api: simplify nvim_buf_get_offset function

src/nvim/api/buffer.c

@@ -493,11 +493,10 @@ end:
 
 /// Return the byte offset for a line.
 //
-/// This includes the end-of-line character, depending on the 'fileformat'
-/// option for the current buffer. The first line returns 0. UTF-8 encoding is
-/// used, 'fileencoding' is ignored. Sending in the index just below the last
-/// line gives the total byte count for the entire file. A final newline is
-/// included if it would be written, see 'eol'.
+/// The first line returns 0. UTF-8 bytes are counted, and EOL counts as one
+/// byte. 'fileformat' and 'fileencoding' are ignored. Sending in the index
+/// just below the last line gives the total byte count for the entire buffer.
+/// A final EOL is included if it would be written, see 'eol'.
 ///
 /// Unlike |line2byte()|, throws error for out-of-bounds indexing.
 /// Returns -1 for unloaded buffer.
@@ -506,7 +505,7 @@ end:
 /// @param index      Line index
 /// @param[out] err   Error details, if any
 /// @return Integer   Byte offset
-Integer nvim_buf_get_offset_for_line(Buffer buffer, Integer index, Error *err)
+Integer nvim_buf_get_offset(Buffer buffer, Integer index, Error *err)
   FUNC_API_SINCE(5)
 {
   buf_T *buf = find_buffer_by_handle(buffer, err);
@@ -524,7 +523,7 @@ Integer nvim_buf_get_offset_for_line(Buffer buffer, Integer index, Error *err)
     return 0;
   }
 
-  return ml_find_line_or_offset(buf, (int)index+1, NULL);
+  return ml_find_line_or_offset(buf, (int)index+1, NULL, true);
 }
 
 /// Gets a buffer-scoped (b:) variable.

src/nvim/buffer.c

@@ -3734,7 +3734,8 @@ int build_stl_str_hl(
       FALLTHROUGH;
     case STL_OFFSET:
     {
-      long l = ml_find_line_or_offset(wp->w_buffer, wp->w_cursor.lnum, NULL);
+      long l = ml_find_line_or_offset(wp->w_buffer, wp->w_cursor.lnum, NULL,
+                                      false);
       num = (wp->w_buffer->b_ml.ml_flags & ML_EMPTY) || l < 0 ?
             0L : l + 1 + (!(State & INSERT) && empty_line ?
                           0 : (int)wp->w_cursor.col);

src/nvim/eval.c

@@ -7232,7 +7232,7 @@ static void f_byte2line(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     rettv->vval.v_number = -1;
   } else {
     rettv->vval.v_number = (varnumber_T)ml_find_line_or_offset(curbuf, 0,
-                                                               &boff);
+                                                               &boff, false);
   }
 }
 
@@ -12084,7 +12084,7 @@ static void f_line2byte(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   if (lnum < 1 || lnum > curbuf->b_ml.ml_line_count + 1) {
     rettv->vval.v_number = -1;
   } else {
-    rettv->vval.v_number = ml_find_line_or_offset(curbuf, lnum, NULL);
+    rettv->vval.v_number = ml_find_line_or_offset(curbuf, lnum, NULL, false);
   }
   if (rettv->vval.v_number >= 0) {
     rettv->vval.v_number++;

src/nvim/memline.c

@@ -3850,13 +3850,17 @@ static void ml_updatechunk(buf_T *buf, linenr_T line, long len, int updtype)
   ml_upd_lastcurix = curix;
 }
 
-/*
- * Find offset for line or line with offset.
- * Find line with offset if "lnum" is 0; return remaining offset in offp
- * Find offset of line if "lnum" > 0
- * return -1 if information is not available
- */
-long ml_find_line_or_offset(buf_T *buf, linenr_T lnum, long *offp)
+/// Find offset for line or line with offset.
+///
+/// @param buf buffer to use
+/// @param lnum if > 0, find offset of lnum, store offset in offp
+///             if == 0, return line with offset *offp
+/// @param offp Location where offset of line is stored, or to read offset to
+///             use to find line. In the later case, store remaining offset.
+/// @param no_ff ignore 'fileformat' option, always use one byte for NL.
+///
+/// @return -1 if information is not available
+long ml_find_line_or_offset(buf_T *buf, linenr_T lnum, long *offp, bool no_ff)
 {
   linenr_T curline;
   int curix;
@@ -3869,7 +3873,7 @@ long ml_find_line_or_offset(buf_T *buf, linenr_T lnum, long *offp)
   int text_end;
   long offset;
   int len;
-  int ffdos = (get_fileformat(buf) == EOL_DOS);
+  int ffdos = !no_ff && (get_fileformat(buf) == EOL_DOS);
   int extra = 0;
 
   /* take care of cached line first */
@@ -3983,7 +3987,7 @@ void goto_byte(long cnt)
   if (boff) {
     boff--;
   }
-  lnum = ml_find_line_or_offset(curbuf, (linenr_T)0, &boff);
+  lnum = ml_find_line_or_offset(curbuf, (linenr_T)0, &boff, false);
   if (lnum < 1) {         // past the end
     curwin->w_cursor.lnum = curbuf->b_ml.ml_line_count;
     curwin->w_curswant = MAXCOL;