Give an overview of how arrays are handled and represented in the typed parameters returned by the guest info API. Signed-off-by: Daniel P. Berrangé <berrange@xxxxxxxxxx> --- src/libvirt-domain.c | 50 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 50 insertions(+) diff --git a/src/libvirt-domain.c b/src/libvirt-domain.c index 5bb9f3895e..59fb923d10 100644 --- a/src/libvirt-domain.c +++ b/src/libvirt-domain.c @@ -12390,6 +12390,56 @@ virConnectGetDomainCapabilities(virConnectPtr conn, * VIR_CONNECT_GET_ALL_DOMAINS_STATS_SHUTOFF and/or * VIR_CONNECT_GET_ALL_DOMAINS_STATS_OTHER for all other states. * + * In a number of cases the parameters returned are representing + * arrays of data items. In these cases multiple VIR_DOMAIN_GUEST_INFO* + * constants will need to be concatenated to form a complete typed + * parameter key. The design pattern for handling array entries is + * as follows + * + * - VIR_DOMAIN_GUEST_INFO_nnnnn_COUNT + * + * Defines the upper limit on the number of elements that will + * be returned. In some cases the array information may be + * sparsely populated, so it is not considered an error if a + * given element does not exist. Applications should check for + * each possible element upto the declared limit. + * + * - VIR_DOMAIN_GUEST_INFO_nnnnn_PREFIX + * + * Defines the prefix to be used to construct the typed parameter + * key for an array element, including the trailing '.'. The prefix + * must have an array index appended, along with a suffix. + * + * - VIR_DOMAIN_GUEST_INFO_nnnnn_SUFFIX_mmmmm + * + * Defines the suffix for accessing a particular data item within + * the array element, including the leading '.'. The suffix must + * have an array prefix and index prepended. + * + * As an example, assuming a printf-like formatting approach an + * application would construct a key as follows: + * + * format(VIR_DOMAIN_STATS_CPU_CACHE_MONITOR_PREFIX + + * "%d" + + * VIR_DOMAIN_STATS_CPU_CACHE_MONITOR_SUFFIX_VCPUS + * index) + * + * Which, when index==3, would result in the key "cpu.cache.monitor.3.vcpus" + * + * In some cases there may be nested arrays, in which case the key + * is formed by concatenating multiple prefixes and suffixes with + * mutliple array indexes. For example: + * + * format(VIR_DOMAIN_STATS_CPU_CACHE_MONITOR_PREFIX + + * "%d" + + * VIR_DOMAIN_STATS_CPU_CACHE_MONITOR_SUFFIX_BANK_PREFIX + + * "%d" + + * VIR_DOMAIN_STATS_CPU_CACHE_MONITOR_SUFFIX_BANK_SUFFIX_BYTES + * monindex, bankindex) + * + * Which, when monindex==3 and bankindex==7, would result in the + * key "cpu.cache.monitor.3.bank.7.bytes". + * * Returns the count of returned statistics structures on success, -1 on error. * The requested data are returned in the @retStats parameter. The returned * array should be freed by the caller. See virDomainStatsRecordListFree. -- 2.48.1
