1 files changed, 56 insertions, 0 deletions
diff --git a/src/libnetdata/eval/eval.h b/src/libnetdata/eval/eval.h
new file mode 100644
index 000000000..48a3b073f
--- /dev/null
+++ b/src/libnetdata/eval/eval.h
@@ -0,0 +1,56 @@
+// 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
+
+struct eval_expression;
+typedef struct eval_expression EVAL_EXPRESSION;
+typedef bool (*eval_expression_variable_lookup_t)(STRING *variable, void *data, NETDATA_DOUBLE *result);
+
+// 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
+EVAL_EXPRESSION *expression_parse(const char *string, const char **failed_at, int *error);
+
+// free all resources allocated for an expression
+void expression_free(EVAL_EXPRESSION *expression);
+
+// convert an error code to a message
+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)
+int expression_evaluate(EVAL_EXPRESSION *expression);
+
+const char *expression_source(EVAL_EXPRESSION *expression);
+const char *expression_parsed_as(EVAL_EXPRESSION *expression);
+const char *expression_error_msg(EVAL_EXPRESSION *expression);
+NETDATA_DOUBLE expression_result(EVAL_EXPRESSION *expression);
+void expression_set_variable_lookup_callback(EVAL_EXPRESSION *expression, eval_expression_variable_lookup_t cb, void *data);
+
+void expression_hardcode_variable(EVAL_EXPRESSION *expression, STRING *variable, NETDATA_DOUBLE value);
+
+#endif //NETDATA_EVAL_H