vlib: add a vlib/mssql module (#10280)

vlib/mssql/stmt_handle.v

@@ -0,0 +1,127 @@
+module mssql
+
+// HStmt is handle for sql statement
+struct HStmt {
+mut:
+	// db connection reference. Owner is Connection struct.
+	hdbc C.SQLHDBC = C.SQLHDBC(C.SQL_NULL_HDBC)
+	// statement handle
+	hstmt C.SQLHSTMT = C.SQLHSTMT(C.SQL_NULL_HSTMT)
+	// fields used for computation
+	column_count int = -1
+	// columns
+	buffers [][]char
+	// indicators for each column
+	indicators []C.SQLLEN
+}
+
+// new_hstmt constructs a new statement handle
+fn new_hstmt(hdbc C.SQLHDBC) ?HStmt {
+	mut retcode := C.SQLRETURN(C.SQL_SUCCESS)
+	mut hstmt := C.SQLHSTMT(C.SQL_NULL_HSTMT)
+	// Allocate statement handle
+	retcode = C.SQLAllocHandle(C.SQLSMALLINT(C.SQL_HANDLE_STMT), C.SQLHANDLE(hdbc), unsafe { &C.SQLHANDLE(&hstmt) })
+	check_error(retcode, 'SQLAllocHandle(SQL_HANDLE_STMT)', C.SQLHANDLE(hstmt), C.SQLSMALLINT(C.SQL_HANDLE_STMT)) ?
+
+	return HStmt{
+		hdbc: hdbc
+		hstmt: hstmt
+	}
+}
+
+// close the statement handle
+fn (mut h HStmt) close() {
+	// Deallocate handle
+	if h.hstmt != C.SQLHSTMT(C.SQL_NULL_HSTMT) {
+		// check error code?
+		C.SQLFreeHandle(C.SQLSMALLINT(C.SQL_HANDLE_STMT), C.SQLHANDLE(h.hstmt))
+		h.hstmt = C.SQLHSTMT(C.SQL_NULL_HSTMT)
+	}
+}
+
+// exec executes a Sql statement. Result is stored in odbc driver, and not yet read.
+fn (h HStmt) exec(sql string) ? {
+	retcode := C.SQLExecDirect(h.hstmt, sql.str, C.SQLINTEGER(C.SQL_NTS))
+	check_error(retcode, 'SQLExecDirect()', C.SQLHANDLE(h.hstmt), C.SQLSMALLINT(C.SQL_HANDLE_STMT)) ?
+}
+
+// retrieve_affected_rows returns number of rows affected/modified by the last operation. -1 if not applicable.
+fn (h HStmt) retrieve_affected_rows() ?int {
+	count_ret := C.SQLLEN(0)
+	retcode := C.SQLRowCount(h.hstmt, &count_ret)
+	check_error(retcode, 'SQLRowCount()', C.SQLHANDLE(h.hstmt), C.SQLSMALLINT(C.SQL_HANDLE_STMT)) ?
+	return int(count_ret)
+}
+
+fn (h HStmt) retrieve_column_count() ?int {
+	mut retcode := C.SQLRETURN(C.SQL_SUCCESS)
+	col_count_buff := C.SQLSMALLINT(0)
+	retcode = C.SQLNumResultCols(h.hstmt, &col_count_buff)
+	check_error(retcode, 'SQLNumResultCols()', C.SQLHANDLE(h.hstmt), C.SQLSMALLINT(C.SQL_HANDLE_STMT)) ?
+	return int(col_count_buff)
+}
+
+// allocate buffers and bind them to drivers
+fn (mut h HStmt) prepare_read() ? {
+	mut retcode := C.SQLRETURN(C.SQL_SUCCESS)
+
+	column_count := h.retrieve_column_count() ?
+	h.column_count = column_count // remember the count because read will need it
+
+	h.buffers = [][]char{len: h.column_count, cap: h.column_count}
+	h.indicators = []C.SQLLEN{len: h.column_count, cap: h.column_count}
+
+	for i := 0; i < h.column_count; i++ {
+		i_col := C.SQLUSMALLINT(i + 1) // col number starts with 1
+		size_ret := C.SQLLEN(0)
+		// find out buffer size needed to read data in this column
+		retcode = C.SQLColAttribute(h.hstmt, i_col, C.SQLUSMALLINT(C.SQL_DESC_LENGTH),
+			C.SQLPOINTER(0), C.SQLSMALLINT(0), C.SQLSMALLINT(0), &size_ret)
+		check_error(retcode, 'SQLColAttribute()', C.SQLHANDLE(h.hstmt), C.SQLSMALLINT(C.SQL_HANDLE_STMT)) ?
+
+		// buffer allocation is the size + 1 to include termination char, since SQL_DESC_LENGTH does not include it.
+		allocate_size := size_ret + C.SQLLEN(1)
+		allocate_size_int := int(allocate_size)
+		buff := []char{len: allocate_size_int, cap: allocate_size_int}
+
+		// bind the buffer
+		retcode = C.SQLBindCol(h.hstmt, C.SQLUSMALLINT(i_col), C.SQLSMALLINT(C.SQL_C_CHAR),
+			C.SQLPOINTER(&buff[0]), allocate_size, &h.indicators[i])
+		check_error(retcode, 'SQLBindCol()', C.SQLHANDLE(h.hstmt), C.SQLSMALLINT(C.SQL_HANDLE_STMT)) ?
+
+		// record the buffer in HStmt
+		h.buffers[i] = buff
+	}
+}
+
+// fetch all rows
+fn (h HStmt) read_rows() ?[][]string {
+	mut retcode := C.SQLRETURN(C.SQL_SUCCESS)
+
+	mut res := [][]string{}
+
+	if h.column_count <= 0 {
+		// there is nothing in the driver to read from
+		return res
+	}
+
+	// Fetch and print each row of data until SQL_NO_DATA returned.
+	for {
+		mut row := []string{}
+		retcode = C.SQLFetch(h.hstmt)
+		if retcode == C.SQLRETURN(C.SQL_SUCCESS) || retcode == C.SQLRETURN(C.SQL_SUCCESS_WITH_INFO) {
+			// copy buffered result to res
+			for content in h.buffers {
+				row << string(content)
+			}
+		} else {
+			if retcode != C.SQLRETURN(C.SQL_NO_DATA) {
+				check_error(retcode, 'SQLFetch()', C.SQLHANDLE(h.hstmt), C.SQLSMALLINT(C.SQL_HANDLE_STMT)) ?
+			} else {
+				break
+			}
+		}
+		res << row
+	}
+	return res
+}