ulong    order;
           Rsobj_t* left;
           Rsobj_t* right;
           Rsobj_t* equal;
           uchar*   key;
           ssize_t  keylen;
           uchar*   data;
           ssize_t  datalen;

order, left:

These fields are only significant in calls to event functions raised by method Rsverify.

right, equal:

The rslist() call returns a linked list of sorted records. obj->right defines the forward link for obj. obj->equal, if not NULL, points to a NULL-terminated linked list of records compared equal to obj.

key, keylen, data, datalen:

These fields define the key and data of the given record.

c_max:

Due to memory cache behavior, it is sometimes worthwhile to limit the amount of data sorted by a sort method at any given time. Data across calls to rsprocess() accumulated for a sort method is limited as follows. If c_max < 0, there is no limit. If c_max = 0, each rsprocess() call sorts data separately. If c_max > 0, data will be accumulated up to c_max before sorted. Thus, when c_max >= 0, many sorted list of records may result. These lists will be merged together in a rslist() or rswrite() call.

type:

This is a bit combination of: (1) RS_UNIQ, keeping only one in a set of duplicated records, (2) RS_REVERSE, sorting records in reverse order, and (3) RS_DATA, comparing records by keys, then by data.

Sort methods are of type Rsmethod_t*. The fields int Rsmethod_t.type and char* Rsmethod_t.name contain the method type and name respectively.

Object key management is defined in the type Rsdisc_t:

         typedef struct
         { int        type;
           ssize_t    data;
           ssize_t    key;
           ssize_t    keylen;
           Rsdefkey_f defkeyf;
           Rsevent_f  eventf;
         } Rsdisc_t;

If Rsdisc_t.defkeyf is not NULL, it is called to define a key. The key should be constructed in the given area key whose size is s_key. s_key is guaranteed to be at least Rsdisc_t.key*s_data. Rsdisc_t.defkeyf should return the length of the key or a negative value on error.

RS_CLOSE:

This event is raised when rs is about to be closed. The associated data is NULL.

RS_DISC:

This event is raised when the discipline is about to be changed. (Sfdisc_t*)data is the new discipline.

RS_METHOD:

This event is raised when the method is about to be changed. (Sfmethod_t*)data is the new method.

RS_VERIFY:

This event is raised when method Rsverify detects a record, r=(Rsobj_t*)data, out of order with respect to a previous record p. There are three cases. If r compares equal with p and RS_UNIQ is on, then r->equal is p. If r compares less than p and RS_REVERSE is off, then r->right is p. Finally, if r compares larger than p and RS_REVERSE is on, then r->left is p.

r->order and p->order are the ordinal positions of r and p in the stream of records.

The return value of eventf is significant as follows. If it is negative, the verification process is aborted. If it is zero, the verification process continues as if r did not exist. If it is positive, the verification process continues as if r was in order.