NAME
SQL::ObjectModel::API_C - Describe the core C API for SQL::ObjectModel
COPYRIGHT AND LICENSE
This file is part of the SQL::ObjectModel library (libSOM).
SQL::ObjectModel is Copyright (c) 1999-2003, Darren R. Duncan. All rights reserved. Address comments, suggestions, and bug reports to perl@DarrenDuncan.net, or visit "http://www.DarrenDuncan.net" for more information.
SQL::ObjectModel is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License (GPL) version 2 as published by the Free Software Foundation (http://www.fsf.org/). You should have received a copy of the GPL as part of the SQL::ObjectModel distribution, in the file named "LICENSE"; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
Any versions of SQL::ObjectModel that you modify and distribute must carry prominent notices stating that you changed the files and the date of any changes, in addition to preserving this original copyright notice and other credits. SQL::ObjectModel is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GPL for more details.
Linking SQL::ObjectModel statically or dynamically with other modules is making a combined work based on SQL::ObjectModel. Thus, the terms and conditions of the GPL cover the whole combination.
As a special exception, the copyright holders of SQL::ObjectModel give you permission to link SQL::ObjectModel with independent modules that are interfaces to or implementations of databases, regardless of the license terms of these independent modules, and to copy and distribute the resulting combined work under terms of your choice, provided that every copy of the combined work is accompanied by a complete copy of the source code of SQL::ObjectModel (the version of SQL::ObjectModel used to produce the combined work), being distributed under the terms of the GPL plus this exception. An independent module is a module which is not derived from or based on SQL::ObjectModel, and which is fully useable when not linked to SQL::ObjectModel in any form.
Note that people who make modified versions of SQL::ObjectModel are not obligated to grant this special exception for their modified versions; it is their choice whether to do so. The GPL gives permission to release a modified version without this exception; this exception also makes it possible to release a modified version which carries forward this exception.
While it is by no means required, the copyright holders of SQL::ObjectModel would appreciate being informed any time you create a modified version of SQL::ObjectModel that you are willing to distribute, because that is a practical way of suggesting improvements to the standard version.
DESCRIPTION
The first releases of SQL::ObjectModel are being implemented in pure Perl 5 thanks mainly to the heritage of original intention for using it with Perl programs, and otherwise to the fact that Perl is great for rapid prototyping, and has a large existing support for talking to databases, via the mature DBI framework, upon which to build. The longer term goal, however, is that SQL::ObjectModel will be a pure ANSI C library which has optional bindings for multiple other languages, such as C++, Objective-C, Perl 5 (most importantly), Parrot and Perl 6, Python, PHP 4+, Java, and whatever else users want.
This has practical benefits such as compatability with databases for which there is no existing Perl support (all database drivers already have C support), and the ability to use it with any favorite programming language (which can bring in developers from those communities aka Parrot). Moreover, and most easily guessed, C is a lot more efficient in both CPU and memory considering the huge amount of data processing that SQL::ObjectModel has to do. There are good reasons for things like LIBXML, GD, and DBI to be written in C which are applicable to SQL::ObjectModel also. To that end, SQL::ObjectModel is being designed from the ground up to be easily implemented in either Perl 5 or C, in both cases using an object-oriented conceptual process.
This document is a reference for the SQL::ObjectModel C API that is being planned, consisting mainly of the C header files (struct definitions and function declarations) that the actual SQL::ObjectModel core will end up being. After all, SQL::ObjectModel is actually more of an interface or protocol definition than an actual implementation (although it includes those parts too). This is intended to give programmers an idea why the design is going the way that it is and why details that pure Perl programs don't necessarily have to know about are being considered. While pure C is not object oriented at all, the SQL::ObjectModel API is designed to be as object-like as possible, such that each C struct for storing data will have a corresponding set of functions for interfacing with it, and the details for memory allocation and deallocation are handled by those also.
Note that the core libraries are intended to not have any external dependencies, except for data type handling libraries such as for string or sparse list handling. These classes do not do any I/O and they do not talk to the operating system, so they should be fully portable. All such things are relegated to extensions like the drivers.
Note also that the following should be considered almost-C rather than perfect C. The reasoning is that my experience in writing C is rusty at the moment and I haven't necessarily tried to compile these yet. For the moment they are just a type of documentation. They will be improved.
CONTENT OF libSOM.h
#ifndef _libSOM_h
#define _libSOM_h
#include "libSOM_types.h"
#include "libSOM_datatype.h"
#endif /* _libSOM_h */CONTENT OF libSOM_types.h
#ifndef _libSOM_types_h
#define _libSOM_types_h
#ifdef __cplusplus
extern "C" {
#endif
/************************************************************************/
/* define some constant values here */
#define FALSE 0
#define TRUE 1
/************************************************************************/
/* define some simple data types here */
typedef unsigned char dt_lsom_boolean; /* stores only two values: 0 (false) or 1 (true) */
typedef unsigned char dt_lsom_uint8 ; /* a precise integer between 0 and +255 */
typedef unsigned short dt_lsom_uint16; /* a precise integer between 0 and +65,535 */
typedef unsigned int dt_lsom_uint32; /* a precise integer between 0 and +4,294,967,295 */
typedef unsigned longlong dt_lsom_uint64; /* a precise integer between 0 and +(2^64)-1 */
typedef char dt_lsom_sint8 ; /* a precise integer between -128 and +127 */
typedef short dt_lsom_sint16; /* a precise integer between -32,768 and +32,767 */
typedef int dt_lsom_sint32; /* a precise integer between -2,147,483,648 and +2,147,483,647 */
typedef longlong dt_lsom_sint64; /* a precise integer between -(2^63) and +(2^63)-1 */
typedef float dt_lsom_float32; /* a 32-bit imprecise fractional number */
typedef double dt_lsom_float64; /* a 64-bit imprecise fractional number */
/* a precise fractional number stored as a variable length string */
typedef struct {
char* data ;
dt_lsom_uint16 byte_length;
} dt_lsom_decimal;
/* an arbitrary sized unit of binary data */
typedef struct {
char* data ;
dt_lsom_uint64 byte_length;
} dt_lsom_binary;
/* enumeration of character encoding types */
typedef enum {
LSOM_STR_ENC_U8 , /* 8-bit unicode */
LSOM_STR_ENC_U16, /* 16-bit unicode */
LSOM_STR_ENC_U32, /* 32-bit unicode */
LSOM_STR_ENC_ASC, /* 8-bit ascii */
LSOM_STR_ENC_EBS /* 8-bit ebsdic */
} en_lsom_str_enc_type;
/* an arbitrary sized unit of text data that is not null terminated */
typedef struct {
char* data ; /* actual string data, which may contain nulls */
dt_lsom_uint64 byte_length ; /* size of memory used by data in bytes */
en_lsom_str_enc_type enc_type ; /* string encoding type that data is using */
dt_lsom_uint8 bytes_per_char; /* (see enc_type) how many bytes each char uses, default = 1 */
} dt_lsom_string;
/* a date and time (whose representation isn't decided yet) */
typedef struct {
char* data ;
dt_lsom_uint8 byte_length;
} dt_lsom_datetime;
/************************************************************************/
/* define some accessor functions here */
/************************************************************************/
#ifdef __cplusplus
}
#endif
#endif /* _libSOM_types_h */CONTENT OF libSOM_datatype.h
#ifndef _libSOM_datatype_h
#define _libSOM_datatype_h
#ifdef __cplusplus
extern "C" {
#endif
#include "libSOM_types.h"
/************************************************************************/
/* define some simple data types here */
/* enumeration of basic data types */
typedef enum {
BOOL, /* a boolean */
BIN, /* binary data */
STR, /* text data */
INT, /* precise whole number */
FLOAT, /* imprecise fractional number */
DEC, /* precise fractional number */
DATETIME /* a date and time; this may be split into more types */
/* may add geographical types */
/* may add enumerated or set types */
} en_lsom_sch_datatype_base;
/* enumeration of ways to handle latin character data */
typedef enum {
PRESERVE, /* preserve existing case, upper and lower */
TOUPPER, /* convert to upper case */
TOLOWER /* convert to lower case */
} en_lsom_sch_datatype_case;
/* meta-data for a scalar unit of data, such as a db table column */
typedef struct {
dt_lsom_string name ; /* unique user-readable data type */
en_lsom_sch_datatype_base base_type ; /* basic underlying data type */
dt_lsom_uint64 size ; /* in bytes for BIN, INT, FLOAT; in chars for STR, DEC */
dt_lsom_boolean store_fixed ; /* true = try to store fixed size; default is var size */
en_lsom_str_enc_type str_encoding ; /* string encoding type for STR data */
dt_lsom_boolean str_trim_white; /* true = trim bounding whitespace on save */
en_lsom_sch_datatype_case str_latin_case; /* says how to handle latin text case on save */
dt_lsom_string str_pad_char ; /* if def, use char to pad fixed-width strs on save */
dt_lsom_boolean str_trim_pad ; /* true = trim padding of fixed-width strs on read */
dt_lsom_boolean int_unsigned ; /* true = only INTs >= 0 can be stored */
dt_lsom_uint16 dec_precision ; /* allowed max prec for DEC nums; must be < size */
/* others may be added such as min/max allowed num or date values or which calendar to use */
} st_lsom_sch_datatype;
/************************************************************************/
/* define some accessor functions here */
/************************************************************************/
#ifdef __cplusplus
}
#endif
#endif /* _libSOM_datatype_h */SEE ALSO
perl(1), SQL::ObjectModel, SQL::ObjectModel::DataDictionary, Rosetta, Rosetta::Framework.