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bhyveload: add a small ring buffer to the cb_putc function. #2226

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bhyveload: add a small ring buffer to the cb_putc function. #2226

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35 changes: 33 additions & 2 deletions usr.sbin/bhyveload/bhyveload.c
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Original file line number Diff line number Diff line change
Expand Up @@ -57,6 +57,7 @@
#include <sys/stat.h>
#include <sys/disk.h>
#include <sys/queue.h>
#include <sys/uio.h>

#include <machine/specialreg.h>
#include <machine/vmm.h>
Expand Down Expand Up @@ -89,6 +90,10 @@

#define NDISKS 32

#define BUF_SIZE 256
#define PRODUCE(u, p, n) {(u) += (n); (p) = ((p) + (n)) % BUF_SIZE; }
#define CONSUME(u, c, n) {(u) -= (n); (c) = ((c) + (n)) % BUF_SIZE; }

/*
* Reason for our loader reload and reentry, though these aren't really used
* at the moment.
Expand Down Expand Up @@ -125,9 +130,35 @@ static void cb_exit(void *arg, int v);
static void
cb_putc(void *arg __unused, int ch)
{
char c = ch;
static char buf[BUF_SIZE];
static uint cons = 0, prod = 0, used = 0;
struct iovec iov[2];
uint niov;
ssize_t rc;

/* If the buffer is full, discard one character. */
if (used == BUF_SIZE)
CONSUME(used, cons, 1);

buf[prod] = ch;
PRODUCE(used, prod, 1);

if (prod > cons) {
iov[0].iov_base = &buf[cons];
iov[0].iov_len = prod - cons;
niov = 1;
} else {
iov[0].iov_base = &buf[cons];
iov[0].iov_len = BUF_SIZE - cons;
iov[1].iov_base = buf;
iov[1].iov_len = prod;
niov = 2;
}

if ((rc = writev(consout_fd, iov, niov)) < 0)
return;

(void) write(consout_fd, &c, 1);
CONSUME(used, cons, rc);
}

static int
Expand Down
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