various renames to make the code more readable

2 files changed, 118 insertions, 116 deletions

diff --git a/src/eval.c b/src/eval.c
index ff121b5ceb..93d768cf78 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -1,11 +1,10 @@
 #include "common.h"
 
 // forward definitions
-static inline void operand_free(EVAL_OPERAND *op);
-static inline EVAL_OPERAND *parse_operand(const char **string, int *error);
-static inline EVAL_OPERAND *parse_operand1(const char **string, int *error);
-static inline calculated_number eval_operand(EVAL_OPERAND *op, int *error);
-
+static inline void eval_node_free(EVAL_NODE *op);
+static inline EVAL_NODE *parse_full_expression(const char **string, int *error);
+static inline EVAL_NODE *parse_one_full_operand(const char **string, int *error);
+static inline calculated_number eval_node(EVAL_NODE *op, int *error);
 
 static inline void skip_spaces(const char **string) {
     const char *s = *string;
@@ -217,7 +216,7 @@ static inline int parse_close_subexpression(const char **string) {
     return 0;
 }
 
-static inline int parse_literal(const char **string, calculated_number *number) {
+static inline int parse_constant(const char **string, calculated_number *number) {
     char *end = NULL;
     calculated_number n = strtold(*string, &end);
     if(unlikely(!end || *string == end || isnan(n) || isinf(n))) {
@@ -225,7 +224,6 @@ static inline int parse_literal(const char **string, calculated_number *number)
         return 0;
     }
     *number = n;
-
     *string = end;
     return 1;
 }
@@ -251,7 +249,7 @@ static inline int parse_not(const char **string) {
 }
 
 static struct operator_parser {
-    char id;
+    unsigned char id;
     int (*parse)(const char **);
 } operator_parsers[] = {
         // the order in this list is important!
@@ -272,13 +270,13 @@ static struct operator_parser {
         { EVAL_OPERATOR_MULTIPLY,              parse_multiply },
         { EVAL_OPERATOR_DIVIDE,                parse_divide },
 
-        /* we should not put
+        /* we should not put in this list the following:
          *
          *  - NOT
          *  - (
          *  - )
          *
-         * in this list
+         * these are handled in code
          */
 
         { EVAL_OPERATOR_NOP, NULL }
@@ -306,7 +304,7 @@ static inline calculated_number eval_value(EVAL_VALUE *v, int *error) {
 
     switch(v->type) {
         case EVAL_VALUE_EXPRESSION:
-            n = eval_operand(v->expression, error);
+            n = eval_node(v->expression, error);
             break;
 
         case EVAL_VALUE_NUMBER:
@@ -325,52 +323,52 @@ static inline calculated_number eval_value(EVAL_VALUE *v, int *error) {
     return eval_check_number(n, error);
 }
 
-calculated_number eval_and(EVAL_OPERAND *op, int *error) {
+calculated_number eval_and(EVAL_NODE *op, int *error) {
     return eval_value(&op->ops[0], error) && eval_value(&op->ops[1], error);
 }
-calculated_number eval_or(EVAL_OPERAND *op, int *error) {
+calculated_number eval_or(EVAL_NODE *op, int *error) {
     return eval_value(&op->ops[0], error) || eval_value(&op->ops[1], error);
 }
-calculated_number eval_greater_than_or_equal(EVAL_OPERAND *op, int *error) {
+calculated_number eval_greater_than_or_equal(EVAL_NODE *op, int *error) {
     return eval_value(&op->ops[0], error) >= eval_value(&op->ops[1], error);
 }
-calculated_number eval_less_than_or_equal(EVAL_OPERAND *op, int *error) {
+calculated_number eval_less_than_or_equal(EVAL_NODE *op, int *error) {
     return eval_value(&op->ops[0], error) <= eval_value(&op->ops[1], error);
 }
-calculated_number eval_not_equal(EVAL_OPERAND *op, int *error) {
+calculated_number eval_not_equal(EVAL_NODE *op, int *error) {
     return eval_value(&op->ops[0], error) != eval_value(&op->ops[1], error);
 }
-calculated_number eval_equal(EVAL_OPERAND *op, int *error) {
+calculated_number eval_equal(EVAL_NODE *op, int *error) {
     return eval_value(&op->ops[0], error) == eval_value(&op->ops[1], error);
 }
-calculated_number eval_less(EVAL_OPERAND *op, int *error) {
+calculated_number eval_less(EVAL_NODE *op, int *error) {
     return eval_value(&op->ops[0], error) < eval_value(&op->ops[1], error);
 }
-calculated_number eval_greater(EVAL_OPERAND *op, int *error) {
+calculated_number eval_greater(EVAL_NODE *op, int *error) {
     return eval_value(&op->ops[0], error) > eval_value(&op->ops[1], error);
 }
-calculated_number eval_plus(EVAL_OPERAND *op, int *error) {
+calculated_number eval_plus(EVAL_NODE *op, int *error) {
     return eval_value(&op->ops[0], error) + eval_value(&op->ops[1], error);
 }
-calculated_number eval_minus(EVAL_OPERAND *op, int *error) {
+calculated_number eval_minus(EVAL_NODE *op, int *error) {
     return eval_value(&op->ops[0], error) - eval_value(&op->ops[1], error);
 }
-calculated_number eval_multiply(EVAL_OPERAND *op, int *error) {
+calculated_number eval_multiply(EVAL_NODE *op, int *error) {
     return eval_value(&op->ops[0], error) * eval_value(&op->ops[1], error);
 }
-calculated_number eval_divide(EVAL_OPERAND *op, int *error) {
+calculated_number eval_divide(EVAL_NODE *op, int *error) {
     return eval_value(&op->ops[0], error) / eval_value(&op->ops[1], error);
 }
-calculated_number eval_nop(EVAL_OPERAND *op, int *error) {
+calculated_number eval_nop(EVAL_NODE *op, int *error) {
     return eval_value(&op->ops[0], error);
 }
-calculated_number eval_not(EVAL_OPERAND *op, int *error) {
+calculated_number eval_not(EVAL_NODE *op, int *error) {
     return !eval_value(&op->ops[0], error);
 }
-calculated_number eval_sign_plus(EVAL_OPERAND *op, int *error) {
+calculated_number eval_sign_plus(EVAL_NODE *op, int *error) {
     return eval_value(&op->ops[0], error);
 }
-calculated_number eval_sign_minus(EVAL_OPERAND *op, int *error) {
+calculated_number eval_sign_minus(EVAL_NODE *op, int *error) {
     return -eval_value(&op->ops[0], error);
 }
 
@@ -378,7 +376,7 @@ static struct operator {
     const char *print_as;
     char precedence;
     char parameters;
-    calculated_number (*eval)(EVAL_OPERAND *op, int *error);
+    calculated_number (*eval)(EVAL_NODE *op, int *error);
 } operators[256] = {
         // this is a random access array
         // we always access it with a known EVAL_OPERATOR_X
@@ -408,7 +406,7 @@ static struct operator {
 
 #define eval_precedence(operator) (operators[(unsigned char)(operator)].precedence)
 
-static inline calculated_number eval_operand(EVAL_OPERAND *op, int *error) {
+static inline calculated_number eval_node(EVAL_NODE *op, int *error) {
     if(unlikely(op->count != operators[op->operator].parameters)) {
         *error = EVAL_ERROR_INVALID_NUMBER_OF_OPERANDS;
         return 0;
@@ -421,7 +419,7 @@ static inline calculated_number eval_operand(EVAL_OPERAND *op, int *error) {
 
 // ----------------------------------------------------------------------------
 
-static inline char parse_operator(const char **string, int *precedence) {
+static inline unsigned char parse_operator(const char **string, int *precedence) {
     skip_spaces(string);
 
     int i;
@@ -434,11 +432,10 @@ static inline char parse_operator(const char **string, int *precedence) {
     return EVAL_OPERATOR_NOP;
 }
 
-
-static inline EVAL_OPERAND *operand_alloc(int count) {
+static inline EVAL_NODE *eval_node_alloc(int count) {
     static int id = 1;
 
-    EVAL_OPERAND *op = calloc(1, sizeof(EVAL_OPERAND) + (sizeof(EVAL_VALUE) * count));
+    EVAL_NODE *op = calloc(1, sizeof(EVAL_NODE) + (sizeof(EVAL_VALUE) * count));
     if(!op) fatal("Cannot allocate memory for OPERAND with %d slots", count);
 
     op->id = id++;
@@ -448,7 +445,7 @@ static inline EVAL_OPERAND *operand_alloc(int count) {
     return op;
 }
 
-static inline void operand_set_value_operand(EVAL_OPERAND *op, int pos, EVAL_OPERAND *value) {
+static inline void eval_node_set_value_to_node(EVAL_NODE *op, int pos, EVAL_NODE *value) {
     if(pos >= op->count)
         fatal("Invalid request to set position %d of OPERAND that has only %d values", pos + 1, op->count + 1);
 
@@ -456,7 +453,7 @@ static inline void operand_set_value_operand(EVAL_OPERAND *op, int pos, EVAL_OPE
     op->ops[pos].expression = value;
 }
 
-static inline void operand_set_value_literal(EVAL_OPERAND *op, int pos, calculated_number value) {
+static inline void node_set_value_to_constant(EVAL_NODE *op, int pos, calculated_number value) {
     if(pos >= op->count)
         fatal("Invalid request to set position %d of OPERAND that has only %d values", pos + 1, op->count + 1);
 
@@ -471,19 +468,19 @@ static inline void variable_free(VARIABLE *v) {
 static inline void value_free(EVAL_VALUE *v) {
     switch(v->type) {
         case EVAL_VALUE_EXPRESSION:
-            operand_free(v->expression);
+            eval_node_free(v->expression);
             break;
 
-        case EVAL_VALUE_VARIABLE:
-            variable_free(v->variable);
-            break;
+//        case EVAL_VALUE_VARIABLE:
+//            variable_free(v->variable);
+//            break;
 
         default:
             break;
     }
 }
 
-static inline void operand_free(EVAL_OPERAND *op) {
+static inline void eval_node_free(EVAL_NODE *op) {
     if(op->count) {
         int i;
         for(i = op->count - 1; i >= 0 ;i--)
@@ -493,18 +490,18 @@ static inline void operand_free(EVAL_OPERAND *op) {
     free(op);
 }
 
-static inline EVAL_OPERAND *parse_operand_with_operator(const char **string, char type, int *error) {
-    EVAL_OPERAND *sub = parse_operand1(string, error);
+static inline EVAL_NODE *parse_next_operand_given_its_operator(const char **string, unsigned char operator_type, int *error) {
+    EVAL_NODE *sub = parse_one_full_operand(string, error);
     if(!sub) return NULL;
 
-    EVAL_OPERAND *op = operand_alloc(1);
-    op->operator = type;
-    operand_set_value_operand(op, 0, sub);
+    EVAL_NODE *op = eval_node_alloc(1);
+    op->operator = operator_type;
+    eval_node_set_value_to_node(op, 0, sub);
     return op;
 }
 
-static inline EVAL_OPERAND *parse_operand1(const char **string, int *error) {
-    EVAL_OPERAND *op1 = NULL;
+static inline EVAL_NODE *parse_one_full_operand(const char **string, int *error) {
+    EVAL_NODE *op1 = NULL;
     calculated_number number;
 
     *error = EVAL_ERROR_OK;
@@ -516,27 +513,27 @@ static inline EVAL_OPERAND *parse_operand1(const char **string, int *error) {
     }
 
     if(parse_not(string)) {
-        op1 = parse_operand_with_operator(string, EVAL_OPERATOR_NOT, error);
+        op1 = parse_next_operand_given_its_operator(string, EVAL_OPERATOR_NOT, error);
         op1->precedence = eval_precedence(EVAL_OPERATOR_NOT);
     }
     else if(parse_plus(string)) {
-        op1 = parse_operand_with_operator(string, EVAL_OPERATOR_SIGN_PLUS, error);
+        op1 = parse_next_operand_given_its_operator(string, EVAL_OPERATOR_SIGN_PLUS, error);
         op1->precedence = eval_precedence(EVAL_OPERATOR_SIGN_PLUS);
     }
     else if(parse_minus(string)) {
-        op1 = parse_operand_with_operator(string, EVAL_OPERATOR_SIGN_MINUS, error);
+        op1 = parse_next_operand_given_its_operator(string, EVAL_OPERATOR_SIGN_MINUS, error);
         op1->precedence = eval_precedence(EVAL_OPERATOR_SIGN_MINUS);
     }
     else if(parse_open_subexpression(string)) {
-        EVAL_OPERAND *sub = parse_operand(string, error);
+        EVAL_NODE *sub = parse_full_expression(string, error);
         if(sub) {
-            op1 = operand_alloc(1);
+            op1 = eval_node_alloc(1);
             op1->operator = EVAL_OPERATOR_EXPRESSION_OPEN;
             op1->precedence = eval_precedence(EVAL_OPERATOR_EXPRESSION_OPEN);
-            operand_set_value_operand(op1, 0, sub);
+            eval_node_set_value_to_node(op1, 0, sub);
             if(!parse_close_subexpression(string)) {
                 *error = EVAL_ERROR_MISSING_CLOSE_SUBEXPRESSION;
-                operand_free(op1);
+                eval_node_free(op1);
                 return NULL;
             }
         }
@@ -544,10 +541,10 @@ static inline EVAL_OPERAND *parse_operand1(const char **string, int *error) {
 //    else if(parse_variable(string)) {
 //
 //    }
-    else if(parse_literal(string, &number)) {
-        op1 = operand_alloc(1);
+    else if(parse_constant(string, &number)) {
+        op1 = eval_node_alloc(1);
         op1->operator = EVAL_OPERATOR_VALUE;
-        operand_set_value_literal(op1, 0, number);
+        node_set_value_to_constant(op1, 0, number);
     }
     else if(*string)
         *error = EVAL_ERROR_UNKNOWN_OPERAND;
@@ -557,41 +554,42 @@ static inline EVAL_OPERAND *parse_operand1(const char **string, int *error) {
     return op1;
 }
 
-static inline EVAL_OPERAND *parse_operand_rest(const char **string, int *error, EVAL_OPERAND *op1) {
-    EVAL_OPERAND *op2 = NULL;
-    char operator;
+static inline EVAL_NODE *parse_rest_of_expression(const char **string, int *error, EVAL_NODE *op1) {
+    EVAL_NODE *op2 = NULL;
+    unsigned char operator;
     int precedence;
 
     operator = parse_operator(string, &precedence);
     skip_spaces(string);
 
     if(operator != EVAL_OPERATOR_NOP) {
-        op2 = parse_operand1(string, error);
+        op2 = parse_one_full_operand(string, error);
         if(!op2) {
-            operand_free(op1);
+            // error is already reported
+            eval_node_free(op1);
             return NULL;
         }
 
-        EVAL_OPERAND *op = operand_alloc(2);
+        EVAL_NODE *op = eval_node_alloc(2);
         op->operator = operator;
         op->precedence = precedence;
 
-        operand_set_value_operand(op, 0, op1);
-        operand_set_value_operand(op, 1, op2);
+        eval_node_set_value_to_node(op, 0, op1);
+        eval_node_set_value_to_node(op, 1, op2);
 
         if(op->precedence > op1->precedence && op1->count == 2 && op1->operator != '(' && op1->ops[1].type == EVAL_VALUE_EXPRESSION) {
-            operand_set_value_operand(op, 0, op1->ops[1].expression);
+            eval_node_set_value_to_node(op, 0, op1->ops[1].expression);
             op1->ops[1].expression = op;
             op = op1;
         }
 
-        return parse_operand_rest(string, error, op);
+        return parse_rest_of_expression(string, error, op);
     }
     else if(**string == EVAL_OPERATOR_EXPRESSION_CLOSE) {
         ;
     }
     else if(**string) {
-        if(op1) operand_free(op1);
+        if(op1) eval_node_free(op1);
         op1 = NULL;
         *error = EVAL_ERROR_MISSING_OPERATOR;
     }
@@ -599,19 +597,58 @@ static inline EVAL_OPERAND *parse_operand_rest(const char **string, int *error,
     return op1;
 }
 
-static inline EVAL_OPERAND *parse_operand(const char **string, int *error) {
-    EVAL_OPERAND *op1 = NULL;
+static inline EVAL_NODE *parse_full_expression(const char **string, int *error) {
+    EVAL_NODE *op1 = NULL;
 
-    op1 = parse_operand1(string, error);
+    op1 = parse_one_full_operand(string, error);
     if(!op1) {
         *error = EVAL_ERROR_MISSING_OPERAND;
         return NULL;
     }
 
-    return parse_operand_rest(string, error, op1);
+    return parse_rest_of_expression(string, error, op1);
+}
+
+// ----------------------------------------------------------------------------
+// public API
+
+EVAL_NODE *expression_parse(const char *string, const char **failed_at, int *error) {
+    const char *s;
+    int err = EVAL_ERROR_OK;
+    unsigned long pos = 0;
+
+    s = string;
+    EVAL_NODE *op = parse_full_expression(&s, &err);
+
+    if (failed_at) *failed_at = s;
+    if (error) *error = err;
+
+    if(!op) {
+        pos = s - string + 1;
+        error("failed to parse expression '%s': %s at character %lu (i.e.: '%s').", string, expression_strerror(err), pos, s);
+    }
+
+    return op;
+}
+
+calculated_number expression_evaluate(EVAL_NODE *expression, int *error) {
+    int err = EVAL_ERROR_OK;
+    calculated_number ret = eval_node(expression, &err);
+
+    if(err != EVAL_ERROR_OK) {
+        error("Failed to execute expression with error %d (%s)", err, expression_strerror(err));
+        if(error) *error = err;
+        return 0;
+    }
+
+    return ret;
+}
+
+void expression_free(EVAL_NODE *op) {
+    if(op) eval_node_free(op);
 }
 
-const char *eval_error(int error) {
+const char *expression_strerror(int error) {
     switch(error) {
         case EVAL_ERROR_OK:
             return "success";
@@ -644,39 +681,3 @@ const char *eval_error(int error) {
             return "unknown error";
     }
 }
-
-EVAL_OPERAND *parse_expression(const char *string, const char **failed_at, int *error) {
-    const char *s;
-    int err = EVAL_ERROR_OK;
-    unsigned long pos = 0;
-
-    s = string;
-    EVAL_OPERAND *op = parse_operand(&s, &err);
-
-    if (failed_at) *failed_at = s;
-    if (error) *error = err;
-
-    if(!op) {
-        pos = s - string + 1;
-        error("failed to parse expression '%s': %s at character %lu (i.e.: '%s').", string, eval_error(err), pos, s);
-    }
-
-    return op;
-}
-
-calculated_number evaluate_expression(EVAL_OPERAND *expression, int *error) {
-    int err = EVAL_ERROR_OK;
-    calculated_number ret = eval_operand(expression, &err);
-
-    if(err != EVAL_ERROR_OK) {
-        error("Failed to execute expression with error %d (%s)", err, eval_error(err));
-        if(error) *error = err;
-        return 0;
-    }
-
-    return ret;
-}
-
-void free_expression(EVAL_OPERAND *op) {
-    if(op) operand_free(op);
-}
diff --git a/src/eval.h b/src/eval.h
index 157abc63bd..a645b31b07 100644
--- a/src/eval.h
+++ b/src/eval.h
@@ -12,7 +12,7 @@ typedef struct variable {
 #define EVAL_VALUE_VARIABLE 2
 #define EVAL_VALUE_EXPRESSION 3
 
-// these are used for EVAL_OPERAND.operator
+// these are used for EVAL_NODE.operator
 #define EVAL_OPERATOR_NOP                   '\0'
 #define EVAL_OPERATOR_VALUE                 ':'
 #define EVAL_OPERATOR_EXPRESSION_OPEN       '('
@@ -53,21 +53,22 @@ typedef struct eval_value {
     union {
         calculated_number number;
         VARIABLE *variable;
-        struct eval_operand *expression;
+        struct eval_node *expression;
     };
 } EVAL_VALUE;
 
-typedef struct eval_operand {
+typedef struct eval_node {
     int id;
     unsigned char operator;
     int precedence;
 
     int count;
     EVAL_VALUE ops[];
-} EVAL_OPERAND;
+} EVAL_NODE;
 
-extern EVAL_OPERAND *parse_expression(const char *string, const char **failed_at, int *error);
-extern calculated_number evaluate_expression(EVAL_OPERAND *expression, int *error);
-extern void free_expression(EVAL_OPERAND *op);
+extern EVAL_NODE *expression_parse(const char *string, const char **failed_at, int *error);
+extern calculated_number expression_evaluate(EVAL_NODE *expression, int *error);
+extern void expression_free(EVAL_NODE *op);
+extern const char *expression_strerror(int error);
 
 #endif //NETDATA_EVAL_H