DataBase_Use_C.zip_c语言 数据库_database_database_use_c_小型数据库_数据库系统

cbaseTM The C Database Library Citadel Brookville, IndianaCopyright (c) 1989, 1991 Citadel All rights reserved Citadel Software, Inc. 241 East Eleventh Street Brookville, IN 47012 317-647-4720 BBS 317-647-2403 Version 1.0.2 This manual is protected by United States copyright law. No part of it may be reproduced without the express written permission of Citadel. Technical Support The Citadel BBS is available 24 hours a day. Voice support is available between 10 a.m. and 4 p.m. EST. When calling for technical support, please have ready the following information: - product name and version number - operating system and version number - C compiler and version number - computer brand and model UNIX is a trademark of AT&T. Turbo C is a trademark of Borland International, Inc. Contents Introduction 1 Chapter 1. A Tutorial Introduction 3 1.1 Defining a Database 1.2 Using the cbase Library Chapter 2. cbase Architecture 9 Chapter 3. The Data Definition Language 11 Chapter 4. cbase Library Functions 13 4.1 Access Control Functions 4.2 Lock Functions 4.3 Record Cursor Position Functions 4.4 Key Cursor Position Functions 4.5 Input/Output Functions 4.6 Import/Export Functions Chapter 5. Custom Indexing 23 Chapter 6. An Example Program 27 6.1 Data Definition 6.2 Opening a cbase 6.3 Locking a cbase 6.4 Accessing a cbase 6.5 Closing a cbase 6.6 Storing Variable Length Text Appendix A. Installation Instructions 37 A1 manx A2 The blkio Library A3 The lseq Library A4 The btree Library A5 The cbase Library A6 Combining Libraries A7 cbddlp A8 rolodeck A9 Troubleshooting Appendix B. Defining New Data Types 45 B1 The Type Name B2 The Comparison Function B3 The Export and Import Functions B4 The Type Count Appendix C. Porting to a New Operating System 49 C1 The OPSYS and CCOM Macros C2 The File Descriptor Type C3 System Calls for File Access C4 System Calls for File Locking C5 Debugging References 53 Introduction cbase is a complete multiuser C database file management library, providing indexed and sequential access on multiple keys. Custom indexing beyond that performed automatically by cbase can also be performed. cbase features a layered architecture (see Figure 2.1), and actually includes four individual libraries. Below is a summary of the library's main features. cbase Features Portable - Written in strict adherence to ANSI C standard. - K&R C compatibility maintained. - All operating system dependent code is isolated, making it easy to port to new systems easy. - UNIX and DOS currently supported. - Complete C source code included. Buffered - Both records and indexes are buffered using LRU (least recently used) buffering. Fast and efficient random access - B+-trees are used for inverted file key storage. - Multiple keys are supported. - Both unique and duplicate keys are supported. Fast and efficient sequential access - B+-trees also allow keyed sequential access. - Records are stored in doubly linked lists for non-keyed sequential access. - Both types of sequential access are bidirectional. Multiuser - Read-only locking. Other Features - Text file data import and export. - Custom data types can be defined. - Marker used to detect corrupt files. - Reference documentation is in standard UNIX manual entry format, including errno values. Utilities - cbddlp, a data definition language processor, is provided to automatically generate the C code defining a database. Chapter 1: A Tutorial Introduction We begin with a brief example of a cbase application to provide the reader with a general understanding of the basic elements involved. Details on everything presented here will come in later chapters. The running example in this tutorial will be a minimal inventory database consisting of a single type of record having fields for a unique part code, a part description, bin location, and quantity in stock. 1.1 Defining a Database The first step in any database application is to design the logical structure of the database, i.e., the records to be stored and the fields in those records. This logical design must then be encoded somehow into the application, which involves the construction of data structures that can be quite lengthy and tedious to input. To facilitate this process, cbase allows databases to be defined using a relatively concise data definition language (DDL). The most important DDL element is the record statement. record is similar to the C struct statement, but database data types are used rather than C types, and fields can be made keys simply by prefixing the keyword key. Using the keyword unique in addition will cause the key to be constrained to be unique. What being a key means is that an index is automatically maintained for that field, allowing quick searches to be performed on that field as well as rapid sequential processing of the records in the sort order of that field. The DDL statements data file and index file are used to specify the filename for each data file and index file. C preprocessor statements can also be included in a DDL file. Figure 1.1 shows the complete DDL description part.ddl for our inventory database. This information must now be translated into a form accessible from a C program. This is done with the cbase DDL processor cbddlp. cbddlp part.ddl From the information in part.ddl, cbddlp generates all the necessary macros and data structures necessary to completely define the database in C. Two C source files are generated: a .h file to be included in every module, and a .i file to be included in only one, normally the one containing main. The contents of the .i file will be used only internally by cbase, but the contents of the .h file are required by the application program. Figure 1.2 lists the header file part.h generated from part.ddl. First notice that the C preprocessor statements have been passed through unaltered. There is then a macro identifying the cbase that is the record name converted to upper case. For each record statement in the DDL file, there is a corresponding C struct statement using the same record name as its identifier. For each field in a record there is an upper case macro identifying it, and a macro for the number of fields in the record. Finally, there is a declaration for the field list data structure in the .i file that is passed to the cbase library functions to create and open a cbase. The prefix for the field count and field list identifiers are taken from the characters of the first field name preceding the first underscore. /* constants */ #define PTCODE_MAX (11) /* part code length max */ #define PTDESC_MAX (30) /* part description length max */ #define PTBIN_MAX (4) /* part bin length max */ /* file assignments */ data file "part.dat" contains part; index file "ptcode.ndx" contains pt_code;