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Article contents:== Outdated CHICKEN release This is a manual page for an old and unsupported version of CHICKEN. If you are still using it, please consider migrating to the latest version. You can find the manual for the latest release [[/manual|here]]. [[tags: manual]] == Foreign type specifiers Here is a list of valid foreign type specifiers: === scheme-object An arbitrary Scheme data object (immediate or non-immediate). === bool As argument: any value ({{#f}} is false, anything else is true). As result: anything different from 0 and the {{NULL}} pointer is {{#t}}. === byte unsigned-byte A byte. === char unsigned-char A character. === short unsigned-short A short integer number. === int unsigned-int int32 unsigned-int32 An small integer number in fixnum range (at least 30 bit). === integer unsigned-integer integer32 unsigned-integer32 integer64 Either a fixnum or a flonum in the range of a (unsigned) machine ''int'' or with 32/64 bit width. === long unsigned-long Either a fixnum or a flonum in the range of a (unsigned) machine ''long'' or with 32 bit width. === float double A floating-point number. If an exact integer is passed as an argument, then it is automatically converted to a float. === number A floating-point number. Similar to {{double}}, but when used as a result type, then either an exact integer or a floating-point number is returned, depending on whether the result fits into an exact integer or not. === symbol A symbol, which will be passed to foreign code as a zero-terminated string. When declared as the result of foreign code, the result should be a string and a symbol with the same name will be interned in the symbol table (and returned to the caller). === scheme-pointer An untyped pointer to the contents of a non-immediate Scheme object (not allowed as return type). The value {{#f}} is also allowed and is passed as a {{NULL}} pointer. Don't confuse this type with {{(c-pointer ...)}} which means something different (a machine-pointer object). === nonnull-scheme-pointer As {{scheme-pointer}}, but guaranteed not to be {{#f}}. Don't confuse this type with {{(nonnull-c-pointer ...)}} which means something different (a machine-pointer object). === c-pointer An untyped operating-system pointer or a locative. The value {{#f}} is also allowed and is passed as a {{NULL}} pointer. If uses as the type of a return value, a {{NULL}} pointer will be returned as {{#f}}. === nonnull-c-pointer As {{c-pointer}}, but guaranteed not to be {{#f/NULL}}. === blob A blob object, passed as a pointer to its contents. Arguments of type {{blob}} may optionally be {{#f}}, which is passed as a NULL pointer. This is not allowed as a return type. === nonnull-blob As {{blob}}, but guaranteed not to be {{#f}}. === u8vector u16vector u32vector s8vector s16vector s32vector f32vector f64vector A SRFI-4 number-vector object, passed as a pointer to its contents. These type specifiers are not allowed as return types. === nonnull-u8vector nonnull-u16vector nonnull-u32vector nonnull-s8vector nonnull-s16vector nonnull-s32vector nonnull-f32vector nonnull-f64vector As {{u8vector ...}}, but guaranteed not to be {{#f}}. === c-string A C string (zero-terminated). The value {{#f}} is also allowed and is passed as a {{NULL}} pointer. If uses as the type of a return value, a {{NULL}} pointer will be returned as {{#f}}. Note that the string is copied (with a zero-byte appended) when passed as an argument to a foreign function. Also a return value of this type is copied into garbage collected memory. === nonnull-c-string As {{c-string}}, but guaranteed not to be {{#f/NULL}}. === [nonnull-] c-string* Similar to {{[nonnull-] c-string}}, but if used as a result-type, the pointer returned by the foreign code will be freed (using the C-libraries {{free(1)}}) after copying. This type specifier is not valid as a result type for callbacks defined with {{define-external}}. === [nonnull-] unsigned-c-string[*] Same as {{c-string}}, but maps to the {{unsigned char *}} C type. === c-string-list Expects a pointer to a list of C strings teminated by a {{NULL}} pointer and returns a list of strings. Only valid as a result type of non-callback functions. === c-string-list* Similar to {{c-string-list}} but releases the storage of each string and the pointer array using {{free(1)}}. === void Specifies an undefined return value. Not allowed as argument type. === (const TYPE) The foreign type {{TYPE}} with an additional {{const}} specifier. === (enum NAME) An enumeration type. Handled internally as an {{integer}}. === (c-pointer TYPE) An operating-system pointer or a locative to an object of {{TYPE}}. === (nonnull-c-pointer TYPE) As {{(c-pointer TYPE)}}, but guaranteed not to be {{#f/NULL}}. === (ref TYPE) A C++ reference type. Reference types are handled the same way as pointers inside Scheme code. === (struct NAME) A struct of the name {{NAME}}, which should be a string. Structs cannot be directly passed as arguments to foreign function, neither can they be result values. Pointers to structs are allowed, though. === (template TYPE ARGTYPE ...) A C++ template type. For example {{vector<int>}} would be specified as {{(template "vector" int)}}. Template types cannot be directly passed as arguments or returned as results. === (union NAME) A union of the name {{NAME}}, which should be a string. Unions cannot be directly passed as arguments to foreign function, neither can they be result values. Pointers to unions are allowed, though. === (instance CNAME SCHEMECLASS) A pointer to a C++ class instance. {{CNAME}} should designate the name of the C++ class, and {{SCHEMECLASS}} should be the class that wraps the instance pointer. Normally {{SCHEMECLASS}} should be a subclass of {{<c++-object>}}. === (instance-ref CNAME SCHEMECLASS) A reference to a C++ class instance. === (function RESULTTYPE (ARGUMENTTYPE1 ... [...]) [CALLCONV]) A function pointer. {{CALLCONV}} specifies an optional calling convention and should be a string. The meaning of this string is entirely platform dependent. The value {{#f}} is also allowed and is passed as a {{NULL}} pointer. === Mappings Foreign types are mapped to C types in the following manner: <table> <tr><td>bool</td><td> int </td></tr><tr><td>[unsigned-]char</td><td> [unsigned] char </td></tr><tr><td>[unsigned-]short</td><td> [unsigned] short </td></tr><tr><td>[unsigned-]int</td><td> [unsigned] int </td></tr><tr><td>[unsigned-]integer</td><td> [unsigned] int </td></tr><tr><td>[unsigned-]long</td><td> [unsigned] long </td></tr><tr><td>float</td><td> float </td></tr><tr><td>double</td><td> double </td></tr><tr><td>number</td><td> double </td></tr><tr><td>[nonnull-]c-pointer</td><td> void * </td></tr><tr><td>[nonnull-]blob</td><td> unsigned char * </td></tr><tr><td>[nonnull-]u8vector</td><td> unsigned char * </td></tr><tr><td>[nonnull-]s8vector</td><td> char * </td></tr><tr><td>[nonnull-]u16vector</td><td> unsigned short * </td></tr><tr><td>[nonnull-]s16vector</td><td> short * </td></tr><tr><td>[nonnull-]u32vector</td><td> uint32_t * </td></tr><tr><td>[nonnull-]s32vector</td><td> int32_t * </td></tr><tr><td>[nonnull-]f32vector</td><td> float * </td></tr><tr><td>[nonnull-]f64vector</td><td> double * </td></tr><tr><td>[nonnull-]c-string</td><td> char * </td></tr><tr><td>[nonnull-]unsigned-c-string</td><td> unsigned char * </td></tr> <tr><td>c-string-list</td><td>char **</td></tr> <tr><td>symbol</td><td> char * </td></tr><tr><td>void</td><td> void </td></tr><tr><td>([nonnull-]c-pointer TYPE)</td><td> TYPE * </td></tr><tr><td>(enum NAME)</td><td> enum NAME </td></tr><tr><td>(struct NAME)</td><td> struct NAME </td></tr><tr><td>(ref TYPE)</td><td> TYPE & </td></tr><tr><td>(template T1 T2 ...)</td><td> T1<T2, ...> </td></tr><tr><td>(union NAME)</td><td> union NAME </td></tr><tr><td>(function RTYPE (ATYPE ...) [CALLCONV])</td><td> [CALLCONV] RTYPE (*)(ATYPE, ...) </td></tr><tr><td>(instance CNAME SNAME)</td><td> CNAME * </td></tr><tr><td>(instance-ref CNAME SNAME)</td><td> CNAME & </td></tr></table> Previous: [[Accessing external objects]] Next: [[Embedding]] Description of your changes:

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