33 lines
1.7 KiB
Factor
33 lines
1.7 KiB
Factor
USING: alien.c-types strings help.markup help.syntax alien.syntax
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sequences io arrays kernel words assocs namespaces ;
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IN: alien.structs
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ARTICLE: "c-structs" "C structure types"
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"A " { $snippet "struct" } " in C is essentially a block of memory with the value of each structure field stored at a fixed offset from the start of the block. The C library interface provides some utilities to define words which read and write structure fields given a base address."
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{ $subsection POSTPONE: C-STRUCT: }
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"Great care must be taken when working with C structures since no type or bounds checking is possible."
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$nl
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"An example:"
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{ $code
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"C-STRUCT: XVisualInfo"
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" { \"Visual*\" \"visual\" }"
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" { \"VisualID\" \"visualid\" }"
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" { \"int\" \"screen\" }"
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" { \"uint\" \"depth\" }"
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" { \"int\" \"class\" }"
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" { \"ulong\" \"red_mask\" }"
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" { \"ulong\" \"green_mask\" }"
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" { \"ulong\" \"blue_mask\" }"
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" { \"int\" \"colormap_size\" }"
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" { \"int\" \"bits_per_rgb\" } ;"
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}
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"C structure objects can be allocated by calling " { $link <c-object> } " or " { $link malloc-object } "."
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$nl
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"Arrays of C structures can be created with the " { $vocab-link "struct-arrays" } " vocabulary." ;
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ARTICLE: "c-unions" "C unions"
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"A " { $snippet "union" } " in C defines a type large enough to hold its largest member. This is usually used to allocate a block of memory which can hold one of several types of values."
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{ $subsection POSTPONE: C-UNION: }
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"C union objects can be allocated by calling " { $link <c-object> } " or " { $link malloc-object } "."
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$nl
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"Arrays of C unions can be created with the " { $vocab-link "struct-arrays" } " vocabulary." ; |