#!/bin/awk -f
#
# Copyright © 2021, 2023-2024 Nick Bowler
#
# Generate a function to return the C keyword corresponding to a specifier
# type as a string, for internal use by the output routines.
#
# License WTFPL2: Do What The Fuck You Want To Public License, version 2.
# This is free software: you are free to do what the fuck you want to.
# There is NO WARRANTY, to the extent permitted by law.

END {
  print "/*";
  if (FILENAME) {
    print " * Automatically generated by gen-specstr.awk from " FILENAME;
  } else {
    print " * Automatically generated by gen-specstr.awk";
  }
  print " * Do not edit.";
  print " */";
}

BEGIN {
  kinds["TYPE"] = kinds["STOR"] = kinds["QUAL"] = kinds["FUNC"] = 1;
  count = 0;
}

# Locate all the relevant identifiers in cdecl.h.  We assume everything
# is in numerically increasing order within the various enums.
$1 ~ /^CDECL_/ {
  sub(/[^ABCDEFGHIJKLMNOPQRSTUVWXYZ_].*/, "", $1);

  split($1, parts, "_");
  if (parts[2] == "SPEC") {
    x = $0;
    sub(/^.*= */, "", x);
    sub(/,? *$/, "", x);

    x = int(x / 512) % 8;
    if (skiptab[x]) {
      print "cannot create skip table";
      exit 1;
    }

    skiptab[x] = parts[3];
  }

  if (parts[2] in kinds) {
    kind_counts[parts[2]]++;
    specs[count++] = parts[3];
  }
}

END {
  # Create the token table.  The first 5 entries key off of bits 9 through 11,
  # which is sufficient to distinguish the different specifier kinds and is
  # used to partition the rest of the token table.
  skip_count = 0;
  for (i in skiptab) {
    if (skip_count < i)
      skip_count = i;
  }

  skip_pos = ++skip_count;
  for (i = 0; i < skip_count; i++) {
    offset_table = offset_table skip_pos ", ";
    skip_pos += kind_counts[skiptab[i]];
  }
  sub(/ $/, "\n\t\t", offset_table);

  for (i = 0; i < count; i++) {
    suffix = "";
    if (i+1 < count)
      suffix = ",\n\t\t";

    if (specs[i] == "IDENT")
      s = "0";
    else
      s = "PACK_TOKEN(T_" specs[i] ")";
    offset_table = offset_table s suffix;
  }

  print "static const char *spec_string(unsigned type)"
  print "{"
  print "\tstatic const unsigned char _Alignas(1) idx[] = {";
  print "\t\t" offset_table;
  print "\t};\n";

  print "\tunsigned x = (type & 0xff) + idx[type >> 9];";
  print "\tassert(x < sizeof idx);";
  print "\tif (!(x = idx[x]))";
  print "\t\treturn \"\";";
  print "\treturn cdecl__token_name(UNPACK_TOKEN(x));";
  print "}";
}