eXternal <a href="http://www.setgetweb.com/p/iSeries/v5r3/eXternal">Data Representation</a> (XDR)

Integrated File System Introduction

eXternal Data Representation (XDR)

The following APIs allow Remote Procedure Call (RPC) applications to handle arbitrary data structures, regardless of their different hosts' byte orders or structure layout conventions.

API Description
xdr_array() A filter primitive that translates between variable-length arrays and their corresponding external representations. This function is called to encode or decode each element of the array
xdr_bool() A filter primitive that translates between Booleans (C integers) and their external representations. When encoding data, this filter produces values of either 1 or 0.
xdr_bytes() A filter primitive that translates between counted byte arrays and their external representations. This function treats a subset of generic arrays in which the size of array elements is known to be 1 and the external description of each element is built-in. The length of the byte sequence is explicitly located in an unsigned integer. The byte sequence is not ended by a null character. The external representation of the bytes is the same as their internal representation.
xdr_char() A filter primitive that translates between C-language characters and their external representation
xdr_double() A filter primitive that translates between C-language double-precision numbers and their external representations
xdr_double_char() A filter primitive that translates between C-language 2-byte characters and their external representation
xdr_enum() A filter primitive that translates between C-language enumeration (enum) and its external representation
xdr_free() Recursively frees the object pointed to by the pointer passed in
xdr_float() A filter primitive that translates between C-language floating-point numbers (normalized single floating-point numbers) and their external representations
xdr_int() A filter primitive that translates between C-language integers and their external representation
xdr_long() A filter primitive that translates between C-language long integers and their external representations
xdr_netobj() A filter primitive that translates between variable-length opaque data and its external representation
xdr_opaque() Afilter primitive that translates between fixed-size opaque data and its external representation
xdr_pointer() Provides pointer chasing within structures and serializes null pointers. Can represent recursive data structures, such as binary trees or linked lists.
xdr_reference() a filter primitive that provides pointer chasing within structures. This primitive allows the serializing, deserializing, and freeing of any pointers within one structure that are referenced by another structure. The xdr_reference() function does not attach special meaning to a null pointer during serialization, and passing the address of a null pointer may cause a memory error. Therefore, the programmer must describe data with a two-sided discriminated union. One side is used when the pointer is valid; the other side, when the pointer is null.
xdr_short() A filter primitive that translates between C-language short integers and their external representation
xdr_string() A filter primitive that translates between C-language strings and their corresponding external representations
xdr_u_char() A filter primitive that translates between unsigned C-language characters and their external representations
xdr_u_int() A filter primitive that translates between C-language unsigned integers and their external representations
xdr_u_long() A filter primitive that translates between C-language unsigned long integers and their external representations
xdr_u_short() A filter primitive that translates between C-language unsigned short integers and their external representations
xdr_union() A filter primitive that translates between discriminated C unions and their corresponding external representations
xdr_vector() A filter primitive that translates between fixed-length arrays and their corresponding external representations
xdr_void() Has no parameters. It is passed to other RPC functions that require a parameter, but does not transmit data
xdr_wrapstring() A primitive that calls the xdr_string(xdr, sp, maxuint) API, where maxuint is the maximum value of an unsigned integer. The xdr_wrapstring() is useful because the RPC package passes a maximum of two XDR functions as parameters, and the xdr_string() function requires three.

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API	Description
xdr_array()	A filter primitive that translates between variable-length arrays and their corresponding external representations. This function is called to encode or decode each element of the array
xdr_bool()	A filter primitive that translates between Booleans (C integers) and their external representations. When encoding data, this filter produces values of either 1 or 0.
xdr_bytes()	A filter primitive that translates between counted byte arrays and their external representations. This function treats a subset of generic arrays in which the size of array elements is known to be 1 and the external description of each element is built-in. The length of the byte sequence is explicitly located in an unsigned integer. The byte sequence is not ended by a null character. The external representation of the bytes is the same as their internal representation.
xdr_char()	A filter primitive that translates between C-language characters and their external representation
xdr_double()	A filter primitive that translates between C-language double-precision numbers and their external representations
xdr_double_char()	A filter primitive that translates between C-language 2-byte characters and their external representation
xdr_enum()	A filter primitive that translates between C-language enumeration (enum) and its external representation
xdr_free()	Recursively frees the object pointed to by the pointer passed in
xdr_float()	A filter primitive that translates between C-language floating-point numbers (normalized single floating-point numbers) and their external representations
xdr_int()	A filter primitive that translates between C-language integers and their external representation
xdr_long()	A filter primitive that translates between C-language long integers and their external representations
xdr_netobj()	A filter primitive that translates between variable-length opaque data and its external representation
xdr_opaque()	Afilter primitive that translates between fixed-size opaque data and its external representation
xdr_pointer()	Provides pointer chasing within structures and serializes null pointers. Can represent recursive data structures, such as binary trees or linked lists.
xdr_reference()	a filter primitive that provides pointer chasing within structures. This primitive allows the serializing, deserializing, and freeing of any pointers within one structure that are referenced by another structure. The xdr_reference() function does not attach special meaning to a null pointer during serialization, and passing the address of a null pointer may cause a memory error. Therefore, the programmer must describe data with a two-sided discriminated union. One side is used when the pointer is valid; the other side, when the pointer is null.
xdr_short()	A filter primitive that translates between C-language short integers and their external representation
xdr_string()	A filter primitive that translates between C-language strings and their corresponding external representations
xdr_u_char()	A filter primitive that translates between unsigned C-language characters and their external representations
xdr_u_int()	A filter primitive that translates between C-language unsigned integers and their external representations
xdr_u_long()	A filter primitive that translates between C-language unsigned long integers and their external representations
xdr_u_short()	A filter primitive that translates between C-language unsigned short integers and their external representations
xdr_union()	A filter primitive that translates between discriminated C unions and their corresponding external representations
xdr_vector()	A filter primitive that translates between fixed-length arrays and their corresponding external representations
xdr_void()	Has no parameters. It is passed to other RPC functions that require a parameter, but does not transmit data
xdr_wrapstring()	A primitive that calls the xdr_string(xdr, sp, maxuint) API, where maxuint is the maximum value of an unsigned integer. The xdr_wrapstring() is useful because the RPC package passes a maximum of two XDR functions as parameters, and the xdr_string() function requires three.