[Qemu-devel] [PATCH 1/5] qemu-char: Add new char device CirMemCharDriver

[Lei Li <lilei@linux.vnet.ibm.com>]

Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
---
 qemu-char.c |   84 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 84 insertions(+), 0 deletions(-)

diff --git a/qemu-char.c b/qemu-char.c
index 767da93..0470085 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -2591,6 +2591,90 @@ size_t qemu_chr_mem_osize(const CharDriverState *chr)
     return d->outbuf_size;
 }
 
+/*********************************************************/
+/*CircularMemory chardev*/
+
+typedef struct {
+    size_t cbuf_capacity;
+    size_t cbuf_in;
+    size_t cbuf_out;
+    size_t cbuf_count;
+    uint8_t *cbuf;
+} CircMemCharDriver;
+
+static int cirmem_chr_is_empty(CharDriverState *chr)
+{
+    CircMemCharDriver *d = chr->opaque;
+
+    return d->cbuf_count == 0;
+}
+
+static int cirmem_chr_is_full(CharDriverState *chr)
+{
+    CircMemCharDriver *d = chr->opaque;
+
+    return d->cbuf_count == d->cbuf_capacity;
+}
+
+static int cirmem_chr_write(CharDriverState *chr, const uint8_t *buf, int len)
+{
+    CircMemCharDriver *d = chr->opaque;
+    int left;
+
+    if (d->cbuf_capacity < len) {
+        return -1;
+    }
+
+    left = d->cbuf_capacity - d->cbuf_count % d->cbuf_capacity;
+
+    /* Some of cbuf need to be overwrited */
+    if (left < len) {
+        memcpy(d->cbuf + d->cbuf_in, buf, left);
+        memcpy(d->cbuf + d->cbuf_out, buf + left, len - left);
+        d->cbuf_out = (d->cbuf_out + len - left) % d->cbuf_capacity;
+        d->cbuf_count = d->cbuf_count + left;
+    } else {
+        /* Completely overwrite */
+        if (cirmem_chr_is_full(chr)) {
+            d->cbuf_out = (d->cbuf_out + len) % d->cbuf_capacity;
+        } else {
+        /* Enough cbuf to write */
+        d->cbuf_count += len;
+        }
+        memcpy(d->cbuf + d->cbuf_in, buf, len);
+    }
+
+    d->cbuf_in = (d->cbuf_in + len) % d->cbuf_capacity;
+
+    return len;
+}
+
+static void cirmem_chr_read(CharDriverState *chr, uint8_t *buf, int len)
+{
+    CircMemCharDriver *d = chr->opaque;
+    int left;
+
+    if (cirmem_chr_is_empty(chr)) {
+        return;
+    }
+
+    left = d->cbuf_capacity - d->cbuf_count % d->cbuf_capacity;
+
+    if (d->cbuf_capacity < len) {
+        len = d->cbuf_capacity;
+    }
+
+    if (left < len) {
+        memcpy(buf, d->cbuf + d->cbuf_out, left);
+        memcpy(buf + left, d->cbuf + d->cbuf_out + left, len - left);
+    } else {
+        memcpy(buf, d->cbuf + d->cbuf_out, len);
+    }
+
+    d->cbuf_out = (d->cbuf_out + len) % d->cbuf_capacity;
+    d->cbuf_count -= len;
+}
+
 QemuOpts *qemu_chr_parse_compat(const char *label, const char *filename)
 {
     char host[65], port[33], width[8], height[8];
-- 
1.7.7.6