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-rw-r--r--src/util/nbbio.c382
1 files changed, 382 insertions, 0 deletions
diff --git a/src/util/nbbio.c b/src/util/nbbio.c
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+/*++
+/* NAME
+/* nbbio 3
+/* SUMMARY
+/* non-blocking buffered I/O
+/* SYNOPSIS
+/* #include <nbbio.h>
+/*
+/* NBBIO *nbbio_create(fd, bufsize, label, action, context)
+/* int fd;
+/* ssize_t bufsize;
+/* const char *label;
+/* void (*action)(int event, void *context);
+/* char *context;
+/*
+/* void nbbio_free(np)
+/* NBBIO *np;
+/*
+/* void nbbio_enable_read(np, timeout)
+/* NBBIO *np;
+/* int timeout;
+/*
+/* void nbbio_enable_write(np, timeout)
+/* NBBIO *np;
+/* int timeout;
+/*
+/* void nbbio_disable_readwrite(np)
+/* NBBIO *np;
+/*
+/* void nbbio_slumber(np, timeout)
+/* NBBIO *np;
+/* int timeout;
+/*
+/* int NBBIO_ACTIVE_FLAGS(np)
+/* NBBIO *np;
+/*
+/* int NBBIO_ERROR_FLAGS(np)
+/* NBBIO *np;
+/*
+/* const ssize_t NBBIO_BUFSIZE(np)
+/* NBBIO *np;
+/*
+/* ssize_t NBBIO_READ_PEND(np)
+/* NBBIO *np;
+/*
+/* char *NBBIO_READ_BUF(np)
+/* NBBIO *np;
+/*
+/* const ssize_t NBBIO_WRITE_PEND(np)
+/* NBBIO *np;
+/*
+/* char *NBBIO_WRITE_BUF(np)
+/* NBBIO *np;
+/* DESCRIPTION
+/* This module implements low-level support for event-driven
+/* I/O on a full-duplex stream. Read/write events are handled
+/* by pseudothreads that run under control by the events(5)
+/* module. After each I/O operation, the application is
+/* notified via a call-back routine.
+/*
+/* It is up to the call-back routine to turn on/off read/write
+/* events as appropriate. It is an error to leave read events
+/* enabled for a buffer that is full, or to leave write events
+/* enabled for a buffer that is empty.
+/*
+/* nbbio_create() creates a pair of buffers of the named size
+/* for the named stream. The label specifies the purpose of
+/* the stream, and is used for diagnostic messages. The
+/* nbbio(3) event handler invokes the application call-back
+/* routine with the current event type (EVENT_READ etc.) and
+/* with the application-specified context.
+/*
+/* nbbio_free() terminates any pseudothreads associated with
+/* the named buffer pair, closes the stream, and destroys the
+/* buffer pair.
+/*
+/* nbbio_enable_read() enables a read pseudothread (if one
+/* does not already exist) for the named buffer pair, and
+/* (re)starts the buffer pair's timer. It is an error to enable
+/* a read pseudothread while the read buffer is full, or while
+/* a write pseudothread is still enabled.
+/*
+/* nbbio_enable_write() enables a write pseudothread (if one
+/* does not already exist) for the named buffer pair, and
+/* (re)starts the buffer pair's timer. It is an error to enable
+/* a write pseudothread while the write buffer is empty, or
+/* while a read pseudothread is still enabled.
+/*
+/* nbbio_disable_readwrite() disables any read/write pseudothreads
+/* for the named buffer pair, including timeouts. To ensure
+/* buffer liveness, use nbbio_slumber() instead of
+/* nbbio_disable_readwrite(). It is no error to call this
+/* function while no read/write pseudothread is enabled.
+/*
+/* nbbio_slumber() disables any read/write pseudothreads for
+/* the named buffer pair, but keeps the timer active to ensure
+/* buffer liveness. It is no error to call this function while
+/* no read/write pseudothread is enabled.
+/*
+/* NBBIO_ERROR_FLAGS() returns the error flags for the named buffer
+/* pair: zero or more of NBBIO_FLAG_EOF (read EOF), NBBIO_FLAG_ERROR
+/* (read/write error) or NBBIO_FLAG_TIMEOUT (time limit
+/* exceeded).
+/*
+/* NBBIO_ACTIVE_FLAGS() returns the pseudothread flags for the
+/* named buffer pair: NBBIO_FLAG_READ (read pseudothread is
+/* active), NBBIO_FLAG_WRITE (write pseudothread is active),
+/* or zero (no pseudothread is active).
+/*
+/* NBBIO_WRITE_PEND() and NBBIO_WRITE_BUF() evaluate to the
+/* number of to-be-written bytes and the write buffer for the
+/* named buffer pair. NBBIO_WRITE_PEND() must be updated by
+/* the application code that fills the write buffer; no more
+/* than NBBIO_BUFSIZE() bytes may be filled.
+/*
+/* NBBIO_READ_PEND() and NBBIO_READ_BUF() evaluate to the
+/* number of unread bytes and the read buffer for the named
+/* buffer pair. NBBIO_READ_PEND() and NBBIO_READ_BUF() must
+/* be updated by the application code that drains the read
+/* buffer.
+/* SEE ALSO
+/* events(3) event manager
+/* DIAGNOSTICS
+/* Panic: interface violation.
+/*
+/* Fatal: out of memory.
+/* LICENSE
+/* .ad
+/* .fi
+/* The Secure Mailer license must be distributed with this software.
+/* AUTHOR(S)
+/* Wietse Venema
+/* IBM T.J. Watson Research
+/* P.O. Box 704
+/* Yorktown Heights, NY 10598, USA
+/*
+/* Wietse Venema
+/* Google, Inc.
+/* 111 8th Avenue
+/* New York, NY 10011, USA
+/*--*/
+
+ /*
+ * System library.
+ */
+#include <sys_defs.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h> /* memmove() */
+
+ /*
+ * Utility library.
+ */
+#include <mymalloc.h>
+#include <msg.h>
+#include <events.h>
+#include <nbbio.h>
+
+/* nbbio_event - non-blocking event handler */
+
+static void nbbio_event(int event, void *context)
+{
+ const char *myname = "nbbio_event";
+ NBBIO *np = (NBBIO *) context;
+ ssize_t count;
+
+ switch (event) {
+
+ /*
+ * Read data into the read buffer. Leave it up to the application to
+ * drain the buffer until it is empty.
+ */
+ case EVENT_READ:
+ if (np->read_pend == np->bufsize)
+ msg_panic("%s: socket fd=%d: read buffer is full",
+ myname, np->fd);
+ if (np->read_pend < 0 || np->read_pend > np->bufsize)
+ msg_panic("%s: socket fd=%d: bad pending read count %ld",
+ myname, np->fd, (long) np->read_pend);
+ count = read(np->fd, np->read_buf + np->read_pend,
+ np->bufsize - np->read_pend);
+ if (count > 0) {
+ np->read_pend += count;
+ if (msg_verbose)
+ msg_info("%s: read %ld on %s fd=%d",
+ myname, (long) count, np->label, np->fd);
+ } else if (count == 0) {
+ np->flags |= NBBIO_FLAG_EOF;
+ if (msg_verbose)
+ msg_info("%s: read EOF on %s fd=%d",
+ myname, np->label, np->fd);
+ } else {
+ if (errno == EAGAIN)
+ msg_warn("%s: read() returns EAGAIN on readable descriptor",
+ myname);
+ np->flags |= NBBIO_FLAG_ERROR;
+ if (msg_verbose)
+ msg_info("%s: read %s fd=%d: %m", myname, np->label, np->fd);
+ }
+ break;
+
+ /*
+ * Drain data from the output buffer. Notify the application
+ * whenever some bytes are written.
+ *
+ * XXX Enforce a total time limit to ensure liveness when a hostile
+ * receiver sets a very small TCP window size.
+ */
+ case EVENT_WRITE:
+ if (np->write_pend == 0)
+ msg_panic("%s: socket fd=%d: empty write buffer", myname, np->fd);
+ if (np->write_pend < 0 || np->write_pend > np->bufsize)
+ msg_panic("%s: socket fd=%d: bad pending write count %ld",
+ myname, np->fd, (long) np->write_pend);
+ count = write(np->fd, np->write_buf, np->write_pend);
+ if (count > 0) {
+ np->write_pend -= count;
+ if (np->write_pend > 0)
+ memmove(np->write_buf, np->write_buf + count, np->write_pend);
+ } else {
+ if (errno == EAGAIN)
+ msg_warn("%s: write() returns EAGAIN on writable descriptor",
+ myname);
+ np->flags |= NBBIO_FLAG_ERROR;
+ if (msg_verbose)
+ msg_info("%s: write %s fd=%d: %m", myname, np->label, np->fd);
+ }
+ break;
+
+ /*
+ * Something bad happened.
+ */
+ case EVENT_XCPT:
+ np->flags |= NBBIO_FLAG_ERROR;
+ if (msg_verbose)
+ msg_info("%s: error on %s fd=%d: %m", myname, np->label, np->fd);
+ break;
+
+ /*
+ * Something good didn't happen.
+ */
+ case EVENT_TIME:
+ np->flags |= NBBIO_FLAG_TIMEOUT;
+ if (msg_verbose)
+ msg_info("%s: %s timeout on %s fd=%d",
+ myname, NBBIO_OP_NAME(np), np->label, np->fd);
+ break;
+
+ default:
+ msg_panic("%s: unknown event %d", myname, event);
+ }
+
+ /*
+ * Application notification. The application will check for any error
+ * flags, copy application data from or to our buffer pair, and decide
+ * what I/O happens next.
+ */
+ np->action(event, np->context);
+}
+
+/* nbbio_enable_read - enable reading from socket into buffer */
+
+void nbbio_enable_read(NBBIO *np, int timeout)
+{
+ const char *myname = "nbbio_enable_read";
+
+ /*
+ * Sanity checks.
+ */
+ if (np->flags & (NBBIO_MASK_ACTIVE & ~NBBIO_FLAG_READ))
+ msg_panic("%s: socket fd=%d is enabled for %s",
+ myname, np->fd, NBBIO_OP_NAME(np));
+ if (timeout <= 0)
+ msg_panic("%s: socket fd=%d: bad timeout %d",
+ myname, np->fd, timeout);
+ if (np->read_pend >= np->bufsize)
+ msg_panic("%s: socket fd=%d: read buffer is full",
+ myname, np->fd);
+
+ /*
+ * Enable events.
+ */
+ if ((np->flags & NBBIO_FLAG_READ) == 0) {
+ event_enable_read(np->fd, nbbio_event, (void *) np);
+ np->flags |= NBBIO_FLAG_READ;
+ }
+ event_request_timer(nbbio_event, (void *) np, timeout);
+}
+
+/* nbbio_enable_write - enable writing from buffer to socket */
+
+void nbbio_enable_write(NBBIO *np, int timeout)
+{
+ const char *myname = "nbbio_enable_write";
+
+ /*
+ * Sanity checks.
+ */
+ if (np->flags & (NBBIO_MASK_ACTIVE & ~NBBIO_FLAG_WRITE))
+ msg_panic("%s: socket fd=%d is enabled for %s",
+ myname, np->fd, NBBIO_OP_NAME(np));
+ if (timeout <= 0)
+ msg_panic("%s: socket fd=%d: bad timeout %d",
+ myname, np->fd, timeout);
+ if (np->write_pend <= 0)
+ msg_panic("%s: socket fd=%d: empty write buffer",
+ myname, np->fd);
+
+ /*
+ * Enable events.
+ */
+ if ((np->flags & NBBIO_FLAG_WRITE) == 0) {
+ event_enable_write(np->fd, nbbio_event, (void *) np);
+ np->flags |= NBBIO_FLAG_WRITE;
+ }
+ event_request_timer(nbbio_event, (void *) np, timeout);
+}
+
+/* nbbio_disable_readwrite - disable read/write/timer events */
+
+void nbbio_disable_readwrite(NBBIO *np)
+{
+ np->flags &= ~NBBIO_MASK_ACTIVE;
+ event_disable_readwrite(np->fd);
+ event_cancel_timer(nbbio_event, (void *) np);
+}
+
+/* nbbio_slumber - disable read/write events, keep timer */
+
+void nbbio_slumber(NBBIO *np, int timeout)
+{
+ np->flags &= ~NBBIO_MASK_ACTIVE;
+ event_disable_readwrite(np->fd);
+ event_request_timer(nbbio_event, (void *) np, timeout);
+}
+
+/* nbbio_create - create socket buffer */
+
+NBBIO *nbbio_create(int fd, ssize_t bufsize, const char *label,
+ NBBIO_ACTION action, void *context)
+{
+ NBBIO *np;
+
+ /*
+ * Sanity checks.
+ */
+ if (fd < 0)
+ msg_panic("nbbio_create: bad file descriptor: %d", fd);
+ if (bufsize <= 0)
+ msg_panic("nbbio_create: bad buffer size: %ld", (long) bufsize);
+
+ /*
+ * Create a new buffer pair.
+ */
+ np = (NBBIO *) mymalloc(sizeof(*np));
+ np->fd = fd;
+ np->bufsize = bufsize;
+ np->label = mystrdup(label);
+ np->action = action;
+ np->context = context;
+ np->flags = 0;
+
+ np->read_buf = mymalloc(bufsize);
+ np->read_pend = 0;
+
+ np->write_buf = mymalloc(bufsize);
+ np->write_pend = 0;
+
+ return (np);
+}
+
+/* nbbio_free - destroy socket buffer */
+
+void nbbio_free(NBBIO *np)
+{
+ nbbio_disable_readwrite(np);
+ (void) close(np->fd);
+ myfree(np->label);
+ myfree(np->read_buf);
+ myfree(np->write_buf);
+ myfree((void *) np);
+}
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