diff options
author | Pablo Martín <caedesv@users.sourceforge.net> | 2003-09-07 20:01:24 +0000 |
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committer | Pablo Martín <caedesv@users.sourceforge.net> | 2003-09-07 20:01:24 +0000 |
commit | e20d5ae3622d5d656dc28d7a090aee76b08158b0 (patch) | |
tree | de772d913888f4d5faf127414e2cb4ce486be3ca /include/pdp_type.h_old | |
parent | 69fab985ebfc5ea03228c92a859e4091fee1b28d (diff) |
updating pdp to current version 0.12.2
svn path=/trunk/externals/pdp/; revision=936
Diffstat (limited to 'include/pdp_type.h_old')
-rw-r--r-- | include/pdp_type.h_old | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/include/pdp_type.h_old b/include/pdp_type.h_old new file mode 100644 index 0000000..d588e7f --- /dev/null +++ b/include/pdp_type.h_old @@ -0,0 +1,180 @@ +/* + * Pure Data Packet system implementation. Type handling interface + * Copyright (c) by Tom Schouten <pdp@zzz.kotnet.org> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program 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 + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + * + */ + + +/* COMMENTS + +Since version 0.11 all packets have an (optional) high level type description. +This can be thought of as their mime type. It has several uses: + +* automatic type conversion +* better reuse strategy for non pure packets +* debugging + +The description is text-encoded, in the following form: + +type/subtype/subsubtype/.. + +This is implemented using t_pdp_symbol. + +Type descriptors can have wildcards. This is to give some freedom to a desired +type conversion. The following are all compatible: + +*/ + +// image/grey/320x240 +// image/*/320x240 +// image/*/* + +/* + +From a user pov, the type conversion is centralized. A single object (pdp_convert) +can do most of the conversions. + +Type conversion implementation has to be done decentralized. It is subdivided into +two steps: inter-type and intra-type conversions. + +Intra-type is the full responsability of each type implementation and can be handled +in a decentralized way (at linkage the type central intra-converter is registered +at the pdp framework. + +Inter-type conversion is harder to do decentralized, therefore each new type should +provide some conversions to the basic built in types. (internal image, bitmap or matrix +types. + +The point of this whole business is to + +* enable automatic conversion from anything to a desired type for operators that combine objects. + i.e. pdp_add but receive incompatible objects. +* enable manual anything to anything conversion using a pdp_convert object, i.e. have a consistent + package conversion api for users. + + +The solution is type conversion programs. A program's behaviour is specified as follows: + +* the program is registered with a source and destination (result) template +* it is passed a packet and a destination template +* it can assume the source packet complies to the program's registerd source template +* it should convert the packet to a packet that will comply to it's registered destination template +* if for some reason a conversion fails, an invalid packet (handle == -1) should be returned + +about type templates: + +* they are hierarchical, with subtypes separated by a '/' character +* they can contain a wildcard '*', meaning that a certain level in the type hierarchy is: + - a don't care value, when the wildcard is used + -> as a destination template in a requested conversion + -> as a source template in a conversion program's specification + - uspecified, when the wildcard is used + -> as a destination template in a conversion program's specification + + + +NOTE: + + a wildcard can't be used in a source template for a conversion request + this assymetry requires there be 2 kinds of template matching mechanisms: + + - source type description (without wildcards) to conversion program source template matching + - destination type description (with wildcards) to conversion program destination template matching + + since a packet's type description cannot have wildcards, a symmetric matching (both sides have + wildcards) can be used for matching. + +*/ + + + +/* + +implementation: + +there are 2 lists with conversion progams: +* the global list, containing all registered programs. +* the cached list, containing all recently used registered programs, or combinations thereof + +if there is no cached, perfectly matching rule, a new one will be created, and added to +the head of the conversion list. + +all conversion methods should keep their hand's off the source packet. it is treated as readonly. +this is to ensure a more flexible operation (i.e. be able to put the conversion at the register_ro +level) this will need a bit more logic in running the conversion program though.. + + +*/ + +#ifndef PDP_TYPE_H +#define PDP_TYPE_H + +/* the conversion method accepts a packet (which is freed) and a destination wildcard + and produces a new packet, or the invalid packet if the conversion failed */ +typedef int (*t_pdp_conversion_method)(int, t_pdp_symbol *); + +/* a conversion program is alist of conversion methods */ +typedef struct _pdp_conversion_program +{ + t_pdp_conversion_method method; // conversion method + struct _pdp_conversion_program *next; // next method in program +} t_pdp_conversion_program; + +/* a conversion has source and dest wildcards, and a conversion program */ +typedef struct _pdp_conversion +{ + t_pdp_symbol *src_pattern; // source type pattern + t_pdp_symbol *dst_pattern; // destination type pattern + t_pdp_conversion_program *program; // the conversion program for this conversion + struct _pdp_conversion *next; // next conversion program record +} t_pdp_conversion; + +/* all symbols are C style */ +#ifdef __cplusplus +extern "C" +{ +#endif + +/* pdp_packet methods */ +t_pdp_symbol *pdp_packet_get_description(int packet); +int pdp_packet_convert_ro(int packet, t_pdp_symbol *dest_pattern); +int pdp_packet_convert_rw(int packet, t_pdp_symbol *dest_pattern); + + +/* pdp_conversion_program methods */ +void pdp_conversion_program_free(t_pdp_conversion_program *program); +t_pdp_conversion_program *pdp_conversion_program_new(t_pdp_conversion_method method, ...); +t_pdp_conversion_program *pdp_conversion_program_copy(t_pdp_conversion_program *program); +void pdp_conversion_program_add(t_pdp_conversion_program *program, t_pdp_conversion_program *tail); + +/* pdp_type (central type object) methods */ +int pdp_type_description_match(t_pdp_symbol *description, t_pdp_symbol *pattern); +void pdp_type_register_conversion (t_pdp_symbol *src_pattern, t_pdp_symbol *dst_pattern, t_pdp_conversion_program *program); +void pdp_type_register_cached_conversion (t_pdp_symbol *src_pattern, t_pdp_symbol *dst_pattern, t_pdp_conversion_program *program); + + //t_pdp_symbol *pdp_type_gendesc(char *desc); //generate a type description (with description list attached) +t_pdp_list *pdp_type_to_list(t_pdp_symbol *type); + +/* pdp's (threadsafe) symbol */ +t_pdp_symbol *pdp_gensym(char *s); + + +#ifdef __cplusplus +} +#endif + +#endif |