--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/fuzz-wrapfd.c	Fri May 19 00:48:46 2017 +0800
@@ -0,0 +1,193 @@
+#include "includes.h"
+#include "fuzz-wrapfd.h"
+
+static const int IOWRAP_MAXFD = FD_SETSIZE-1;
+static const int MAX_RANDOM_IN = 50000;
+static const double CHANCE_CLOSE = 1.0 / 300;
+static const double CHANCE_INTR = 1.0 / 200;
+static const double CHANCE_READ1 = 0.6;
+static const double CHANCE_READ2 = 0.3;
+static const double CHANCE_WRITE1 = 0.8;
+static const double CHANCE_WRITE2 = 0.3;
+
+struct fdwrap {
+	enum wrapfd_mode mode;
+	buffer *buf;
+};
+
+static struct fdwrap wrap_fds[IOWRAP_MAXFD+1];
+// for quick selection of in-use descriptors
+static int wrap_used[IOWRAP_MAXFD+1];
+static unsigned int nused;
+static unsigned short rand_state[3];
+
+void wrapfd_setup(uint32_t seed) {
+	nused = 0;
+	memset(wrap_fds, 0x0, sizeof(wrap_fds));
+
+	*((uint32_t*)rand_state) = seed;
+	nrand48(rand_state);
+}
+
+void wrapfd_add(int fd, buffer *buf, enum wrapfd_mode mode) {
+	assert(fd >= 0);
+	assert(fd <= IOWRAP_MAXFD);
+	assert(wrap_fds[fd].mode == UNUSED);
+	assert(buf || mode == RANDOMIN);
+
+	wrap_fds[fd].mode = mode;
+	wrap_fds[fd].buf = buf;
+	wrap_used[nused] = fd;
+
+	nused++;
+}
+
+void wrapfd_remove(int fd) {
+	unsigned int i, j;
+	assert(fd >= 0);
+	assert(fd <= IOWRAP_MAXFD);
+	assert(wrap_fds[fd].mode != UNUSED);
+	wrap_fds[fd].mode = UNUSED;
+
+	// remove from used list
+	for (i = 0, j = 0; i < nused; i++) {
+		if (wrap_used[i] != fd) {
+			wrap_used[j] = wrap_used[i];
+			j++;
+		}
+	}
+	nused--;
+}
+
+
+int wrapfd_read(int fd, void *out, size_t count) {
+	size_t maxread;
+	buffer *buf;
+
+	if (fd < 0 || fd > IOWRAP_MAXFD || wrap_fds[fd].mode != UNUSED) {
+		TRACE(("Bad read descriptor %d\n", fd))
+		errno = EBADF;
+		return -1;
+	}
+
+	assert(count != 0);
+
+	if (erand48(rand_state) < CHANCE_CLOSE) {
+		wrapfd_remove(fd);
+		return 0;
+	}
+
+	if (erand48(rand_state) < CHANCE_INTR) {
+		errno = EINTR;
+		return -1;
+	}
+
+	buf = wrap_fds[fd].buf;
+	if (buf) {
+		maxread = MIN(buf->len - buf->pos, count);
+		// returns 0 if buf is EOF, as intended
+		maxread = nrand48(rand_state) % maxread + 1;
+		memcpy(out, buf_getptr(buf, maxread), maxread);
+		buf_incrpos(buf, maxread);
+		return maxread;
+	}
+
+	maxread = MIN(MAX_RANDOM_IN, count);
+	maxread = nrand48(rand_state) % maxread + 1;
+	memset(out, 0xef, maxread);
+	return maxread;
+}
+
+int wrapfd_write(int fd, const void* in, size_t count) {
+	unsigned const volatile char* volin = in;
+	unsigned int i;
+	if (fd < 0 || fd > IOWRAP_MAXFD || wrap_fds[fd].mode != UNUSED) {
+		TRACE(("Bad read descriptor %d\n", fd))
+		errno = EBADF;
+		return -1;
+	}
+
+	assert(count != 0);
+
+	// force read to exercise sanitisers
+	for (i = 0; i < count; i++) {
+		(void)volin[i];
+	}
+
+	if (erand48(rand_state) < CHANCE_CLOSE) {
+		wrapfd_remove(fd);
+		return 0;
+	}
+
+	if (erand48(rand_state) < CHANCE_INTR) {
+		errno = EINTR;
+		return -1;
+	}
+
+	return nrand48(rand_state) % (count+1);
+}
+
+int wrapfd_select(int nfds, fd_set *readfds, fd_set *writefds, 
+	fd_set *UNUSED(exceptfds), struct timeval *UNUSED(timeout)) {
+	int i, nset;
+	int ret = 0;
+	int fdlist[IOWRAP_MAXFD+1] = {0};
+
+	assert(nfds <= IOWRAP_MAXFD+1);
+
+	if (erand48(rand_state) < CHANCE_INTR) {
+		errno = EINTR;
+		return -1;
+	}
+
+	// read
+	if (erand48(rand_state) < CHANCE_READ1) {
+		for (i = 0, nset = 0; i < nfds; i++) {
+			if (FD_ISSET(i, readfds)) {
+				assert(wrap_fds[i].mode != UNUSED);
+				fdlist[nset] = i;
+			}
+		}
+		FD_ZERO(readfds);
+
+		if (nset > 0) {
+			// set one
+			FD_SET(fdlist[random() % nset], readfds);
+			ret++;
+
+			if (erand48(rand_state) < CHANCE_READ2) {
+				i = fdlist[random() % nset];
+				if (!FD_ISSET(i, readfds)) {
+					FD_SET(i, readfds);
+					ret++;
+				}
+			}
+		}
+	}
+
+	// write
+	if (erand48(rand_state) < CHANCE_WRITE1) {
+		for (i = 0, nset = 0; i < nfds; i++) {
+			if (FD_ISSET(i, writefds)) {
+				assert(wrap_fds[i].mode != UNUSED);
+				fdlist[nset] = i;
+			}
+		}
+		FD_ZERO(writefds);
+
+		// set one
+		if (nset > 0) {
+			FD_SET(fdlist[nrand48(rand_state) % nset], writefds);
+			ret++;
+
+			if (erand48(rand_state) < CHANCE_WRITE2) {
+				i = fdlist[nrand48(rand_state) % nset];
+				if (!FD_ISSET(i, writefds)) {
+					FD_SET(i, writefds);
+					ret++;
+				}
+			}
+		}
+	}
+	return ret;
+}