_AWK AS A C CODE GENERATOR_
by Wahhab Baldwin

[LISTING ONE]

#    This program reads a C structure and produces C code
#    to write the record to a C-ISAM work area.
#    There are limitations on the input format:  see sample

BEGIN {     FS = "[ \t[]+"              # Override default
      }                                 #    field separators
$1 == "struct" && $3 == "{" {           # Opening record struct
            rec = $2
            print "/*  " $2 "  */"
            offset = 0
       }
$2 == "struct" && $3 == "{" {           # Struct within record
            type = "struct"
            j = 0
       }
$2 == "long"   {    f(type == "struct", "stlong",  $3, 4)}
$2 == "int"    {    f(type == "struct", "stint",   $3, 2)}
$2 == "float"  {    f(type == "struct", "stfloat", $3, 4)}
$2 == "double" {    f(type == "struct", "stdbl",   $3, 8)}
$2 == "char" && NF > 3 {                # String
                    f(type == "struct", "stchar",  $3, $4 - 1)}
$2 == "char" && NF == 3 {               # Single character
                    f(type == "struct", "stchar",  $3, 1)}
$2 == "}" && NF > 3 {                   # Array of structs
            type = ""
            print "\tfor (i = 0; i < " $4 + 0 "; i++) {"
            for (k = 0; k < j; k++) {
                gsub(";", "", name[k])
                temp = $3 "[i]." name[k]
                emit2("\t" stype[k], temp, flen[k])
            }
            print "\t}"
            offset += ($4 - 1) * slen
            slen = 0
        }

$2 == "}" && NF == 3 {                  # Named struct
            type = ""
            for (k = 0; k < j; k++)
                emit(stype[k], $3 "." name[k], flen[k])
            slen = 0
        }

function f(bool, str, x, y) {
           if (bool)
                setup(str, x, y)
            else
                emit(str, x, y)
        }

function setup(type, varname, l) {      # Save field data in array
            name[j] = varname
            stype[j] = type
            flen[j++] = l
            slen += l
        }

function emit(type, varname, l) {       # Print C code for field
            gsub(";", "", varname)
            print "\t" type "(p." rec "->" varname,
                ", inf_rec + " offset \
                (type == "ststring" ? ", " l ");" : ");")
            offset += l
        }

function emit2(type, varname, l) {      # Print C code for field in struct
            gsub(";", "", varname)
            print "\t" type "(p." rec "->" varname,
                ", inf_rec + i * " slen, "+",
                offset (type ~ /string/ ? ", " l ");": ");")
            offset += l
        }

[Example 1: Simple AWK program to total a series of numbers]

{total += $1}
END  {print total}  # Total for all input


[Example 2:  Built-in AWK function for global substitution]

	{gsub(/aluminium/, "aluminum")}
	{gsub(/colour/, "color")}

[Example 3:  Using strings rather than integers as array subscripts]


           # Program to count word usage in input.
           # eliminate all non-letters except space
           {    gsub(/[^A-Za-z ]/, "")        }

           # add words to associative array
           {    for (i = 1; i <= NF; i++)
                     ++word[$i] }

           # print each array entry
      END  {    for (j in word)
                     print j, word[j] }

[Example 4:  Alternative to using the ? operator]

      if (type ~ /string/)
           last_part = ", " l ");"
      else
           last_part = ");"
      print "\t" type "(p." rec "->" varname
           ", inf_rec + " offset last_part