From 4ccf671cc6fbce349c7deca69cfa8e566823d4ed Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Sat, 31 Mar 2012 11:21:45 +0200
Subject: [PATCH] Better syncio.c with millisecond resolution.

---
 src/redis.h  |  6 +++---
 src/syncio.c | 61 ++++++++++++++++++++++++++++++++++++++--------------
 2 files changed, 48 insertions(+), 19 deletions(-)

diff --git a/src/redis.h b/src/redis.h
index 5d16722e..f3defca4 100644
--- a/src/redis.h
+++ b/src/redis.h
@@ -811,9 +811,9 @@ int equalStringObjects(robj *a, robj *b);
 unsigned long estimateObjectIdleTime(robj *o);
 
 /* Synchronous I/O with timeout */
-int syncWrite(int fd, char *ptr, ssize_t size, int timeout);
-int syncRead(int fd, char *ptr, ssize_t size, int timeout);
-int syncReadLine(int fd, char *ptr, ssize_t size, int timeout);
+ssize_t syncWrite(int fd, char *ptr, ssize_t size, long long timeout);
+ssize_t syncRead(int fd, char *ptr, ssize_t size, long long timeout);
+ssize_t syncReadLine(int fd, char *ptr, ssize_t size, long long timeout);
 
 /* Replication */
 void replicationFeedSlaves(list *slaves, int dictid, robj **argv, int argc);
diff --git a/src/syncio.c b/src/syncio.c
index 9958363b..b0c2969e 100644
--- a/src/syncio.c
+++ b/src/syncio.c
@@ -36,50 +36,79 @@
  * of the SYNC command where the slave does it in a blocking way, and
  * the MIGRATE command that must be blocking in order to be atomic from the
  * point of view of the two instances (one migrating the key and one receiving
- * the key). This is why need the following blocking I/O functions. */
+ * the key). This is why need the following blocking I/O functions.
+ *
+ * All the functions take the timeout in milliseconds. */
+
+#define REDIS_SYNCIO_RESOLUTION 10 /* Resolution in milliseconds */
 
-int syncWrite(int fd, char *ptr, ssize_t size, int timeout) {
+/* Write the specified payload to 'fd'. If writing the whole payload will be done
+ * within 'timeout' milliseconds the operation succeeds and 'size' is returned.
+ * Otherwise the operation fails, -1 is returned, and an unspecified partial write
+ * could be performed against the file descriptor. */
+ssize_t syncWrite(int fd, char *ptr, ssize_t size, long long timeout) {
     ssize_t nwritten, ret = size;
-    time_t start = time(NULL);
+    long long start = mstime();
+    long long remaining = timeout;
 
-    timeout++;
-    while(size) {
-        if (aeWait(fd,AE_WRITABLE,1000) & AE_WRITABLE) {
+    while(1) {
+        long long wait = (remaining > REDIS_SYNCIO_RESOLUTION) ?
+                          remaining : REDIS_SYNCIO_RESOLUTION;
+        long long elapsed;
+
+        if (aeWait(fd,AE_WRITABLE,wait) & AE_WRITABLE) {
             nwritten = write(fd,ptr,size);
             if (nwritten == -1) return -1;
             ptr += nwritten;
             size -= nwritten;
+            if (size == 0) return ret;
         }
-        if ((time(NULL)-start) > timeout) {
+        elapsed = mstime() - start;
+        if (elapsed >= timeout) {
             errno = ETIMEDOUT;
             return -1;
         }
+        remaining = timeout - elapsed;
     }
-    return ret;
 }
 
-int syncRead(int fd, char *ptr, ssize_t size, int timeout) {
+/* Read the specified amount of bytes from 'fd'. If all the bytes are read within
+ * 'timeout' milliseconds the operation succeed and 'size' is returned.
+ * Otherwise the operation fails, -1 is returned, and an unspecified amount of
+ * data could be read from the file descriptor. */
+ssize_t syncRead(int fd, char *ptr, ssize_t size, long long timeout) {
     ssize_t nread, totread = 0;
-    time_t start = time(NULL);
+    long long start = mstime();
+    long long remaining = timeout;
 
-    timeout++;
-    while(size) {
-        if (aeWait(fd,AE_READABLE,1000) & AE_READABLE) {
+    while(1) {
+        long long wait = (remaining > REDIS_SYNCIO_RESOLUTION) ?
+                          remaining : REDIS_SYNCIO_RESOLUTION;
+        long long elapsed;
+
+        if (aeWait(fd,AE_READABLE,wait) & AE_READABLE) {
             nread = read(fd,ptr,size);
             if (nread <= 0) return -1;
             ptr += nread;
             size -= nread;
             totread += nread;
+            if (size == 0) return totread;
         }
-        if ((time(NULL)-start) > timeout) {
+        elapsed = mstime() - start;
+        if (elapsed >= timeout) {
             errno = ETIMEDOUT;
             return -1;
         }
+        remaining = timeout - elapsed;
     }
-    return totread;
 }
 
-int syncReadLine(int fd, char *ptr, ssize_t size, int timeout) {
+/* Read a line making sure that every char will not require more than 'timeout'
+ * milliseconds to be read.
+ * 
+ * On success the number of bytes read is returned, otherwise -1.
+ * On success the string is always correctly terminated with a 0 byte. */
+ssize_t syncReadLine(int fd, char *ptr, ssize_t size, long long timeout) {
     ssize_t nread = 0;
 
     size--;
-- 
2.47.2