1 files changed, 80 insertions, 0 deletions
diff --git a/rnd.c b/rnd.c
new file mode 100644
index 0000000..7e24bf2
--- /dev/null
+++ b/rnd.c
@@ -0,0 +1,80 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+static char reservoir[128U << 10];
+static size_t reservoir_off = sizeof(reservoir);
+static int random_fd;
+static const char *random_fname;
+
+
+size_t
+max_blksize(void)
+{
+	size_t ret = sizeof(reservoir);
+	while (ret & (ret - 1U))
+		ret &= ret - 1U;
+	return ret;
+}
+
+
+void
+init_random(int fd, const char *fname)
+{
+	struct stat st;
+
+	random_fname = fname;
+	random_fd = fd;
+
+	errno = 0;
+	if (isatty(random_fd) || errno == EBADF) {
+	use_builtin_generator:
+		random_fd = -1;
+		libsimple_srand();
+	} else if (fstat(random_fd, &st)) {
+		if (errno == EBADF)
+			goto use_builtin_generator;
+		eprintf("fstat %s:", random_fname);
+	} else if (S_ISFIFO(st.st_mode) || S_ISCHR(st.st_mode) || S_ISSOCK(st.st_mode)) {
+		eprintf("%s is of a unsupported inode type (must be TTY, character device, FIFO, or socket)", fname);
+	}
+}
+
+
+const char *
+get_random(size_t needed)
+{
+	size_t off;
+	ssize_t r;
+
+	if (sizeof(reservoir) - reservoir_off >= needed)
+		return &reservoir[reservoir_off];
+
+	if (random_fd < 0) {
+		libsimple_random_bytes(&libsimple_random_bits, NULL, reservoir, reservoir_off);
+		reservoir_off = 0;
+		return reservoir;
+	}
+
+	for (off = 0; off < reservoir_off;) {
+		r = read(random_fd, &reservoir[off], reservoir_off - off);
+		if (r <= 0) {
+			if (!r)
+				eprintf("random source depleted");
+			if (errno == EINTR)
+				continue;
+			eprintf("read %s:", random_fname);
+		}
+		off += (size_t)r;
+	}
+
+	reservoir_off = 0;
+	return reservoir;
+}
+
+
+void
+used_random(ssize_t amount)
+{
+	reservoir_off += (size_t)amount;
+}