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//! Abstraction on top of the MongoDB connection read prefences.
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use crate::mongoc::bindings;
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/// Describes how reads should be dispatched.
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pub enum ReadMode {
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/// Default mode. All operations read from the current replica set primary.
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Primary,
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/// All operations read from among the nearest secondary members of the replica set.
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Secondary,
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/// In most situations, operations read from the primary but if it is unavailable, operations read from secondary members.
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PrimaryPreferred,
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/// In most situations, operations read from among the nearest secondary members, but if no secondaries are available, operations read from the primary.
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SecondaryPreferred,
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/// Operations read from among the nearest members of the replica set, irrespective of the member’s type.
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Nearest
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}
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fn read_mode_value(read_mode: &ReadMode) -> bindings::mongoc_read_mode_t {
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match read_mode {
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&ReadMode::Primary => bindings::MONGOC_READ_PRIMARY,
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&ReadMode::Secondary => bindings::MONGOC_READ_SECONDARY,
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&ReadMode::PrimaryPreferred => bindings::MONGOC_READ_PRIMARY_PREFERRED,
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&ReadMode::SecondaryPreferred => bindings::MONGOC_READ_SECONDARY_PREFERRED,
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&ReadMode::Nearest => bindings::MONGOC_READ_NEAREST
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}
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}
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/// Provides an abstraction on top of the MongoDB connection read prefences.
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///
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/// It allows for hinting to the driver which nodes in a replica set should be accessed first.
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/// Generally, it makes the most sense to stick with the global default, `Primary`. All of the other modes come with caveats that won't be covered in great detail here.
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pub struct ReadPrefs {
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inner: *mut bindings::mongoc_read_prefs_t
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}
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impl ReadPrefs {
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/// Create a new empty read prefs.
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pub fn new(read_mode: &ReadMode) -> ReadPrefs {
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let read_mode_value = read_mode_value(read_mode);
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let inner = unsafe { bindings::mongoc_read_prefs_new(read_mode_value) };
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assert!(!inner.is_null());
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ReadPrefs { inner: inner }
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}
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/// Get a new instance of the default read pref.
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pub fn default() -> ReadPrefs{
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ReadPrefs::new(&ReadMode::Primary)
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}
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#[doc(hidden)]
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pub fn inner(&self) -> *const bindings::mongoc_read_prefs_t {
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assert!(!self.inner.is_null());
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self.inner
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}
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#[doc(hidden)]
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pub fn mut_inner(&self) -> *mut bindings::mongoc_read_prefs_t {
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assert!(!self.inner.is_null());
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self.inner as *mut bindings::mongoc_read_prefs_t
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}
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}
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impl Drop for ReadPrefs {
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fn drop(&mut self) {
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assert!(!self.inner.is_null());
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unsafe {
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bindings::mongoc_read_prefs_destroy(self.inner);
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}
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}
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}
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