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-rw-r--r--libnetdata/eval/eval.h88
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diff --git a/libnetdata/eval/eval.h b/libnetdata/eval/eval.h
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+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef NETDATA_EVAL_H
+#define NETDATA_EVAL_H 1
+
+#include "../libnetdata.h"
+
+#define EVAL_MAX_VARIABLE_NAME_LENGTH 300
+
+typedef enum rrdcalc_status {
+ RRDCALC_STATUS_REMOVED = -2,
+ RRDCALC_STATUS_UNDEFINED = -1,
+ RRDCALC_STATUS_UNINITIALIZED = 0,
+ RRDCALC_STATUS_CLEAR = 1,
+ RRDCALC_STATUS_RAISED = 2,
+ RRDCALC_STATUS_WARNING = 3,
+ RRDCALC_STATUS_CRITICAL = 4
+} RRDCALC_STATUS;
+
+typedef struct eval_variable {
+ char *name;
+ uint32_t hash;
+ struct eval_variable *next;
+} EVAL_VARIABLE;
+
+typedef struct eval_expression {
+ const char *source;
+ const char *parsed_as;
+
+ RRDCALC_STATUS *status;
+ calculated_number *this;
+ time_t *after;
+ time_t *before;
+
+ calculated_number result;
+
+ int error;
+ BUFFER *error_msg;
+
+ // hidden EVAL_NODE *
+ void *nodes;
+
+ // custom data to be used for looking up variables
+ struct rrdcalc *rrdcalc;
+} EVAL_EXPRESSION;
+
+#define EVAL_VALUE_INVALID 0
+#define EVAL_VALUE_NUMBER 1
+#define EVAL_VALUE_VARIABLE 2
+#define EVAL_VALUE_EXPRESSION 3
+
+// parsing and evaluation
+#define EVAL_ERROR_OK 0
+
+// parsing errors
+#define EVAL_ERROR_MISSING_CLOSE_SUBEXPRESSION 1
+#define EVAL_ERROR_UNKNOWN_OPERAND 2
+#define EVAL_ERROR_MISSING_OPERAND 3
+#define EVAL_ERROR_MISSING_OPERATOR 4
+#define EVAL_ERROR_REMAINING_GARBAGE 5
+#define EVAL_ERROR_IF_THEN_ELSE_MISSING_ELSE 6
+
+// evaluation errors
+#define EVAL_ERROR_INVALID_VALUE 101
+#define EVAL_ERROR_INVALID_NUMBER_OF_OPERANDS 102
+#define EVAL_ERROR_VALUE_IS_NAN 103
+#define EVAL_ERROR_VALUE_IS_INFINITE 104
+#define EVAL_ERROR_UNKNOWN_VARIABLE 105
+
+// parse the given string as an expression and return:
+// a pointer to an expression if it parsed OK
+// NULL in which case the pointer to error has the error code
+extern EVAL_EXPRESSION *expression_parse(const char *string, const char **failed_at, int *error);
+
+// free all resources allocated for an expression
+extern void expression_free(EVAL_EXPRESSION *expression);
+
+// convert an error code to a message
+extern const char *expression_strerror(int error);
+
+// evaluate an expression and return
+// 1 = OK, the result is in: expression->result
+// 2 = FAILED, the error message is in: buffer_tostring(expression->error_msg)
+extern int expression_evaluate(EVAL_EXPRESSION *expression);
+
+extern int health_variable_lookup(const char *variable, uint32_t hash, struct rrdcalc *rc, calculated_number *result);
+
+#endif //NETDATA_EVAL_H