text: #ifndef STREAM_H
  #define STREAM_H
  
  #include "rax.h"
  #include "listpack.h"
  
  /* Stream item ID: a 128 bit number composed of a milliseconds time and
   * a sequence counter. IDs generated in the same millisecond (or in a past
   * millisecond if the clock jumped backward) will use the millisecond time
   * of the latest generated ID and an incremented sequence. */
  typedef struct streamID {
      uint64_t ms;        /* Unix time in milliseconds. */
      uint64_t seq;       /* Sequence number. */
  } streamID;
  
  typedef struct stream {
      rax *rax;               /* The radix tree holding the stream. */
      uint64_t length;        /* Number of elements inside this stream. */
      streamID last_id;       /* Zero if there are yet no items. */
      rax *cgroups;           /* Consumer groups dictionary: name -> streamCG */
  } stream;
  
  /* We define an iterator to iterate stream items in an abstract way, without
   * caring about the radix tree + listpack representation. Technically speaking
   * the iterator is only used inside streamReplyWithRange(), so could just
   * be implemented inside the function, but practically there is the AOF
   * rewriting code that also needs to iterate the stream to emit the XADD
   * commands. */
  typedef struct streamIterator {
      stream *stream;         /* The stream we are iterating. */
      streamID master_id;     /* ID of the master entry at listpack head. */
      uint64_t master_fields_count;       /* Master entries # of fields. */
      unsigned char *master_fields_start; /* Master entries start in listpack. */
      unsigned char *master_fields_ptr;   /* Master field to emit next. */
      int entry_flags;                    /* Flags of entry we are emitting. */
      int rev;                /* True if iterating end to start (reverse). */
      uint64_t start_key[2];  /* Start key as 128 bit big endian. */
      uint64_t end_key[2];    /* End key as 128 bit big endian. */
      raxIterator ri;         /* Rax iterator. */
      unsigned char *lp;      /* Current listpack. */
      unsigned char *lp_ele;  /* Current listpack cursor. */
      unsigned char *lp_flags; /* Current entry flags pointer. */
      /* Buffers used to hold the string of lpGet() when the element is
       * integer encoded, so that there is no string representation of the
       * element inside the listpack itself. */
      unsigned char field_buf[LP_INTBUF_SIZE];
      unsigned char value_buf[LP_INTBUF_SIZE];
  } streamIterator;
  
  /* Consumer group. */
  typedef struct streamCG {
      streamID last_id;       /* Last delivered (not acknowledged) ID for this
                                 group. Consumers that will just ask for more
                                 messages will served with IDs > than this. */
      rax *pel;               /* Pending entries list. This is a radix tree that
                                 has every message delivered to consumers (without
                                 the NOACK option) that was yet not acknowledged
                                 as processed. The key of the radix tree is the
                                 ID as a 64 bit big endian number, while the
                                 associated value is a streamNACK structure.*/
      rax *consumers;         /* A radix tree representing the consumers by name
                                 and their associated representation in the form
                                 of streamConsumer structures. */
  } streamCG;
  
  /* A specific consumer in a consumer group.  */
  typedef struct streamConsumer {
      mstime_t seen_time;         /* Last time this consumer was active. */
      sds name;                   /* Consumer name. This is how the consumer
                                     will be identified in the consumer group
                                     protocol. Case sensitive. */
      rax *pel;                   /* Consumer specific pending entries list: all
                                     the pending messages delivered to this
                                     consumer not yet acknowledged. Keys are
                                     big endian message IDs, while values are
                                     the same streamNACK structure referenced
                                     in the "pel" of the consumer group structure
                                     itself, so the value is shared. */
  } streamConsumer;
  
  /* Pending (yet not acknowledged) message in a consumer group. */
  typedef struct streamNACK {
      mstime_t delivery_time;     /* Last time this message was delivered. */
      uint64_t delivery_count;    /* Number of times this message was delivered.*/
      streamConsumer *consumer;   /* The consumer this message was delivered to
                                     in the last delivery. */
  } streamNACK;
  
  /* Stream propagation information, passed to functions in order to propagate
   * XCLAIM commands to AOF and slaves. */
  typedef struct streamPropInfo {
      robj *keyname;
      robj *groupname;
  } streamPropInfo;
  
  /* Prototypes of exported APIs. */
  struct client;
  
  /* Flags for streamLookupConsumer */
  #define SLC_DEFAULT      0
  #define SLC_NO_REFRESH   (1<<0) /* Do not update consumer's seen-time */
  
  /* Flags for streamCreateConsumer */
  #define SCC_DEFAULT       0
  #define SCC_NO_NOTIFY     (1<<0) /* Do not notify key space if consumer created */
  #define SCC_NO_DIRTIFY    (1<<1) /* Do not dirty++ if consumer created */
  
  stream *streamNew(void);
  void freeStream(stream *s);
  unsigned long streamLength(const robj *subject);
  size_t streamReplyWithRange(client *c, stream *s, streamID *start, streamID *end, size_t count, int rev, streamCG *group, streamConsumer *consumer, int flags, streamPropInfo *spi);
  void streamIteratorStart(streamIterator *si, stream *s, streamID *start, streamID *end, int rev);
  int streamIteratorGetID(streamIterator *si, streamID *id, int64_t *numfields);
  void streamIteratorGetField(streamIterator *si, unsigned char **fieldptr, unsigned char **valueptr, int64_t *fieldlen, int64_t *valuelen);
  void streamIteratorRemoveEntry(streamIterator *si, streamID *current);
  void streamIteratorStop(streamIterator *si);
  streamCG *streamLookupCG(stream *s, sds groupname);
  streamConsumer *streamLookupConsumer(streamCG *cg, sds name, int flags);
  streamConsumer *streamCreateConsumer(streamCG *cg, sds name, robj *key, int dbid, int flags);
  streamCG *streamCreateCG(stream *s, char *name, size_t namelen, streamID *id);
  streamNACK *streamCreateNACK(streamConsumer *consumer);
  void streamDecodeID(void *buf, streamID *id);
  int streamCompareID(streamID *a, streamID *b);
  void streamFreeNACK(streamNACK *na);
  int streamIncrID(streamID *id);
  int streamDecrID(streamID *id);
  void streamPropagateConsumerCreation(client *c, robj *key, robj *groupname, sds consumername);
  robj *streamDup(robj *o);
  int streamValidateListpackIntegrity(unsigned char *lp, size_t size, int deep);
  int streamParseID(const robj *o, streamID *id);
  robj *createObjectFromStreamID(streamID *id);
  int streamAppendItem(stream *s, robj **argv, int64_t numfields, streamID *added_id, streamID *use_id);
  int streamDeleteItem(stream *s, streamID *id);
  int64_t streamTrimByLength(stream *s, long long maxlen, int approx);
  int64_t streamTrimByID(stream *s, streamID minid, int approx);
  
  #endif
  