String Support

String creation, cloning, assignment, and deletion. More...

Functions
char *	DDS_String_alloc (DDS_UnsignedLong length)
	Create a new empty string that can hold up to length characters.
char *	DDS_String_dup (const char *str)
	Clone a string. Creates a new string that duplicates the value of string.
int	DDS_String_cmp (const char *s1, const char *s2)
	Compare two strings.
int	DDS_String_ncmp (const char *s1, const char *s2, DDS_UnsignedLong num)
	Compare two strings.
int	DDS_String_length (const char *string)
	Return the length of a string.
int	DDS_Wstring_cmp (const CDR_Wstring *s1, const CDR_Wstring *s2)
	Return the length of a string.

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Detailed Description

String creation, cloning, assignment, and deletion.

The functions in this class ensure consistent cross-platform implementations for string creation (DDS_String_alloc()), deletion (DDS_String_free()), and cloning (DDS_String_dup()) that preserve the mutable value type semantics. These are to be viewed as functions that define a string class whose data is represented by a 'char*'.

The following conventions govern the memory management of strings in RTI Connext Micro:

• The DDS implementation ensures that when value types containing strings are passed back and forth to the DDS APIs, the strings are created/deleted/assigned/cloned using the string class functions.
• Value types containing strings have ownership of the contained string. Thus, when a value type is deleted, the contained string field is also deleted.
• The user must ensure that when value types containing strings are passed back and forth to the DDS APIs, the strings are created/deleted/assigned/cloned using the String class functions.

The representation of a string in C/C++ unfortunately does not allow programs to detect how much memory has been allocated for a string. RTI Connext Micro must therefore make some assumptions when a user requests that a string be copied into. The following rules apply when RTI Connext Micro is copying into a string or string sequence:

• If the 'char*' is NULL, RTI Connext Micro will log a warning and allocate a new string on behalf of the user. To avoid leaking memory, you must ensure that the string will be freed (see below).
• If the 'char*' is not NULL, RTI Connext Micro will assume that you are managing the string's memory yourself and have allocated enough memory to store the string to be copied. RTI Connext Micro will copy into your memory; to avoid memory corruption, be sure to allocate enough of it. Also, do not pass structures containing junk pointers into RTI Connext Micro; you are likely to crash.

This requirement can generally be assured by adhering to the following idiom for manipulating strings:

• Always use DDS_String_alloc() to create a string
• Always use DDS_String_dup() to clone a string

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Function Documentation

char* DDS_String_alloc

(

DDS_UnsignedLong

length

)

Create a new empty string that can hold up to length characters.

This function will allocate enough memory to hold a string of length characters, plus one additional byte to hold the NULL terminating character.

Parameters:

length

<<in>> Capacity of the string.

Returns:

A newly created non-NULL string upon success or NULL upon failure.

MT Safety:

This operation is thread safe.

API Restriction:

This function must only be called after DDS_DomainParticipantFactory_get_instance.

char* DDS_String_dup

(

const char *

str

)

Clone a string. Creates a new string that duplicates the value of string.

Parameters:

str	<<in>> The string to duplicate.

Returns:

If string == NULL, this function always returns NULL. Otherwise, upon success it returns a newly created string whose value is string; upon failure it returns NULL.

MT Safety:

This operation is not thread safe.

API Restriction:

This function must only be called after DDS_DomainParticipantFactory_get_instance.

int DDS_String_cmp	(	const char *	s1,
		const char *	s2
	)

Compare two strings.

Precondition:

s1 and s2 can be NULL or non-NULL.

Parameters:

s1	<<in>> String 1 to compare.
s2	<<in>> String 2 to compare.

Returns:

0 if s1 equals s2, positive integer if s1 is greater than s2, negative integer if s1 is less than s2

MT Safety:

This operation is not thread safe.

int DDS_String_ncmp	(	const char *	s1,
		const char *	s2,
		DDS_UnsignedLong	num
	)

Compare two strings.

This function compares two strings for lexicographic equivalence, but only up to num bytes.

Parameters:

[in]	s1	<<in>> Left side of comparison
[in]	s2	<<in>> Right side of comparison
[in]	num	Maximum number of bytes to compare

Returns:

0 if s1 equals s2, positive integer if s1 is greater than s2, negative integer if s1 is less than s2

MT Safety:

This operation is not thread safe.

int DDS_String_length

(

const char *

string

)

Return the length of a string.

Precondition:

string must be non-NULL

Parameters:

string

<<in>> String to return length of

Returns:

length of string. Does not include the NUL-termination character. If a NULL value is passed as argument, RTI_SIZE_INVALID will be returned.

MT Safety:

This operation is not thread safe.

int DDS_Wstring_cmp	(	const CDR_Wstring *	s1,
		const CDR_Wstring *	s2
	)

Return the length of a string.

Precondition:

s1 and s2 can be NULL or non-NULL.

Parameters:

s1	<<in>> String 1 to compare.
s2	<<in>> String 2 to compare.

Returns:

0 if s1 equals s2, positive integer if s1 is greater than s2, negative integer if s1 is less than s2

MT Safety:

This operation is not thread safe.