we are at the start of an expression, the minus is
* considered a number. */
minus_is_number = 1;
} else if (last->token_type == EXPR_TOKEN_OP &&
last->opcode != EXPR_OP_CPAREN)
{
/* Also, if the previous token was an operator, the minus
* is considered a number, unless the previous operator is
* a closing parens. In such case it's like (...) -5, or alike
* and we want to emit an operator. */
minus_is_number = 1;
}
/* Parse based on the current character. */
exprtoken *current = NULL;
if (*es->p == '\0') {
current = exprNewToken(EXPR_TOKEN_EOF);
} else if (isdigit(*es->p) ||
(minus_is_number && *es->p == '-' && isdigit(es->p[1])))
{
current = exprParseNumber(es);
} else if (*es->p == '"' || *es->p == '\'') {
current = exprParseString(es);
} else if (*es->p == '.' && is_selector_char(es->p[1])) {
current = exprParseSelector(es);
} else if (isalpha(*es->p) || strchr(EXPR_OP_SPECIALCHARS, *es->p)) {
current = exprParseOperator(es);
} else if (*es->p == '[') {
current = exprParseTuple(es);
}
if (current == NULL) {
if (errpos) *errpos = es->p - es->expr;
return 1; // Syntax Error.
}
/* Push the current token to tokens stack. */
exprStackPush(&es->tokens, current);
if (current->token_type == EXPR_TOKEN_EOF) break;
}
return 0;
}
/* Helper function to get operator precedence from the operator table. */
int exprGetOpPrecedence(int opcode) {
for (int i = 0; ExprOptable[i].opname != NULL; i++) {
if (ExprOptable[i].opcode == opcode)
return ExprOptable[i].precedence;
}
return -1;
}
/* Helper function to get operator arity from the operator table. */
int exprGetOpArity(int opcode) {
for (int i = 0; ExprOptable[i].opname != NULL; i++) {
if (ExprOptable[i].opcode == opcode)
return ExprOptable[i].arity;
}
return -1;
}
/* Process an operator during compilation. Returns 0 on success, 1 on error.
* This function will retain a reference of the operator 'op' in case it
* is pushed on the operators stack. */
int exprProcessOperator(exprstate *es, exprtoken *op, int *stack_items, int *errpos) {
if (op->opcode == EXPR_OP_OPAREN) {
// This is just a marker for us. Do nothing.
exprStackPush(&es->ops_stack, op);
exprTokenRetain(op);
return 0;
}
if (op->opcode == EXPR_OP_CPAREN) {
/* Process operators until we find the matching opening parenthesis. */
while (1) {
exprtoken *top_op = exprStackPop(&es->ops_stack);
if (top_op == NULL) {
if (errpos) *errpos = op->offset;
return 1;
}
if (top_op->opcode == EXPR_OP_OPAREN) {
/* Open parethesis found. Our work finished. */
exprTokenRelease(top_op);
return 0;
}
int arity = exprGetOpArity(top_op->opcode);
if (*stack_items < arity) {
exprTokenRelease(top_op);
if (errpos) *errpos = top_op->offset;
return 1;
}
/* Move the operator on the program stack. */
exprStackPush(&es->program, top_op);
*stack_items = *stack_items - arity + 1;
}
}
int curr_prec = exprGetOpPrecedence(op->opcode);
/* Process operators with higher or equal precedence. */
while (1) {
exprtoken *top_op = exprStackPeek(&es->ops_stack);
if (top_op == NULL || top_op->opcode == EXPR_OP_OPAREN) break;
int top_prec = exprGetOpPrecedence(top_op->opcode);
if (top_prec < curr_prec) break;
/* Special case for **: only pop if precedence is strictly higher
* so that the operator is right associative, that is:
* 2 ** 3 ** 2 is evaluated as 2 ** (3 ** 2) == 512 instead
* of (2 ** 3) ** 2 == 64. */
if (op->opcode == EXPR_OP_POW && top_prec <= curr_prec) break;
/* Pop and add to program. */
top_op = exprStackPop(&es->ops_stack);
int arity = exprGetOpArity(top_op->opcode);
if (*stack_items < arity) {
exprTokenRelease(top_op);
if (errpos) *errpos = top_op->offset;
return 1;
}
/* Move to the program stack. */
exprStackPush(&es->program, top_op);
*stack_items = *stack_items - arity + 1;
}
/* Push current operator. */
exprStackPush(&es->ops_stack, op);
exprTokenRetain(op);
return 0;
}
/* Compile the expression into a set of push-value and exec-operator
* that exprRun() can execute. The function returns an expstate object
* that can be used for execution of the program. On error, NULL
* is returned, and optionally the position of the error into the
* expression is returned by reference. */
exprstate *exprCompile(char *expr, int *errpos) {
/* Initialize expression state. */
exprstate *es = RedisModule_Alloc(sizeof(exprstate));
es->expr = RedisModule_Strdup(expr);
es->p = es->expr;
/* Initialize all stacks. */
exprStackInit(&es->values_stack);
exprStackInit(&es->ops_stack);
exprStackInit(&es->tokens);
exprStackInit(&es->program);
/* Tokenization. */
if (exprTokenize(es, errpos)) {
exprFree(es);
return NULL;
}
/* Compile the expression into a sequence of operations. */
int stack_items = 0; // Track # of items that would be on the stack
// during execution. This way we can detect arity
// issues at compile time.
/* Process each token. */
for (int i = 0; i < es->tokens.numitems; i++) {
exprtoken *token = es->tokens.items[i];
if (token->token_type == EXPR_TOKEN_EOF) break;
/* Handle values (numbers, strings, selectors). */
if (token->token_type == EXPR_TOKEN_NUM ||
token->token_type == EXPR_TOKEN_STR ||
token->token_type == EXPR_TOKEN_TUPLE ||
token->token_type == EXPR_TOKEN_SELECTOR)
{
exprStackPush(&es->program, token);
exprTokenRetain(token);
stack_items++;
continue;
}
/* Handle operators. */
if (token->token_type == EXPR_TOKEN_OP) {
if (exprProcessOperator(es, token, &stack_items, errpos)) {
exprFree(es);
return NULL;
}
continue;
}
}
/* Process remaining operators on the stack. */
while (es->ops_stack.numitems > 0) {
exprtoken *op = exprStackPop(&es->ops_stack);
if (op->opcode == EXPR_OP_OPAREN) {
if (errpos) *errpos = op->offset;
exprTokenRelease(op);
exprFree(es);
return NULL;
}
int arity = exprGetOpArity(op->opcode);
if (stack_items < arity) {
if (errpos) *errpos = op->offset;
exprTokenRelease(op);
exprFree(es);
return NULL;
}
exprStackPush(&es->program, op);
stack_items = stack_items - arity + 1;
}
/* Verify that exactly one value would remain on the stack after
* execution. We could also check that such value is a number, but this
* would make the code more complex without much gains. */
if (stack_items != 1) {
if (errpos) {
/* Point to the last token's offset for error reporting. */
exprtoken *last = es->tokens.items[es->tokens.numitems - 1];
*errpos = last->offset;
}
exprFree(es);
return NULL;
}
return es;
}
/* ============================ Expression execution ======================== */
/* Convert a token to its numeric value. For strings we attempt to parse them
* as numbers, returning 0 if conversion fails. */
double exprTokenToNum(exprtoken *t) {
char buf[128];
if (t->token_type == EXPR_TOKEN_NUM) {
return t->num;
} else if (t->token_type == EXPR_TOKEN_STR && t->str.len < sizeof(buf)) {
memcpy(buf, t->str.start, t->str.len);
buf[t->str.len] = '\0';
char *endptr;
double val = strtod(buf, &endptr);
return *endptr == '\0' ? val : 0;
} else {
return 0;
}
}
/* Conver obejct to true/false (0 or 1) */
double exprTokenToBool(exprtoken *t) {
if (t->token_type == EXPR_TOKEN_NUM) {
return t->num != 0;
} else if (t->token_type == EXPR_TOKEN_STR && t->str.len == 0) {
return 0; // Empty string are false, like in Javascript.
} else {
return 1; // Every non numerical type is true.
}
}
/* Compare two tokens. Returns true if they are equal. */
int exprTokensEqual(exprtoken *a, exprtoken *b) {
// If both are strings, do string comparison.
if (a->token_type == EXPR_TOKEN_STR && b->token_type == EXPR_TOKEN_STR) {
return a->str.len == b->str.len &&
memcmp(a->str.start, b->str.start, a->str.len) == 0;
}
// If both are numbers, do numeric comparison.
if (a->token_type == EXPR_TOKEN_NUM && b->token_type == EXPR_TOKEN_NUM) {
return a->num == b->num;
}
// Mixed types - convert to numbers and compare.
return exprTokenToNum(a) == exprTokenToNum(b);
}
/* Convert a json object to an expression token. There is only
* limited support for JSON arrays: they must be composed of
* just numbers and strings. Returns NULL if the JSON object
* cannot be converted. */
exprtoken *exprJsonToToken(cJSON *js) {
if (cJSON_IsNumber(js)) {
exprtoken *obj = exprNewToken(EXPR_TOKEN_NUM);
obj->num = cJSON_GetNumberValue(js);
return obj;
} else if (cJSON_IsString(js)) {
exprtoken *obj = exprNewToken(EXPR_TOKEN_STR);
char *strval = cJSON_GetStringValue(js);
obj->str.heapstr = RedisModule_Strdup(strval);
obj->str.start = obj->str.heapstr;
obj->str.len = strlen(obj->str.heapstr);
return obj;
} else if (cJSON_IsBool(js)) {
exprtoken *obj = exprNewToken(EXPR_TOKEN_NUM);
obj->num = cJSON_IsTrue(js);
return obj;
} else if (cJSON_IsArray(js)) {
// First, scan the array to ensure it only
// contains strings and numbers. Otherwise the
// expression will evaluate to false.
int array_size = cJSON_GetArraySize(js);
for (int j = 0; j < array_size; j++) {
cJSON *item = cJSON_GetArrayItem(js, j);
if (!cJSON_IsNumber(item) && !cJSON_IsString(item)) return NULL;
}
// Create a tuple token for the array.
exprtoken *obj = exprNewToken(EXPR_TOKEN_TUPLE);
obj->tuple.len = array_size;
obj->tuple.ele = NULL;
if (obj->tuple.len == 0) return obj; // No elements, already ok.
obj->tuple.ele =
RedisModule_Alloc(sizeof(exprtoken*) * obj->tuple.len);
// Convert each array element to a token.
for (size_t j = 0; j < obj->tuple.len; j++) {
cJSON *item = cJSON_GetArrayItem(js, j);
if (cJSON_IsNumber(item)) {
exprtoken *eleToken = exprNewToken(EXPR_TOKEN_NUM);
eleToken->num = cJSON_GetNumberValue(item);
obj->tuple.ele[j] = eleToken;
} else if (cJSON_IsString(item)) {
exprtoken *eleToken = exprNewToken(EXPR_TOKEN_STR);
char *strval = cJSON_GetStringValue(item);
eleToken->str.heapstr = RedisModule_Strdup(strval);
eleToken->str.start = eleToken->str.heapstr;
eleToken->str.len = strlen(eleToken->str.heapstr);
obj->tuple.ele[j] = eleToken;
}
}
return obj;
}
return NULL; // No conversion possible for this type.
}
/* Execute the compiled expression program. Returns 1 if the final stack value
* evaluates to true, 0 otherwise. Also returns 0 if any selector callback
* fails. */
int exprRun(exprstate *es, char *json, size_t json_len) {
exprStackReset(&es->values_stack);
cJSON *parsed_json = NULL;
// Execute each instruction in the program.
for (int i = 0; i < es->program.numitems; i++) {
exprtoken *t = es->program.items[i];
// Handle selectors by calling the callback.
if (t->token_type == EXPR_TOKEN_SELECTOR) {
if (json != NULL) {
cJSON *attrib = NULL;
if (parsed_json == NULL) {
parsed_json = cJSON_ParseWithLength(json,json_len);
// Will be left to NULL if the above fails.
}
if (parsed_json) {
char item_name[128];
if (t->str.len > 0 && t->str.len < sizeof(item_name)) {
memcpy(item_name,t->str.start,t->str.len);
item_name[t->str.len] = 0;
attrib = cJSON_GetObjectItem(parsed_json,item_name);
}
/* Fill the token according to the JSON type stored
* at the attribute. */
if (attrib) {
exprtoken *obj = exprJsonToToken(attrib);
if (obj) {
exprStackPush(&es->values_stack, obj);
continue;
}
}
}
}
// Selector not found or JSON object not convertible to
// expression tokens. Evaluate the expression to false.
if (parsed_json) cJSON_Delete(parsed_json);
return 0;
}
// Push non-operator values directly onto the stack.
if (t->token_type != EXPR_TOKEN_OP) {
exprStackPush(&es->values_stack, t);
exprTokenRetain(t);
continue;
}
// Handle operators.
exprtoken *result = exprNewToken(EXPR_TOKEN_NUM);
// Pop operands - we know we have enough from compile-time checks.
exprtoken *b = exprStackPop(&es->values_stack);
exprtoken *a = NULL;
if (exprGetOpArity(t->opcode) == 2) {
a = exprStackPop(&es->values_stack);
}
switch(t->opcode) {
case EXPR_OP_NOT:
result->num = exprTokenToBool(b) == 0 ? 1 : 0;
break;
case EXPR_OP_POW: {
double base = exprTokenToNum(a);
double exp = exprTokenToNum(b);
result->num = pow(base, exp);
break;
}
case EXPR_OP_MULT:
result->num = exprTokenToNum(a) * exprTokenToNum(b);
break;
case EXPR_OP_DIV:
result->num = exprTokenToNum(a) / exprTokenToNum(b);
break;
case EXPR_OP_MOD: {
double va = exprTokenToNum(a);
double vb = exprTokenToNum(b);
result->num = fmod(va, vb);
break;
}
case EXPR_OP_SUM:
result->num = exprTokenToNum(a) + exprTokenToNum(b);
break;
case EXPR_OP_DIFF:
result->num = exprTokenToNum(a) - exprTokenToNum(b);
break;
case EXPR_OP_GT:
result->num = exprTokenToNum(a) > exprTokenToNum(b) ? 1 : 0;
break;
case EXPR_OP_GTE:
result->num = exprTokenToNum(a) >= exprTokenToNum(b) ? 1 : 0;
break;
case EXPR_OP_LT:
result->num = exprTokenToNum(a) < exprTokenToNum(b) ? 1 : 0;
break;
case EXPR_OP_LTE:
result->num = exprTokenToNum(a) <= exprTokenToNum(b) ? 1 : 0;
break;
case EXPR_OP_EQ:
result->num = exprTokensEqual(a, b) ? 1 : 0;
break;
case EXPR_OP_NEQ:
result->num = !exprTokensEqual(a, b) ? 1 : 0;
break;
case EXPR_OP_IN: {
// For 'in' operator, b must be a tuple.
result->num = 0; // Default to false.
if (b->token_type == EXPR_TOKEN_TUPLE) {
for (size_t j = 0; j < b->tuple.len; j++) {
if (exprTokensEqual(a, b->tuple.ele[j])) {
result->num = 1; // Found a match.
break;
}
}
}
break;
}
case EXPR_OP_AND:
result->num =
exprTokenToBool(a) != 0 && exprTokenToBool(b) != 0 ? 1 : 0;
break;
case EXPR_OP_OR:
result->num =
exprTokenToBool(a) != 0 || exprTokenToBool(b) != 0 ? 1 : 0;
break;
default:
// Do nothing: we don't want runtime errors.
break;
}
// Free operands and push result.
if (a) exprTokenRelease(a);
exprTokenRelease(b);
exprStackPush(&es->values_stack, result);
}
if (parsed_json) cJSON_Delete(parsed_json);
// Get final result from stack.
exprtoken *final = exprStackPop(&es->values_stack);
if (final == NULL) return 0;
// Convert result to boolean.
int retval = exprTokenToBool(final);
exprTokenRelease(final);
return retval;
}
/* ============================ Simple test main ============================ */
#ifdef TEST_MAIN
void exprPrintToken(exprtoken *t) {
switch(t->token_type) {
case EXPR_TOKEN_EOF:
printf("EOF");
break;
case EXPR_TOKEN_NUM:
printf("NUM:%g", t->num);
break;
case EXPR_TOKEN_STR:
printf("STR:\"%.*s\"", (int)t->str.len, t->str.start);
break;
case EXPR_TOKEN_SELECTOR:
printf("SEL:%.*s", (int)t->str.len, t->str.start);
break;
case EXPR_TOKEN_OP:
printf("OP:");
for (int i = 0; ExprOptable[i].opname != NULL; i++) {
if (ExprOptable[i].opcode == t->opcode) {
printf("%s", ExprOptable[i].opname);
break;
}
}
break;
default:
printf("UNKNOWN");
break;
}
}
void exprPrintStack(exprstack *stack, const char *name) {
printf("%s (%d items):", name, stack->numitems);
for (int j = 0; j < stack->numitems; j++) {
printf(" ");
exprPrintToken(stack->items[j]);
}
printf("\n");
}
int main(int argc, char **argv) {
char *testexpr = "(5+2)*3 and .year > 1980 and 'foo' == 'foo'";
char *testjson = "{\"year\": 1984, \"name\": \"The Matrix\"}";
if (argc >= 2) testexpr = argv[1];
if (argc >= 3) testjson = argv[2];
printf("Compiling expression: %s\n", testexpr);
int errpos = 0;
exprstate *es = exprCompile(testexpr,&errpos);
if (es == NULL) {
printf("Compilation failed near \"...%s\"\n", testexpr+errpos);
return 1;
}
exprPrintStack(&es->tokens, "Tokens");
exprPrintStack(&es->program, "Program");
printf("Running against object: %s\n", testjson);
int result = exprRun(es,testjson,strlen(testjson));
printf("Result1: %s\n", result ? "True" : "False");
result = exprRun(es,testjson,strlen(testjson));
printf("Result2: %s\n", result ? "True" : "False");
exprFree(es);
return 0;
}
#endif
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