-! (c)Joe Groff bsd license
-USING: alien classes help.markup help.syntax kernel libc
-quotations slots ;
+! Copyright (C) Joe Groff.
+! See http://factorcode.org/license.txt for BSD license.
+USING: alien classes classes.struct.private help.markup help.syntax
+kernel libc math sequences ;
IN: classes.struct
HELP: <struct-boa>
}
{ $description "This macro implements " { $link boa } " for " { $link struct } " classes. A struct of the given class is constructed, and its slots are initialized using values off the top of the datastack." } ;
+HELP: (struct)
+{ $values
+ { "class" class }
+ { "struct" struct }
+}
+{ $description "Allocates garbage-collected heap memory for a new " { $link struct } " of the specified " { $snippet "class" } ". The new struct's slots are left uninitialized; in most cases, the " { $link <struct> } " word, which initializes the struct's slots with their initial values, should be used instead." } ;
+
+{ (struct) (malloc-struct) } related-words
+
HELP: <struct>
{ $values
{ "class" class }
{ $description "Defines a new " { $link struct } " type. The syntax is nearly identical to " { $link POSTPONE: TUPLE: } "; however, there are some additional restrictions on struct types:"
{ $list
{ "Struct classes cannot have a superclass defined." }
-{ "The slots of a struct must all have a type declared. The type must be a C type." }
+{ "The slots of a struct must all have a type declared. The type must be a C type." }
{ { $link read-only } " slots on structs are not enforced, though they may be declared." }
-} } ;
+}
+"Additionally, structs may use bit fields. A slot specifier may use the syntax " { $snippet "bits: n" } " to specify that the bit width of the slot is " { $snippet "n" } ". Bit width may be specified on signed or unsigned integer slots. The layout of bit fields is not guaranteed to match that of any particular C compiler." } ;
HELP: S{
{ $syntax "S{ class slots... }" }
{ $values { "class" "a " { $link struct } " class word" } { "slots" "slot values" } }
{ $description "Marks the beginning of a literal struct. The syntax is identical to tuple literal syntax with " { $link POSTPONE: T{ } { $snippet " }" } "; either the assoc syntax (that is, " { $snippet "S{ class { slot value } { slot value } ... }" } ") or the simple syntax (" { $snippet "S{ class f value value ... }" } ") can be used." } ;
+HELP: S@
+{ $syntax "S@ class alien" }
+{ $values { "class" "a " { $link struct } " class word" } { "alien" "a literal alien" } }
+{ $description "Marks the beginning of a literal struct at a specific C address. The prettyprinter uses this syntax when the memory backing a struct object is invalid. This syntax should not generally be used in source code." } ;
+
+{ POSTPONE: S{ POSTPONE: S@ } related-words
+
HELP: UNION-STRUCT:
{ $syntax "UNION-STRUCT: class { slot type } { slot type } ... ;" }
{ $values { "class" "a new " { $link struct } " class to define" } { "slots" "a list of slot specifiers" } }
{ $description "Defines a new " { $link struct } " type where all of the slots share the same storage. See " { $link POSTPONE: STRUCT: } " for details on the syntax." } ;
+HELP: PACKED-STRUCT:
+{ $syntax "PACKED-STRUCT: class { slot type } { slot type } ... ;" }
+{ $values { "class" "a new " { $link struct } " class to define" } { "slots" "a list of slot specifiers" } }
+{ $description "Defines a new " { $link struct } " type with no alignment padding between slots or at the end. In all other respects, behaves like " { $link POSTPONE: STRUCT: } "." } ;
+
HELP: define-struct-class
{ $values
- { "class" class } { "slots" "a sequence of " { $link slot-spec } "s" }
+ { "class" class } { "slots" "a sequence of " { $link struct-slot-spec } "s" }
}
{ $description "Defines a new " { $link struct } " class. This is the runtime equivalent of the " { $link POSTPONE: STRUCT: } " syntax." } ;
+HELP: define-packed-struct-class
+{ $values
+ { "class" class } { "slots" "a sequence of " { $link struct-slot-spec } "s" }
+}
+{ $description "Defines a new " { $link struct } " class. This is the runtime equivalent of the " { $link POSTPONE: PACKED-STRUCT: } " syntax." } ;
+
HELP: define-union-struct-class
{ $values
- { "class" class } { "slots" "a sequence of " { $link slot-spec } "s" }
+ { "class" class } { "slots" "a sequence of " { $link struct-slot-spec } "s" }
}
{ $description "Defines a new " { $link struct } " class where all of the slots share the same storage. This is the runtime equivalent of the " { $link POSTPONE: UNION-STRUCT: } " syntax." } ;
{ "class" class }
{ "struct" struct }
}
-{ $description "Allocates unmanaged C heap memory for a new " { $link struct } " of the specified " { $snippet "class" } ". The new struct's slots are left uninitialized. The struct should be " { $link free } "d when it is no longer needed." } ;
+{ $description "Allocates unmanaged C heap memory for a new " { $link struct } " of the specified " { $snippet "class" } ". The new struct's slots are initialized to their initial values. The struct should be " { $link free } "d when it is no longer needed." } ;
+
+HELP: (malloc-struct)
+{ $values
+ { "class" class }
+ { "struct" struct }
+}
+{ $description "Allocates unmanaged C heap memory for a new " { $link struct } " of the specified " { $snippet "class" } ". The new struct's slots are left uninitialized; to initialize the allocated memory with the slots' initial values, use " { $link malloc-struct } ". The struct should be " { $link free } "d when it is no longer needed." } ;
+
+HELP: compute-struct-offsets
+{ $values { "slots" sequence } { "size" integer } }
+{ $description "Computes how many bytes of memory the struct takes, minus final padding." } ;
HELP: memory>struct
{ $values
}
{ $description "Constructs a new " { $link struct } " of the specified " { $snippet "class" } " at the memory location referenced by " { $snippet "ptr" } ". The referenced memory is unchanged." } ;
+HELP: read-struct
+{ $values { "class" class } { "struct" struct } }
+{ $description "Reads a new " { $link struct } " of the specified " { $snippet "class" } "." } ;
+
HELP: struct
{ $class-description "The parent class of all struct types." } ;
HELP: struct-class
{ $class-description "The metaclass of all " { $link struct } " classes." } ;
-ARTICLE: "classes.struct" "Struct classes"
-{ $link struct } " classes are similar to " { $link tuple } "s, but their slots exhibit value semantics, and they are backed by a contiguous structured block of memory. Structs can be used for structured access to C memory or Factor byte arrays and for passing struct values in and out of the FFI. Struct types are defined using a syntax similar to tuple syntax:"
-{ $subsection POSTPONE: STRUCT: }
+HELP: struct-slot-values
+{ $values { "struct" struct } { "sequence" sequence } }
+{ $description "Extracts the values of the structs slots" }
+{ $errors "Throws a memory protection error if the memory the struct references is not accessible." } ;
+
+ARTICLE: "classes.struct.examples" "Struct class examples"
+"A struct with a variety of fields:"
+{ $code
+ "USING: alien.c-types classes.struct ;"
+ ""
+ "STRUCT: test-struct"
+ " { i int }"
+ " { chicken char[16] }"
+ " { data void* } ;"
+}
+"Creating a new instance of this struct, and printing out:"
+{ $code "test-struct <struct> ." }
+"Creating a new instance with slots initialized from the stack:"
+{ $code
+ "USING: libc specialized-arrays alien.data ;"
+ "SPECIALIZED-ARRAY: char"
+ ""
+ "42"
+ "\"Hello, chicken.\" char >c-array"
+ "1024 malloc"
+ "test-struct <struct-boa> ."
+} ;
+
+ARTICLE: "classes.struct.define" "Defining struct classes"
+"Struct classes are defined using a syntax similar to the " { $link POSTPONE: TUPLE: } " syntax for defining tuple classes:"
+{ $subsections POSTPONE: STRUCT: POSTPONE: PACKED-STRUCT: }
+"Union structs are also supported, which behave like structs but share the same memory for all the slots."
+{ $subsections POSTPONE: UNION-STRUCT: } ;
+
+ARTICLE: "classes.struct.create" "Creating instances of structs"
"Structs can be allocated with " { $link new } "- and " { $link boa } "-like constructor words. Additional words are provided for building structs from C memory and from existing buffers:"
-{ $subsection <struct> }
-{ $subsection <struct-boa> }
-{ $subsection malloc-struct }
-{ $subsection memory>struct }
-"Structs have literal syntax like tuples:"
-{ $subsection POSTPONE: S{ }
-"Union structs are also supported, which behave like structs but share the same memory for all the type's slots."
-{ $subsection POSTPONE: UNION-STRUCT: }
-;
+{ $subsections
+ <struct>
+ <struct-boa>
+ malloc-struct
+ memory>struct
+}
+"When the contents of a struct will be immediately reset, faster primitive words are available that will create a struct without initializing its contents:"
+{ $subsections
+ (struct)
+ (malloc-struct)
+}
+"Structs have literal syntax, similar to " { $link POSTPONE: T{ } " for tuples:"
+{ $subsections POSTPONE: S{ } ;
+
+ARTICLE: "classes.struct.c" "Passing structs to C functions"
+"Structs can be passed and returned by value, or by reference."
+$nl
+"If a parameter is declared with a struct type, the parameter is passed by value. To pass a struct by reference, declare a parameter with a pointer to struct type."
+$nl
+{ $heading "C functions returning structs" }
+"If a C function is declared as returning a struct type, the struct is returned by value, and wrapped in an instance of the correct struct class automatically. If a C function is declared as returning a pointer to a struct, it will return an " { $link alien } " instance. This is because there is no way to distinguish between a pointer to a single struct and a pointer to an array of zero or more structs. It is up to the caller to wrap it in a struct using " { $link memory>struct } ", or a specialized array of structs using " { $snippet "<direct-T-array>" } ", respectively."
+$nl
+"An example of a struct declaration:"
+{ $code
+ "USING: alien.c-types classes.struct ;"
+ ""
+ "STRUCT: Point"
+ " { x int }"
+ " { y int }"
+ " { z int } ;"
+}
+"A C function which returns a struct by value:"
+{ $code
+ "USING: alien.syntax ;"
+ "FUNCTION: Point give_me_a_point ( c-string description )"
+}
+"A C function which takes a struct parameter by reference:"
+{ $code
+ "FUNCTION: void print_point ( Point* p )"
+} ;
+
+ARTICLE: "classes.struct" "Struct classes"
+"The " { $vocab-link "classes.struct" } " vocabulary implements " { $link struct } " classes. They are similar to " { $link tuple } " classes, but their slots exhibit value semantics, and they are backed by a contiguous structured block of memory. Structs can be used for space-efficient storage of data in the Factor heap, as well as for passing data to and from C libraries using the " { $link "alien" } "."
+{ $subsections
+ "classes.struct.examples"
+ "classes.struct.define"
+ "classes.struct.create"
+ "classes.struct.c"
+} ;
ABOUT: "classes.struct"
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