/* * PROGRAM: Object oriented API samples. * MODULE: 04.print_table.cpp * DESCRIPTION: Run SELECT statement without parameters. * Use attachment method to open cursor. * Print all fields for selected records in a table. * Learns how to access blob data and use unprepared statement. * * Example for the following interfaces: * * IAttachment - database attachment * IMessageMetadata - describe input and output data format * IResultSet - fetch data returned by statement after execution * * The contents of this file are subject to the Initial * Developer's Public License Version 1.0 (the "License"); * you may not use this file except in compliance with the * License. You may obtain a copy of the License at * http://www.ibphoenix.com/main.nfs?a=ibphoenix&page=ibp_idpl. * * Software distributed under the License is distributed AS IS, * WITHOUT WARRANTY OF ANY KIND, either express or implied. * See the License for the specific language governing rights * and limitations under the License. * * The Original Code was created by Alexander Peshkoff * for the Firebird Open Source RDBMS project. * * Copyright (c) 2013 Alexander Peshkoff <peshkoff@mail.ru> * and all contributors signed below. * * All Rights Reserved. * Contributor(s): ______________________________________. */ #include "ifaceExamples.h" static IMaster* master = fb_get_master_interface(); struct MyField { const char* name; unsigned type, length, offset, null; void print(ThrowStatusWrapper* st, IAttachment* att, ITransaction* tra, unsigned char* buf); }; int main() { int rc = 0; char s[100]; setenv("ISC_USER", "sysdba", 0); setenv("ISC_PASSWORD", "masterkey", 0); ThrowStatusWrapper status(master->getStatus()); IProvider* prov = master->getDispatcher(); IAttachment* att = NULL; ITransaction* tra = NULL; IResultSet* curs = NULL; IMessageMetadata* meta = NULL; try { att = prov->attachDatabase(&status, "employee", 0, NULL); tra = att->startTransaction(&status, 0, NULL); // If we are not going to run same SELECT query many times we may do not prepare it, // opening cursor instead with single API call. // If statement has input parameters and we know them, appropriate IMetadata may be // constructed and passed to openCursor() together with data buffer. // We also may provide out format info and coerce data passing appropriate metadata // into API call. // In this sample we have no input parameters and do not coerce anything - just // print what we get from SQL query. const char* sql = "select * from rdb$relations where RDB$RELATION_ID < 3 " "or RDB$VIEW_SOURCE is not null"; // Do not use IStatement - just ask attachment to open cursor curs = att->openCursor(&status, tra, 0, sql, SAMPLES_DIALECT, NULL, NULL, NULL, NULL, 0); meta = curs->getMetadata(&status); unsigned cols = meta->getCount(&status); MyField* fields = new MyField[cols]; memset(fields, 0, sizeof(MyField) * cols); unsigned f = 0; for (unsigned j = 0; j < cols; ++j) { unsigned t = meta->getType(&status, j) & ~1; unsigned sub = meta->getSubType(&status, j); switch (t) { case SQL_BLOB: if (sub != 1) continue; break; case SQL_TEXT: case SQL_VARYING: case SQL_SHORT: case SQL_DOUBLE: break; default: { sprintf(s, "Unknown type %d for %s", t, meta->getField(&status, j)); throw s; } continue; } // we can work with this field - cache metadata info for fast access fields[f].type = t; fields[f].name = meta->getField(&status, j); fields[f].length = meta->getLength(&status, j); fields[f].offset = meta->getOffset(&status, j); fields[f].null = meta->getNullOffset(&status, j); ++f; } unsigned l = meta->getMessageLength(&status); unsigned char* buffer = new unsigned char[l]; // fetch records from cursor while (curs->fetchNext(&status, buffer) == IStatus::RESULT_OK) { for (unsigned j = 0; j < f; ++j) { // call field's function to print it fields[j].print(&status, att, tra, buffer); } printf("\n"); } curs->close(&status); curs = NULL; meta->release(); meta = NULL; tra->commit(&status); tra = NULL; att->detach(&status); att = NULL; } catch (const FbException& error) { // handle error fflush(stdout); rc = 1; char buf[256]; master->getUtilInterface()->formatStatus(buf, sizeof(buf), error.getStatus()); fprintf(stderr, "%s\n", buf); } if (meta) meta->release(); if (curs) curs->release(); if (tra) tra->release(); if (att) att->release(); prov->release(); status.dispose(); return rc; } template <typename T> T as(unsigned char* ptr) { return *((T*) ptr); } void MyField::print(ThrowStatusWrapper* st, IAttachment* att, ITransaction* tra, unsigned char* buf) { printf("%s: ", name); if (as<short>(buf + null)) { printf("<Null>\n"); return; } // IBlob makes it possible to read/write BLOB data IBlob* blob = NULL; switch (type) { // text fields case SQL_TEXT: printf("%*.*s\n", length, length, buf + offset); break; case SQL_VARYING: { unsigned l = as<short>(buf + offset); printf("%*.*s\n", l, l, buf + offset + sizeof(short)); } break; // numeric fields case SQL_SHORT: printf("%d\n", as<short>(buf + offset)); break; case SQL_DOUBLE: printf("%f\n", as<double>(buf + offset)); break; // blob requires more handling in DB case SQL_BLOB: try { // use attachment's method to access BLOB object blob = att->openBlob(st, tra, (ISC_QUAD*) (buf + offset), 0, NULL); char segbuf[16]; unsigned len; // read data segment by segment for (;;) { int cc = blob->getSegment(st, sizeof(segbuf), segbuf, &len); if (cc != IStatus::RESULT_OK && cc != IStatus::RESULT_SEGMENT) break; fwrite(segbuf, sizeof(char), len, stdout); } // close BLOB after receiving all data blob->close(st); blob = NULL; printf("\n"); } catch (...) { if (blob) blob->release(); throw; } break; // do not plan to have all types here default: throw "Unknown type in MyField::print()"; } }