Pike Manual

17.2.2 struct svalue

An svalue is the most central data structure in the Pike interpreter. It is used to hold values on the stack, local variables, items in arrays and mappings and a lot more. Any of the data types described in chapter 4 "Data types" can be stored in an svalue.

A struct svalue has three members:

short type;

This says what type of value is actually stored in the svalue. Valid values are T_INT, T_FLOAT, T_STRING, T_ARRAY, T_MAPPING, T_MULTISET, T_FUNCTION, T_PROGRAM, T_OBJECT. In certain situations, other values are used in the type field, but those are reserved for internal Pike use only.

short subtype;

union anything u

This union contains the data. Depending on what the type member is, you can access one of the following union members:

`type` is:	member to use:	notes:
`T_INT`	`INT_TYPE integer`
`T_FLOAT`	`FLOAT_TYPE float_number`
`T_STRING`	`struct pike_string *string`
`T_ARRAY`	`struct array *array`
`T_MAPPING`	`struct mapping *mapping`
`T_MULTISET`	`struct multiset *multiset`
`T_OBJECT`	`struct object *object`
`T_PROGRAM`	`struct program *program`
`T_FUNCTION`	`struct callable *efun`	If `subtype == FUNCTION_BUILTIN`
`T_FUNCTION`	`struct object *object`	If `subtype != FUNCTION_BUILTIN`

Of course there are a whole bunch of functions for operating on svalues:

FUNCTION: free_svalue - free the contents of an svalue
SYNTAX: void free_svalue(struct svalue *s);
DESCRIPTION: This function is actually a macro, it will the contents of s. It does not however free s itself. After calling free_svalue, the contents of s is undefined, and you should not be surprised if your computer blows up if you try to access the it's contents. Also note that this doesn't nessecarily free whatever the svalue is pointing to, it only frees one reference. If that reference is the last one, the object/array/mapping/whatever will indeed be freed.
NOTE: This function will *not* call Pike code or error().

FUNCTION: free_svalues - free many svalues
SYNTAX: void free_svalues(struct svalue *s, INT32 howmany, TYPE_FIELD type_hint);
DESCRIPTION: This function does the same as free_svalue but operates on several svalues. The type_hint is used for optimization and should be set to BIT_MIXED if you don't know exactly what types are beeing freed.
NOTE: This function will *not* call Pike code or error().
SEE ALSO

FUNCTION: assign_svalue - copy an svalue to another svalue
SYNTAX: void assign_svalue(struct svalue *to, sstruct svalue *from);
DESCRIPTION: This function frees the contents of to and then copies the contents of from into to. If the value in from uses refcounts, they will be increased to reflect this copy.
NOTE: This function will *not* call Pike code or error().
SEE ALSO

FUNCTION: assign_svalue_no_free - copy an svalue to another svalue
SYNTAX: void assign_svalue_no_free(struct svalue *to, sstruct svalue *from);
DESCRIPTION: This function does the same as assign_svalue() but does not free the contents of to before overwriting it. This should be used when to has not been initialized yet. If this funcion is incorrectly, memory leaks will occur. On the other hand, if you call assign_svalue on an uninitialized svalue, a core dump or bus error will most likely occur.
NOTE: This function will *not* call Pike code or error().
SEE ALSO

FUNCTION: IS_ZERO - check if an svalue is true or false
SYNTAX: int IS_ZERO(struct svalue *s);
DESCRIPTION: This macro returns 1 if s is false and 0 if s is true.
NOTE: This macro will evaluate s several times.
This macro may call Pike code and/or error().
SEE ALSO

FUNCTION: is_eq - check if two svalues contains the same value
SYNTAX: int is_eq(struct svalue *a, struct svalue *b);
DESCRIPTION: This function returns 1 if a and b contain the same value. This is the same as the `== operator in pike.
NOTE: This function may call Pike code and/or error().
SEE ALSO

FUNCTION: is_equal - check if two svalues are equal
SYNTAX: int is_equal(struct svalue *a, struct svalue *b);
DESCRIPTION: This function returns 1 if a and b contains equal values. This is the same as the function equal in pike.
NOTE: This function may call Pike code and/or error().
SEE ALSO

FUNCTION: is_lt - compare the contents of two svalues
SYNTAX: int is_lt(struct svalue *a, struct svalue *b); int is_le(struct svalue *a, struct svalue *b); int is_gt(struct svalue *a, struct svalue *b); int is_ge(struct svalue *a, struct svalue *b);
DESCRIPTION: These functions are equal to the pike operators `<, `<=, `>, `>= respectively. For instance is_lt will return 1 if the contents of a is lesser than the contents of b.
NOTE: This function may call Pike code and/or error(). For instance, it will call error() if you try to compare values which cannot be compared such as comparing an integer to an array.
SEE ALSO

Previous section

To contents

Next section