Struct DataSourceVTable 

#[repr(C)]
pub struct DataSourceVTable {
    pub init: Option<unsafe extern "C" fn(*const u8, usize) -> *mut c_void>,
    pub get_query_schema: Option<unsafe extern "C" fn(*mut c_void) -> *const QuerySchema>,
    pub get_output_schema: Option<unsafe extern "C" fn(*mut c_void) -> *const OutputSchema>,
    pub get_source_schema: Option<unsafe extern "C" fn(*mut c_void, *const u8, usize, *mut *mut u8, *mut usize) -> i32>,
    pub validate_query: Option<unsafe extern "C" fn(*mut c_void, *const u8, usize, *mut *mut i8) -> i32>,
    pub load: Option<unsafe extern "C" fn(*mut c_void, *const u8, usize, *mut *mut u8, *mut usize) -> i32>,
    pub load_binary: Option<unsafe extern "C" fn(*mut c_void, *const u8, usize, u8, Option<unsafe extern "C" fn(u8, u64, u64, u64, *mut c_void) -> i32>, *mut c_void, *mut *mut u8, *mut usize) -> i32>,
    pub subscribe: Option<unsafe extern "C" fn(*mut c_void, *const u8, usize, unsafe extern "C" fn(*const u8, usize, *mut c_void), *mut c_void) -> u64>,
    pub unsubscribe: Option<unsafe extern "C" fn(*mut c_void, u64) -> i32>,
    pub free_buffer: Option<unsafe extern "C" fn(*mut u8, usize)>,
    pub free_string: Option<unsafe extern "C" fn(*mut i8)>,
    pub drop: Option<unsafe extern "C" fn(*mut c_void)>,
}

Function pointer types for data source plugins

Fields

init: Option<unsafe extern "C" fn(*const u8, usize) -> *mut c_void>

Initialize the data source with configuration. config: MessagePack-encoded configuration object Returns: opaque instance pointer, or null on error

get_query_schema: Option<unsafe extern "C" fn(*mut c_void) -> *const QuerySchema>

Get the query schema for this data source. Returns a pointer to the QuerySchema struct (must remain valid for plugin lifetime).

get_output_schema: Option<unsafe extern "C" fn(*mut c_void) -> *const OutputSchema>

Get the output schema for this data source. Returns a pointer to the OutputSchema struct (must remain valid for plugin lifetime).

get_source_schema: Option<unsafe extern "C" fn(*mut c_void, *const u8, usize, *mut *mut u8, *mut usize) -> i32>

Query the data schema for a specific source.

Unlike get_output_schema which returns a static schema for the plugin, this function returns the dynamic schema for a specific data source. This enables schema discovery at runtime.

source_id: The source identifier (e.g., table name, symbol, device ID) out_ptr: Output pointer to MessagePack-encoded PluginSchema out_len: Output length of the data

The returned PluginSchema (MessagePack) has structure:

{
  "columns": [
    { "name": "timestamp", "data_type": "Timestamp" },
    { "name": "value", "data_type": "Number" }
  ],
  "timestamp_column": "timestamp"
}

Returns: 0 on success, non-zero error code on failure Caller must free the output buffer with free_buffer.

validate_query: Option<unsafe extern "C" fn(*mut c_void, *const u8, usize, *mut *mut i8) -> i32>

Validate a query before execution. query: MessagePack-encoded query parameters out_error: On error, write error message pointer here (caller must free with free_string) Returns: 0 on success, non-zero error code on failure

load: Option<unsafe extern "C" fn(*mut c_void, *const u8, usize, *mut *mut u8, *mut usize) -> i32>

Load historical data (JSON/MessagePack format - legacy). query: MessagePack-encoded query parameters out_ptr: Output pointer to MessagePack-encoded Series data out_len: Output length of the data Returns: 0 on success, non-zero error code on failure Caller must free the output buffer with free_buffer.

load_binary: Option<unsafe extern "C" fn(*mut c_void, *const u8, usize, u8, Option<unsafe extern "C" fn(u8, u64, u64, u64, *mut c_void) -> i32>, *mut c_void, *mut *mut u8, *mut usize) -> i32>

Load historical data in binary columnar format (ABI v2).

High-performance data loading that bypasses JSON serialization. Returns binary data in the format defined by binary_format module that can be directly mapped to SeriesStorage.

Arguments

• instance: Plugin instance
• query: MessagePack-encoded query parameters
• query_len: Length of query data
• granularity: Progress reporting granularity (0=Coarse, 1=Fine)
• progress_callback: Optional callback for progress reporting
• progress_user_data: User data passed to progress callback
• out_ptr: Output pointer to binary columnar data
• out_len: Output length of the data

Returns: 0 on success, non-zero error code on failure Caller must free the output buffer with free_buffer.

subscribe: Option<unsafe extern "C" fn(*mut c_void, *const u8, usize, unsafe extern "C" fn(*const u8, usize, *mut c_void), *mut c_void) -> u64>

Subscribe to streaming data. query: MessagePack-encoded query parameters callback: Called for each data point (data_ptr, data_len, user_data) callback_data: User data passed to callback Returns: subscription ID on success, 0 on failure

unsubscribe: Option<unsafe extern "C" fn(*mut c_void, u64) -> i32>

Unsubscribe from streaming data. subscription_id: ID returned by subscribe Returns: 0 on success, non-zero on failure

free_buffer: Option<unsafe extern "C" fn(*mut u8, usize)>

Free a buffer allocated by load.

free_string: Option<unsafe extern "C" fn(*mut i8)>

Free an error string allocated by validate_query.

drop: Option<unsafe extern "C" fn(*mut c_void)>

Cleanup and destroy the instance.