Allow users to replace allocator and handle OOM everywhere. (#800)

* Adds an indirection to every allocation/deallocation to allow users to 
  plug in ones of their choosing (use custom functions, jemalloc, etc).

* Gracefully handle OOM everywhere in hiredis.  This should make it possible
  for users of the library to have more flexibility in how they handle such situations.

* Changes `redisReaderTask->elements` from an `int` to a `long long` to prevent
  a possible overflow when transferring the task elements into a `redisReply`.

* Adds a configurable `max elements` member to `redisReader` that defaults to
  2^32 - 1.  This can be set to "unlimited" by setting the value to zero.

1 files changed, 7 insertions, 2 deletions

diff --git a/read.h b/read.h
index 788c401..2d74d77 100644
--- a/read.h
+++ b/read.h
@@ -63,7 +63,11 @@
 #define REDIS_REPLY_BIGNUM 13
 #define REDIS_REPLY_VERB 14
 
-#define REDIS_READER_MAX_BUF (1024*16)  /* Default max unused reader buffer. */
+/* Default max unused reader buffer. */
+#define REDIS_READER_MAX_BUF (1024*16)
+
+/* Default multi-bulk element limit */
+#define REDIS_READER_MAX_ARRAY_ELEMENTS ((1LL<<32) - 1)
 
 #ifdef __cplusplus
 extern "C" {
@@ -71,7 +75,7 @@ extern "C" {
 
 typedef struct redisReadTask {
     int type;
-    int elements; /* number of elements in multibulk container */
+    long long elements; /* number of elements in multibulk container */
     int idx; /* index in parent (array) object */
     void *obj; /* holds user-generated value for a read task */
     struct redisReadTask *parent; /* parent task */
@@ -96,6 +100,7 @@ typedef struct redisReader {
     size_t pos; /* Buffer cursor */
     size_t len; /* Buffer length */
     size_t maxbuf; /* Max length of unused buffer */
+    long long maxelements; /* Max multi-bulk elements */
 
     redisReadTask **task;
     int tasks;