-USING: help.markup help.syntax byte-arrays ;
+USING: help.markup help.syntax byte-arrays alien math sequences ;
IN: specialized-arrays
-ARTICLE: "specialized-arrays" "Specialized arrays"
-"The " { $vocab-link "specialized-arrays" } " vocabulary implements fixed-length sequence types for storing machine values in a space-efficient manner without boxing."
-$nl
-"For each primitive C type " { $snippet "T" } ", a set of words are defined in the vocabulary named " { $snippet "specialized-arrays.T" } ":"
+HELP: SPECIALIZED-ARRAY:
+{ $syntax "SPECIALIZED-ARRAY: type" }
+{ $values { "type" "a C type" } }
+{ $description "Brings a specialized array for holding values of " { $snippet "type" } " into the vocabulary search path. The generated words are documented in " { $link "specialized-array-words" } "." } ;
+
+HELP: SPECIALIZED-ARRAYS:
+{ $syntax "SPECIALIZED-ARRAYS: type type type ... ;" }
+{ $values { "type" "a C type" } }
+{ $description "Brings a set of specialized arrays for holding values of each " { $snippet "type" } " into the vocabulary search path. The generated words are documented in " { $link "specialized-array-words" } "." } ;
+
+{ POSTPONE: SPECIALIZED-ARRAY: POSTPONE: SPECIALIZED-ARRAYS: } related-words
+
+HELP: direct-slice
+{ $values { "from" integer } { "to" integer } { "seq" "a specialized array" } { "seq'" "a new specialized array" } }
+{ $description "Constructs a new specialized array of the same type as " { $snippet "seq" } " sharing the same underlying memory as the subsequence of " { $snippet "seq" } " from elements " { $snippet "from" } " up to but not including " { $snippet "to" } ". Like " { $link slice } ", raises an error if " { $snippet "from" } " or " { $snippet "to" } " is out of bounds." } ;
+
+HELP: direct-head
+{ $values { "seq" "a specialized array" } { "n" integer } { "seq'" "a new specialized array" } }
+{ $description "Constructs a new specialized array of the same type as " { $snippet "seq" } " sharing the same underlying memory as the first " { $snippet "n" } " elements of " { $snippet "seq" } ". Like " { $link head } ", raises an error if " { $snippet "n" } " is out of bounds." } ;
+
+HELP: direct-tail
+{ $values { "seq" "a specialized array" } { "n" integer } { "seq'" "a new specialized array" } }
+{ $description "Constructs a new specialized array of the same type as " { $snippet "seq" } " sharing the same underlying memory as " { $snippet "seq" } " without the first " { $snippet "n" } " elements. Like " { $link tail } ", raises an error if " { $snippet "n" } " is out of bounds." } ;
+
+HELP: direct-head*
+{ $values { "seq" "a specialized array" } { "n" integer } { "seq'" "a new specialized array" } }
+{ $description "Constructs a new specialized array of the same type as " { $snippet "seq" } " sharing the same underlying memory as " { $snippet "seq" } " without the last " { $snippet "n" } " elements. Like " { $link head* } ", raises an error if " { $snippet "n" } " is out of bounds." } ;
+
+HELP: direct-tail*
+{ $values { "seq" "a specialized array" } { "n" integer } { "seq'" "a new specialized array" } }
+{ $description "Constructs a new specialized array of the same type as " { $snippet "seq" } " sharing the same underlying memory as the last " { $snippet "n" } " elements of " { $snippet "seq" } ". Like " { $link tail* } ", raises an error if " { $snippet "n" } " is out of bounds." } ;
+
+{ direct-slice direct-head direct-tail direct-head* direct-tail* } related-words
+
+ARTICLE: "specialized-array-words" "Specialized array words"
+"The " { $link POSTPONE: SPECIALIZED-ARRAY: } " and " { $link POSTPONE: SPECIALIZED-ARRAYS: } " parsing words generate specialized array types if they haven't been generated already and add the following words to the vocabulary search path, where " { $snippet "T" } " is the C type in question:"
{ $table
{ { $snippet "T-array" } { "The class of arrays with elements of type " { $snippet "T" } } }
{ { $snippet "<T-array>" } { "Constructor for arrays with elements of type " { $snippet "T" } "; stack effect " { $snippet "( len -- array )" } } }
- { { $snippet ">T-array" } { "Converts a sequence into a specialized array of type " { $snippet "T" } "; stack effect " { $snippet "( seq -- array )" } } }
- { { $snippet "byte-array>T-array" } { "Converts a byte array into a specialized array by interpreting the bytes in as machine-specific values. Code which uses this word is unportable" } }
+ { { $snippet "(T-array)" } { "Constructor for arrays with elements of type " { $snippet "T" } ", where the initial contents are uninitialized; stack effect " { $snippet "( len -- array )" } } }
+ { { $snippet "<direct-T-array>" } { "Constructor for arrays with elements of type " { $snippet "T" } " backed by raw memory; stack effect " { $snippet "( alien len -- array )" } } }
{ { $snippet "T-array{" } { "Literal syntax, consists of a series of values terminated by " { $snippet "}" } } }
}
-"Each specialized array has a " { $slot "underlying" } " slot holding a " { $link byte-array } " with the raw data. This data can be passed to C functions."
+"Behind the scenes, these words are placed in a vocabulary named " { $snippet "specialized-arrays.instances.T" } ", however this vocabulary should not be placed in a " { $link POSTPONE: USING: } " form directly. Instead, always use " { $link POSTPONE: SPECIALIZED-ARRAY: } " or " { $link POSTPONE: SPECIALIZED-ARRAYS: } ". This ensures that the vocabulary can get generated the first time it is needed."
$nl
-"The primitive C types for which specialized arrays exist:"
-{ $list
- { $snippet "char" }
- { $snippet "uchar" }
- { $snippet "short" }
- { $snippet "ushort" }
- { $snippet "int" }
- { $snippet "uint" }
- { $snippet "long" }
- { $snippet "ulong" }
- { $snippet "longlong" }
- { $snippet "ulonglong" }
- { $snippet "float" }
- { $snippet "double" }
- { $snippet "complex-float" }
- { $snippet "complex-double" }
- { $snippet "void*" }
- { $snippet "bool" }
+"Additionally, special versions of the standard " { $link <slice> } ", " { $link head } ", and " { $link tail } " sequence operations are provided for specialized arrays to create a new specialized array object sharing storage with a subsequence of an existing array:"
+{ $subsections
+ direct-slice
+ direct-head
+ direct-tail
+ direct-head*
+ direct-tail*
+} ;
+
+ARTICLE: "specialized-array-c" "Passing specialized arrays to C functions"
+"If a C function is declared as taking a parameter with a pointer or an array type (for example, " { $snippet "float*" } " or " { $snippet "int[3]" } "), instances of the relevant specialized array can be passed in."
+$nl
+"C type specifiers for array types are documented in " { $link "c-types-specs" } "."
+$nl
+"Here is an example; as is common with C functions, the array length is passed in separately, since C does not offer a runtime facility to determine the array length of a base pointer:"
+{ $code
+ "USING: alien.syntax specialized-arrays ;"
+ "SPECIALIZED-ARRAY: int"
+ "FUNCTION: void process_data ( int* data, int len )"
+ "int-array{ 10 20 30 } dup length process_data"
+}
+"Literal specialized arrays, as well as specialized arrays created with " { $snippet "<T-array>" } " and " { $snippet "T >c-array" } " are backed by a " { $link byte-array } " in the Factor heap, and can move as a result of garbage collection. If this is unsuitable, the array can be allocated in unmanaged memory instead."
+$nl
+"In the following example, it is presumed that the C library holds on to a pointer to the array's data after the " { $snippet "init_with_data()" } " call returns; this is one situation where unmanaged memory has to be used instead. Note the use of destructors to ensure the memory is deallocated after the block ends:"
+{ $code
+ "USING: alien.syntax specialized-arrays ;"
+ "SPECIALIZED-ARRAY: float"
+ "FUNCTION: void init_with_data ( float* data, int len )"
+ "FUNCTION: float compute_result ( )"
+ "["
+ " 100 malloc-float-array &free"
+ " dup length init_with_data"
+ " compute_result"
+ "] with-destructors"
+}
+"Finally, sometimes a C library returns a pointer to an array in unmanaged memory, together with a length. In this case, a specialized array can be constructed to view this memory using " { $snippet "<direct-T-array>" } ":"
+{ $code
+ "USING: alien.c-types alien.data classes.struct ;"
+ ""
+ "STRUCT: device_info"
+ " { id int }"
+ " { name char* } ;"
+ ""
+ "FUNCTION: void get_device_info ( int* length )"
+ ""
+ "0 int <ref> [ get_device_info ] keep <direct-int-array> ."
}
-"Note that " { $vocab-link "specialized-arrays.bool" } " behaves like a C " { $snippet "bool[]" } " array, and each element takes up 8 bits of space. For a more space-efficient boolean array, see " { $link "bit-arrays" } "."
+"For a full discussion of Factor heap allocation versus unmanaged memory allocation, see " { $link "byte-arrays-gc" } "."
$nl
-"Specialized arrays are generated with a functor in the " { $vocab-link "specialized-arrays.functor" } " vocabulary."
+"Each specialized array has a " { $slot "underlying" } " slot holding a " { $link byte-array } " with the raw data. Passing a specialized array as a parameter to a C function call will automatically extract the underlying data. To get at the underlying data directly, call the " { $link >c-ptr } " word on a specialized array." ;
+
+ARTICLE: "specialized-array-math" "Vector arithmetic with specialized arrays"
+"Each specialized array with a numeric type generates specialized versions of the " { $link "math-vectors" } " words. The compiler substitutes calls for these words if it can statically determine input types. The " { $snippet "optimized." } " word in the " { $vocab-link "compiler.tree.debugger" } " vocabulary can be used to determine if this optimization is being performed for a particular piece of code." ;
+
+ARTICLE: "specialized-array-examples" "Specialized array examples"
+"Let's import specialized float arrays:"
+{ $code "USING: specialized-arrays math.constants math.functions ;" "SPECIALIZED-ARRAY: float" }
+"Creating a float array with 3 elements:"
+{ $code "1.0 [ sin ] [ cos ] [ tan ] tri float-array{ } 3sequence ." }
+"Create a float array and sum the elements:"
+{ $code
+ "1000 <iota> [ 1000 /f pi * sin ] float-array{ } map-as"
+ "0.0 [ + ] reduce ."
+} ;
+
+ARTICLE: "specialized-arrays" "Specialized arrays"
+"The " { $vocab-link "specialized-arrays" } " vocabulary implements fixed-length sequence types for storing machine values in a space-efficient manner without boxing."
$nl
-"The " { $vocab-link "specialized-vectors" } " vocabulary provides resizable versions of the above." ;
+"A specialized array type needs to be generated for each element type. This is done with parsing words:"
+{ $subsections
+ POSTPONE: SPECIALIZED-ARRAY:
+ POSTPONE: SPECIALIZED-ARRAYS:
+}
+"This parsing word adds new words to the search path, documented in the next section."
+{ $subsections
+ "specialized-array-words"
+ "specialized-array-c"
+ "specialized-array-math"
+ "specialized-array-examples"
+}
+"The " { $vocab-link "specialized-vectors" } " vocabulary provides a resizable version of this abstraction." ;
ABOUT: "specialized-arrays"
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