1 files changed, 268 insertions, 16 deletions

diff --git a/src/nvim/api/buffer.c b/src/nvim/api/buffer.c
index f1151d196a..8d82d22040 100644
--- a/src/nvim/api/buffer.c
+++ b/src/nvim/api/buffer.c
@@ -309,6 +309,27 @@ end:
   return rv;
 }
 
+static bool check_string_array(Array arr, bool disallow_nl, Error *err)
+{
+  for (size_t i = 0; i < arr.size; i++) {
+    if (arr.items[i].type != kObjectTypeString) {
+      api_set_error(err,
+                    kErrorTypeValidation,
+                    "All items in the replacement array must be strings");
+      return false;
+    }
+    // Disallow newlines in the middle of the line.
+    if (disallow_nl) {
+      const String l = arr.items[i].data.string;
+      if (memchr(l.data, NL, l.size)) {
+        api_set_error(err, kErrorTypeValidation,
+                      "String cannot contain newlines");
+        return false;
+      }
+    }
+  }
+  return true;
+}
 
 /// Sets (replaces) a line-range in the buffer.
 ///
@@ -362,22 +383,9 @@ void nvim_buf_set_lines(uint64_t channel_id,
     return;
   }
 
-  for (size_t i = 0; i < replacement.size; i++) {
-    if (replacement.items[i].type != kObjectTypeString) {
-      api_set_error(err,
-                    kErrorTypeValidation,
-                    "All items in the replacement array must be strings");
-      return;
-    }
-    // Disallow newlines in the middle of the line.
-    if (channel_id != VIML_INTERNAL_CALL) {
-      const String l = replacement.items[i].data.string;
-      if (memchr(l.data, NL, l.size)) {
-        api_set_error(err, kErrorTypeValidation,
-                      "String cannot contain newlines");
-        return;
-      }
-    }
+  bool disallow_nl = (channel_id != VIML_INTERNAL_CALL);
+  if (!check_string_array(replacement, disallow_nl, err)) {
+    return;
   }
 
   size_t new_len = replacement.size;
@@ -487,6 +495,250 @@ end:
   try_end(err);
 }
 
+/// Sets (replaces) a range in the buffer
+///
+/// This is recommended over nvim_buf_set_lines when only modifying parts of a
+/// line, as extmarks will be preserved on non-modified parts of the touched
+/// lines.
+///
+/// Indexing is zero-based and end-exclusive.
+///
+/// To insert text at a given index, set `start` and `end` ranges to the same
+/// index. To delete a range, set `replacement` to an array containing
+/// an empty string, or simply an empty array.
+///
+/// Prefer nvim_buf_set_lines when adding or deleting entire lines only.
+///
+/// @param channel_id
+/// @param buffer           Buffer handle, or 0 for current buffer
+/// @param start_row        First line index
+/// @param start_column     Last column
+/// @param end_row          Last line index
+/// @param end_column       Last column
+/// @param replacement      Array of lines to use as replacement
+/// @param[out] err         Error details, if any
+void nvim_buf_set_text(uint64_t channel_id, Buffer buffer,
+                       Integer start_row, Integer start_col,
+                       Integer end_row, Integer end_col,
+                       ArrayOf(String) replacement, Error *err)
+  FUNC_API_SINCE(7)
+{
+  FIXED_TEMP_ARRAY(scratch, 1);
+  if (replacement.size == 0) {
+    scratch.items[0] = STRING_OBJ(STATIC_CSTR_AS_STRING(""));
+    replacement = scratch;
+  }
+
+  buf_T *buf = find_buffer_by_handle(buffer, err);
+  if (!buf) {
+    return;
+  }
+
+  bool oob = false;
+
+  // check range is ordered and everything!
+  // start_row, end_row within buffer len (except add text past the end?)
+  start_row = normalize_index(buf, start_row, &oob);
+  if (oob || start_row == buf->b_ml.ml_line_count + 1) {
+    api_set_error(err, kErrorTypeValidation, "start_row out of bounds");
+    return;
+  }
+
+  end_row = normalize_index(buf, end_row, &oob);
+  if (oob || end_row == buf->b_ml.ml_line_count + 1) {
+    api_set_error(err, kErrorTypeValidation, "end_row out of bounds");
+    return;
+  }
+
+  char *str_at_start = (char *)ml_get_buf(buf, start_row, false);
+  if (start_col < 0 || (size_t)start_col > strlen(str_at_start)) {
+    api_set_error(err, kErrorTypeValidation, "start_col out of bounds");
+    return;
+  }
+
+  char *str_at_end = (char *)ml_get_buf(buf, end_row, false);
+  size_t len_at_end = strlen(str_at_end);
+  if (end_col < 0 || (size_t)end_col > len_at_end) {
+    api_set_error(err, kErrorTypeValidation, "end_col out of bounds");
+    return;
+  }
+
+  if (start_row > end_row || (end_row == start_row && start_col > end_col)) {
+    api_set_error(err, kErrorTypeValidation, "start is higher than end");
+    return;
+  }
+
+  bool disallow_nl = (channel_id != VIML_INTERNAL_CALL);
+  if (!check_string_array(replacement, disallow_nl, err)) {
+    return;
+  }
+
+  size_t new_len = replacement.size;
+
+  bcount_t new_byte = 0;
+  bcount_t old_byte = 0;
+
+  // calculate byte size of old region before it gets modified/deleted
+  if (start_row == end_row) {
+      old_byte = (bcount_t)end_col - start_col;
+  } else {
+      const char *bufline;
+      old_byte += (bcount_t)strlen(str_at_start) - start_col;
+      for (int64_t i = 1; i < end_row - start_row; i++) {
+          int64_t lnum = start_row + i;
+
+          bufline = (char *)ml_get_buf(buf, lnum, false);
+          old_byte += (bcount_t)(strlen(bufline))+1;
+      }
+      old_byte += (bcount_t)end_col+1;
+  }
+
+  String first_item = replacement.items[0].data.string;
+  String last_item = replacement.items[replacement.size-1].data.string;
+
+  size_t firstlen = (size_t)start_col+first_item.size;
+  size_t last_part_len = strlen(str_at_end) - (size_t)end_col;
+  if (replacement.size == 1) {
+    firstlen += last_part_len;
+  }
+  char *first = xmallocz(firstlen), *last = NULL;
+  memcpy(first, str_at_start, (size_t)start_col);
+  memcpy(first+start_col, first_item.data, first_item.size);
+  memchrsub(first+start_col, NUL, NL, first_item.size);
+  if (replacement.size == 1) {
+    memcpy(first+start_col+first_item.size, str_at_end+end_col, last_part_len);
+  } else {
+    last = xmallocz(last_item.size+last_part_len);
+    memcpy(last, last_item.data, last_item.size);
+    memchrsub(last, NUL, NL, last_item.size);
+    memcpy(last+last_item.size, str_at_end+end_col, last_part_len);
+  }
+
+  char **lines = (new_len != 0) ? xcalloc(new_len, sizeof(char *)) : NULL;
+  lines[0] = first;
+  new_byte += (bcount_t)(first_item.size);
+  for (size_t i = 1; i < new_len-1; i++) {
+    const String l = replacement.items[i].data.string;
+
+    // Fill lines[i] with l's contents. Convert NULs to newlines as required by
+    // NL-used-for-NUL.
+    lines[i] = xmemdupz(l.data, l.size);
+    memchrsub(lines[i], NUL, NL, l.size);
+    new_byte += (bcount_t)(l.size)+1;
+  }
+  if (replacement.size > 1) {
+    lines[replacement.size-1] = last;
+    new_byte += (bcount_t)(last_item.size)+1;
+  }
+
+  try_start();
+  aco_save_T aco;
+  aucmd_prepbuf(&aco, (buf_T *)buf);
+
+  if (!MODIFIABLE(buf)) {
+    api_set_error(err, kErrorTypeException, "Buffer is not 'modifiable'");
+    goto end;
+  }
+
+  // Small note about undo states: unlike set_lines, we want to save the
+  // undo state of one past the end_row, since end_row is inclusive.
+  if (u_save((linenr_T)start_row - 1, (linenr_T)end_row + 1) == FAIL) {
+    api_set_error(err, kErrorTypeException, "Failed to save undo information");
+    goto end;
+  }
+
+  ptrdiff_t extra = 0;  // lines added to text, can be negative
+  size_t old_len = (size_t)(end_row-start_row+1);
+
+  // If the size of the range is reducing (ie, new_len < old_len) we
+  // need to delete some old_len. We do this at the start, by
+  // repeatedly deleting line "start".
+  size_t to_delete = (new_len < old_len) ? (size_t)(old_len - new_len) : 0;
+  for (size_t i = 0; i < to_delete; i++) {
+    if (ml_delete((linenr_T)start_row, false) == FAIL) {
+      api_set_error(err, kErrorTypeException, "Failed to delete line");
+      goto end;
+    }
+  }
+
+  if (to_delete > 0) {
+    extra -= (ptrdiff_t)to_delete;
+  }
+
+  // For as long as possible, replace the existing old_len with the
+  // new old_len. This is a more efficient operation, as it requires
+  // less memory allocation and freeing.
+  size_t to_replace = old_len < new_len ? old_len : new_len;
+  for (size_t i = 0; i < to_replace; i++) {
+    int64_t lnum = start_row + (int64_t)i;
+
+    if (lnum >= MAXLNUM) {
+      api_set_error(err, kErrorTypeValidation, "Index value is too high");
+      goto end;
+    }
+
+    if (ml_replace((linenr_T)lnum, (char_u *)lines[i], false) == FAIL) {
+      api_set_error(err, kErrorTypeException, "Failed to replace line");
+      goto end;
+    }
+    // Mark lines that haven't been passed to the buffer as they need
+    // to be freed later
+    lines[i] = NULL;
+  }
+
+  // Now we may need to insert the remaining new old_len
+  for (size_t i = to_replace; i < new_len; i++) {
+    int64_t lnum = start_row + (int64_t)i - 1;
+
+    if (lnum >= MAXLNUM) {
+      api_set_error(err, kErrorTypeValidation, "Index value is too high");
+      goto end;
+    }
+
+    if (ml_append((linenr_T)lnum, (char_u *)lines[i], 0, false) == FAIL) {
+      api_set_error(err, kErrorTypeException, "Failed to insert line");
+      goto end;
+    }
+
+    // Same as with replacing, but we also need to free lines
+    xfree(lines[i]);
+    lines[i] = NULL;
+    extra++;
+  }
+
+  // Adjust marks. Invalidate any which lie in the
+  // changed range, and move any in the remainder of the buffer.
+  mark_adjust((linenr_T)start_row,
+              (linenr_T)end_row,
+              MAXLNUM,
+              (long)extra,
+              kExtmarkNOOP);
+
+  colnr_T col_extent = (colnr_T)(end_col
+                                 - ((end_row == start_row) ? start_col : 0));
+  extmark_splice(buf, (int)start_row-1, (colnr_T)start_col,
+                 (int)(end_row-start_row), col_extent, old_byte,
+                 (int)new_len-1, (colnr_T)last_item.size, new_byte,
+                 kExtmarkUndo);
+
+
+  changed_lines((linenr_T)start_row, 0, (linenr_T)end_row, (long)extra, true);
+
+  // adjust cursor like an extmark ( i e it was inside last_part_len)
+  if (curwin->w_cursor.lnum == end_row && curwin->w_cursor.col > end_col) {
+    curwin->w_cursor.col -= col_extent - (colnr_T)last_item.size;
+  }
+  fix_cursor((linenr_T)start_row, (linenr_T)end_row, (linenr_T)extra);
+
+end:
+  for (size_t i = 0; i < new_len; i++) {
+    xfree(lines[i]);
+  }
+  xfree(lines);
+  aucmd_restbuf(&aco);
+  try_end(err);
+}
+
 /// Returns the byte offset of a line (0-indexed). |api-indexing|
 ///
 /// Line 1 (index=0) has offset 0. UTF-8 bytes are counted. EOL is one byte.