__pmParseHostSpec, __pmUnparseHostSpec, __pmFreeHostSpec - uniform host specification parser

#include "pmapi.h"
#include "libpcp.h"

int __pmParseHostSpec(const char *string, __pmHostSpec **hostsp, int *count, char **errmsg);
int __pmUnparseHostSpec(__pmHostSpec *hosts, int count, char *string, size_t size);
void __pmFreeHostSpec(__pmHostSpec *hosts, int count);

cc ... -lpcp

This documentation is intended for internal Performance Co-Pilot (PCP) developer use.

These interfaces are not part of the PCP APIs that are guaranteed to remain fixed across releases, and they may not work, or may provide different semantics at some point in the future.

__pmParseHostSpec accepts a string specifying the location of a PCP performance metric collector daemon. The syntax of the various formats of this string is described in PCPIntro(1) where several examples are also presented.

The syntax allows the initial pmcd(1) hostname to be optionally followed by a list of port numbers, which will be tried in order when connecting to pmcd on that host. The list of port numbers is separated from the hostname using a colon, and each port in the list is comma-separated.

In addition, one or more optional pmproxy(1) hosts can be specified (currently, only one proxy host is supported by the PCP protocols). These are separated from each other and from the pmcd component using the @ character. These may also be followed by an optional port list, using the same comma-separated syntax as before.

__pmParseHostSpec takes a null-terminated host specification string and returns an array of __pmHostSpec structures, where the array has count entries.

These __pmHostSpec structures that are returned via hostsp represent each individual host in the specification string and has the following declaration:

    typedef struct {
        char    *name;       /* hostname (always valid) */
        int     *ports;      /* array of host port numbers */
        int     nports;      /* number of ports in host port array */
    } __pmHostSpec;

__pmUnparseHostSpec performs the inverse operation, creating a string representation from a number of hosts structures. Where the count of structures indicated by hosts is greater than one, the proxy syntax is used to indicate a chain of proxied hosts. The size of the supplied string buffer must be provided by the caller using the size parameter.

If the given string is successfully parsed __pmParseHostSpec returns zero. In this case the dynamic storage allocated by __pmParseHostSpec can be released by calling __pmFreeHostSpec using the address returned from __pmParseHostSpec via hosts.

__pmParseHostSpec returns PM_ERR_GENERIC and a dynamically allocated error message string in errmsg, if the given string does not parse, and the user-supplied errmsg pointer is non-null. Be sure to free(3) the error message string in this situation.

In the case of an error, hosts is undefined. In the case of success, errmsg is undefined.

On success __pmUnparseHostSpec returns a positive value indicating the number of characters written into the supplied buffer. However, if the supplied buffer was too small, a negative status code of -E2BIG is returned.

pmcd(1), pmproxy(1), pmchart(1), __pmParseHostAttrsSpec(3), PMAPI(3) and pmNewContext(3).

PCP Performance Co-Pilot