Minor performance fix: Only rearrange buffers for BIG-REQUESTs.

[free-sw/xcb/libxcb] / src / xcb_out.c

diff --git a/src/xcb_out.c b/src/xcb_out.c
index 04b8365..442fcf5 100644 (file)
--- a/src/xcb_out.c
+++ b/src/xcb_out.c
@@ -27,6 +27,7 @@
 
 #include <assert.h>
 #include <stdlib.h>
+#include <unistd.h>
 #include <string.h>
 #include <errno.h>
 
@@ -47,6 +48,40 @@ static int force_sequence_wrap(XCBConnection *c)
     return ret;
 }
 
+static int _xcb_write(const int fd, char (*buf)[], int *count)
+{
+    int n = write(fd, *buf, *count);
+    if(n > 0)
+    {
+        *count -= n;
+        if(*count)
+            memmove(*buf, *buf + n, *count);
+    }
+    return n;
+}
+
+static int _xcb_writev(const int fd, struct iovec *vec, int count)
+{
+    int n = writev(fd, vec, count);
+    if(n > 0)
+    {
+        int rem = n;
+        for(; count; --count, ++vec)
+        {
+            int cur = vec->iov_len;
+            if(cur > rem)
+                cur = rem;
+            vec->iov_len -= cur;
+            vec->iov_base = (char *) vec->iov_base + cur;
+            rem -= cur;
+            if(vec->iov_len)
+                break;
+        }
+        assert(rem == 0);
+    }
+    return n;
+}
+
 /* Public interface */
 
 CARD32 XCBGetMaximumRequestLength(XCBConnection *c)
@@ -82,6 +117,24 @@ int XCBSendRequest(XCBConnection *c, unsigned int *request, struct iovec *vector
     assert(vector != 0);
     assert(req->count > 0);
 
+    /* set the major opcode, and the minor opcode for extensions */
+    if(req->ext)
+    {
+        const XCBQueryExtensionRep *extension = XCBGetExtensionData(c, req->ext);
+        /* TODO: better error handling here, please! */
+        assert(extension && extension->present);
+        ((CARD8 *) vector[0].iov_base)[0] = extension->major_opcode;
+        ((CARD8 *) vector[0].iov_base)[1] = req->opcode;
+
+        /* do we need to work around the X server bug described in glx.xml? */
+        if(strcmp(req->ext->name, "GLX") &&
+                ((req->opcode == 17 && ((CARD32 *) vector[0].iov_base)[0] == 0x10004) ||
+                 req->opcode == 21))
+            workaround = WORKAROUND_GLX_GET_FB_CONFIGS_BUG;
+    }
+    else
+        ((CARD8 *) vector[0].iov_base)[0] = req->opcode;
+
     /* put together the length field, possibly using BIGREQUESTS */
     for(i = 0; i < req->count; ++i)
         longlen += XCB_CEIL(vector[i].iov_len) >> 2;
@@ -99,38 +152,17 @@ int XCBSendRequest(XCBConnection *c, unsigned int *request, struct iovec *vector
     }
 
     /* set the length field. */
-    i = 0;
-    prefix[i].iov_base = vector[0].iov_base;
-    prefix[i].iov_len = sizeof(CARD32);
-    vector[0].iov_base = ((char *) vector[0].iov_base) + sizeof(CARD32);
-    vector[0].iov_len -= sizeof(CARD32);
-    ((CARD16 *) prefix[i].iov_base)[1] = shortlen;
-    ++i;
+    ((CARD16 *) vector[0].iov_base)[1] = shortlen;
     if(!shortlen)
     {
+        prefix[0].iov_base = vector[0].iov_base;
+        prefix[0].iov_len = sizeof(CARD32);
+        vector[0].iov_base = ((char *) vector[0].iov_base) + sizeof(CARD32);
+        vector[0].iov_len -= sizeof(CARD32);
         ++longlen;
-        prefix[i].iov_base = &longlen;
-        prefix[i].iov_len = sizeof(CARD32);
-        ++i;
-    }
-
-    /* set the major opcode, and the minor opcode for extensions */
-    if(req->ext)
-    {
-        const XCBQueryExtensionRep *extension = XCBGetExtensionData(c, req->ext);
-        /* TODO: better error handling here, please! */
-        assert(extension && extension->present);
-        ((CARD8 *) prefix[0].iov_base)[0] = extension->major_opcode;
-        ((CARD8 *) prefix[0].iov_base)[1] = req->opcode;
-
-        /* do we need to work around the X server bug described in glx.xml? */
-        if(strcmp(req->ext->name, "GLX") &&
-                ((req->opcode == 17 && ((CARD32 *) vector[0].iov_base)[0] == 0x10004) ||
-                 req->opcode == 21))
-            workaround = WORKAROUND_GLX_GET_FB_CONFIGS_BUG;
+        prefix[1].iov_base = &longlen;
+        prefix[1].iov_len = sizeof(CARD32);
     }
-    else
-        ((CARD8 *) prefix[0].iov_base)[0] = req->opcode;
 
     /* get a sequence number and arrange for delivery. */
     pthread_mutex_lock(&c->iolock);
@@ -145,7 +177,10 @@ int XCBSendRequest(XCBConnection *c, unsigned int *request, struct iovec *vector
     if(!req->isvoid)
         _xcb_in_expect_reply(c, *request, workaround);
 
-    ret = _xcb_out_write_block(c, prefix, i);
+    if(!shortlen)
+        ret = _xcb_out_write_block(c, prefix, 2);
+    else
+        ret = 1;
     if(ret > 0)
         ret = _xcb_out_write_block(c, vector, req->count);
     pthread_mutex_unlock(&c->iolock);
@@ -199,8 +234,9 @@ int _xcb_out_write(XCBConnection *c)
     else
         n = _xcb_write(c->fd, &c->out.queue, &c->out.queue_len);
 
-    if(n < 0 && errno == EAGAIN)
-        n = 1;
+    /* XXX: should "nothing was written" be considered failure or
+     * success for this function? it's not an I/O error, but... */
+    n = (n > 0) || (n < 0 && errno == EAGAIN);
 
     if(c->out.vec_len)
     {
@@ -258,7 +294,7 @@ int _xcb_out_write_block(XCBConnection *c, struct iovec *vector, size_t count)
         c->out.vec[c->out.vec_len].iov_base = (void *) pad;
         c->out.vec[c->out.vec_len++].iov_len = XCB_PAD(vector[i].iov_len);
     }
-    if(_xcb_out_flush(c) <= 0)
+    if(!_xcb_out_flush(c))
         len = -1;
     free(c->out.vec);
     c->out.vec = 0;
@@ -269,9 +305,9 @@ int _xcb_out_write_block(XCBConnection *c, struct iovec *vector, size_t count)
 int _xcb_out_flush(XCBConnection *c)
 {
     int ret = 1;
-    c->out.request_written = c->out.request;
     while(ret && (c->out.queue_len || c->out.vec_len))
         ret = _xcb_conn_wait(c, /*should_write*/ 1, &c->out.cond);
+    c->out.request_written = c->out.request;
     pthread_cond_broadcast(&c->out.cond);
     return ret;
 }