Add #version to lesskey.

NEWS

@@ -20,6 +20,8 @@
 
 * Add the --redraw-on-quit option.
 
+* Add #version conditional to lesskey.
+
 * Fix display of multibyte and double-width chars in prompt.
 
 * Fix ESC-BACKSPACE command when BACKSPACE key does not send 0x08.

lesskey.c

@@ -122,6 +122,14 @@ lesskey_parse_error(s)
  fprintf(stderr, "%s\n", s);
 }
 
+ int
+lstrtoi(buf, ebuf)
+ char *buf;
+ char **ebuf;
+{
+ return (int) strtol(buf, ebuf, 10);
+}
+
  void *
 ecalloc(count, size)
  int count;

lesskey.nro.VER

@@ -26,7 +26,7 @@ source file into a format understood by
 .IR less .
 This compilation step is no longer required and the
 .I lesskey
-program is therefore deprecated although the file format remains supported by
+program is therefore deprecated, although the file format remains supported by
 .I less
 itself.
 .PP
@@ -43,7 +43,7 @@ Defines new line-editing keys.
 Defines environment variables.
 .PP
 Blank lines and lines which start with a pound sign (#) are ignored,
-except for the special section header lines.
+except as noted below.
 .
 .SH "COMMAND SECTION"
 The command section begins with the line
@@ -355,6 +355,40 @@ is run, and specifies the character set to be "latin1":
 .fi
 .sp
 .
+.SH CONDITIONAL CONFIGURATION
+If a line begins with #version followed by a relational operator and a version number,
+the remainder of the line is parsed if and only if the running version of
+.I less
+(or
+.IR lesskey )
+matches the operator.
+This can be helpful if a lesskey file is used by different versions of
+.IR less .
+For example, suppose that a new command named 'sideways-search' is added in version 777.
+Then the following line would assign the command to the Q key, but only in versions of
+.I less
+which support it. The line would be ignored in earlier versions.
+.sp
+.nf
+ #version >= 777 Q sideways-search
+.fi
+.sp
+These six operators are supported:
+.RS 5m
+.TS
+l l.
+ > Greater than
+ < Less than
+ >= Greater than or equal to
+ <= Less than or equal to
+ = Equal to
+ <> Not equal to
+.TE
+.RE
+.sp
+In version 594 and earlier, all #version lines are ignored,
+regardless of the result of the relational operator.
+.
 .SH "SEE ALSO"
 .BR less (1)
 .

lesskey_parse.c

@@ -21,9 +21,12 @@
 extern void lesskey_parse_error(char *msg);
 extern char *homefile(char *filename);
 extern void *ecalloc(int count, unsigned int size);
+extern int lstrtoi(char *str, char **end);
+extern char version[];
 
 static int linenum;
 static int errors;
+static int less_version = 0;
 static char *lesskey_file;
 
 static struct lesskey_cmdname cmdnames[] = 
@@ -353,9 +356,75 @@ add_cmd_str(s, tables)
 }
 
 /*
- * See if we have a special "control" line.
+ * Does a given version number match the running version?
+ * Operator compares the running version to the given version.
  */
  static int
+match_version(op, ver)
+ char op;
+ int ver;
+{
+ switch (op)
+ {
+ case '>': return less_version > ver;
+ case '<': return less_version < ver;
+ case '+': return less_version >= ver;
+ case '-': return less_version <= ver;
+ case '=': return less_version == ver;
+ case '!': return less_version != ver;
+ default: {
+ char sop[2] = { op, '\0' };
+ parse_error("invalid operator in #version: ", sop);
+ return 0; }
+ }
+}
+
+/*
+ * Handle a #version line.
+ * If the version matches, return the part of the line that should be executed.
+ * Otherwise, return NULL.
+ */
+ static char *
+version_line(s, tables)
+ char *s;
+ struct lesskey_tables *tables;
+{
+ char op;
+ int ver;
+ char *e;
+
+ s += strlen("#version");
+ s = skipsp(s);
+ op = *s++;
+ if (op == '<' && *s == '=')
+ {
+ op = '-';
+ s++;
+ } else if (op == '>' && *s == '=')
+ {
+ op = '+';
+ s++;
+ } else if (op == '<' && *s == '>')
+ {
+ op = '!';
+ s++;
+ }
+ s = skipsp(s);
+ ver = lstrtoi(s, &e);
+ if (e == s)
+ {
+ parse_error("invalid version number in #version: ", s);
+ return (NULL);
+ }
+ if (!match_version(op, ver))
+ return (NULL);
+ return (e);
+}
+
+/*
+ * See if we have a special "control" line.
+ */
+ static char *
 control_line(s, tables)
  char *s;
  struct lesskey_tables *tables;
@@ -365,25 +434,29 @@ control_line(s, tables)
  if (PREFIX(s, "#line-edit"))
  {
  tables->currtable = &tables->edittable;
- return (1);
+ return (NULL);
  }
  if (PREFIX(s, "#command"))
  {
  tables->currtable = &tables->cmdtable;
- return (1);
+ return (NULL);
  }
  if (PREFIX(s, "#env"))
  {
  tables->currtable = &tables->vartable;
- return (1);
+ return (NULL);
  }
  if (PREFIX(s, "#stop"))
  {
  add_cmd_char('\0', tables);
  add_cmd_char(A_END_LIST, tables);
- return (1);
+ return (NULL);
+ }
+ if (PREFIX(s, "#version"))
+ {
+ return (version_line(s, tables));
  }
- return (0);
+ return (s);
 }
 
 /*
@@ -528,14 +601,15 @@ parse_line(line, tables)
  /*
  * See if it is a control line.
  */
- if (control_line(line, tables))
+ p = control_line(line, tables);
+ if (p == NULL)
  return;
  /*
  * Skip leading white space.
  * Replace the final newline with a null byte.
  * Ignore blank lines and comments.
  */
- p = clean_line(line);
+ p = clean_line(p);
  if (*p == '\0')
  return;
 
@@ -563,6 +637,8 @@ parse_lesskey(infile, tables)
  init_tables(tables);
  errors = 0;
  linenum = 0;
+ if (less_version == 0)
+ less_version = lstrtoi(version, NULL);
 
  /*
  * Open the input file.

version.c

@@ -935,7 +935,8 @@ v591 8/8/21 Use \kB for backspace key in lesskey; add more \k codes;
  handle multibyte chars in prompt.
 v592 8/24/21 Add --status-line option; limit use of /proc kludge; add --header.
 v593 8/30/21 Add header columns, --no-number-headers.
-v594 Let regex library handle caseless; add --redraw-on-quit option.
+v594 Let regex library handle caseless; add --redraw-on-quit option;
+ add #version to lesskey.
 */
 
 char version[] = "594x";