[Qemu-devel] [PATCH 1/6] qemu-char: Convert MemCharDriver to circular buffer

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

Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
---
 qemu-char.c |   96 +++++++++++++++++++++++++++++++++++++++++++++++-----------
 qemu-char.h |    2 +-
 2 files changed, 78 insertions(+), 20 deletions(-)

diff --git a/qemu-char.c b/qemu-char.c
index 398baf1..b21b93a 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -2528,38 +2528,96 @@ static CharDriverState *qemu_chr_open_socket(QemuOpts *opts)
 /***********************************************************/
 /* Memory chardev */
 typedef struct {
-    size_t outbuf_size;
-    size_t outbuf_capacity;
-    uint8_t *outbuf;
+    size_t cbuf_capacity;
+    size_t cbuf_in;
+    size_t cbuf_out;
+    size_t cbuf_count;
+    uint8_t *cbuf;
 } MemoryDriver;
 
+static int mem_chr_is_empty(CharDriverState *chr)
+{
+    MemoryDriver *d = chr->opaque;
+
+    return d->cbuf_count == 0;
+}
+
+static int mem_chr_is_full(CharDriverState *chr)
+{
+    MemoryDriver *d = chr->opaque;
+
+    return d->cbuf_count == d->cbuf_capacity;
+}
+
 static int mem_chr_write(CharDriverState *chr, const uint8_t *buf, int len)
 {
     MemoryDriver *d = chr->opaque;
+    int left;
 
-    /* TODO: the QString implementation has the same code, we should
-     * introduce a generic way to do this in cutils.c */
-    if (d->outbuf_capacity < d->outbuf_size + len) {
-        /* grow outbuf */
-        d->outbuf_capacity += len;
-        d->outbuf_capacity *= 2;
-        d->outbuf = g_realloc(d->outbuf, d->outbuf_capacity);
+    if (d->cbuf_capacity < len) {
+        return -1;
     }
 
-    memcpy(d->outbuf + d->outbuf_size, buf, len);
-    d->outbuf_size += len;
+    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 (mem_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;
 }
 
-void qemu_chr_init_mem(CharDriverState *chr)
+static void mem_chr_read(CharDriverState *chr, uint8_t *buf, int len)
+{
+    MemoryDriver *d = chr->opaque;
+    int left;
+
+    if (mem_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;
+}
+
+void qemu_chr_init_mem(CharDriverState *chr, size_t size)
 {
     MemoryDriver *d;
 
     d = g_malloc(sizeof(*d));
-    d->outbuf_size = 0;
-    d->outbuf_capacity = 4096;
-    d->outbuf = g_malloc0(d->outbuf_capacity);
+    d->cbuf_capacity = size;
+    d->cbuf_in = 0;
+    d->cbuf_out = 0;
+    d->cbuf_count = 0;
+    d->cbuf = g_malloc0(d->cbuf_capacity);
 
     memset(chr, 0, sizeof(*chr));
     chr->opaque = d;
@@ -2569,7 +2627,7 @@ void qemu_chr_init_mem(CharDriverState *chr)
 QString *qemu_chr_mem_to_qs(CharDriverState *chr)
 {
     MemoryDriver *d = chr->opaque;
-    return qstring_from_substr((char *) d->outbuf, 0, d->outbuf_size - 1);
+    return qstring_from_substr((char *) d->cbuf, 0, d->cbuf_count - 1);
 }
 
 /* NOTE: this driver can not be closed with qemu_chr_delete()! */
@@ -2577,7 +2635,7 @@ void qemu_chr_close_mem(CharDriverState *chr)
 {
     MemoryDriver *d = chr->opaque;
 
-    g_free(d->outbuf);
+    g_free(d->cbuf);
     g_free(chr->opaque);
     chr->opaque = NULL;
     chr->chr_write = NULL;
@@ -2586,7 +2644,7 @@ void qemu_chr_close_mem(CharDriverState *chr)
 size_t qemu_chr_mem_osize(const CharDriverState *chr)
 {
     const MemoryDriver *d = chr->opaque;
-    return d->outbuf_size;
+    return d->cbuf_count;
 }
 
 QemuOpts *qemu_chr_parse_compat(const char *label, const char *filename)
diff --git a/qemu-char.h b/qemu-char.h
index 486644b..d8d90cc 100644
--- a/qemu-char.h
+++ b/qemu-char.h
@@ -243,7 +243,7 @@ CharDriverState *qemu_chr_open_eventfd(int eventfd);
 extern int term_escape_char;
 
 /* memory chardev */
-void qemu_chr_init_mem(CharDriverState *chr);
+void qemu_chr_init_mem(CharDriverState *chr, size_t size);
 void qemu_chr_close_mem(CharDriverState *chr);
 QString *qemu_chr_mem_to_qs(CharDriverState *chr);
 size_t qemu_chr_mem_osize(const CharDriverState *chr);
-- 
1.7.7.6