@@ 145,6 145,27 @@
((_ type)
(sizeof* type))))
+(define-syntax struct-alignment
+ (syntax-rules ()
+ "Compute the alignment for the aggregate made of TYPES at OFFSET. The
+result is the alignment of the \"most strictly aligned component\"."
+ ((_ offset types ...)
+ (max (align offset types) ...))))
+
+(define-syntax struct-size
+ (syntax-rules ()
+ "Return the size in bytes of the structure made of TYPES."
+ ((_ offset (types-processed ...))
+ ;; The SysV ABI P.S. says: "Aggregates (structures and arrays) and unions
+ ;; assume the alignment of their most strictly aligned component." As an
+ ;; example, a struct such as "int32, int16" has size 8, not 6.
+ (1+ (logior (1- offset)
+ (1- (struct-alignment offset types-processed ...)))))
+ ((_ offset (types-processed ...) type0 types ...)
+ (struct-size (+ (type-size type0) (align offset type0))
+ (type0 types-processed ...)
+ types ...))))
+
(define-syntax write-type
(syntax-rules (~)
((_ bv offset (type ~ order) value)
@@ 193,10 214,13 @@
(define-syntax define-c-struct
(syntax-rules ()
- "Define READ as a deserializer and WRITE! as a serializer for the C
-structure with the given TYPES. READ uses WRAP-FIELDS to return its value."
- ((_ name wrap-fields read write! (fields types) ...)
+ "Define SIZE as the size in bytes of the C structure made of FIELDS. READ
+as a deserializer and WRITE! as a serializer for the C structure with the
+given TYPES. READ uses WRAP-FIELDS to return its value."
+ ((_ name size wrap-fields read write! (fields types) ...)
(begin
+ (define size
+ (struct-size 0 () types ...))
(define (write! bv offset fields ...)
(write-types bv offset (types ...) (fields ...)))
(define* (read bv #:optional (offset 0))
@@ 559,6 583,7 @@ system to PUT-OLD."
32))
(define-c-struct sockaddr-in ;<linux/in.h>
+ sizeof-sockaddrin
(lambda (family port address)
(make-socket-address family address port))
read-sockaddr-in
@@ 568,6 593,7 @@ system to PUT-OLD."
(address (int32 ~ big)))
(define-c-struct sockaddr-in6 ;<linux/in6.h>
+ sizeof-sockaddr-in6
(lambda (family port flowinfo address scopeid)
(make-socket-address family address port flowinfo scopeid))
read-sockaddr-in6
@@ 832,6 858,7 @@ an <interface> object, and whose cdr is the pointer NEXT."
next))
(define-c-struct ifaddrs ;<ifaddrs.h>
+ %sizeof-ifaddrs
values->interface
read-ifaddrs
write-ifaddrs!
@@ 843,14 870,6 @@ an <interface> object, and whose cdr is the pointer NEXT."
(broadcastaddr '*)
(data '*))
-(define-syntax %struct-ifaddrs-type
- (identifier-syntax
- `(* * ,unsigned-int * * * *)))
-
-(define-syntax %sizeof-ifaddrs
- (identifier-syntax
- (sizeof* %struct-ifaddrs-type)))
-
(define (unfold-interface-list ptr)
"Call 'read-ifaddrs' on PTR and all its 'next' fields, recursively, and
return the list of resulting <interface> objects."
@@ 901,6 920,7 @@ network interface. This is implemented using the 'getifaddrs' libc function."
(y-pixels window-size-y-pixels))
(define-c-struct winsize ;<bits/ioctl-types.h>
+ sizeof-winsize
window-size
read-winsize
write-winsize!
@@ 909,18 929,16 @@ network interface. This is implemented using the 'getifaddrs' libc function."
(x-pixels unsigned-short)
(y-pixels unsigned-short))
-(define winsize-struct
- (list unsigned-short unsigned-short unsigned-short unsigned-short))
-
(define* (terminal-window-size #:optional (port (current-output-port)))
"Return a <window-size> structure describing the terminal at PORT, or raise
a 'system-error' if PORT is not backed by a terminal. This procedure
corresponds to the TIOCGWINSZ ioctl."
- (let* ((size (make-c-struct winsize-struct '(0 0 0 0)))
- (ret (%ioctl (fileno port) TIOCGWINSZ size))
+ (let* ((size (make-bytevector sizeof-winsize))
+ (ret (%ioctl (fileno port) TIOCGWINSZ
+ (bytevector->pointer size)))
(err (errno)))
(if (zero? ret)
- (read-winsize (pointer->bytevector size (sizeof winsize-struct)))
+ (read-winsize size)
(throw 'system-error "terminal-window-size" "~A"
(list (strerror err))
(list err)))))