c++/sqlite-demo-modul/demo.cpp
author František Kučera <franta-hg@frantovo.cz>
Fri, 15 May 2020 20:32:37 +0200
changeset 59 d6614ad97bed
parent 58 2f84ed5f3abf
permissions -rw-r--r--
LV2: modul zesilovače, dle oficiálního příkladu, ale bez závislosti na Pythonu – stačí gcc a make
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#include <cstdio>
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#include <sqlite3ext.h>
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#include <unistd.h>
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/**
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 * This is just an example – use official documentation: https://www.sqlite.org/loadext.html
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 */
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#define C_API extern "C"
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#define SQL_FN(functionName) void functionName (sqlite3_context* ctx, int valueCount, sqlite3_value** values)
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SQLITE_EXTENSION_INIT1
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/**
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 * Returns number of values passed to the SQL function.
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 */
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SQL_FN(valueCount) {
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	sqlite3_result_int(ctx, valueCount);
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}
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/**
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 * Returns current PID (process id).
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 */
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SQL_FN(getPID) {
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	sqlite3_result_int(ctx, getpid());
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}
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/**
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 * Returns multiplication of all arguments or zero, if there are no arguments.
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 */
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SQL_FN(multiply) {
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	sqlite3_int64 result = valueCount == 0 ? 0 : 1;
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	for (int i = 0; i < valueCount; i++) result *= sqlite3_value_int64(values[i]);
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	sqlite3_result_int64(ctx, result);
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}
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/**
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 * Function name should match the library file name: libdemo.so → sqlite3_demo_init.
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 * Or we can specify different entry point when loading the module.
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 */
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C_API int sqlite3_demo_init(sqlite3* db, char** error, const sqlite3_api_routines* api) {
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	SQLITE_EXTENSION_INIT2(api);
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	sqlite3_create_function(db, "value_count", -1, SQLITE_UTF8, nullptr, valueCount, nullptr, nullptr);
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	sqlite3_create_function(db, "get_pid", 0, SQLITE_UTF8, nullptr, getPID, nullptr, nullptr);
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	sqlite3_create_function(db, "multiply", -1, SQLITE_UTF8, nullptr, multiply, nullptr, nullptr);
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	// -1 = function accepts arbitrary number of arguments
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	return SQLITE_OK;
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}