diff options
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 34 |
1 files changed, 32 insertions, 2 deletions
@@ -74513,7 +74513,10 @@ type is similar to the unparametrized .codn cptr . It also converts between Lisp objects of type .code cptr -and foreign pointers. However, it provides a measure of type safety. +and foreign pointers. Unlike the unparametrized type, it provides a measure of +type safety, and also supports the conversion of +.code carray +objects. When a foreign pointer is converted to a Lisp object under control of the parametrized @@ -74544,7 +74547,34 @@ is specified as .codn nil , then this is precisely equivalent to the unparametrized .code cptr -which doesn't provides the above safety measure. +which doesn't provide the above safety measure. + +A +.code carray +object may also be converted to a foreign pointer under the control of +a parametrized +.code cptr +type. The +.code carray +object's internal pointer becomes the foreign pointer value. +The conversion is only permitted if the following two restrictions are not met, +otherwise an error exception is thrown. +Firstly, the +.meta type-sym +of the +.code cptr +type must be the name of an FFI type, at the time when the +.code cptr +type expression is processed, otherwise the +.code cptr +is not associated with a type. +Secondly, the +.code carray +object being converted must have an element type which matches the +FFI type denoted by the +.code cptr +object's +.metn type-sym . Pointer type safety is useful, because FFI can be used to create bindings to large application programming interfaces (APIs) in which objects of |