65 lines
2.7 KiB
C
65 lines
2.7 KiB
C
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// Compile with clang or gcc:
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// clang -Wall -shared -fPIC -I <path-to-memgraph-include> example.c -o example.so
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// <path-to-memgraph-include> for installed Memgraph will usually be something
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// like `/usr/include/memgraph` or `/usr/local/include/memgraph`.
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// To use the compiled module, you need to run Memgraph configured to load
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// modules from the directory where the compiled module can be found.
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#include "mg_procedure.h"
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// This example procedure returns 2 fields: `args` and `result`.
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// * `args` is a copy of arguments passed to the procedure.
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// * `result` is the result of this procedure, a "Hello World!" string.
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// In case of memory errors, this function will report them and finish executing.
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//
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// The procedure can be invoked in openCypher using the following call:
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// CALL example(1, 2, 3) YIELD args, result;
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// Naturally, you may pass in different arguments or yield less fields.
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void mgp_main(const struct mgp_list *args, const struct mgp_graph *graph,
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struct mgp_result *result, struct mgp_memory *memory) {
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struct mgp_list *args_copy = mgp_list_make_empty(mgp_list_size(args), memory);
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if (args_copy == NULL) goto error_memory;
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for (size_t i = 0; i < mgp_list_size(args); ++i) {
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int success = mgp_list_append(args_copy, mgp_list_at(args, i));
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if (!success) goto error_free_list;
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}
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struct mgp_result_record *record = mgp_result_new_record(result);
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if (record == NULL) goto error_free_list;
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// Transfer ownership of args_copy to mgp_value.
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struct mgp_value *args_value = mgp_value_make_list(args_copy);
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if (args_value == NULL) goto error_free_list;
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int args_inserted = mgp_result_record_insert(record, "args", args_value);
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// Release `args_value` and contained `args_copy`.
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mgp_value_destroy(args_value);
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if (!args_inserted) goto error_memory;
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struct mgp_value *hello_world_value =
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mgp_value_make_string("Hello World!", memory);
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if (hello_world_value == NULL) goto error_memory;
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int result_inserted =
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mgp_result_record_insert(record, "result", hello_world_value);
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mgp_value_destroy(hello_world_value);
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if (!result_inserted) goto error_memory;
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// We have successfully finished, so return without error reporting.
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return;
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error_free_list:
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mgp_list_destroy(args_copy);
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error_memory:
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mgp_result_set_error_msg(result, "Not enough memory!");
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return;
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}
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// This is an optional function if you need to initialize any global state when
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// your module is loaded.
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int mgp_init_module() {
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// Return 0 to indicate success.
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return 0;
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}
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// This is an optional function if you need to release any resources before the
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// module is unloaded. You will probably need this if you acquired some
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// resources in mgp_init_module.
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int mgp_shutdown_module() {
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// Return 0 to indicate success.
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return 0;
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}
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