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peek-byte in Scheme
* libguile/ports.c (trampoline_to_c_read, trampoline_to_c_write): Since C might assume that the indices are within bounds of the bytevector, verify them more here. (scm_port_random_access_p, scm_port_read_buffering) (scm_set_port_read_buffer, scm_port_read, scm_port_write): New helpers exposed to (ice-9 ports). (scm_port_read_buffer, scm_port_write_buffer): Don't flush or validate port mode; we do that in Scheme. * module/ice-9/ports.scm: Implement enough of port machinery to implement peek-byte in Scheme. Not yet exported.
This commit is contained in:
Andy Wingo
parent
300c85b0f0
commit
6a752bcf2a
3 changed files with 169 additions and 30 deletions
110
libguile/ports.c
110
libguile/ports.c
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@ -258,11 +258,20 @@ scm_make_port_type (char *name,
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static SCM
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trampoline_to_c_read (SCM port, SCM dst, SCM start, SCM count)
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#define FUNC_NAME "port-read"
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{
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size_t c_start, c_count;
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SCM_VALIDATE_OPPORT (1, port);
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c_start = scm_to_size_t (start);
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c_count = scm_to_size_t (count);
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SCM_ASSERT_RANGE (2, start, start <= count);
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SCM_ASSERT_RANGE (3, count, c_start+c_count <= scm_c_bytevector_length (dst));
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return scm_from_size_t
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(SCM_PORT_DESCRIPTOR (port)->c_read
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(port, dst, scm_to_size_t (start), scm_to_size_t (count)));
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(SCM_PORT_DESCRIPTOR (port)->c_read (port, dst, c_start, c_count));
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}
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#undef FUNC_NAME
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static size_t
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trampoline_to_scm_read (SCM port, SCM dst, size_t start, size_t count)
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@ -274,11 +283,20 @@ trampoline_to_scm_read (SCM port, SCM dst, size_t start, size_t count)
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static SCM
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trampoline_to_c_write (SCM port, SCM src, SCM start, SCM count)
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#define FUNC_NAME "port-write"
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{
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size_t c_start, c_count;
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SCM_VALIDATE_OPPORT (1, port);
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c_start = scm_to_size_t (start);
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c_count = scm_to_size_t (count);
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SCM_ASSERT_RANGE (2, start, c_start <= c_count);
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SCM_ASSERT_RANGE (3, count, c_start+c_count <= scm_c_bytevector_length (src));
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return scm_from_size_t
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(SCM_PORT_DESCRIPTOR (port)->c_write
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(port, src, scm_to_size_t (start), scm_to_size_t (count)));
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(SCM_PORT_DESCRIPTOR (port)->c_write (port, src, c_start, c_count));
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}
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#undef FUNC_NAME
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static size_t
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trampoline_to_scm_write (SCM port, SCM src, size_t start, size_t count)
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@ -2457,43 +2475,75 @@ scm_fill_input (SCM port)
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return read_buf;
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}
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SCM_DEFINE (scm_port_random_access_p, "port-random-access?", 1, 0, 0,
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(SCM port),
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"Return true if the port is random-access, or false otherwise.")
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#define FUNC_NAME s_scm_port_random_access_p
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{
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SCM_VALIDATE_OPPORT (1, port);
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return scm_from_bool (SCM_PTAB_ENTRY (port)->rw_random);
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}
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#undef FUNC_NAME
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SCM_DEFINE (scm_port_read_buffering, "port-read-buffering", 1, 0, 0,
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(SCM port),
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"Return the amount of read buffering on a port, in bytes.")
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#define FUNC_NAME s_scm_port_read_buffering
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{
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SCM_VALIDATE_OPINPORT (1, port);
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return scm_from_size_t (SCM_PTAB_ENTRY (port)->read_buffering);
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}
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#undef FUNC_NAME
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SCM_DEFINE (scm_set_port_read_buffer_x, "set-port-read-buffer!", 2, 0, 0,
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(SCM port, SCM buf),
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"Reset the read buffer on an input port.")
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#define FUNC_NAME s_scm_set_port_read_buffer_x
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{
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SCM_VALIDATE_OPINPORT (1, port);
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SCM_ASSERT_TYPE (scm_is_vector (buf) && scm_c_vector_length (buf) >= 4,
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buf, 2, FUNC_NAME, "port buffer");
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SCM_PTAB_ENTRY (port)->read_buf = buf;
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return SCM_UNSPECIFIED;
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}
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#undef FUNC_NAME
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SCM_DEFINE (scm_port_read, "port-read", 1, 0, 0, (SCM port),
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"Return the read function for an input port.")
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#define FUNC_NAME s_scm_port_read
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{
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SCM_VALIDATE_OPINPORT (1, port);
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return SCM_PORT_DESCRIPTOR (port)->scm_read;
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}
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#undef FUNC_NAME
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SCM_DEFINE (scm_port_write, "port-write", 1, 0, 0,
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(SCM port),
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"Return the write function for an output port.")
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#define FUNC_NAME s_scm_port_write
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{
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SCM_VALIDATE_OPOUTPORT (1, port);
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return SCM_PORT_DESCRIPTOR (port)->scm_write;
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}
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#undef FUNC_NAME
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SCM_DEFINE (scm_port_read_buffer, "port-read-buffer", 1, 0, 0,
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(SCM port),
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"Return the read buffer for a port. If the port is\n"
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"random-access, its write buffer, if any, will be flushed\n"
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"if needed.")
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"Return the read buffer for a port.")
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#define FUNC_NAME s_scm_port_read_buffer
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{
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scm_t_port *pt;
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SCM_VALIDATE_OPINPORT (1, port);
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pt = SCM_PTAB_ENTRY (port);
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if (pt->rw_random)
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scm_flush (pt->port);
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return pt->read_buf;
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SCM_VALIDATE_OPPORT (1, port);
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return SCM_PTAB_ENTRY (port)->read_buf;
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}
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#undef FUNC_NAME
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SCM_DEFINE (scm_port_write_buffer, "port-write-buffer", 1, 0, 0,
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(SCM port),
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"Return the write buffer for a port. If the port is\n"
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"random-access, its read buffer, if any, will be discarded\n"
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"if needed.")
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"Return the write buffer for a port.")
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#define FUNC_NAME s_scm_port_write_buffer
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{
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scm_t_port *pt;
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SCM_VALIDATE_OPOUTPORT (1, port);
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pt = SCM_PTAB_ENTRY (port);
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if (pt->rw_random)
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scm_end_input (pt->port);
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return pt->write_buf;
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SCM_VALIDATE_OPPORT (1, port);
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return SCM_PTAB_ENTRY (port)->write_buf;
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}
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#undef FUNC_NAME
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@ -316,6 +316,12 @@ SCM_API SCM scm_drain_input (SCM port);
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SCM_API void scm_end_input (SCM port);
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SCM_API SCM scm_force_output (SCM port);
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SCM_API void scm_flush (SCM port);
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SCM_INTERNAL SCM scm_port_random_access_p (SCM port);
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SCM_INTERNAL SCM scm_port_read_buffering (SCM port);
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SCM_INTERNAL SCM scm_set_port_read_buffer_x (SCM port, SCM buf);
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SCM_INTERNAL SCM scm_port_read (SCM port);
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SCM_INTERNAL SCM scm_port_write (SCM port);
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SCM_INTERNAL SCM scm_port_read_buffer (SCM port);
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SCM_INTERNAL SCM scm_port_write_buffer (SCM port);
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@ -26,6 +26,7 @@
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(define-module (ice-9 ports)
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#:use-module (rnrs bytevectors)
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#:export (;; Definitions from ports.c.
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%port-property
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%set-port-property!
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@ -153,6 +154,88 @@
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(define-syntax-rule (port-buffer-bytevector buf) (vector-ref buf 0))
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(define-syntax-rule (port-buffer-cur buf) (vector-ref buf 1))
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(define-syntax-rule (port-buffer-end buf) (vector-ref buf 2))
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(define-syntax-rule (port-buffer-has-eof? buf) (vector-ref buf 3))
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(define-syntax-rule (set-port-buffer-cur! buf cur)
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(vector-set! buf 1 cur))
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(define-syntax-rule (set-port-buffer-end! buf end)
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(vector-set! buf 2 end))
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(define-syntax-rule (set-port-buffer-has-eof?! buf has-eof?)
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(vector-set! buf 3 has-eof?))
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(define (make-port-buffer size)
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(vector (make-bytevector size 0) 0 0 #f))
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(define (write-bytes port src start count)
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(let ((written ((port-write port) port src start count)))
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(unless (<= 0 written count)
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(error "bad return from port write function" written))
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(when (< written count)
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(write-bytes port src (+ start written) (- count written)))))
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(define (flush-output port)
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(let* ((buf (port-write-buffer port))
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(cur (port-buffer-cur buf))
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(end (port-buffer-end buf)))
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(when (< cur end)
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;; Update cursors before attempting to write, assuming that I/O
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;; errors are sticky. That way if the write throws an error,
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;; causing the computation to abort, and possibly causing the port
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;; to be collected by GC when it's open, any subsequent close-port
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;; or force-output won't signal *another* error.
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(set-port-buffer-cur! buf 0)
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(set-port-buffer-end! buf 0)
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(write-bytes port (port-buffer-bytevector buf) cur (- end cur)))))
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(define (read-bytes port dst start count)
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(let ((read ((port-read port) port dst start count)))
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(unless (<= 0 read count)
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(error "bad return from port read function" read))
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read))
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(define (fill-input port)
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(let ((buf (port-read-buffer port)))
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(cond
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((or (< (port-buffer-cur buf) (port-buffer-end buf))
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(port-buffer-has-eof? buf))
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buf)
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(else
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(unless (input-port? port)
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(error "not an input port" port))
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(when (port-random-access? port)
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(flush-output port))
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(let* ((read-buffering (port-read-buffering port))
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(buf (if (= (bytevector-length (port-buffer-bytevector buf))
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read-buffering)
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buf
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(let ((buf (make-port-buffer read-buffering)))
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(set-port-read-buffer! port buf)
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buf)))
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(bv (port-buffer-bytevector buf))
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(start (port-buffer-end buf))
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(count (- (bytevector-length bv) start))
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(read (read-bytes port bv start count)))
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(set-port-buffer-end! buf (+ start read))
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(set-port-buffer-has-eof?! buf (zero? count))
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buf)))))
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(define (peek-byte port)
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(let* ((buf (port-read-buffer port))
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(cur (port-buffer-cur buf)))
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(if (< cur (port-buffer-end buf))
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(bytevector-u8-ref (port-buffer-bytevector buf) cur)
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(let* ((buf (fill-input port))
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(cur (port-buffer-cur buf)))
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(if (< cur (port-buffer-end buf))
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(bytevector-u8-ref (port-buffer-bytevector buf) cur)
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the-eof-object)))))
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;;; Current ports as parameters.
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;;;
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