1ExtUtils::Constant::BaseP(e3rplm)Programmers ReferenceEGxutiUdteils::Constant::Base(3pm)
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6 ExtUtils::Constant::Base - base class for ExtUtils::Constant objects
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9 require ExtUtils::Constant::Base;
10 @ISA = 'ExtUtils::Constant::Base';
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13 ExtUtils::Constant::Base provides a base implementation of methods to
14 generate C code to give fast constant value lookup by named string.
15 Currently it's mostly used ExtUtils::Constant::XS, which generates the
16 lookup code for the constant() subroutine found in many XS modules.
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19 ExtUtils::Constant::Base exports no subroutines. The following methods
20 are available
21 header
23 A method returning a scalar containing definitions needed,
24 typically for a C header file.
25 memEQ_clause args_hashref
27 A method to return a suitable C "if" statement to check whether
28 name is equal to the C variable "name". If checked_at is defined,
29 then it is used to avoid "memEQ" for short names, or to generate a
30 comment to highlight the position of the character in the "switch"
31 statement.
32 If i<checked_at> is a reference to a scalar, then instead it gives
34 the characters pre-checked at the beginning, (and the number of
35 chars by which the C variable name has been advanced. These need to
36 be chopped from the front of name).
37 dump_names arg_hashref, ITEM...
39 An internal function to generate the embedded perl code that will
40 regenerate the constant subroutines. default_type, types and ITEMs
41 are the same as for C_constant. indent is treated as number of
42 spaces to indent by. If "declare_types" is true a $types is always
43 declared in the perl code generated, if defined and false never
44 declared, and if undefined $types is only declared if the values in
45 types as passed in cannot be inferred from default_types and the
46 ITEMs.
47 assign arg_hashref, VALUE...
49 A method to return a suitable assignment clause. If type is
50 aggregate (eg PVN expects both pointer and length) then there
51 should be multiple VALUEs for the components. pre and post if
52 defined give snippets of C code to proceed and follow the
53 assignment. pre will be at the start of a block, so variables may
54 be defined in it.
55 return_clause arg_hashref, ITEM
57 A method to return a suitable "#ifdef" clause. ITEM is a hashref
58 (as passed to "C_constant" and "match_clause". indent is the number
59 of spaces to indent, defaulting to 6.
60 switch_clause arg_hashref, NAMELEN, ITEMHASH, ITEM...
62 An internal method to generate a suitable "switch" clause, called
63 by "C_constant" ITEMs are in the hash ref format as given in the
64 description of "C_constant", and must all have the names of the
65 same length, given by NAMELEN. ITEMHASH is a reference to a hash,
66 keyed by name, values being the hashrefs in the ITEM list. (No
67 parameters are modified, and there can be keys in the ITEMHASH that
68 are not in the list of ITEMs without causing problems - the hash is
69 passed in to save generating it afresh for each call).
70 params WHAT
72 An "internal" method, subject to change, currently called to allow
73 an overriding class to cache information that will then be passed
74 into all the "*param*" calls. (Yes, having to read the source to
75 make sense of this is considered a known bug). WHAT is be a hashref
76 of types the constant function will return. In
77 ExtUtils::Constant::XS this method is used to returns a hashref
78 keyed IV NV PV SV to show which combination of pointers will be
79 needed in the C argument list generated by
80 C_constant_other_params_definition and C_constant_other_params
81 dogfood arg_hashref, ITEM...
83 An internal function to generate the embedded perl code that will
84 regenerate the constant subroutines. Parameters are the same as
85 for C_constant.
86 Currently the base class does nothing and returns an empty string.
88 normalise_items args, default_type, seen_types, seen_items, ITEM...
90 Convert the items to a normalised form. For 8 bit and Unicode
91 values converts the item to an array of 1 or 2 items, both 8 bit
92 and UTF-8 encoded.
93 C_constant arg_hashref, ITEM...
95 A function that returns a list of C subroutine definitions that
96 return the value and type of constants when passed the name by the
97 XS wrapper. ITEM... gives a list of constant names. Each can
98 either be a string, which is taken as a C macro name, or a
99 reference to a hash with the following keys
100 name The name of the constant, as seen by the perl code.
102 type The type of the constant (IV, NV etc)
104 value A C expression for the value of the constant, or a list of
106 C expressions if the type is aggregate. This defaults to
107 the name if not given.
108 macro The C pre-processor macro to use in the "#ifdef". This
110 defaults to the name, and is mainly used if value is an
111 "enum". If a reference an array is passed then the first
112 element is used in place of the "#ifdef" line, and the
113 second element in place of the "#endif". This allows pre-
114 processor constructions such as
115 #if defined (foo)
117 #if !defined (bar)
118 ...
119 #endif
120 #endif
121 to be used to determine if a constant is to be defined.
123 A "macro" 1 signals that the constant is always defined, so
125 the "#if"/"#endif" test is omitted.
126 default Default value to use (instead of "croak"ing with "your
128 vendor has not defined...") to return if the macro isn't
129 defined. Specify a reference to an array with type followed
130 by value(s).
131 pre C code to use before the assignment of the value of the
133 constant. This allows you to use temporary variables to
134 extract a value from part of a "struct" and return this as
135 value. This C code is places at the start of a block, so
136 you can declare variables in it.
137 post C code to place between the assignment of value (to a
139 temporary) and the return from the function. This allows
140 you to clear up anything in pre. Rarely needed.
141 def_pre
143 def_post
144 Equivalents of pre and post for the default value.
145 utf8 Generated internally. Is zero or undefined if name is 7 bit
147 ASCII, "no" if the name is 8 bit (and so should only match
148 if SvUTF8() is false), "yes" if the name is utf8 encoded.
149 The internals automatically clone any name with characters
151 128-255 but none 256+ (ie one that could be either in bytes
152 or utf8) into a second entry which is utf8 encoded.
153 weight Optional sorting weight for names, to determine the order
155 of linear testing when multiple names fall in the same case
156 of a switch clause. Higher comes earlier, undefined
157 defaults to zero.
158 In the argument hashref, package is the name of the package, and is
160 only used in comments inside the generated C code. subname defaults
161 to "constant" if undefined.
162 default_type is the type returned by "ITEM"s that don't specify
164 their type. It defaults to the value of "default_type()". types
165 should be given either as a comma separated list of types that the
166 C subroutine subname will generate or as a reference to a hash.
167 default_type will be added to the list if not present, as will any
168 types given in the list of ITEMs. The resultant list should be the
169 same list of types that "XS_constant" is given. [Otherwise
170 "XS_constant" and "C_constant" may differ in the number of
171 parameters to the constant function. indent is currently unused and
172 ignored. In future it may be used to pass in information used to
173 change the C indentation style used.] The best way to maintain
174 consistency is to pass in a hash reference and let this function
175 update it.
176 breakout governs when child functions of subname are generated. If
178 there are breakout or more ITEMs with the same length of name, then
179 the code to switch between them is placed into a function named
180 subname_len, for example "constant_5" for names 5 characters long.
181 The default breakout is 3. A single "ITEM" is always inlined.
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184 Not everything is documented yet.
185 Probably others.
187
189 Nicholas Clark <nick@ccl4.org> based on the code in "h2xs" by Larry
190 Wall and others
191perl v5.36.3 2023-11-30 ExtUtils::Constant::Base(3pm)