API: Implement buffer updates

Originally written by @phodge in
https://github.com/neovim/neovim/pull/5269.

1 files changed, 195 insertions, 0 deletions

diff --git a/src/nvim/liveupdate.c b/src/nvim/liveupdate.c
new file mode 100644
index 0000000000..79318e4255
--- /dev/null
+++ b/src/nvim/liveupdate.c
@@ -0,0 +1,195 @@
+#include "nvim/liveupdate.h"
+#include "nvim/memline.h"
+#include "nvim/api/private/helpers.h"
+#include "nvim/msgpack_rpc/channel.h"
+
+// Register a channel. Return True if the channel was added, or already added.
+// Return False if the channel couldn't be added because the buffer is
+// unloaded.
+bool liveupdate_register(buf_T *buf, uint64_t channel_id)
+{
+  // must fail if the buffer isn't loaded
+  if (buf->b_ml.ml_mfp == NULL) {
+    return false;
+  }
+
+  // count how many channels are currently watching the buffer
+  size_t size = kv_size(buf->liveupdate_channels);
+  if (size) {
+    for (size_t i = 0; i < size; i++) {
+      if (kv_A(buf->liveupdate_channels, i) == channel_id) {
+        // buffer is already registered ... nothing to do
+        return true;
+      }
+    }
+  }
+
+  // append the channelid to the list
+  kv_push(buf->liveupdate_channels, channel_id);
+
+  // send through the full channel contents now
+  Array linedata = ARRAY_DICT_INIT;
+  size_t line_count = buf->b_ml.ml_line_count;
+  linedata.size = line_count;
+  linedata.items = xcalloc(sizeof(Object), line_count);
+  for (size_t i = 0; i < line_count; i++) {
+    linenr_T lnum = 1 + (linenr_T)i;
+
+    const char *bufstr = (char *)ml_get_buf(buf, lnum, false);
+    Object str = STRING_OBJ(cstr_to_string(bufstr));
+
+    // Vim represents NULs as NLs, but this may confuse clients.
+    strchrsub(str.data.string.data, '\n', '\0');
+
+    linedata.items[i] = str;
+  }
+
+  Array args = ARRAY_DICT_INIT;
+  args.size = 4;
+  args.items = xcalloc(sizeof(Object), args.size);
+
+  // the first argument is always the buffer handle
+  args.items[0] = BUFFER_OBJ(buf->handle);
+  args.items[1] = INTEGER_OBJ(buf->b_changedtick);
+  args.items[2] = ARRAY_OBJ(linedata);
+  args.items[3] = BOOLEAN_OBJ(false);
+
+  channel_send_event(channel_id, "LiveUpdateStart", args);
+  return true;
+}
+
+void liveupdate_send_end(buf_T *buf, uint64_t channelid)
+{
+    Array args = ARRAY_DICT_INIT;
+    args.size = 1;
+    args.items = xcalloc(sizeof(Object), args.size);
+    args.items[0] = BUFFER_OBJ(buf->handle);
+    channel_send_event(channelid, "LiveUpdateEnd", args);
+}
+
+void liveupdate_unregister(buf_T *buf, uint64_t channelid)
+{
+  size_t size = kv_size(buf->liveupdate_channels);
+  if (!size) {
+    return;
+  }
+
+  // go through list backwards and remove the channel id each time it appears
+  // (it should never appear more than once)
+  size_t j = 0;
+  size_t found = 0;
+  for (size_t i = 0; i < size; i++) {
+    if (kv_A(buf->liveupdate_channels, i) == channelid) {
+      found++;
+    } else {
+      // copy item backwards into prior slot if needed
+      if (i != j) {
+        kv_A(buf->liveupdate_channels, j) = kv_A(buf->liveupdate_channels, i);
+      }
+      j++;
+    }
+  }
+
+  if (found) {
+    // remove X items from the end of the array
+    buf->liveupdate_channels.size -= found;
+
+    // make a new copy of the active array without the channelid in it
+    liveupdate_send_end(buf, channelid);
+  }
+}
+
+void liveupdate_unregister_all(buf_T *buf)
+{
+  size_t size = kv_size(buf->liveupdate_channels);
+  if (size) {
+    for (size_t i = 0; i < size; i++) {
+      liveupdate_send_end(buf, kv_A(buf->liveupdate_channels, i));
+    }
+    kv_destroy(buf->liveupdate_channels);
+    kv_init(buf->liveupdate_channels);
+  }
+}
+
+void liveupdate_send_changes(buf_T *buf, linenr_T firstline, int64_t num_added,
+                             int64_t num_removed, bool send_tick)
+{
+  // if one the channels doesn't work, put its ID here so we can remove it later
+  uint64_t badchannelid = 0;
+
+  // notify each of the active channels
+  for (size_t i = 0; i < kv_size(buf->liveupdate_channels); i++) {
+    uint64_t channelid = kv_A(buf->liveupdate_channels, i);
+
+    // send through the changes now channel contents now
+    Array args = ARRAY_DICT_INIT;
+    args.size = 5;
+    args.items = xcalloc(sizeof(Object), args.size);
+
+    // the first argument is always the buffer handle
+    args.items[0] = BUFFER_OBJ(buf->handle);
+
+    // next argument is b:changedtick
+    args.items[1] = send_tick ? INTEGER_OBJ(buf->b_changedtick) : NIL;
+
+    // the first line that changed (zero-indexed)
+    args.items[2] = INTEGER_OBJ(firstline - 1);
+
+    // how many lines are being swapped out
+    args.items[3] = INTEGER_OBJ(num_removed);
+
+    // linedata of lines being swapped in
+    Array linedata = ARRAY_DICT_INIT;
+    if (num_added > 0) {
+        linedata.size = num_added;
+        linedata.items = xcalloc(sizeof(Object), num_added);
+        for (int64_t i = 0; i < num_added; i++) {
+          int64_t lnum = firstline + i;
+          const char *bufstr = (char *)ml_get_buf(buf, (linenr_T)lnum, false);
+          Object str = STRING_OBJ(cstr_to_string(bufstr));
+
+          // Vim represents NULs as NLs, but this may confuse clients.
+          strchrsub(str.data.string.data, '\n', '\0');
+
+          linedata.items[i] = str;
+        }
+    }
+    args.items[4] = ARRAY_OBJ(linedata);
+    if (!channel_send_event(channelid, "LiveUpdate", args)) {
+      // We can't unregister the channel while we're iterating over the
+      // liveupdate_channels array, so we remember its ID to unregister it at
+      // the end.
+      badchannelid = channelid;
+    }
+  }
+
+  // We can only ever remove one dead channel at a time. This is OK because the
+  // change notifications are so frequent that many dead channels will be
+  // cleared up quickly.
+  if (badchannelid != 0) {
+    ELOG("Disabling live updates for dead channel %llu", badchannelid);
+    liveupdate_unregister(buf, badchannelid);
+  }
+}
+
+void liveupdate_send_tick(buf_T *buf)
+{
+  // notify each of the active channels
+  for (size_t i = 0; i < kv_size(buf->liveupdate_channels); i++) {
+    uint64_t channelid = kv_A(buf->liveupdate_channels, i);
+
+    // send through the changes now channel contents now
+    Array args = ARRAY_DICT_INIT;
+    args.size = 2;
+    args.items = xcalloc(sizeof(Object), args.size);
+
+    // the first argument is always the buffer handle
+    args.items[0] = BUFFER_OBJ(buf->handle);
+
+    // next argument is b:changedtick
+    args.items[1] = INTEGER_OBJ(buf->b_changedtick);
+
+    // don't try and clean up dead channels here
+    channel_send_event(channelid, "LiveUpdateTick", args);
+  }
+}