Merge pull request #456 from pietern/unstable-mkopts

[redis.git] / src / rio.c

diff --git a/src/rio.c b/src/rio.c
index e69d939f2e9a980a498e48d76f956809ed94ccef..44165d71565fa68009e2cd0a23b63c63076be2df 100644 (file)
--- a/src/rio.c
+++ b/src/rio.c
@@ -1,18 +1,36 @@
+/* rio.c is a simple stream-oriented I/O abstraction that provides an interface
+ * to write code that can consume/produce data using different concrete input
+ * and output devices. For instance the same rdb.c code using the rio abstraction
+ * can be used to read and write the RDB format using in-memory buffers or files.
+ *
+ * A rio object provides the following methods:
+ *  read: read from stream.
+ *  write: write to stream.
+ *  tell: get the current offset.
+ *
+ * It is also possible to set a 'checksum' method that is used by rio.c in order
+ * to compute a checksum of the data written or read, or to query the rio object
+ * for the current checksum. */
+
+#include "fmacros.h"
 #include <string.h>
+#include <stdio.h>
 #include "rio.h"
 #include "util.h"
 
+uint64_t crc64(uint64_t crc, const unsigned char *s, uint64_t l);
+
 /* Returns 1 or 0 for success/failure. */
 static size_t rioBufferWrite(rio *r, const void *buf, size_t len) {
     r->io.buffer.ptr = sdscatlen(r->io.buffer.ptr,(char*)buf,len);
     r->io.buffer.pos += len;
-    return len;
+    return 1;
 }
 
 /* Returns 1 or 0 for success/failure. */
 static size_t rioBufferRead(rio *r, void *buf, size_t len) {
     if (sdslen(r->io.buffer.ptr)-r->io.buffer.pos < len)
-        return 0;
+        return 0; /* not enough buffer to return len bytes. */
     memcpy(buf,r->io.buffer.ptr+r->io.buffer.pos,len);
     r->io.buffer.pos += len;
     return 1;
@@ -42,6 +60,8 @@ static const rio rioBufferIO = {
     rioBufferRead,
     rioBufferWrite,
     rioBufferTell,
+    NULL,           /* update_checksum */
+    0,              /* current checksum */
     { { NULL, 0 } } /* union for io-specific vars */
 };
 
@@ -49,21 +69,32 @@ static const rio rioFileIO = {
     rioFileRead,
     rioFileWrite,
     rioFileTell,
+    NULL,           /* update_checksum */
+    0,              /* current checksum */
     { { NULL, 0 } } /* union for io-specific vars */
 };
 
-rio rioInitWithFile(FILE *fp) {
-    rio r = rioFileIO;
-    r.io.file.fp = fp;
-    return r;
+void rioInitWithFile(rio *r, FILE *fp) {
+    *r = rioFileIO;
+    r->io.file.fp = fp;
+}
+
+void rioInitWithBuffer(rio *r, sds s) {
+    *r = rioBufferIO;
+    r->io.buffer.ptr = s;
+    r->io.buffer.pos = 0;
 }
-rio rioInitWithBuffer(sds s) {
-    rio r = rioBufferIO;
-    r.io.buffer.ptr = s;
-    r.io.buffer.pos = 0;
-    return r;
+
+/* This function can be installed both in memory and file streams when checksum
+ * computation is needed. */
+void rioGenericUpdateChecksum(rio *r, const void *buf, size_t len) {
+    r->cksum = crc64(r->cksum,buf,len);
 }
 
+/* ------------------------------ Higher level interface ---------------------------
+ * The following higher level functions use lower level rio.c functions to help
+ * generating the Redis protocol for the Append Only File. */
+
 /* Write multi bulk count in the format: "*<count>\r\n". */
 size_t rioWriteBulkCount(rio *r, char prefix, int count) {
     char cbuf[128];